Merge branch 'master' into custom-discarded-job-handling

1020 files changed, 15161 insertions, 6684 deletions

diff --git a/.codeclimate.yml b/.codeclimate.yml
index 63d3562e9b..d59a0780d1 100644
--- a/.codeclimate.yml
+++ b/.codeclimate.yml
@@ -1,7 +1,29 @@
+checks:
+  argument-count:
+    enabled: false
+  complex-logic:
+    enabled: false
+  file-lines:
+    enabled: false
+  method-complexity:
+    enabled: false
+  method-count:
+    enabled: false
+  method-lines:
+    enabled: false
+  nested-control-flow:
+    enabled: false
+  return-statements:
+    enabled: false
+  similar-code:
+    enabled: false
+  identical-code:
+    enabled: false
+
 engines:
   rubocop:
     enabled: true
-    channel: rubocop-0-49
+    channel: rubocop-0-51
 
 ratings:
   paths:
diff --git a/.rubocop.yml b/.rubocop.yml
index f3ed8bc841..f6259fe432 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -76,6 +76,9 @@ Layout/SpaceAroundOperators:
 Layout/SpaceBeforeFirstArg:
     Enabled: true
 
+Style/DefWithParentheses:
+  Enabled: true
+
 # Defining a method with parameters needs parentheses.
 Style/MethodDefParentheses:
   Enabled: true
@@ -135,3 +138,11 @@ Lint/EndAlignment:
 # Use my_method(my_arg) not my_method( my_arg ) or my_method my_arg.
 Lint/RequireParentheses:
   Enabled: true
+
+Style/RedundantReturn:
+  Enabled: true
+  AllowMultipleReturnValues: true
+
+Style/Semicolon:
+  Enabled: true
+  AllowAsExpressionSeparator: true
diff --git a/.travis.yml b/.travis.yml
index 27400b98c7..ac151b902d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,29 +11,34 @@ cache:
 
 services:
   - memcached
+  - redis-server
 
 addons:
   postgresql: "9.6"
+  chrome: stable
+  apt:
+    sources:
+      - sourceline: "ppa:mc3man/trusty-media"
+      - sourceline: "ppa:ubuntuhandbook1/apps"
 
 bundler_args: --without test --jobs 3 --retry 3
 before_install:
   - "rm ${BUNDLE_GEMFILE}.lock"
   - "travis_retry gem update --system"
-  - "travis_retry gem update bundler"
+  - "travis_retry gem install bundler -v 1.15.4"
   - "[ -f /tmp/beanstalkd-1.10/Makefile ] || (curl -L https://github.com/kr/beanstalkd/archive/v1.10.tar.gz | tar xz -C /tmp)"
   - "pushd /tmp/beanstalkd-1.10 && make && (./beanstalkd &); popd"
   - "[[ -z $encrypted_8a915ebdd931_key && -z $encrypted_8a915ebdd931_iv ]] || openssl aes-256-cbc -K $encrypted_8a915ebdd931_key -iv $encrypted_8a915ebdd931_iv -in activestorage/test/service/configurations.yml.enc -out activestorage/test/service/configurations.yml -d"
   - "[[ $GEM != 'av:ujs' ]] || nvm install node"
   - "[[ $GEM != 'av:ujs' ]] || node --version"
   - "[[ $GEM != 'av:ujs' ]] || (cd actionview && npm install)"
-  - "[[ $GEM != 'av:ujs' ]] || [[ $(phantomjs --version) > '2' ]] || npm install -g phantomjs-prebuilt"
 
 before_script:
   # Set Sauce Labs username and access key. Obfuscated, purposefully not encrypted.
   # Decodes to e.g. `export VARIABLE=VALUE`
   - $(base64 --decode <<< "ZXhwb3J0IFNBVUNFX0FDQ0VTU19LRVk9YTAzNTM0M2YtZTkyMi00MGIzLWFhM2MtMDZiM2VhNjM1YzQ4")
   - $(base64 --decode <<< "ZXhwb3J0IFNBVUNFX1VTRVJOQU1FPXJ1YnlvbnJhaWxz")
-  - redis-server --bind 127.0.0.1 --port 6379 --requirepass 'password' --daemonize yes
+  - if [[ $GEM = *ast*  ]] ; then sudo apt-get update && sudo apt-get -y install ffmpeg mupdf mupdf-tools ; fi
 
 script: 'ci/travis.rb'
 
@@ -65,21 +70,25 @@ matrix:
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
     - rvm: 2.3.5
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
     - rvm: 2.4.2
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
     - rvm: ruby-head
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
     - rvm: 2.3.5
       env:
@@ -94,17 +103,17 @@ matrix:
         - "GEM=ar:postgresql POSTGRES=9.2"
       addons:
         postgresql: "9.2"
-    - rvm: jruby-9.1.13.0
+    - rvm: jruby-9.1.15.0
       jdk: oraclejdk8
       env:
         - "GEM=ap"
-    - rvm: jruby-9.1.13.0
+    - rvm: jruby-9.1.15.0
       jdk: oraclejdk8
       env:
         - "GEM=am,amo,aj"
   allow_failures:
     - rvm: ruby-head
-    - rvm: jruby-9.1.13.0
+    - rvm: jruby-9.1.15.0
     - env: "GEM=ac:integration"
   fast_finish: true
 
diff --git a/Gemfile b/Gemfile
index fda547fab2..32ec87b501 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,21 +6,18 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
 gemspec
 
-gem "arel", github: "rails/arel"
-
 # We need a newish Rake since Active Job sets its test tasks' descriptions.
 gem "rake", ">= 11.1"
 
 # This needs to be with require false to ensure correct loading order, as it has to
 # be loaded after loading the test library.
-gem "mocha", "~> 0.14", require: false
+gem "mocha", require: false
 
-gem "capybara", "~> 2.13"
+gem "capybara", "~> 2.15"
 
 gem "rack-cache", "~> 1.2"
-gem "jquery-rails"
 gem "coffee-rails"
-gem "sass-rails", github: "rails/sass-rails", branch: "5-0-stable"
+gem "sass-rails"
 gem "turbolinks", "~> 5"
 
 # require: false so bcrypt is loaded only when has_secure_password is used.
@@ -40,6 +37,9 @@ gem "rubocop", ">= 0.47", require: false
 # https://github.com/guard/rb-inotify/pull/79
 gem "rb-inotify", github: "matthewd/rb-inotify", branch: "close-handling", require: false
 
+# https://github.com/puma/puma/pull/1345
+gem "stopgap_13632", platforms: :mri if RUBY_VERSION == "2.2.8"
+
 group :doc do
   gem "sdoc", github: "robin850/sdoc", branch: "upgrade"
   gem "redcarpet", "~> 3.2.3", platforms: :ruby
@@ -52,16 +52,13 @@ gem "dalli", ">= 2.2.1"
 gem "listen", ">= 3.0.5", "< 3.2", require: false
 gem "libxml-ruby", platforms: :ruby
 
-# Action View. For testing Erubis handler deprecation.
-gem "erubis", "~> 2.7.0", require: false
-
 # for railties app_generator_test
 gem "bootsnap", ">= 1.1.0", require: false
 
 # Active Job.
 group :job do
   gem "resque", require: false
-  gem "resque-scheduler", require: false
+  gem "resque-scheduler", github: "resque/resque-scheduler", require: false
   gem "sidekiq", require: false
   gem "sucker_punch", require: false
   gem "delayed_job", require: false
@@ -80,9 +77,10 @@ end
 group :cable do
   gem "puma", require: false
 
-  gem "em-hiredis", require: false
   gem "hiredis", require: false
-  gem "redis", require: false
+  gem "redis", "~> 4.0", require: false
+
+  gem "redis-namespace"
 
   gem "websocket-client-simple", github: "matthewd/websocket-client-simple", branch: "close-race", require: false
 
@@ -91,14 +89,20 @@ group :cable do
   gem "sprockets-export", require: false
 end
 
+# Active Storage
 group :storage do
   gem "aws-sdk-s3", require: false
-  gem "google-cloud-storage", "~> 1.3", require: false
+  gem "google-cloud-storage", "~> 1.8", require: false
   gem "azure-storage", require: false
 
   gem "mini_magick"
 end
 
+group :ujs do
+  gem "qunit-selenium"
+  gem "chromedriver-helper"
+end
+
 # Add your own local bundler stuff.
 local_gemfile = File.expand_path(".Gemfile", __dir__)
 instance_eval File.read local_gemfile if File.exist? local_gemfile
diff --git a/Gemfile.lock b/Gemfile.lock
index 787631ada5..1453bddb34 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -24,22 +24,14 @@ GIT
       websocket
 
 GIT
-  remote: https://github.com/rails/arel.git
-  revision: 42510bf71472e2e35d9becb546edd05562672344
+  remote: https://github.com/resque/resque-scheduler.git
+  revision: 284b862dd63967da1cf3a7e6abd9d2052067c8be
   specs:
-    arel (9.0.0.alpha)
-
-GIT
-  remote: https://github.com/rails/sass-rails.git
-  revision: bb5c1d34e8acad2e2960cc785184ffe17d7b3bca
-  branch: 5-0-stable
-  specs:
-    sass-rails (5.0.6)
-      railties (>= 4.0.0, < 6)
-      sass (~> 3.1)
-      sprockets (>= 2.8, < 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
-      tilt (>= 1.1, < 3)
+    resque-scheduler (4.3.0)
+      mono_logger (~> 1.0)
+      redis (>= 3.3, < 5)
+      resque (~> 1.26)
+      rufus-scheduler (~> 3.2)
 
 GIT
   remote: https://github.com/robin850/sdoc.git
@@ -52,62 +44,62 @@ GIT
 PATH
   remote: .
   specs:
-    actioncable (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
+    actioncable (5.2.0.beta2)
+      actionpack (= 5.2.0.beta2)
       nio4r (~> 2.0)
       websocket-driver (~> 0.6.1)
-    actionmailer (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      actionview (= 5.2.0.alpha)
-      activejob (= 5.2.0.alpha)
+    actionmailer (5.2.0.beta2)
+      actionpack (= 5.2.0.beta2)
+      actionview (= 5.2.0.beta2)
+      activejob (= 5.2.0.beta2)
       mail (~> 2.5, >= 2.5.4)
       rails-dom-testing (~> 2.0)
-    actionpack (5.2.0.alpha)
-      actionview (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    actionpack (5.2.0.beta2)
+      actionview (= 5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
       rack (~> 2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actionview (5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    actionview (5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activejob (5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    activejob (5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
       globalid (>= 0.3.6)
-    activemodel (5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
-    activerecord (5.2.0.alpha)
-      activemodel (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
-      arel (= 9.0.0.alpha)
-    activestorage (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      activerecord (= 5.2.0.alpha)
-    activesupport (5.2.0.alpha)
+    activemodel (5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
+    activerecord (5.2.0.beta2)
+      activemodel (= 5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
+      arel (>= 9.0)
+    activestorage (5.2.0.beta2)
+      actionpack (= 5.2.0.beta2)
+      activerecord (= 5.2.0.beta2)
+    activesupport (5.2.0.beta2)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (~> 0.7)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    rails (5.2.0.alpha)
-      actioncable (= 5.2.0.alpha)
-      actionmailer (= 5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      actionview (= 5.2.0.alpha)
-      activejob (= 5.2.0.alpha)
-      activemodel (= 5.2.0.alpha)
-      activerecord (= 5.2.0.alpha)
-      activestorage (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    rails (5.2.0.beta2)
+      actioncable (= 5.2.0.beta2)
+      actionmailer (= 5.2.0.beta2)
+      actionpack (= 5.2.0.beta2)
+      actionview (= 5.2.0.beta2)
+      activejob (= 5.2.0.beta2)
+      activemodel (= 5.2.0.beta2)
+      activerecord (= 5.2.0.beta2)
+      activestorage (= 5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
       bundler (>= 1.3.0)
-      railties (= 5.2.0.alpha)
+      railties (= 5.2.0.beta2)
       sprockets-rails (>= 2.0.0)
-    railties (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    railties (5.2.0.beta2)
+      actionpack (= 5.2.0.beta2)
+      activesupport (= 5.2.0.beta2)
       method_source
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
@@ -115,9 +107,23 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.5.1)
-      public_suffix (~> 2.0, >= 2.0.2)
+    activerecord-jdbc-adapter (1.3.24)
+      activerecord (>= 2.2, < 5.0)
+    activerecord-jdbcmysql-adapter (1.3.24)
+      activerecord-jdbc-adapter (~> 1.3.24)
+      jdbc-mysql (>= 5.1.22)
+    activerecord-jdbcpostgresql-adapter (1.3.24)
+      activerecord-jdbc-adapter (~> 1.3.24)
+      jdbc-postgres (~> 9.1, <= 9.4.1206)
+    activerecord-jdbcsqlite3-adapter (1.3.24)
+      activerecord-jdbc-adapter (~> 1.3.24)
+      jdbc-sqlite3 (>= 3.7.2, < 3.9)
+    addressable (2.5.2)
+      public_suffix (>= 2.0.2, < 4.0)
     amq-protocol (2.2.0)
+    archive-zip (0.7.0)
+      io-like (~> 0.3.0)
+    arel (9.0.0)
     ast (2.3.0)
     aws-partitions (1.20.0)
     aws-sdk-core (3.3.0)
@@ -145,6 +151,7 @@ GEM
       concurrent-ruby (~> 1.0.1)
       dante (> 0.1.5)
     bcrypt (3.1.11)
+    bcrypt (3.1.11-java)
     bcrypt (3.1.11-x64-mingw32)
     bcrypt (3.1.11-x86-mingw32)
     beaneater (1.0.0)
@@ -168,6 +175,8 @@ GEM
       selenium-webdriver
     bootsnap (1.1.2)
       msgpack (~> 1.0)
+    bootsnap (1.1.2-java)
+      msgpack (~> 1.0)
     builder (3.2.3)
     bunny (2.6.6)
       amq-protocol (>= 2.1.0)
@@ -181,6 +190,9 @@ GEM
       xpath (~> 2.0)
     childprocess (0.7.1)
       ffi (~> 1.0, >= 1.0.11)
+    chromedriver-helper (1.1.0)
+      archive-zip (~> 0.7.0)
+      nokogiri (~> 1.6)
     coffee-rails (4.2.2)
       coffee-script (>= 2.2.0)
       railties (>= 4.0.0)
@@ -189,13 +201,15 @@ GEM
       execjs
     coffee-script-source (1.12.2)
     concurrent-ruby (1.0.5)
+    concurrent-ruby (1.0.5-java)
     connection_pool (2.2.1)
     cookiejar (0.3.3)
+    crass (1.0.3)
     curses (1.0.2)
     daemons (1.2.4)
     dalli (2.7.6)
     dante (0.2.0)
-    declarative (0.0.9)
+    declarative (0.0.10)
     declarative-option (0.1.0)
     delayed_job (4.1.3)
       activesupport (>= 3.0, < 5.2)
@@ -203,9 +217,6 @@ GEM
       activerecord (>= 3.0, < 5.2)
       delayed_job (>= 3.0, < 5)
     digest-crc (0.4.1)
-    em-hiredis (0.3.1)
-      eventmachine (~> 1.0)
-      hiredis (~> 0.6.0)
     em-http-request (1.1.5)
       addressable (>= 2.3.4)
       cookiejar (!= 0.3.1)
@@ -214,14 +225,11 @@ GEM
       http_parser.rb (>= 0.6.0)
     em-socksify (0.3.1)
       eventmachine (>= 1.0.0.beta.4)
-    erubi (1.6.1)
-    erubis (2.7.0)
-    et-orbi (1.0.5)
+    erubi (1.7.0)
+    et-orbi (1.0.8)
       tzinfo
     event_emitter (0.2.6)
     eventmachine (1.2.5)
-    eventmachine (1.2.5-x64-mingw32)
-    eventmachine (1.2.5-x86-mingw32)
     execjs (2.7.0)
     faraday (0.13.1)
       multipart-post (>= 1.2, < 3)
@@ -239,45 +247,49 @@ GEM
       eventmachine (>= 0.12.0)
       websocket-driver (>= 0.5.1)
     ffi (1.9.18)
+    ffi (1.9.18-java)
     ffi (1.9.18-x64-mingw32)
     ffi (1.9.18-x86-mingw32)
-    globalid (0.4.0)
+    globalid (0.4.1)
       activesupport (>= 4.2.0)
-    google-api-client (0.13.1)
+    google-api-client (0.17.3)
       addressable (~> 2.5, >= 2.5.1)
-      googleauth (~> 0.5)
+      googleauth (>= 0.5, < 0.7.0)
       httpclient (>= 2.8.1, < 3.0)
       mime-types (~> 3.0)
       representable (~> 3.0)
       retriable (>= 2.0, < 4.0)
-    google-cloud-core (1.0.0)
+    google-cloud-core (1.1.0)
       google-cloud-env (~> 1.0)
-      googleauth (~> 0.5.1)
     google-cloud-env (1.0.1)
       faraday (~> 0.11)
-    google-cloud-storage (1.4.0)
+    google-cloud-storage (1.9.0)
       digest-crc (~> 0.4)
-      google-api-client (~> 0.13.0)
-      google-cloud-core (~> 1.0)
-    googleauth (0.5.3)
+      google-api-client (~> 0.17.0)
+      google-cloud-core (~> 1.1)
+      googleauth (~> 0.6.2)
+    googleauth (0.6.2)
       faraday (~> 0.12)
-      jwt (~> 1.4)
+      jwt (>= 1.4, < 3.0)
       logging (~> 2.0)
       memoist (~> 0.12)
       multi_json (~> 1.11)
       os (~> 0.9)
       signet (~> 0.7)
     hiredis (0.6.1)
+    hiredis (0.6.1-java)
     http_parser.rb (0.6.0)
     httpclient (2.8.3)
-    i18n (0.8.6)
+    i18n (0.9.1)
+      concurrent-ruby (~> 1.0)
+    io-like (0.3.0)
+    jdbc-mysql (5.1.44)
+    jdbc-postgres (9.4.1206)
+    jdbc-sqlite3 (3.8.11.2)
     jmespath (1.3.1)
-    jquery-rails (4.3.1)
-      rails-dom-testing (>= 1, < 3)
-      railties (>= 4.2.0)
-      thor (>= 0.14, < 2.0)
     json (2.1.0)
-    jwt (1.5.6)
+    json (2.1.0-java)
+    jwt (2.1.0)
     kindlerb (1.2.0)
       mustache
       nokogiri
@@ -290,13 +302,14 @@ GEM
     logging (2.2.2)
       little-plugger (~> 1.1)
       multi_json (~> 1.10)
-    loofah (2.0.3)
+    loofah (2.1.1)
+      crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
-    mail (2.6.6)
-      mime-types (>= 1.16, < 4)
+    mail (2.7.0)
+      mini_mime (>= 0.1.1)
     memoist (0.16.0)
     metaclass (0.0.4)
-    method_source (0.8.2)
+    method_source (0.9.0)
     mime-types (3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
@@ -309,13 +322,14 @@ GEM
       path_expander (~> 1.0)
     minitest-server (1.0.4)
       minitest (~> 5.0)
-    mocha (0.14.0)
+    mocha (1.3.0)
       metaclass (~> 0.0.1)
     mono_logger (1.1.0)
     msgpack (1.1.0)
+    msgpack (1.1.0-java)
     msgpack (1.1.0-x64-mingw32)
     msgpack (1.1.0-x86-mingw32)
-    multi_json (1.12.1)
+    multi_json (1.12.2)
     multipart-post (2.0.0)
     mustache (1.0.5)
     mustermann (1.0.0)
@@ -325,6 +339,7 @@ GEM
     nio4r (2.1.0)
     nokogiri (1.8.0)
       mini_portile2 (~> 2.2.0)
+    nokogiri (1.8.0-java)
     nokogiri (1.8.0-x64-mingw32)
       mini_portile2 (~> 2.2.0)
     nokogiri (1.8.0-x86-mingw32)
@@ -339,16 +354,20 @@ GEM
     pg (0.19.0-x86-mingw32)
     powerpack (0.1.1)
     psych (2.2.4)
-    public_suffix (2.0.5)
+    public_suffix (3.0.1)
     puma (3.9.1)
+    puma (3.9.1-java)
     que (0.14.0)
+    qunit-selenium (0.0.4)
+      selenium-webdriver
+      thor
     racc (1.4.14)
     rack (2.0.3)
     rack-cache (1.7.0)
       rack (>= 0.4)
     rack-protection (2.0.0)
       rack
-    rack-test (0.7.0)
+    rack-test (0.8.0)
       rack (>= 1.0, < 3)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
@@ -357,13 +376,13 @@ GEM
       loofah (~> 2.0)
     rainbow (2.2.2)
       rake
-    rake (12.0.0)
+    rake (12.2.1)
     rb-fsevent (0.10.2)
     rdoc (5.1.0)
     redcarpet (3.2.3)
-    redis (3.3.3)
-    redis-namespace (1.5.3)
-      redis (~> 3.0, >= 3.0.4)
+    redis (4.0.1)
+    redis-namespace (1.6.0)
+      redis (>= 3.0.4)
     representable (3.0.4)
       declarative (< 0.1.0)
       declarative-option (< 0.2.0)
@@ -374,45 +393,46 @@ GEM
       redis-namespace (~> 1.3)
       sinatra (>= 0.9.2)
       vegas (~> 0.1.2)
-    resque-scheduler (4.3.0)
-      mono_logger (~> 1.0)
-      redis (~> 3.3)
-      resque (~> 1.26)
-      rufus-scheduler (~> 3.2)
     retriable (3.1.1)
-    rubocop (0.49.1)
+    rubocop (0.51.0)
       parallel (~> 1.10)
       parser (>= 2.3.3.1, < 3.0)
       powerpack (~> 0.1)
-      rainbow (>= 1.99.1, < 3.0)
+      rainbow (>= 2.2.2, < 3.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
-    ruby-progressbar (1.8.1)
+    ruby-progressbar (1.9.0)
     ruby_dep (1.5.0)
     rubyzip (1.2.1)
     rufus-scheduler (3.4.2)
       et-orbi (~> 1.0)
-    sass (3.5.1)
+    sass (3.5.3)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
+    sass-rails (5.0.7)
+      railties (>= 4.0.0, < 6)
+      sass (~> 3.1)
+      sprockets (>= 2.8, < 4.0)
+      sprockets-rails (>= 2.0, < 4.0)
+      tilt (>= 1.1, < 3)
     selenium-webdriver (3.5.1)
       childprocess (~> 0.5)
       rubyzip (~> 1.0)
     sequel (4.49.0)
     serverengine (1.5.11)
       sigdump (~> 0.2.2)
-    sidekiq (5.0.4)
+    sidekiq (5.0.5)
       concurrent-ruby (~> 1.0)
       connection_pool (~> 2.2, >= 2.2.0)
       rack-protection (>= 1.5.0)
-      redis (~> 3.3, >= 3.3.3)
+      redis (>= 3.3.4, < 5)
     sigdump (0.2.4)
-    signet (0.7.3)
+    signet (0.8.1)
       addressable (~> 2.3)
       faraday (~> 0.9)
-      jwt (~> 1.5)
+      jwt (>= 1.5, < 3.0)
       multi_json (~> 1.10)
     sinatra (2.0.0)
       mustermann (~> 1.0)
@@ -445,6 +465,7 @@ GEM
     thor (0.20.0)
     thread (0.1.7)
     thread_safe (0.3.6)
+    thread_safe (0.3.6-java)
     tilt (2.0.8)
     turbolinks (5.0.1)
       turbolinks-source (~> 5)
@@ -472,6 +493,7 @@ GEM
       nokogiri (~> 1.3)
 
 PLATFORMS
+  java
   ruby
   x64-mingw32
   x86-mingw32
@@ -480,7 +502,6 @@ DEPENDENCIES
   activerecord-jdbcmysql-adapter (>= 1.3.0)
   activerecord-jdbcpostgresql-adapter (>= 1.3.0)
   activerecord-jdbcsqlite3-adapter (>= 1.3.0)
-  arel!
   aws-sdk-s3
   azure-storage
   backburner
@@ -490,23 +511,21 @@ DEPENDENCIES
   blade-sauce_labs_plugin
   bootsnap (>= 1.1.0)
   byebug
-  capybara (~> 2.13)
+  capybara (~> 2.15)
+  chromedriver-helper
   coffee-rails
   dalli (>= 2.2.1)
   delayed_job
   delayed_job_active_record
-  em-hiredis
-  erubis (~> 2.7.0)
-  google-cloud-storage (~> 1.3)
+  google-cloud-storage (~> 1.8)
   hiredis
-  jquery-rails
   json (>= 2.0.0)
   kindlerb (~> 1.2.0)
   libxml-ruby
   listen (>= 3.0.5, < 3.2)
   mini_magick
   minitest-bisect
-  mocha (~> 0.14)
+  mocha
   mysql2 (>= 0.4.4)
   nokogiri (>= 1.6.8)
   pg (>= 0.18.0)
@@ -514,17 +533,19 @@ DEPENDENCIES
   puma
   que
   queue_classic!
+  qunit-selenium
   racc (>= 1.4.6)
   rack-cache (~> 1.2)
   rails!
   rake (>= 11.1)
   rb-inotify!
   redcarpet (~> 3.2.3)
-  redis
+  redis (~> 4.0)
+  redis-namespace
   resque
-  resque-scheduler
+  resque-scheduler!
   rubocop (>= 0.47)
-  sass-rails!
+  sass-rails
   sdoc!
   sequel
   sidekiq
@@ -541,4 +562,4 @@ DEPENDENCIES
   websocket-client-simple!
 
 BUNDLED WITH
-   1.15.4
+   1.16.0
diff --git a/RAILS_VERSION b/RAILS_VERSION
index d5ebf861d3..5d41efd0ef 100644
--- a/RAILS_VERSION
+++ b/RAILS_VERSION
@@ -1 +1 @@
-5.2.0.alpha
+5.2.0.beta2
diff --git a/RELEASING_RAILS.md b/RELEASING_RAILS.md
index 3ff28c29f5..c61fe7eb13 100644
--- a/RELEASING_RAILS.md
+++ b/RELEASING_RAILS.md
@@ -141,7 +141,7 @@ lists where you should announce:
 Use Markdown format for your announcement. Remember to ask people to report
 issues with the release candidate to the rails-core mailing list.
 
-NOTE: For patch releases there's a `rake announce` task to generate the release
+NOTE: For patch releases, there's a `rake announce` task to generate the release
 post. It supports multiple patch releases too:
 
 ```
diff --git a/actioncable/CHANGELOG.md b/actioncable/CHANGELOG.md
index 560ee89846..38bf842b14 100644
--- a/actioncable/CHANGELOG.md
+++ b/actioncable/CHANGELOG.md
@@ -1,3 +1,18 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Removed deprecated evented redis adapter.
+
+    *Rafael Mendonça França*
+
+*   Support redis-rb 4.0.
+
+    *Jeremy Daer*
+
 *   Hash long stream identifiers when using PostgreSQL adapter.
 
     PostgreSQL has a limit on identifiers length (63 chars, [docs](https://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS)).
@@ -16,11 +31,4 @@
 
     *Marc Rendl Ignacio*
 
-*   Action Cable socket errors are now logged to the console
-
-    Previously any socket errors were ignored and this made it hard to diagnose socket issues (e.g. as discussed in #28362).
-
-    *Edward Poot*
-
-
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actioncable/CHANGELOG.md) for previous changes.
diff --git a/actioncable/README.md b/actioncable/README.md
index a060e8938e..a05ef1dd20 100644
--- a/actioncable/README.md
+++ b/actioncable/README.md
@@ -446,7 +446,7 @@ The WebSocket server doesn't have access to the session, but it has access to th
 
 ## Dependencies
 
-Action Cable provides a subscription adapter interface to process its pubsub internals. By default, asynchronous, inline, PostgreSQL, evented Redis, and non-evented Redis adapters are included. The default adapter in new Rails applications is the asynchronous (`async`) adapter. To create your own adapter, you can look at `ActionCable::SubscriptionAdapter::Base` for all methods that must be implemented, and any of the adapters included within Action Cable as example implementations.
+Action Cable provides a subscription adapter interface to process its pubsub internals. By default, asynchronous, inline, PostgreSQL, and Redis adapters are included. The default adapter in new Rails applications is the asynchronous (`async`) adapter. To create your own adapter, you can look at `ActionCable::SubscriptionAdapter::Base` for all methods that must be implemented, and any of the adapters included within Action Cable as example implementations.
 
 The Ruby side of things is built on top of [websocket-driver](https://github.com/faye/websocket-driver-ruby), [nio4r](https://github.com/celluloid/nio4r), and [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby).
 
@@ -454,9 +454,9 @@ The Ruby side of things is built on top of [websocket-driver](https://github.com
 ## Deployment
 
 Action Cable is powered by a combination of WebSockets and threads. All of the
-connection management is handled internally by utilizing Ruby’s native thread
+connection management is handled internally by utilizing Ruby's native thread
 support, which means you can use all your regular Rails models with no problems
-as long as you haven’t committed any thread-safety sins.
+as long as you haven't committed any thread-safety sins.
 
 The Action Cable server does _not_ need to be a multi-threaded application server.
 This is because Action Cable uses the [Rack socket hijacking API](http://www.rubydoc.info/github/rack/rack/file/SPEC#Hijacking)
@@ -558,7 +558,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actioncable/lib/action_cable.rb b/actioncable/lib/action_cable.rb
index bd828b2d0f..001a043409 100644
--- a/actioncable/lib/action_cable.rb
+++ b/actioncable/lib/action_cable.rb
@@ -25,7 +25,7 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "action_cable/version"
+require "action_cable/version"
 
 module ActionCable
   extend ActiveSupport::Autoload
diff --git a/actioncable/lib/action_cable/connection/client_socket.rb b/actioncable/lib/action_cable/connection/client_socket.rb
index ba33c8b982..10289ab55c 100644
--- a/actioncable/lib/action_cable/connection/client_socket.rb
+++ b/actioncable/lib/action_cable/connection/client_socket.rb
@@ -21,7 +21,7 @@ module ActionCable
         return true if env["HTTP_X_FORWARDED_PROTO"] == "https"
         return true if env["rack.url_scheme"] == "https"
 
-        return false
+        false
       end
 
       CONNECTING = 0
diff --git a/actioncable/lib/action_cable/connection/subscriptions.rb b/actioncable/lib/action_cable/connection/subscriptions.rb
index faafd6d0a6..bb8d64e27a 100644
--- a/actioncable/lib/action_cable/connection/subscriptions.rb
+++ b/actioncable/lib/action_cable/connection/subscriptions.rb
@@ -43,7 +43,7 @@ module ActionCable
 
       def remove(data)
         logger.info "Unsubscribing from channel: #{data['identifier']}"
-        remove_subscription subscriptions[data["identifier"]]
+        remove_subscription find(data)
       end
 
       def remove_subscription(subscription)
diff --git a/actioncable/lib/action_cable/engine.rb b/actioncable/lib/action_cable/engine.rb
index c961f47342..53cbb597cd 100644
--- a/actioncable/lib/action_cable/engine.rb
+++ b/actioncable/lib/action_cable/engine.rb
@@ -2,7 +2,7 @@
 
 require "rails"
 require "action_cable"
-require_relative "helpers/action_cable_helper"
+require "action_cable/helpers/action_cable_helper"
 require "active_support/core_ext/hash/indifferent_access"
 
 module ActionCable
diff --git a/actioncable/lib/action_cable/gem_version.rb b/actioncable/lib/action_cable/gem_version.rb
index af8277d06e..d72ba18acd 100644
--- a/actioncable/lib/action_cable/gem_version.rb
+++ b/actioncable/lib/action_cable/gem_version.rb
@@ -10,7 +10,7 @@ module ActionCable
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actioncable/lib/action_cable/server/configuration.rb b/actioncable/lib/action_cable/server/configuration.rb
index 82fed81a18..26209537df 100644
--- a/actioncable/lib/action_cable/server/configuration.rb
+++ b/actioncable/lib/action_cable/server/configuration.rb
@@ -25,13 +25,26 @@ module ActionCable
       # Also makes sure proper dependencies are required.
       def pubsub_adapter
         adapter = (cable.fetch("adapter") { "redis" })
+
+        # Require the adapter itself and give useful feedback about
+        #   1. Missing adapter gems and
+        #   2. Adapter gems' missing dependencies.
         path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
         begin
           require path_to_adapter
-        rescue Gem::LoadError => e
-          raise Gem::LoadError, "Specified '#{adapter}' for Action Cable pubsub adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by Action Cable)."
         rescue LoadError => e
-          raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/cable.yml is valid. If you use an adapter other than 'postgresql' or 'redis' add the necessary adapter gem to the Gemfile.", e.backtrace
+          # We couldn't require the adapter itself. Raise an exception that
+          # points out config typos and missing gems.
+          if e.path == path_to_adapter
+            # We can assume that a non-builtin adapter was specified, so it's
+            # either misspelled or missing from Gemfile.
+            raise e.class, "Could not load the '#{adapter}' Action Cable pubsub adapter. Ensure that the adapter is spelled correctly in config/cable.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
+
+          # Bubbled up from the adapter require. Prefix the exception message
+          # with some guidance about how to address it and reraise.
+          else
+            raise e.class, "Error loading the '#{adapter}' Action Cable pubsub adapter. Missing a gem it depends on? #{e.message}", e.backtrace
+          end
         end
 
         adapter = adapter.camelize
diff --git a/actioncable/lib/action_cable/subscription_adapter/async.rb b/actioncable/lib/action_cable/subscription_adapter/async.rb
index 96c18c4a2f..c9930299c7 100644
--- a/actioncable/lib/action_cable/subscription_adapter/async.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/async.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "inline"
+require "action_cable/subscription_adapter/inline"
 
 module ActionCable
   module SubscriptionAdapter
diff --git a/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb b/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
deleted file mode 100644
index 07774810ce..0000000000
--- a/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
+++ /dev/null
@@ -1,89 +0,0 @@
-# frozen_string_literal: true
-
-require "thread"
-
-gem "em-hiredis", "~> 0.3.0"
-gem "redis", "~> 3.0"
-require "em-hiredis"
-require "redis"
-
-EventMachine.epoll  if EventMachine.epoll?
-EventMachine.kqueue if EventMachine.kqueue?
-
-module ActionCable
-  module SubscriptionAdapter
-    class EventedRedis < Base # :nodoc:
-      prepend ChannelPrefix
-
-      @@mutex = Mutex.new
-
-      # Overwrite this factory method for EventMachine Redis connections if you want to use a different Redis connection library than EM::Hiredis.
-      # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor :em_redis_connector, default: ->(config) { EM::Hiredis.connect(config[:url]) }
-
-      # Overwrite this factory method for Redis connections if you want to use a different Redis connection library than Redis.
-      # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor :redis_connector, default: ->(config) { ::Redis.new(url: config[:url]) }
-
-      def initialize(*)
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
-          The "evented_redis" subscription adapter is deprecated and
-          will be removed in Rails 5.2. Please use the "redis" adapter
-          instead.
-        MSG
-
-        super
-        @redis_connection_for_broadcasts = @redis_connection_for_subscriptions = nil
-      end
-
-      def broadcast(channel, payload)
-        redis_connection_for_broadcasts.publish(channel, payload)
-      end
-
-      def subscribe(channel, message_callback, success_callback = nil)
-        redis_connection_for_subscriptions.pubsub.subscribe(channel, &message_callback).tap do |result|
-          result.callback { |reply| success_callback.call } if success_callback
-        end
-      end
-
-      def unsubscribe(channel, message_callback)
-        redis_connection_for_subscriptions.pubsub.unsubscribe_proc(channel, message_callback)
-      end
-
-      def shutdown
-        redis_connection_for_subscriptions.pubsub.close_connection
-        @redis_connection_for_subscriptions = nil
-      end
-
-      private
-        def redis_connection_for_subscriptions
-          ensure_reactor_running
-          @redis_connection_for_subscriptions || @server.mutex.synchronize do
-            @redis_connection_for_subscriptions ||= self.class.em_redis_connector.call(@server.config.cable).tap do |redis|
-              redis.on(:reconnect_failed) do
-                @logger.error "[ActionCable] Redis reconnect failed."
-              end
-
-              redis.on(:failed) do
-                @logger.error "[ActionCable] Redis connection has failed."
-              end
-            end
-          end
-        end
-
-        def redis_connection_for_broadcasts
-          @redis_connection_for_broadcasts || @server.mutex.synchronize do
-            @redis_connection_for_broadcasts ||= self.class.redis_connector.call(@server.config.cable)
-          end
-        end
-
-        def ensure_reactor_running
-          return if EventMachine.reactor_running? && EventMachine.reactor_thread
-          @@mutex.synchronize do
-            Thread.new { EventMachine.run } unless EventMachine.reactor_running?
-            Thread.pass until EventMachine.reactor_running? && EventMachine.reactor_thread
-          end
-        end
-    end
-  end
-end
diff --git a/actioncable/lib/action_cable/subscription_adapter/redis.rb b/actioncable/lib/action_cable/subscription_adapter/redis.rb
index facea944ff..c28951608f 100644
--- a/actioncable/lib/action_cable/subscription_adapter/redis.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/redis.rb
@@ -2,7 +2,7 @@
 
 require "thread"
 
-gem "redis", "~> 3.0"
+gem "redis", ">= 3", "< 5"
 require "redis"
 
 module ActionCable
@@ -76,7 +76,7 @@ module ActionCable
 
           def listen(conn)
             conn.without_reconnect do
-              original_client = conn.client
+              original_client = conn.respond_to?(:_client) ? conn._client : conn.client
 
               conn.subscribe("_action_cable_internal") do |on|
                 on.subscribe do |chan, count|
diff --git a/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb b/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb.tt
index d672697283..d672697283 100644
--- a/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb
+++ b/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb b/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb.tt
index 0ff5442f47..0ff5442f47 100644
--- a/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb
+++ b/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/cable.js b/actioncable/lib/rails/generators/channel/templates/assets/cable.js.tt
index 739aa5f022..739aa5f022 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/cable.js
+++ b/actioncable/lib/rails/generators/channel/templates/assets/cable.js.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee b/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt
index 5467811aba..5467811aba 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee
+++ b/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/channel.js b/actioncable/lib/rails/generators/channel/templates/assets/channel.js.tt
index ab0e68b11a..ab0e68b11a 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/channel.js
+++ b/actioncable/lib/rails/generators/channel/templates/assets/channel.js.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/channel.rb b/actioncable/lib/rails/generators/channel/templates/channel.rb.tt
index 4bcfb2be4d..4bcfb2be4d 100644
--- a/actioncable/lib/rails/generators/channel/templates/channel.rb
+++ b/actioncable/lib/rails/generators/channel/templates/channel.rb.tt
diff --git a/actioncable/package.json b/actioncable/package.json
index acec1e2e9c..8d7f9ff302 100644
--- a/actioncable/package.json
+++ b/actioncable/package.json
@@ -1,6 +1,6 @@
 {
   "name": "actioncable",
-  "version": "5.2.0-alpha",
+  "version": "5.2.0-beta2",
   "description": "WebSocket framework for Ruby on Rails.",
   "main": "lib/assets/compiled/action_cable.js",
   "files": [
diff --git a/actioncable/test/connection/client_socket_test.rb b/actioncable/test/connection/client_socket_test.rb
index 2051216010..5c31690c8b 100644
--- a/actioncable/test/connection/client_socket_test.rb
+++ b/actioncable/test/connection/client_socket_test.rb
@@ -67,9 +67,9 @@ class ActionCable::Connection::ClientSocketTest < ActionCable::TestCase
       env = Rack::MockRequest.env_for "/test",
         "HTTP_CONNECTION" => "upgrade", "HTTP_UPGRADE" => "websocket",
         "HTTP_HOST" => "localhost", "HTTP_ORIGIN" => "http://rubyonrails.com"
-      io = \
+      io, client_io = \
         begin
-          Socket.pair(Socket::AF_UNIX, Socket::SOCK_STREAM, 0).first
+          Socket.pair(Socket::AF_UNIX, Socket::SOCK_STREAM, 0)
         rescue
           StringIO.new
         end
@@ -77,6 +77,14 @@ class ActionCable::Connection::ClientSocketTest < ActionCable::TestCase
 
       Connection.new(@server, env).tap do |connection|
         connection.process
+        if client_io
+          # Make sure server returns handshake response
+          Timeout.timeout(1) do
+            loop do
+              break if client_io.readline == "\r\n"
+            end
+          end
+        end
         connection.send :handle_open
         assert connection.connected
       end
diff --git a/actioncable/test/subscription_adapter/evented_redis_test.rb b/actioncable/test/subscription_adapter/evented_redis_test.rb
deleted file mode 100644
index e3e0a0c72a..0000000000
--- a/actioncable/test/subscription_adapter/evented_redis_test.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-# frozen_string_literal: true
-
-require "test_helper"
-require_relative "common"
-require_relative "channel_prefix"
-
-class EventedRedisAdapterTest < ActionCable::TestCase
-  include CommonSubscriptionAdapterTest
-  include ChannelPrefixTest
-
-  def setup
-    assert_deprecated do
-      super
-    end
-
-    # em-hiredis is warning-rich
-    @previous_verbose, $VERBOSE = $VERBOSE, nil
-  end
-
-  def teardown
-    super
-
-    # Ensure EM is shut down before we re-enable warnings
-    EventMachine.reactor_thread.tap do |thread|
-      EventMachine.stop
-      thread.join
-    end
-
-    $VERBOSE = @previous_verbose
-  end
-
-  def test_slow_eventmachine
-    require "eventmachine"
-    require "thread"
-
-    lock = Mutex.new
-
-    EventMachine.singleton_class.class_eval do
-      alias_method :delayed_initialize_event_machine, :initialize_event_machine
-      define_method(:initialize_event_machine) do
-        lock.synchronize do
-          sleep 0.5
-          delayed_initialize_event_machine
-        end
-      end
-    end
-
-    test_basic_broadcast
-  ensure
-    lock.synchronize do
-      EventMachine.singleton_class.class_eval do
-        alias_method :initialize_event_machine, :delayed_initialize_event_machine
-        remove_method :delayed_initialize_event_machine
-      end
-    end
-  end
-
-  def cable_config
-    { adapter: "evented_redis", url: "redis://:password@127.0.0.1:6379/12" }
-  end
-end
diff --git a/actioncable/test/subscription_adapter/redis_test.rb b/actioncable/test/subscription_adapter/redis_test.rb
index 69120d5753..63823d6ef0 100644
--- a/actioncable/test/subscription_adapter/redis_test.rb
+++ b/actioncable/test/subscription_adapter/redis_test.rb
@@ -4,12 +4,15 @@ require "test_helper"
 require_relative "common"
 require_relative "channel_prefix"
 
+require "active_support/testing/method_call_assertions"
+require "action_cable/subscription_adapter/redis"
+
 class RedisAdapterTest < ActionCable::TestCase
   include CommonSubscriptionAdapterTest
   include ChannelPrefixTest
 
   def cable_config
-    { adapter: "redis", driver: "ruby", url: "redis://:password@127.0.0.1:6379/12" }
+    { adapter: "redis", driver: "ruby" }
   end
 end
 
@@ -23,6 +26,22 @@ class RedisAdapterTest::AlternateConfiguration < RedisAdapterTest
   def cable_config
     alt_cable_config = super.dup
     alt_cable_config.delete(:url)
-    alt_cable_config.merge(host: "127.0.0.1", port: 6379, db: 12, password: "password")
+    alt_cable_config.merge(host: "127.0.0.1", port: 6379, db: 12)
+  end
+end
+
+class RedisAdapterTest::Connector < ActiveSupport::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
+  test "slices url, host, port, db, and password from config" do
+    config = { url: 1, host: 2, port: 3, db: 4, password: 5 }
+
+    assert_called_with ::Redis, :new, [ config ] do
+      connect config.merge(other: "unrelated", stuff: "here")
+    end
+  end
+
+  def connect(config)
+    ActionCable::SubscriptionAdapter::Redis.redis_connector.call(config)
   end
 end
diff --git a/actionmailer/CHANGELOG.md b/actionmailer/CHANGELOG.md
index 9993a11c9d..2836f0cfbc 100644
--- a/actionmailer/CHANGELOG.md
+++ b/actionmailer/CHANGELOG.md
@@ -1,3 +1,18 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Add `assert_enqueued_email_with` test helper.
+
+        assert_enqueued_email_with ContactMailer, :welcome do
+          ContactMailer.welcome.deliver_later
+        end
+
+    *Mikkel Malmberg*
+
 *   Allow Action Mailer classes to configure their delivery job.
 
         class MyMailer < ApplicationMailer
diff --git a/actionmailer/README.rdoc b/actionmailer/README.rdoc
index 9993d3777d..14dfb82234 100644
--- a/actionmailer/README.rdoc
+++ b/actionmailer/README.rdoc
@@ -148,7 +148,7 @@ The latest version of Action Mailer can be installed with RubyGems:
 
   $ gem install actionmailer
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/actionmailer
 
@@ -166,7 +166,7 @@ API documentation is at
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actionmailer/lib/action_mailer.rb b/actionmailer/lib/action_mailer.rb
index a170eb7917..ade3fe39a2 100644
--- a/actionmailer/lib/action_mailer.rb
+++ b/actionmailer/lib/action_mailer.rb
@@ -24,7 +24,7 @@
 #++
 
 require "abstract_controller"
-require_relative "action_mailer/version"
+require "action_mailer/version"
 
 # Common Active Support usage in Action Mailer
 require "active_support"
diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 1c1e1a9a3b..eb8ae59533 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
 require "mail"
-require_relative "collector"
+require "action_mailer/collector"
 require "active_support/core_ext/string/inflections"
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/module/anonymous"
 
-require_relative "log_subscriber"
-require_relative "rescuable"
+require "action_mailer/log_subscriber"
+require "action_mailer/rescuable"
 
 module ActionMailer
   # Action Mailer allows you to send email from your application using a mailer model and views.
diff --git a/actionmailer/lib/action_mailer/gem_version.rb b/actionmailer/lib/action_mailer/gem_version.rb
index 063d4580d8..6a7dd0a212 100644
--- a/actionmailer/lib/action_mailer/gem_version.rb
+++ b/actionmailer/lib/action_mailer/gem_version.rb
@@ -10,7 +10,7 @@ module ActionMailer
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionmailer/lib/action_mailer/preview.rb b/actionmailer/lib/action_mailer/preview.rb
index 730ac89c94..0aea84fd2b 100644
--- a/actionmailer/lib/action_mailer/preview.rb
+++ b/actionmailer/lib/action_mailer/preview.rb
@@ -104,7 +104,7 @@ module ActionMailer
       private
         def load_previews
           if preview_path
-            Dir["#{preview_path}/**/*_preview.rb"].each { |file| require_dependency file }
+            Dir["#{preview_path}/**/*_preview.rb"].sort.each { |file| require_dependency file }
           end
         end
 
diff --git a/actionmailer/lib/action_mailer/test_helper.rb b/actionmailer/lib/action_mailer/test_helper.rb
index ac8b944743..8ee4d06915 100644
--- a/actionmailer/lib/action_mailer/test_helper.rb
+++ b/actionmailer/lib/action_mailer/test_helper.rb
@@ -93,6 +93,48 @@ module ActionMailer
       assert_enqueued_jobs number, only: [ ActionMailer::DeliveryJob, ActionMailer::Parameterized::DeliveryJob ], &block
     end
 
+    # Asserts that a specific email has been enqueued, optionally
+    # matching arguments.
+    #
+    #   def test_email
+    #     ContactMailer.welcome.deliver_later
+    #     assert_enqueued_email_with ContactMailer, :welcome
+    #   end
+    #
+    #   def test_email_with_arguments
+    #     ContactMailer.welcome("Hello", "Goodbye").deliver_later
+    #     assert_enqueued_email_with ContactMailer, :welcome, args: ["Hello", "Goodbye"]
+    #   end
+    #
+    # If a block is passed, that block should cause the specified email
+    # to be enqueued.
+    #
+    #   def test_email_in_block
+    #     assert_enqueued_email_with ContactMailer, :welcome do
+    #       ContactMailer.welcome.deliver_later
+    #     end
+    #   end
+    #
+    # If `args` is provided as a Hash, a parameterized email is matched.
+    #
+    #   def test_parameterized_email
+    #     assert_enqueued_email_with ContactMailer, :welcome,
+    #       args: {email: 'user@example.com} do
+    #       ContactMailer.with(email: 'user@example.com').welcome.deliver_later
+    #     end
+    #   end
+    def assert_enqueued_email_with(mailer, method, args: nil, queue: "mailers", &block)
+      if args.is_a? Hash
+        job = ActionMailer::Parameterized::DeliveryJob
+        args = [mailer.to_s, method.to_s, "deliver_now", args]
+      else
+        job = ActionMailer::DeliveryJob
+        args = [mailer.to_s, method.to_s, "deliver_now", *args]
+      end
+
+      assert_enqueued_with(job: job, args: args, queue: queue, &block)
+    end
+
     # Asserts that no emails are enqueued for later delivery.
     #
     #   def test_no_emails
diff --git a/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb b/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb.tt
index 00fb9bd48f..00fb9bd48f 100644
--- a/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb
+++ b/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb.tt
diff --git a/actionmailer/lib/rails/generators/mailer/templates/mailer.rb b/actionmailer/lib/rails/generators/mailer/templates/mailer.rb.tt
index 348d314758..348d314758 100644
--- a/actionmailer/lib/rails/generators/mailer/templates/mailer.rb
+++ b/actionmailer/lib/rails/generators/mailer/templates/mailer.rb.tt
diff --git a/actionmailer/test/base_test.rb b/actionmailer/test/base_test.rb
index 0da969c349..977e0e201e 100644
--- a/actionmailer/test/base_test.rb
+++ b/actionmailer/test/base_test.rb
@@ -322,22 +322,21 @@ class BaseTest < ActiveSupport::TestCase
 
   test "implicit multipart with attachments creates nested parts" do
     email = BaseMailer.implicit_multipart(attachments: true)
-    assert_equal("application/pdf", email.parts[0].mime_type)
-    assert_equal("multipart/alternative", email.parts[1].mime_type)
-    assert_equal("text/plain", email.parts[1].parts[0].mime_type)
-    assert_equal("TEXT Implicit Multipart", email.parts[1].parts[0].body.encoded)
-    assert_equal("text/html", email.parts[1].parts[1].mime_type)
-    assert_equal("HTML Implicit Multipart", email.parts[1].parts[1].body.encoded)
+    assert_equal(%w[ application/pdf multipart/alternative ], email.parts.map(&:mime_type).sort)
+    multipart = email.parts.detect { |p| p.mime_type == "multipart/alternative" }
+    assert_equal("text/plain", multipart.parts[0].mime_type)
+    assert_equal("TEXT Implicit Multipart", multipart.parts[0].body.encoded)
+    assert_equal("text/html", multipart.parts[1].mime_type)
+    assert_equal("HTML Implicit Multipart", multipart.parts[1].body.encoded)
   end
 
   test "implicit multipart with attachments and sort order" do
     order = ["text/html", "text/plain"]
     with_default BaseMailer, parts_order: order do
       email = BaseMailer.implicit_multipart(attachments: true)
-      assert_equal("application/pdf", email.parts[0].mime_type)
-      assert_equal("multipart/alternative", email.parts[1].mime_type)
-      assert_equal("text/plain", email.parts[1].parts[1].mime_type)
-      assert_equal("text/html", email.parts[1].parts[0].mime_type)
+      assert_equal(%w[ application/pdf multipart/alternative ], email.parts.map(&:mime_type).sort)
+      multipart = email.parts.detect { |p| p.mime_type == "multipart/alternative" }
+      assert_equal(%w[ text/html text/plain ], multipart.parts.map(&:mime_type).sort)
     end
   end
 
@@ -427,12 +426,12 @@ class BaseTest < ActiveSupport::TestCase
 
   test "explicit multipart with attachments creates nested parts" do
     email = BaseMailer.explicit_multipart(attachments: true)
-    assert_equal("application/pdf", email.parts[0].mime_type)
-    assert_equal("multipart/alternative", email.parts[1].mime_type)
-    assert_equal("text/plain", email.parts[1].parts[0].mime_type)
-    assert_equal("TEXT Explicit Multipart", email.parts[1].parts[0].body.encoded)
-    assert_equal("text/html", email.parts[1].parts[1].mime_type)
-    assert_equal("HTML Explicit Multipart", email.parts[1].parts[1].body.encoded)
+    assert_equal(%w[ application/pdf multipart/alternative ], email.parts.map(&:mime_type).sort)
+    multipart = email.parts.detect { |p| p.mime_type == "multipart/alternative" }
+    assert_equal("text/plain", multipart.parts[0].mime_type)
+    assert_equal("TEXT Explicit Multipart", multipart.parts[0].body.encoded)
+    assert_equal("text/html", multipart.parts[1].mime_type)
+    assert_equal("HTML Explicit Multipart", multipart.parts[1].body.encoded)
   end
 
   test "explicit multipart with templates" do
diff --git a/actionmailer/test/caching_test.rb b/actionmailer/test/caching_test.rb
index e11e8d4676..ae4e7bf57e 100644
--- a/actionmailer/test/caching_test.rb
+++ b/actionmailer/test/caching_test.rb
@@ -198,7 +198,7 @@ end
 class CacheHelperOutputBufferTest < BaseCachingTest
   class MockController
     def read_fragment(name, options)
-      return false
+      false
     end
 
     def write_fragment(name, fragment, options)
@@ -214,9 +214,9 @@ class CacheHelperOutputBufferTest < BaseCachingTest
     output_buffer = ActionView::OutputBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
@@ -235,9 +235,9 @@ class CacheHelperOutputBufferTest < BaseCachingTest
     output_buffer = ActiveSupport::SafeBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
diff --git a/actionmailer/test/test_helper_test.rb b/actionmailer/test/test_helper_test.rb
index abf50cf4da..3866097389 100644
--- a/actionmailer/test/test_helper_test.rb
+++ b/actionmailer/test/test_helper_test.rb
@@ -10,6 +10,18 @@ class TestHelperMailer < ActionMailer::Base
       to: "test@example.com",
       from: "tester@example.com"
   end
+
+  def test_args(recipient, name)
+    mail body: render(inline: "Hello, #{name}"),
+      to: recipient,
+      from: "tester@example.com"
+  end
+
+  def test_parameter_args
+    mail body: render(inline: "All is #{params[:all]}"),
+      to: "test@example.com",
+      from: "tester@example.com"
+  end
 end
 
 class TestHelperMailerTest < ActionMailer::TestCase
@@ -42,7 +54,7 @@ class TestHelperMailerTest < ActionMailer::TestCase
   end
 
   def test_encode
-    assert_equal "=?UTF-8?Q?This_is_=E3=81=82_string?=", encode("This is あ string")
+    assert_equal "This is あ string", Mail::Encodings.q_value_decode(encode("This is あ string"))
   end
 
   def test_read_fixture
@@ -207,6 +219,36 @@ class TestHelperMailerTest < ActionMailer::TestCase
 
     assert_match(/0 .* but 1/, error.message)
   end
+
+  def test_assert_enqueued_email_with
+    assert_nothing_raised do
+      assert_enqueued_email_with TestHelperMailer, :test do
+        silence_stream($stdout) do
+          TestHelperMailer.test.deliver_later
+        end
+      end
+    end
+  end
+
+  def test_assert_enqueued_email_with_args
+    assert_nothing_raised do
+      assert_enqueued_email_with TestHelperMailer, :test_args, args: ["some_email", "some_name"] do
+        silence_stream($stdout) do
+          TestHelperMailer.test_args("some_email", "some_name").deliver_later
+        end
+      end
+    end
+  end
+
+  def test_assert_enqueued_email_with_parameterized_args
+    assert_nothing_raised do
+      assert_enqueued_email_with TestHelperMailer, :test_parameter_args, args: { all: "good" } do
+        silence_stream($stdout) do
+          TestHelperMailer.with(all: "good").test_parameter_args.deliver_later
+        end
+      end
+    end
+  end
 end
 
 class AnotherTestHelperMailerTest < ActionMailer::TestCase
diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 932968fa35..753dd8589a 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,4 +1,141 @@
-*  Cookies `:expires` option supports `ActiveSupport::Duration` object.
+*   Add headless firefox support to System Tests.
+
+    *bogdanvlviv*
+
+*   Changed the default system test screenshot output from `inline` to `simple`.
+
+    `inline` works well for iTerm2 but not everyone uses iTerm2. Some terminals like
+    Terminal.app ignore the `inline` and output the path to the file since it can't
+    render the image. Other terminals, like those on Ubuntu, cannot handle the image
+    inline, but also don't handle it gracefully and instead of outputting the file
+    path, it dumps binary into the terminal.
+
+    Commit 9d6e28 fixes this by changing the default for screenshot to be `simple`.
+
+    *Eileen M. Uchitelle*
+
+*   Register most popular audio/video/font mime types supported by modern browsers.
+
+    *Guillermo Iguaran*
+
+*   Fix optimized url helpers when using relative url root
+
+    Fixes #31220.
+
+    *Andrew White*
+
+
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Add DSL for configuring Content-Security-Policy header
+
+    The DSL allows you to configure a global Content-Security-Policy
+    header and then override within a controller. For more information
+    about the Content-Security-Policy header see MDN:
+
+    https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
+
+    Example global policy:
+
+        # config/initializers/content_security_policy.rb
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+          p.font_src    :self, :https, :data
+          p.img_src     :self, :https, :data
+          p.object_src  :none
+          p.script_src  :self, :https
+          p.style_src   :self, :https, :unsafe_inline
+        end
+
+    Example controller overrides:
+
+        # Override policy inline
+        class PostsController < ApplicationController
+          content_security_policy do |p|
+            p.upgrade_insecure_requests true
+          end
+        end
+
+        # Using literal values
+        class PostsController < ApplicationController
+          content_security_policy do |p|
+            p.base_uri "https://www.example.com"
+          end
+        end
+
+        # Using mixed static and dynamic values
+        class PostsController < ApplicationController
+          content_security_policy do |p|
+            p.base_uri :self, -> { "https://#{current_user.domain}.example.com" }
+          end
+        end
+
+    Allows you to also only report content violations for migrating
+    legacy content using the `content_security_policy_report_only`
+    configuration attribute, e.g;
+
+        # config/initializers/content_security_policy.rb
+        Rails.application.config.content_security_policy_report_only = true
+
+        # controller override
+        class PostsController < ApplicationController
+          self.content_security_policy_report_only = true
+        end
+
+    Note that this feature does not validate the header for performance
+    reasons since the header is calculated at runtime.
+
+    *Andrew White*
+
+*   Make `assert_recognizes` to traverse mounted engines
+
+    *Yuichiro Kaneko*
+
+*   Remove deprecated `ActionController::ParamsParser::ParseError`.
+
+    *Rafael Mendonça França*
+
+*   Add `:allow_other_host` option to `redirect_back` method.
+    When `allow_other_host` is set to `false`, the `redirect_back`
+    will not allow a redirecting from a different host.
+    `allow_other_host` is `true` by default.
+
+    *Tim Masliuchenko*
+
+*   Add headless chrome support to System Tests.
+
+    *Yuji Yaginuma*
+
+*   Add ability to enable Early Hints for HTTP/2
+
+    If supported by the server, and enabled in Puma this allows H2 Early Hints to be used.
+
+    The `javascript_include_tag` and the `stylesheet_link_tag` automatically add Early Hints if requested.
+
+    *Eileen M. Uchitelle*, *Aaron Patterson*
+
+*   Simplify cookies middleware with key rotation support
+
+    Use the `rotate` method for both `MessageEncryptor` and
+    `MessageVerifier` to add key rotation support for encrypted and
+    signed cookies. This also helps simplify support for legacy cookie
+    security.
+
+    *Michael J Coyne*
+
+*   Use Capybara registered `:puma` server config.
+
+    The Capybara registered `:puma` server ensures the puma server is run in process so
+    connection sharing and open request detection work correctly by default.
+
+    *Thomas Walpole*
+
+*   Cookies `:expires` option supports `ActiveSupport::Duration` object.
 
         cookies[:user_name] = { value: "assain", expires: 1.hour }
         cookies[:key] = { value: "a yummy cookie", expires: 6.months }
@@ -7,7 +144,7 @@
 
     *Assain Jaleel*
 
-*  Enforce signed/encrypted cookie expiry server side.
+*   Enforce signed/encrypted cookie expiry server side.
 
     Rails can thwart attacks by malicious clients that don't honor a cookie's expiry.
 
@@ -47,7 +184,7 @@
 
     *Kir Shatrov*
 
-*   `driven_by` now registers poltergeist and capybara-webkit
+*   `driven_by` now registers poltergeist and capybara-webkit.
 
     If poltergeist or capybara-webkit are set as drivers is set for System Tests,
     `driven_by` will register the driver and set additional options passed via
@@ -57,7 +194,7 @@
 
     *Mario Chavez*
 
-*   AEAD encrypted cookies and sessions with GCM
+*   AEAD encrypted cookies and sessions with GCM.
 
     Encrypted cookies now use AES-GCM which couples authentication and
     encryption in one faster step and produces shorter ciphertexts. Cookies
diff --git a/actionpack/README.rdoc b/actionpack/README.rdoc
index 93b2a0932a..f56230ffa0 100644
--- a/actionpack/README.rdoc
+++ b/actionpack/README.rdoc
@@ -30,7 +30,7 @@ The latest version of Action Pack can be installed with RubyGems:
 
   $ gem install actionpack
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/actionpack
 
@@ -44,11 +44,11 @@ Action Pack is released under the MIT license:
 
 == Support
 
-API documentation is at
+API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actionpack/lib/abstract_controller/base.rb b/actionpack/lib/abstract_controller/base.rb
index 3761054bb7..a312af6715 100644
--- a/actionpack/lib/abstract_controller/base.rb
+++ b/actionpack/lib/abstract_controller/base.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "error"
+require "abstract_controller/error"
 require "active_support/configurable"
 require "active_support/descendants_tracker"
 require "active_support/core_ext/module/anonymous"
@@ -180,8 +180,6 @@ module AbstractController
       #
       # ==== Parameters
       # * <tt>name</tt> - The name of an action to be tested
-      #
-      # :api: private
       def action_method?(name)
         self.class.action_methods.include?(name)
       end
diff --git a/actionpack/lib/abstract_controller/rendering.rb b/actionpack/lib/abstract_controller/rendering.rb
index 41898c4c2e..8ba2b25552 100644
--- a/actionpack/lib/abstract_controller/rendering.rb
+++ b/actionpack/lib/abstract_controller/rendering.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "error"
+require "abstract_controller/error"
 require "action_view"
 require "action_view/view_paths"
 require "set"
@@ -20,7 +20,6 @@ module AbstractController
 
     # Normalizes arguments, options and then delegates render_to_body and
     # sticks the result in <tt>self.response_body</tt>.
-    # :api: public
     def render(*args, &block)
       options = _normalize_render(*args, &block)
       rendered_body = render_to_body(options)
@@ -42,19 +41,16 @@ module AbstractController
     # (as ActionController extends it to be anything that
     # responds to the method each), this method needs to be
     # overridden in order to still return a string.
-    # :api: plugin
     def render_to_string(*args, &block)
       options = _normalize_render(*args, &block)
       render_to_body(options)
     end
 
     # Performs the actual template rendering.
-    # :api: public
     def render_to_body(options = {})
     end
 
-    # Returns Content-Type of rendered content
-    # :api: public
+    # Returns Content-Type of rendered content.
     def rendered_format
       Mime[:text]
     end
@@ -65,7 +61,6 @@ module AbstractController
 
     # This method should return a hash with assigns.
     # You can overwrite this configuration per controller.
-    # :api: public
     def view_assigns
       protected_vars = _protected_ivars
       variables      = instance_variables
@@ -76,11 +71,11 @@ module AbstractController
       }
     end
 
+  private
     # Normalize args by converting <tt>render "foo"</tt> to
     # <tt>render :action => "foo"</tt> and <tt>render "foo/bar"</tt> to
     # <tt>render :file => "foo/bar"</tt>.
-    # :api: plugin
-    def _normalize_args(action = nil, options = {})
+    def _normalize_args(action = nil, options = {}) # :doc:
       if action.respond_to?(:permitted?)
         if action.permitted?
           action
@@ -95,20 +90,17 @@ module AbstractController
     end
 
     # Normalize options.
-    # :api: plugin
-    def _normalize_options(options)
+    def _normalize_options(options) # :doc:
       options
     end
 
     # Process extra options.
-    # :api: plugin
-    def _process_options(options)
+    def _process_options(options) # :doc:
       options
     end
 
     # Process the rendered format.
-    # :api: private
-    def _process_format(format)
+    def _process_format(format) # :nodoc:
     end
 
     def _process_variant(options)
@@ -121,8 +113,7 @@ module AbstractController
     end
 
     # Normalize args and options.
-    # :api: private
-    def _normalize_render(*args, &block)
+    def _normalize_render(*args, &block) # :nodoc:
       options = _normalize_args(*args, &block)
       _process_variant(options)
       _normalize_options(options)
diff --git a/actionpack/lib/action_controller.rb b/actionpack/lib/action_controller.rb
index e893507baa..f43784f9f2 100644
--- a/actionpack/lib/action_controller.rb
+++ b/actionpack/lib/action_controller.rb
@@ -3,8 +3,8 @@
 require "active_support/rails"
 require "abstract_controller"
 require "action_dispatch"
-require_relative "action_controller/metal/live"
-require_relative "action_controller/metal/strong_parameters"
+require "action_controller/metal/live"
+require "action_controller/metal/strong_parameters"
 
 module ActionController
   extend ActiveSupport::Autoload
@@ -22,6 +22,7 @@ module ActionController
 
   autoload_under "metal" do
     autoload :ConditionalGet
+    autoload :ContentSecurityPolicy
     autoload :Cookies
     autoload :DataStreaming
     autoload :EtagWithTemplateDigest
diff --git a/actionpack/lib/action_controller/api.rb b/actionpack/lib/action_controller/api.rb
index ba9af4767e..b192e496de 100644
--- a/actionpack/lib/action_controller/api.rb
+++ b/actionpack/lib/action_controller/api.rb
@@ -2,7 +2,7 @@
 
 require "action_view"
 require "action_controller"
-require_relative "log_subscriber"
+require "action_controller/log_subscriber"
 
 module ActionController
   # API Controller is a lightweight version of <tt>ActionController::Base</tt>,
diff --git a/actionpack/lib/action_controller/base.rb b/actionpack/lib/action_controller/base.rb
index bbc48e6eb7..204a3d400c 100644
--- a/actionpack/lib/action_controller/base.rb
+++ b/actionpack/lib/action_controller/base.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require "action_view"
-require_relative "log_subscriber"
-require_relative "metal/params_wrapper"
+require "action_controller/log_subscriber"
+require "action_controller/metal/params_wrapper"
 
 module ActionController
   # Action Controllers are the core of a web request in \Rails. They are made up of one or more actions that are executed
@@ -225,6 +225,7 @@ module ActionController
       Flash,
       FormBuilder,
       RequestForgeryProtection,
+      ContentSecurityPolicy,
       ForceSSL,
       Streaming,
       DataStreaming,
diff --git a/actionpack/lib/action_controller/metal/content_security_policy.rb b/actionpack/lib/action_controller/metal/content_security_policy.rb
new file mode 100644
index 0000000000..48a7109bea
--- /dev/null
+++ b/actionpack/lib/action_controller/metal/content_security_policy.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module ActionController #:nodoc:
+  module ContentSecurityPolicy
+    # TODO: Documentation
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      def content_security_policy(**options, &block)
+        before_action(options) do
+          if block_given?
+            policy = request.content_security_policy.clone
+            yield policy
+            request.content_security_policy = policy
+          end
+        end
+      end
+
+      def content_security_policy_report_only(report_only = true, **options)
+        before_action(options) do
+          request.content_security_policy_report_only = report_only
+        end
+      end
+    end
+  end
+end
diff --git a/actionpack/lib/action_controller/metal/data_streaming.rb b/actionpack/lib/action_controller/metal/data_streaming.rb
index 882f6f3d0a..5a82ccf668 100644
--- a/actionpack/lib/action_controller/metal/data_streaming.rb
+++ b/actionpack/lib/action_controller/metal/data_streaming.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "exceptions"
+require "action_controller/metal/exceptions"
 
 module ActionController #:nodoc:
   # Methods for sending arbitrary data and for streaming files to the browser,
diff --git a/actionpack/lib/action_controller/metal/exceptions.rb b/actionpack/lib/action_controller/metal/exceptions.rb
index f808295720..a65857d6ef 100644
--- a/actionpack/lib/action_controller/metal/exceptions.rb
+++ b/actionpack/lib/action_controller/metal/exceptions.rb
@@ -34,9 +34,6 @@ module ActionController
   class NotImplemented < MethodNotAllowed #:nodoc:
   end
 
-  class UnknownController < ActionControllerError #:nodoc:
-  end
-
   class MissingFile < ActionControllerError #:nodoc:
   end
 
diff --git a/actionpack/lib/action_controller/metal/http_authentication.rb b/actionpack/lib/action_controller/metal/http_authentication.rb
index 08d9b094f3..01676f3237 100644
--- a/actionpack/lib/action_controller/metal/http_authentication.rb
+++ b/actionpack/lib/action_controller/metal/http_authentication.rb
@@ -72,10 +72,10 @@ module ActionController
             before_action(options.except(:name, :password, :realm)) do
               authenticate_or_request_with_http_basic(options[:realm] || "Application") do |name, password|
                 # This comparison uses & so that it doesn't short circuit and
-                # uses `variable_size_secure_compare` so that length information
+                # uses `secure_compare` so that length information
                 # isn't leaked.
-                ActiveSupport::SecurityUtils.variable_size_secure_compare(name, options[:name]) &
-                  ActiveSupport::SecurityUtils.variable_size_secure_compare(password, options[:password])
+                ActiveSupport::SecurityUtils.secure_compare(name, options[:name]) &
+                  ActiveSupport::SecurityUtils.secure_compare(password, options[:password])
               end
             end
           end
@@ -248,7 +248,7 @@ module ActionController
       def decode_credentials(header)
         ActiveSupport::HashWithIndifferentAccess[header.to_s.gsub(/^Digest\s+/, "").split(",").map do |pair|
           key, value = pair.split("=", 2)
-          [key.strip, value.to_s.gsub(/^"|"$/, "").delete('\'')]
+          [key.strip, value.to_s.gsub(/^"|"$/, "").delete("'")]
         end]
       end
 
@@ -350,10 +350,7 @@ module ActionController
     #         authenticate_or_request_with_http_token do |token, options|
     #           # Compare the tokens in a time-constant manner, to mitigate
     #           # timing attacks.
-    #           ActiveSupport::SecurityUtils.secure_compare(
-    #             ::Digest::SHA256.hexdigest(token),
-    #             ::Digest::SHA256.hexdigest(TOKEN)
-    #           )
+    #           ActiveSupport::SecurityUtils.secure_compare(token, TOKEN)
     #         end
     #       end
     #   end
diff --git a/actionpack/lib/action_controller/metal/instrumentation.rb b/actionpack/lib/action_controller/metal/instrumentation.rb
index 476f0843b2..be9449629f 100644
--- a/actionpack/lib/action_controller/metal/instrumentation.rb
+++ b/actionpack/lib/action_controller/metal/instrumentation.rb
@@ -83,16 +83,13 @@ module ActionController
     #   def cleanup_view_runtime
     #     super - time_taken_in_something_expensive
     #   end
-    #
-    # :api: plugin
-    def cleanup_view_runtime
+    def cleanup_view_runtime # :doc:
       yield
     end
 
     # Every time after an action is processed, this method is invoked
     # with the payload, so you can add more information.
-    # :api: plugin
-    def append_info_to_payload(payload)
+    def append_info_to_payload(payload) # :doc:
       payload[:view_runtime] = view_runtime
     end
 
@@ -100,7 +97,6 @@ module ActionController
       # A hook which allows other frameworks to log what happened during
       # controller process action. This method should return an array
       # with the messages to be added.
-      # :api: plugin
       def log_process_action(payload) #:nodoc:
         messages, view_runtime = [], payload[:view_runtime]
         messages << ("Views: %.1fms" % view_runtime.to_f) if view_runtime
diff --git a/actionpack/lib/action_controller/metal/params_wrapper.rb b/actionpack/lib/action_controller/metal/params_wrapper.rb
index f4f2381286..a678377d4f 100644
--- a/actionpack/lib/action_controller/metal/params_wrapper.rb
+++ b/actionpack/lib/action_controller/metal/params_wrapper.rb
@@ -112,6 +112,14 @@ module ActionController
               else
                 self.include = m.attribute_names
               end
+
+              if m.respond_to?(:nested_attributes_options) && m.nested_attributes_options.keys.any?
+                self.include += m.nested_attributes_options.keys.map do |key|
+                  key.to_s.concat("_attributes")
+                end
+              end
+
+              self.include
             end
           end
         end
diff --git a/actionpack/lib/action_controller/metal/redirecting.rb b/actionpack/lib/action_controller/metal/redirecting.rb
index 5cd8568d8d..87a2e29a3f 100644
--- a/actionpack/lib/action_controller/metal/redirecting.rb
+++ b/actionpack/lib/action_controller/metal/redirecting.rb
@@ -68,7 +68,7 @@ module ActionController
     # if possible, otherwise redirects to the provided default fallback
     # location.
     #
-    # The referrer information is pulled from the HTTP `Referer` (sic) header on
+    # The referrer information is pulled from the HTTP +Referer+ (sic) header on
     # the request. This is an optional header and its presence on the request is
     # subject to browser security settings and user preferences. If the request
     # is missing this header, the <tt>fallback_location</tt> will be used.
@@ -79,15 +79,18 @@ module ActionController
     #   redirect_back fallback_location: "/images/screenshot.jpg"
     #   redirect_back fallback_location: posts_url
     #   redirect_back fallback_location: proc { edit_post_url(@post) }
+    #   redirect_back fallback_location: '/', allow_other_host: false
     #
-    # All options that can be passed to <tt>redirect_to</tt> are accepted as
+    # ==== Options
+    # * <tt>:fallback_location</tt> - The default fallback location that will be used on missing +Referer+ header.
+    # * <tt>:allow_other_host</tt> - Allows or disallow redirection to the host that is different to the current host
+    #
+    # All other options that can be passed to <tt>redirect_to</tt> are accepted as
     # options and the behavior is identical.
-    def redirect_back(fallback_location:, **args)
-      if referer = request.headers["Referer"]
-        redirect_to referer, **args
-      else
-        redirect_to fallback_location, **args
-      end
+    def redirect_back(fallback_location:, allow_other_host: true, **args)
+      referer = request.headers["Referer"]
+      redirect_to_referer = referer && (allow_other_host || _url_host_allowed?(referer))
+      redirect_to redirect_to_referer ? referer : fallback_location, **args
     end
 
     def _compute_redirect_to_location(request, options) #:nodoc:
@@ -120,5 +123,11 @@ module ActionController
           302
         end
       end
+
+      def _url_host_allowed?(url)
+        URI(url.to_s).host == request.host
+      rescue ArgumentError, URI::Error
+        false
+      end
   end
 end
diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
index 813a7e00d4..767eddb361 100644
--- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb
+++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "rack/session/abstract/id"
-require_relative "exceptions"
+require "action_controller/metal/exceptions"
 require "active_support/security_utils"
 
 module ActionController #:nodoc:
@@ -216,7 +216,7 @@ module ActionController #:nodoc:
       # The actual before_action that is used to verify the CSRF token.
       # Don't override this directly. Provide your own forgery protection
       # strategy instead. If you override, you'll disable same-origin
-      # `<script>` verification.
+      # <tt><script></tt> verification.
       #
       # Lean on the protect_from_forgery declaration to mark which actions are
       # due for same-origin request verification. If protect_from_forgery is
@@ -248,8 +248,9 @@ module ActionController #:nodoc:
         "If you know what you're doing, go ahead and disable forgery " \
         "protection on this action to permit cross-origin JavaScript embedding."
       private_constant :CROSS_ORIGIN_JAVASCRIPT_WARNING
+      # :startdoc:
 
-      # If `verify_authenticity_token` was run (indicating that we have
+      # If +verify_authenticity_token+ was run (indicating that we have
       # forgery protection enabled for this request) then also verify that
       # we aren't serving an unauthorized cross-origin response.
       def verify_same_origin_request # :doc:
@@ -266,7 +267,7 @@ module ActionController #:nodoc:
         @marked_for_same_origin_verification = request.get?
       end
 
-      # If the `verify_authenticity_token` before_action ran, verify that
+      # If the +verify_authenticity_token+ before_action ran, verify that
       # JavaScript responses are only served to same-origin GET requests.
       def marked_for_same_origin_verification? # :doc:
         @marked_for_same_origin_verification ||= false
@@ -368,7 +369,7 @@ module ActionController #:nodoc:
       end
 
       def compare_with_real_token(token, session) # :doc:
-        ActiveSupport::SecurityUtils.secure_compare(token, real_csrf_token(session))
+        ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, real_csrf_token(session))
       end
 
       def valid_per_form_csrf_token?(token, session) # :doc:
@@ -379,7 +380,7 @@ module ActionController #:nodoc:
             request.request_method
           )
 
-          ActiveSupport::SecurityUtils.secure_compare(token, correct_token)
+          ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, correct_token)
         else
           false
         end
@@ -414,11 +415,21 @@ module ActionController #:nodoc:
         allow_forgery_protection
       end
 
+      NULL_ORIGIN_MESSAGE = <<-MSG.strip_heredoc
+        The browser returned a 'null' origin for a request with origin-based forgery protection turned on. This usually
+        means you have the 'no-referrer' Referrer-Policy header enabled, or that you the request came from a site that
+        refused to give its origin. This makes it impossible for Rails to verify the source of the requests. Likely the
+        best solution is to change your referrer policy to something less strict like same-origin or strict-same-origin.
+        If you cannot change the referrer policy, you can disable origin checking with the
+        Rails.application.config.action_controller.forgery_protection_origin_check setting.
+      MSG
+
       # Checks if the request originated from the same origin by looking at the
       # Origin header.
       def valid_request_origin? # :doc:
         if forgery_protection_origin_check
           # We accept blank origin headers because some user agents don't send it.
+          raise InvalidAuthenticityToken, NULL_ORIGIN_MESSAGE if request.origin == "null"
           request.origin.nil? || request.origin == request.base_url
         else
           true
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index ef7c4c4c16..a56ac749f8 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -335,7 +335,7 @@ module ActionController
     # the same way as <tt>Hash#each_pair</tt>.
     def each_pair(&block)
       @parameters.each_pair do |key, value|
-        yield key, convert_hashes_to_parameters(key, value)
+        yield [key, convert_hashes_to_parameters(key, value)]
       end
     end
     alias_method :each, :each_pair
diff --git a/actionpack/lib/action_controller/metal/testing.rb b/actionpack/lib/action_controller/metal/testing.rb
index b07f1f3d8c..6e8a95040f 100644
--- a/actionpack/lib/action_controller/metal/testing.rb
+++ b/actionpack/lib/action_controller/metal/testing.rb
@@ -12,11 +12,5 @@ module ActionController
         self.params = nil
       end
     end
-
-    module ClassMethods
-      def before_filters
-        _process_action_callbacks.find_all { |x| x.kind == :before }.map(&:name)
-      end
-    end
   end
 end
diff --git a/actionpack/lib/action_controller/railtie.rb b/actionpack/lib/action_controller/railtie.rb
index 769be39004..7d42f5d931 100644
--- a/actionpack/lib/action_controller/railtie.rb
+++ b/actionpack/lib/action_controller/railtie.rb
@@ -4,7 +4,7 @@ require "rails"
 require "action_controller"
 require "action_dispatch/railtie"
 require "abstract_controller/railties/routes_helpers"
-require_relative "railties/helpers"
+require "action_controller/railties/helpers"
 require "action_view/railtie"
 
 module ActionController
diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index 74d557fc18..4b408750a4 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -7,7 +7,7 @@ require "active_support/core_ext/module/anonymous"
 require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/hash/keys"
 require "active_support/testing/constant_lookup"
-require_relative "template_assertions"
+require "action_controller/template_assertions"
 require "rails-dom-testing"
 
 module ActionController
diff --git a/actionpack/lib/action_dispatch.rb b/actionpack/lib/action_dispatch.rb
index 34937f3229..6fed911d0a 100644
--- a/actionpack/lib/action_dispatch.rb
+++ b/actionpack/lib/action_dispatch.rb
@@ -42,6 +42,7 @@ module ActionDispatch
 
   eager_autoload do
     autoload_under "http" do
+      autoload :ContentSecurityPolicy
       autoload :Request
       autoload :Response
     end
diff --git a/actionpack/lib/action_dispatch/http/content_security_policy.rb b/actionpack/lib/action_dispatch/http/content_security_policy.rb
new file mode 100644
index 0000000000..4883e23d24
--- /dev/null
+++ b/actionpack/lib/action_dispatch/http/content_security_policy.rb
@@ -0,0 +1,231 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/object/deep_dup"
+
+module ActionDispatch #:nodoc:
+  class ContentSecurityPolicy
+    class Middleware
+      CONTENT_TYPE = "Content-Type".freeze
+      POLICY = "Content-Security-Policy".freeze
+      POLICY_REPORT_ONLY = "Content-Security-Policy-Report-Only".freeze
+
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        request = ActionDispatch::Request.new env
+        _, headers, _ = response = @app.call(env)
+
+        return response unless html_response?(headers)
+        return response if policy_present?(headers)
+
+        if policy = request.content_security_policy
+          headers[header_name(request)] = policy.build(request.controller_instance)
+        end
+
+        response
+      end
+
+      private
+
+        def html_response?(headers)
+          if content_type = headers[CONTENT_TYPE]
+            content_type =~ /html/
+          end
+        end
+
+        def header_name(request)
+          if request.content_security_policy_report_only
+            POLICY_REPORT_ONLY
+          else
+            POLICY
+          end
+        end
+
+        def policy_present?(headers)
+          headers[POLICY] || headers[POLICY_REPORT_ONLY]
+        end
+    end
+
+    module Request
+      POLICY = "action_dispatch.content_security_policy".freeze
+      POLICY_REPORT_ONLY = "action_dispatch.content_security_policy_report_only".freeze
+
+      def content_security_policy
+        get_header(POLICY)
+      end
+
+      def content_security_policy=(policy)
+        set_header(POLICY, policy)
+      end
+
+      def content_security_policy_report_only
+        get_header(POLICY_REPORT_ONLY)
+      end
+
+      def content_security_policy_report_only=(value)
+        set_header(POLICY_REPORT_ONLY, value)
+      end
+    end
+
+    MAPPINGS = {
+      self:           "'self'",
+      unsafe_eval:    "'unsafe-eval'",
+      unsafe_inline:  "'unsafe-inline'",
+      none:           "'none'",
+      http:           "http:",
+      https:          "https:",
+      data:           "data:",
+      mediastream:    "mediastream:",
+      blob:           "blob:",
+      filesystem:     "filesystem:",
+      report_sample:  "'report-sample'",
+      strict_dynamic: "'strict-dynamic'"
+    }.freeze
+
+    DIRECTIVES = {
+      base_uri:        "base-uri",
+      child_src:       "child-src",
+      connect_src:     "connect-src",
+      default_src:     "default-src",
+      font_src:        "font-src",
+      form_action:     "form-action",
+      frame_ancestors: "frame-ancestors",
+      frame_src:       "frame-src",
+      img_src:         "img-src",
+      manifest_src:    "manifest-src",
+      media_src:       "media-src",
+      object_src:      "object-src",
+      script_src:      "script-src",
+      style_src:       "style-src",
+      worker_src:      "worker-src"
+    }.freeze
+
+    private_constant :MAPPINGS, :DIRECTIVES
+
+    attr_reader :directives
+
+    def initialize
+      @directives = {}
+      yield self if block_given?
+    end
+
+    def initialize_copy(other)
+      @directives = other.directives.deep_dup
+    end
+
+    DIRECTIVES.each do |name, directive|
+      define_method(name) do |*sources|
+        if sources.first
+          @directives[directive] = apply_mappings(sources)
+        else
+          @directives.delete(directive)
+        end
+      end
+    end
+
+    def block_all_mixed_content(enabled = true)
+      if enabled
+        @directives["block-all-mixed-content"] = true
+      else
+        @directives.delete("block-all-mixed-content")
+      end
+    end
+
+    def plugin_types(*types)
+      if types.first
+        @directives["plugin-types"] = types
+      else
+        @directives.delete("plugin-types")
+      end
+    end
+
+    def report_uri(uri)
+      @directives["report-uri"] = [uri]
+    end
+
+    def require_sri_for(*types)
+      if types.first
+        @directives["require-sri-for"] = types
+      else
+        @directives.delete("require-sri-for")
+      end
+    end
+
+    def sandbox(*values)
+      if values.empty?
+        @directives["sandbox"] = true
+      elsif values.first
+        @directives["sandbox"] = values
+      else
+        @directives.delete("sandbox")
+      end
+    end
+
+    def upgrade_insecure_requests(enabled = true)
+      if enabled
+        @directives["upgrade-insecure-requests"] = true
+      else
+        @directives.delete("upgrade-insecure-requests")
+      end
+    end
+
+    def build(context = nil)
+      build_directives(context).compact.join("; ") + ";"
+    end
+
+    private
+      def apply_mappings(sources)
+        sources.map do |source|
+          case source
+          when Symbol
+            apply_mapping(source)
+          when String, Proc
+            source
+          else
+            raise ArgumentError, "Invalid content security policy source: #{source.inspect}"
+          end
+        end
+      end
+
+      def apply_mapping(source)
+        MAPPINGS.fetch(source) do
+          raise ArgumentError, "Unknown content security policy source mapping: #{source.inspect}"
+        end
+      end
+
+      def build_directives(context)
+        @directives.map do |directive, sources|
+          if sources.is_a?(Array)
+            "#{directive} #{build_directive(sources, context).join(' ')}"
+          elsif sources
+            directive
+          else
+            nil
+          end
+        end
+      end
+
+      def build_directive(sources, context)
+        sources.map { |source| resolve_source(source, context) }
+      end
+
+      def resolve_source(source, context)
+        case source
+        when String
+          source
+        when Symbol
+          source.to_s
+        when Proc
+          if context.nil?
+            raise RuntimeError, "Missing context for the dynamic content security policy source: #{source.inspect}"
+          else
+            context.instance_exec(&source)
+          end
+        else
+          raise RuntimeError, "Unexpected content security policy source: #{source.inspect}"
+        end
+      end
+  end
+end
diff --git a/actionpack/lib/action_dispatch/http/filter_parameters.rb b/actionpack/lib/action_dispatch/http/filter_parameters.rb
index b7141cc1b9..ec86b8bc47 100644
--- a/actionpack/lib/action_dispatch/http/filter_parameters.rb
+++ b/actionpack/lib/action_dispatch/http/filter_parameters.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "parameter_filter"
+require "action_dispatch/http/parameter_filter"
 
 module ActionDispatch
   module Http
@@ -9,7 +9,7 @@ module ActionDispatch
     # sub-hashes of the params hash to filter. Filtering only certain sub-keys
     # from a hash is possible by using the dot notation: 'credit_card.number'.
     # If a block is given, each key and value of the params hash and all
-    # sub-hashes is passed to it, the value or key can be replaced using
+    # sub-hashes is passed to it, where the value or the key can be replaced using
     # String#replace or similar method.
     #
     #   env["action_dispatch.parameter_filter"] = [:password]
@@ -48,7 +48,7 @@ module ActionDispatch
         @filtered_env ||= env_filter.filter(@env)
       end
 
-      # Reconstructed a path with all sensitive GET parameters replaced.
+      # Reconstructs a path with all sensitive GET parameters replaced.
       def filtered_path
         @filtered_path ||= query_string.empty? ? path : "#{path}?#{filtered_query_string}"
       end
diff --git a/actionpack/lib/action_dispatch/http/mime_negotiation.rb b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
index 0ca18d98a1..d7435fa8df 100644
--- a/actionpack/lib/action_dispatch/http/mime_negotiation.rb
+++ b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
@@ -12,9 +12,6 @@ module ActionDispatch
       end
 
       # The MIME type of the HTTP request, such as Mime[:xml].
-      #
-      # For backward compatibility, the post \format is extracted from the
-      # X-Post-Data-Format HTTP header if present.
       def content_mime_type
         fetch_header("action_dispatch.request.content_type") do |k|
           v = if get_header("CONTENT_TYPE") =~ /^([^,\;]*)/
diff --git a/actionpack/lib/action_dispatch/http/mime_type.rb b/actionpack/lib/action_dispatch/http/mime_type.rb
index d797e90e52..d2b2106845 100644
--- a/actionpack/lib/action_dispatch/http/mime_type.rb
+++ b/actionpack/lib/action_dispatch/http/mime_type.rb
@@ -339,4 +339,4 @@ module Mime
   end
 end
 
-require_relative "mime_types"
+require "action_dispatch/http/mime_types"
diff --git a/actionpack/lib/action_dispatch/http/mime_types.rb b/actionpack/lib/action_dispatch/http/mime_types.rb
index f8e6fca36d..342e6de312 100644
--- a/actionpack/lib/action_dispatch/http/mime_types.rb
+++ b/actionpack/lib/action_dispatch/http/mime_types.rb
@@ -10,6 +10,7 @@ Mime::Type.register "text/css", :css
 Mime::Type.register "text/calendar", :ics
 Mime::Type.register "text/csv", :csv
 Mime::Type.register "text/vcard", :vcf
+Mime::Type.register "text/vtt", :vtt, %w(vtt)
 
 Mime::Type.register "image/png", :png, [], %w(png)
 Mime::Type.register "image/jpeg", :jpeg, [], %w(jpg jpeg jpe pjpeg)
@@ -20,6 +21,18 @@ Mime::Type.register "image/svg+xml", :svg
 
 Mime::Type.register "video/mpeg", :mpeg, [], %w(mpg mpeg mpe)
 
+Mime::Type.register "audio/mpeg", :mp3, [], %w(mp1 mp2 mp3)
+Mime::Type.register "audio/ogg", :ogg, [], %w(oga ogg spx opus)
+Mime::Type.register "audio/aac", :m4a, %w( audio/mp4 ), %w(m4a mpg4 aac)
+
+Mime::Type.register "video/webm", :webm, [], %w(webm)
+Mime::Type.register "video/mp4", :mp4, [], %w(mp4 m4v)
+
+Mime::Type.register "font/otf", :otf, [], %w(otf)
+Mime::Type.register "font/ttf", :ttf, [], %w(ttf)
+Mime::Type.register "font/woff", :woff, [], %w(woff)
+Mime::Type.register "font/woff2", :woff2, [], %w(woff2)
+
 Mime::Type.register "application/xml", :xml, %w( text/xml application/x-xml )
 Mime::Type.register "application/rss+xml", :rss
 Mime::Type.register "application/atom+xml", :atom
diff --git a/actionpack/lib/action_dispatch/http/parameters.rb b/actionpack/lib/action_dispatch/http/parameters.rb
index ae875eb830..8d7431fd6b 100644
--- a/actionpack/lib/action_dispatch/http/parameters.rb
+++ b/actionpack/lib/action_dispatch/http/parameters.rb
@@ -123,9 +123,4 @@ module ActionDispatch
         end
     end
   end
-
-  module ParamsParser
-    include ActiveSupport::Deprecation::DeprecatedConstantAccessor
-    deprecate_constant "ParseError", "ActionDispatch::Http::Parameters::ParseError"
-  end
 end
diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index dee7be184a..3838b84a7a 100644
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
@@ -3,15 +3,15 @@
 require "stringio"
 
 require "active_support/inflector"
-require_relative "headers"
+require "action_dispatch/http/headers"
 require "action_controller/metal/exceptions"
 require "rack/request"
-require_relative "cache"
-require_relative "mime_negotiation"
-require_relative "parameters"
-require_relative "filter_parameters"
-require_relative "upload"
-require_relative "url"
+require "action_dispatch/http/cache"
+require "action_dispatch/http/mime_negotiation"
+require "action_dispatch/http/parameters"
+require "action_dispatch/http/filter_parameters"
+require "action_dispatch/http/upload"
+require "action_dispatch/http/url"
 require "active_support/core_ext/array/conversions"
 
 module ActionDispatch
@@ -22,6 +22,7 @@ module ActionDispatch
     include ActionDispatch::Http::Parameters
     include ActionDispatch::Http::FilterParameters
     include ActionDispatch::Http::URL
+    include ActionDispatch::ContentSecurityPolicy::Request
     include Rack::Request::Env
 
     autoload :Session, "action_dispatch/request/session"
@@ -199,6 +200,23 @@ module ActionDispatch
       @headers ||= Http::Headers.new(self)
     end
 
+    # Early Hints is an HTTP/2 status code that indicates hints to help a client start
+    # making preparations for processing the final response.
+    #
+    # If the env contains +rack.early_hints+ then the server accepts HTTP2 push for Link headers.
+    #
+    # The +send_early_hints+ method accepts a hash of links as follows:
+    #
+    #   send_early_hints("Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload")
+    #
+    # If you are using +javascript_include_tag+ or +stylesheet_link_tag+ the
+    # Early Hints headers are included by default if supported.
+    def send_early_hints(links)
+      return unless env["rack.early_hints"]
+
+      env["rack.early_hints"].call(links)
+    end
+
     # Returns a +String+ with the last requested path including their params.
     #
     #    # get '/foo'
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 0c7b153420..7e50cb6d23 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "filter_redirect"
-require_relative "cache"
+require "action_dispatch/http/filter_redirect"
+require "action_dispatch/http/cache"
 require "monitor"
 
 module ActionDispatch # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey.rb b/actionpack/lib/action_dispatch/journey.rb
index 903063d00f..2852efa6ae 100644
--- a/actionpack/lib/action_dispatch/journey.rb
+++ b/actionpack/lib/action_dispatch/journey.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "journey/router"
-require_relative "journey/gtg/builder"
-require_relative "journey/gtg/simulator"
-require_relative "journey/nfa/builder"
-require_relative "journey/nfa/simulator"
+require "action_dispatch/journey/router"
+require "action_dispatch/journey/gtg/builder"
+require "action_dispatch/journey/gtg/simulator"
+require "action_dispatch/journey/nfa/builder"
+require "action_dispatch/journey/nfa/simulator"
diff --git a/actionpack/lib/action_dispatch/journey/gtg/builder.rb b/actionpack/lib/action_dispatch/journey/gtg/builder.rb
index 7e3d957baa..44c31053cb 100644
--- a/actionpack/lib/action_dispatch/journey/gtg/builder.rb
+++ b/actionpack/lib/action_dispatch/journey/gtg/builder.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "transition_table"
+require "action_dispatch/journey/gtg/transition_table"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
index 6ed478f816..ea647e051a 100644
--- a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
+++ b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../nfa/dot"
+require "action_dispatch/journey/nfa/dot"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/nfa/builder.rb b/actionpack/lib/action_dispatch/journey/nfa/builder.rb
index 3135c05ffa..d22302e101 100644
--- a/actionpack/lib/action_dispatch/journey/nfa/builder.rb
+++ b/actionpack/lib/action_dispatch/journey/nfa/builder.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "transition_table"
-require_relative "../gtg/transition_table"
+require "action_dispatch/journey/nfa/transition_table"
+require "action_dispatch/journey/gtg/transition_table"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb b/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb
index bfd929357b..fe55861507 100644
--- a/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb
+++ b/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "dot"
+require "action_dispatch/journey/nfa/dot"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/nodes/node.rb b/actionpack/lib/action_dispatch/journey/nodes/node.rb
index 0a84f28c1a..08b931a3cd 100644
--- a/actionpack/lib/action_dispatch/journey/nodes/node.rb
+++ b/actionpack/lib/action_dispatch/journey/nodes/node.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../visitors"
+require "action_dispatch/journey/visitors"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/parser.rb b/actionpack/lib/action_dispatch/journey/parser.rb
index 6ddfe96098..e002755bcf 100644
--- a/actionpack/lib/action_dispatch/journey/parser.rb
+++ b/actionpack/lib/action_dispatch/journey/parser.rb
@@ -8,7 +8,7 @@ require 'racc/parser.rb'
 
 # :stopdoc:
 
-require_relative "parser_extras"
+require "action_dispatch/journey/parser_extras"
 module ActionDispatch
   module Journey
     class Parser < Racc::Parser
diff --git a/actionpack/lib/action_dispatch/journey/parser.y b/actionpack/lib/action_dispatch/journey/parser.y
index 850c84ea1a..f9b1a7a958 100644
--- a/actionpack/lib/action_dispatch/journey/parser.y
+++ b/actionpack/lib/action_dispatch/journey/parser.y
@@ -47,4 +47,4 @@ end
 ---- header
 # :stopdoc:
 
-require_relative "parser_extras"
+require "action_dispatch/journey/parser_extras"
diff --git a/actionpack/lib/action_dispatch/journey/parser_extras.rb b/actionpack/lib/action_dispatch/journey/parser_extras.rb
index dfbc6c4529..18ec6c9b9b 100644
--- a/actionpack/lib/action_dispatch/journey/parser_extras.rb
+++ b/actionpack/lib/action_dispatch/journey/parser_extras.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "scanner"
-require_relative "nodes/node"
+require "action_dispatch/journey/scanner"
+require "action_dispatch/journey/nodes/node"
 
 module ActionDispatch
   # :stopdoc:
diff --git a/actionpack/lib/action_dispatch/journey/router.rb b/actionpack/lib/action_dispatch/journey/router.rb
index 9987a9bfa1..30af3ff930 100644
--- a/actionpack/lib/action_dispatch/journey/router.rb
+++ b/actionpack/lib/action_dispatch/journey/router.rb
@@ -1,16 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "router/utils"
-require_relative "routes"
-require_relative "formatter"
+require "action_dispatch/journey/router/utils"
+require "action_dispatch/journey/routes"
+require "action_dispatch/journey/formatter"
 
 before = $-w
 $-w = false
-require_relative "parser"
+require "action_dispatch/journey/parser"
 $-w = before
 
-require_relative "route"
-require_relative "path/pattern"
+require "action_dispatch/journey/route"
+require "action_dispatch/journey/path/pattern"
 
 module ActionDispatch
   module Journey # :nodoc:
@@ -61,7 +61,7 @@ module ActionDispatch
           return [status, headers, body]
         end
 
-        return [404, { "X-Cascade" => "pass" }, ["Not Found"]]
+        [404, { "X-Cascade" => "pass" }, ["Not Found"]]
       end
 
       def recognize(rails_req)
diff --git a/actionpack/lib/action_dispatch/middleware/cookies.rb b/actionpack/lib/action_dispatch/middleware/cookies.rb
index 845df500d8..ea4156c972 100644
--- a/actionpack/lib/action_dispatch/middleware/cookies.rb
+++ b/actionpack/lib/action_dispatch/middleware/cookies.rb
@@ -49,6 +49,18 @@ module ActionDispatch
       get_header Cookies::AUTHENTICATED_ENCRYPTED_COOKIE_SALT
     end
 
+    def use_authenticated_cookie_encryption
+      get_header Cookies::USE_AUTHENTICATED_COOKIE_ENCRYPTION
+    end
+
+    def encrypted_cookie_cipher
+      get_header Cookies::ENCRYPTED_COOKIE_CIPHER
+    end
+
+    def signed_cookie_digest
+      get_header Cookies::SIGNED_COOKIE_DIGEST
+    end
+
     def secret_token
       get_header Cookies::SECRET_TOKEN
     end
@@ -64,6 +76,11 @@ module ActionDispatch
     def cookies_digest
       get_header Cookies::COOKIES_DIGEST
     end
+
+    def cookies_rotations
+      get_header Cookies::COOKIES_ROTATIONS
+    end
+
     # :startdoc:
   end
 
@@ -144,7 +161,7 @@ module ActionDispatch
   #
   # * <tt>:tld_length</tt> - When using <tt>:domain => :all</tt>, this option can be used to explicitly
   #   set the TLD length when using a short (<= 3 character) domain that is being interpreted as part of a TLD.
-  #   For example, to share cookies between user1.lvh.me and user2.lvh.me, set <tt>:tld_length</tt> to 1.
+  #   For example, to share cookies between user1.lvh.me and user2.lvh.me, set <tt>:tld_length</tt> to 2.
   # * <tt>:expires</tt> - The time at which this cookie expires, as a \Time or ActiveSupport::Duration object.
   # * <tt>:secure</tt> - Whether this cookie is only transmitted to HTTPS servers.
   #   Default is +false+.
@@ -157,10 +174,14 @@ module ActionDispatch
     ENCRYPTED_COOKIE_SALT = "action_dispatch.encrypted_cookie_salt".freeze
     ENCRYPTED_SIGNED_COOKIE_SALT = "action_dispatch.encrypted_signed_cookie_salt".freeze
     AUTHENTICATED_ENCRYPTED_COOKIE_SALT = "action_dispatch.authenticated_encrypted_cookie_salt".freeze
+    USE_AUTHENTICATED_COOKIE_ENCRYPTION = "action_dispatch.use_authenticated_cookie_encryption".freeze
+    ENCRYPTED_COOKIE_CIPHER = "action_dispatch.encrypted_cookie_cipher".freeze
+    SIGNED_COOKIE_DIGEST = "action_dispatch.signed_cookie_digest".freeze
     SECRET_TOKEN = "action_dispatch.secret_token".freeze
     SECRET_KEY_BASE = "action_dispatch.secret_key_base".freeze
     COOKIES_SERIALIZER = "action_dispatch.cookies_serializer".freeze
     COOKIES_DIGEST = "action_dispatch.cookies_digest".freeze
+    COOKIES_ROTATIONS = "action_dispatch.cookies_rotations".freeze
 
     # Cookies can typically store 4096 bytes.
     MAX_COOKIE_SIZE = 4096
@@ -201,12 +222,7 @@ module ActionDispatch
       #
       #   cookies.signed[:discount] # => 45
       def signed
-        @signed ||=
-          if upgrade_legacy_signed_cookies?
-            UpgradeLegacySignedCookieJar.new(self)
-          else
-            SignedCookieJar.new(self)
-          end
+        @signed ||= SignedKeyRotatingCookieJar.new(self)
       end
 
       # Returns a jar that'll automatically encrypt cookie values before sending them to the client and will decrypt them for read.
@@ -223,18 +239,11 @@ module ActionDispatch
       # Example:
       #
       #   cookies.encrypted[:discount] = 45
-      #   # => Set-Cookie: discount=ZS9ZZ1R4cG1pcUJ1bm80anhQang3dz09LS1mbDZDSU5scGdOT3ltQ2dTdlhSdWpRPT0%3D--ab54663c9f4e3bc340c790d6d2b71e92f5b60315; path=/
+      #   # => Set-Cookie: discount=DIQ7fw==--K3n//8vvnSbGq9dA--7Xh91HfLpwzbj1czhBiwOg==; path=/
       #
       #   cookies.encrypted[:discount] # => 45
       def encrypted
-        @encrypted ||=
-          if upgrade_legacy_signed_cookies?
-            UpgradeLegacyEncryptedCookieJar.new(self)
-          elsif upgrade_legacy_hmac_aes_cbc_cookies?
-            UpgradeLegacyHmacAesCbcCookieJar.new(self)
-          else
-            EncryptedCookieJar.new(self)
-          end
+        @encrypted ||= EncryptedKeyRotatingCookieJar.new(self)
       end
 
       # Returns the +signed+ or +encrypted+ jar, preferring +encrypted+ if +secret_key_base+ is set.
@@ -255,34 +264,18 @@ module ActionDispatch
         end
 
         def upgrade_legacy_hmac_aes_cbc_cookies?
-          request.secret_key_base.present?                       &&
-            request.authenticated_encrypted_cookie_salt.present? &&
-            request.encrypted_signed_cookie_salt.present?        &&
-            request.encrypted_cookie_salt.present?
+          request.secret_key_base.present? &&
+            request.encrypted_signed_cookie_salt.present? &&
+            request.encrypted_cookie_salt.present? &&
+            request.use_authenticated_cookie_encryption
         end
-    end
 
-    # Passing the ActiveSupport::MessageEncryptor::NullSerializer downstream
-    # to the Message{Encryptor,Verifier} allows us to handle the
-    # (de)serialization step within the cookie jar, which gives us the
-    # opportunity to detect and migrate legacy cookies.
-    module VerifyAndUpgradeLegacySignedMessage # :nodoc:
-      def initialize(*args)
-        super
-        @legacy_verifier = ActiveSupport::MessageVerifier.new(request.secret_token, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
-      end
-
-      def verify_and_upgrade_legacy_signed_message(name, signed_message)
-        deserialize(name, @legacy_verifier.verify(signed_message)).tap do |value|
-          self[name] = { value: value }
+        def encrypted_cookie_cipher
+          request.encrypted_cookie_cipher || "aes-256-gcm"
         end
-      rescue ActiveSupport::MessageVerifier::InvalidSignature
-        nil
-      end
 
-      private
-        def parse(name, signed_message)
-          super || verify_and_upgrade_legacy_signed_message(name, signed_message)
+        def signed_cookie_digest
+          request.signed_cookie_digest || "SHA1"
         end
     end
 
@@ -524,6 +517,7 @@ module ActionDispatch
 
     module SerializedCookieJars # :nodoc:
       MARSHAL_SIGNATURE = "\x04\x08".freeze
+      SERIALIZER = ActiveSupport::MessageEncryptor::NullSerializer
 
       protected
         def needs_migration?(value)
@@ -534,12 +528,16 @@ module ActionDispatch
           serializer.dump(value)
         end
 
-        def deserialize(name, value)
+        def deserialize(name)
+          rotate = false
+          value  = yield -> { rotate = true }
+
           if value
-            if needs_migration?(value)
-              Marshal.load(value).tap do |v|
-                self[name] = { value: v }
-              end
+            case
+            when needs_migration?(value)
+              self[name] = Marshal.load(value)
+            when rotate
+              self[name] = serializer.load(value)
             else
               serializer.load(value)
             end
@@ -561,24 +559,31 @@ module ActionDispatch
         def digest
           request.cookies_digest || "SHA1"
         end
-
-        def key_generator
-          request.key_generator
-        end
     end
 
-    class SignedCookieJar < AbstractCookieJar # :nodoc:
+    class SignedKeyRotatingCookieJar < AbstractCookieJar # :nodoc:
       include SerializedCookieJars
 
       def initialize(parent_jar)
         super
-        secret = key_generator.generate_key(request.signed_cookie_salt)
-        @verifier = ActiveSupport::MessageVerifier.new(secret, digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
+
+        secret = request.key_generator.generate_key(request.signed_cookie_salt)
+        @verifier = ActiveSupport::MessageVerifier.new(secret, digest: signed_cookie_digest, serializer: SERIALIZER)
+
+        request.cookies_rotations.signed.each do |*secrets, **options|
+          @verifier.rotate(*secrets, serializer: SERIALIZER, **options)
+        end
+
+        if upgrade_legacy_signed_cookies?
+          @verifier.rotate request.secret_token, serializer: SERIALIZER
+        end
       end
 
       private
         def parse(name, signed_message)
-          deserialize name, @verifier.verified(signed_message)
+          deserialize(name) do |rotate|
+            @verifier.verified(signed_message, on_rotation: rotate)
+          end
         end
 
         def commit(options)
@@ -588,37 +593,47 @@ module ActionDispatch
         end
     end
 
-    # UpgradeLegacySignedCookieJar is used instead of SignedCookieJar if
-    # secrets.secret_token and secret_key_base are both set. It reads
-    # legacy cookies signed with the old dummy key generator and signs and
-    # re-saves them using the new key generator to provide a smooth upgrade path.
-    class UpgradeLegacySignedCookieJar < SignedCookieJar #:nodoc:
-      include VerifyAndUpgradeLegacySignedMessage
-    end
-
-    class EncryptedCookieJar < AbstractCookieJar # :nodoc:
+    class EncryptedKeyRotatingCookieJar < AbstractCookieJar # :nodoc:
       include SerializedCookieJars
 
       def initialize(parent_jar)
         super
 
-        if ActiveSupport::LegacyKeyGenerator === key_generator
-          raise "You didn't set secret_key_base, which is required for this cookie jar. " \
-            "Read the upgrade documentation to learn more about this new config option."
+        if request.use_authenticated_cookie_encryption
+          key_len = ActiveSupport::MessageEncryptor.key_len(encrypted_cookie_cipher)
+          secret = request.key_generator.generate_key(request.authenticated_encrypted_cookie_salt, key_len)
+          @encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: encrypted_cookie_cipher, serializer: SERIALIZER)
+        else
+          key_len = ActiveSupport::MessageEncryptor.key_len("aes-256-cbc")
+          secret = request.key_generator.generate_key(request.encrypted_cookie_salt, key_len)
+          sign_secret = request.key_generator.generate_key(request.encrypted_signed_cookie_salt)
+          @encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", serializer: SERIALIZER)
+        end
+
+        request.cookies_rotations.encrypted.each do |*secrets, **options|
+          @encryptor.rotate(*secrets, serializer: SERIALIZER, **options)
         end
 
-        cipher = "aes-256-gcm"
-        key_len = ActiveSupport::MessageEncryptor.key_len(cipher)
-        secret = key_generator.generate_key(request.authenticated_encrypted_cookie_salt || "")[0, key_len]
+        if upgrade_legacy_hmac_aes_cbc_cookies?
+          legacy_cipher = "aes-256-cbc"
+          secret = request.key_generator.generate_key(request.encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len(legacy_cipher))
+          sign_secret = request.key_generator.generate_key(request.encrypted_signed_cookie_salt)
 
-        @encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
+          @encryptor.rotate(secret, sign_secret, cipher: legacy_cipher, digest: digest, serializer: SERIALIZER)
+        end
+
+        if upgrade_legacy_signed_cookies?
+          @legacy_verifier = ActiveSupport::MessageVerifier.new(request.secret_token, digest: digest, serializer: SERIALIZER)
+        end
       end
 
       private
         def parse(name, encrypted_message)
-          deserialize name, @encryptor.decrypt_and_verify(encrypted_message)
-        rescue ActiveSupport::MessageVerifier::InvalidSignature, ActiveSupport::MessageEncryptor::InvalidMessage
-          nil
+          deserialize(name) do |rotate|
+            @encryptor.decrypt_and_verify(encrypted_message, on_rotation: rotate)
+          end
+        rescue ActiveSupport::MessageEncryptor::InvalidMessage, ActiveSupport::MessageVerifier::InvalidSignature
+          parse_legacy_signed_message(name, encrypted_message)
         end
 
         def commit(options)
@@ -626,39 +641,15 @@ module ActionDispatch
 
           raise CookieOverflow if options[:value].bytesize > MAX_COOKIE_SIZE
         end
-    end
-
-    # UpgradeLegacyEncryptedCookieJar is used by ActionDispatch::Session::CookieStore
-    # instead of EncryptedCookieJar if secrets.secret_token and secret_key_base
-    # are both set. It reads legacy cookies signed with the old dummy key generator and
-    # encrypts and re-saves them using the new key generator to provide a smooth upgrade path.
-    class UpgradeLegacyEncryptedCookieJar < EncryptedCookieJar #:nodoc:
-      include VerifyAndUpgradeLegacySignedMessage
-    end
-
-    # UpgradeLegacyHmacAesCbcCookieJar is used by ActionDispatch::Session::CookieStore
-    # to upgrade cookies encrypted with AES-256-CBC with HMAC to AES-256-GCM
-    class UpgradeLegacyHmacAesCbcCookieJar < EncryptedCookieJar
-      def initialize(parent_jar)
-        super
 
-        secret = key_generator.generate_key(request.encrypted_cookie_salt || "")[0, ActiveSupport::MessageEncryptor.key_len]
-        sign_secret = key_generator.generate_key(request.encrypted_signed_cookie_salt || "")
+        def parse_legacy_signed_message(name, legacy_signed_message)
+          if defined?(@legacy_verifier)
+            deserialize(name) do |rotate|
+              rotate.call
 
-        @legacy_encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
-      end
-
-      def decrypt_and_verify_legacy_encrypted_message(name, signed_message)
-        deserialize(name, @legacy_encryptor.decrypt_and_verify(signed_message)).tap do |value|
-          self[name] = { value: value }
-        end
-      rescue ActiveSupport::MessageVerifier::InvalidSignature, ActiveSupport::MessageEncryptor::InvalidMessage
-        nil
-      end
-
-      private
-        def parse(name, signed_message)
-          super || decrypt_and_verify_legacy_encrypted_message(name, signed_message)
+              @legacy_verifier.verified(legacy_signed_message)
+            end
+          end
         end
     end
 
diff --git a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
index 3006cd97ce..511306eb0e 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../http/request"
-require_relative "exception_wrapper"
-require_relative "../routing/inspector"
+require "action_dispatch/http/request"
+require "action_dispatch/middleware/exception_wrapper"
+require "action_dispatch/routing/inspector"
 require "action_view"
 require "action_view/base"
 
diff --git a/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb b/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
index e054fefc9b..5b0be96223 100644
--- a/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
@@ -3,8 +3,8 @@
 require "rack/utils"
 require "rack/request"
 require "rack/session/abstract/id"
-require_relative "../cookies"
-require_relative "../../request/session"
+require "action_dispatch/middleware/cookies"
+require "action_dispatch/request/session"
 
 module ActionDispatch
   module Session
diff --git a/actionpack/lib/action_dispatch/middleware/session/cache_store.rb b/actionpack/lib/action_dispatch/middleware/session/cache_store.rb
index c84bc8bfad..a6d965a644 100644
--- a/actionpack/lib/action_dispatch/middleware/session/cache_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/cache_store.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "abstract_store"
+require "action_dispatch/middleware/session/abstract_store"
 
 module ActionDispatch
   module Session
diff --git a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
index b0514a96d8..4ea96196d3 100644
--- a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/hash/keys"
-require_relative "abstract_store"
+require "action_dispatch/middleware/session/abstract_store"
 require "rack/session/cookie"
 
 module ActionDispatch
diff --git a/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb b/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb
index f0aec39c9c..914df3a2b1 100644
--- a/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "abstract_store"
+require "action_dispatch/middleware/session/abstract_store"
 begin
   require "rack/session/dalli"
 rescue LoadError => e
diff --git a/actionpack/lib/action_dispatch/middleware/show_exceptions.rb b/actionpack/lib/action_dispatch/middleware/show_exceptions.rb
index d2e739d27f..3c88afd4d3 100644
--- a/actionpack/lib/action_dispatch/middleware/show_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/show_exceptions.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../http/request"
-require_relative "exception_wrapper"
+require "action_dispatch/http/request"
+require "action_dispatch/middleware/exception_wrapper"
 
 module ActionDispatch
   # This middleware rescues any exception returned by the application
diff --git a/actionpack/lib/action_dispatch/middleware/ssl.rb b/actionpack/lib/action_dispatch/middleware/ssl.rb
index 45290b6ac3..ef633aadc6 100644
--- a/actionpack/lib/action_dispatch/middleware/ssl.rb
+++ b/actionpack/lib/action_dispatch/middleware/ssl.rb
@@ -1,47 +1,52 @@
 # frozen_string_literal: true
 
 module ActionDispatch
-  # This middleware is added to the stack when `config.force_ssl = true`, and is passed
-  # the options set in `config.ssl_options`. It does three jobs to enforce secure HTTP
+  # This middleware is added to the stack when <tt>config.force_ssl = true</tt>, and is passed
+  # the options set in +config.ssl_options+. It does three jobs to enforce secure HTTP
   # requests:
   #
-  #   1. TLS redirect: Permanently redirects http:// requests to https://
-  #      with the same URL host, path, etc. Enabled by default. Set `config.ssl_options`
-  #      to modify the destination URL
-  #      (e.g. `redirect: { host: "secure.widgets.com", port: 8080 }`), or set
-  #      `redirect: false` to disable this feature.
+  # 1. <b>TLS redirect</b>: Permanently redirects +http://+ requests to +https://+
+  #    with the same URL host, path, etc. Enabled by default. Set +config.ssl_options+
+  #    to modify the destination URL
+  #    (e.g. <tt>redirect: { host: "secure.widgets.com", port: 8080 }</tt>), or set
+  #    <tt>redirect: false</tt> to disable this feature.
   #
-  #   2. Secure cookies: Sets the `secure` flag on cookies to tell browsers they
-  #      mustn't be sent along with http:// requests. Enabled by default. Set
-  #      `config.ssl_options` with `secure_cookies: false` to disable this feature.
+  #    Requests can opt-out of redirection with +exclude+:
   #
-  #   3. HTTP Strict Transport Security (HSTS): Tells the browser to remember
-  #      this site as TLS-only and automatically redirect non-TLS requests.
-  #      Enabled by default. Configure `config.ssl_options` with `hsts: false` to disable.
+  #      config.ssl_options = { redirect: { exclude: -> request { request.path =~ /healthcheck/ } } }
   #
-  # Set `config.ssl_options` with `hsts: { … }` to configure HSTS:
-  #   * `expires`: How long, in seconds, these settings will stick. The minimum
-  #     required to qualify for browser preload lists is `18.weeks`. Defaults to
-  #     `180.days` (recommended).
-  #   * `subdomains`: Set to `true` to tell the browser to apply these settings
-  #     to all subdomains. This protects your cookies from interception by a
-  #     vulnerable site on a subdomain. Defaults to `true`.
-  #   * `preload`: Advertise that this site may be included in browsers'
-  #     preloaded HSTS lists. HSTS protects your site on every visit *except the
-  #     first visit* since it hasn't seen your HSTS header yet. To close this
-  #     gap, browser vendors include a baked-in list of HSTS-enabled sites.
-  #     Go to https://hstspreload.appspot.com to submit your site for inclusion.
-  #     Defaults to `false`.
+  # 2. <b>Secure cookies</b>: Sets the +secure+ flag on cookies to tell browsers they
+  #    must not be sent along with +http://+ requests. Enabled by default. Set
+  #    +config.ssl_options+ with <tt>secure_cookies: false</tt> to disable this feature.
   #
-  # To turn off HSTS, omitting the header is not enough. Browsers will remember the
-  # original HSTS directive until it expires. Instead, use the header to tell browsers to
-  # expire HSTS immediately. Setting `hsts: false` is a shortcut for
-  # `hsts: { expires: 0 }`.
+  # 3. <b>HTTP Strict Transport Security (HSTS)</b>: Tells the browser to remember
+  #    this site as TLS-only and automatically redirect non-TLS requests.
+  #    Enabled by default. Configure +config.ssl_options+ with <tt>hsts: false</tt> to disable.
   #
-  # Requests can opt-out of redirection with `exclude`:
+  #    Set +config.ssl_options+ with <tt>hsts: { ... }</tt> to configure HSTS:
   #
-  #    config.ssl_options = { redirect: { exclude: -> request { request.path =~ /healthcheck/ } } }
+  #    * +expires+: How long, in seconds, these settings will stick. The minimum
+  #      required to qualify for browser preload lists is 18 weeks. Defaults to
+  #      180 days (recommended).
+  #
+  #    * +subdomains+: Set to +true+ to tell the browser to apply these settings
+  #      to all subdomains. This protects your cookies from interception by a
+  #      vulnerable site on a subdomain. Defaults to +true+.
+  #
+  #    * +preload+: Advertise that this site may be included in browsers'
+  #      preloaded HSTS lists. HSTS protects your site on every visit <i>except the
+  #      first visit</i> since it hasn't seen your HSTS header yet. To close this
+  #      gap, browser vendors include a baked-in list of HSTS-enabled sites.
+  #      Go to https://hstspreload.org to submit your site for inclusion.
+  #      Defaults to +false+.
+  #
+  #    To turn off HSTS, omitting the header is not enough. Browsers will remember the
+  #    original HSTS directive until it expires. Instead, use the header to tell browsers to
+  #    expire HSTS immediately. Setting <tt>hsts: false</tt> is a shortcut for
+  #    <tt>hsts: { expires: 0 }</tt>.
   class SSL
+    # :stopdoc:
+
     # Default to 180 days, the low end for https://www.ssllabs.com/ssltest/
     # and greater than the 18-week requirement for browser preload lists.
     HSTS_EXPIRES_IN = 15552000
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb
index e0509f56f4..39ea25bdfc 100644
--- a/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb
@@ -106,6 +106,7 @@
 
     .line {
       padding-left: 10px;
+      white-space: pre;
     }
 
     .line:hover {
diff --git a/actionpack/lib/action_dispatch/railtie.rb b/actionpack/lib/action_dispatch/railtie.rb
index 4743a7ce61..855f2ffa47 100644
--- a/actionpack/lib/action_dispatch/railtie.rb
+++ b/actionpack/lib/action_dispatch/railtie.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "action_dispatch"
+require "active_support/messages/rotation_configuration"
 
 module ActionDispatch
   class Railtie < Rails::Railtie # :nodoc:
@@ -18,6 +19,7 @@ module ActionDispatch
     config.action_dispatch.signed_cookie_salt = "signed cookie"
     config.action_dispatch.encrypted_cookie_salt = "encrypted cookie"
     config.action_dispatch.encrypted_signed_cookie_salt = "signed encrypted cookie"
+    config.action_dispatch.authenticated_encrypted_cookie_salt = "authenticated encrypted cookie"
     config.action_dispatch.use_authenticated_cookie_encryption = false
     config.action_dispatch.perform_deep_munge = true
 
@@ -27,6 +29,8 @@ module ActionDispatch
       "X-Content-Type-Options" => "nosniff"
     }
 
+    config.action_dispatch.cookies_rotations = ActiveSupport::Messages::RotationConfiguration.new
+
     config.eager_load_namespaces << ActionDispatch
 
     initializer "action_dispatch.configure" do |app|
@@ -39,8 +43,6 @@ module ActionDispatch
       ActionDispatch::ExceptionWrapper.rescue_responses.merge!(config.action_dispatch.rescue_responses)
       ActionDispatch::ExceptionWrapper.rescue_templates.merge!(config.action_dispatch.rescue_templates)
 
-      config.action_dispatch.authenticated_encrypted_cookie_salt = "authenticated encrypted cookie" if config.action_dispatch.use_authenticated_cookie_encryption
-
       config.action_dispatch.always_write_cookie = Rails.env.development? if config.action_dispatch.always_write_cookie.nil?
       ActionDispatch::Cookies::CookieJar.always_write_cookie = config.action_dispatch.always_write_cookie
 
diff --git a/actionpack/lib/action_dispatch/routing/endpoint.rb b/actionpack/lib/action_dispatch/routing/endpoint.rb
index e911b6537b..24dced1efd 100644
--- a/actionpack/lib/action_dispatch/routing/endpoint.rb
+++ b/actionpack/lib/action_dispatch/routing/endpoint.rb
@@ -3,10 +3,12 @@
 module ActionDispatch
   module Routing
     class Endpoint # :nodoc:
-      def dispatcher?;   false; end
-      def redirect?;     false; end
-      def matches?(req); true;  end
-      def app;           self;  end
+      def dispatcher?;                           false; end
+      def redirect?;                             false; end
+      def engine?;       rack_app.respond_to?(:routes); end
+      def matches?(req);                          true; end
+      def app;                                    self; end
+      def rack_app;                                app; end
     end
   end
 end
diff --git a/actionpack/lib/action_dispatch/routing/inspector.rb b/actionpack/lib/action_dispatch/routing/inspector.rb
index b2868b7427..a2205569b4 100644
--- a/actionpack/lib/action_dispatch/routing/inspector.rb
+++ b/actionpack/lib/action_dispatch/routing/inspector.rb
@@ -15,7 +15,7 @@ module ActionDispatch
       end
 
       def rack_app
-        app.app
+        app.rack_app
       end
 
       def path
@@ -47,7 +47,7 @@ module ActionDispatch
       end
 
       def engine?
-        rack_app.respond_to?(:routes)
+        app.engine?
       end
     end
 
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 2b43ade081..d87a23a58c 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -4,8 +4,8 @@ require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/regexp"
-require_relative "redirection"
-require_relative "endpoint"
+require "action_dispatch/routing/redirection"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -475,6 +475,16 @@ module ActionDispatch
         #
         #      resources :users, param: :name
         #
+        #   The +users+ resource here will have the following routes generated for it:
+        #
+        #      GET       /users(.:format)
+        #      POST      /users(.:format)
+        #      GET       /users/new(.:format)
+        #      GET       /users/:name/edit(.:format)
+        #      GET       /users/:name(.:format)
+        #      PATCH/PUT /users/:name(.:format)
+        #      DELETE    /users/:name(.:format)
+        #
         #   You can override <tt>ActiveRecord::Base#to_param</tt> of a related
         #   model to construct a URL:
         #
@@ -484,8 +494,8 @@ module ActionDispatch
         #        end
         #      end
         #
-        #   user = User.find_by(name: 'Phusion')
-        #   user_path(user)  # => "/users/Phusion"
+        #      user = User.find_by(name: 'Phusion')
+        #      user_path(user)  # => "/users/Phusion"
         #
         # [:path]
         #   The path prefix for the routes.
@@ -1265,7 +1275,7 @@ module ActionDispatch
         #   POST      /profile
         #
         # === Options
-        # Takes same options as +resources+.
+        # Takes same options as resources[rdoc-ref:#resources]
         def resource(*resources, &block)
           options = resources.extract_options!.dup
 
@@ -1330,7 +1340,7 @@ module ActionDispatch
         #   DELETE    /photos/:photo_id/comments/:id
         #
         # === Options
-        # Takes same options as <tt>Base#match</tt> as well as:
+        # Takes same options as match[rdoc-ref:Base#match] as well as:
         #
         # [:path_names]
         #   Allows you to change the segment component of the +edit+ and +new+ actions.
@@ -2036,7 +2046,7 @@ module ActionDispatch
       end
 
       module CustomUrls
-        # Define custom url helpers that will be added to the application's
+        # Define custom URL helpers that will be added to the application's
         # routes. This allows you to override and/or replace the default behavior
         # of routing helpers, e.g:
         #
@@ -2056,11 +2066,11 @@ module ActionDispatch
         # arguments for +url_for+ which will actually build the URL string. This can
         # be one of the following:
         #
-        #   * A string, which is treated as a generated URL
-        #   * A hash, e.g. { controller: "pages", action: "index" }
-        #   * An array, which is passed to `polymorphic_url`
-        #   * An Active Model instance
-        #   * An Active Model class
+        # * A string, which is treated as a generated URL
+        # * A hash, e.g. <tt>{ controller: "pages", action: "index" }</tt>
+        # * An array, which is passed to +polymorphic_url+
+        # * An Active Model instance
+        # * An Active Model class
         #
         # NOTE: Other URL helpers can be called in the block but be careful not to invoke
         # your custom URL helper again otherwise it will result in a stack overflow error.
diff --git a/actionpack/lib/action_dispatch/routing/redirection.rb b/actionpack/lib/action_dispatch/routing/redirection.rb
index 2e2bc87b57..143a4b3d62 100644
--- a/actionpack/lib/action_dispatch/routing/redirection.rb
+++ b/actionpack/lib/action_dispatch/routing/redirection.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "../http/request"
+require "action_dispatch/http/request"
 require "active_support/core_ext/uri"
 require "active_support/core_ext/array/extract_options"
 require "rack/utils"
 require "action_controller/metal/exceptions"
-require_relative "endpoint"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 445e86b13c..9eff30fa53 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -1,14 +1,14 @@
 # frozen_string_literal: true
 
-require_relative "../journey"
+require "action_dispatch/journey"
 require "active_support/core_ext/object/to_query"
 require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/module/remove_method"
 require "active_support/core_ext/array/extract_options"
 require "action_controller/metal/exceptions"
-require_relative "../http/request"
-require_relative "endpoint"
+require "action_dispatch/http/request"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -199,6 +199,16 @@ module ActionDispatch
               if args.size == arg_size && !inner_options && optimize_routes_generation?(t)
                 options = t.url_options.merge @options
                 options[:path] = optimized_helper(args)
+
+                original_script_name = options.delete(:original_script_name)
+                script_name = t._routes.find_script_name(options)
+
+                if original_script_name
+                  script_name = original_script_name + script_name
+                end
+
+                options[:script_name] = script_name
+
                 url_strategy.call options
               else
                 super
@@ -584,14 +594,14 @@ module ActionDispatch
         if route.segment_keys.include?(:controller)
           ActiveSupport::Deprecation.warn(<<-MSG.squish)
             Using a dynamic :controller segment in a route is deprecated and
-            will be removed in Rails 5.2.
+            will be removed in Rails 6.0.
           MSG
         end
 
         if route.segment_keys.include?(:action)
           ActiveSupport::Deprecation.warn(<<-MSG.squish)
             Using a dynamic :action segment in a route is deprecated and
-            will be removed in Rails 5.2.
+            will be removed in Rails 6.0.
           MSG
         end
 
@@ -842,6 +852,10 @@ module ActionDispatch
         end
 
         req = make_request(env)
+        recognize_path_with_request(req, path, extras)
+      end
+
+      def recognize_path_with_request(req, path, extras)
         @router.recognize(req) do |route, params|
           params.merge!(extras)
           params.each do |key, value|
@@ -860,6 +874,9 @@ module ActionDispatch
             end
 
             return req.path_parameters
+          elsif app.matches?(req) && app.engine?
+            path_parameters = app.rack_app.routes.recognize_path_with_request(req, path, extras)
+            return path_parameters
           end
         end
 
diff --git a/actionpack/lib/action_dispatch/routing/url_for.rb b/actionpack/lib/action_dispatch/routing/url_for.rb
index 3ae533dd37..fa345dccdf 100644
--- a/actionpack/lib/action_dispatch/routing/url_for.rb
+++ b/actionpack/lib/action_dispatch/routing/url_for.rb
@@ -155,7 +155,7 @@ module ActionDispatch
       # Missing routes keys may be filled in from the current request's parameters
       # (e.g. +:controller+, +:action+, +:id+ and any other parameters that are
       # placed in the path). Given that the current action has been reached
-      # through `GET /users/1`:
+      # through <tt>GET /users/1</tt>:
       #
       #   url_for(only_path: true)                        # => '/users/1'
       #   url_for(only_path: true, action: 'edit')        # => '/users/1/edit'
diff --git a/actionpack/lib/action_dispatch/system_test_case.rb b/actionpack/lib/action_dispatch/system_test_case.rb
index ae4aeac59d..99d0c06751 100644
--- a/actionpack/lib/action_dispatch/system_test_case.rb
+++ b/actionpack/lib/action_dispatch/system_test_case.rb
@@ -1,13 +1,15 @@
 # frozen_string_literal: true
 
+gem "capybara", "~> 2.15"
+
 require "capybara/dsl"
 require "capybara/minitest"
 require "action_controller"
-require_relative "system_testing/driver"
-require_relative "system_testing/server"
-require_relative "system_testing/test_helpers/screenshot_helper"
-require_relative "system_testing/test_helpers/setup_and_teardown"
-require_relative "system_testing/test_helpers/undef_methods"
+require "action_dispatch/system_testing/driver"
+require "action_dispatch/system_testing/server"
+require "action_dispatch/system_testing/test_helpers/screenshot_helper"
+require "action_dispatch/system_testing/test_helpers/setup_and_teardown"
+require "action_dispatch/system_testing/test_helpers/undef_methods"
 
 module ActionDispatch
   # = System Testing
@@ -119,14 +121,22 @@ module ActionDispatch
     #
     #   driven_by :poltergeist
     #
+    #   driven_by :selenium, screen_size: [800, 800]
+    #
+    #   driven_by :selenium, using: :chrome
+    #
+    #   driven_by :selenium, using: :headless_chrome
+    #
     #   driven_by :selenium, using: :firefox
     #
-    #   driven_by :selenium, screen_size: [800, 800]
+    #   driven_by :selenium, using: :headless_firefox
     def self.driven_by(driver, using: :chrome, screen_size: [1400, 1400], options: {})
       self.driver = SystemTesting::Driver.new(driver, using: using, screen_size: screen_size, options: options)
     end
 
     driven_by :selenium
+
+    ActiveSupport.run_load_hooks(:action_dispatch_system_test_case, self)
   end
 
   SystemTestCase.start_application
diff --git a/actionpack/lib/action_dispatch/system_testing/driver.rb b/actionpack/lib/action_dispatch/system_testing/driver.rb
index 4279336f2f..280989a146 100644
--- a/actionpack/lib/action_dispatch/system_testing/driver.rb
+++ b/actionpack/lib/action_dispatch/system_testing/driver.rb
@@ -31,8 +31,35 @@ module ActionDispatch
           end
         end
 
+        def browser_options
+          if @browser == :headless_chrome
+            browser_options = Selenium::WebDriver::Chrome::Options.new
+            browser_options.args << "--headless"
+            browser_options.args << "--disable-gpu"
+
+            @options.merge(options: browser_options)
+          elsif @browser == :headless_firefox
+            browser_options = Selenium::WebDriver::Firefox::Options.new
+            browser_options.args << "-headless"
+
+            @options.merge(options: browser_options)
+          else
+            @options
+          end
+        end
+
+        def browser
+          if @browser == :headless_chrome
+            :chrome
+          elsif @browser == :headless_firefox
+            :firefox
+          else
+            @browser
+          end
+        end
+
         def register_selenium(app)
-          Capybara::Selenium::Driver.new(app, { browser: @browser }.merge(@options)).tap do |driver|
+          Capybara::Selenium::Driver.new(app, { browser: browser }.merge(browser_options)).tap do |driver|
             driver.browser.manage.window.size = Selenium::WebDriver::Dimension.new(*@screen_size)
           end
         end
@@ -43,7 +70,7 @@ module ActionDispatch
 
         def register_webkit(app)
           Capybara::Webkit::Driver.new(app, Capybara::Webkit::Configuration.to_hash.merge(@options)).tap do |driver|
-            driver.resize_window(*@screen_size)
+            driver.resize_window_to(driver.current_window_handle, *@screen_size)
           end
         end
 
diff --git a/actionpack/lib/action_dispatch/system_testing/server.rb b/actionpack/lib/action_dispatch/system_testing/server.rb
index 76bada8df1..8f1b6725b1 100644
--- a/actionpack/lib/action_dispatch/system_testing/server.rb
+++ b/actionpack/lib/action_dispatch/system_testing/server.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "rack/handler/puma"
-
 module ActionDispatch
   module SystemTesting
     class Server # :nodoc:
@@ -12,29 +10,17 @@ module ActionDispatch
       self.silence_puma = false
 
       def run
-        register
         setup
       end
 
       private
-        def register
-          Capybara.register_server :rails_puma do |app, port, host|
-            Rack::Handler::Puma.run(
-              app,
-              Port: port,
-              Threads: "0:1",
-              Silent: self.class.silence_puma
-            )
-          end
-        end
-
         def setup
           set_server
           set_port
         end
 
         def set_server
-          Capybara.server = :rails_puma
+          Capybara.server = :puma, { Silent: self.class.silence_puma }
         end
 
         def set_port
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
index 6c337cdc31..df0c5d3f0e 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
@@ -15,12 +15,11 @@ module ActionDispatch
         #
         # You can set the +RAILS_SYSTEM_TESTING_SCREENSHOT+ environment variable to
         # control the output. Possible values are:
-        # * [+inline+ (default)]    display the screenshot in the terminal using the
+        # * [+simple+ (default)]    Only displays the screenshot path.
+        #                           This is the default value.
+        # * [+inline+]              Display the screenshot in the terminal using the
         #                           iTerm image protocol (https://iterm2.com/documentation-images.html).
-        # * [+simple+]              only display the screenshot path.
-        #                           This is the default value if the +CI+ environment variables
-        #                           is defined.
-        # * [+artifact+]            display the screenshot in the terminal, using the terminal
+        # * [+artifact+]            Display the screenshot in the terminal, using the terminal
         #                           artifact format (https://buildkite.github.io/terminal/inline-images/).
         def take_screenshot
           save_image
@@ -59,11 +58,8 @@ module ActionDispatch
             # Environment variables have priority
             output_type = ENV["RAILS_SYSTEM_TESTING_SCREENSHOT"] || ENV["CAPYBARA_INLINE_SCREENSHOT"]
 
-            # If running in a CI environment, default to simple
-            output_type ||= "simple" if ENV["CI"]
-
-            # Default
-            output_type ||= "inline"
+            # Default to outputting a path to the screenshot
+            output_type ||= "simple"
 
             output_type
           end
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb
index ef680cafed..d64be3b3d9 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb
@@ -14,7 +14,7 @@ module ActionDispatch
 
           def method_missing(method, *args, &block)
             if METHODS.include?(method)
-              raise NoMethodError
+              raise NoMethodError, "System tests cannot make direct requests via ##{method}; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information."
             else
               super
             end
diff --git a/actionpack/lib/action_dispatch/testing/integration.rb b/actionpack/lib/action_dispatch/testing/integration.rb
index ae1f368e8b..7171b6942c 100644
--- a/actionpack/lib/action_dispatch/testing/integration.rb
+++ b/actionpack/lib/action_dispatch/testing/integration.rb
@@ -7,43 +7,43 @@ require "active_support/core_ext/object/try"
 require "rack/test"
 require "minitest"
 
-require_relative "request_encoder"
+require "action_dispatch/testing/request_encoder"
 
 module ActionDispatch
   module Integration #:nodoc:
     module RequestHelpers
-      # Performs a GET request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a GET request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def get(path, **args)
         process(:get, path, **args)
       end
 
-      # Performs a POST request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a POST request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def post(path, **args)
         process(:post, path, **args)
       end
 
-      # Performs a PATCH request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a PATCH request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def patch(path, **args)
         process(:patch, path, **args)
       end
 
-      # Performs a PUT request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a PUT request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def put(path, **args)
         process(:put, path, **args)
       end
 
-      # Performs a DELETE request with the given parameters. See +#process+ for
-      # more details.
+      # Performs a DELETE request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def delete(path, **args)
         process(:delete, path, **args)
       end
 
-      # Performs a HEAD request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a HEAD request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def head(path, *args)
         process(:head, path, *args)
       end
diff --git a/actionpack/lib/action_dispatch/testing/test_process.rb b/actionpack/lib/action_dispatch/testing/test_process.rb
index 3b63706aaa..8ac50c730d 100644
--- a/actionpack/lib/action_dispatch/testing/test_process.rb
+++ b/actionpack/lib/action_dispatch/testing/test_process.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../middleware/cookies"
-require_relative "../middleware/flash"
+require "action_dispatch/middleware/cookies"
+require "action_dispatch/middleware/flash"
 
 module ActionDispatch
   module TestProcess
diff --git a/actionpack/lib/action_dispatch/testing/test_response.rb b/actionpack/lib/action_dispatch/testing/test_response.rb
index b23ea7479c..1e6b21f235 100644
--- a/actionpack/lib/action_dispatch/testing/test_response.rb
+++ b/actionpack/lib/action_dispatch/testing/test_response.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "request_encoder"
+require "action_dispatch/testing/request_encoder"
 
 module ActionDispatch
   # Integration test methods such as ActionDispatch::Integration::Session#get
diff --git a/actionpack/lib/action_pack.rb b/actionpack/lib/action_pack.rb
index fe2fc7c474..95fdd3affb 100644
--- a/actionpack/lib/action_pack.rb
+++ b/actionpack/lib/action_pack.rb
@@ -23,4 +23,4 @@
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #++
 
-require_relative "action_pack/version"
+require "action_pack/version"
diff --git a/actionpack/lib/action_pack/gem_version.rb b/actionpack/lib/action_pack/gem_version.rb
index 28bc153f4d..97f4934b58 100644
--- a/actionpack/lib/action_pack/gem_version.rb
+++ b/actionpack/lib/action_pack/gem_version.rb
@@ -10,7 +10,7 @@ module ActionPack
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionpack/test/abstract_unit.rb b/actionpack/test/abstract_unit.rb
index caa56018f8..55ad9c245e 100644
--- a/actionpack/test/abstract_unit.rb
+++ b/actionpack/test/abstract_unit.rb
@@ -44,7 +44,7 @@ module Rails
       @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "test")
     end
 
-    def root; end;
+    def root; end
   end
 end
 
@@ -449,3 +449,11 @@ end
 class DrivenBySeleniumWithChrome < ActionDispatch::SystemTestCase
   driven_by :selenium, using: :chrome
 end
+
+class DrivenBySeleniumWithHeadlessChrome < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :headless_chrome
+end
+
+class DrivenBySeleniumWithHeadlessFirefox < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :headless_firefox
+end
diff --git a/actionpack/test/controller/caching_test.rb b/actionpack/test/controller/caching_test.rb
index e0300539c9..3557f9f888 100644
--- a/actionpack/test/controller/caching_test.rb
+++ b/actionpack/test/controller/caching_test.rb
@@ -317,7 +317,7 @@ end
 class CacheHelperOutputBufferTest < ActionController::TestCase
   class MockController
     def read_fragment(name, options)
-      return false
+      false
     end
 
     def write_fragment(name, fragment, options)
@@ -333,9 +333,9 @@ class CacheHelperOutputBufferTest < ActionController::TestCase
     output_buffer = ActionView::OutputBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
@@ -354,9 +354,9 @@ class CacheHelperOutputBufferTest < ActionController::TestCase
     output_buffer = ActiveSupport::SafeBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
diff --git a/actionpack/test/controller/flash_test.rb b/actionpack/test/controller/flash_test.rb
index d92ae0b817..34bc2c0caa 100644
--- a/actionpack/test/controller/flash_test.rb
+++ b/actionpack/test/controller/flash_test.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
-require "active_support/key_generator"
+require "active_support/messages/rotation_configuration"
 
 class FlashTest < ActionController::TestCase
   class TestController < ActionController::Base
@@ -243,6 +243,7 @@ end
 class FlashIntegrationTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   Generator  = ActiveSupport::LegacyKeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33")
+  Rotations  = ActiveSupport::Messages::RotationConfiguration.new
 
   class TestController < ActionController::Base
     add_flash_types :bar
@@ -348,6 +349,7 @@ class FlashIntegrationTest < ActionDispatch::IntegrationTest
       args[0] ||= {}
       args[0][:env] ||= {}
       args[0][:env]["action_dispatch.key_generator"] ||= Generator
+      args[0][:env]["action_dispatch.cookies_rotations"] = Rotations
       super(path, *args)
     end
 
diff --git a/actionpack/test/controller/log_subscriber_test.rb b/actionpack/test/controller/log_subscriber_test.rb
index f0f106c8ba..be455642de 100644
--- a/actionpack/test/controller/log_subscriber_test.rb
+++ b/actionpack/test/controller/log_subscriber_test.rb
@@ -98,7 +98,7 @@ class ACLogSubscriberTest < ActionController::TestCase
 
     @old_logger = ActionController::Base.logger
 
-    @cache_path = File.join Dir.tmpdir, Dir::Tmpname.make_tmpname("tmp", "cache")
+    @cache_path = Dir.mktmpdir(%w[tmp cache])
     @controller.cache_store = :file_store, @cache_path
     ActionController::LogSubscriber.attach_to :action_controller
   end
diff --git a/actionpack/test/controller/new_base/base_test.rb b/actionpack/test/controller/new_base/base_test.rb
index d9f200b2a7..280134f8d2 100644
--- a/actionpack/test/controller/new_base/base_test.rb
+++ b/actionpack/test/controller/new_base/base_test.rb
@@ -47,7 +47,6 @@ module Dispatching
   end
 
   class BaseTest < Rack::TestCase
-    # :api: plugin
     test "simple dispatching" do
       get "/dispatching/simple/index"
 
@@ -56,14 +55,12 @@ module Dispatching
       assert_content_type "text/plain; charset=utf-8"
     end
 
-    # :api: plugin
     test "directly modifying response body" do
       get "/dispatching/simple/modify_response_body"
 
       assert_body "success"
     end
 
-    # :api: plugin
     test "directly modifying response body twice" do
       get "/dispatching/simple/modify_response_body_twice"
 
diff --git a/actionpack/test/controller/parameters/accessors_test.rb b/actionpack/test/controller/parameters/accessors_test.rb
index 43cabae7d2..154430d4b0 100644
--- a/actionpack/test/controller/parameters/accessors_test.rb
+++ b/actionpack/test/controller/parameters/accessors_test.rb
@@ -51,6 +51,14 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     @params.each { |key, value| assert_not(value.permitted?) if key == "person" }
   end
 
+  test "each returns key,value array for block with arity 1" do
+    @params.each do |arg|
+      assert_kind_of Array, arg
+      assert_equal "person", arg[0]
+      assert_kind_of ActionController::Parameters, arg[1]
+    end
+  end
+
   test "each_pair carries permitted status" do
     @params.permit!
     @params.each_pair { |key, value| assert(value.permitted?) if key == "person" }
@@ -60,6 +68,14 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     @params.each_pair { |key, value| assert_not(value.permitted?) if key == "person" }
   end
 
+  test "each_pair returns key,value array for block with arity 1" do
+    @params.each_pair do |arg|
+      assert_kind_of Array, arg
+      assert_equal "person", arg[0]
+      assert_kind_of ActionController::Parameters, arg[1]
+    end
+  end
+
   test "empty? returns true when params contains no key/value pairs" do
     params = ActionController::Parameters.new
     assert params.empty?
diff --git a/actionpack/test/controller/params_wrapper_test.rb b/actionpack/test/controller/params_wrapper_test.rb
index df68ef25a3..c4c74e8f2b 100644
--- a/actionpack/test/controller/params_wrapper_test.rb
+++ b/actionpack/test/controller/params_wrapper_test.rb
@@ -255,6 +255,20 @@ class ParamsWrapperTest < ActionController::TestCase
       assert_equal "", @response.body
     end
   end
+
+  def test_derived_wrapped_keys_from_nested_attributes
+    def User.nested_attributes_options
+      { person: {} }
+    end
+
+    assert_called(User, :attribute_names, times: 2, returns: ["username"]) do
+      with_default_wrapper_options do
+        @request.env["CONTENT_TYPE"] = "application/json"
+        post :parse, params: { "username" => "sikachu", "person_attributes" => { "title" => "Developer" } }
+        assert_parameters("username" => "sikachu", "person_attributes" => { "title" => "Developer" }, "user" => { "username" => "sikachu", "person_attributes" => { "title" => "Developer" } })
+      end
+    end
+  end
 end
 
 class NamespacedParamsWrapperTest < ActionController::TestCase
@@ -262,7 +276,7 @@ class NamespacedParamsWrapperTest < ActionController::TestCase
 
   module Admin
     module Users
-      class UsersController < ActionController::Base;
+      class UsersController < ActionController::Base
         class << self
           attr_accessor :last_parameters
         end
diff --git a/actionpack/test/controller/redirect_test.rb b/actionpack/test/controller/redirect_test.rb
index e447b66486..2959dc3e4d 100644
--- a/actionpack/test/controller/redirect_test.rb
+++ b/actionpack/test/controller/redirect_test.rb
@@ -62,6 +62,10 @@ class RedirectController < ActionController::Base
     redirect_back(fallback_location: "/things/stuff", status: 307)
   end
 
+  def safe_redirect_back_with_status
+    redirect_back(fallback_location: "/things/stuff", status: 307, allow_other_host: false)
+  end
+
   def host_redirect
     redirect_to action: "other_host", only_path: false, host: "other.test.host"
   end
@@ -259,6 +263,23 @@ class RedirectTest < ActionController::TestCase
     assert_equal "http://test.host/things/stuff", redirect_to_url
   end
 
+  def test_safe_redirect_back_from_other_host
+    @request.env["HTTP_REFERER"] = "http://another.host/coming/from"
+    get :safe_redirect_back_with_status
+
+    assert_response 307
+    assert_equal "http://test.host/things/stuff", redirect_to_url
+  end
+
+  def test_safe_redirect_back_from_the_same_host
+    referer = "http://test.host/coming/from"
+    @request.env["HTTP_REFERER"] = referer
+    get :safe_redirect_back_with_status
+
+    assert_response 307
+    assert_equal referer, redirect_to_url
+  end
+
   def test_redirect_to_record
     with_routing do |set|
       set.draw do
diff --git a/actionpack/test/controller/request_forgery_protection_test.rb b/actionpack/test/controller/request_forgery_protection_test.rb
index 12ae95d602..4822d85bcb 100644
--- a/actionpack/test/controller/request_forgery_protection_test.rb
+++ b/actionpack/test/controller/request_forgery_protection_test.rb
@@ -2,6 +2,7 @@
 
 require "abstract_unit"
 require "active_support/log_subscriber/test_helper"
+require "active_support/messages/rotation_configuration"
 
 # common controller actions
 module RequestForgeryProtectionActions
@@ -445,6 +446,19 @@ module RequestForgeryProtectionTests
     end
   end
 
+  def test_should_raise_for_post_with_null_origin
+    forgery_protection_origin_check do
+      session[:_csrf_token] = @token
+      @controller.stub :form_authenticity_token, @token do
+        exception = assert_raises(ActionController::InvalidAuthenticityToken) do
+          @request.set_header "HTTP_ORIGIN", "null"
+          post :index, params: { custom_authenticity_token: @token }
+        end
+        assert_match "The browser returned a 'null' origin for a request", exception.message
+      end
+    end
+  end
+
   def test_should_block_post_with_origin_checking_and_wrong_origin
     old_logger = ActionController::Base.logger
     logger = ActiveSupport::LogSubscriber::TestHelper::MockLogger.new
@@ -630,13 +644,14 @@ end
 
 class RequestForgeryProtectionControllerUsingNullSessionTest < ActionController::TestCase
   class NullSessionDummyKeyGenerator
-    def generate_key(secret)
+    def generate_key(secret, length = nil)
       "03312270731a2ed0d11ed091c2338a06"
     end
   end
 
   def setup
     @request.env[ActionDispatch::Cookies::GENERATOR_KEY] = NullSessionDummyKeyGenerator.new
+    @request.env[ActionDispatch::Cookies::COOKIES_ROTATIONS] = ActiveSupport::Messages::RotationConfiguration.new
   end
 
   test "should allow to set signed cookies" do
diff --git a/actionpack/test/controller/routing_test.rb b/actionpack/test/controller/routing_test.rb
index f09051b306..71b01c36a7 100644
--- a/actionpack/test/controller/routing_test.rb
+++ b/actionpack/test/controller/routing_test.rb
@@ -213,7 +213,7 @@ class LegacyRouteSetTests < ActiveSupport::TestCase
     assert_equal expected, ActiveSupport::JSON.decode(get(u))
   end
 
-  def test_regexp_precidence
+  def test_regexp_precedence
     rs.draw do
       get "/whois/:domain", constraints: {
         domain: /\w+\.[\w\.]+/ },
diff --git a/actionpack/test/controller/send_file_test.rb b/actionpack/test/controller/send_file_test.rb
index fd2399e433..7b1a52b277 100644
--- a/actionpack/test/controller/send_file_test.rb
+++ b/actionpack/test/controller/send_file_test.rb
@@ -178,7 +178,7 @@ class SendFileTest < ActionController::TestCase
       "image.jpg" => "image/jpeg",
       "image.tif" => "image/tiff",
       "image.gif" => "image/gif",
-      "movie.mpg" => "video/mpeg",
+      "movie.mp4" => "video/mp4",
       "file.zip" => "application/zip",
       "file.unk" => "application/octet-stream",
       "zip" => "application/octet-stream"
diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index 46369ebbb0..536c5ed97a 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -6,7 +6,7 @@ require "active_support/json/decoding"
 require "rails/engine"
 
 class TestCaseTest < ActionController::TestCase
-  def self.fixture_path; end;
+  def self.fixture_path; end
 
   class TestController < ActionController::Base
     def no_op
diff --git a/actionpack/test/dispatch/content_security_policy_test.rb b/actionpack/test/dispatch/content_security_policy_test.rb
new file mode 100644
index 0000000000..7c4a65a633
--- /dev/null
+++ b/actionpack/test/dispatch/content_security_policy_test.rb
@@ -0,0 +1,368 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class ContentSecurityPolicyTest < ActiveSupport::TestCase
+  def setup
+    @policy = ActionDispatch::ContentSecurityPolicy.new
+  end
+
+  def test_build
+    assert_equal ";", @policy.build
+
+    @policy.script_src :self
+    assert_equal "script-src 'self';", @policy.build
+  end
+
+  def test_dup
+    @policy.img_src :self
+    @policy.block_all_mixed_content
+    @policy.upgrade_insecure_requests
+    @policy.sandbox
+    copied = @policy.dup
+    assert_equal copied.build, @policy.build
+  end
+
+  def test_mappings
+    @policy.script_src :data
+    assert_equal "script-src data:;", @policy.build
+
+    @policy.script_src :mediastream
+    assert_equal "script-src mediastream:;", @policy.build
+
+    @policy.script_src :blob
+    assert_equal "script-src blob:;", @policy.build
+
+    @policy.script_src :filesystem
+    assert_equal "script-src filesystem:;", @policy.build
+
+    @policy.script_src :self
+    assert_equal "script-src 'self';", @policy.build
+
+    @policy.script_src :unsafe_inline
+    assert_equal "script-src 'unsafe-inline';", @policy.build
+
+    @policy.script_src :unsafe_eval
+    assert_equal "script-src 'unsafe-eval';", @policy.build
+
+    @policy.script_src :none
+    assert_equal "script-src 'none';", @policy.build
+
+    @policy.script_src :strict_dynamic
+    assert_equal "script-src 'strict-dynamic';", @policy.build
+
+    @policy.script_src :none, :report_sample
+    assert_equal "script-src 'none' 'report-sample';", @policy.build
+  end
+
+  def test_fetch_directives
+    @policy.child_src :self
+    assert_match %r{child-src 'self'}, @policy.build
+
+    @policy.child_src false
+    assert_no_match %r{child-src}, @policy.build
+
+    @policy.connect_src :self
+    assert_match %r{connect-src 'self'}, @policy.build
+
+    @policy.connect_src false
+    assert_no_match %r{connect-src}, @policy.build
+
+    @policy.default_src :self
+    assert_match %r{default-src 'self'}, @policy.build
+
+    @policy.default_src false
+    assert_no_match %r{default-src}, @policy.build
+
+    @policy.font_src :self
+    assert_match %r{font-src 'self'}, @policy.build
+
+    @policy.font_src false
+    assert_no_match %r{font-src}, @policy.build
+
+    @policy.frame_src :self
+    assert_match %r{frame-src 'self'}, @policy.build
+
+    @policy.frame_src false
+    assert_no_match %r{frame-src}, @policy.build
+
+    @policy.img_src :self
+    assert_match %r{img-src 'self'}, @policy.build
+
+    @policy.img_src false
+    assert_no_match %r{img-src}, @policy.build
+
+    @policy.manifest_src :self
+    assert_match %r{manifest-src 'self'}, @policy.build
+
+    @policy.manifest_src false
+    assert_no_match %r{manifest-src}, @policy.build
+
+    @policy.media_src :self
+    assert_match %r{media-src 'self'}, @policy.build
+
+    @policy.media_src false
+    assert_no_match %r{media-src}, @policy.build
+
+    @policy.object_src :self
+    assert_match %r{object-src 'self'}, @policy.build
+
+    @policy.object_src false
+    assert_no_match %r{object-src}, @policy.build
+
+    @policy.script_src :self
+    assert_match %r{script-src 'self'}, @policy.build
+
+    @policy.script_src false
+    assert_no_match %r{script-src}, @policy.build
+
+    @policy.style_src :self
+    assert_match %r{style-src 'self'}, @policy.build
+
+    @policy.style_src false
+    assert_no_match %r{style-src}, @policy.build
+
+    @policy.worker_src :self
+    assert_match %r{worker-src 'self'}, @policy.build
+
+    @policy.worker_src false
+    assert_no_match %r{worker-src}, @policy.build
+  end
+
+  def test_document_directives
+    @policy.base_uri "https://example.com"
+    assert_match %r{base-uri https://example\.com;}, @policy.build
+
+    @policy.plugin_types "application/x-shockwave-flash"
+    assert_match %r{plugin-types application/x-shockwave-flash;}, @policy.build
+
+    @policy.sandbox
+    assert_match %r{sandbox;}, @policy.build
+
+    @policy.sandbox "allow-scripts", "allow-modals"
+    assert_match %r{sandbox allow-scripts allow-modals;}, @policy.build
+
+    @policy.sandbox false
+    assert_no_match %r{sandbox}, @policy.build
+  end
+
+  def test_navigation_directives
+    @policy.form_action :self
+    assert_match %r{form-action 'self';}, @policy.build
+
+    @policy.frame_ancestors :self
+    assert_match %r{frame-ancestors 'self';}, @policy.build
+  end
+
+  def test_reporting_directives
+    @policy.report_uri "/violations"
+    assert_match %r{report-uri /violations;}, @policy.build
+  end
+
+  def test_other_directives
+    @policy.block_all_mixed_content
+    assert_match %r{block-all-mixed-content;}, @policy.build
+
+    @policy.block_all_mixed_content false
+    assert_no_match %r{block-all-mixed-content}, @policy.build
+
+    @policy.require_sri_for :script, :style
+    assert_match %r{require-sri-for script style;}, @policy.build
+
+    @policy.require_sri_for "script", "style"
+    assert_match %r{require-sri-for script style;}, @policy.build
+
+    @policy.require_sri_for
+    assert_no_match %r{require-sri-for}, @policy.build
+
+    @policy.upgrade_insecure_requests
+    assert_match %r{upgrade-insecure-requests;}, @policy.build
+
+    @policy.upgrade_insecure_requests false
+    assert_no_match %r{upgrade-insecure-requests}, @policy.build
+  end
+
+  def test_multiple_sources
+    @policy.script_src :self, :https
+    assert_equal "script-src 'self' https:;", @policy.build
+  end
+
+  def test_multiple_directives
+    @policy.script_src :self, :https
+    @policy.style_src :self, :https
+    assert_equal "script-src 'self' https:; style-src 'self' https:;", @policy.build
+  end
+
+  def test_dynamic_directives
+    request = Struct.new(:host).new("www.example.com")
+    controller = Struct.new(:request).new(request)
+
+    @policy.script_src -> { request.host }
+    assert_equal "script-src www.example.com;", @policy.build(controller)
+  end
+
+  def test_mixed_static_and_dynamic_directives
+    @policy.script_src :self, -> { "foo.com" }, "bar.com"
+    assert_equal "script-src 'self' foo.com bar.com;", @policy.build(Object.new)
+  end
+
+  def test_invalid_directive_source
+    exception = assert_raises(ArgumentError) do
+      @policy.script_src [:self]
+    end
+
+    assert_equal "Invalid content security policy source: [:self]", exception.message
+  end
+
+  def test_missing_context_for_dynamic_source
+    @policy.script_src -> { request.host }
+
+    exception = assert_raises(RuntimeError) do
+      @policy.build
+    end
+
+    assert_match %r{\AMissing context for the dynamic content security policy source:}, exception.message
+  end
+
+  def test_raises_runtime_error_when_unexpected_source
+    @policy.plugin_types [:flash]
+
+    exception = assert_raises(RuntimeError) do
+      @policy.build
+    end
+
+    assert_match %r{\AUnexpected content security policy source:}, exception.message
+  end
+end
+
+class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
+  class PolicyController < ActionController::Base
+    content_security_policy only: :inline do |p|
+      p.default_src "https://example.com"
+    end
+
+    content_security_policy only: :conditional, if: :condition? do |p|
+      p.default_src "https://true.example.com"
+    end
+
+    content_security_policy only: :conditional, unless: :condition? do |p|
+      p.default_src "https://false.example.com"
+    end
+
+    content_security_policy only: :report_only do |p|
+      p.report_uri "/violations"
+    end
+
+    content_security_policy_report_only only: :report_only
+
+    def index
+      head :ok
+    end
+
+    def inline
+      head :ok
+    end
+
+    def conditional
+      head :ok
+    end
+
+    def report_only
+      head :ok
+    end
+
+    private
+      def condition?
+        params[:condition] == "true"
+      end
+  end
+
+  ROUTES = ActionDispatch::Routing::RouteSet.new
+  ROUTES.draw do
+    scope module: "content_security_policy_integration_test" do
+      get "/", to: "policy#index"
+      get "/inline", to: "policy#inline"
+      get "/conditional", to: "policy#conditional"
+      get "/report-only", to: "policy#report_only"
+    end
+  end
+
+  POLICY = ActionDispatch::ContentSecurityPolicy.new do |p|
+    p.default_src :self
+  end
+
+  class PolicyConfigMiddleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      env["action_dispatch.content_security_policy"] = POLICY
+      env["action_dispatch.content_security_policy_report_only"] = false
+      env["action_dispatch.show_exceptions"] = false
+
+      @app.call(env)
+    end
+  end
+
+  APP = build_app(ROUTES) do |middleware|
+    middleware.use PolicyConfigMiddleware
+    middleware.use ActionDispatch::ContentSecurityPolicy::Middleware
+  end
+
+  def app
+    APP
+  end
+
+  def test_generates_content_security_policy_header
+    get "/"
+    assert_policy "default-src 'self';"
+  end
+
+  def test_generates_inline_content_security_policy
+    get "/inline"
+    assert_policy "default-src https://example.com;"
+  end
+
+  def test_generates_conditional_content_security_policy
+    get "/conditional", params: { condition: "true" }
+    assert_policy "default-src https://true.example.com;"
+
+    get "/conditional", params: { condition: "false" }
+    assert_policy "default-src https://false.example.com;"
+  end
+
+  def test_generates_report_only_content_security_policy
+    get "/report-only"
+    assert_policy "default-src 'self'; report-uri /violations;", report_only: true
+  end
+
+  private
+
+    def env_config
+      Rails.application.env_config
+    end
+
+    def content_security_policy
+      env_config["action_dispatch.content_security_policy"]
+    end
+
+    def content_security_policy=(policy)
+      env_config["action_dispatch.content_security_policy"] = policy
+    end
+
+    def assert_policy(expected, report_only: false)
+      assert_response :success
+
+      if report_only
+        expected_header = "Content-Security-Policy-Report-Only"
+        unexpected_header = "Content-Security-Policy"
+      else
+        expected_header = "Content-Security-Policy"
+        unexpected_header = "Content-Security-Policy-Report-Only"
+      end
+
+      assert_nil response.headers[unexpected_header]
+      assert_equal expected, response.headers[expected_header]
+    end
+end
diff --git a/actionpack/test/dispatch/cookies_test.rb b/actionpack/test/dispatch/cookies_test.rb
index cb225c0f62..40cbad3b0d 100644
--- a/actionpack/test/dispatch/cookies_test.rb
+++ b/actionpack/test/dispatch/cookies_test.rb
@@ -3,7 +3,7 @@
 require "abstract_unit"
 require "openssl"
 require "active_support/key_generator"
-require "active_support/message_verifier"
+require "active_support/messages/rotation_configuration"
 
 class CookieJarTest < ActiveSupport::TestCase
   attr_reader :request
@@ -287,15 +287,25 @@ class CookiesTest < ActionController::TestCase
 
   tests TestController
 
-  SALT = "b3c631c314c0bbca50c1b2843150fe33"
+  SECRET_KEY_BASE = "b3c631c314c0bbca50c1b2843150fe33"
+  SIGNED_COOKIE_SALT = "signed cookie"
+  ENCRYPTED_COOKIE_SALT = "encrypted cookie"
+  ENCRYPTED_SIGNED_COOKIE_SALT = "sigend encrypted cookie"
+  AUTHENTICATED_ENCRYPTED_COOKIE_SALT = "authenticated encrypted cookie"
 
   def setup
     super
 
-    @request.env["action_dispatch.key_generator"] = ActiveSupport::KeyGenerator.new(SALT, iterations: 2)
+    @request.env["action_dispatch.key_generator"] = ActiveSupport::KeyGenerator.new(SECRET_KEY_BASE, iterations: 2)
+    @request.env["action_dispatch.cookies_rotations"] = ActiveSupport::Messages::RotationConfiguration.new
 
-    @request.env["action_dispatch.signed_cookie_salt"] =
-      @request.env["action_dispatch.authenticated_encrypted_cookie_salt"] = SALT
+    @request.env["action_dispatch.secret_key_base"] = SECRET_KEY_BASE
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = true
+
+    @request.env["action_dispatch.signed_cookie_salt"] = SIGNED_COOKIE_SALT
+    @request.env["action_dispatch.encrypted_cookie_salt"] = ENCRYPTED_COOKIE_SALT
+    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = ENCRYPTED_SIGNED_COOKIE_SALT
+    @request.env["action_dispatch.authenticated_encrypted_cookie_salt"] = AUTHENTICATED_ENCRYPTED_COOKIE_SALT
 
     @request.host = "www.nextangle.com"
   end
@@ -430,28 +440,72 @@ class CookiesTest < ActionController::TestCase
     assert_equal 45, cookies.signed[:user_id]
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
 
     verifier = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal, digest: "SHA1")
     assert_equal verifier.generate(45), cookies[:user_id]
   end
 
   def test_signed_cookie_using_custom_digest
-    @request.env["action_dispatch.cookies_digest"] = "SHA256"
+    @request.env["action_dispatch.signed_cookie_digest"] = "SHA256"
+
     get :set_signed_cookie
     cookies = @controller.send :cookies
     assert_not_equal 45, cookies[:user_id]
     assert_equal 45, cookies.signed[:user_id]
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
 
     verifier = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal, digest: "SHA256")
     assert_equal verifier.generate(45), cookies[:user_id]
   end
 
+  def test_signed_cookie_rotating_secret_and_digest
+    secret = "b3c631c314c0bbca50c1b2843150fe33"
+
+    @request.env["action_dispatch.signed_cookie_digest"] = "SHA256"
+    @request.env["action_dispatch.cookies_rotations"].rotate :signed, secret, digest: "SHA1"
+
+    old_message = ActiveSupport::MessageVerifier.new(secret, digest: "SHA1", serializer: Marshal).generate(45)
+    @request.headers["Cookie"] = "user_id=#{old_message}"
+
+    get :get_signed_cookie
+    assert_equal 45, @controller.send(:cookies).signed[:user_id]
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+    verifier = ActiveSupport::MessageVerifier.new(secret, digest: "SHA256", serializer: Marshal)
+    assert_equal 45, verifier.verify(@response.cookies["user_id"])
+  end
+
+  def test_signed_cookie_with_legacy_secret_scheme
+    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
+
+    old_message = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", digest: "SHA1", serializer: Marshal).generate(45)
+
+    @request.headers["Cookie"] = "user_id=#{old_message}"
+    get :get_signed_cookie
+    assert_equal 45, @controller.send(:cookies).signed[:user_id]
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key("signed cookie")
+    verifier = ActiveSupport::MessageVerifier.new(secret, digest: "SHA1", serializer: Marshal)
+    assert_equal 45, verifier.verify(@response.cookies["user_id"])
+  end
+
+  def test_tampered_with_signed_cookie
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+
+    verifier = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal, digest: "SHA1")
+    message = verifier.generate(45)
+
+    @request.headers["Cookie"] = "user_id=#{Marshal.dump 45}--#{message.split("--").last}"
+    get :get_signed_cookie
+    assert_nil @controller.send(:cookies).signed[:user_id]
+  end
+
   def test_signed_cookie_using_default_serializer
     get :set_signed_cookie
     cookies = @controller.send :cookies
@@ -494,8 +548,7 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
 
     marshal_value = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal).generate(45)
     @request.headers["Cookie"] = "user_id=#{marshal_value}"
@@ -514,8 +567,8 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+
     json_value = ActiveSupport::MessageVerifier.new(secret, serializer: JSON).generate(45)
     @request.headers["Cookie"] = "user_id=#{json_value}"
 
@@ -578,11 +631,10 @@ class CookiesTest < ActionController::TestCase
   def test_encrypted_cookie_using_hybrid_serializer_can_migrate_marshal_dumped_value_to_json
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
-    cipher = "aes-256-gcm"
-    salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: Marshal)
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], 32)
 
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
     marshal_value = encryptor.encrypt_and_sign("bar")
     @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape marshal_value}"
 
@@ -592,7 +644,7 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    json_encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    json_encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     assert_not_nil @response.cookies["foo"]
     assert_equal "bar", json_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
@@ -600,11 +652,10 @@ class CookiesTest < ActionController::TestCase
   def test_encrypted_cookie_using_hybrid_serializer_can_read_from_json_dumped_value
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
-    cipher = "aes-256-gcm"
-    salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], 32)
 
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     json_value = encryptor.encrypt_and_sign("bar")
     @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape json_value}"
 
@@ -691,65 +742,8 @@ class CookiesTest < ActionController::TestCase
     }
   end
 
-  def test_signed_uses_signed_cookie_jar_if_only_secret_token_is_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = nil
-    get :set_signed_cookie
-    assert_kind_of ActionDispatch::Cookies::SignedCookieJar, cookies.signed
-  end
-
-  def test_signed_uses_signed_cookie_jar_if_only_secret_key_base_is_set
-    @request.env["action_dispatch.secret_token"] = nil
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :set_signed_cookie
-    assert_kind_of ActionDispatch::Cookies::SignedCookieJar, cookies.signed
-  end
-
-  def test_signed_uses_upgrade_legacy_signed_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :set_signed_cookie
-    assert_kind_of ActionDispatch::Cookies::UpgradeLegacySignedCookieJar, cookies.signed
-  end
-
-  def test_signed_or_encrypted_uses_signed_cookie_jar_if_only_secret_token_is_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = nil
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::SignedCookieJar, cookies.signed_or_encrypted
-  end
-
-  def test_signed_or_encrypted_uses_encrypted_cookie_jar_if_only_secret_key_base_is_set
-    @request.env["action_dispatch.secret_token"] = nil
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::EncryptedCookieJar, cookies.signed_or_encrypted
-  end
-
-  def test_signed_or_encrypted_uses_upgrade_legacy_encrypted_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::UpgradeLegacyEncryptedCookieJar, cookies.signed_or_encrypted
-  end
-
-  def test_encrypted_uses_encrypted_cookie_jar_if_only_secret_key_base_is_set
-    @request.env["action_dispatch.secret_token"] = nil
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::EncryptedCookieJar, cookies.encrypted
-  end
-
-  def test_encrypted_uses_upgrade_legacy_encrypted_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::UpgradeLegacyEncryptedCookieJar, cookies.encrypted
-  end
-
   def test_legacy_signed_cookie_is_read_and_transparently_upgraded_by_signed_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33").generate(45)
 
@@ -766,9 +760,6 @@ class CookiesTest < ActionController::TestCase
 
   def test_legacy_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    @request.env["action_dispatch.encrypted_cookie_salt"] = "4433796b79d99a7735553e316522acee"
-    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = "00646eb40062e1b1deff205a27cd30f9"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33").generate("bar")
 
@@ -777,17 +768,14 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    cipher = "aes-256-gcm"
-    salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: Marshal)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], 32)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_json_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :json
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate(45)
 
@@ -805,7 +793,6 @@ class CookiesTest < ActionController::TestCase
   def test_legacy_json_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_json_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :json
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate("bar")
 
@@ -824,7 +811,6 @@ class CookiesTest < ActionController::TestCase
   def test_legacy_json_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_hybrid_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate(45)
 
@@ -842,7 +828,6 @@ class CookiesTest < ActionController::TestCase
   def test_legacy_json_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_hybrid_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate("bar")
 
@@ -851,17 +836,15 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    cipher = "aes-256-gcm"
     salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")]
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_marshal_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_hybrid_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33").generate(45)
 
@@ -878,6 +861,8 @@ class CookiesTest < ActionController::TestCase
 
   def test_legacy_marshal_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_hybrid_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
+
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = true
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
     @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
@@ -888,16 +873,14 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    cipher = "aes-256-gcm"
     salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")]
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_signed_cookie_is_treated_as_nil_by_signed_cookie_jar_if_tampered
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     @request.headers["Cookie"] = "user_id=45"
     get :get_signed_cookie
@@ -908,7 +891,6 @@ class CookiesTest < ActionController::TestCase
 
   def test_legacy_signed_cookie_is_treated_as_nil_by_encrypted_cookie_jar_if_tampered
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     @request.headers["Cookie"] = "foo=baz"
     get :get_encrypted_cookie
@@ -917,18 +899,50 @@ class CookiesTest < ActionController::TestCase
     assert_nil @response.cookies["foo"]
   end
 
-  def test_legacy_hmac_aes_cbc_encrypted_marshal_cookie_is_upgraded_to_authenticated_encrypted_cookie
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
+  def test_use_authenticated_cookie_encryption_uses_legacy_hmac_aes_cbc_encryption_when_not_enabled
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = nil
 
-    @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
+    key_generator = @request.env["action_dispatch.key_generator"]
+    encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]
+    encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
+    secret = key_generator.generate_key(encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-cbc"))
+    sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", digest: "SHA1", serializer: Marshal)
+
+    get :set_encrypted_cookie
+
+    cookies = @controller.send :cookies
+    assert_not_equal "bar", cookies[:foo]
+    assert_equal "bar", cookies.encrypted[:foo]
+    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+  end
+
+  def test_rotating_signed_cookies_digest
+    @request.env["action_dispatch.signed_cookie_digest"] = "SHA256"
+    @request.env["action_dispatch.cookies_rotations"].rotate :signed, digest: "SHA1"
 
     key_generator = @request.env["action_dispatch.key_generator"]
+
+    old_secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+    old_value = ActiveSupport::MessageVerifier.new(old_secret).generate(45)
+
+    @request.headers["Cookie"] = "user_id=#{old_value}"
+    get :get_signed_cookie
+
+    assert_equal 45, @controller.send(:cookies).signed[:user_id]
+
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+    verifier = ActiveSupport::MessageVerifier.new(secret, digest: "SHA256")
+    assert_equal 45, verifier.verify(@response.cookies["user_id"])
+  end
+
+  def test_legacy_hmac_aes_cbc_encrypted_marshal_cookie_is_upgraded_to_authenticated_encrypted_cookie
+    key_generator = @request.env["action_dispatch.key_generator"]
     encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]
     encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
-    secret = key_generator.generate_key(encrypted_cookie_salt)
+    secret = key_generator.generate_key(encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-cbc"))
     sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
-    marshal_value = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: Marshal).encrypt_and_sign("bar")
+    marshal_value = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", serializer: Marshal).encrypt_and_sign("bar")
 
     @request.headers["Cookie"] = "foo=#{marshal_value}"
 
@@ -938,27 +952,22 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    aead_cipher = "aes-256-gcm"
     aead_salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    aead_secret = key_generator.generate_key(aead_salt)[0, ActiveSupport::MessageEncryptor.key_len(aead_cipher)]
-    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: aead_cipher, serializer: Marshal)
+    aead_secret = key_generator.generate_key(aead_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm"))
+    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: "aes-256-gcm", serializer: Marshal)
 
     assert_equal "bar", aead_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_hmac_aes_cbc_encrypted_json_cookie_is_upgraded_to_authenticated_encrypted_cookie
     @request.env["action_dispatch.cookies_serializer"] = :json
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-
-    @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
 
     key_generator = @request.env["action_dispatch.key_generator"]
     encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]
     encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
-    secret = key_generator.generate_key(encrypted_cookie_salt)
+    secret = key_generator.generate_key(encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-cbc"))
     sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
-    marshal_value = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON).encrypt_and_sign("bar")
+    marshal_value = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", serializer: JSON).encrypt_and_sign("bar")
 
     @request.headers["Cookie"] = "foo=#{marshal_value}"
 
@@ -968,19 +977,17 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    aead_cipher = "aes-256-gcm"
     aead_salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    aead_secret = key_generator.generate_key(aead_salt)[0, ActiveSupport::MessageEncryptor.key_len(aead_cipher)]
-    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: aead_cipher, serializer: JSON)
+    aead_secret = key_generator.generate_key(aead_salt)[0, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")]
+    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: "aes-256-gcm", serializer: JSON)
 
     assert_equal "bar", aead_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_hmac_aes_cbc_encrypted_cookie_using_64_byte_key_is_upgraded_to_authenticated_encrypted_cookie
     @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-
-    @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
+    @request.env["action_dispatch.encrypted_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
+    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
 
     # Cookie generated with 64 bytes secret
     message = ["566d4e75536d686e633246564e6b493062557079626c566d51574d30515430394c53315665564a694e4563786555744f57537454576b396a5a31566a626e52525054303d2d2d34663234333330623130623261306163363562316266323335396164666364613564643134623131"].pack("H*")
@@ -991,15 +998,35 @@ class CookiesTest < ActionController::TestCase
     cookies = @controller.send :cookies
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
-    cipher = "aes-256-gcm"
 
     salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: Marshal)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(salt, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm"))
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
 
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
+  def test_encrypted_cookie_rotating_secret
+    secret = "b3c631c314c0bbca50c1b2843150fe33"
+
+    @request.env["action_dispatch.encrypted_cookie_cipher"] = "aes-256-gcm"
+    @request.env["action_dispatch.cookies_rotations"].rotate :encrypted, secret
+
+    key_len = ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")
+
+    old_message = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal).encrypt_and_sign(45)
+
+    @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape old_message}"
+
+    get :get_encrypted_cookie
+    assert_equal 45, @controller.send(:cookies).encrypted[:foo]
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], key_len)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
+    assert_equal 45, encryptor.decrypt_and_verify(@response.cookies["foo"])
+  end
+
   def test_cookie_with_all_domain_option
     get :set_cookie_with_domain
     assert_response :success
diff --git a/actionpack/test/dispatch/mime_type_test.rb b/actionpack/test/dispatch/mime_type_test.rb
index 90e95e972d..6854783386 100644
--- a/actionpack/test/dispatch/mime_type_test.rb
+++ b/actionpack/test/dispatch/mime_type_test.rb
@@ -30,21 +30,21 @@ class MimeTypeTest < ActiveSupport::TestCase
 
   test "parse text with trailing star at the beginning" do
     accept = "text/*, text/html, application/json, multipart/form-data"
-    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:xml], Mime[:yaml], Mime[:json], Mime[:multipart_form]]
+    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:vtt], Mime[:xml], Mime[:yaml], Mime[:json], Mime[:multipart_form]]
     parsed = Mime::Type.parse(accept)
-    assert_equal expect, parsed
+    assert_equal expect.map(&:to_s), parsed.map(&:to_s)
   end
 
   test "parse text with trailing star in the end" do
     accept = "text/html, application/json, multipart/form-data, text/*"
-    expect = [Mime[:html], Mime[:json], Mime[:multipart_form], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:xml], Mime[:yaml]]
+    expect = [Mime[:html], Mime[:json], Mime[:multipart_form], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:vtt], Mime[:xml], Mime[:yaml]]
     parsed = Mime::Type.parse(accept)
-    assert_equal expect, parsed
+    assert_equal expect.map(&:to_s), parsed.map(&:to_s)
   end
 
   test "parse text with trailing star" do
     accept = "text/*"
-    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:xml], Mime[:yaml], Mime[:json]]
+    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:vtt], Mime[:xml], Mime[:yaml], Mime[:json]]
     parsed = Mime::Type.parse(accept)
     assert_equal expect.map(&:to_s).sort!, parsed.map(&:to_s).sort!
   end
diff --git a/actionpack/test/dispatch/request_test.rb b/actionpack/test/dispatch/request_test.rb
index 68c6d26364..8661dc56d6 100644
--- a/actionpack/test/dispatch/request_test.rb
+++ b/actionpack/test/dispatch/request_test.rb
@@ -763,7 +763,7 @@ class RequestMethod < BaseRequestTest
 
   test "post uneffected by local inflections" do
     existing_acronyms = ActiveSupport::Inflector.inflections.acronyms.dup
-    existing_acronym_regex = ActiveSupport::Inflector.inflections.acronym_regex.dup
+    assert_deprecated { ActiveSupport::Inflector.inflections.acronym_regex.dup }
     begin
       ActiveSupport::Inflector.inflections do |inflect|
         inflect.acronym "POS"
@@ -777,7 +777,7 @@ class RequestMethod < BaseRequestTest
       # Reset original acronym set
       ActiveSupport::Inflector.inflections do |inflect|
         inflect.send(:instance_variable_set, "@acronyms", existing_acronyms)
-        inflect.send(:instance_variable_set, "@acronym_regex", existing_acronym_regex)
+        inflect.send(:define_acronym_regex_patterns)
       end
     end
   end
@@ -1304,3 +1304,18 @@ class RequestFormData < BaseRequestTest
     assert !request.form_data?
   end
 end
+
+class EarlyHintsRequestTest < BaseRequestTest
+  def setup
+    super
+    @env["rack.early_hints"] = lambda { |links| links }
+    @request = stub_request
+  end
+
+  test "when early hints is set in the env link headers are sent" do
+    early_hints = @request.send_early_hints("Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload")
+    expected_hints = { "Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload" }
+
+    assert_equal expected_hints, early_hints
+  end
+end
diff --git a/actionpack/test/dispatch/routing_assertions_test.rb b/actionpack/test/dispatch/routing_assertions_test.rb
index e492a56653..a5198f2f13 100644
--- a/actionpack/test/dispatch/routing_assertions_test.rb
+++ b/actionpack/test/dispatch/routing_assertions_test.rb
@@ -1,14 +1,40 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
+require "rails/engine"
 require "controller/fake_controllers"
 
 class SecureArticlesController < ArticlesController; end
 class BlockArticlesController < ArticlesController; end
 class QueryArticlesController < ArticlesController; end
 
+class SecureBooksController < BooksController; end
+class BlockBooksController < BooksController; end
+class QueryBooksController < BooksController; end
+
 class RoutingAssertionsTest < ActionController::TestCase
   def setup
+    engine = Class.new(Rails::Engine) do
+      def self.name
+        "blog_engine"
+      end
+    end
+    engine.routes.draw do
+      resources :books
+
+      scope "secure", constraints: { protocol: "https://" } do
+        resources :books, controller: "secure_books"
+      end
+
+      scope "block", constraints: lambda { |r| r.ssl? } do
+        resources :books, controller: "block_books"
+      end
+
+      scope "query", constraints: lambda { |r| r.params[:use_query] == "true" } do
+        resources :books, controller: "query_books"
+      end
+    end
+
     @routes = ActionDispatch::Routing::RouteSet.new
     @routes.draw do
       resources :articles
@@ -24,6 +50,8 @@ class RoutingAssertionsTest < ActionController::TestCase
       scope "query", constraints: lambda { |r| r.params[:use_query] == "true" } do
         resources :articles, controller: "query_articles"
       end
+
+      mount engine => "/shelf"
     end
   end
 
@@ -83,6 +111,49 @@ class RoutingAssertionsTest < ActionController::TestCase
     assert_match err.message, "This is a really bad msg"
   end
 
+  def test_assert_recognizes_with_engine
+    assert_recognizes({ controller: "books", action: "index" }, "/shelf/books")
+    assert_recognizes({ controller: "books", action: "show", id: "1" }, "/shelf/books/1")
+  end
+
+  def test_assert_recognizes_with_engine_and_extras
+    assert_recognizes({ controller: "books", action: "index", page: "1" }, "/shelf/books", page: "1")
+  end
+
+  def test_assert_recognizes_with_engine_and_method
+    assert_recognizes({ controller: "books", action: "create" }, { path: "/shelf/books", method: :post })
+    assert_recognizes({ controller: "books", action: "update", id: "1" }, { path: "/shelf/books/1", method: :put })
+  end
+
+  def test_assert_recognizes_with_engine_and_hash_constraint
+    assert_raise(Assertion) do
+      assert_recognizes({ controller: "secure_books", action: "index" }, "http://test.host/shelf/secure/books")
+    end
+    assert_recognizes({ controller: "secure_books", action: "index", protocol: "https://" }, "https://test.host/shelf/secure/books")
+  end
+
+  def test_assert_recognizes_with_engine_and_block_constraint
+    assert_raise(Assertion) do
+      assert_recognizes({ controller: "block_books", action: "index" }, "http://test.host/shelf/block/books")
+    end
+    assert_recognizes({ controller: "block_books", action: "index" }, "https://test.host/shelf/block/books")
+  end
+
+  def test_assert_recognizes_with_engine_and_query_constraint
+    assert_raise(Assertion) do
+      assert_recognizes({ controller: "query_books", action: "index", use_query: "false" }, "/shelf/query/books", use_query: "false")
+    end
+    assert_recognizes({ controller: "query_books", action: "index", use_query: "true" }, "/shelf/query/books", use_query: "true")
+  end
+
+  def test_assert_recognizes_raises_message_with_engine
+    err = assert_raise(Assertion) do
+      assert_recognizes({ controller: "secure_books", action: "index" }, "http://test.host/shelf/secure/books", {}, "This is a really bad msg")
+    end
+
+    assert_match err.message, "This is a really bad msg"
+  end
+
   def test_assert_routing
     assert_routing("/articles", controller: "articles", action: "index")
   end
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 446b65a9b9..b2d2bf0416 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -3,6 +3,7 @@
 require "erb"
 require "abstract_unit"
 require "controller/fake_controllers"
+require "active_support/messages/rotation_configuration"
 
 class TestRoutingMapper < ActionDispatch::IntegrationTest
   SprocketsApp = lambda { |env|
@@ -4947,6 +4948,7 @@ end
 class FlashRedirectTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   Generator  = ActiveSupport::LegacyKeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33")
+  Rotations  = ActiveSupport::Messages::RotationConfiguration.new
 
   class KeyGeneratorMiddleware
     def initialize(app)
@@ -4955,6 +4957,8 @@ class FlashRedirectTest < ActionDispatch::IntegrationTest
 
     def call(env)
       env["action_dispatch.key_generator"] ||= Generator
+      env["action_dispatch.cookies_rotations"] ||= Rotations
+
       @app.call(env)
     end
   end
@@ -5053,3 +5057,40 @@ class TestRecognizePath < ActionDispatch::IntegrationTest
       Routes.recognize_path(*args)
     end
 end
+
+class TestRelativeUrlRootGeneration < ActionDispatch::IntegrationTest
+  config = ActionDispatch::Routing::RouteSet::Config.new("/blog", false)
+
+  stub_controllers(config) do |routes|
+    Routes = routes
+
+    routes.draw do
+      get "/", to: "posts#index", as: :posts
+      get "/:id", to: "posts#show", as: :post
+    end
+  end
+
+  include Routes.url_helpers
+
+  APP = build_app Routes
+
+  def app
+    APP
+  end
+
+  def test_url_helpers
+    assert_equal "/blog/", posts_path({})
+    assert_equal "/blog/", Routes.url_helpers.posts_path({})
+
+    assert_equal "/blog/1", post_path(id: "1")
+    assert_equal "/blog/1", Routes.url_helpers.post_path(id: "1")
+  end
+
+  def test_optimized_url_helpers
+    assert_equal "/blog/", posts_path
+    assert_equal "/blog/", Routes.url_helpers.posts_path
+
+    assert_equal "/blog/1", post_path("1")
+    assert_equal "/blog/1", Routes.url_helpers.post_path("1")
+  end
+end
diff --git a/actionpack/test/dispatch/session/cookie_store_test.rb b/actionpack/test/dispatch/session/cookie_store_test.rb
index 6517cf4c99..e34426a471 100644
--- a/actionpack/test/dispatch/session/cookie_store_test.rb
+++ b/actionpack/test/dispatch/session/cookie_store_test.rb
@@ -3,14 +3,19 @@
 require "abstract_unit"
 require "stringio"
 require "active_support/key_generator"
+require "active_support/messages/rotation_configuration"
 
 class CookieStoreTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   SessionSecret = "b3c631c314c0bbca50c1b2843150fe33"
-  Generator = ActiveSupport::LegacyKeyGenerator.new(SessionSecret)
+  SessionSalt   = "authenticated encrypted cookie"
 
-  Verifier = ActiveSupport::MessageVerifier.new(SessionSecret, digest: "SHA1")
-  SignedBar = Verifier.generate(foo: "bar", session_id: SecureRandom.hex(16))
+  Generator = ActiveSupport::KeyGenerator.new(SessionSecret, iterations: 1000)
+  Rotations = ActiveSupport::Messages::RotationConfiguration.new
+
+  Encryptor = ActiveSupport::MessageEncryptor.new(
+    Generator.generate_key(SessionSalt, 32), cipher: "aes-256-gcm", serializer: Marshal
+  )
 
   class TestController < ActionController::Base
     def no_session_access
@@ -23,12 +28,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
     def set_session_value
       session[:foo] = "bar"
-      render plain: Rack::Utils.escape(Verifier.generate(session.to_hash))
-    end
-
-    def set_session_value_expires_in_five_hours
-      session[:foo] = "bar"
-      render plain: Rack::Utils.escape(Verifier.generate(session.to_hash, expires_in: 5.hours))
+      render body: nil
     end
 
     def get_session_value
@@ -70,19 +70,35 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     end
   end
 
+  def parse_cookie_from_header
+    cookie_matches = headers["Set-Cookie"].match(/#{SessionKey}=([^;]+)/)
+    cookie_matches && cookie_matches[1]
+  end
+
+  def assert_session_cookie(cookie_string, contents)
+    assert_includes headers["Set-Cookie"], cookie_string
+
+    session_value = parse_cookie_from_header
+    session_data = Encryptor.decrypt_and_verify(Rack::Utils.unescape(session_value)) rescue nil
+
+    assert_not_nil session_data, "session failed to decrypt"
+    assert_equal session_data.slice(*contents.keys), contents
+  end
+
   def test_setting_session_value
     with_test_route_set do
       get "/set_session_value"
+
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
     end
   end
 
   def test_getting_session_value
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
+      get "/set_session_value"
       get "/get_session_value"
+
       assert_response :success
       assert_equal 'foo: "bar"', response.body
     end
@@ -90,8 +106,9 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_getting_session_id
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
+      get "/set_session_value"
       get "/persistent_session_id"
+
       assert_response :success
       assert_equal 32, response.body.size
       session_id = response.body
@@ -104,8 +121,12 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_disregards_tampered_sessions
     with_test_route_set do
-      cookies[SessionKey] = "BAh7BjoIZm9vIghiYXI%3D--123456780"
+      encryptor = ActiveSupport::MessageEncryptor.new("A" * 32, cipher: "aes-256-gcm", serializer: Marshal)
+
+      cookies[SessionKey] = encryptor.encrypt_and_sign("foo" => "bar", "session_id" => "abc")
+
       get "/get_session_value"
+
       assert_response :success
       assert_equal "foo: nil", response.body
     end
@@ -133,19 +154,19 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
   def test_does_set_secure_cookies_over_https
     with_test_route_set(secure: true) do
       get "/set_session_value", headers: { "HTTPS" => "on" }
+
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; secure; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; secure; HttpOnly", "foo" => "bar"
     end
   end
 
   # {:foo=>#<SessionAutoloadTest::Foo bar:"baz">, :session_id=>"ce8b0752a6ab7c7af3cdb8a80e6b9e46"}
-  SignedSerializedCookie = "BAh7BzoIZm9vbzodU2Vzc2lvbkF1dG9sb2FkVGVzdDo6Rm9vBjoJQGJhciIIYmF6Og9zZXNzaW9uX2lkIiVjZThiMDc1MmE2YWI3YzdhZjNjZGI4YTgwZTZiOWU0Ng==--2bf3af1ae8bd4e52b9ac2099258ace0c380e601c"
+  EncryptedSerializedCookie = "9RZ2Fij0qLveUwM4s+CCjGqhpjyUC8jiBIf/AiBr9M3TB8xh2vQZtvSOMfN3uf6oYbbpIDHAcOFIEl69FcW1ozQYeSrCLonYCazoh34ZdYskIQfGwCiSYleVXG1OD9Z4jFqeVArw4Ewm0paOOPLbN1rc6A==--I359v/KWdZ1ok0ey--JFFhuPOY7WUo6tB/eP05Aw=="
 
   def test_deserializes_unloaded_classes_on_get_id
     with_test_route_set do
       with_autoload_path "session_autoload_test" do
-        cookies[SessionKey] = SignedSerializedCookie
+        cookies[SessionKey] = EncryptedSerializedCookie
         get "/get_session_id"
         assert_response :success
         assert_equal "id: ce8b0752a6ab7c7af3cdb8a80e6b9e46", response.body, "should auto-load unloaded class"
@@ -156,7 +177,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
   def test_deserializes_unloaded_classes_on_get_value
     with_test_route_set do
       with_autoload_path "session_autoload_test" do
-        cookies[SessionKey] = SignedSerializedCookie
+        cookies[SessionKey] = EncryptedSerializedCookie
         get "/get_session_value"
         assert_response :success
         assert_equal 'foo: #<SessionAutoloadTest::Foo bar:"baz">', response.body, "should auto-load unloaded class"
@@ -195,8 +216,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
       get "/set_session_value"
       assert_response :success
       session_payload = response.body
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
 
       get "/call_reset_session"
       assert_response :success
@@ -214,8 +234,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     with_test_route_set do
       get "/set_session_value"
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
 
       get "/get_class_after_reset_session"
       assert_response :success
@@ -237,8 +256,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     with_test_route_set do
       get "/set_session_value"
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
 
       get "/call_session_clear"
       assert_response :success
@@ -251,7 +269,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_persistent_session_id
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
+      get "/set_session_value"
       get "/persistent_session_id"
       assert_response :success
       assert_equal 32, response.body.size
@@ -266,8 +284,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_setting_session_id_to_nil_is_respected
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
-
+      get "/set_session_value"
       get "/get_session_id"
       sid = response.body
       assert_equal 36, sid.size
@@ -281,31 +298,53 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     with_test_route_set(expire_after: 5.hours) do
       # First request accesses the session
       time = Time.local(2008, 4, 24)
-      cookie_body = nil
 
       Time.stub :now, time do
         expected_expiry = (time + 5.hours).gmtime.strftime("%a, %d %b %Y %H:%M:%S -0000")
 
-        cookies[SessionKey] = SignedBar
+        get "/set_session_value"
 
-        get "/set_session_value_expires_in_five_hours"
         assert_response :success
-
-        cookie_body = response.body
-        assert_equal "_myapp_session=#{cookie_body}; path=/; expires=#{expected_expiry}; HttpOnly",
-          headers["Set-Cookie"]
+        assert_session_cookie "path=/; expires=#{expected_expiry}; HttpOnly", "foo" => "bar"
       end
 
       # Second request does not access the session
-      time = Time.local(2008, 4, 25)
+      time = time + 3.hours
       Time.stub :now, time do
         expected_expiry = (time + 5.hours).gmtime.strftime("%a, %d %b %Y %H:%M:%S -0000")
 
         get "/no_session_access"
+
         assert_response :success
+        assert_session_cookie "path=/; expires=#{expected_expiry}; HttpOnly", "foo" => "bar"
+      end
+    end
+  end
+
+  def test_session_store_with_expire_after_does_not_accept_expired_session
+    with_test_route_set(expire_after: 5.hours) do
+      # First request accesses the session
+      time = Time.local(2017, 11, 12)
+
+      Time.stub :now, time do
+        expected_expiry = (time + 5.hours).gmtime.strftime("%a, %d %b %Y %H:%M:%S -0000")
+
+        get "/set_session_value"
+        get "/get_session_value"
 
-        assert_equal "_myapp_session=#{cookies[SessionKey]}; path=/; expires=#{expected_expiry}; HttpOnly",
-          headers["Set-Cookie"]
+        assert_response :success
+        assert_equal 'foo: "bar"', response.body
+        assert_session_cookie "path=/; expires=#{expected_expiry}; HttpOnly", "foo" => "bar"
+      end
+
+      # Second request is beyond the expiry time and the session is invalidated
+      time += 5.hours + 1.minute
+
+      Time.stub :now, time do
+        get "/get_session_value"
+
+        assert_response :success
+        assert_equal "foo: nil", response.body
       end
     end
   end
@@ -345,7 +384,15 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     def get(path, *args)
       args[0] ||= {}
       args[0][:headers] ||= {}
-      args[0][:headers]["action_dispatch.key_generator"] ||= Generator
+      args[0][:headers].tap do |config|
+        config["action_dispatch.secret_key_base"] = SessionSecret
+        config["action_dispatch.authenticated_encrypted_cookie_salt"] = SessionSalt
+        config["action_dispatch.use_authenticated_cookie_encryption"] = true
+
+        config["action_dispatch.key_generator"] ||= Generator
+        config["action_dispatch.cookies_rotations"] ||= Rotations
+      end
+
       super(path, *args)
     end
 
diff --git a/actionpack/test/dispatch/system_testing/driver_test.rb b/actionpack/test/dispatch/system_testing/driver_test.rb
index e6f9353b22..fcdaf7fb4c 100644
--- a/actionpack/test/dispatch/system_testing/driver_test.rb
+++ b/actionpack/test/dispatch/system_testing/driver_test.rb
@@ -17,6 +17,22 @@ class DriverTest < ActiveSupport::TestCase
     assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
   end
 
+  test "initializing the driver with a headless chrome" do
+    driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :headless_chrome, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
+    assert_equal :selenium, driver.instance_variable_get(:@name)
+    assert_equal :headless_chrome, driver.instance_variable_get(:@browser)
+    assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
+    assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
+  end
+
+  test "initializing the driver with a headless firefox" do
+    driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :headless_firefox, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
+    assert_equal :selenium, driver.instance_variable_get(:@name)
+    assert_equal :headless_firefox, driver.instance_variable_get(:@browser)
+    assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
+    assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
+  end
+
   test "initializing the driver with a poltergeist" do
     driver = ActionDispatch::SystemTesting::Driver.new(:poltergeist, screen_size: [1400, 1400], options: { js_errors: false })
     assert_equal :poltergeist, driver.instance_variable_get(:@name)
diff --git a/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb b/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
index 2afda31cf5..264844fc7d 100644
--- a/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
+++ b/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
@@ -35,6 +35,11 @@ class ScreenshotHelperTest < ActiveSupport::TestCase
     end
   end
 
+  test "defaults to simple output for the screenshot" do
+    new_test = DrivenBySeleniumWithChrome.new("x")
+    assert_equal "simple", new_test.send(:output_type)
+  end
+
   test "display_image return artifact format when specify RAILS_SYSTEM_TESTING_SCREENSHOT environment" do
     begin
       original_output_type = ENV["RAILS_SYSTEM_TESTING_SCREENSHOT"]
@@ -42,6 +47,8 @@ class ScreenshotHelperTest < ActiveSupport::TestCase
 
       new_test = DrivenBySeleniumWithChrome.new("x")
 
+      assert_equal "artifact", new_test.send(:output_type)
+
       Rails.stub :root, Pathname.getwd do
         new_test.stub :passed?, false do
           assert_match %r|url=artifact://.+?tmp/screenshots/failures_x\.png|, new_test.send(:display_image)
diff --git a/actionpack/test/dispatch/system_testing/server_test.rb b/actionpack/test/dispatch/system_testing/server_test.rb
index ed65d93e49..1866225fc1 100644
--- a/actionpack/test/dispatch/system_testing/server_test.rb
+++ b/actionpack/test/dispatch/system_testing/server_test.rb
@@ -9,10 +9,6 @@ class ServerTest < ActiveSupport::TestCase
     ActionDispatch::SystemTesting::Server.new.run
   end
 
-  test "initializing the server port" do
-    assert_includes Capybara.servers, :rails_puma
-  end
-
   test "port is always included" do
     assert Capybara.always_include_port, "expected Capybara.always_include_port to be true"
   end
diff --git a/actionpack/test/dispatch/system_testing/system_test_case_test.rb b/actionpack/test/dispatch/system_testing/system_test_case_test.rb
index b60ec559ae..b078a5abc5 100644
--- a/actionpack/test/dispatch/system_testing/system_test_case_test.rb
+++ b/actionpack/test/dispatch/system_testing/system_test_case_test.rb
@@ -22,6 +22,18 @@ class SetDriverToSeleniumTest < DrivenBySeleniumWithChrome
   end
 end
 
+class SetDriverToSeleniumHeadlessChromeTest < DrivenBySeleniumWithHeadlessChrome
+  test "uses selenium headless chrome" do
+    assert_equal :selenium, Capybara.current_driver
+  end
+end
+
+class SetDriverToSeleniumHeadlessFirefoxTest < DrivenBySeleniumWithHeadlessFirefox
+  test "uses selenium headless firefox" do
+    assert_equal :selenium, Capybara.current_driver
+  end
+end
+
 class SetHostTest < DrivenByRackTest
   test "sets default host" do
     assert_equal "http://127.0.0.1", Capybara.app_host
@@ -36,32 +48,37 @@ end
 
 class UndefMethodsTest < DrivenBySeleniumWithChrome
   test "get" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       get "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #get; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "post" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       post "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #post; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "put" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       put "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #put; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "patch" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       patch "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #patch; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "delete" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       delete "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #delete; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 end
diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index b22686d1d8..f42ada0baa 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,39 @@
+*   Add `preload_link_tag` helper
+
+    This helper that allows to the browser to initiate early fetch of resources
+    (different to the specified in `javascript_include_tag` and `stylesheet_link_tag`).
+    Additionally, this sends Early Hints if supported by browser.
+
+    *Guillermo Iguaran*
+
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Change `form_with` to generates ids by default.
+
+    When `form_with` was introduced we disabled the automatic generation of ids
+    that was enabled in `form_for`. This usually is not an good idea since labels don't work
+    when the input doesn't have an id and it made harder to test with Capybara.
+
+    You can still disable the automatic generation of ids setting `config.action_view.form_with_generates_ids`
+    to `false.`
+
+    *Nick Pezza*
+
+*   Fix issues with `field_error_proc` wrapping `optgroup` and select divider `option`.
+
+    Fixes #31088
+
+    *Matthias Neumayr*
+
+*   Remove deprecated Erubis ERB handler.
+
+    *Rafael Mendonça França*
+
 *   Remove default `alt` text generation.
 
     Fixes #30096
diff --git a/actionview/README.rdoc b/actionview/README.rdoc
index d5029599b7..03a0723564 100644
--- a/actionview/README.rdoc
+++ b/actionview/README.rdoc
@@ -11,7 +11,7 @@ The latest version of Action View can be installed with RubyGems:
 
   $ gem install actionview
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/actionview
 
@@ -29,7 +29,7 @@ API documentation is at
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actionview/RUNNING_UJS_TESTS.rdoc b/actionview/RUNNING_UJS_TESTS.rdoc
index a575624a06..e30c2aee55 100644
--- a/actionview/RUNNING_UJS_TESTS.rdoc
+++ b/actionview/RUNNING_UJS_TESTS.rdoc
@@ -1,7 +1,8 @@
 == Running UJS tests
 
-Ensure that you can build the project and run tests.
-Run rake ujs:server first, and then run the web tests by
-visiting http://localhost:4567 in your browser.
+Ensure that you can build the project by running:
+   rake ujs:server
 
-rake ujs:server
+Then run the web tests by visiting the following URL in your browser:
+
+   http://localhost:4567
diff --git a/actionview/RUNNING_UNIT_TESTS.rdoc b/actionview/RUNNING_UNIT_TESTS.rdoc
index 6c4e5e983a..4442dbdb9e 100644
--- a/actionview/RUNNING_UNIT_TESTS.rdoc
+++ b/actionview/RUNNING_UNIT_TESTS.rdoc
@@ -2,13 +2,13 @@
 
 The easiest way to run the unit tests is through Rake. The default task runs
 the entire test suite for all classes. For more information, checkout the
-full array of rake tasks with "rake -T"
+full array of rake tasks with <tt>rake -T</tt>
 
-Rake can be found at http://docs.seattlerb.org/rake/.
+Rake can be found at https://ruby.github.io/rake/.
 
 == Running by hand
 
-To run a single test suite
+Run a single test suite:
 
    rake test TEST=path/to/test.rb
 
@@ -18,10 +18,9 @@ which can be further narrowed down to one test:
 
 == Dependency on Active Record and database setup
 
-Test cases in the test/activerecord/ directory depend on having
-activerecord and sqlite3 installed. If Active Record is not in
-actionview/../activerecord directory, or the sqlite3 rubygem is not installed,
-these tests are skipped.
-
+Test cases in the +test/activerecord/+ directory depend on having
+activerecord+ and +sqlite3+ installed. If Active Record is not in
+actionview/../activerecord+ directory, or the +sqlite3+ Ruby gem is not installed,
+  these tests are skipped.
 Other tests are runnable from a fresh copy of actionview without any configuration.
 
diff --git a/actionview/Rakefile b/actionview/Rakefile
index 20dfa4e114..8650f541b0 100644
--- a/actionview/Rakefile
+++ b/actionview/Rakefile
@@ -32,7 +32,7 @@ namespace :test do
   task :ujs do
     begin
       Dir.mkdir("log")
-      pid = spawn("bundle exec rackup test/ujs/config.ru -p 4567 -s puma > log/test.log 2>&1")
+      pid = spawn("bundle exec rackup test/ujs/config.ru -p 4567 -s puma > log/test.log 2>&1", pgroup: true)
 
       start_time = Time.now
 
@@ -45,10 +45,10 @@ namespace :test do
         end
       end
 
-      system("npm run lint && phantomjs ../ci/phantomjs.js http://localhost:4567/")
-      status = $?.to_i
+      system("npm run lint && bundle exec ruby ../ci/qunit-selenium-runner.rb http://localhost:4567/")
+      status = $?.exitstatus
     ensure
-      Process.kill("KILL", pid) if pid
+      Process.kill("KILL", -pid) if pid
       FileUtils.rm_rf("log")
     end
 
diff --git a/actionview/app/assets/javascripts/README.md b/actionview/app/assets/javascripts/README.md
index f321b9f720..8198011b02 100644
--- a/actionview/app/assets/javascripts/README.md
+++ b/actionview/app/assets/javascripts/README.md
@@ -1,5 +1,4 @@
-Ruby on Rails unobtrusive scripting adapter.
-========================================
+# Ruby on Rails unobtrusive scripting adapter
 
 This unobtrusive scripting support file is developed for the Ruby on Rails framework, but is not strictly tied to any specific backend. You can drop this into any application to:
 
@@ -8,51 +7,47 @@ This unobtrusive scripting support file is developed for the Ruby on Rails frame
 - make forms or hyperlinks submit data asynchronously with Ajax;
 - have submit buttons become automatically disabled on form submit to prevent double-clicking.
 
-These features are achieved by adding certain ["data" attributes][data] to your HTML markup. In Rails, they are added by the framework's template helpers.
+These features are achieved by adding certain [`data` attributes][data] to your HTML markup. In Rails, they are added by the framework's template helpers.
 
-Requirements
-------------
+## Optional prerequisites
 
-- HTML5 doctype (optional).
+Note that the `data` attributes this library adds are a feature of HTML5. If you're not targeting HTML5, these attributes may make your HTML to fail [validation][validator]. However, this shouldn't create any issues for web browsers or other user agents.
 
-If you don't use HTML5, adding "data" attributes to your HTML4 or XHTML pages might make them fail [W3C markup validation][validator]. However, this shouldn't create any issues for web browsers or other user agents.
+## Installation
 
-Installation using npm
-------------
+### NPM
 
-Run `npm install rails-ujs --save` to install the rails-ujs package.
+    npm install rails-ujs --save
+    
+### Yarn
+    
+    yarn add rails-ujs
 
-Installation using Yarn
-------------
+## Usage
 
-Run `yarn add rails-ujs` to install the rails-ujs package.
+### Asset pipeline
 
-Usage
-------------
-
-Require `rails-ujs` in your application.js manifest.
+In a conventional Rails application that uses the asset pipeline, require `rails-ujs` in your `application.js` manifest:
 
 ```javascript
 //= require rails-ujs
 ```
 
-Usage with yarn
-------------
+### ES2015+
 
-When using with the Webpacker gem or your preferred JavaScript bundler, just
-add the following to your main JS file and compile.
+If you're using the Webpacker gem or some other JavaScript bundler, add the following to your main JS file:
 
 ```javascript
 import Rails from 'rails-ujs';
 Rails.start()
 ```
 
-How to run tests
-------------
+## How to run tests
 
 Run `bundle exec rake ujs:server` first, and then run the web tests by visiting http://localhost:4567 in your browser.
 
 ## License
+
 rails-ujs is released under the [MIT License](MIT-LICENSE).
 
 [data]: http://www.w3.org/TR/html5/dom.html#embedding-custom-non-visible-data-with-the-data-*-attributes "Embedding custom non-visible data with the data-* attributes"
diff --git a/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee b/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee
index 852587042c..b3448dabac 100644
--- a/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee
@@ -62,7 +62,7 @@ Rails.handleRemote = (e) ->
         fire(element, 'ajax:send', [xhr])
       else
         fire(element, 'ajax:stopped')
-        xhr.abort()
+        return false
     success: (args...) -> fire(element, 'ajax:success', args)
     error: (args...) -> fire(element, 'ajax:error', args)
     complete: (args...) -> fire(element, 'ajax:complete', args)
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
index a653d3af3d..cc0e037428 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
@@ -20,13 +20,12 @@ Rails.ajax = (options) ->
     else
       options.error?(response, xhr.statusText, xhr)
     options.complete?(xhr, xhr.statusText)
-  # Call beforeSend hook
-  options.beforeSend?(xhr, options)
-  # Send the request
+
+  if options.beforeSend? && !options.beforeSend(xhr, options)
+    return false
+
   if xhr.readyState is XMLHttpRequest.OPENED
     xhr.send(options.data)
-  else
-    fire(document, 'ajaxStop') # to be compatible with jQuery.ajax
 
 prepareOptions = (options) ->
   options.url = options.url or location.href
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee
index 6bef618147..3d3c5bb330 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee
@@ -5,6 +5,13 @@ m = Element.prototype.matches or
     Element.prototype.oMatchesSelector or
     Element.prototype.webkitMatchesSelector
 
+# Checks if the given native dom element matches the selector
+# element::
+#   native DOM element
+# selector::
+#   css selector string or
+#   a javascript object with `selector` and `exclude` properties
+#   Examples: "form", { selector: "form", exclude: "form[data-remote='true']"}
 Rails.matches = (element, selector) ->
   if selector.exclude?
     m.call(element, selector.selector) and not m.call(element, selector.exclude)
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee
index 8d3ff007ea..a2135c9851 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee
@@ -14,6 +14,13 @@ if typeof CustomEvent isnt 'function'
   CustomEvent.prototype = window.Event.prototype
 
 # Triggers a custom event on an element and returns false if the event result is false
+# obj::
+#   a native DOM element
+# name::
+#   string that corrspends to the event you want to trigger
+#   e.g. 'click', 'submit'
+# data::
+#   data you want to pass when you dispatch an event
 fire = Rails.fire = (obj, name, data) ->
   event = new CustomEvent(
     name,
@@ -31,6 +38,17 @@ Rails.stopEverything = (e) ->
   e.stopPropagation()
   e.stopImmediatePropagation()
 
+# Delegates events
+# to a specified parent `element`, which fires event `handler`
+# for the specified `selector` when an event of `eventType` is triggered
+# element::
+#   parent element that will listen for events e.g. document
+# selector::
+#   css selector; or an object that has `selector` and `exclude` properties (see: Rails.matches)
+# eventType::
+#   string representing the event e.g. 'submit', 'click'
+# handler::
+#   the event handler to be called
 Rails.delegate = (element, selector, eventType, handler) ->
   element.addEventListener eventType, (e) ->
     target = e.target
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee
index 5fa337b518..736cab08db 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee
@@ -10,7 +10,7 @@ Rails.serializeElement = (element, additionalParam) ->
   params = []
 
   inputs.forEach (input) ->
-    return unless input.name
+    return if !input.name || input.disabled
     if matches(input, 'select')
       toArray(input.options).forEach (option) ->
         params.push(name: input.name, value: option.value) if option.selected
diff --git a/actionview/lib/action_view.rb b/actionview/lib/action_view.rb
index 3c8a8488a5..9533f8d56c 100644
--- a/actionview/lib/action_view.rb
+++ b/actionview/lib/action_view.rb
@@ -25,7 +25,7 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "action_view/version"
+require "action_view/version"
 
 module ActionView
   extend ActiveSupport::Autoload
@@ -76,7 +76,6 @@ module ActionView
       autoload :MissingTemplate
       autoload :ActionViewError
       autoload :EncodingError
-      autoload :MissingRequestError
       autoload :TemplateError
       autoload :WrongEncodingError
     end
diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index 637c8e7708..d41fe2a608 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -3,11 +3,11 @@
 require "active_support/core_ext/module/attr_internal"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/ordered_options"
-require_relative "log_subscriber"
-require_relative "helpers"
-require_relative "context"
-require_relative "template"
-require_relative "lookup_context"
+require "action_view/log_subscriber"
+require "action_view/helpers"
+require "action_view/context"
+require "action_view/template"
+require "action_view/lookup_context"
 
 module ActionView #:nodoc:
   # = Action View Base
diff --git a/actionview/lib/action_view/context.rb b/actionview/lib/action_view/context.rb
index e1b02fbde4..665a9e3171 100644
--- a/actionview/lib/action_view/context.rb
+++ b/actionview/lib/action_view/context.rb
@@ -19,7 +19,6 @@ module ActionView
     attr_accessor :output_buffer, :view_flow
 
     # Prepares the context by setting the appropriate instance variables.
-    # :api: plugin
     def _prepare_context
       @view_flow     = OutputFlow.new
       @output_buffer = nil
@@ -29,7 +28,6 @@ module ActionView
     # Encapsulates the interaction with the view flow so it
     # returns the correct buffer on +yield+. This is usually
     # overwritten by helpers to add more behavior.
-    # :api: plugin
     def _layout_for(name = nil)
       name ||= :layout
       view_flow.get(name).html_safe
diff --git a/actionview/lib/action_view/dependency_tracker.rb b/actionview/lib/action_view/dependency_tracker.rb
index 02bd0545c2..182f6e2eef 100644
--- a/actionview/lib/action_view/dependency_tracker.rb
+++ b/actionview/lib/action_view/dependency_tracker.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "path_set"
+require "action_view/path_set"
 
 module ActionView
   class DependencyTracker # :nodoc:
diff --git a/actionview/lib/action_view/digestor.rb b/actionview/lib/action_view/digestor.rb
index e404ebb6b6..dfd62bdcfd 100644
--- a/actionview/lib/action_view/digestor.rb
+++ b/actionview/lib/action_view/digestor.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "dependency_tracker"
+require "action_view/dependency_tracker"
 require "monitor"
 
 module ActionView
diff --git a/actionview/lib/action_view/gem_version.rb b/actionview/lib/action_view/gem_version.rb
index ed92490be7..ff7f2bb853 100644
--- a/actionview/lib/action_view/gem_version.rb
+++ b/actionview/lib/action_view/gem_version.rb
@@ -10,7 +10,7 @@ module ActionView
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionview/lib/action_view/helpers/active_model_helper.rb b/actionview/lib/action_view/helpers/active_model_helper.rb
index f1ef715710..e41a95d2ce 100644
--- a/actionview/lib/action_view/helpers/active_model_helper.rb
+++ b/actionview/lib/action_view/helpers/active_model_helper.rb
@@ -17,8 +17,8 @@ module ActionView
         end
       end
 
-      def content_tag(*)
-        error_wrapping(super)
+      def content_tag(type, options, *)
+        select_markup_helper?(type) ? super : error_wrapping(super)
       end
 
       def tag(type, options, *)
@@ -43,6 +43,10 @@ module ActionView
           object.respond_to?(:errors) && object.errors.respond_to?(:[]) && error_message.present?
         end
 
+        def select_markup_helper?(type)
+          ["optgroup", "option"].include?(type)
+        end
+
         def tag_generate_errors?(options)
           options["type"] != "hidden"
         end
diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index bc2713d13e..da630129cb 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -2,8 +2,10 @@
 
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/hash/keys"
-require_relative "asset_url_helper"
-require_relative "tag_helper"
+require "active_support/core_ext/object/inclusion"
+require "active_support/core_ext/object/try"
+require "action_view/helpers/asset_url_helper"
+require "action_view/helpers/tag_helper"
 
 module ActionView
   # = Action View Asset Tag Helpers
@@ -37,6 +39,9 @@ module ActionView
       # When the Asset Pipeline is enabled, you can pass the name of your manifest as
       # source, and include other JavaScript or CoffeeScript files inside the manifest.
       #
+      # If the server supports Early Hints header links for these assets will be
+      # automatically pushed.
+      #
       # ==== Options
       #
       # When the last parameter is a hash you can add HTML attributes using that
@@ -77,12 +82,20 @@ module ActionView
       def javascript_include_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
-        sources.uniq.map { |source|
+        early_hints_links = []
+
+        sources_tags = sources.uniq.map { |source|
+          href = path_to_javascript(source, path_options)
+          early_hints_links << "<#{href}>; rel=preload; as=script"
           tag_options = {
-            "src" => path_to_javascript(source, path_options)
+            "src" => href
           }.merge!(options)
           content_tag("script".freeze, "", tag_options)
         }.join("\n").html_safe
+
+        request.send_early_hints("Link" => early_hints_links.join("\n")) if respond_to?(:request) && request
+
+        sources_tags
       end
 
       # Returns a stylesheet link tag for the sources specified as arguments. If
@@ -92,6 +105,9 @@ module ActionView
       # to "screen", so you must explicitly set it to "all" for the stylesheet(s) to
       # apply to all media types.
       #
+      # If the server supports Early Hints header links for these assets  will be
+      # automatically pushed.
+      #
       #   stylesheet_link_tag "style"
       #   # => <link href="/assets/style.css" media="screen" rel="stylesheet" />
       #
@@ -113,14 +129,22 @@ module ActionView
       def stylesheet_link_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "host", "skip_pipeline").symbolize_keys
-        sources.uniq.map { |source|
+        early_hints_links = []
+
+        sources_tags = sources.uniq.map { |source|
+          href = path_to_stylesheet(source, path_options)
+          early_hints_links << "<#{href}>; rel=preload; as=stylesheet"
           tag_options = {
             "rel" => "stylesheet",
             "media" => "screen",
-            "href" => path_to_stylesheet(source, path_options)
+            "href" => href
           }.merge!(options)
           tag(:link, tag_options)
         }.join("\n").html_safe
+
+        request.send_early_hints("Link" => early_hints_links.join("\n")) if respond_to?(:request) && request
+
+        sources_tags
       end
 
       # Returns a link tag that browsers and feed readers can use to auto-detect
@@ -199,6 +223,67 @@ module ActionView
         }.merge!(options.symbolize_keys))
       end
 
+      # Returns a link tag that browsers can use to preload the +source+.
+      # The +source+ can be the path of an resource managed by asset pipeline,
+      # a full path or an URI.
+      #
+      # ==== Options
+      #
+      # * <tt>:type</tt>  - Override the auto-generated mime type, defaults to the mime type for +source+ extension.
+      # * <tt>:as</tt>  - Override the auto-generated value for as attribute, calculated using +source+ extension and mime type.
+      # * <tt>:crossorigin</tt>  - Specify the crossorigin attribute, required to load cross-origin resources.
+      # * <tt>:nopush</tt>  - Specify if the use of server push is not desired for the resource. Defaults to +false+.
+      #
+      # ==== Examples
+      #
+      #   preload_link_tag("custom_theme.css")
+      #   # => <link rel="preload" href="/assets/custom_theme.css" as="style" type="text/css" />
+      #
+      #   preload_link_tag("/videos/video.webm")
+      #   # => <link rel="preload" href="/videos/video.mp4" as="video" type="video/webm" />
+      #
+      #   preload_link_tag(post_path(format: :json), as: "fetch")
+      #   # => <link rel="preload" href="/posts.json" as="fetch" type="application/json" />
+      #
+      #   preload_link_tag("worker.js", as: "worker")
+      #   # => <link rel="preload" href="/assets/worker.js" as="worker" type="text/javascript" />
+      #
+      #   preload_link_tag("//example.com/font.woff2")
+      #   # => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="anonymous"/>
+      #
+      #   preload_link_tag("//example.com/font.woff2", crossorigin: "use-credentials")
+      #   # => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="use-credentials" />
+      #
+      #   preload_link_tag("/media/audio.ogg", nopush: true)
+      #   # => <link rel="preload" href="/media/audio.ogg" as="audio" type="audio/ogg" />
+      #
+      def preload_link_tag(source, options = {})
+        href = asset_path(source, skip_pipeline: options.delete(:skip_pipeline))
+        extname = File.extname(source).downcase.delete(".")
+        mime_type = options.delete(:type) || Template::Types[extname].try(:to_s)
+        as_type = options.delete(:as) || resolve_link_as(extname, mime_type)
+        crossorigin = options.delete(:crossorigin)
+        crossorigin = "anonymous" if crossorigin == true || (crossorigin.blank? && as_type == "font")
+        nopush = options.delete(:nopush) || false
+
+        link_tag = tag.link({
+          rel: "preload",
+          href: href,
+          as: as_type,
+          type: mime_type,
+          crossorigin: crossorigin
+        }.merge!(options.symbolize_keys))
+
+        early_hints_link = "<#{href}>; rel=preload; as=#{as_type}"
+        early_hints_link += "; type=#{mime_type}" if mime_type
+        early_hints_link += "; crossorigin=#{crossorigin}" if crossorigin
+        early_hints_link += "; nopush" if nopush
+
+        request.send_early_hints("Link" => early_hints_link) if respond_to?(:request) && request
+
+        link_tag
+      end
+
       # Returns an HTML image tag for the +source+. The +source+ can be a full
       # path, a file or an Active Storage attachment.
       #
@@ -395,6 +480,18 @@ module ActionView
             raise ArgumentError, "Cannot pass a :size option with a :height or :width option"
           end
         end
+
+        def resolve_link_as(extname, mime_type)
+          if extname == "js"
+            "script"
+          elsif extname == "css"
+            "style"
+          elsif extname == "vtt"
+            "track"
+          elsif (type = mime_type.to_s.split("/")[0]) && type.in?(%w(audio video font))
+            type
+          end
+        end
     end
   end
 end
diff --git a/actionview/lib/action_view/helpers/asset_url_helper.rb b/actionview/lib/action_view/helpers/asset_url_helper.rb
index a4dcfc9a6c..f7690104ee 100644
--- a/actionview/lib/action_view/helpers/asset_url_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_url_helper.rb
@@ -324,7 +324,7 @@ module ActionView
       # Since +javascript_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   javascript_url "js/xmlhr.js", host: "http://stage.example.com" # => http://stage.example.com/assets/dir/xmlhr.js
+      #   javascript_url "js/xmlhr.js", host: "http://stage.example.com" # => http://stage.example.com/assets/js/xmlhr.js
       #
       def javascript_url(source, options = {})
         url_to_asset(source, { type: :javascript }.merge!(options))
@@ -351,7 +351,7 @@ module ActionView
       # Since +stylesheet_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   stylesheet_url "css/style.css", host: "http://stage.example.com" # => http://stage.example.com/css/style.css
+      #   stylesheet_url "css/style.css", host: "http://stage.example.com" # => http://stage.example.com/assets/css/style.css
       #
       def stylesheet_url(source, options = {})
         url_to_asset(source, { type: :stylesheet }.merge!(options))
@@ -381,7 +381,7 @@ module ActionView
       # Since +image_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   image_url "edit.png", host: "http://stage.example.com" # => http://stage.example.com/edit.png
+      #   image_url "edit.png", host: "http://stage.example.com" # => http://stage.example.com/assets/edit.png
       #
       def image_url(source, options = {})
         url_to_asset(source, { type: :image }.merge!(options))
@@ -407,7 +407,7 @@ module ActionView
       # Since +video_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   video_url "hd.avi", host: "http://stage.example.com" # => http://stage.example.com/hd.avi
+      #   video_url "hd.avi", host: "http://stage.example.com" # => http://stage.example.com/videos/hd.avi
       #
       def video_url(source, options = {})
         url_to_asset(source, { type: :video }.merge!(options))
@@ -433,7 +433,7 @@ module ActionView
       # Since +audio_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   audio_url "horse.wav", host: "http://stage.example.com" # => http://stage.example.com/horse.wav
+      #   audio_url "horse.wav", host: "http://stage.example.com" # => http://stage.example.com/audios/horse.wav
       #
       def audio_url(source, options = {})
         url_to_asset(source, { type: :audio }.merge!(options))
@@ -458,7 +458,7 @@ module ActionView
       # Since +font_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   font_url "font.ttf", host: "http://stage.example.com" # => http://stage.example.com/font.ttf
+      #   font_url "font.ttf", host: "http://stage.example.com" # => http://stage.example.com/fonts/font.ttf
       #
       def font_url(source, options = {})
         url_to_asset(source, { type: :font }.merge!(options))
diff --git a/actionview/lib/action_view/helpers/date_helper.rb b/actionview/lib/action_view/helpers/date_helper.rb
index 642bd0fec6..09040ccbc4 100644
--- a/actionview/lib/action_view/helpers/date_helper.rb
+++ b/actionview/lib/action_view/helpers/date_helper.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/date/conversions"
 require "active_support/core_ext/hash/slice"
diff --git a/actionview/lib/action_view/helpers/form_helper.rb b/actionview/lib/action_view/helpers/form_helper.rb
index 6702c65ccb..6185aa133f 100644
--- a/actionview/lib/action_view/helpers/form_helper.rb
+++ b/actionview/lib/action_view/helpers/form_helper.rb
@@ -1,12 +1,12 @@
 # frozen_string_literal: true
 
 require "cgi"
-require_relative "date_helper"
-require_relative "tag_helper"
-require_relative "form_tag_helper"
-require_relative "active_model_helper"
-require_relative "../model_naming"
-require_relative "../record_identifier"
+require "action_view/helpers/date_helper"
+require "action_view/helpers/tag_helper"
+require "action_view/helpers/form_tag_helper"
+require "action_view/helpers/active_model_helper"
+require "action_view/model_naming"
+require "action_view/record_identifier"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/string/output_safety"
@@ -478,6 +478,8 @@ module ActionView
 
       mattr_accessor :form_with_generates_remote_forms, default: true
 
+      mattr_accessor :form_with_generates_ids, default: false
+
       # Creates a form tag based on mixing URLs, scopes, or models.
       #
       #   # Using just a URL:
@@ -640,16 +642,6 @@ module ActionView
       #
       # Where <tt>@document = Document.find(params[:id])</tt>.
       #
-      # When using labels +form_with+ requires setting the id on the field being
-      # labelled:
-      #
-      #   <%= form_with(model: @post) do |form| %>
-      #     <%= form.label :title %>
-      #     <%= form.text_field :title, id: :post_title %>
-      #   <% end %>
-      #
-      # See +label+ for more on how the +for+ attribute is derived.
-      #
       # === Mixing with other form helpers
       #
       # While +form_with+ uses a FormBuilder object it's possible to mix and
@@ -746,7 +738,7 @@ module ActionView
       #   end
       def form_with(model: nil, scope: nil, url: nil, format: nil, **options)
         options[:allow_method_names_outside_object] = true
-        options[:skip_default_ids] = true
+        options[:skip_default_ids] = !form_with_generates_ids
 
         if model
           url ||= polymorphic_path(model, format: format)
@@ -1044,16 +1036,6 @@ module ActionView
       # or model is yielded, so any generated field names are prefixed with
       # either the passed scope or the scope inferred from the <tt>:model</tt>.
       #
-      # When using labels +fields+ requires setting the id on the field being
-      # labelled:
-      #
-      #   <%= fields :comment do |fields| %>
-      #     <%= fields.label :body %>
-      #     <%= fields.text_field :body, id: :comment_body %>
-      #   <% end %>
-      #
-      # See +label+ for more on how the +for+ attribute is derived.
-      #
       # === Mixing with other form helpers
       #
       # While +form_with+ uses a FormBuilder object it's possible to mix and
@@ -1072,7 +1054,7 @@ module ActionView
       # FormOptionsHelper#collection_select and DateHelper#datetime_select.
       def fields(scope = nil, model: nil, **options, &block)
         options[:allow_method_names_outside_object] = true
-        options[:skip_default_ids] = true
+        options[:skip_default_ids] = !form_with_generates_ids
 
         if model
           scope ||= model_name_from_record_or_class(model).param_key
@@ -1985,7 +1967,7 @@ module ActionView
       # See the docs for the <tt>ActionView::FormHelper.fields</tt> helper method.
       def fields(scope = nil, model: nil, **options, &block)
         options[:allow_method_names_outside_object] = true
-        options[:skip_default_ids] = true
+        options[:skip_default_ids] = !FormHelper.form_with_generates_ids
 
         convert_to_legacy_options(options)
 
diff --git a/actionview/lib/action_view/helpers/form_options_helper.rb b/actionview/lib/action_view/helpers/form_options_helper.rb
index 1517abfad0..02a44477c1 100644
--- a/actionview/lib/action_view/helpers/form_options_helper.rb
+++ b/actionview/lib/action_view/helpers/form_options_helper.rb
@@ -2,7 +2,7 @@
 
 require "cgi"
 require "erb"
-require_relative "form_helper"
+require "action_view/helpers/form_helper"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/array/wrap"
@@ -279,17 +279,17 @@ module ActionView
       # Finally, this method supports a <tt>:default</tt> option, which selects
       # a default ActiveSupport::TimeZone if the object's time zone is +nil+.
       #
-      #   time_zone_select( "user", "time_zone", nil, include_blank: true)
+      #   time_zone_select("user", "time_zone", nil, include_blank: true)
       #
-      #   time_zone_select( "user", "time_zone", nil, default: "Pacific Time (US & Canada)" )
+      #   time_zone_select("user", "time_zone", nil, default: "Pacific Time (US & Canada)")
       #
-      #   time_zone_select( "user", 'time_zone', ActiveSupport::TimeZone.us_zones, default: "Pacific Time (US & Canada)")
+      #   time_zone_select("user", 'time_zone', ActiveSupport::TimeZone.us_zones, default: "Pacific Time (US & Canada)")
       #
-      #   time_zone_select( "user", 'time_zone', [ ActiveSupport::TimeZone['Alaska'], ActiveSupport::TimeZone['Hawaii'] ])
+      #   time_zone_select("user", 'time_zone', [ ActiveSupport::TimeZone['Alaska'], ActiveSupport::TimeZone['Hawaii'] ])
       #
-      #   time_zone_select( "user", 'time_zone', /Australia/)
+      #   time_zone_select("user", 'time_zone', /Australia/)
       #
-      #   time_zone_select( "user", "time_zone", ActiveSupport::TimeZone.all.sort, model: ActiveSupport::TimeZone)
+      #   time_zone_select("user", "time_zone", ActiveSupport::TimeZone.all.sort, model: ActiveSupport::TimeZone)
       def time_zone_select(object, method, priority_zones = nil, options = {}, html_options = {})
         Tags::TimeZoneSelect.new(object, method, self, priority_zones, options, html_options).render
       end
diff --git a/actionview/lib/action_view/helpers/form_tag_helper.rb b/actionview/lib/action_view/helpers/form_tag_helper.rb
index 31a1f8be8c..e86e18dd78 100644
--- a/actionview/lib/action_view/helpers/form_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/form_tag_helper.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "cgi"
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/module/attribute_accessors"
 
@@ -115,7 +115,7 @@ module ActionView
       #   #    <option>Write</option></select>
       #
       #   select_tag "people", options_from_collection_for_select(@people, "id", "name"), include_blank: true
-      #   # => <select id="people" name="people"><option value=""></option><option value="1">David</option></select>
+      #   # => <select id="people" name="people"><option value="" label=" "></option><option value="1">David</option></select>
       #
       #   select_tag "people", options_from_collection_for_select(@people, "id", "name"), include_blank: "All"
       #   # => <select id="people" name="people"><option value="">All</option><option value="1">David</option></select>
@@ -394,7 +394,7 @@ module ActionView
       #   # => <input checked="checked" id="receive_updates_no" name="receive_updates" type="radio" value="no" />
       #
       #   radio_button_tag 'time_slot', "3:00 p.m.", false, disabled: true
-      #   # => <input disabled="disabled" id="time_slot_300_pm" name="time_slot" type="radio" value="3:00 p.m." />
+      #   # => <input disabled="disabled" id="time_slot_3:00_p.m." name="time_slot" type="radio" value="3:00 p.m." />
       #
       #   radio_button_tag 'color', "green", true, class: "color_input"
       #   # => <input checked="checked" class="color_input" id="color_green" name="color" type="radio" value="green" />
diff --git a/actionview/lib/action_view/helpers/javascript_helper.rb b/actionview/lib/action_view/helpers/javascript_helper.rb
index 11eefe0ee0..dd2cd57ac3 100644
--- a/actionview/lib/action_view/helpers/javascript_helper.rb
+++ b/actionview/lib/action_view/helpers/javascript_helper.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 
 module ActionView
   module Helpers #:nodoc:
diff --git a/actionview/lib/action_view/helpers/tag_helper.rb b/actionview/lib/action_view/helpers/tag_helper.rb
index a64d7e396e..a6cec3f69c 100644
--- a/actionview/lib/action_view/helpers/tag_helper.rb
+++ b/actionview/lib/action_view/helpers/tag_helper.rb
@@ -166,7 +166,7 @@ module ActionView
       # This may come in handy when using jQuery's HTML5-aware <tt>.data()</tt>
       # from 1.4.3.
       #
-      #   tag.div data: { city_state: %w( Chigaco IL ) }
+      #   tag.div data: { city_state: %w( Chicago IL ) }
       #   # => <div data-city-state="[&quot;Chicago&quot;,&quot;IL&quot;]"></div>
       #
       # The generated attributes are escaped by default. This can be disabled using
diff --git a/actionview/lib/action_view/helpers/tags/base.rb b/actionview/lib/action_view/helpers/tags/base.rb
index 8934a9894c..fed908fcdb 100644
--- a/actionview/lib/action_view/helpers/tags/base.rb
+++ b/actionview/lib/action_view/helpers/tags/base.rb
@@ -97,7 +97,7 @@ module ActionView
             index = name_and_id_index(options)
             options["name"] = options.fetch("name") { tag_name(options["multiple"], index) }
 
-            unless skip_default_ids?
+            if generate_ids?
               options["id"] = options.fetch("id") { tag_id(index) }
               if namespace = options.delete("namespace")
                 options["id"] = options["id"] ? "#{namespace}_#{options['id']}" : namespace
@@ -183,8 +183,8 @@ module ActionView
             end
           end
 
-          def skip_default_ids?
-            @skip_default_ids
+          def generate_ids?
+            !@skip_default_ids
           end
       end
     end
diff --git a/actionview/lib/action_view/helpers/tags/check_box.rb b/actionview/lib/action_view/helpers/tags/check_box.rb
index 6b34dfef90..4327e07cae 100644
--- a/actionview/lib/action_view/helpers/tags/check_box.rb
+++ b/actionview/lib/action_view/helpers/tags/check_box.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "checkable"
+require "action_view/helpers/tags/checkable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
index 91c1135d20..455442178e 100644
--- a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "collection_helpers"
+require "action_view/helpers/tags/collection_helpers"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
index 0b0482f74e..16d37134e5 100644
--- a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "collection_helpers"
+require "action_view/helpers/tags/collection_helpers"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/label.rb b/actionview/lib/action_view/helpers/tags/label.rb
index 56b48bbd62..02bd099784 100644
--- a/actionview/lib/action_view/helpers/tags/label.rb
+++ b/actionview/lib/action_view/helpers/tags/label.rb
@@ -75,10 +75,6 @@ module ActionView
           def render_component(builder)
             builder.translation
           end
-
-          def skip_default_ids?
-            false # The id is used as the `for` attribute.
-          end
       end
     end
   end
diff --git a/actionview/lib/action_view/helpers/tags/radio_button.rb b/actionview/lib/action_view/helpers/tags/radio_button.rb
index 3cfdcbea3f..621db2b1b5 100644
--- a/actionview/lib/action_view/helpers/tags/radio_button.rb
+++ b/actionview/lib/action_view/helpers/tags/radio_button.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "checkable"
+require "action_view/helpers/tags/checkable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/text_area.rb b/actionview/lib/action_view/helpers/tags/text_area.rb
index 9c162b59f5..4519082ff6 100644
--- a/actionview/lib/action_view/helpers/tags/text_area.rb
+++ b/actionview/lib/action_view/helpers/tags/text_area.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "placeholderable"
+require "action_view/helpers/tags/placeholderable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/text_field.rb b/actionview/lib/action_view/helpers/tags/text_field.rb
index 3553942048..d92967e212 100644
--- a/actionview/lib/action_view/helpers/tags/text_field.rb
+++ b/actionview/lib/action_view/helpers/tags/text_field.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "placeholderable"
+require "action_view/helpers/tags/placeholderable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/text_helper.rb b/actionview/lib/action_view/helpers/text_helper.rb
index 3044a2c0ef..84d38aa416 100644
--- a/actionview/lib/action_view/helpers/text_helper.rb
+++ b/actionview/lib/action_view/helpers/text_helper.rb
@@ -422,7 +422,7 @@ module ActionView
         def to_s
           value = @values[@index].to_s
           @index = next_index
-          return value
+          value
         end
 
         private
@@ -446,7 +446,7 @@ module ActionView
         # uses an instance variable of ActionView::Base.
         def get_cycle(name)
           @_cycles = Hash.new unless defined?(@_cycles)
-          return @_cycles[name]
+          @_cycles[name]
         end
 
         def set_cycle(name, cycle_object)
diff --git a/actionview/lib/action_view/helpers/translation_helper.rb b/actionview/lib/action_view/helpers/translation_helper.rb
index e663892592..1860bc4732 100644
--- a/actionview/lib/action_view/helpers/translation_helper.rb
+++ b/actionview/lib/action_view/helpers/translation_helper.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 require "active_support/core_ext/string/access"
 require "i18n/exceptions"
 
diff --git a/actionview/lib/action_view/helpers/url_helper.rb b/actionview/lib/action_view/helpers/url_helper.rb
index 2d5aac6dc7..889562c478 100644
--- a/actionview/lib/action_view/helpers/url_helper.rb
+++ b/actionview/lib/action_view/helpers/url_helper.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "javascript_helper"
+require "action_view/helpers/javascript_helper"
 require "active_support/core_ext/array/access"
 require "active_support/core_ext/hash/keys"
 require "active_support/core_ext/string/output_safety"
@@ -139,6 +139,11 @@ module ActionView
       #   link_to "Profiles", controller: "profiles"
       #   # => <a href="/profiles">Profiles</a>
       #
+      # When name is +nil+ the href is presented instead
+      #
+      #   link_to nil, "http://example.com"
+      #   # => <a href="http://www.example.com">http://www.example.com</a>
+      #
       # You can use a block as well if your link target is hard to fit into the name parameter. ERB example:
       #
       #   <%= link_to(@profile) do %>
@@ -589,10 +594,27 @@ module ActionView
         end
 
         def add_method_to_attributes!(html_options, method)
-          if method && method.to_s.downcase != "get".freeze && html_options["rel".freeze] !~ /nofollow/
-            html_options["rel".freeze] = "#{html_options["rel".freeze]} nofollow".lstrip
+          if method_not_get_method?(method) && html_options["rel"] !~ /nofollow/
+            if html_options["rel"].blank?
+              html_options["rel"] = "nofollow"
+            else
+              html_options["rel"] = "#{html_options["rel"]} nofollow"
+            end
           end
-          html_options["data-method".freeze] = method
+          html_options["data-method"] = method
+        end
+
+        STRINGIFIED_COMMON_METHODS = {
+          get:    "get",
+          delete: "delete",
+          patch:  "patch",
+          post:   "post",
+          put:    "put",
+        }.freeze
+
+        def method_not_get_method?(method)
+          return false unless method
+          (STRINGIFIED_COMMON_METHODS[method] || method.to_s.downcase) != "get"
         end
 
         def token_tag(token = nil, form_options: {})
diff --git a/actionview/lib/action_view/layouts.rb b/actionview/lib/action_view/layouts.rb
index b11ef6e133..3e6d352c15 100644
--- a/actionview/lib/action_view/layouts.rb
+++ b/actionview/lib/action_view/layouts.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "rendering"
+require "action_view/rendering"
 require "active_support/core_ext/module/redefine_method"
 
 module ActionView
diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index acc0f57f1d..0e56eca35c 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -3,7 +3,7 @@
 require "concurrent/map"
 require "active_support/core_ext/module/remove_method"
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "template/resolver"
+require "action_view/template/resolver"
 
 module ActionView
   # = Action View Lookup Context
diff --git a/actionview/lib/action_view/railtie.rb b/actionview/lib/action_view/railtie.rb
index b22347c55c..73dfb267bb 100644
--- a/actionview/lib/action_view/railtie.rb
+++ b/actionview/lib/action_view/railtie.rb
@@ -22,8 +22,15 @@ module ActionView
     initializer "action_view.form_with_generates_remote_forms" do |app|
       ActiveSupport.on_load(:action_view) do
         form_with_generates_remote_forms = app.config.action_view.delete(:form_with_generates_remote_forms)
-        unless form_with_generates_remote_forms.nil?
-          ActionView::Helpers::FormHelper.form_with_generates_remote_forms = form_with_generates_remote_forms
+        ActionView::Helpers::FormHelper.form_with_generates_remote_forms = form_with_generates_remote_forms
+      end
+    end
+
+    initializer "action_view.form_with_generates_ids" do |app|
+      ActiveSupport.on_load(:action_view) do
+        form_with_generates_ids = app.config.action_view.delete(:form_with_generates_ids)
+        unless form_with_generates_ids.nil?
+          ActionView::Helpers::FormHelper.form_with_generates_ids = form_with_generates_ids
         end
       end
     end
diff --git a/actionview/lib/action_view/record_identifier.rb b/actionview/lib/action_view/record_identifier.rb
index b34a793c89..1310a1ce0a 100644
--- a/actionview/lib/action_view/record_identifier.rb
+++ b/actionview/lib/action_view/record_identifier.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module"
-require_relative "model_naming"
+require "action_view/model_naming"
 
 module ActionView
   # RecordIdentifier encapsulates methods used by various ActionView helpers
diff --git a/actionview/lib/action_view/renderer/partial_renderer.rb b/actionview/lib/action_view/renderer/partial_renderer.rb
index beb0a18b65..5b40af4f2f 100644
--- a/actionview/lib/action_view/renderer/partial_renderer.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "partial_renderer/collection_caching"
+require "action_view/renderer/partial_renderer/collection_caching"
 
 module ActionView
   class PartialIteration
diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index 2648f9153f..4e5fdfbb2d 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "view_paths"
+require "action_view/view_paths"
 
 module ActionView
   # This is a class to fix I18n global state. Whenever you provide I18n.locale during a request,
@@ -75,8 +75,7 @@ module ActionView
     end
 
     # Returns an object that is able to render templates.
-    # :api: private
-    def view_renderer
+    def view_renderer # :nodoc:
       @_view_renderer ||= ActionView::Renderer.new(lookup_context)
     end
 
@@ -92,7 +91,6 @@ module ActionView
     private
 
       # Find and render a template based on the options given.
-      # :api: private
       def _render_template(options)
         variant = options.delete(:variant)
         assigns = options.delete(:assigns)
@@ -114,7 +112,6 @@ module ActionView
 
       # Normalize args by converting render "foo" to render :action => "foo" and
       # render "foo/bar" to render :template => "foo/bar".
-      # :api: private
       def _normalize_args(action = nil, options = {})
         options = super(action, options)
         case action
@@ -137,7 +134,6 @@ module ActionView
       end
 
       # Normalize options.
-      # :api: private
       def _normalize_options(options)
         options = super(options)
         if options[:partial] == true
diff --git a/actionview/lib/action_view/template/error.rb b/actionview/lib/action_view/template/error.rb
index 2b0b25817b..4e3c02e05e 100644
--- a/actionview/lib/action_view/template/error.rb
+++ b/actionview/lib/action_view/template/error.rb
@@ -10,9 +10,6 @@ module ActionView
   class EncodingError < StandardError #:nodoc:
   end
 
-  class MissingRequestError < StandardError #:nodoc:
-  end
-
   class WrongEncodingError < EncodingError #:nodoc:
     def initialize(string, encoding)
       @string, @encoding = string, encoding
diff --git a/actionview/lib/action_view/template/handlers/erb.rb b/actionview/lib/action_view/template/handlers/erb.rb
index c41de62e52..b7b749f9da 100644
--- a/actionview/lib/action_view/template/handlers/erb.rb
+++ b/actionview/lib/action_view/template/handlers/erb.rb
@@ -3,11 +3,8 @@
 module ActionView
   class Template
     module Handlers
-      autoload :Erubis, "action_view/template/handlers/erb/deprecated_erubis"
-
       class ERB
         autoload :Erubi, "action_view/template/handlers/erb/erubi"
-        autoload :Erubis, "action_view/template/handlers/erb/erubis"
 
         # Specify trim mode for the ERB compiler. Defaults to '-'.
         # See ERB documentation for suitable values.
diff --git a/actionview/lib/action_view/template/handlers/erb/deprecated_erubis.rb b/actionview/lib/action_view/template/handlers/erb/deprecated_erubis.rb
deleted file mode 100644
index 00c7d7cc7d..0000000000
--- a/actionview/lib/action_view/template/handlers/erb/deprecated_erubis.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-# frozen_string_literal: true
-
-::ActiveSupport::Deprecation.warn("ActionView::Template::Handlers::Erubis is deprecated and will be removed from Rails 5.2. Switch to ActionView::Template::Handlers::ERB::Erubi instead.")
-
-module ActionView
-  class Template
-    module Handlers
-      Erubis = ERB::Erubis
-    end
-  end
-end
diff --git a/actionview/lib/action_view/template/handlers/erb/erubis.rb b/actionview/lib/action_view/template/handlers/erb/erubis.rb
deleted file mode 100644
index dc3bf1ff27..0000000000
--- a/actionview/lib/action_view/template/handlers/erb/erubis.rb
+++ /dev/null
@@ -1,83 +0,0 @@
-# frozen_string_literal: true
-
-gem "erubis"
-require "erubis"
-
-module ActionView
-  class Template
-    module Handlers
-      class ERB
-        class Erubis < ::Erubis::Eruby
-          # :nodoc: all
-          def add_preamble(src)
-            @newline_pending = 0
-            src << "@output_buffer = output_buffer || ActionView::OutputBuffer.new;"
-          end
-
-          def add_text(src, text)
-            return if text.empty?
-
-            if text == "\n"
-              @newline_pending += 1
-            else
-              src << "@output_buffer.safe_append='"
-              src << "\n" * @newline_pending if @newline_pending > 0
-              src << escape_text(text)
-              src << "'.freeze;"
-
-              @newline_pending = 0
-            end
-          end
-
-          # Erubis toggles <%= and <%== behavior when escaping is enabled.
-          # We override to always treat <%== as escaped.
-          def add_expr(src, code, indicator)
-            case indicator
-            when "=="
-              add_expr_escaped(src, code)
-            else
-              super
-            end
-          end
-
-          BLOCK_EXPR = /\s*((\s+|\))do|\{)(\s*\|[^|]*\|)?\s*\Z/
-
-          def add_expr_literal(src, code)
-            flush_newline_if_pending(src)
-            if BLOCK_EXPR.match?(code)
-              src << "@output_buffer.append= " << code
-            else
-              src << "@output_buffer.append=(" << code << ");"
-            end
-          end
-
-          def add_expr_escaped(src, code)
-            flush_newline_if_pending(src)
-            if BLOCK_EXPR.match?(code)
-              src << "@output_buffer.safe_expr_append= " << code
-            else
-              src << "@output_buffer.safe_expr_append=(" << code << ");"
-            end
-          end
-
-          def add_stmt(src, code)
-            flush_newline_if_pending(src)
-            super
-          end
-
-          def add_postamble(src)
-            flush_newline_if_pending(src)
-            src << "@output_buffer.to_s"
-          end
-
-          def flush_newline_if_pending(src)
-            if @newline_pending > 0
-              src << "@output_buffer.safe_append='#{"\n" * @newline_pending}'.freeze;"
-              @newline_pending = 0
-            end
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/actionview/lib/action_view/template/resolver.rb b/actionview/lib/action_view/template/resolver.rb
index a58d375293..5a86f10973 100644
--- a/actionview/lib/action_view/template/resolver.rb
+++ b/actionview/lib/action_view/template/resolver.rb
@@ -3,7 +3,7 @@
 require "pathname"
 require "active_support/core_ext/class"
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "../template"
+require "action_view/template"
 require "thread"
 require "concurrent/map"
 
diff --git a/actionview/lib/action_view/test_case.rb b/actionview/lib/action_view/test_case.rb
index 93be2be2d1..e1cbae5845 100644
--- a/actionview/lib/action_view/test_case.rb
+++ b/actionview/lib/action_view/test_case.rb
@@ -270,7 +270,7 @@ module ActionView
         begin
           routes = @controller.respond_to?(:_routes) && @controller._routes
         rescue
-          # Dont call routes, if there is an error on _routes call
+          # Don't call routes, if there is an error on _routes call
         end
 
         if routes &&
@@ -286,7 +286,7 @@ module ActionView
         begin
           routes = @controller.respond_to?(:_routes) && @controller._routes
         rescue
-          # Dont call routes, if there is an error on _routes call
+          # Don't call routes, if there is an error on _routes call
         end
 
         routes &&
diff --git a/actionview/lib/action_view/testing/resolvers.rb b/actionview/lib/action_view/testing/resolvers.rb
index 92fdb24a5e..68186c3bf8 100644
--- a/actionview/lib/action_view/testing/resolvers.rb
+++ b/actionview/lib/action_view/testing/resolvers.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../template/resolver"
+require "action_view/template/resolver"
 
 module ActionView #:nodoc:
   # Use FixtureResolver in your tests to simulate the presence of files on the
diff --git a/actionview/package.json b/actionview/package.json
index 4cbf0207e5..787ae06208 100644
--- a/actionview/package.json
+++ b/actionview/package.json
@@ -1,6 +1,6 @@
 {
   "name": "rails-ujs",
-  "version": "5.2.0-alpha",
+  "version": "5.2.0-beta2",
   "description": "Ruby on Rails unobtrusive scripting adapter",
   "main": "lib/assets/compiled/rails-ujs.js",
   "files": [
diff --git a/actionview/test/abstract_unit.rb b/actionview/test/abstract_unit.rb
index c98270bd12..f20a66c2d2 100644
--- a/actionview/test/abstract_unit.rb
+++ b/actionview/test/abstract_unit.rb
@@ -26,14 +26,6 @@ require "active_record"
 
 require "pp" # require 'pp' early to prevent hidden_methods from not picking up the pretty-print methods until too late
 
-module Rails
-  class << self
-    def env
-      @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "test")
-    end
-  end
-end
-
 ActiveSupport::Dependencies.hook!
 
 Thread.abort_on_exception = true
@@ -110,12 +102,6 @@ module ActionDispatch
   end
 end
 
-module ActiveSupport
-  class TestCase
-    include ActionDispatch::DrawOnce
-  end
-end
-
 class RoutedRackApp
   attr_reader :routes
 
@@ -162,29 +148,6 @@ class ActionDispatch::IntegrationTest < ActiveSupport::TestCase
 
   self.app = build_app
 
-  # Stub Rails dispatcher so it does not get controller references and
-  # simply return the controller#action as Rack::Body.
-  class StubDispatcher < ::ActionDispatch::Routing::RouteSet::Dispatcher
-    private
-      def controller_reference(controller_param)
-        controller_param
-      end
-
-      def dispatch(controller, action, env)
-        [200, { "Content-Type" => "text/html" }, ["#{controller}##{action}"]]
-      end
-  end
-
-  def self.stub_controllers
-    old_dispatcher = ActionDispatch::Routing::RouteSet::Dispatcher
-    ActionDispatch::Routing::RouteSet.module_eval { remove_const :Dispatcher }
-    ActionDispatch::Routing::RouteSet.module_eval { const_set :Dispatcher, StubDispatcher }
-    yield ActionDispatch::Routing::RouteSet.new
-  ensure
-    ActionDispatch::Routing::RouteSet.module_eval { remove_const :Dispatcher }
-    ActionDispatch::Routing::RouteSet.module_eval { const_set :Dispatcher, old_dispatcher }
-  end
-
   def with_routing(&block)
     temporary_routes = ActionDispatch::Routing::RouteSet.new
     old_app, self.class.app = self.class.app, self.class.build_app(temporary_routes)
@@ -196,21 +159,6 @@ class ActionDispatch::IntegrationTest < ActiveSupport::TestCase
     self.class.app = old_app
     silence_warnings { Object.const_set(:SharedTestRoutes, old_routes) }
   end
-
-  def with_autoload_path(path)
-    path = File.join(File.expand_path("fixtures", __dir__), path)
-    if ActiveSupport::Dependencies.autoload_paths.include?(path)
-      yield
-    else
-      begin
-        ActiveSupport::Dependencies.autoload_paths << path
-        yield
-      ensure
-        ActiveSupport::Dependencies.autoload_paths.reject! { |p| p == path }
-        ActiveSupport::Dependencies.clear
-      end
-    end
-  end
 end
 
 ActionView::RoutingUrlFor.include(ActionDispatch::Routing::UrlFor)
@@ -274,6 +222,7 @@ module ActionDispatch
 end
 
 class ActiveSupport::TestCase
+  include ActionDispatch::DrawOnce
   include ActiveSupport::Testing::MethodCallAssertions
 
   # Skips the current run on Rubinius using Minitest::Assertions#skip
diff --git a/actionview/test/actionpack/abstract/abstract_controller_test.rb b/actionview/test/actionpack/abstract/abstract_controller_test.rb
index 468a6376c7..4d4e2b8ef2 100644
--- a/actionview/test/actionpack/abstract/abstract_controller_test.rb
+++ b/actionview/test/actionpack/abstract/abstract_controller_test.rb
@@ -236,7 +236,7 @@ module AbstractController
       end
     end
 
-    class RespondToActionController < AbstractController::Base;
+    class RespondToActionController < AbstractController::Base
       def index() self.response_body = "success" end
 
       def fail()  self.response_body = "fail"    end
diff --git a/actionview/test/activerecord/render_partial_with_record_identification_test.rb b/actionview/test/activerecord/render_partial_with_record_identification_test.rb
index 367d2c3174..3a698fa42e 100644
--- a/actionview/test/activerecord/render_partial_with_record_identification_test.rb
+++ b/actionview/test/activerecord/render_partial_with_record_identification_test.rb
@@ -17,21 +17,11 @@ class RenderPartialWithRecordIdentificationController < ActionController::Base
     render partial: Reply.base
   end
 
-  def render_with_has_many_through_association
-    @developer = Developer.first
-    render partial: @developer.topics
-  end
-
   def render_with_has_one_association
     @company = Company.find(1)
     render partial: @company.mascot
   end
 
-  def render_with_belongs_to_association
-    @reply = Reply.find(1)
-    render partial: @reply.topic
-  end
-
   def render_with_record
     @developer = Developer.first
     render partial: @developer
diff --git a/actionview/test/template/active_model_helper_test.rb b/actionview/test/template/active_model_helper_test.rb
index a929d8dc3d..36afed6dd6 100644
--- a/actionview/test/template/active_model_helper_test.rb
+++ b/actionview/test/template/active_model_helper_test.rb
@@ -6,7 +6,7 @@ class ActiveModelHelperTest < ActionView::TestCase
   tests ActionView::Helpers::ActiveModelHelper
 
   silence_warnings do
-    Post = Struct.new(:author_name, :body, :updated_at) do
+    Post = Struct.new(:author_name, :body, :category, :published, :updated_at) do
       include ActiveModel::Conversion
       include ActiveModel::Validations
 
@@ -22,10 +22,14 @@ class ActiveModelHelperTest < ActionView::TestCase
     @post = Post.new
     @post.errors[:author_name] << "can't be empty"
     @post.errors[:body] << "foo"
+    @post.errors[:category] << "must exist"
+    @post.errors[:published] << "must be accepted"
     @post.errors[:updated_at] << "bar"
 
     @post.author_name = ""
     @post.body        = "Back to the hill and over it again!"
+    @post.category    = "rails"
+    @post.published   = false
     @post.updated_at  = Date.new(2004, 6, 15)
   end
 
@@ -56,6 +60,25 @@ class ActiveModelHelperTest < ActionView::TestCase
     assert_dom_equal(expected_dom, select("post", "author_name", [:a, :b], prompt: "Choose one..."))
   end
 
+  def test_select_grouped_options_with_errors
+    grouped_options = [
+      ["A", [["A1"], ["A2"]]],
+      ["B", [["B1"], ["B2"]]],
+    ]
+
+    assert_dom_equal(
+      %(<div class="field_with_errors"><select name="post[category]" id="post_category"><optgroup label="A"><option value="A1">A1</option>\n<option value="A2">A2</option></optgroup><optgroup label="B"><option value="B1">B1</option>\n<option value="B2">B2</option></optgroup></select></div>),
+      select("post", "category", grouped_options)
+    )
+  end
+
+  def test_collection_select_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><select name="post[author_name]" id="post_author_name"><option value="a">a</option>\n<option value="b">b</option></select></div>),
+      collection_select("post", "author_name", [:a, :b], :to_s, :to_s)
+    )
+  end
+
   def test_date_select_with_errors
     assert_dom_equal(
       %(<div class="field_with_errors"><select id="post_updated_at_1i" name="post[updated_at(1i)]">\n<option selected="selected" value="2004">2004</option>\n<option value="2005">2005</option>\n</select>\n<input id="post_updated_at_2i" name="post[updated_at(2i)]" type="hidden" value="6" />\n<input id="post_updated_at_3i" name="post[updated_at(3i)]" type="hidden" value="1" />\n</div>),
@@ -77,6 +100,55 @@ class ActiveModelHelperTest < ActionView::TestCase
     )
   end
 
+  def test_label_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><label for="post_body">Body</label></div>),
+      label("post", "body")
+    )
+  end
+
+  def test_check_box_with_errors
+    assert_dom_equal(
+      %(<input name="post[published]" type="hidden" value="0" /><div class="field_with_errors"><input type="checkbox" value="1" name="post[published]" id="post_published" /></div>),
+      check_box("post", "published")
+    )
+  end
+
+  def test_check_boxes_with_errors
+    assert_dom_equal(
+      %(<input name="post[published]" type="hidden" value="0" /><div class="field_with_errors"><input type="checkbox" value="1" name="post[published]" id="post_published" /></div><input name="post[published]" type="hidden" value="0" /><div class="field_with_errors"><input type="checkbox" value="1" name="post[published]" id="post_published" /></div>),
+      check_box("post", "published") + check_box("post", "published")
+    )
+  end
+
+  def test_radio_button_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><input type="radio" value="rails" checked="checked" name="post[category]" id="post_category_rails" /></div>),
+      radio_button("post", "category", "rails")
+    )
+  end
+
+  def test_radio_buttons_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><input type="radio" value="rails" checked="checked" name="post[category]" id="post_category_rails" /></div><div class="field_with_errors"><input type="radio" value="java" name="post[category]" id="post_category_java" /></div>),
+      radio_button("post", "category", "rails") + radio_button("post", "category", "java")
+    )
+  end
+
+  def test_collection_check_boxes_with_errors
+    assert_dom_equal(
+      %(<input type="hidden" name="post[category][]" value="" /><div class="field_with_errors"><input type="checkbox" value="ruby" name="post[category][]" id="post_category_ruby" /></div><label for="post_category_ruby">ruby</label><div class="field_with_errors"><input type="checkbox" value="java" name="post[category][]" id="post_category_java" /></div><label for="post_category_java">java</label>),
+      collection_check_boxes("post", "category", [:ruby, :java], :to_s, :to_s)
+    )
+  end
+
+  def test_collection_radio_buttons_with_errors
+    assert_dom_equal(
+      %(<input type="hidden" name="post[category]" value="" /><div class="field_with_errors"><input type="radio" value="ruby" name="post[category]" id="post_category_ruby" /></div><label for="post_category_ruby">ruby</label><div class="field_with_errors"><input type="radio" value="java" name="post[category]" id="post_category_java" /></div><label for="post_category_java">java</label>),
+      collection_radio_buttons("post", "category", [:ruby, :java], :to_s, :to_s)
+    )
+  end
+
   def test_hidden_field_does_not_render_errors
     assert_dom_equal(
       %(<input id="post_author_name" name="post[author_name]" type="hidden" value="" />),
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 6645839f0e..284dacf2d4 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -19,6 +19,7 @@ class AssetTagHelperTest < ActionView::TestCase
       def ssl?() false end
       def host_with_port() "localhost" end
       def base_url() "http://www.example.com" end
+      def send_early_hints(links) end
     end.new
 
     @controller.request = @request
@@ -213,6 +214,17 @@ class AssetTagHelperTest < ActionView::TestCase
     %(favicon_link_tag 'mb-icon.png', :rel => 'apple-touch-icon', :type => 'image/png') => %(<link href="/images/mb-icon.png" rel="apple-touch-icon" type="image/png" />)
   }
 
+  PreloadLinkToTag = {
+    %(preload_link_tag '/styles/custom_theme.css') => %(<link rel="preload" href="/styles/custom_theme.css" as="style" type="text/css" />),
+    %(preload_link_tag '/videos/video.webm') => %(<link rel="preload" href="/videos/video.webm" as="video" type="video/webm" />),
+    %(preload_link_tag '/posts.json', as: 'fetch') => %(<link rel="preload" href="/posts.json" as="fetch" type="application/json" />),
+    %(preload_link_tag '/users', as: 'fetch', type: 'application/json') => %(<link rel="preload" href="/users" as="fetch" type="application/json" />),
+    %(preload_link_tag '//example.com/map?callback=initMap', as: 'fetch', type: 'application/javascript') => %(<link rel="preload" href="//example.com/map?callback=initMap" as="fetch" type="application/javascript" />),
+    %(preload_link_tag '//example.com/font.woff2') => %(<link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="anonymous"/>),
+    %(preload_link_tag '//example.com/font.woff2', crossorigin: 'use-credentials') => %(<link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="use-credentials" />),
+    %(preload_link_tag '/media/audio.ogg', nopush: true) => %(<link rel="preload" href="/media/audio.ogg" as="audio" type="audio/ogg" />)
+  }
+
   VideoPathToTag = {
     %(video_path("xml"))          => %(/videos/xml),
     %(video_path("xml.ogg"))      => %(/videos/xml.ogg),
@@ -305,6 +317,24 @@ class AssetTagHelperTest < ActionView::TestCase
     %(font_path("font.ttf?123")) => %(/fonts/font.ttf?123)
   }
 
+  FontUrlToTag = {
+    %(font_url("font.eot")) => %(http://www.example.com/fonts/font.eot),
+    %(font_url("font.eot#iefix")) => %(http://www.example.com/fonts/font.eot#iefix),
+    %(font_url("font.woff")) => %(http://www.example.com/fonts/font.woff),
+    %(font_url("font.ttf")) => %(http://www.example.com/fonts/font.ttf),
+    %(font_url("font.ttf?123")) => %(http://www.example.com/fonts/font.ttf?123),
+    %(font_url("font.ttf", host: "http://assets.example.com")) => %(http://assets.example.com/fonts/font.ttf)
+  }
+
+  UrlToFontToTag = {
+    %(url_to_font("font.eot")) => %(http://www.example.com/fonts/font.eot),
+    %(url_to_font("font.eot#iefix")) => %(http://www.example.com/fonts/font.eot#iefix),
+    %(url_to_font("font.woff")) => %(http://www.example.com/fonts/font.woff),
+    %(url_to_font("font.ttf")) => %(http://www.example.com/fonts/font.ttf),
+    %(url_to_font("font.ttf?123")) => %(http://www.example.com/fonts/font.ttf?123),
+    %(url_to_font("font.ttf", host: "http://assets.example.com")) => %(http://assets.example.com/fonts/font.ttf)
+  }
+
   def test_autodiscovery_link_tag_with_unknown_type_but_not_pass_type_option_key
     assert_raise(ArgumentError) do
       auto_discovery_link_tag(:xml)
@@ -421,6 +451,14 @@ class AssetTagHelperTest < ActionView::TestCase
     }
   end
 
+  def test_stylesheet_link_tag_without_request
+    @request = nil
+    assert_dom_equal(
+      %(<link rel="stylesheet" media="screen" href="/stylesheets/foo.css" />),
+      stylesheet_link_tag("foo.css")
+    )
+  end
+
   def test_stylesheet_link_tag_is_html_safe
     assert stylesheet_link_tag("dir/file").html_safe?
     assert stylesheet_link_tag("dir/other/file", "dir/file2").html_safe?
@@ -445,6 +483,11 @@ class AssetTagHelperTest < ActionView::TestCase
     assert_dom_equal %(<link href="//assets.example.com/stylesheets/wellington.css" media="screen" rel="stylesheet" />), stylesheet_link_tag("wellington")
   end
 
+  def test_javascript_include_tag_without_request
+    @request = nil
+    assert_dom_equal %(<script src="/javascripts/foo.js"></script>), javascript_include_tag("foo.js")
+  end
+
   def test_image_path
     ImagePathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
@@ -503,6 +546,10 @@ class AssetTagHelperTest < ActionView::TestCase
     FaviconLinkToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
 
+  def test_preload_link_tag
+    PreloadLinkToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
+  end
+
   def test_video_path
     VideoPathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
@@ -547,6 +594,14 @@ class AssetTagHelperTest < ActionView::TestCase
     FontPathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
 
+  def test_font_url
+    FontUrlToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
+  end
+
+  def test_url_to_font_alias_for_font_url
+    UrlToFontToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
+  end
+
   def test_video_audio_tag_does_not_modify_options
     options = { autoplay: true }
     video_tag("video", options)
@@ -627,7 +682,9 @@ class AssetTagHelperNonVhostTest < ActionView::TestCase
     @controller = BasicController.new
     @controller.config.relative_url_root = "/collaboration/hieraki"
 
-    @request = Struct.new(:protocol, :base_url).new("gopher://", "gopher://www.example.com")
+    @request = Struct.new(:protocol, :base_url) do
+      def send_early_hints(links); end
+    end.new("gopher://", "gopher://www.example.com")
     @controller.request = @request
   end
 
@@ -749,6 +806,23 @@ class AssetTagHelperNonVhostTest < ActionView::TestCase
   end
 end
 
+class AssetTagHelperWithoutRequestTest < ActionView::TestCase
+  tests ActionView::Helpers::AssetTagHelper
+
+  undef :request
+
+  def test_stylesheet_link_tag_without_request
+    assert_dom_equal(
+      %(<link rel="stylesheet" media="screen" href="/stylesheets/foo.css" />),
+      stylesheet_link_tag("foo.css")
+    )
+  end
+
+  def test_javascript_include_tag_without_request
+    assert_dom_equal %(<script src="/javascripts/foo.js"></script>), javascript_include_tag("foo.js")
+  end
+end
+
 class AssetUrlHelperControllerTest < ActionView::TestCase
   tests ActionView::Helpers::AssetUrlHelper
 
diff --git a/actionview/test/template/digestor_test.rb b/actionview/test/template/digestor_test.rb
index 928b1ac7dd..1bfa39a319 100644
--- a/actionview/test/template/digestor_test.rb
+++ b/actionview/test/template/digestor_test.rb
@@ -4,17 +4,6 @@ require "abstract_unit"
 require "fileutils"
 require "action_view/dependency_tracker"
 
-class FixtureTemplate
-  attr_reader :source, :handler
-
-  def initialize(template_path)
-    @source = File.read(template_path)
-    @handler = ActionView::Template.handler_for_extension(:erb)
-  rescue Errno::ENOENT
-    raise ActionView::MissingTemplate.new([], "", [], true, [])
-  end
-end
-
 class FixtureFinder < ActionView::LookupContext
   FIXTURES_DIR = File.expand_path("../fixtures/digestor", __dir__)
 
diff --git a/actionview/test/template/erb/deprecated_erubis_implementation_test.rb b/actionview/test/template/erb/deprecated_erubis_implementation_test.rb
deleted file mode 100644
index ea088e7cfc..0000000000
--- a/actionview/test/template/erb/deprecated_erubis_implementation_test.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-# frozen_string_literal: true
-
-require "abstract_unit"
-
-module ERBTest
-  class DeprecatedErubisImplementationTest < ActionView::TestCase
-    test "Erubis implementation is deprecated" do
-      assert_deprecated "ActionView::Template::Handlers::Erubis is deprecated and will be removed from Rails 5.2. Switch to ActionView::Template::Handlers::ERB::Erubi instead." do
-        assert_equal "ActionView::Template::Handlers::ERB::Erubis", ActionView::Template::Handlers::Erubis.to_s
-
-        assert_nothing_raised { Class.new(ActionView::Template::Handlers::Erubis) }
-      end
-    end
-  end
-end
diff --git a/actionview/test/template/form_helper/form_with_test.rb b/actionview/test/template/form_helper/form_with_test.rb
index c7d49070ce..0295ff627d 100644
--- a/actionview/test/template/form_helper/form_with_test.rb
+++ b/actionview/test/template/form_helper/form_with_test.rb
@@ -5,6 +5,15 @@ require "controller/fake_models"
 
 class FormWithTest < ActionView::TestCase
   include RenderERBUtils
+
+  setup do
+    @old_value = ActionView::Helpers::FormHelper.form_with_generates_ids
+    ActionView::Helpers::FormHelper.form_with_generates_ids = true
+  end
+
+  teardown do
+    ActionView::Helpers::FormHelper.form_with_generates_ids = @old_value
+  end
 end
 
 class FormWithActsLikeFormTagTest < FormWithTest
@@ -218,7 +227,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     @post = Post.new
     @comment = Comment.new
-    def @post.errors()
+    def @post.errors
       Class.new {
         def [](field); field == "author_name" ? ["can't be empty"] : [] end
         def empty?() false end
@@ -314,17 +323,45 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
       "<label for='post_title'>The Title</label>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[secret]' type='hidden' value='0' />" \
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />" \
+      "<select name='post[category]' id='post_category'><option value='animal'>animal</option>\n<option value='economy'>economy</option>\n<option value='sports'>sports</option></select>" \
+      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />" \
+      "<button name='button' type='submit'>Create post</button>" \
+      "<button name='button' type='submit'><span>Create post</span></button>"
+    end
+
+    assert_dom_equal expected, output_buffer
+  end
+
+  def test_form_with_not_outputting_ids
+    old_value = ActionView::Helpers::FormHelper.form_with_generates_ids
+    ActionView::Helpers::FormHelper.form_with_generates_ids = false
+
+    form_with(model: @post, id: "create-post") do |f|
+      concat f.label(:title) { "The Title" }
+      concat f.text_field(:title)
+      concat f.text_area(:body)
+      concat f.check_box(:secret)
+      concat f.select(:category, %w( animal economy sports ))
+      concat f.submit("Create post")
+    end
+
+    expected = whole_form("/posts/123", "create-post", method: "patch") do
+      "<label>The Title</label>" \
       "<input name='post[title]' type='text' value='Hello World' />" \
       "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
       "<input name='post[secret]' checked='checked' type='checkbox' value='1' />" \
       "<select name='post[category]'><option value='animal'>animal</option>\n<option value='economy'>economy</option>\n<option value='sports'>sports</option></select>" \
-      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />" \
-      "<button name='button' type='submit'>Create post</button>" \
-      "<button name='button' type='submit'><span>Create post</span></button>"
+      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />"
     end
 
     assert_dom_equal expected, output_buffer
+  ensure
+    ActionView::Helpers::FormHelper.form_with_generates_ids = old_value
   end
 
   def test_form_with_only_url_on_create
@@ -335,7 +372,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts") do
       '<label for="title">Label me</label>' \
-      '<input type="text" name="title">'
+      '<input type="text" name="title" id="title">'
     end
 
     assert_dom_equal expected, output_buffer
@@ -349,7 +386,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123") do
       '<label for="title">Label me</label>' \
-      '<input type="text" name="title">'
+      '<input type="text" name="title" id="title">'
     end
 
     assert_dom_equal expected, output_buffer
@@ -361,7 +398,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123") do
-      '<input type="text" name="no_model_to_back_this_badboy">'
+      '<input type="text" name="no_model_to_back_this_badboy" id="no_model_to_back_this_badboy" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -373,7 +410,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: :patch) do
-      '<input type="text" name="post[this_dont_exist_on_post]">'
+      '<input type="text" name="post[this_dont_exist_on_post]" id="post_this_dont_exist_on_post" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -391,8 +428,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end.new
 
     form_with(model: obj, scope: "other_name", url: "/", id: "edit-other-name") do |f|
-      assert_dom_equal '<input type="hidden" name="other_name[private_property]">', f.hidden_field(:private_property)
-      assert_dom_equal '<input type="hidden" name="other_name[protected_property]">', f.hidden_field(:protected_property)
+      assert_dom_equal '<input type="hidden" name="other_name[private_property]" id="other_name_private_property">', f.hidden_field(:private_property)
+      assert_dom_equal '<input type="hidden" name="other_name[protected_property]"  id="other_name_protected_property">', f.hidden_field(:protected_property)
     end
   end
 
@@ -459,7 +496,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       "<label for='post_active_false'>" \
       "<input checked='checked' name='post[active]' type='radio' value='false' id='post_active_false' />" \
       "false</label>" \
-      "<input name='post[id]' type='hidden' value='1' />"
+      "<input name='post[id]' type='hidden' value='1' id='post_id' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -557,7 +594,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       "<label for='post_tag_ids_3'>" \
       "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' id='post_tag_ids_3' />" \
       "Tag 3</label>" \
-      "<input name='post[id]' type='hidden' value='1' />"
+      "<input name='post[id]' type='hidden' value='1' id='post_id' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -587,7 +624,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", "create-post", method: "patch", multipart: true) do
-      "<input name='post[file]' type='file' />"
+      "<input name='post[file]' type='file' id='post_file' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -601,7 +638,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch", multipart: true) do
-      "<input name='post[comment][file]' type='file' />"
+      "<input name='post[comment][file]' type='file' id='post_comment_file'/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -640,7 +677,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/44", method: "patch") do
-      "<input name='post[title]' type='text' value='And his name will be forty and four.' />" \
+      "<input name='post[title]' type='text' value='And his name will be forty and four.' id='post_title' />" \
       "<input name='commit' data-disable-with='Edit post' type='submit' value='Edit post' />"
     end
 
@@ -658,10 +695,10 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
       "<label for='other_name_title' class='post_title'>Title</label>" \
-      "<input name='other_name[title]' value='Hello World' type='text' />" \
-      "<textarea name='other_name[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='other_name[title]' value='Hello World' type='text' id='other_name_title' />" \
+      "<textarea name='other_name[body]' id='other_name_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='other_name[secret]' value='0' type='hidden' />" \
-      "<input name='other_name[secret]' checked='checked' value='1' type='checkbox' />" \
+      "<input name='other_name[secret]' checked='checked' value='1' type='checkbox' id='other_name_secret' />" \
       "<input name='commit' value='Create post' data-disable-with='Create post' type='submit' />"
     end
 
@@ -676,10 +713,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "delete") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret'/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -693,10 +730,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "delete") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -710,7 +747,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/search", "search-post", method: "get") do
-      "<input name='post[title]' type='search' />"
+      "<input name='post[title]' type='search' id='post_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -724,10 +761,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -744,10 +781,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "patch", local: true) do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -761,7 +798,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", skip_enforcing_utf8: true) do
-      "<input name='post[title]' type='text' value='Hello World' />"
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -773,7 +810,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", skip_enforcing_utf8: false) do
-      "<input name='post[title]' type='text' value='Hello World' />"
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -787,10 +824,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -806,10 +843,10 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", method: "patch") do
       "<label for='post_123_title'>Title</label>" \
-      "<input name='post[123][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[123][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[123][title]' type='text' value='Hello World' id='post_123_title' />" \
+      "<textarea name='post[123][body]' id='post_123_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[123][secret]' type='hidden' value='0' />" \
-      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' id='post_123_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -823,10 +860,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[][title]' type='text' value='Hello World' id='post__title' />" \
+      "<textarea name='post[][body]' id='post__body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[][secret]' type='hidden' value='0' />" \
-      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' id='post__secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -841,7 +878,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", method: "patch") do
       "<div class='field_with_errors'><label for='post_author_name' class='label'>Author name</label></div>" \
-      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' /></div>" \
+      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' id='post_author_name' /></div>" \
       "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />"
     end
 
@@ -859,7 +896,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", method: "patch") do
       "<div class='field_with_errors'><label for='post_author_name' class='label'>Author name</label></div>" \
-      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' /></div>" \
+      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' id='post_author_name' /></div>" \
       "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />"
     end
 
@@ -947,7 +984,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: :patch) do
-      '<input type="text" name="post[comment][dont_exist_on_model]">'
+      '<input type="text" name="post[comment][dont_exist_on_model]" id="post_comment_dont_exist_on_model" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -967,7 +1004,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form do
-      '<input name="posts[post][0][comment][1][dont_exist_on_model]" type="text">'
+      '<input name="posts[post][0][comment][1][dont_exist_on_model]" type="text" id="posts_post_0_comment_1_dont_exist_on_model" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -982,7 +1019,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[comment][body]' type='text' value='Hello World' />"
+      "<input name='post[comment][body]' type='text' value='Hello World' id='post_comment_body' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1002,7 +1039,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form do
-      "<input name='posts[post][0][comment][1][name]' type='text' value='comment #1' />"
+      "<input name='posts[post][0][comment][1][name]' type='text' value='comment #1' id='posts_post_0_comment_1_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1017,8 +1054,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][title]' type='text' value='Hello World' />" \
-      "<input name='post[123][comment][][name]' type='text' value='new comment' />"
+      "<input name='post[123][title]' type='text' value='Hello World' id='post_123_title' />" \
+      "<input name='post[123][comment][][name]' type='text' value='new comment' id='post_123_comment__name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1033,8 +1070,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][title]' type='text' value='Hello World' />" \
-      "<input name='post[1][comment][1][name]' type='text' value='new comment' />"
+      "<input name='post[1][title]' type='text' value='Hello World' id='post_1_title' />" \
+      "<input name='post[1][comment][1][name]' type='text' value='new comment' id='post_1_comment_1_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1048,7 +1085,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][comment][title]' type='text' value='Hello World' />"
+      "<input name='post[1][comment][title]' type='text' value='Hello World' id='post_1_comment_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1062,7 +1099,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][comment][5][title]' type='text' value='Hello World' />"
+      "<input name='post[1][comment][5][title]' type='text' value='Hello World' id='post_1_comment_5_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1076,7 +1113,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][comment][title]' type='text' value='Hello World' />"
+      "<input name='post[123][comment][title]' type='text' value='Hello World' id='post_123_comment_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1090,7 +1127,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[comment][5][title]' type='radio' value='hello' />"
+      "<input name='post[comment][5][title]' type='radio' value='hello' id='post_comment_5_title_hello' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1104,7 +1141,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][comment][123][title]' type='text' value='Hello World' />"
+      "<input name='post[123][comment][123][title]' type='text' value='Hello World' id='post_123_comment_123_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1124,9 +1161,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][comment][5][title]' type='text' value='Hello World' />"
+      "<input name='post[123][comment][5][title]' type='text' value='Hello World' id='post_123_comment_5_title' />"
     end + whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][comment][123][title]' type='text' value='Hello World' />"
+      "<input name='post[1][comment][123][title]' type='text' value='Hello World' id='post_1_comment_123_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1143,8 +1180,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-        '<input name="post[author_attributes][name]" type="text" value="new author" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+        '<input name="post[author_attributes][name]" type="text" value="new author" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1170,9 +1207,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1189,9 +1226,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1208,8 +1245,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1226,8 +1263,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1244,9 +1281,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1264,9 +1301,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1285,11 +1322,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1312,11 +1349,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1339,10 +1376,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1365,11 +1402,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1388,11 +1425,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1412,11 +1449,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1435,9 +1472,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="new comment" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="new comment" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1456,10 +1493,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" id="post_comments_attributes_0_id"/>' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1474,7 +1511,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1491,11 +1528,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1512,11 +1549,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1547,11 +1584,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1570,10 +1607,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1590,8 +1627,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" />'
+      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" id="post_comments_attributes_abc_name" />' \
+      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" id="post_comments_attributes_abc_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1607,8 +1644,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" />'
+      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" id="post_comments_attributes_abc_name" />' \
+      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" id="post_comments_attributes_abc_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1630,8 +1667,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" />'
+      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" id="post_comments_attributes_abc_name" />' \
+      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" id="post_comments_attributes_abc_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1716,18 +1753,18 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][0][relevances_attributes][0][value]" type="text" value="commentrelevance #314" />' \
-      '<input name="post[comments_attributes][0][relevances_attributes][0][id]" type="hidden" value="314" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" />' \
-      '<input name="post[tags_attributes][0][value]" type="text" value="tag #123" />' \
-      '<input name="post[tags_attributes][0][relevances_attributes][0][value]" type="text" value="tagrelevance #3141" />' \
-      '<input name="post[tags_attributes][0][relevances_attributes][0][id]" type="hidden" value="3141" />' \
-      '<input name="post[tags_attributes][0][id]" type="hidden" value="123" />' \
-      '<input name="post[tags_attributes][1][value]" type="text" value="tag #456" />' \
-      '<input name="post[tags_attributes][1][relevances_attributes][0][value]" type="text" value="tagrelevance #31415" />' \
-      '<input name="post[tags_attributes][1][relevances_attributes][0][id]" type="hidden" value="31415" />' \
-      '<input name="post[tags_attributes][1][id]" type="hidden" value="456" />'
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][relevances_attributes][0][value]" type="text" value="commentrelevance #314" id="post_comments_attributes_0_relevances_attributes_0_value" />' \
+      '<input name="post[comments_attributes][0][relevances_attributes][0][id]" type="hidden" value="314" id="post_comments_attributes_0_relevances_attributes_0_id"/>' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" id="post_comments_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][0][value]" type="text" value="tag #123" id="post_tags_attributes_0_value"/>' \
+      '<input name="post[tags_attributes][0][relevances_attributes][0][value]" type="text" value="tagrelevance #3141" id="post_tags_attributes_0_relevances_attributes_0_value"/>' \
+      '<input name="post[tags_attributes][0][relevances_attributes][0][id]" type="hidden" value="3141" id="post_tags_attributes_0_relevances_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][0][id]" type="hidden" value="123" id="post_tags_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][1][value]" type="text" value="tag #456" id="post_tags_attributes_1_value"/>' \
+      '<input name="post[tags_attributes][1][relevances_attributes][0][value]" type="text" value="tagrelevance #31415" id="post_tags_attributes_1_relevances_attributes_0_value"/>' \
+      '<input name="post[tags_attributes][1][relevances_attributes][0][id]" type="hidden" value="31415" id="post_tags_attributes_1_relevances_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][1][id]" type="hidden" value="456" id="post_tags_attributes_1_id"/>'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1743,7 +1780,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[author_attributes][name]" type="text" value="hash backed author" />'
+      '<input name="post[author_attributes][name]" type="text" value="hash backed author" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1757,10 +1794,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1773,10 +1810,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[123][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[123][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[123][title]' type='text' value='Hello World' id='post_123_title' />" \
+      "<textarea name='post[123][body]' id='post_123_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[123][secret]' type='hidden' value='0' />" \
-      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' id='post_123_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1789,10 +1826,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[][title]' type='text' value='Hello World' id='post__title' />" \
+      "<textarea name='post[][body]' id='post__body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[][secret]' type='hidden' value='0' />" \
-      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' id='post__secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1805,10 +1842,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[abc][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[abc][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[abc][title]' type='text' value='Hello World' id='post_abc_title' />" \
+      "<textarea name='post[abc][body]' id='post_abc_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[abc][secret]' type='hidden' value='0' />" \
-      "<input name='post[abc][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[abc][secret]' checked='checked' type='checkbox' value='1' id='post_abc_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1821,10 +1858,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1837,10 +1874,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1852,7 +1889,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     assert_dom_equal "<label for=\"author_post_title\">Title</label>" \
-    "<input name='author[post][title]' type='text' value='Hello World' />",
+    "<input name='author[post][title]' type='text' value='Hello World' id='author_post_title' id='author_post_1_title' />",
       output_buffer
   end
 
@@ -1863,7 +1900,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     assert_dom_equal "<label for=\"author_post_1_title\">Title</label>" \
-      "<input name='author[post][1][title]' type='text' value='Hello World' />",
+      "<input name='author[post][1][title]' type='text' value='Hello World' id='author_post_1_title' />",
       output_buffer
   end
 
@@ -1882,10 +1919,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='parent_post[secret]' type='hidden' value='0' />" \
-      "<input name='parent_post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='parent_post[secret]' checked='checked' type='checkbox' value='1' id='parent_post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1902,9 +1939,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
-      "<input name='post[comment][name]' type='text' value='new comment' />"
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[comment][name]' type='text' value='new comment' id='post_comment_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1918,7 +1955,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[category][name]' type='text' />"
+      "<input name='post[category][name]' type='text' id='post_category_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1942,9 +1979,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>" \
-      "<label for='body'>Body:</label> <textarea name='post[body]'>\nBack to the hill and over it again!</textarea><br/>" \
-      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title'/><br/>" \
+      "<label for='body'>Body:</label> <textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea><br/>" \
+      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' /><br/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1961,9 +1998,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>" \
-      "<label for='body'>Body:</label> <textarea name='post[body]'>\nBack to the hill and over it again!</textarea><br/>" \
-      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>" \
+      "<label for='body'>Body:</label> <textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea><br/>" \
+      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' /><br/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1980,7 +2017,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1995,7 +2032,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       concat f.text_field(:title)
     end
 
-    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>"
+    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>"
 
     assert_dom_equal expected, output_buffer
   end
@@ -2007,7 +2044,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       concat f.text_field(:title)
     end
 
-    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>"
+    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>"
 
     assert_dom_equal expected, output_buffer
   end
@@ -2020,9 +2057,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>" \
-      "<label for='body'>Body:</label> <textarea name='post[body]'>\nBack to the hill and over it again!</textarea><br/>" \
-      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title'/><br/>" \
+      "<label for='body'>Body:</label> <textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea><br/>" \
+      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' /><br/>"
 
     assert_dom_equal expected, output_buffer
   end
diff --git a/actionview/test/template/form_helper_test.rb b/actionview/test/template/form_helper_test.rb
index ac64096908..e7b249cc9c 100644
--- a/actionview/test/template/form_helper_test.rb
+++ b/actionview/test/template/form_helper_test.rb
@@ -105,7 +105,7 @@ class FormHelperTest < ActionView::TestCase
 
     @post = Post.new
     @comment = Comment.new
-    def @post.errors()
+    def @post.errors
       Class.new {
         def [](field); field == "author_name" ? ["can't be empty"] : [] end
         def empty?() false end
@@ -1560,6 +1560,38 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_for_is_not_affected_by_form_with_generates_ids
+    old_value = ActionView::Helpers::FormHelper.form_with_generates_ids
+    ActionView::Helpers::FormHelper.form_with_generates_ids = false
+
+    form_for(@post, html: { id: "create-post" }) do |f|
+      concat f.label(:title) { "The Title" }
+      concat f.text_field(:title)
+      concat f.text_area(:body)
+      concat f.check_box(:secret)
+      concat f.submit("Create post")
+      concat f.button("Create post")
+      concat f.button {
+        concat content_tag(:span, "Create post")
+      }
+    end
+
+    expected = whole_form("/posts/123", "create-post", "edit_post", method: "patch") do
+      "<label for='post_title'>The Title</label>" \
+      "<input name='post[title]' type='text' id='post_title' value='Hello World' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[secret]' type='hidden' value='0' />" \
+      "<input name='post[secret]' checked='checked' type='checkbox' id='post_secret' value='1' />" \
+      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />" \
+      "<button name='button' type='submit'>Create post</button>" \
+      "<button name='button' type='submit'><span>Create post</span></button>"
+    end
+
+    assert_dom_equal expected, output_buffer
+  ensure
+    ActionView::Helpers::FormHelper.form_with_generates_ids = old_value
+  end
+
   def test_form_for_with_collection_radio_buttons
     post = Post.new
     def post.active; false; end
diff --git a/actionview/test/template/form_options_helper_test.rb b/actionview/test/template/form_options_helper_test.rb
index a66db2f3dc..f0eed1e290 100644
--- a/actionview/test/template/form_options_helper_test.rb
+++ b/actionview/test/template/form_options_helper_test.rb
@@ -1251,6 +1251,25 @@ class FormOptionsHelperTest < ActionView::TestCase
                  html
   end
 
+  def test_time_zone_select_with_priority_zones_and_errors
+    @firm = Firm.new("D")
+    @firm.extend ActiveModel::Validations
+    @firm.errors[:time_zone] << "invalid"
+    zones = [ ActiveSupport::TimeZone.new("A"), ActiveSupport::TimeZone.new("D") ]
+    html = time_zone_select("firm", "time_zone", zones)
+    assert_dom_equal "<div class=\"field_with_errors\">" \
+                 "<select id=\"firm_time_zone\" name=\"firm[time_zone]\">" \
+                 "<option value=\"A\">A</option>\n" \
+                 "<option value=\"D\" selected=\"selected\">D</option>" \
+                 "<option value=\"\" disabled=\"disabled\">-------------</option>\n" \
+                 "<option value=\"B\">B</option>\n" \
+                 "<option value=\"C\">C</option>\n" \
+                 "<option value=\"E\">E</option>" \
+                 "</select>" \
+                 "</div>",
+                 html
+  end
+
   def test_time_zone_select_with_default_time_zone_and_nil_value
     @firm = Firm.new()
     @firm.time_zone = nil
diff --git a/actionview/test/template/javascript_helper_test.rb b/actionview/test/template/javascript_helper_test.rb
index 4478c9f4ab..a72bc6c2fe 100644
--- a/actionview/test/template/javascript_helper_test.rb
+++ b/actionview/test/template/javascript_helper_test.rb
@@ -6,11 +6,15 @@ class JavaScriptHelperTest < ActionView::TestCase
   tests ActionView::Helpers::JavaScriptHelper
 
   attr_accessor :output_buffer
+  attr_reader :request
 
   setup do
     @old_escape_html_entities_in_json = ActiveSupport.escape_html_entities_in_json
     ActiveSupport.escape_html_entities_in_json = true
     @template = self
+    @request = Class.new do
+      def send_early_hints(links) end
+    end.new
   end
 
   def teardown
diff --git a/actionview/test/template/log_subscriber_test.rb b/actionview/test/template/log_subscriber_test.rb
index a4d89ba0d1..7f4fd25573 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -30,7 +30,7 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
     ActiveSupport::LogSubscriber.log_subscribers.clear
 
     # We need to undef `root`, RenderTestCases don't want this to be defined
-    Rails.instance_eval { undef :root } if @defined_root
+    Rails.instance_eval { undef :root } if defined?(@defined_root)
   end
 
   def set_logger(logger)
diff --git a/actionview/test/template/sanitize_helper_test.rb b/actionview/test/template/sanitize_helper_test.rb
index c7714cf205..0e690c82cb 100644
--- a/actionview/test/template/sanitize_helper_test.rb
+++ b/actionview/test/template/sanitize_helper_test.rb
@@ -21,8 +21,8 @@ class SanitizeHelperTest < ActionView::TestCase
 
   def test_should_sanitize_illegal_style_properties
     raw      = %(display:block; position:absolute; left:0; top:0; width:100%; height:100%; z-index:1; background-color:black; background-image:url(http://www.ragingplatypus.com/i/cam-full.jpg); background-x:center; background-y:center; background-repeat:repeat;)
-    expected = %(display: block; width: 100%; height: 100%; background-color: black; background-x: center; background-y: center;)
-    assert_equal expected, sanitize_css(raw)
+    expected = %r(\Adisplay:\s?block;\s?width:\s?100%;\s?height:\s?100%;\s?background-color:\s?black;\s?background-x:\s?center;\s?background-y:\s?center;\z)
+    assert_match expected, sanitize_css(raw)
   end
 
   def test_strip_tags
diff --git a/actionview/test/ujs/public/test/call-ajax.js b/actionview/test/ujs/public/test/call-ajax.js
new file mode 100644
index 0000000000..49e64cad5c
--- /dev/null
+++ b/actionview/test/ujs/public/test/call-ajax.js
@@ -0,0 +1,27 @@
+(function() {
+
+module('call-ajax', {
+  setup: function() {
+    $('#qunit-fixture')
+      .append($('<a />', { href: '#' }))
+  }
+})
+
+asyncTest('call ajax without "ajax:beforeSend"', 1, function() {
+
+  var link = $('#qunit-fixture a')
+  link.bindNative('click', function() {
+    Rails.ajax({
+      type: 'get',
+      url: '/',
+      success: function() {
+        ok(true, 'calling request in ajax:success')
+      }
+    })
+  })
+
+  link.triggerNative('click')
+  setTimeout(function() { start() }, 13)
+})
+
+})()
diff --git a/actionview/test/ujs/public/test/call-remote-callbacks.js b/actionview/test/ujs/public/test/call-remote-callbacks.js
index 707e21541d..48763f6301 100644
--- a/actionview/test/ujs/public/test/call-remote-callbacks.js
+++ b/actionview/test/ujs/public/test/call-remote-callbacks.js
@@ -12,34 +12,20 @@ module('call-remote-callbacks', {
     $(document).undelegate('form[data-remote]', 'ajax:send')
     $(document).undelegate('form[data-remote]', 'ajax:complete')
     $(document).undelegate('form[data-remote]', 'ajax:success')
-    $(document).unbind('ajaxStop')
     $(document).unbind('iframe:loading')
   }
 })
 
-function start_after_submit(form) {
-  form.bindNative('ajax:complete', function() {
-    ok(true, 'ajax:complete')
-    start()
-  })
-}
-
 function submit(fn) {
   var form = $('form')
-  start_after_submit(form)
 
   if (fn) fn(form)
   form.triggerNative('submit')
-}
 
-function submit_with_button(submit_button) {
-  var form = $('form')
-  start_after_submit(form)
-
-  submit_button.triggerNative('click')
+  setTimeout(function() { start() }, 13)
 }
 
-asyncTest('modifying form fields with "ajax:before" sends modified data in request', 4, function() {
+asyncTest('modifying form fields with "ajax:before" sends modified data in request', 3, function() {
   $('form[data-remote]')
     .append($('<input type="text" name="user_name" value="john">'))
     .append($('<input type="text" name="removed_user_name" value="john">'))
@@ -61,7 +47,7 @@ asyncTest('modifying form fields with "ajax:before" sends modified data in reque
   })
 })
 
-asyncTest('modifying data("type") with "ajax:before" requests new dataType in request', 2, function() {
+asyncTest('modifying data("type") with "ajax:before" requests new dataType in request', 1, function() {
   $('form[data-remote]').data('type', 'html')
     .bindNative('ajax:before', function() {
       this.setAttribute('data-type', 'xml')
@@ -74,7 +60,7 @@ asyncTest('modifying data("type") with "ajax:before" requests new dataType in re
   })
 })
 
-asyncTest('setting data("with-credentials",true) with "ajax:before" uses new setting in request', 2, function() {
+asyncTest('setting data("with-credentials",true) with "ajax:before" uses new setting in request', 1, function() {
   $('form[data-remote]').data('with-credentials', false)
     .bindNative('ajax:before', function() {
       this.setAttribute('data-with-credentials', true)
@@ -96,14 +82,11 @@ asyncTest('stopping the "ajax:beforeSend" event aborts the request', 1, function
     form.unbind('ajax:send').bindNative('ajax:send', function() {
       ok(false, 'ajax:send should not run')
     })
-    form.unbind('ajax:complete').bindNative('ajax:complete', function() {
-      ok(false, 'ajax:complete should not run')
-    })
-    form.bindNative('ajax:error', function(e, xhr, status, error) {
+    form.bindNative('ajax:error', function(e, response, status, xhr) {
       ok(false, 'ajax:error should not run')
     })
-    $(document).bindNative('ajaxStop', function() {
-      start()
+    form.bindNative('ajax:complete', function() {
+      ok(false, 'ajax:complete should not run')
     })
   })
 })
@@ -188,16 +171,13 @@ asyncTest('"ajax:beforeSend" can be observed and stopped with event delegation',
     form.unbind('ajax:send').bindNative('ajax:send', function() {
       ok(false, 'ajax:send should not run')
     })
-    form.unbind('ajax:complete').bindNative('ajax:complete', function() {
+    form.bindNative('ajax:complete', function() {
       ok(false, 'ajax:complete should not run')
     })
-    $(document).bindNative('ajaxStop', function() {
-      start()
-    })
   })
 })
 
-asyncTest('"ajax:beforeSend", "ajax:send", "ajax:success" and "ajax:complete" are triggered', 9, function() {
+asyncTest('"ajax:beforeSend", "ajax:send", "ajax:success" and "ajax:complete" are triggered', 8, function() {
   submit(function(form) {
     form.bindNative('ajax:beforeSend', function(e, xhr, settings) {
       ok(xhr.setRequestHeader, 'first argument to "ajax:beforeSend" should be an XHR object')
@@ -218,25 +198,25 @@ asyncTest('"ajax:beforeSend", "ajax:send", "ajax:success" and "ajax:complete" ar
   })
 })
 
-if(window.phantom !== undefined) {
-  asyncTest('"ajax:beforeSend", "ajax:send", "ajax:error" and "ajax:complete" are triggered on error', 7, function() {
-    submit(function(form) {
-      form.attr('action', '/error')
-      form.bindNative('ajax:beforeSend', function(arg) { ok(true, 'ajax:beforeSend') })
-      form.bindNative('ajax:send', function(arg) { ok(true, 'ajax:send') })
-      form.bindNative('ajax:error', function(e, xhr, status, error) {
-        ok(xhr.getResponseHeader, 'first argument to "ajax:error" should be an XHR object')
-        equal(status, 'error', 'second argument to ajax:error should be a status string')
-        // Firefox 8 returns "Forbidden " with trailing space
-        equal($.trim(error), 'Forbidden', 'third argument to ajax:error should be an HTTP status response')
-        // Opera returns "0" for HTTP code
-        equal(xhr.status, window.opera ? 0 : 403, 'status code should be 403')
-      })
+asyncTest('"ajax:beforeSend", "ajax:send", "ajax:error" and "ajax:complete" are triggered on error', 8, function() {
+  submit(function(form) {
+    form.attr('action', '/error')
+    form.bindNative('ajax:beforeSend', function(arg) { ok(true, 'ajax:beforeSend') })
+    form.bindNative('ajax:send', function(arg) { ok(true, 'ajax:send') })
+    form.bindNative('ajax:error', function(e, response, status, xhr) {
+      equal(response, '', 'first argument to ajax:error should be an HTTP status response')
+      equal(status, 'Forbidden', 'second argument to ajax:error should be a status string')
+      ok(xhr.getResponseHeader, 'third argument to "ajax:error" should be an XHR object')
+      // Opera returns "0" for HTTP code
+      equal(xhr.status, window.opera ? 0 : 403, 'status code should be 403')
+    })
+    form.bindNative('ajax:complete', function(e, xhr, status) {
+      ok(xhr.getResponseHeader, 'first argument to "ajax:complete" should be an XHR object')
+      equal(status, 'Forbidden', 'second argument to ajax:complete should be a status string')
     })
   })
-}
+})
 
-// IF THIS TEST IS FAILING, TRY INCREASING THE TIMEOUT AT THE BOTTOM TO > 100
 asyncTest('binding to ajax callbacks via .delegate() triggers handlers properly', 4, function() {
   $(document)
     .delegate('form[data-remote]', 'ajax:beforeSend', function() {
@@ -245,29 +225,15 @@ asyncTest('binding to ajax callbacks via .delegate() triggers handlers properly'
     .delegate('form[data-remote]', 'ajax:send', function() {
       ok(true, 'ajax:send handler is triggered')
     })
-    .delegate('form[data-remote]', 'ajax:complete', function() {
-      ok(true, 'ajax:complete handler is triggered')
-    })
     .delegate('form[data-remote]', 'ajax:success', function() {
       ok(true, 'ajax:success handler is triggered')
     })
-  $('form[data-remote]').triggerNative('submit')
-
-  setTimeout(function() {
-    start()
-  }, 63)
-})
-
-asyncTest('binding to ajax:send event to call jquery methods on ajax object', 2, function() {
-  $('form[data-remote]')
-    .bindNative('ajax:send', function(e, xhr) {
-      ok(true, 'event should fire')
-      equal(typeof(xhr.abort), 'function', 'event should pass jqXHR object')
-      xhr.abort()
+    .delegate('form[data-remote]', 'ajax:complete', function() {
+      ok(true, 'ajax:complete handler is triggered')
     })
-    .triggerNative('submit')
+  $('form[data-remote]').triggerNative('submit')
 
-  setTimeout(function() { start() }, 35)
+  setTimeout(function() { start() }, 13)
 })
 
 })()
diff --git a/actionview/test/ujs/public/test/data-remote.js b/actionview/test/ujs/public/test/data-remote.js
index 9bbefc18f2..cbbd4e6c92 100644
--- a/actionview/test/ujs/public/test/data-remote.js
+++ b/actionview/test/ujs/public/test/data-remote.js
@@ -191,9 +191,10 @@ asyncTest('submitting form with data-remote attribute should include inputs in a
     .triggerNative('submit')
 })
 
-asyncTest('submitting form with data-remote attribute submits input with matching [form] attribute', 5, function() {
+asyncTest('submitting form with data-remote attribute submits input with matching [form] attribute', 6, function() {
   $('#qunit-fixture')
     .append($('<input type="text" name="user_data" value="value1" form="my-remote-form">'))
+    .append($('<input type="text" name="user_email" value="from@example.com" disabled="disabled" form="my-remote-form">'))
 
   $('form[data-remote]')
     .bindNative('ajax:success', function(e, data, status, xhr) {
@@ -201,6 +202,7 @@ asyncTest('submitting form with data-remote attribute submits input with matchin
       App.assertRequestPath(data, '/echo')
       equal(data.params.user_name, 'john', 'ajax arguments should have key user_name with right value')
       equal(data.params.user_data, 'value1', 'ajax arguments should have key user_data with right value')
+      equal(data.params.user_email, undefined, 'ajax arguments should not have disabled field')
       App.assertPostRequest(data)
     })
     .bindNative('ajax:complete', function() { start() })
diff --git a/actionview/test/ujs/views/tests/index.html.erb b/actionview/test/ujs/views/tests/index.html.erb
index 8de6cd0695..6b16535216 100644
--- a/actionview/test/ujs/views/tests/index.html.erb
+++ b/actionview/test/ujs/views/tests/index.html.erb
@@ -1,6 +1,6 @@
 <% @title = "rails-ujs test" %>
 
-<%= test_to 'data-confirm', 'data-remote', 'data-disable', 'data-disable-with', 'call-remote', 'call-remote-callbacks', 'data-method', 'override', 'csrf-refresh', 'csrf-token' %>
+<%= test_to 'data-confirm', 'data-remote', 'data-disable', 'data-disable-with', 'call-remote', 'call-remote-callbacks', 'data-method', 'override', 'csrf-refresh', 'csrf-token', 'call-ajax' %>
 
 <h1 id="qunit-header"><%= @title %></h1>
 <h2 id="qunit-banner"></h2>
diff --git a/activejob/CHANGELOG.md b/activejob/CHANGELOG.md
index 32bf5a4b50..0867ba4e9b 100644
--- a/activejob/CHANGELOG.md
+++ b/activejob/CHANGELOG.md
@@ -13,12 +13,16 @@
         end
 
     *Aidan Haran*
-    
-*   Change logging instrumentation to log errors when a job raises an exception.
 
-    Fixes #26848.
+## Rails 5.2.0.beta2 (November 28, 2017) ##
 
-    *Steven Bull*
+*   No changes.
 
 
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Support redis-rb 4.0.
+
+    *Jeremy Daer*
+
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activejob/CHANGELOG.md) for previous changes.
diff --git a/activejob/README.md b/activejob/README.md
index 8a9a23929b..f1ebb76e08 100644
--- a/activejob/README.md
+++ b/activejob/README.md
@@ -100,7 +100,7 @@ The latest version of Active Job can be installed with RubyGems:
   $ gem install activejob
 ```
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/activejob
 
@@ -117,7 +117,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activejob/lib/active_job.rb b/activejob/lib/active_job.rb
index 56dab66544..1f5bd7b3e9 100644
--- a/activejob/lib/active_job.rb
+++ b/activejob/lib/active_job.rb
@@ -25,7 +25,7 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "active_job/version"
+require "active_job/version"
 require "global_id"
 
 module ActiveJob
diff --git a/activejob/lib/active_job/base.rb b/activejob/lib/active_job/base.rb
index 6af41260db..ae112abb2c 100644
--- a/activejob/lib/active_job/base.rb
+++ b/activejob/lib/active_job/base.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "core"
-require_relative "queue_adapter"
-require_relative "queue_name"
-require_relative "queue_priority"
-require_relative "enqueuing"
-require_relative "execution"
-require_relative "callbacks"
-require_relative "exceptions"
-require_relative "logging"
-require_relative "translation"
+require "active_job/core"
+require "active_job/queue_adapter"
+require "active_job/queue_name"
+require "active_job/queue_priority"
+require "active_job/enqueuing"
+require "active_job/execution"
+require "active_job/callbacks"
+require "active_job/exceptions"
+require "active_job/logging"
+require "active_job/translation"
 
 module ActiveJob #:nodoc:
   # = Active Job
diff --git a/activejob/lib/active_job/core.rb b/activejob/lib/active_job/core.rb
index c4e12fc518..879746fc01 100644
--- a/activejob/lib/active_job/core.rb
+++ b/activejob/lib/active_job/core.rb
@@ -97,17 +97,23 @@ module ActiveJob
     # ==== Examples
     #
     #    class DeliverWebhookJob < ActiveJob::Base
+    #      attr_writer :attempt_number
+    #
+    #      def attempt_number
+    #        @attempt_number ||= 0
+    #      end
+    #
     #      def serialize
-    #        super.merge('attempt_number' => (@attempt_number || 0) + 1)
+    #        super.merge('attempt_number' => attempt_number + 1)
     #      end
     #
     #      def deserialize(job_data)
     #        super
-    #        @attempt_number = job_data['attempt_number']
+    #        self.attempt_number = job_data['attempt_number']
     #      end
     #
-    #      rescue_from(TimeoutError) do |exception|
-    #        raise exception if @attempt_number > 5
+    #      rescue_from(Timeout::Error) do |exception|
+    #        raise exception if attempt_number > 5
     #        retry_job(wait: 10)
     #      end
     #    end
diff --git a/activejob/lib/active_job/enqueuing.rb b/activejob/lib/active_job/enqueuing.rb
index c0d016853c..53cb98fc71 100644
--- a/activejob/lib/active_job/enqueuing.rb
+++ b/activejob/lib/active_job/enqueuing.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "arguments"
+require "active_job/arguments"
 
 module ActiveJob
   # Provides behavior for enqueuing jobs.
diff --git a/activejob/lib/active_job/exceptions.rb b/activejob/lib/active_job/exceptions.rb
index 21d823eef9..ae700848d0 100644
--- a/activejob/lib/active_job/exceptions.rb
+++ b/activejob/lib/active_job/exceptions.rb
@@ -49,7 +49,7 @@ module ActiveJob
             retry_job wait: determine_delay(wait), queue: queue, priority: priority
           else
             if block_given?
-              yield self, exception
+              yield self, error
             else
               logger.error "Stopped retrying #{self.class} due to a #{exception}, which reoccurred on #{executions} attempts. The original exception was #{error.cause.inspect}."
               raise error
diff --git a/activejob/lib/active_job/execution.rb b/activejob/lib/active_job/execution.rb
index 85e050b489..d75be376ec 100644
--- a/activejob/lib/active_job/execution.rb
+++ b/activejob/lib/active_job/execution.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/rescuable"
-require_relative "arguments"
+require "active_job/arguments"
 
 module ActiveJob
   module Execution
diff --git a/activejob/lib/active_job/gem_version.rb b/activejob/lib/active_job/gem_version.rb
index 7ee61780e1..49dfd4095e 100644
--- a/activejob/lib/active_job/gem_version.rb
+++ b/activejob/lib/active_job/gem_version.rb
@@ -10,7 +10,7 @@ module ActiveJob
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb b/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb
index 1978179948..8eeef32b99 100644
--- a/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb
+++ b/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb
@@ -34,6 +34,10 @@ module ActiveJob
           @job_data = job_data
         end
 
+        def display_name
+          "#{job_data['job_class']} [#{job_data['job_id']}] from DelayedJob(#{job_data['queue_name']}) with arguments: #{job_data['arguments']}"
+        end
+
         def perform
           Base.execute(job_data)
         end
diff --git a/activejob/lib/rails/generators/job/templates/application_job.rb b/activejob/lib/rails/generators/job/templates/application_job.rb.tt
index f93745a31a..f93745a31a 100644
--- a/activejob/lib/rails/generators/job/templates/application_job.rb
+++ b/activejob/lib/rails/generators/job/templates/application_job.rb.tt
diff --git a/activejob/lib/rails/generators/job/templates/job.rb b/activejob/lib/rails/generators/job/templates/job.rb.tt
index 4ad2914a45..4ad2914a45 100644
--- a/activejob/lib/rails/generators/job/templates/job.rb
+++ b/activejob/lib/rails/generators/job/templates/job.rb.tt
diff --git a/activejob/test/cases/exceptions_test.rb b/activejob/test/cases/exceptions_test.rb
index 7b8f1dcca7..bc33d79f61 100644
--- a/activejob/test/cases/exceptions_test.rb
+++ b/activejob/test/cases/exceptions_test.rb
@@ -68,7 +68,7 @@ class ExceptionsTest < ActiveJob::TestCase
   test "custom handling of job that exceeds retry attempts" do
     perform_enqueued_jobs do
       RetryJob.perform_later "CustomCatchError", 6
-      assert_equal "Dealt with a job that failed to retry in a custom way after 6 attempts", JobBuffer.last_value
+      assert_equal "Dealt with a job that failed to retry in a custom way after 6 attempts. Message: CustomCatchError", JobBuffer.last_value
     end
   end
 
diff --git a/activejob/test/integration/queuing_test.rb b/activejob/test/integration/queuing_test.rb
index 0d8aa336a6..32ef485c45 100644
--- a/activejob/test/integration/queuing_test.rb
+++ b/activejob/test/integration/queuing_test.rb
@@ -45,6 +45,13 @@ class QueuingTest < ActiveSupport::TestCase
     end
   end
 
+  test "should supply a wrapped class name to DelayedJob" do
+    skip unless adapter_is?(:delayed_job)
+    ::HelloJob.perform_later
+    job = Delayed::Job.first
+    assert_match(/HelloJob \[[0-9a-f-]+\] from DelayedJob\(default\) with arguments: \[\]/, job.name)
+  end
+
   test "resque JobWrapper should have instance variable queue" do
     skip unless adapter_is?(:resque)
     job = ::HelloJob.set(wait: 5.seconds).perform_later
diff --git a/activejob/test/jobs/retry_job.rb b/activejob/test/jobs/retry_job.rb
index 2b22186f0a..82b80fe12b 100644
--- a/activejob/test/jobs/retry_job.rb
+++ b/activejob/test/jobs/retry_job.rb
@@ -18,7 +18,7 @@ class RetryJob < ActiveJob::Base
   retry_on ShortWaitTenAttemptsError, wait: 1.second, attempts: 10
   retry_on ExponentialWaitTenAttemptsError, wait: :exponentially_longer, attempts: 10
   retry_on CustomWaitTenAttemptsError, wait: ->(executions) { executions * 2 }, attempts: 10
-  retry_on(CustomCatchError) { |job, exception| JobBuffer.add("Dealt with a job that failed to retry in a custom way after #{job.arguments.second} attempts") }
+  retry_on(CustomCatchError) { |job, exception| JobBuffer.add("Dealt with a job that failed to retry in a custom way after #{job.arguments.second} attempts. Message: #{exception.message}") }
   discard_on DiscardableError
   discard_on(CustomDiscardableError) { |job, exception| JobBuffer.add("Dealt with a job that was discarded in a custom way") }
 
diff --git a/activejob/test/support/delayed_job/delayed/backend/test.rb b/activejob/test/support/delayed_job/delayed/backend/test.rb
index 4721c1cc17..9280a37a5c 100644
--- a/activejob/test/support/delayed_job/delayed/backend/test.rb
+++ b/activejob/test/support/delayed_job/delayed/backend/test.rb
@@ -77,7 +77,7 @@ module Delayed
             self.locked_by = worker
           end
 
-          return true
+          true
         end
 
         def self.db_time_now
diff --git a/activejob/test/support/integration/adapters/resque.rb b/activejob/test/support/integration/adapters/resque.rb
index 484b476567..2ed8302277 100644
--- a/activejob/test/support/integration/adapters/resque.rb
+++ b/activejob/test/support/integration/adapters/resque.rb
@@ -3,11 +3,12 @@
 module ResqueJobsManager
   def setup
     ActiveJob::Base.queue_adapter = :resque
-    Resque.redis = Redis::Namespace.new "active_jobs_int_test", redis: Redis.connect(url: "redis://:password@127.0.0.1:6379/12", thread_safe: true)
+    Resque.redis = Redis::Namespace.new "active_jobs_int_test", redis: Redis.new(url: "redis://127.0.0.1:6379/12", thread_safe: true)
     Resque.logger = Rails.logger
     unless can_run?
       puts "Cannot run integration tests for resque. To be able to run integration tests for resque you need to install and start redis.\n"
-      exit
+      status = ENV["CI"] ? false : true
+      exit status
     end
   end
 
@@ -41,11 +42,8 @@ module ResqueJobsManager
   end
 
   def can_run?
-    begin
-      Resque.redis.client.connect
-    rescue
-      return false
-    end
-    true
+    Resque.redis.ping == "PONG"
+  rescue
+    false
   end
 end
diff --git a/activejob/test/support/integration/adapters/sidekiq.rb b/activejob/test/support/integration/adapters/sidekiq.rb
index ceb7fb61f2..4b01a81ec5 100644
--- a/activejob/test/support/integration/adapters/sidekiq.rb
+++ b/activejob/test/support/integration/adapters/sidekiq.rb
@@ -5,20 +5,13 @@ require "sidekiq/api"
 require "sidekiq/testing"
 Sidekiq::Testing.disable!
 
-Sidekiq.configure_server do |config|
-  config.redis = { url: "redis://:password@127.0.0.1:6379/12" }
-end
-
-Sidekiq.configure_client do |config|
-  config.redis = { url: "redis://:password@127.0.0.1:6379/12" }
-end
-
 module SidekiqJobsManager
   def setup
     ActiveJob::Base.queue_adapter = :sidekiq
     unless can_run?
       puts "Cannot run integration tests for sidekiq. To be able to run integration tests for sidekiq you need to install and start redis.\n"
-      exit
+      status = ENV["CI"] ? false : true
+      exit status
     end
   end
 
diff --git a/activejob/test/support/integration/dummy_app_template.rb b/activejob/test/support/integration/dummy_app_template.rb
index ac382bd1b7..7ea78c3350 100644
--- a/activejob/test/support/integration/dummy_app_template.rb
+++ b/activejob/test/support/integration/dummy_app_template.rb
@@ -4,8 +4,6 @@ if ENV["AJ_ADAPTER"] == "delayed_job"
   generate "delayed_job:active_record", "--quiet"
 end
 
-rails_command("db:migrate")
-
 initializer "activejob.rb", <<-CODE
 require "#{File.expand_path("jobs_manager.rb",  __dir__)}"
 JobsManager.current_manager.setup
diff --git a/activejob/test/support/integration/helper.rb b/activejob/test/support/integration/helper.rb
index a058da141f..a02d874e2e 100644
--- a/activejob/test/support/integration/helper.rb
+++ b/activejob/test/support/integration/helper.rb
@@ -18,6 +18,7 @@ Rails::Generators::AppGenerator.start args
 require "#{dummy_app_path}/config/environment.rb"
 
 ActiveRecord::Migrator.migrations_paths = [ Rails.root.join("db/migrate").to_s ]
+ActiveRecord::Tasks::DatabaseTasks.migrate
 require "rails/test_help"
 
 Rails.backtrace_cleaner.remove_silencers!
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 048c43f2c4..2dfde11707 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,18 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Execute `ConfirmationValidator` validation when `_confirmation`'s value is `false`.
+
+    *bogdanvlviv*
+
+*   Allow passing a Proc or Symbol to length validator options.
+
+    *Matt Rohrer*
+
 *   Add method `#merge!` for `ActiveModel::Errors`.
 
     *Jahfer Husain*
diff --git a/activemodel/README.rdoc b/activemodel/README.rdoc
index 772df0f8f6..1aaf4813ea 100644
--- a/activemodel/README.rdoc
+++ b/activemodel/README.rdoc
@@ -251,11 +251,11 @@ Active Model is released under the MIT license:
 
 == Support
 
-API documentation is at
+API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index dfd9be34a9..a3884206a6 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -25,11 +25,13 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "active_model/version"
+require "active_model/version"
 
 module ActiveModel
   extend ActiveSupport::Autoload
 
+  autoload :Attribute
+  autoload :Attributes
   autoload :AttributeAssignment
   autoload :AttributeMethods
   autoload :BlockValidator, "active_model/validator"
@@ -45,6 +47,7 @@ module ActiveModel
   autoload :SecurePassword
   autoload :Serialization
   autoload :Translation
+  autoload :Type
   autoload :Validations
   autoload :Validator
 
diff --git a/activerecord/lib/active_record/attribute.rb b/activemodel/lib/active_model/attribute.rb
index fc474edc15..b75ff80b31 100644
--- a/activerecord/lib/active_record/attribute.rb
+++ b/activemodel/lib/active_model/attribute.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
-module ActiveRecord
+require "active_support/core_ext/object/duplicable"
+
+module ActiveModel
   class Attribute # :nodoc:
     class << self
       def from_database(name, value, type)
@@ -130,8 +132,6 @@ module ActiveRecord
       coder["value"] = value if defined?(@value)
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
     protected
 
       attr_reader :original_attribute
@@ -237,6 +237,7 @@ module ActiveRecord
           self.class.new(name, type)
         end
       end
+
       private_constant :FromDatabase, :FromUser, :Null, :Uninitialized, :WithCastValue
   end
 end
diff --git a/activerecord/lib/active_record/attribute/user_provided_default.rb b/activemodel/lib/active_model/attribute/user_provided_default.rb
index 690a931615..f274b687d4 100644
--- a/activerecord/lib/active_record/attribute/user_provided_default.rb
+++ b/activemodel/lib/active_model/attribute/user_provided_default.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../attribute"
+require "active_model/attribute"
 
-module ActiveRecord
+module ActiveModel
   class Attribute # :nodoc:
     class UserProvidedDefault < FromUser # :nodoc:
       def initialize(name, value, type, database_default)
@@ -22,8 +22,6 @@ module ActiveRecord
         self.class.new(name, user_provided_value, type, original_attribute)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :user_provided_value
diff --git a/activerecord/lib/active_record/attribute_mutation_tracker.rb b/activemodel/lib/active_model/attribute_mutation_tracker.rb
index 94bf641a5d..c67e1b809a 100644
--- a/activerecord/lib/active_record/attribute_mutation_tracker.rb
+++ b/activemodel/lib/active_model/attribute_mutation_tracker.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
-module ActiveRecord
+require "active_support/core_ext/hash/indifferent_access"
+
+module ActiveModel
   class AttributeMutationTracker # :nodoc:
     OPTION_NOT_GIVEN = Object.new
 
@@ -107,5 +109,8 @@ module ActiveRecord
 
     def original_value(*)
     end
+
+    def force_change(*)
+    end
   end
 end
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activemodel/lib/active_model/attribute_set.rb
index 492067e2b3..54a5dd4064 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activemodel/lib/active_model/attribute_set.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "attribute_set/builder"
-require_relative "attribute_set/yaml_encoder"
+require "active_model/attribute_set/builder"
+require "active_model/attribute_set/yaml_encoder"
 
-module ActiveRecord
+module ActiveModel
   class AttributeSet # :nodoc:
-    delegate :each_value, :fetch, to: :attributes
+    delegate :each_value, :fetch, :except, to: :attributes
 
     def initialize(attributes)
       @attributes = attributes
diff --git a/activerecord/lib/active_record/attribute_set/builder.rb b/activemodel/lib/active_model/attribute_set/builder.rb
index e3a9c7fdb3..758eb830fc 100644
--- a/activerecord/lib/active_record/attribute_set/builder.rb
+++ b/activemodel/lib/active_model/attribute_set/builder.rb
@@ -1,39 +1,34 @@
 # frozen_string_literal: true
 
-require_relative "../attribute"
+require "active_model/attribute"
 
-module ActiveRecord
+module ActiveModel
   class AttributeSet # :nodoc:
     class Builder # :nodoc:
-      attr_reader :types, :always_initialized, :default
+      attr_reader :types, :default_attributes
 
-      def initialize(types, always_initialized = nil, &default)
+      def initialize(types, default_attributes = {})
         @types = types
-        @always_initialized = always_initialized
-        @default = default
+        @default_attributes = default_attributes
       end
 
       def build_from_database(values = {}, additional_types = {})
-        if always_initialized && !values.key?(always_initialized)
-          values[always_initialized] = nil
-        end
-
-        attributes = LazyAttributeHash.new(types, values, additional_types, &default)
+        attributes = LazyAttributeHash.new(types, values, additional_types, default_attributes)
         AttributeSet.new(attributes)
       end
     end
   end
 
   class LazyAttributeHash # :nodoc:
-    delegate :transform_values, :each_key, :each_value, :fetch, to: :materialize
+    delegate :transform_values, :each_key, :each_value, :fetch, :except, to: :materialize
 
-    def initialize(types, values, additional_types, &default)
+    def initialize(types, values, additional_types, default_attributes)
       @types = types
       @values = values
       @additional_types = additional_types
       @materialized = false
       @delegate_hash = {}
-      @default = default || proc {}
+      @default_attributes = default_attributes
     end
 
     def key?(key)
@@ -92,11 +87,9 @@ module ActiveRecord
       @materialized = true
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
     protected
 
-      attr_reader :types, :values, :additional_types, :delegate_hash, :default
+      attr_reader :types, :values, :additional_types, :delegate_hash, :default_attributes
 
       def materialize
         unless @materialized
@@ -119,7 +112,12 @@ module ActiveRecord
         if value_present
           delegate_hash[name] = Attribute.from_database(name, value, type)
         elsif types.key?(name)
-          delegate_hash[name] = default.call(name) || Attribute.uninitialized(name, type)
+          attr = default_attributes[name]
+          if attr
+            delegate_hash[name] = attr.dup
+          else
+            delegate_hash[name] = Attribute.uninitialized(name, type)
+          end
         end
       end
   end
diff --git a/activerecord/lib/active_record/attribute_set/yaml_encoder.rb b/activemodel/lib/active_model/attribute_set/yaml_encoder.rb
index 9254ce16ab..4ea945b956 100644
--- a/activerecord/lib/active_record/attribute_set/yaml_encoder.rb
+++ b/activemodel/lib/active_model/attribute_set/yaml_encoder.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-module ActiveRecord
+module ActiveModel
   class AttributeSet
     # Attempts to do more intelligent YAML dumping of an
-    # ActiveRecord::AttributeSet to reduce the size of the resulting string
+    # ActiveModel::AttributeSet to reduce the size of the resulting string
     class YAMLEncoder # :nodoc:
       def initialize(default_types)
         @default_types = default_types
@@ -33,8 +33,6 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :default_types
diff --git a/activemodel/lib/active_model/attributes.rb b/activemodel/lib/active_model/attributes.rb
new file mode 100644
index 0000000000..cac461b549
--- /dev/null
+++ b/activemodel/lib/active_model/attributes.rb
@@ -0,0 +1,108 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/object/deep_dup"
+require "active_model/attribute_set"
+require "active_model/attribute/user_provided_default"
+
+module ActiveModel
+  module Attributes #:nodoc:
+    extend ActiveSupport::Concern
+    include ActiveModel::AttributeMethods
+
+    included do
+      attribute_method_suffix "="
+      class_attribute :attribute_types, :_default_attributes, instance_accessor: false
+      self.attribute_types = Hash.new(Type.default_value)
+      self._default_attributes = AttributeSet.new({})
+    end
+
+    module ClassMethods
+      def attribute(name, type = Type::Value.new, **options)
+        name = name.to_s
+        if type.is_a?(Symbol)
+          type = ActiveModel::Type.lookup(type, **options.except(:default))
+        end
+        self.attribute_types = attribute_types.merge(name => type)
+        define_default_attribute(name, options.fetch(:default, NO_DEFAULT_PROVIDED), type)
+        define_attribute_methods(name)
+      end
+
+      private
+
+        def define_method_attribute=(name)
+          safe_name = name.unpack("h*".freeze).first
+          ActiveModel::AttributeMethods::AttrNames.set_name_cache safe_name, name
+
+          generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1
+            def __temp__#{safe_name}=(value)
+              name = ::ActiveModel::AttributeMethods::AttrNames::ATTR_#{safe_name}
+              write_attribute(name, value)
+            end
+            alias_method #{(name + '=').inspect}, :__temp__#{safe_name}=
+            undef_method :__temp__#{safe_name}=
+          STR
+        end
+
+        NO_DEFAULT_PROVIDED = Object.new # :nodoc:
+        private_constant :NO_DEFAULT_PROVIDED
+
+        def define_default_attribute(name, value, type)
+          self._default_attributes = _default_attributes.deep_dup
+          if value == NO_DEFAULT_PROVIDED
+            default_attribute = _default_attributes[name].with_type(type)
+          else
+            default_attribute = Attribute::UserProvidedDefault.new(
+              name,
+              value,
+              type,
+              _default_attributes.fetch(name.to_s) { nil },
+            )
+          end
+          _default_attributes[name] = default_attribute
+        end
+    end
+
+    def initialize(*)
+      @attributes = self.class._default_attributes.deep_dup
+      super
+    end
+
+    private
+
+      def write_attribute(attr_name, value)
+        name = if self.class.attribute_alias?(attr_name)
+          self.class.attribute_alias(attr_name).to_s
+        else
+          attr_name.to_s
+        end
+
+        @attributes.write_from_user(name, value)
+        value
+      end
+
+      def attribute(attr_name)
+        name = if self.class.attribute_alias?(attr_name)
+          self.class.attribute_alias(attr_name).to_s
+        else
+          attr_name.to_s
+        end
+        @attributes.fetch_value(name)
+      end
+
+      # Handle *= for method_missing.
+      def attribute=(attribute_name, value)
+        write_attribute(attribute_name, value)
+      end
+  end
+
+  module AttributeMethods #:nodoc:
+    AttrNames = Module.new {
+      def self.set_name_cache(name, value)
+        const_name = "ATTR_#{name}"
+        unless const_defined? const_name
+          const_set const_name, value.dup.freeze
+        end
+      end
+    }
+  end
+end
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 943db0ab52..d2ebd18107 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -2,6 +2,7 @@
 
 require "active_support/hash_with_indifferent_access"
 require "active_support/core_ext/object/duplicable"
+require "active_model/attribute_mutation_tracker"
 
 module ActiveModel
   # == Active \Model \Dirty
@@ -130,6 +131,24 @@ module ActiveModel
       attribute_method_affix prefix: "restore_", suffix: "!"
     end
 
+    def initialize_dup(other) # :nodoc:
+      super
+      if self.class.respond_to?(:_default_attributes)
+        @attributes = self.class._default_attributes.map do |attr|
+          attr.with_value_from_user(@attributes.fetch_value(attr.name))
+        end
+      end
+      @mutations_from_database = nil
+    end
+
+    def changes_applied # :nodoc:
+      @previously_changed = changes
+      @mutations_before_last_save = mutations_from_database
+      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
+      forget_attribute_assignments
+      @mutations_from_database = nil
+    end
+
     # Returns +true+ if any of the attributes have unsaved changes, +false+ otherwise.
     #
     #   person.changed? # => false
@@ -148,6 +167,60 @@ module ActiveModel
       changed_attributes.keys
     end
 
+    # Handles <tt>*_changed?</tt> for +method_missing+.
+    def attribute_changed?(attr, from: OPTION_NOT_GIVEN, to: OPTION_NOT_GIVEN) # :nodoc:
+      !!changes_include?(attr) &&
+        (to == OPTION_NOT_GIVEN || to == _read_attribute(attr)) &&
+        (from == OPTION_NOT_GIVEN || from == changed_attributes[attr])
+    end
+
+    # Handles <tt>*_was</tt> for +method_missing+.
+    def attribute_was(attr) # :nodoc:
+      attribute_changed?(attr) ? changed_attributes[attr] : _read_attribute(attr)
+    end
+
+    # Handles <tt>*_previously_changed?</tt> for +method_missing+.
+    def attribute_previously_changed?(attr) #:nodoc:
+      previous_changes_include?(attr)
+    end
+
+    # Restore all previous data of the provided attributes.
+    def restore_attributes(attributes = changed)
+      attributes.each { |attr| restore_attribute! attr }
+    end
+
+    # Clears all dirty data: current changes and previous changes.
+    def clear_changes_information
+      @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
+      @mutations_before_last_save = nil
+      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
+      forget_attribute_assignments
+      @mutations_from_database = nil
+    end
+
+    def clear_attribute_changes(attr_names)
+      attributes_changed_by_setter.except!(*attr_names)
+      attr_names.each do |attr_name|
+        clear_attribute_change(attr_name)
+      end
+    end
+
+    # Returns a hash of the attributes with unsaved changes indicating their original
+    # values like <tt>attr => original value</tt>.
+    #
+    #   person.name # => "bob"
+    #   person.name = 'robert'
+    #   person.changed_attributes # => {"name" => "bob"}
+    def changed_attributes
+      # This should only be set by methods which will call changed_attributes
+      # multiple times when it is known that the computed value cannot change.
+      if defined?(@cached_changed_attributes)
+        @cached_changed_attributes
+      else
+        attributes_changed_by_setter.reverse_merge(mutations_from_database.changed_values).freeze
+      end
+    end
+
     # Returns a hash of changed attributes indicating their original
     # and new values like <tt>attr => [original value, new value]</tt>.
     #
@@ -155,7 +228,9 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changes # => { "name" => ["bill", "bob"] }
     def changes
-      ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
+      cache_changed_attributes do
+        ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
+      end
     end
 
     # Returns a hash of attributes that were changed before the model was saved.
@@ -166,45 +241,51 @@ module ActiveModel
     #   person.previous_changes # => {"name" => ["bob", "robert"]}
     def previous_changes
       @previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new
+      @previously_changed.merge(mutations_before_last_save.changes)
     end
 
-    # Returns a hash of the attributes with unsaved changes indicating their original
-    # values like <tt>attr => original value</tt>.
-    #
-    #   person.name # => "bob"
-    #   person.name = 'robert'
-    #   person.changed_attributes # => {"name" => "bob"}
-    def changed_attributes
-      @changed_attributes ||= ActiveSupport::HashWithIndifferentAccess.new
+    def attribute_changed_in_place?(attr_name) # :nodoc:
+      mutations_from_database.changed_in_place?(attr_name)
     end
 
-    # Handles <tt>*_changed?</tt> for +method_missing+.
-    def attribute_changed?(attr, from: OPTION_NOT_GIVEN, to: OPTION_NOT_GIVEN) # :nodoc:
-      !!changes_include?(attr) &&
-        (to == OPTION_NOT_GIVEN || to == _read_attribute(attr)) &&
-        (from == OPTION_NOT_GIVEN || from == changed_attributes[attr])
-    end
+    private
+      def clear_attribute_change(attr_name)
+        mutations_from_database.forget_change(attr_name)
+      end
 
-    # Handles <tt>*_was</tt> for +method_missing+.
-    def attribute_was(attr) # :nodoc:
-      attribute_changed?(attr) ? changed_attributes[attr] : _read_attribute(attr)
-    end
+      def mutations_from_database
+        unless defined?(@mutations_from_database)
+          @mutations_from_database = nil
+        end
+        @mutations_from_database ||= if defined?(@attributes)
+          ActiveModel::AttributeMutationTracker.new(@attributes)
+        else
+          NullMutationTracker.instance
+        end
+      end
 
-    # Handles <tt>*_previously_changed?</tt> for +method_missing+.
-    def attribute_previously_changed?(attr) #:nodoc:
-      previous_changes_include?(attr)
-    end
+      def forget_attribute_assignments
+        @attributes = @attributes.map(&:forgetting_assignment) if defined?(@attributes)
+      end
 
-    # Restore all previous data of the provided attributes.
-    def restore_attributes(attributes = changed)
-      attributes.each { |attr| restore_attribute! attr }
-    end
+      def mutations_before_last_save
+        @mutations_before_last_save ||= ActiveModel::NullMutationTracker.instance
+      end
 
-    private
+      def cache_changed_attributes
+        @cached_changed_attributes = changed_attributes
+        yield
+      ensure
+        clear_changed_attributes_cache
+      end
+
+      def clear_changed_attributes_cache
+        remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
+      end
 
       # Returns +true+ if attr_name is changed, +false+ otherwise.
       def changes_include?(attr_name)
-        attributes_changed_by_setter.include?(attr_name)
+        attributes_changed_by_setter.include?(attr_name) || mutations_from_database.changed?(attr_name)
       end
       alias attribute_changed_by_setter? changes_include?
 
@@ -214,18 +295,6 @@ module ActiveModel
         previous_changes.include?(attr_name)
       end
 
-      # Removes current changes and makes them accessible through +previous_changes+.
-      def changes_applied # :doc:
-        @previously_changed = changes
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-      end
-
-      # Clears all dirty data: current changes and previous changes.
-      def clear_changes_information # :doc:
-        @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-      end
-
       # Handles <tt>*_change</tt> for +method_missing+.
       def attribute_change(attr)
         [changed_attributes[attr], _read_attribute(attr)] if attribute_changed?(attr)
@@ -238,15 +307,16 @@ module ActiveModel
 
       # Handles <tt>*_will_change!</tt> for +method_missing+.
       def attribute_will_change!(attr)
-        return if attribute_changed?(attr)
+        unless attribute_changed?(attr)
+          begin
+            value = _read_attribute(attr)
+            value = value.duplicable? ? value.clone : value
+          rescue TypeError, NoMethodError
+          end
 
-        begin
-          value = _read_attribute(attr)
-          value = value.duplicable? ? value.clone : value
-        rescue TypeError, NoMethodError
+          set_attribute_was(attr, value)
         end
-
-        set_attribute_was(attr, value)
+        mutations_from_database.force_change(attr)
       end
 
       # Handles <tt>restore_*!</tt> for +method_missing+.
@@ -257,18 +327,13 @@ module ActiveModel
         end
       end
 
-      # This is necessary because `changed_attributes` might be overridden in
-      # other implementations (e.g. in `ActiveRecord`)
-      alias_method :attributes_changed_by_setter, :changed_attributes # :nodoc:
+      def attributes_changed_by_setter
+        @attributes_changed_by_setter ||= ActiveSupport::HashWithIndifferentAccess.new
+      end
 
       # Force an attribute to have a particular "before" value
       def set_attribute_was(attr, old_value)
         attributes_changed_by_setter[attr] = old_value
       end
-
-      # Remove changes information for the provided attributes.
-      def clear_attribute_changes(attributes) # :doc:
-        attributes_changed_by_setter.except!(*attributes)
-      end
   end
 end
diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 971bdd08b1..275e3f1313 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -322,9 +322,13 @@ module ActiveModel
     #  person.errors.added? :name, :too_long                                # => false
     #  person.errors.added? :name, "is too long"                            # => false
     def added?(attribute, message = :invalid, options = {})
-      message = message.call if message.respond_to?(:call)
-      message = normalize_message(attribute, message, options)
-      self[attribute].include? message
+      if message.is_a? Symbol
+        self.details[attribute].map { |e| e[:error] }.include? message
+      else
+        message = message.call if message.respond_to?(:call)
+        message = normalize_message(attribute, message, options)
+        self[attribute].include? message
+      end
     end
 
     # Returns all the full error messages in an array.
diff --git a/activemodel/lib/active_model/gem_version.rb b/activemodel/lib/active_model/gem_version.rb
index 39269c159c..3c344fe854 100644
--- a/activemodel/lib/active_model/gem_version.rb
+++ b/activemodel/lib/active_model/gem_version.rb
@@ -10,7 +10,7 @@ module ActiveModel
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activemodel/lib/active_model/type.rb b/activemodel/lib/active_model/type.rb
index cb603b3d25..39324999c9 100644
--- a/activemodel/lib/active_model/type.rb
+++ b/activemodel/lib/active_model/type.rb
@@ -1,21 +1,21 @@
 # frozen_string_literal: true
 
-require_relative "type/helpers"
-require_relative "type/value"
-
-require_relative "type/big_integer"
-require_relative "type/binary"
-require_relative "type/boolean"
-require_relative "type/date"
-require_relative "type/date_time"
-require_relative "type/decimal"
-require_relative "type/float"
-require_relative "type/immutable_string"
-require_relative "type/integer"
-require_relative "type/string"
-require_relative "type/time"
-
-require_relative "type/registry"
+require "active_model/type/helpers"
+require "active_model/type/value"
+
+require "active_model/type/big_integer"
+require "active_model/type/binary"
+require "active_model/type/boolean"
+require "active_model/type/date"
+require "active_model/type/date_time"
+require "active_model/type/decimal"
+require "active_model/type/float"
+require "active_model/type/immutable_string"
+require "active_model/type/integer"
+require "active_model/type/string"
+require "active_model/type/time"
+
+require "active_model/type/registry"
 
 module ActiveModel
   module Type
@@ -32,6 +32,10 @@ module ActiveModel
       def lookup(*args, **kwargs) # :nodoc:
         registry.lookup(*args, **kwargs)
       end
+
+      def default_value # :nodoc:
+        @default_value ||= Value.new
+      end
     end
 
     register(:big_integer, Type::BigInteger)
diff --git a/activemodel/lib/active_model/type/big_integer.rb b/activemodel/lib/active_model/type/big_integer.rb
index d080fcc0f2..89e43bcc5f 100644
--- a/activemodel/lib/active_model/type/big_integer.rb
+++ b/activemodel/lib/active_model/type/big_integer.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "integer"
+require "active_model/type/integer"
 
 module ActiveModel
   module Type
diff --git a/activemodel/lib/active_model/type/helpers.rb b/activemodel/lib/active_model/type/helpers.rb
index a4e1427b64..403f0a9e6b 100644
--- a/activemodel/lib/active_model/type/helpers.rb
+++ b/activemodel/lib/active_model/type/helpers.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "helpers/accepts_multiparameter_time"
-require_relative "helpers/numeric"
-require_relative "helpers/mutable"
-require_relative "helpers/time_value"
+require "active_model/type/helpers/accepts_multiparameter_time"
+require "active_model/type/helpers/numeric"
+require "active_model/type/helpers/mutable"
+require "active_model/type/helpers/time_value"
diff --git a/activemodel/lib/active_model/type/string.rb b/activemodel/lib/active_model/type/string.rb
index 6ba2c2a3d2..36f13945b1 100644
--- a/activemodel/lib/active_model/type/string.rb
+++ b/activemodel/lib/active_model/type/string.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "immutable_string"
+require "active_model/type/immutable_string"
 
 module ActiveModel
   module Type
diff --git a/activemodel/lib/active_model/validations/confirmation.rb b/activemodel/lib/active_model/validations/confirmation.rb
index 0abec56b68..1b5d5b09ab 100644
--- a/activemodel/lib/active_model/validations/confirmation.rb
+++ b/activemodel/lib/active_model/validations/confirmation.rb
@@ -9,7 +9,7 @@ module ActiveModel
       end
 
       def validate_each(record, attribute, value)
-        if (confirmed = record.send("#{attribute}_confirmation"))
+        unless (confirmed = record.send("#{attribute}_confirmation")).nil?
           unless confirmation_value_equal?(record, attribute, value, confirmed)
             human_attribute_name = record.class.human_attribute_name(attribute)
             record.errors.add(:"#{attribute}_confirmation", :confirmation, options.except(:case_sensitive).merge!(attribute: human_attribute_name))
diff --git a/activemodel/lib/active_model/validations/exclusion.rb b/activemodel/lib/active_model/validations/exclusion.rb
index a6cbfcc813..3be7ab6ba8 100644
--- a/activemodel/lib/active_model/validations/exclusion.rb
+++ b/activemodel/lib/active_model/validations/exclusion.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "clusivity"
+require "active_model/validations/clusivity"
 
 module ActiveModel
   module Validations
diff --git a/activemodel/lib/active_model/validations/inclusion.rb b/activemodel/lib/active_model/validations/inclusion.rb
index 00e27b528a..3104e7e329 100644
--- a/activemodel/lib/active_model/validations/inclusion.rb
+++ b/activemodel/lib/active_model/validations/inclusion.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "clusivity"
+require "active_model/validations/clusivity"
 
 module ActiveModel
   module Validations
diff --git a/activemodel/lib/active_model/validations/length.rb b/activemodel/lib/active_model/validations/length.rb
index d1a4197286..d6c80b2c5d 100644
--- a/activemodel/lib/active_model/validations/length.rb
+++ b/activemodel/lib/active_model/validations/length.rb
@@ -31,8 +31,8 @@ module ActiveModel
         keys.each do |key|
           value = options[key]
 
-          unless (value.is_a?(Integer) && value >= 0) || value == Float::INFINITY
-            raise ArgumentError, ":#{key} must be a nonnegative Integer or Infinity"
+          unless (value.is_a?(Integer) && value >= 0) || value == Float::INFINITY || value.is_a?(Symbol) || value.is_a?(Proc)
+            raise ArgumentError, ":#{key} must be a nonnegative Integer, Infinity, Symbol, or Proc"
           end
         end
       end
@@ -45,6 +45,12 @@ module ActiveModel
           next unless check_value = options[key]
 
           if !value.nil? || skip_nil_check?(key)
+            case check_value
+            when Proc
+              check_value = check_value.call(record)
+            when Symbol
+              check_value = record.send(check_value)
+            end
             next if value_length.send(validity_check, check_value)
           end
 
diff --git a/activerecord/test/cases/attribute_set_test.rb b/activemodel/test/cases/attribute_set_test.rb
index 8be77ed88f..6e522d6c80 100644
--- a/activerecord/test/cases/attribute_set_test.rb
+++ b/activemodel/test/cases/attribute_set_test.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "active_model/attribute_set"
 
-module ActiveRecord
-  class AttributeSetTest < ActiveRecord::TestCase
+module ActiveModel
+  class AttributeSetTest < ActiveModel::TestCase
     test "building a new set from raw attributes" do
       builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Float.new)
       attributes = builder.build_from_database(foo: "1.1", bar: "2.2")
@@ -162,7 +163,8 @@ module ActiveRecord
     end
 
     test "the primary_key is always initialized" do
-      builder = AttributeSet::Builder.new({ foo: Type::Integer.new }, :foo)
+      defaults = { foo: Attribute.from_user(:foo, nil, nil) }
+      builder = AttributeSet::Builder.new({ foo: Type::Integer.new }, defaults)
       attributes = builder.build_from_database
 
       assert attributes.key?(:foo)
diff --git a/activerecord/test/cases/attribute_test.rb b/activemodel/test/cases/attribute_test.rb
index 1731e7926e..14d86cef97 100644
--- a/activerecord/test/cases/attribute_test.rb
+++ b/activemodel/test/cases/attribute_test.rb
@@ -2,8 +2,8 @@
 
 require "cases/helper"
 
-module ActiveRecord
-  class AttributeTest < ActiveRecord::TestCase
+module ActiveModel
+  class AttributeTest < ActiveModel::TestCase
     setup do
       @type = Minitest::Mock.new
     end
diff --git a/activemodel/test/cases/attributes_dirty_test.rb b/activemodel/test/cases/attributes_dirty_test.rb
new file mode 100644
index 0000000000..83a86371e0
--- /dev/null
+++ b/activemodel/test/cases/attributes_dirty_test.rb
@@ -0,0 +1,205 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+class AttributesDirtyTest < ActiveModel::TestCase
+  class DirtyModel
+    include ActiveModel::Model
+    include ActiveModel::Attributes
+    include ActiveModel::Dirty
+    attribute :name, :string
+    attribute :color, :string
+    attribute :size, :integer
+
+    def save
+      changes_applied
+    end
+
+    def reload
+      clear_changes_information
+    end
+  end
+
+  setup do
+    @model = DirtyModel.new
+  end
+
+  test "setting attribute will result in change" do
+    assert !@model.changed?
+    assert !@model.name_changed?
+    @model.name = "Ringo"
+    assert @model.changed?
+    assert @model.name_changed?
+  end
+
+  test "list of changed attribute keys" do
+    assert_equal [], @model.changed
+    @model.name = "Paul"
+    assert_equal ["name"], @model.changed
+  end
+
+  test "changes to attribute values" do
+    assert !@model.changes["name"]
+    @model.name = "John"
+    assert_equal [nil, "John"], @model.changes["name"]
+  end
+
+  test "checking if an attribute has changed to a particular value" do
+    @model.name = "Ringo"
+    assert @model.name_changed?(from: nil, to: "Ringo")
+    assert_not @model.name_changed?(from: "Pete", to: "Ringo")
+    assert @model.name_changed?(to: "Ringo")
+    assert_not @model.name_changed?(to: "Pete")
+    assert @model.name_changed?(from: nil)
+    assert_not @model.name_changed?(from: "Pete")
+  end
+
+  test "changes accessible through both strings and symbols" do
+    @model.name = "David"
+    assert_not_nil @model.changes[:name]
+    assert_not_nil @model.changes["name"]
+  end
+
+  test "be consistent with symbols arguments after the changes are applied" do
+    @model.name = "David"
+    assert @model.attribute_changed?(:name)
+    @model.save
+    @model.name = "Rafael"
+    assert @model.attribute_changed?(:name)
+  end
+
+  test "attribute mutation" do
+    @model.name = "Yam"
+    @model.save
+    assert !@model.name_changed?
+    @model.name.replace("Hadad")
+    assert @model.name_changed?
+  end
+
+  test "resetting attribute" do
+    @model.name = "Bob"
+    @model.restore_name!
+    assert_nil @model.name
+    assert !@model.name_changed?
+  end
+
+  test "setting color to same value should not result in change being recorded" do
+    @model.color = "red"
+    assert @model.color_changed?
+    @model.save
+    assert !@model.color_changed?
+    assert !@model.changed?
+    @model.color = "red"
+    assert !@model.color_changed?
+    assert !@model.changed?
+  end
+
+  test "saving should reset model's changed status" do
+    @model.name = "Alf"
+    assert @model.changed?
+    @model.save
+    assert !@model.changed?
+    assert !@model.name_changed?
+  end
+
+  test "saving should preserve previous changes" do
+    @model.name = "Jericho Cane"
+    @model.save
+    assert_equal [nil, "Jericho Cane"], @model.previous_changes["name"]
+  end
+
+  test "setting new attributes should not affect previous changes" do
+    @model.name = "Jericho Cane"
+    @model.save
+    @model.name = "DudeFella ManGuy"
+    assert_equal [nil, "Jericho Cane"], @model.name_previous_change
+  end
+
+  test "saving should preserve model's previous changed status" do
+    @model.name = "Jericho Cane"
+    @model.save
+    assert @model.name_previously_changed?
+  end
+
+  test "previous value is preserved when changed after save" do
+    assert_equal({}, @model.changed_attributes)
+    @model.name = "Paul"
+    assert_equal({ "name" => nil }, @model.changed_attributes)
+
+    @model.save
+
+    @model.name = "John"
+    assert_equal({ "name" => "Paul" }, @model.changed_attributes)
+  end
+
+  test "changing the same attribute multiple times retains the correct original value" do
+    @model.name = "Otto"
+    @model.save
+    @model.name = "DudeFella ManGuy"
+    @model.name = "Mr. Manfredgensonton"
+    assert_equal ["Otto", "Mr. Manfredgensonton"], @model.name_change
+    assert_equal @model.name_was, "Otto"
+  end
+
+  test "using attribute_will_change! with a symbol" do
+    @model.size = 1
+    assert @model.size_changed?
+  end
+
+  test "reload should reset all changes" do
+    @model.name = "Dmitry"
+    @model.name_changed?
+    @model.save
+    @model.name = "Bob"
+
+    assert_equal [nil, "Dmitry"], @model.previous_changes["name"]
+    assert_equal "Dmitry", @model.changed_attributes["name"]
+
+    @model.reload
+
+    assert_equal ActiveSupport::HashWithIndifferentAccess.new, @model.previous_changes
+    assert_equal ActiveSupport::HashWithIndifferentAccess.new, @model.changed_attributes
+  end
+
+  test "restore_attributes should restore all previous data" do
+    @model.name = "Dmitry"
+    @model.color = "Red"
+    @model.save
+    @model.name = "Bob"
+    @model.color = "White"
+
+    @model.restore_attributes
+
+    assert_not @model.changed?
+    assert_equal "Dmitry", @model.name
+    assert_equal "Red", @model.color
+  end
+
+  test "restore_attributes can restore only some attributes" do
+    @model.name = "Dmitry"
+    @model.color = "Red"
+    @model.save
+    @model.name = "Bob"
+    @model.color = "White"
+
+    @model.restore_attributes(["name"])
+
+    assert @model.changed?
+    assert_equal "Dmitry", @model.name
+    assert_equal "White", @model.color
+  end
+
+  test "changing the attribute reports a change only when the cast value changes" do
+    @model.size = "2.3"
+    @model.save
+    @model.size = "2.1"
+
+    assert_equal false, @model.changed?
+
+    @model.size = "5.1"
+
+    assert_equal true, @model.changed?
+    assert_equal true, @model.size_changed?
+    assert_equal({ "size" => [2, 5] }, @model.changes)
+  end
+end
diff --git a/activemodel/test/cases/attributes_test.rb b/activemodel/test/cases/attributes_test.rb
new file mode 100644
index 0000000000..914aee1ac0
--- /dev/null
+++ b/activemodel/test/cases/attributes_test.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+module ActiveModel
+  class AttributesTest < ActiveModel::TestCase
+    class ModelForAttributesTest
+      include ActiveModel::Model
+      include ActiveModel::Attributes
+
+      attribute :integer_field, :integer
+      attribute :string_field, :string
+      attribute :decimal_field, :decimal
+      attribute :string_with_default, :string, default: "default string"
+      attribute :date_field, :date, default: -> { Date.new(2016, 1, 1) }
+      attribute :boolean_field, :boolean
+    end
+
+    class ChildModelForAttributesTest < ModelForAttributesTest
+    end
+
+    class GrandchildModelForAttributesTest < ChildModelForAttributesTest
+      attribute :integer_field, :string
+    end
+
+    test "properties assignment" do
+      data = ModelForAttributesTest.new(
+        integer_field: "2.3",
+        string_field: "Rails FTW",
+        decimal_field: "12.3",
+        boolean_field: "0"
+      )
+
+      assert_equal 2, data.integer_field
+      assert_equal "Rails FTW", data.string_field
+      assert_equal BigDecimal.new("12.3"), data.decimal_field
+      assert_equal "default string", data.string_with_default
+      assert_equal Date.new(2016, 1, 1), data.date_field
+      assert_equal false, data.boolean_field
+
+      data.integer_field = 10
+      data.string_with_default = nil
+      data.boolean_field = "1"
+
+      assert_equal 10, data.integer_field
+      assert_nil data.string_with_default
+      assert_equal true, data.boolean_field
+    end
+
+    test "nonexistent attribute" do
+      assert_raise ActiveModel::UnknownAttributeError do
+        ModelForAttributesTest.new(nonexistent: "nonexistent")
+      end
+    end
+
+    test "children inherit attributes" do
+      data = ChildModelForAttributesTest.new(integer_field: "4.4")
+
+      assert_equal 4, data.integer_field
+    end
+
+    test "children can override parents" do
+      data = GrandchildModelForAttributesTest.new(integer_field: "4.4")
+
+      assert_equal "4.4", data.integer_field
+    end
+  end
+end
diff --git a/activemodel/test/cases/dirty_test.rb b/activemodel/test/cases/dirty_test.rb
index 2cd9e185e6..dfe041ff50 100644
--- a/activemodel/test/cases/dirty_test.rb
+++ b/activemodel/test/cases/dirty_test.rb
@@ -219,4 +219,8 @@ class DirtyTest < ActiveModel::TestCase
     assert_equal "Dmitry", @model.name
     assert_equal "White", @model.color
   end
+
+  test "model can be dup-ed without Attributes" do
+    assert @model.dup
+  end
 end
diff --git a/activemodel/test/cases/errors_test.rb b/activemodel/test/cases/errors_test.rb
index ab18af0de1..d5c282b620 100644
--- a/activemodel/test/cases/errors_test.rb
+++ b/activemodel/test/cases/errors_test.rb
@@ -223,6 +223,13 @@ class ErrorsTest < ActiveModel::TestCase
     assert !person.errors.added?(:name)
   end
 
+  test "added? returns false when checking for an error by symbol and a different error with same message is present" do
+    I18n.backend.store_translations("en", errors: { attributes: { name: { wrong: "is wrong", used: "is wrong" } } })
+    person = Person.new
+    person.errors.add(:name, :wrong)
+    assert !person.errors.added?(:name, :used)
+  end
+
   test "size calculates the number of error messages" do
     person = Person.new
     person.errors.add(:name, "cannot be blank")
diff --git a/activemodel/test/cases/type/big_integer_test.rb b/activemodel/test/cases/type/big_integer_test.rb
index 3d29235d52..0fa0200df4 100644
--- a/activemodel/test/cases/type/big_integer_test.rb
+++ b/activemodel/test/cases/type/big_integer_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/binary_test.rb b/activemodel/test/cases/type/binary_test.rb
index ef4f125a3b..3221a73e49 100644
--- a/activemodel/test/cases/type/binary_test.rb
+++ b/activemodel/test/cases/type/binary_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/boolean_test.rb b/activemodel/test/cases/type/boolean_test.rb
index 97b165ab48..2d33579595 100644
--- a/activemodel/test/cases/type/boolean_test.rb
+++ b/activemodel/test/cases/type/boolean_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/date_test.rb b/activemodel/test/cases/type/date_test.rb
index 15c40a37b7..e8cf178612 100644
--- a/activemodel/test/cases/type/date_test.rb
+++ b/activemodel/test/cases/type/date_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/date_time_test.rb b/activemodel/test/cases/type/date_time_test.rb
index 598ccf485e..60f62becc2 100644
--- a/activemodel/test/cases/type/date_time_test.rb
+++ b/activemodel/test/cases/type/date_time_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/decimal_test.rb b/activemodel/test/cases/type/decimal_test.rb
index a0acdc2736..b91d67f95f 100644
--- a/activemodel/test/cases/type/decimal_test.rb
+++ b/activemodel/test/cases/type/decimal_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/float_test.rb b/activemodel/test/cases/type/float_test.rb
index 46e8b34dfe..28318e06f8 100644
--- a/activemodel/test/cases/type/float_test.rb
+++ b/activemodel/test/cases/type/float_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/immutable_string_test.rb b/activemodel/test/cases/type/immutable_string_test.rb
index 72f5779dfb..751f753ddb 100644
--- a/activemodel/test/cases/type/immutable_string_test.rb
+++ b/activemodel/test/cases/type/immutable_string_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/integer_test.rb b/activemodel/test/cases/type/integer_test.rb
index d2e635b447..8c5d18c9b3 100644
--- a/activemodel/test/cases/type/integer_test.rb
+++ b/activemodel/test/cases/type/integer_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 require "active_support/core_ext/numeric/time"
 
 module ActiveModel
diff --git a/activemodel/test/cases/type/registry_test.rb b/activemodel/test/cases/type/registry_test.rb
index f34104286c..0633ea2538 100644
--- a/activemodel/test/cases/type/registry_test.rb
+++ b/activemodel/test/cases/type/registry_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/string_test.rb b/activemodel/test/cases/type/string_test.rb
index d39389718b..825c8bb246 100644
--- a/activemodel/test/cases/type/string_test.rb
+++ b/activemodel/test/cases/type/string_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/time_test.rb b/activemodel/test/cases/type/time_test.rb
index 0bea95768d..f7102d1e97 100644
--- a/activemodel/test/cases/type/time_test.rb
+++ b/activemodel/test/cases/type/time_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/value_test.rb b/activemodel/test/cases/type/value_test.rb
index 671343b0c8..55b5d9d584 100644
--- a/activemodel/test/cases/type/value_test.rb
+++ b/activemodel/test/cases/type/value_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/validations/conditional_validation_test.rb b/activemodel/test/cases/validations/conditional_validation_test.rb
index 68dade556c..caea8b65ef 100644
--- a/activemodel/test/cases/validations/conditional_validation_test.rb
+++ b/activemodel/test/cases/validations/conditional_validation_test.rb
@@ -18,6 +18,22 @@ class ConditionalValidationTest < ActiveModel::TestCase
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
+  def test_if_validation_using_array_of_true_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: [:condition_is_true, :condition_is_true])
+    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
+    assert t.invalid?
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
+  end
+
+  def test_unless_validation_using_array_of_false_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: [:condition_is_false, :condition_is_false])
+    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
+    assert t.invalid?
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
+  end
+
   def test_unless_validation_using_method_true
     # When the method returns true
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_true)
@@ -26,59 +42,31 @@ class ConditionalValidationTest < ActiveModel::TestCase
     assert_empty t.errors[:title]
   end
 
-  def test_if_validation_using_method_false
-    # When the method returns false
-    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true_but_its_not)
+  def test_if_validation_using_array_of_true_and_false_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: [:condition_is_true, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
     assert_empty t.errors[:title]
   end
 
-  def test_unless_validation_using_method_false
-    # When the method returns false
-    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_true_but_its_not)
-    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
-    assert_equal ["hoo 5"], t.errors["title"]
-  end
-
-  def test_if_validation_using_string_true
-    # When the evaluated string returns true
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: "a = 1; a == 1")
-    end
-    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
-    assert_equal ["hoo 5"], t.errors["title"]
-  end
-
-  def test_unless_validation_using_string_true
-    # When the evaluated string returns true
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: "a = 1; a == 1")
-    end
+  def test_unless_validation_using_array_of_true_and_felse_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: [:condition_is_true, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
     assert_empty t.errors[:title]
   end
 
-  def test_if_validation_using_string_false
-    # When the evaluated string returns false
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: "false")
-    end
+  def test_if_validation_using_method_false
+    # When the method returns false
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
     assert_empty t.errors[:title]
   end
 
-  def test_unless_validation_using_string_false
-    # When the evaluated string returns false
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: "false")
-    end
+  def test_unless_validation_using_method_false
+    # When the method returns false
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
     assert t.invalid?
     assert t.errors[:title].any?
@@ -123,27 +111,18 @@ class ConditionalValidationTest < ActiveModel::TestCase
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
-  # previous implementation of validates_presence_of eval'd the
-  # string with the wrong binding, this regression test is to
-  # ensure that it works correctly
-  def test_validation_with_if_as_string
-    Topic.validates_presence_of(:title)
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_presence_of(:author_name, if: "title.to_s.match('important')")
-    end
-
-    t = Topic.new
-    assert t.invalid?, "A topic without a title should not be valid"
-    assert_empty t.errors[:author_name], "A topic without an 'important' title should not require an author"
-
-    t.title = "Just a title"
-    assert t.valid?, "A topic with a basic title should be valid"
-
-    t.title = "A very important title"
-    assert t.invalid?, "A topic with an important title, but without an author, should not be valid"
-    assert t.errors[:author_name].any?, "A topic with an 'important' title should require an author"
+  def test_validation_using_conbining_if_true_and_unless_true_conditions
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true, unless: :condition_is_true)
+    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
+    assert t.valid?
+    assert_empty t.errors[:title]
+  end
 
-    t.author_name = "Hubert J. Farnsworth"
-    assert t.valid?, "A topic with an important title and author should be valid"
+  def test_validation_using_conbining_if_true_and_unless_false_conditions
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true, unless: :condition_is_false)
+    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
+    assert t.invalid?
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 end
diff --git a/activemodel/test/cases/validations/confirmation_validation_test.rb b/activemodel/test/cases/validations/confirmation_validation_test.rb
index e84415a868..8b2c65289b 100644
--- a/activemodel/test/cases/validations/confirmation_validation_test.rb
+++ b/activemodel/test/cases/validations/confirmation_validation_test.rb
@@ -37,6 +37,19 @@ class ConfirmationValidationTest < ActiveModel::TestCase
     assert t.valid?
   end
 
+  def test_validates_confirmation_of_with_boolean_attribute
+    Topic.validates_confirmation_of(:approved)
+
+    t = Topic.new(approved: true, approved_confirmation: nil)
+    assert t.valid?
+
+    t.approved_confirmation = false
+    assert t.invalid?
+
+    t.approved_confirmation = true
+    assert t.valid?
+  end
+
   def test_validates_confirmation_of_for_ruby_class
     Person.validates_confirmation_of :karma
 
diff --git a/activemodel/test/cases/validations/length_validation_test.rb b/activemodel/test/cases/validations/length_validation_test.rb
index a0d8e058f5..42f76f3e3c 100644
--- a/activemodel/test/cases/validations/length_validation_test.rb
+++ b/activemodel/test/cases/validations/length_validation_test.rb
@@ -410,4 +410,35 @@ class LengthValidationTest < ActiveModel::TestCase
     assert Topic.new("title" => "david").valid?
     assert Topic.new("title" => "david2").invalid?
   end
+
+  def test_validates_length_of_using_proc_as_maximum
+    Topic.validates_length_of :title, maximum: ->(model) { 5 }
+
+    t = Topic.new("title" => "valid", "content" => "whatever")
+    assert t.valid?
+
+    t.title = "notvalid"
+    assert t.invalid?
+    assert t.errors[:title].any?
+    assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
+
+    t.title = ""
+    assert t.valid?
+  end
+
+  def test_validates_length_of_using_proc_as_maximum_with_model_method
+    Topic.send(:define_method, :max_title_length, lambda { 5 })
+    Topic.validates_length_of :title, maximum: Proc.new(&:max_title_length)
+
+    t = Topic.new("title" => "valid", "content" => "whatever")
+    assert t.valid?
+
+    t.title = "notvalid"
+    assert t.invalid?
+    assert t.errors[:title].any?
+    assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
+
+    t.title = ""
+    assert t.valid?
+  end
 end
diff --git a/activemodel/test/cases/validations/numericality_validation_test.rb b/activemodel/test/cases/validations/numericality_validation_test.rb
index 001815e28f..fbbaf8a30c 100644
--- a/activemodel/test/cases/validations/numericality_validation_test.rb
+++ b/activemodel/test/cases/validations/numericality_validation_test.rb
@@ -59,7 +59,7 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_of_with_integer_only_and_symbol_as_value
-    Topic.validates_numericality_of :approved, only_integer: :condition_is_true_but_its_not
+    Topic.validates_numericality_of :approved, only_integer: :condition_is_false
 
     invalid!(NIL + BLANK + JUNK)
     valid!(FLOATS + INTEGERS + BIGDECIMAL + INFINITY)
diff --git a/activemodel/test/cases/validations/validates_test.rb b/activemodel/test/cases/validations/validates_test.rb
index 77cb8ebdc1..7f32f5dc74 100644
--- a/activemodel/test/cases/validations/validates_test.rb
+++ b/activemodel/test/cases/validations/validates_test.rb
@@ -62,17 +62,23 @@ class ValidatesTest < ActiveModel::TestCase
   end
 
   def test_validates_with_if_as_local_conditions
-    Person.validates :karma, presence: true, email: { unless: :condition_is_true }
+    Person.validates :karma, presence: true, email: { if: :condition_is_false }
     person = Person.new
     person.valid?
     assert_equal ["can't be blank"], person.errors[:karma]
   end
 
   def test_validates_with_if_as_shared_conditions
-    Person.validates :karma, presence: true, email: true, if: :condition_is_true
+    Person.validates :karma, presence: true, email: true, if: :condition_is_false
+    person = Person.new
+    assert person.valid?
+  end
+
+  def test_validates_with_unless_as_local_conditions
+    Person.validates :karma, presence: true, email: { unless: :condition_is_true }
     person = Person.new
     person.valid?
-    assert_equal ["can't be blank", "is not an email"], person.errors[:karma].sort
+    assert_equal ["can't be blank"], person.errors[:karma]
   end
 
   def test_validates_with_unless_shared_conditions
diff --git a/activemodel/test/cases/validations/with_validation_test.rb b/activemodel/test/cases/validations/with_validation_test.rb
index fbe20dc000..13ef5e6a31 100644
--- a/activemodel/test/cases/validations/with_validation_test.rb
+++ b/activemodel/test/cases/validations/with_validation_test.rb
@@ -70,51 +70,15 @@ class ValidatesWithTest < ActiveModel::TestCase
     assert_includes topic.errors[:base], OTHER_ERROR_MESSAGE
   end
 
-  test "with if statements that return false" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, if: "1 == 2")
-    end
-    topic = Topic.new
-    assert topic.valid?
-  end
-
-  test "with if statements that return true" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, if: "1 == 1")
-    end
-    topic = Topic.new
-    assert topic.invalid?
-    assert_includes topic.errors[:base], ERROR_MESSAGE
-  end
-
-  test "with unless statements that return true" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, unless: "1 == 1")
-    end
-    topic = Topic.new
-    assert topic.valid?
-  end
-
-  test "with unless statements that returns false" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, unless: "1 == 2")
-    end
-    topic = Topic.new
-    assert topic.invalid?
-    assert_includes topic.errors[:base], ERROR_MESSAGE
-  end
-
   test "passes all configuration options to the validator class" do
     topic = Topic.new
     validator = Minitest::Mock.new
-    validator.expect(:new, validator, [{ foo: :bar, if: "1 == 1", class: Topic }])
+    validator.expect(:new, validator, [{ foo: :bar, if: :condition_is_true, class: Topic }])
     validator.expect(:validate, nil, [topic])
     validator.expect(:is_a?, false, [Symbol])
     validator.expect(:is_a?, false, [String])
 
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(validator, if: "1 == 1", foo: :bar)
-    end
+    Topic.validates_with(validator, if: :condition_is_true, foo: :bar)
     assert topic.valid?
     validator.verify
   end
diff --git a/activemodel/test/models/person.rb b/activemodel/test/models/person.rb
index b61fdf76b1..8dd8ceadad 100644
--- a/activemodel/test/models/person.rb
+++ b/activemodel/test/models/person.rb
@@ -9,6 +9,10 @@ class Person
   def condition_is_true
     true
   end
+
+  def condition_is_false
+    false
+  end
 end
 
 class Person::Gender
diff --git a/activemodel/test/models/topic.rb b/activemodel/test/models/topic.rb
index 2f4e92c3b2..b0af00ee45 100644
--- a/activemodel/test/models/topic.rb
+++ b/activemodel/test/models/topic.rb
@@ -23,7 +23,7 @@ class Topic
     true
   end
 
-  def condition_is_true_but_its_not
+  def condition_is_false
     false
   end
 
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index b421fedc96..89a12d4223 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,224 @@
-*   Add new error class `TransactionTimeout` for MySQL adapter which will be raised
-    when lock wait time expires.
+*   Add support for PostgreSQL operator classes to `add_index`.
+
+    Example:
+
+        add_index :users, :name, using: :gist, opclass: { name: :gist_trgm_ops }
+
+    *Greg Navis*
+
+*   Don't allow scopes to be defined which conflict with instance methods on `Relation`.
+
+    Fixes #31120.
+
+    *kinnrot*
+
+
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Add new error class `QueryCanceled` which will be raised
+    when canceling statement due to user request.
+
+    *Ryuta Kamizono*
+
+*   Add `#up_only` to database migrations for code that is only relevant when
+    migrating up, e.g. populating a new column.
+
+    *Rich Daley*
+
+*   Require raw SQL fragments to be explicitly marked when used in
+    relation query methods.
+
+    Before:
+    ```
+    Article.order("LENGTH(title)")
+    ```
+
+    After:
+    ```
+    Article.order(Arel.sql("LENGTH(title)"))
+    ```
+
+    This prevents SQL injection if applications use the [strongly
+    discouraged] form `Article.order(params[:my_order])`, under the
+    mistaken belief that only column names will be accepted.
+
+    Raw SQL strings will now cause a deprecation warning, which will
+    become an UnknownAttributeReference error in Rails 6.0. Applications
+    can opt in to the future behavior by setting `allow_unsafe_raw_sql`
+    to `:disabled`.
+
+    Common and judged-safe string values (such as simple column
+    references) are unaffected:
+    ```
+    Article.order("title DESC")
+    ```
+
+    *Ben Toews*
+
+*   `update_all` will now pass its values to `Type#cast` before passing them to
+    `Type#serialize`. This means that `update_all(foo: 'true')` will properly
+    persist a boolean.
+
+    *Sean Griffin*
+
+*   Add new error class `StatementTimeout` which will be raised
+    when statement timeout exceeded.
+
+    *Ryuta Kamizono*
+
+*   Fix `bin/rails db:migrate` with specified `VERSION`.
+    `bin/rails db:migrate` with empty VERSION behaves as without `VERSION`.
+    Check a format of `VERSION`: Allow a migration version number
+    or name of a migration file. Raise error if format of `VERSION` is invalid.
+    Raise error if target migration doesn't exist.
+
+    *bogdanvlviv*
+
+*   Fixed a bug where column orders for an index weren't written to
+    `db/schema.rb` when using the sqlite adapter.
+
+    Fixes #30902.
+
+    *Paul Kuruvilla*
+
+*   Remove deprecated method `#sanitize_conditions`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated method `#scope_chain`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated configuration `.error_on_ignored_order_or_limit`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated arguments from `#verify!`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated argument `name` from `#indexes`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated method `ActiveRecord::Migrator.schema_migrations_table_name`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated method `supports_primary_key?`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated method `supports_migrations?`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated methods `initialize_schema_migrations_table` and `initialize_internal_metadata_table`.
+
+    *Rafael Mendonça França*
+
+*   Raises when calling `lock!` in a dirty record.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated support to passing a class to `:class_name` on associations.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated argument `default` from `index_name_exists?`.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated support to `quoted_id` when typecasting an Active Record object.
+
+    *Rafael Mendonça França*
+
+*   Fix `bin/rails db:setup` and `bin/rails db:test:prepare` create  wrong
+    ar_internal_metadata's data for a test database.
+
+    Before:
+    ```
+    $ RAILS_ENV=test rails dbconsole
+    > SELECT * FROM ar_internal_metadata;
+    key|value|created_at|updated_at
+    environment|development|2017-09-11 23:14:10.815679|2017-09-11 23:14:10.815679
+    ```
+
+    After:
+    ```
+    $ RAILS_ENV=test rails dbconsole
+    > SELECT * FROM ar_internal_metadata;
+    key|value|created_at|updated_at
+    environment|test|2017-09-11 23:14:10.815679|2017-09-11 23:14:10.815679
+    ```
+
+    Fixes #26731.
+
+    *bogdanvlviv*
+
+*   Fix longer sequence name detection for serial columns.
+
+    Fixes #28332.
+
+    *Ryuta Kamizono*
+
+*   MySQL: Don't lose `auto_increment: true` in the `db/schema.rb`.
+
+    Fixes #30894.
+
+    *Ryuta Kamizono*
+
+*   Fix `COUNT(DISTINCT ...)` for `GROUP BY` with `ORDER BY` and `LIMIT`.
+
+    Fixes #30886.
+
+    *Ryuta Kamizono*
+
+*   PostgreSQL `tsrange` now preserves subsecond precision.
+
+    PostgreSQL 9.1+ introduced range types, and Rails added support for using
+    this datatype in Active Record. However, the serialization of
+    `PostgreSQL::OID::Range` was incomplete, because it did not properly
+    cast the bounds that make up the range. This led to subseconds being
+    dropped in SQL commands:
+
+    Before:
+
+        connection.type_cast(tsrange.serialize(range_value))
+        # => "[2010-01-01 13:30:00 UTC,2011-02-02 19:30:00 UTC)"
+
+    Now:
+
+        connection.type_cast(tsrange.serialize(range_value))
+        # => "[2010-01-01 13:30:00.670277,2011-02-02 19:30:00.745125)"
+
+    *Thomas Cannon*
+
+*   Passing a `Set` to `Relation#where` now behaves the same as passing an
+    array.
+
+    *Sean Griffin*
+
+*   Use given algorithm while removing index from database.
+
+    Fixes #24190.
+
+    *Mehmet Emin İNAÇ*
+
+*   Update payload names for `sql.active_record` instrumentation to be
+    more descriptive.
+
+    Fixes #30586.
+
+    *Jeremy Green*
+
+*   Add new error class `LockWaitTimeout` which will be raised
+    when lock wait timeout exceeded.
 
     *Gabriel Courtemanche*
 
@@ -209,10 +428,6 @@
 
     *Ryuta Kamizono*
 
-*   Quote database name in `db:create` grant statement (when database user does not have access to create the database).
-
-    *Rune Philosof*
-
 *   Raise error `UnknownMigrationVersionError` on the movement of migrations
     when the current migration does not exist.
 
diff --git a/activerecord/README.rdoc b/activerecord/README.rdoc
index ae53ecd177..19650b82ae 100644
--- a/activerecord/README.rdoc
+++ b/activerecord/README.rdoc
@@ -26,7 +26,7 @@ The Product class is automatically mapped to the table named "products",
 which might look like this:
 
    CREATE TABLE products (
-     id int NOT NULL auto_increment,
+     id bigint NOT NULL auto_increment,
      name varchar(255),
      PRIMARY KEY  (id)
    );
@@ -208,7 +208,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activerecord/activerecord.gemspec b/activerecord/activerecord.gemspec
index 7ad06fe840..8e42a11df4 100644
--- a/activerecord/activerecord.gemspec
+++ b/activerecord/activerecord.gemspec
@@ -31,5 +31,5 @@ Gem::Specification.new do |s|
   s.add_dependency "activesupport", version
   s.add_dependency "activemodel",   version
 
-  s.add_dependency "arel", "9.0.0.alpha"
+  s.add_dependency "arel", ">= 9.0"
 end
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 0c19fed9e1..5de6503144 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -27,14 +27,14 @@ require "active_support"
 require "active_support/rails"
 require "active_model"
 require "arel"
+require "yaml"
 
-require_relative "active_record/version"
-require_relative "active_record/attribute_set"
+require "active_record/version"
+require "active_model/attribute_set"
 
 module ActiveRecord
   extend ActiveSupport::Autoload
 
-  autoload :Attribute
   autoload :Base
   autoload :Callbacks
   autoload :Core
@@ -104,6 +104,7 @@ module ActiveRecord
 
     autoload :Result
     autoload :TableMetadata
+    autoload :Type
   end
 
   module Coders
@@ -181,3 +182,7 @@ end
 ActiveSupport.on_load(:i18n) do
   I18n.load_path << File.expand_path("active_record/locale/en.yml", __dir__)
 end
+
+YAML.load_tags["!ruby/object:ActiveRecord::AttributeSet"] = "ActiveModel::AttributeSet"
+YAML.load_tags["!ruby/object:ActiveRecord::Attribute::FromDatabase"] = "ActiveModel::Attribute::FromDatabase"
+YAML.load_tags["!ruby/object:ActiveRecord::LazyAttributeHash"] = "ActiveModel::LazyAttributeHash"
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index a61c0336db..661605d3e5 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -3,7 +3,7 @@
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/string/conversions"
 require "active_support/core_ext/module/remove_method"
-require_relative "errors"
+require "active_record/errors"
 
 module ActiveRecord
   class AssociationNotFoundError < ConfigurationError #:nodoc:
@@ -140,26 +140,6 @@ module ActiveRecord
   class HasOneThroughCantAssociateThroughHasOneOrManyReflection < ThroughCantAssociateThroughHasOneOrManyReflection #:nodoc:
   end
 
-  class HasManyThroughCantAssociateNewRecords < ActiveRecordError #:nodoc:
-    def initialize(owner = nil, reflection = nil)
-      if owner && reflection
-        super("Cannot associate new records through '#{owner.class.name}##{reflection.name}' on '#{reflection.source_reflection.class_name rescue nil}##{reflection.source_reflection.name rescue nil}'. Both records must have an id in order to create the has_many :through record associating them.")
-      else
-        super("Cannot associate new records.")
-      end
-    end
-  end
-
-  class HasManyThroughCantDissociateNewRecords < ActiveRecordError #:nodoc:
-    def initialize(owner = nil, reflection = nil)
-      if owner && reflection
-        super("Cannot dissociate new records through '#{owner.class.name}##{reflection.name}' on '#{reflection.source_reflection.class_name rescue nil}##{reflection.source_reflection.name rescue nil}'. Both records must have an id in order to delete the has_many :through record associating them.")
-      else
-        super("Cannot dissociate new records.")
-      end
-    end
-  end
-
   class ThroughNestedAssociationsAreReadonly < ActiveRecordError #:nodoc:
     def initialize(owner = nil, reflection = nil)
       if owner && reflection
@@ -189,16 +169,6 @@ module ActiveRecord
     end
   end
 
-  class ReadOnlyAssociation < ActiveRecordError #:nodoc:
-    def initialize(reflection = nil)
-      if reflection
-        super("Cannot add to a has_many :through association. Try adding to #{reflection.through_reflection.name.inspect}.")
-      else
-        super("Read-only reflection error.")
-      end
-    end
-  end
-
   # This error is raised when trying to destroy a parent instance in N:1 or 1:1 associations
   # (has_many, has_one) when there is at least 1 child associated instance.
   # ex: if @project.tasks.size > 0, DeleteRestrictionError will be raised when trying to destroy @project
@@ -483,14 +453,14 @@ module ActiveRecord
       # The tables for these classes could look something like:
       #
       #   CREATE TABLE users (
-      #     id int NOT NULL auto_increment,
-      #     account_id int default NULL,
+      #     id bigint NOT NULL auto_increment,
+      #     account_id bigint default NULL,
       #     name varchar default NULL,
       #     PRIMARY KEY  (id)
       #   )
       #
       #   CREATE TABLE accounts (
-      #     id int NOT NULL auto_increment,
+      #     id bigint NOT NULL auto_increment,
       #     name varchar default NULL,
       #     PRIMARY KEY  (id)
       #   )
@@ -557,9 +527,8 @@ module ActiveRecord
       #     has_many :birthday_events, ->(user) { where(starts_on: user.birthday) }, class_name: 'Event'
       #   end
       #
-      # Note: Joining, eager loading and preloading of these associations is not fully possible.
+      # Note: Joining, eager loading and preloading of these associations is not possible.
       # These operations happen before instance creation and the scope will be called with a +nil+ argument.
-      # This can lead to unexpected behavior and is deprecated.
       #
       # == Association callbacks
       #
@@ -850,7 +819,7 @@ module ActiveRecord
       #   project.milestones             # fetches milestones from the database
       #   project.milestones.size        # uses the milestone cache
       #   project.milestones.empty?      # uses the milestone cache
-      #   project.milestones(true).size  # fetches milestones from the database
+      #   project.milestones.reload.size # fetches milestones from the database
       #   project.milestones             # uses the milestone cache
       #
       # == Eager loading of associations
@@ -1400,7 +1369,7 @@ module ActiveRecord
         #   has_many :tags, as: :taggable
         #   has_many :reports, -> { readonly }
         #   has_many :subscribers, through: :subscriptions, source: :user
-        def has_many(name, scope = nil, options = {}, &extension)
+        def has_many(name, scope = nil, **options, &extension)
           reflection = Builder::HasMany.build(self, name, scope, options, &extension)
           Reflection.add_reflection self, name, reflection
         end
@@ -1534,7 +1503,7 @@ module ActiveRecord
         #   has_one :club, through: :membership
         #   has_one :primary_address, -> { where(primary: true) }, through: :addressables, source: :addressable
         #   has_one :credit_card, required: true
-        def has_one(name, scope = nil, options = {})
+        def has_one(name, scope = nil, **options)
           reflection = Builder::HasOne.build(self, name, scope, options)
           Reflection.add_reflection self, name, reflection
         end
@@ -1678,7 +1647,7 @@ module ActiveRecord
         #   belongs_to :company, touch: :employees_last_updated_at
         #   belongs_to :user, optional: true
         #   belongs_to :account, default: -> { company.account }
-        def belongs_to(name, scope = nil, options = {})
+        def belongs_to(name, scope = nil, **options)
           reflection = Builder::BelongsTo.build(self, name, scope, options)
           Reflection.add_reflection self, name, reflection
         end
@@ -1848,7 +1817,7 @@ module ActiveRecord
 
           builder = Builder::HasAndBelongsToMany.new name, self, options
 
-          join_model = ActiveSupport::Deprecation.silence { builder.through_model }
+          join_model = builder.through_model
 
           const_set join_model.name, join_model
           private_constant join_model.name
@@ -1877,7 +1846,7 @@ module ActiveRecord
             hm_options[k] = options[k] if options.key? k
           end
 
-          ActiveSupport::Deprecation.silence { has_many name, scope, hm_options, &extension }
+          has_many name, scope, hm_options, &extension
           _reflections[name.to_s].parent_reflection = habtm_reflection
         end
       end
diff --git a/activerecord/lib/active_record/associations/alias_tracker.rb b/activerecord/lib/active_record/associations/alias_tracker.rb
index 096f016976..14881cfe17 100644
--- a/activerecord/lib/active_record/associations/alias_tracker.rb
+++ b/activerecord/lib/active_record/associations/alias_tracker.rb
@@ -6,36 +6,34 @@ module ActiveRecord
   module Associations
     # Keeps track of table aliases for ActiveRecord::Associations::JoinDependency
     class AliasTracker # :nodoc:
-      def self.create(connection, initial_table)
-        aliases = Hash.new(0)
-        aliases[initial_table] = 1
-        new(connection, aliases)
-      end
-
-      def self.create_with_joins(connection, initial_table, joins)
+      def self.create(connection, initial_table, joins)
         if joins.empty?
-          create(connection, initial_table)
+          aliases = Hash.new(0)
         else
           aliases = Hash.new { |h, k|
             h[k] = initial_count_for(connection, k, joins)
           }
-          aliases[initial_table] = 1
-          new(connection, aliases)
         end
+        aliases[initial_table] = 1
+        new(connection, aliases)
       end
 
       def self.initial_count_for(connection, name, table_joins)
-        # quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
-        quoted_name = connection.quote_table_name(name).downcase
+        quoted_name = nil
 
         counts = table_joins.map do |join|
           if join.is_a?(Arel::Nodes::StringJoin)
+            # quoted_name should be case ignored as some database adapters (Oracle) return quoted name in uppercase
+            quoted_name ||= connection.quote_table_name(name)
+
             # Table names + table aliases
-            join.left.downcase.scan(
-              /join(?:\s+\w+)?\s+(\S+\s+)?#{quoted_name}\son/
+            join.left.scan(
+              /JOIN(?:\s+\w+)?\s+(?:\S+\s+)?(?:#{quoted_name}|#{name})\sON/i
             ).size
           elsif join.respond_to? :left
-            join.left.table_name == name ? 1 : 0
+            join.left.name == name ? 1 : 0
+          elsif join.is_a?(Hash)
+            join.fetch(name, 0)
           else
             # this branch is reached by two tests:
             #
@@ -79,10 +77,7 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :aliases
+      attr_reader :aliases
 
       private
 
diff --git a/activerecord/lib/active_record/associations/association_scope.rb b/activerecord/lib/active_record/associations/association_scope.rb
index b2dc044312..11967e0571 100644
--- a/activerecord/lib/active_record/associations/association_scope.rb
+++ b/activerecord/lib/active_record/associations/association_scope.rb
@@ -23,8 +23,7 @@ module ActiveRecord
         reflection = association.reflection
         scope = klass.unscoped
         owner = association.owner
-        alias_tracker = AliasTracker.create(klass.connection, klass.table_name)
-        chain = get_chain(reflection, association, alias_tracker)
+        chain = get_chain(reflection, association, scope.alias_tracker)
 
         scope.extending! reflection.extensions
         add_constraints(scope, owner, chain)
diff --git a/activerecord/lib/active_record/associations/builder/association.rb b/activerecord/lib/active_record/associations/builder/association.rb
index 496b16b58f..ca3032d967 100644
--- a/activerecord/lib/active_record/associations/builder/association.rb
+++ b/activerecord/lib/active_record/associations/builder/association.rb
@@ -38,11 +38,6 @@ module ActiveRecord::Associations::Builder # :nodoc:
     def self.create_reflection(model, name, scope, options, extension = nil)
       raise ArgumentError, "association names must be a Symbol" unless name.kind_of?(Symbol)
 
-      if scope.is_a?(Hash)
-        options = scope
-        scope   = nil
-      end
-
       validate_options(options)
 
       scope = build_scope(scope, extension)
diff --git a/activerecord/lib/active_record/associations/builder/collection_association.rb b/activerecord/lib/active_record/associations/builder/collection_association.rb
index 753fde5146..35a72c3850 100644
--- a/activerecord/lib/active_record/associations/builder/collection_association.rb
+++ b/activerecord/lib/active_record/associations/builder/collection_association.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../associations"
+require "active_record/associations"
 
 module ActiveRecord::Associations::Builder # :nodoc:
   class CollectionAssociation < Association #:nodoc:
diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index 12fcfbcd45..1981da11a2 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -47,7 +47,7 @@ module ActiveRecord::Associations::Builder # :nodoc:
       habtm = JoinTableResolver.build lhs_model, association_name, options
 
       join_model = Class.new(ActiveRecord::Base) {
-        class << self;
+        class << self
           attr_accessor :left_model
           attr_accessor :name
           attr_accessor :table_name_resolver
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index ceedf150e3..921237a735 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -79,7 +79,13 @@ module ActiveRecord
       def find(*args)
         if options[:inverse_of] && loaded?
           args_flatten = args.flatten
-          raise RecordNotFound, "Couldn't find #{scope.klass.name} without an ID" if args_flatten.blank?
+          model = scope.klass
+
+          if args_flatten.blank?
+            error_message = "Couldn't find #{model.name} without an ID"
+            raise RecordNotFound.new(error_message, model.name, model.primary_key, args)
+          end
+
           result = find_by_scan(*args)
 
           result_size = Array(result).size
@@ -181,8 +187,6 @@ module ActiveRecord
       # are actually removed from the database, that depends precisely on
       # +delete_records+. They are in any case removed from the collection.
       def delete(*records)
-        return if records.empty?
-        records = find(records) if records.any? { |record| record.kind_of?(Integer) || record.kind_of?(String) }
         delete_or_destroy(records, options[:dependent])
       end
 
@@ -192,8 +196,6 @@ module ActiveRecord
       # Note that this method removes records from the database ignoring the
       # +:dependent+ option.
       def destroy(*records)
-        return if records.empty?
-        records = find(records) if records.any? { |record| record.kind_of?(Integer) || record.kind_of?(String) }
         delete_or_destroy(records, :destroy)
       end
 
@@ -376,6 +378,8 @@ module ActiveRecord
         end
 
         def delete_or_destroy(records, method)
+          return if records.empty?
+          records = find(records) if records.any? { |record| record.kind_of?(Integer) || record.kind_of?(String) }
           records = records.flatten
           records.each { |record| raise_on_type_mismatch!(record) }
           existing_records = records.reject(&:new_record?)
diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 412e89255d..8b4a48a38c 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -988,6 +988,12 @@ module ActiveRecord
         load_target == other
       end
 
+      ##
+      # :method: to_ary
+      #
+      # :call-seq:
+      #   to_ary()
+      #
       # Returns a new array of objects from the collection. If the collection
       # hasn't been loaded, it fetches the records from the database.
       #
@@ -1021,10 +1027,6 @@ module ActiveRecord
       #   #       #<Pet id: 5, name: "Brain", person_id: 1>,
       #   #       #<Pet id: 6, name: "Boss",  person_id: 1>
       #   #    ]
-      def to_ary
-        load_target.dup
-      end
-      alias_method :to_a, :to_ary
 
       def records # :nodoc:
         load_target
@@ -1072,7 +1074,6 @@ module ActiveRecord
       end
 
       # Reloads the collection from the database. Returns +self+.
-      # Equivalent to <tt>collection(true)</tt>.
       #
       #   class Person < ActiveRecord::Base
       #     has_many :pets
@@ -1086,9 +1087,6 @@ module ActiveRecord
       #
       #   person.pets.reload # fetches pets from the database
       #   # => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]
-      #
-      #   person.pets(true)  # fetches pets from the database
-      #   # => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]
       def reload
         proxy_association.reload
         reset_scope
diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index 77b3d11b47..df4bf07999 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -43,8 +43,6 @@ module ActiveRecord
         Column = Struct.new(:name, :alias)
       end
 
-      attr_reader :alias_tracker, :base_klass, :join_root
-
       def self.make_tree(associations)
         hash = {}
         walk_tree associations, hash
@@ -90,8 +88,8 @@ module ActiveRecord
       #    associations # => [:appointments]
       #    joins # =>  []
       #
-      def initialize(base, table, associations, joins, eager_loading: true)
-        @alias_tracker = AliasTracker.create_with_joins(base.connection, base.table_name, joins)
+      def initialize(base, table, associations, alias_tracker, eager_loading: true)
+        @alias_tracker = alias_tracker
         @eager_loading = eager_loading
         tree = self.class.make_tree associations
         @join_root = JoinBase.new(base, table, build(tree, base))
@@ -158,6 +156,9 @@ module ActiveRecord
         parents.values
       end
 
+      protected
+        attr_reader :alias_tracker, :base_klass, :join_root
+
       private
 
         def make_constraints(parent, child, tables, join_type)
@@ -224,7 +225,7 @@ module ActiveRecord
               raise EagerLoadPolymorphicError.new(reflection)
             end
 
-            JoinAssociation.new reflection, build(right, reflection.klass)
+            JoinAssociation.new(reflection, build(right, reflection.klass), alias_tracker)
           end.compact
         end
 
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index a526468bf6..221c791bf8 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "join_part"
+require "active_record/associations/join_dependency/join_part"
 
 module ActiveRecord
   module Associations
@@ -11,11 +11,12 @@ module ActiveRecord
 
         attr_accessor :tables
 
-        def initialize(reflection, children)
+        def initialize(reflection, children, alias_tracker)
           super(reflection.klass, children)
 
-          @reflection      = reflection
-          @tables          = nil
+          @alias_tracker = alias_tracker
+          @reflection    = reflection
+          @tables        = nil
         end
 
         def match?(other)
@@ -38,11 +39,12 @@ module ActiveRecord
             joins << table.create_join(table, table.create_on(constraint), join_type)
 
             join_scope = reflection.join_scope(table, foreign_klass)
+            arel = join_scope.arel(alias_tracker.aliases)
 
-            if join_scope.arel.constraints.any?
-              joins.concat join_scope.arel.join_sources
+            if arel.constraints.any?
+              joins.concat arel.join_sources
               right = joins.last.right
-              right.expr = right.expr.and(join_scope.arel.constraints)
+              right.expr = right.expr.and(arel.constraints)
             end
 
             # The current table in this iteration becomes the foreign table in the next
@@ -55,6 +57,9 @@ module ActiveRecord
         def table
           tables.first
         end
+
+        protected
+          attr_reader :alias_tracker
       end
     end
   end
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_base.rb b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
index 8a8fa8993b..988b4e8fa2 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_base.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "join_part"
+require "active_record/associations/join_dependency/join_part"
 
 module ActiveRecord
   module Associations
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index 62caf02a2c..e1087be9b3 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -44,16 +44,8 @@ module ActiveRecord
       extend ActiveSupport::Autoload
 
       eager_autoload do
-        autoload :Association,           "active_record/associations/preloader/association"
-        autoload :SingularAssociation,   "active_record/associations/preloader/singular_association"
-        autoload :CollectionAssociation, "active_record/associations/preloader/collection_association"
-        autoload :ThroughAssociation,    "active_record/associations/preloader/through_association"
-
-        autoload :HasMany,             "active_record/associations/preloader/has_many"
-        autoload :HasManyThrough,      "active_record/associations/preloader/has_many_through"
-        autoload :HasOne,              "active_record/associations/preloader/has_one"
-        autoload :HasOneThrough,       "active_record/associations/preloader/has_one_through"
-        autoload :BelongsTo,           "active_record/associations/preloader/belongs_to"
+        autoload :Association,        "active_record/associations/preloader/association"
+        autoload :ThroughAssociation, "active_record/associations/preloader/through_association"
       end
 
       # Eager loads the named associations for the given Active Record record(s).
@@ -91,13 +83,13 @@ module ActiveRecord
       #   { author: :avatar }
       #   [ :books, { author: :avatar } ]
       def preload(records, associations, preload_scope = nil)
-        records       = Array.wrap(records).compact.uniq
-        associations  = Array.wrap(associations)
+        records = records.compact
 
         if records.empty?
           []
         else
-          associations.flat_map { |association|
+          records.uniq!
+          Array.wrap(associations).flat_map { |association|
             preloaders_on association, records, preload_scope
           }
         end
@@ -166,8 +158,6 @@ module ActiveRecord
         end
 
         class AlreadyLoaded # :nodoc:
-          attr_reader :owners, :reflection
-
           def initialize(klass, owners, reflection, preload_scope)
             @owners = owners
             @reflection = reflection
@@ -178,11 +168,13 @@ module ActiveRecord
           def preloaded_records
             owners.flat_map { |owner| owner.association(reflection.name).target }
           end
+
+          protected
+            attr_reader :owners, :reflection
         end
 
         # Returns a class containing the logic needed to load preload the data
-        # and attach it to a relation. For example +Preloader::Association+ or
-        # +Preloader::HasManyThrough+. The class returned implements a `run` method
+        # and attach it to a relation. The class returned implements a `run` method
         # that accepts a preloader.
         def preloader_for(reflection, owners)
           if owners.first.association(reflection.name).loaded?
@@ -190,13 +182,10 @@ module ActiveRecord
           end
           reflection.check_preloadable!
 
-          case reflection.macro
-          when :has_many
-            reflection.options[:through] ? HasManyThrough : HasMany
-          when :has_one
-            reflection.options[:through] ? HasOneThrough : HasOne
-          when :belongs_to
-            BelongsTo
+          if reflection.options[:through]
+            ThroughAssociation
+          else
+            Association
           end
         end
     end
diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index 9bb6a613e1..735da152b7 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -4,7 +4,6 @@ module ActiveRecord
   module Associations
     class Preloader
       class Association #:nodoc:
-        attr_reader :owners, :reflection, :preload_scope, :model, :klass
         attr_reader :preloaded_records
 
         def initialize(klass, owners, reflection, preload_scope)
@@ -17,55 +16,50 @@ module ActiveRecord
         end
 
         def run(preloader)
-          preload(preloader)
-        end
-
-        def preload(preloader)
-          raise NotImplementedError
-        end
+          records = load_records do |record|
+            owner = owners_by_key[convert_key(record[association_key_name])]
+            association = owner.association(reflection.name)
+            association.set_inverse_instance(record)
+          end
 
-        # The name of the key on the associated records
-        def association_key_name
-          raise NotImplementedError
+          owners.each do |owner|
+            associate_records_to_owner(owner, records[convert_key(owner[owner_key_name])] || [])
+          end
         end
 
-        # The name of the key on the model which declares the association
-        def owner_key_name
-          raise NotImplementedError
-        end
+        protected
+          attr_reader :owners, :reflection, :preload_scope, :model, :klass
 
         private
-          def options
-            reflection.options
+          # The name of the key on the associated records
+          def association_key_name
+            reflection.join_primary_key(klass)
           end
 
-          def associated_records_by_owner(preloader)
-            records = load_records do |record|
-              owner = owners_by_key[convert_key(record[association_key_name])]
-              association = owner.association(reflection.name)
-              association.set_inverse_instance(record)
-            end
+          # The name of the key on the model which declares the association
+          def owner_key_name
+            reflection.join_foreign_key
+          end
 
-            owners.each_with_object({}) do |owner, result|
-              result[owner] = records[convert_key(owner[owner_key_name])] || []
+          def associate_records_to_owner(owner, records)
+            association = owner.association(reflection.name)
+            if reflection.collection?
+              association.loaded!
+              association.target.concat(records)
+            else
+              association.target = records.first
             end
           end
 
           def owner_keys
-            unless defined?(@owner_keys)
-              @owner_keys = owners.map do |owner|
-                owner[owner_key_name]
-              end
-              @owner_keys.uniq!
-              @owner_keys.compact!
-            end
-            @owner_keys
+            @owner_keys ||= owners_by_key.keys
           end
 
           def owners_by_key
             unless defined?(@owners_by_key)
               @owners_by_key = owners.each_with_object({}) do |owner, h|
-                h[convert_key(owner[owner_key_name])] = owner
+                key = convert_key(owner[owner_key_name])
+                h[key] = owner if key
               end
             end
             @owners_by_key
diff --git a/activerecord/lib/active_record/associations/preloader/belongs_to.rb b/activerecord/lib/active_record/associations/preloader/belongs_to.rb
deleted file mode 100644
index ae9695f26a..0000000000
--- a/activerecord/lib/active_record/associations/preloader/belongs_to.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class BelongsTo < SingularAssociation #:nodoc:
-        def association_key_name
-          options[:primary_key] || klass && klass.primary_key
-        end
-
-        def owner_key_name
-          reflection.foreign_key
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/collection_association.rb b/activerecord/lib/active_record/associations/preloader/collection_association.rb
deleted file mode 100644
index fb920a642c..0000000000
--- a/activerecord/lib/active_record/associations/preloader/collection_association.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class CollectionAssociation < Association #:nodoc:
-        private
-
-          def preload(preloader)
-            associated_records_by_owner(preloader).each do |owner, records|
-              association = owner.association(reflection.name)
-              association.loaded!
-              association.target.concat(records)
-            end
-          end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_many.rb b/activerecord/lib/active_record/associations/preloader/has_many.rb
deleted file mode 100644
index 29a1ce099d..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_many.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasMany < CollectionAssociation #:nodoc:
-        def association_key_name
-          reflection.foreign_key
-        end
-
-        def owner_key_name
-          reflection.active_record_primary_key
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_many_through.rb b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
deleted file mode 100644
index 0639fdca44..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_many_through.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasManyThrough < CollectionAssociation #:nodoc:
-        include ThroughAssociation
-
-        def associated_records_by_owner(preloader)
-          records_by_owner = super
-
-          if reflection_scope.distinct_value
-            records_by_owner.each_value(&:uniq!)
-          end
-
-          records_by_owner
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_one.rb b/activerecord/lib/active_record/associations/preloader/has_one.rb
deleted file mode 100644
index d87abf630f..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_one.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasOne < SingularAssociation #:nodoc:
-        def association_key_name
-          reflection.foreign_key
-        end
-
-        def owner_key_name
-          reflection.active_record_primary_key
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_one_through.rb b/activerecord/lib/active_record/associations/preloader/has_one_through.rb
deleted file mode 100644
index 17734d0257..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_one_through.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasOneThrough < SingularAssociation #:nodoc:
-        include ThroughAssociation
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/singular_association.rb b/activerecord/lib/active_record/associations/preloader/singular_association.rb
deleted file mode 100644
index 266b5f6b1c..0000000000
--- a/activerecord/lib/active_record/associations/preloader/singular_association.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class SingularAssociation < Association #:nodoc:
-        private
-
-          def preload(preloader)
-            associated_records_by_owner(preloader).each do |owner, associated_records|
-              record = associated_records.first
-
-              association = owner.association(reflection.name)
-              association.target = record
-            end
-          end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb
index 8aac00d910..a6b7ab80a2 100644
--- a/activerecord/lib/active_record/associations/preloader/through_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/through_association.rb
@@ -3,84 +3,60 @@
 module ActiveRecord
   module Associations
     class Preloader
-      module ThroughAssociation #:nodoc:
-        def through_reflection
-          reflection.through_reflection
-        end
-
-        def source_reflection
-          reflection.source_reflection
-        end
-
-        def associated_records_by_owner(preloader)
-          through_scope = through_scope()
-
-          preloader.preload(owners,
-                            through_reflection.name,
-                            through_scope)
-
-          through_records = owners.map do |owner|
-            center = owner.association(through_reflection.name).target
-            [owner, Array(center)]
-          end
-
-          reset_association(owners, through_reflection.name, through_scope)
-
-          middle_records = through_records.flat_map(&:last)
-
-          preloaders = preloader.preload(middle_records,
-                                         source_reflection.name,
-                                         reflection_scope)
-
+      class ThroughAssociation < Association # :nodoc:
+        def run(preloader)
+          already_loaded     = owners.first.association(through_reflection.name).loaded?
+          through_scope      = through_scope()
+          reflection_scope   = target_reflection_scope
+          through_preloaders = preloader.preload(owners, through_reflection.name, through_scope)
+          middle_records     = through_preloaders.flat_map(&:preloaded_records)
+          preloaders         = preloader.preload(middle_records, source_reflection.name, reflection_scope)
           @preloaded_records = preloaders.flat_map(&:preloaded_records)
 
-          middle_to_pl = preloaders.each_with_object({}) do |pl, h|
-            pl.owners.each { |middle|
-              h[middle] = pl
-            }
-          end
-
-          through_records.each_with_object({}) do |(lhs, center), records_by_owner|
-            pl_to_middle = center.group_by { |record| middle_to_pl[record] }
-
-            records_by_owner[lhs] = pl_to_middle.flat_map do |pl, middles|
-              rhs_records = middles.flat_map { |r|
-                r.association(source_reflection.name).target
-              }.compact
-
-              # Respect the order on `reflection_scope` if it exists, else use the natural order.
-              if reflection_scope.values[:order].present?
-                @id_map ||= id_to_index_map @preloaded_records
-                rhs_records.sort_by { |rhs| @id_map[rhs] }
-              else
-                rhs_records
+          owners.each do |owner|
+            through_records = Array(owner.association(through_reflection.name).target)
+            if already_loaded
+              if source_type = reflection.options[:source_type]
+                through_records = through_records.select do |record|
+                  record[reflection.foreign_type] == source_type
+                end
               end
+            else
+              owner.association(through_reflection.name).reset if through_scope
+            end
+            result = through_records.flat_map do |record|
+              association = record.association(source_reflection.name)
+              target = association.target
+              association.reset if preload_scope
+              target
+            end
+            result.compact!
+            if reflection_scope
+              result.sort_by! { |rhs| preload_index[rhs] } if reflection_scope.order_values.any?
+              result.uniq! if reflection_scope.distinct_value
             end
+            associate_records_to_owner(owner, result)
           end
         end
 
         private
-
-          def id_to_index_map(ids)
-            id_map = {}
-            ids.each_with_index { |id, index| id_map[id] = index }
-            id_map
+          def through_reflection
+            reflection.through_reflection
           end
 
-          def reset_association(owners, association_name, through_scope)
-            should_reset = (through_scope != through_reflection.klass.unscoped) ||
-               (options[:source_type] && through_reflection.collection?)
+          def source_reflection
+            reflection.source_reflection
+          end
 
-            # Don't cache the association - we would only be caching a subset
-            if should_reset
-              owners.each { |owner|
-                owner.association(association_name).reset
-              }
+          def preload_index
+            @preload_index ||= @preloaded_records.each_with_object({}).with_index do |(id, result), index|
+              result[id] = index
             end
           end
 
           def through_scope
             scope = through_reflection.klass.unscoped
+            options = reflection.options
 
             if options[:source_type]
               scope.where! reflection.foreign_type => options[:source_type]
@@ -113,7 +89,17 @@ module ActiveRecord
               end
             end
 
-            scope
+            scope unless scope.empty_scope?
+          end
+
+          def target_reflection_scope
+            if preload_scope
+              reflection_scope.merge(preload_scope)
+            elsif reflection.scope
+              reflection_scope
+            else
+              nil
+            end
           end
       end
     end
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index e4ca6c8408..64f81ca582 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -33,7 +33,9 @@ module ActiveRecord
 
     BLACKLISTED_CLASS_METHODS = %w(private public protected allocate new name parent superclass)
 
-    class GeneratedAttributeMethods < Module; end # :nodoc:
+    class GeneratedAttributeMethods < Module #:nodoc:
+      include Mutex_m
+    end
 
     module ClassMethods
       def inherited(child_class) #:nodoc:
@@ -42,7 +44,7 @@ module ActiveRecord
       end
 
       def initialize_generated_modules # :nodoc:
-        @generated_attribute_methods = GeneratedAttributeMethods.new { extend Mutex_m }
+        @generated_attribute_methods = GeneratedAttributeMethods.new
         @attribute_methods_generated = false
         include @generated_attribute_methods
 
@@ -165,6 +167,46 @@ module ActiveRecord
         end
       end
 
+      # Regexp whitelist. Matches the following:
+      #   "#{table_name}.#{column_name}"
+      #   "#{column_name}"
+      COLUMN_NAME_WHITELIST = /\A(?:\w+\.)?\w+\z/i
+
+      # Regexp whitelist. Matches the following:
+      #   "#{table_name}.#{column_name}"
+      #   "#{table_name}.#{column_name} #{direction}"
+      #   "#{column_name}"
+      #   "#{column_name} #{direction}"
+      COLUMN_NAME_ORDER_WHITELIST = /\A(?:\w+\.)?\w+(?:\s+asc|\s+desc)?\z/i
+
+      def enforce_raw_sql_whitelist(args, whitelist: COLUMN_NAME_WHITELIST) # :nodoc:
+        unexpected = args.reject do |arg|
+          arg.kind_of?(Arel::Node) ||
+            arg.is_a?(Arel::Nodes::SqlLiteral) ||
+            arg.is_a?(Arel::Attributes::Attribute) ||
+            arg.to_s.split(/\s*,\s*/).all? { |part| whitelist.match?(part) }
+        end
+
+        return if unexpected.none?
+
+        if allow_unsafe_raw_sql == :deprecated
+          ActiveSupport::Deprecation.warn(
+            "Dangerous query method (method whose arguments are used as raw " \
+            "SQL) called with non-attribute argument(s): " \
+            "#{unexpected.map(&:inspect).join(", ")}. Non-attribute " \
+            "arguments will be disallowed in Rails 6.0. This method should " \
+            "not be called with user-provided values, such as request " \
+            "parameters or model attributes. Known-safe values can be passed " \
+            "by wrapping them in Arel.sql()."
+          )
+        else
+          raise(ActiveRecord::UnknownAttributeReference,
+            "Query method called with non-attribute argument(s): " +
+            unexpected.map(&:inspect).join(", ")
+          )
+        end
+      end
+
       # Returns true if the given attribute exists, otherwise false.
       #
       #   class Person < ActiveRecord::Base
@@ -234,7 +276,7 @@ module ActiveRecord
         return has_attribute?(name)
       end
 
-      return true
+      true
     end
 
     # Returns +true+ if the given attribute is in the attributes hash, otherwise +false+.
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index 4f957ac3ca..3de6fe566d 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "../attribute_mutation_tracker"
 
 module ActiveRecord
   module AttributeMethods
@@ -33,66 +32,13 @@ module ActiveRecord
       # <tt>reload</tt> the record and clears changed attributes.
       def reload(*)
         super.tap do
+          @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
           @mutations_before_last_save = nil
-          clear_mutation_trackers
-          @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-        end
-      end
-
-      def initialize_dup(other) # :nodoc:
-        super
-        @attributes = self.class._default_attributes.map do |attr|
-          attr.with_value_from_user(@attributes.fetch_value(attr.name))
-        end
-        clear_mutation_trackers
-      end
-
-      def changes_applied # :nodoc:
-        @mutations_before_last_save = mutation_tracker
-        @mutations_from_database = AttributeMutationTracker.new(@attributes)
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-        forget_attribute_assignments
-        clear_mutation_trackers
-      end
-
-      def clear_changes_information # :nodoc:
-        @mutations_before_last_save = nil
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-        forget_attribute_assignments
-        clear_mutation_trackers
-      end
-
-      def clear_attribute_changes(attr_names) # :nodoc:
-        super
-        attr_names.each do |attr_name|
-          clear_attribute_change(attr_name)
-        end
-      end
-
-      def changed_attributes # :nodoc:
-        # This should only be set by methods which will call changed_attributes
-        # multiple times when it is known that the computed value cannot change.
-        if defined?(@cached_changed_attributes)
-          @cached_changed_attributes
-        else
-          super.reverse_merge(mutation_tracker.changed_values).freeze
-        end
-      end
-
-      def changes # :nodoc:
-        cache_changed_attributes do
-          super
+          @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
+          @mutations_from_database = nil
         end
       end
 
-      def previous_changes # :nodoc:
-        mutations_before_last_save.changes
-      end
-
-      def attribute_changed_in_place?(attr_name) # :nodoc:
-        mutation_tracker.changed_in_place?(attr_name)
-      end
-
       # Did this attribute change when we last saved? This method can be invoked
       # as +saved_change_to_name?+ instead of <tt>saved_change_to_attribute?("name")</tt>.
       # Behaves similarly to +attribute_changed?+. This method is useful in
@@ -183,34 +129,6 @@ module ActiveRecord
           result
         end
 
-        def mutation_tracker
-          unless defined?(@mutation_tracker)
-            @mutation_tracker = nil
-          end
-          @mutation_tracker ||= AttributeMutationTracker.new(@attributes)
-        end
-
-        def mutations_from_database
-          unless defined?(@mutations_from_database)
-            @mutations_from_database = nil
-          end
-          @mutations_from_database ||= mutation_tracker
-        end
-
-        def changes_include?(attr_name)
-          super || mutation_tracker.changed?(attr_name)
-        end
-
-        def clear_attribute_change(attr_name)
-          mutation_tracker.forget_change(attr_name)
-          mutations_from_database.forget_change(attr_name)
-        end
-
-        def attribute_will_change!(attr_name)
-          super
-          mutations_from_database.force_change(attr_name)
-        end
-
         def _update_record(*)
           partial_writes? ? super(keys_for_partial_write) : super
         end
@@ -222,30 +140,6 @@ module ActiveRecord
         def keys_for_partial_write
           changed_attribute_names_to_save & self.class.column_names
         end
-
-        def forget_attribute_assignments
-          @attributes = @attributes.map(&:forgetting_assignment)
-        end
-
-        def clear_mutation_trackers
-          @mutation_tracker = nil
-          @mutations_from_database = nil
-        end
-
-        def mutations_before_last_save
-          @mutations_before_last_save ||= NullMutationTracker.instance
-        end
-
-        def cache_changed_attributes
-          @cached_changed_attributes = changed_attributes
-          yield
-        ensure
-          clear_changed_attributes_cache
-        end
-
-        def clear_changed_attributes_cache
-          remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
-        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index 63c059e291..d8fc046e10 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -17,13 +17,15 @@ module ActiveRecord
       # Returns the primary key value.
       def id
         sync_with_transaction_state
-        _read_attribute(self.class.primary_key) if self.class.primary_key
+        primary_key = self.class.primary_key
+        _read_attribute(primary_key) if primary_key
       end
 
       # Sets the primary key value.
       def id=(value)
         sync_with_transaction_state
-        _write_attribute(self.class.primary_key, value) if self.class.primary_key
+        primary_key = self.class.primary_key
+        _write_attribute(primary_key, value) if primary_key
       end
 
       # Queries the primary key value.
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index b070235684..4077250583 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -58,8 +58,9 @@ module ActiveRecord
           attr_name.to_s
         end
 
-        name = self.class.primary_key if name == "id".freeze && self.class.primary_key
-        sync_with_transaction_state if name == self.class.primary_key
+        primary_key = self.class.primary_key
+        name = primary_key if name == "id".freeze && primary_key
+        sync_with_transaction_state if name == primary_key
         _read_attribute(name, &block)
       end
 
diff --git a/activerecord/lib/active_record/attribute_methods/write.rb b/activerecord/lib/active_record/attribute_methods/write.rb
index 37891ce2ef..bb0ec6a8c3 100644
--- a/activerecord/lib/active_record/attribute_methods/write.rb
+++ b/activerecord/lib/active_record/attribute_methods/write.rb
@@ -39,8 +39,9 @@ module ActiveRecord
           attr_name.to_s
         end
 
-        name = self.class.primary_key if name == "id".freeze && self.class.primary_key
-        sync_with_transaction_state if name == self.class.primary_key
+        primary_key = self.class.primary_key
+        name = primary_key if name == "id".freeze && primary_key
+        sync_with_transaction_state if name == primary_key
         _write_attribute(name, value)
       end
 
diff --git a/activerecord/lib/active_record/attributes.rb b/activerecord/lib/active_record/attributes.rb
index afb559db71..0b7c9398a8 100644
--- a/activerecord/lib/active_record/attributes.rb
+++ b/activerecord/lib/active_record/attributes.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "attribute/user_provided_default"
+require "active_model/attribute/user_provided_default"
 
 module ActiveRecord
   # See ActiveRecord::Attributes::ClassMethods for documentation
@@ -250,14 +250,14 @@ module ActiveRecord
           if value == NO_DEFAULT_PROVIDED
             default_attribute = _default_attributes[name].with_type(type)
           elsif from_user
-            default_attribute = Attribute::UserProvidedDefault.new(
+            default_attribute = ActiveModel::Attribute::UserProvidedDefault.new(
               name,
               value,
               type,
               _default_attributes.fetch(name.to_s) { nil },
             )
           else
-            default_attribute = Attribute.from_database(name, value, type)
+            default_attribute = ActiveModel::Attribute.from_database(name, value, type)
           end
           _default_attributes[name] = default_attribute
         end
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 6974cf74f6..a1250c3835 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -436,6 +436,9 @@ module ActiveRecord
             if (autosave && record.changed_for_autosave?) || new_record? || record_changed?(reflection, record, key)
               unless reflection.through_reflection
                 record[reflection.foreign_key] = key
+                if inverse_reflection = reflection.inverse_of
+                  record.association(inverse_reflection.name).loaded!
+                end
               end
 
               saved = record.save(validate: !autosave)
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 541ff51fbe..b7ad944cec 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -15,14 +15,14 @@ require "active_support/core_ext/kernel/singleton_class"
 require "active_support/core_ext/module/introspection"
 require "active_support/core_ext/object/duplicable"
 require "active_support/core_ext/class/subclasses"
-require_relative "attribute_decorators"
-require_relative "define_callbacks"
-require_relative "errors"
-require_relative "log_subscriber"
-require_relative "explain_subscriber"
-require_relative "relation/delegation"
-require_relative "attributes"
-require_relative "type_caster"
+require "active_record/attribute_decorators"
+require "active_record/define_callbacks"
+require "active_record/errors"
+require "active_record/log_subscriber"
+require "active_record/explain_subscriber"
+require "active_record/relation/delegation"
+require "active_record/attributes"
+require "active_record/type_caster"
 
 module ActiveRecord #:nodoc:
   # = Active Record
diff --git a/activerecord/lib/active_record/callbacks.rb b/activerecord/lib/active_record/callbacks.rb
index a2439e6ec7..9ab2780760 100644
--- a/activerecord/lib/active_record/callbacks.rb
+++ b/activerecord/lib/active_record/callbacks.rb
@@ -98,9 +98,9 @@ module ActiveRecord
   # == Types of callbacks
   #
   # There are four types of callbacks accepted by the callback macros: Method references (symbol), callback objects,
-  # inline methods (using a proc), and inline eval methods (using a string). Method references and callback objects
+  # inline methods (using a proc). Method references and callback objects
   # are the recommended approaches, inline methods using a proc are sometimes appropriate (such as for
-  # creating mix-ins), and inline eval methods are deprecated.
+  # creating mix-ins).
   #
   # The method reference callbacks work by specifying a protected or private method available in the object, like this:
   #
@@ -240,7 +240,7 @@ module ActiveRecord
   #
   #     private
   #
-  #     def log_chidren
+  #     def log_children
   #       # Child processing
   #     end
   #
@@ -265,7 +265,7 @@ module ActiveRecord
   #
   #     private
   #
-  #     def log_chidren
+  #     def log_children
   #       # Child processing
   #     end
   #
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index f3e6516414..88b398ad45 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -12,6 +12,9 @@ module ActiveRecord
           timestamp = collection.max_by(&timestamp_column)._read_attribute(timestamp_column)
         end
       else
+        if collection.eager_loading?
+          collection = collection.send(:apply_join_dependency)
+        end
         column_type = type_for_attribute(timestamp_column.to_s)
         column = connection.column_name_from_arel_node(collection.arel_attribute(timestamp_column))
         select_values = "COUNT(*) AS #{connection.quote_column_name("size")}, MAX(%s) AS timestamp"
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 0759f4d2b3..9849f9d5d7 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -63,15 +63,13 @@ module ActiveRecord
     # There are several connection-pooling-related options that you can add to
     # your database connection configuration:
     #
-    # * +pool+: number indicating size of connection pool (default 5)
-    # * +checkout_timeout+: number of seconds to block and wait for a connection
-    #   before giving up and raising a timeout error (default 5 seconds).
-    # * +reaping_frequency+: frequency in seconds to periodically run the
-    #   Reaper, which attempts to find and recover connections from dead
-    #   threads, which can occur if a programmer forgets to close a
-    #   connection at the end of a thread or a thread dies unexpectedly.
-    #   Regardless of this setting, the Reaper will be invoked before every
-    #   blocking wait. (Default +nil+, which means don't schedule the Reaper).
+    # * +pool+: maximum number of connections the pool may manage (default 5).
+    # * +idle_timeout+: number of seconds that a connection will be kept
+    #   unused in the pool before it is automatically disconnected (default
+    #   300 seconds). Set this to zero to keep connections forever.
+    # * +checkout_timeout+: number of seconds to wait for a connection to
+    #   become available before giving up and raising a timeout error (default
+    #   5 seconds).
     #
     #--
     # Synchronization policy:
@@ -82,11 +80,8 @@ module ActiveRecord
     # * private methods that require being called in a +synchronize+ blocks
     #   are now explicitly documented
     class ConnectionPool
-      # Threadsafe, fair, FIFO queue.  Meant to be used by ConnectionPool
-      # with which it shares a Monitor.  But could be a generic Queue.
-      #
-      # The Queue in stdlib's 'thread' could replace this class except
-      # stdlib's doesn't support waiting with a timeout.
+      # Threadsafe, fair, LIFO queue.  Meant to be used by ConnectionPool
+      # with which it shares a Monitor.
       class Queue
         def initialize(lock = Monitor.new)
           @lock = lock
@@ -175,7 +170,7 @@ module ActiveRecord
 
           # Removes and returns the head of the queue if possible, or +nil+.
           def remove
-            @queue.shift
+            @queue.pop
           end
 
           # Remove and return the head the queue if the number of
@@ -283,12 +278,12 @@ module ActiveRecord
           end
       end
 
-      # Every +frequency+ seconds, the reaper will call +reap+ on +pool+.
-      # A reaper instantiated with a +nil+ frequency will never reap the
-      # connection pool.
+      # Every +frequency+ seconds, the reaper will call +reap+ and +flush+ on
+      # +pool+. A reaper instantiated with a zero frequency will never reap
+      # the connection pool.
       #
-      # Configure the frequency by setting "reaping_frequency" in your
-      # database yaml file.
+      # Configure the frequency by setting +reaping_frequency+ in your database
+      # yaml file (default 60 seconds).
       class Reaper
         attr_reader :pool, :frequency
 
@@ -298,11 +293,12 @@ module ActiveRecord
         end
 
         def run
-          return unless frequency
+          return unless frequency && frequency > 0
           Thread.new(frequency, pool) { |t, p|
             loop do
               sleep t
               p.reap
+              p.flush
             end
           }
         end
@@ -326,6 +322,10 @@ module ActiveRecord
         @spec = spec
 
         @checkout_timeout = (spec.config[:checkout_timeout] && spec.config[:checkout_timeout].to_f) || 5
+        if @idle_timeout = spec.config.fetch(:idle_timeout, 300)
+          @idle_timeout = @idle_timeout.to_f
+          @idle_timeout = nil if @idle_timeout <= 0
+        end
 
         # default max pool size to 5
         @size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
@@ -356,7 +356,10 @@ module ActiveRecord
 
         @lock_thread = false
 
-        @reaper = Reaper.new(self, spec.config[:reaping_frequency] && spec.config[:reaping_frequency].to_f)
+        # +reaping_frequency+ is configurable mostly for historical reasons, but it could
+        # also be useful if someone wants a very low +idle_timeout+.
+        reaping_frequency = spec.config.fetch(:reaping_frequency, 60)
+        @reaper = Reaper.new(self, reaping_frequency && reaping_frequency.to_f)
         @reaper.run
       end
 
@@ -450,6 +453,21 @@ module ActiveRecord
         disconnect(false)
       end
 
+      # Discards all connections in the pool (even if they're currently
+      # leased!), along with the pool itself. Any further interaction with the
+      # pool (except #spec and #schema_cache) is undefined.
+      #
+      # See AbstractAdapter#discard!
+      def discard! # :nodoc:
+        synchronize do
+          return if @connections.nil? # already discarded
+          @connections.each do |conn|
+            conn.discard!
+          end
+          @connections = @available = @thread_cached_conns = nil
+        end
+      end
+
       # Clears the cache which maps classes and re-connects connections that
       # require reloading.
       #
@@ -575,6 +593,35 @@ module ActiveRecord
         end
       end
 
+      # Disconnect all connections that have been idle for at least
+      # +minimum_idle+ seconds. Connections currently checked out, or that were
+      # checked in less than +minimum_idle+ seconds ago, are unaffected.
+      def flush(minimum_idle = @idle_timeout)
+        return if minimum_idle.nil?
+
+        idle_connections = synchronize do
+          @connections.select do |conn|
+            !conn.in_use? && conn.seconds_idle >= minimum_idle
+          end.each do |conn|
+            conn.lease
+
+            @available.delete conn
+            @connections.delete conn
+          end
+        end
+
+        idle_connections.each do |conn|
+          conn.disconnect!
+        end
+      end
+
+      # Disconnect all currently idle connections. Connections currently checked
+      # out are unaffected.
+      def flush!
+        reap
+        flush(-1)
+      end
+
       def num_waiting_in_queue # :nodoc:
         @available.num_waiting
       end
@@ -866,11 +913,31 @@ module ActiveRecord
     # about the model. The model needs to pass a specification name to the handler,
     # in order to look up the correct connection pool.
     class ConnectionHandler
+      def self.unowned_pool_finalizer(pid_map) # :nodoc:
+        lambda do |_|
+          discard_unowned_pools(pid_map)
+        end
+      end
+
+      def self.discard_unowned_pools(pid_map) # :nodoc:
+        pid_map.each do |pid, pools|
+          pools.values.compact.each(&:discard!) unless pid == Process.pid
+        end
+      end
+
       def initialize
         # These caches are keyed by spec.name (ConnectionSpecification#name).
         @owner_to_pool = Concurrent::Map.new(initial_capacity: 2) do |h, k|
+          # Discard the parent's connection pools immediately; we have no need
+          # of them
+          ConnectionHandler.discard_unowned_pools(h)
+
           h[k] = Concurrent::Map.new(initial_capacity: 2)
         end
+
+        # Backup finalizer: if the forked child never needed a pool, the above
+        # early discard has not occurred
+        ObjectSpace.define_finalizer self, ConnectionHandler.unowned_pool_finalizer(@owner_to_pool)
       end
 
       def connection_pool_list
@@ -924,6 +991,13 @@ module ActiveRecord
         connection_pool_list.each(&:disconnect!)
       end
 
+      # Disconnects all currently idle connections.
+      #
+      # See ConnectionPool#flush! for details.
+      def flush_idle_connections!
+        connection_pool_list.each(&:flush!)
+      end
+
       # Locate the connection of the nearest super class. This can be an
       # active or defined connection: if it is the latter, it will be
       # opened and set as the active connection for the class it was defined
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index 9ad04c3216..92e46ccf9f 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -11,19 +11,6 @@ module ActiveRecord
       def quote(value)
         value = id_value_for_database(value) if value.is_a?(Base)
 
-        if value.respond_to?(:quoted_id)
-          at = value.method(:quoted_id).source_location
-          at &&= " at %s:%d" % at
-
-          owner = value.method(:quoted_id).owner.to_s
-          klass = value.class.to_s
-          klass += "(#{owner})" unless owner == klass
-
-          ActiveSupport::Deprecation.warn \
-            "Defining #quoted_id is deprecated and will be ignored in Rails 5.2. (defined on #{klass}#{at})"
-          return value.quoted_id
-        end
-
         if value.respond_to?(:value_for_database)
           value = value.value_for_database
         end
@@ -37,10 +24,6 @@ module ActiveRecord
       def type_cast(value, column = nil)
         value = id_value_for_database(value) if value.is_a?(Base)
 
-        if value.respond_to?(:quoted_id) && value.respond_to?(:id)
-          return value.id
-        end
-
         if column
           value = type_cast_from_column(column, value)
         end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 788a455773..0594b4b485 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -6,7 +6,7 @@ module ActiveRecord
     # this type are typically created and returned by methods in database
     # adapters. e.g. ActiveRecord::ConnectionAdapters::MySQL::SchemaStatements#indexes
     class IndexDefinition # :nodoc:
-      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :where, :type, :using, :comment
+      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :opclasses, :where, :type, :using, :comment
 
       def initialize(
         table, name,
@@ -14,6 +14,7 @@ module ActiveRecord
         columns = [],
         lengths: {},
         orders: {},
+        opclasses: {},
         where: nil,
         type: nil,
         using: nil,
@@ -23,13 +24,23 @@ module ActiveRecord
         @name = name
         @unique = unique
         @columns = columns
-        @lengths = lengths
-        @orders = orders
+        @lengths = concise_options(lengths)
+        @orders = concise_options(orders)
+        @opclasses = concise_options(opclasses)
         @where = where
         @type = type
         @using = using
         @comment = comment
       end
+
+      private
+        def concise_options(options)
+          if columns.size == options.size && options.values.uniq.size == 1
+            options.values.first
+          else
+            options
+          end
+        end
     end
 
     # Abstract representation of a column definition. Instances of this type
@@ -85,6 +96,11 @@ module ActiveRecord
         options[:primary_key] != default_primary_key
       end
 
+      def validate?
+        options.fetch(:validate, true)
+      end
+      alias validated? validate?
+
       def defined_for?(to_table_ord = nil, to_table: nil, **options)
         if to_table_ord
           self.to_table == to_table_ord.to_s
@@ -204,6 +220,7 @@ module ActiveRecord
         :decimal,
         :float,
         :integer,
+        :json,
         :string,
         :text,
         :time,
@@ -396,6 +413,9 @@ module ActiveRecord
       alias :belongs_to :references
 
       def new_column_definition(name, type, **options) # :nodoc:
+        if integer_like_primary_key?(type, options)
+          type = integer_like_primary_key_type(type, options)
+        end
         type = aliased_types(type.to_s, type)
         options[:primary_key] ||= type == :primary_key
         options[:null] = false if options[:primary_key]
@@ -410,6 +430,14 @@ module ActiveRecord
         def aliased_types(name, fallback)
           "timestamp" == name ? :datetime : fallback
         end
+
+        def integer_like_primary_key?(type, options)
+          options[:primary_key] && [:integer, :bigint].include?(type) && !options.key?(:default)
+        end
+
+        def integer_like_primary_key_type(type, options)
+          type
+        end
     end
 
     class AlterTable # :nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index f57c7a5d4d..4f58b0242c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../migration/join_table"
+require "active_record/migration/join_table"
 require "active_support/core_ext/string/access"
-require "digest"
+require "digest/sha2"
 
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
@@ -79,7 +79,7 @@ module ActiveRecord
       end
 
       # Returns an array of indexes for the given table.
-      def indexes(table_name, name = nil)
+      def indexes(table_name)
         raise NotImplementedError, "#indexes is not implemented"
       end
 
@@ -216,7 +216,7 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE suppliers (
-      #     id int auto_increment PRIMARY KEY
+      #     id bigint auto_increment PRIMARY KEY
       #   ) ENGINE=InnoDB DEFAULT CHARSET=utf8
       #
       # ====== Rename the primary key column
@@ -228,7 +228,7 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE objects (
-      #     guid int auto_increment PRIMARY KEY,
+      #     guid bigint auto_increment PRIMARY KEY,
       #     name varchar(80)
       #   )
       #
@@ -255,8 +255,8 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE order (
-      #       product_id integer NOT NULL,
-      #       client_id integer NOT NULL
+      #       product_id bigint NOT NULL,
+      #       client_id bigint NOT NULL
       #   );
       #
       #   ALTER TABLE ONLY "orders"
@@ -265,15 +265,15 @@ module ActiveRecord
       # ====== Do not add a primary key column
       #
       #   create_table(:categories_suppliers, id: false) do |t|
-      #     t.column :category_id, :integer
-      #     t.column :supplier_id, :integer
+      #     t.column :category_id, :bigint
+      #     t.column :supplier_id, :bigint
       #   end
       #
       # generates:
       #
       #   CREATE TABLE categories_suppliers (
-      #     category_id int,
-      #     supplier_id int
+      #     category_id bigint,
+      #     supplier_id bigint
       #   )
       #
       # ====== Create a temporary table based on a query
@@ -361,8 +361,8 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE assemblies_parts (
-      #     assembly_id int NOT NULL,
-      #     part_id int NOT NULL,
+      #     assembly_id bigint NOT NULL,
+      #     part_id bigint NOT NULL,
       #   ) ENGINE=InnoDB DEFAULT CHARSET=utf8
       #
       def create_join_table(table_1, table_2, column_options: {}, **options)
@@ -432,7 +432,7 @@ module ActiveRecord
       #     t.references :company
       #   end
       #
-      # Creates a <tt>company_id(integer)</tt> column.
+      # Creates a <tt>company_id(bigint)</tt> column.
       #
       # ====== Add a polymorphic foreign key column
       #
@@ -440,7 +440,7 @@ module ActiveRecord
       #    t.belongs_to :company, polymorphic: true
       #  end
       #
-      # Creates <tt>company_type(varchar)</tt> and <tt>company_id(integer)</tt> columns.
+      # Creates <tt>company_type(varchar)</tt> and <tt>company_id(bigint)</tt> columns.
       #
       # ====== Remove a column
       #
@@ -522,6 +522,8 @@ module ActiveRecord
       #   Specifies the precision for the <tt>:decimal</tt> and <tt>:numeric</tt> columns.
       # * <tt>:scale</tt> -
       #   Specifies the scale for the <tt>:decimal</tt> and <tt>:numeric</tt> columns.
+      # * <tt>:comment</tt> -
+      #   Specifies the comment for the column. This option is ignored by some backends.
       #
       # Note: The precision is the total number of significant digits,
       # and the scale is the number of digits that can be stored following
@@ -598,7 +600,7 @@ module ActiveRecord
       # to provide these in a migration's +change+ method so it can be reverted.
       # In that case, +type+ and +options+ will be used by #add_column.
       def remove_column(table_name, column_name, type = nil, options = {})
-        execute "ALTER TABLE #{quote_table_name(table_name)} DROP #{quote_column_name(column_name)}"
+        execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_for_alter(table_name, column_name, type, options)}"
       end
 
       # Changes the column's definition according to the new options.
@@ -736,6 +738,28 @@ module ActiveRecord
       #
       # Note: only supported by PostgreSQL and MySQL
       #
+      # ====== Creating an index with a specific operator class
+      #
+      #   add_index(:developers, :name, using: 'gist', opclass: :gist_trgm_ops)
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name ON developers USING gist (name gist_trgm_ops) -- PostgreSQL
+      #
+      #   add_index(:developers, [:name, :city], using: 'gist', opclass: { city: :gist_trgm_ops })
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name_and_city ON developers USING gist (name, city gist_trgm_ops) -- PostgreSQL
+      #
+      #   add_index(:developers, [:name, :city], using: 'gist', opclass: :gist_trgm_ops)
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name_and_city ON developers USING gist (name gist_trgm_ops, city gist_trgm_ops) -- PostgreSQL
+      #
+      # Note: only supported by PostgreSQL
+      #
       # ====== Creating an index with a specific type
       #
       #   add_index(:developers, :name, type: :fulltext)
@@ -804,24 +828,19 @@ module ActiveRecord
       end
 
       # Verifies the existence of an index with a given name.
-      def index_name_exists?(table_name, index_name, default = nil)
-        unless default.nil?
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Passing default to #index_name_exists? is deprecated without replacement.
-          MSG
-        end
+      def index_name_exists?(table_name, index_name)
         index_name = index_name.to_s
         indexes(table_name).detect { |i| i.name == index_name }
       end
 
-      # Adds a reference. The reference column is an integer by default,
+      # Adds a reference. The reference column is a bigint by default,
       # the <tt>:type</tt> option can be used to specify a different type.
       # Optionally adds a +_type+ column, if <tt>:polymorphic</tt> option is provided.
       # #add_reference and #add_belongs_to are acceptable.
       #
       # The +options+ hash can include the following keys:
       # [<tt>:type</tt>]
-      #   The reference column type. Defaults to +:integer+.
+      #   The reference column type. Defaults to +:bigint+.
       # [<tt>:index</tt>]
       #   Add an appropriate index. Defaults to true.
       #   See #add_index for usage of this option.
@@ -832,7 +851,7 @@ module ActiveRecord
       # [<tt>:null</tt>]
       #   Whether the column allows nulls. Defaults to true.
       #
-      # ====== Create a user_id integer column
+      # ====== Create a user_id bigint column
       #
       #   add_reference(:products, :user)
       #
@@ -945,6 +964,8 @@ module ActiveRecord
       #   Action that happens <tt>ON DELETE</tt>. Valid values are +:nullify+, +:cascade+ and +:restrict+
       # [<tt>:on_update</tt>]
       #   Action that happens <tt>ON UPDATE</tt>. Valid values are +:nullify+, +:cascade+ and +:restrict+
+      # [<tt>:validate</tt>]
+      #   (Postgres only) Specify whether or not the constraint should be validated. Defaults to +true+.
       def add_foreign_key(from_table, to_table, options = {})
         return unless supports_foreign_keys?
 
@@ -1018,16 +1039,6 @@ module ActiveRecord
         insert_versions_sql(versions) if versions.any?
       end
 
-      def initialize_schema_migrations_table # :nodoc:
-        ActiveRecord::SchemaMigration.create_table
-      end
-      deprecate :initialize_schema_migrations_table
-
-      def initialize_internal_metadata_table # :nodoc:
-        ActiveRecord::InternalMetadata.create_table
-      end
-      deprecate :initialize_internal_metadata_table
-
       def internal_string_options_for_primary_key # :nodoc:
         { primary_key: true }
       end
@@ -1133,7 +1144,7 @@ module ActiveRecord
       def add_index_options(table_name, column_name, comment: nil, **options) # :nodoc:
         column_names = index_column_names(column_name)
 
-        options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type)
+        options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type, :opclass)
 
         index_type = options[:type].to_s if options.key?(:type)
         index_type ||= options[:unique] ? "UNIQUE" : ""
@@ -1172,7 +1183,7 @@ module ActiveRecord
       end
 
       # Changes the comment for a column or removes it if +nil+.
-      def change_column_comment(table_name, column_name, comment) #:nodoc:
+      def change_column_comment(table_name, column_name, comment)
         raise NotImplementedError, "#{self.class} does not support changing column comments"
       end
 
@@ -1186,20 +1197,22 @@ module ActiveRecord
         end
 
         def add_index_sort_order(quoted_columns, **options)
-          if order = options[:order]
-            case order
-            when Hash
-              order = order.symbolize_keys
-              quoted_columns.each { |name, column| column << " #{order[name].upcase}" if order[name].present? }
-            when String
-              quoted_columns.each { |name, column| column << " #{order.upcase}" if order.present? }
-            end
+          orders = options_for_index_columns(options[:order])
+          quoted_columns.each do |name, column|
+            column << " #{orders[name].upcase}" if orders[name].present?
           end
+        end
 
-          quoted_columns
+        def options_for_index_columns(options)
+          if options.is_a?(Hash)
+            options.symbolize_keys
+          else
+            Hash.new { |hash, column| hash[column] = options }
+          end
         end
 
-        # Overridden by the MySQL adapter for supporting index lengths
+        # Overridden by the MySQL adapter for supporting index lengths and by
+        # the PostgreSQL adapter for supporting operator classes.
         def add_options_for_index_columns(quoted_columns, **options)
           if supports_index_sort_order?
             quoted_columns = add_index_sort_order(quoted_columns, options)
@@ -1353,6 +1366,20 @@ module ActiveRecord
           options.is_a?(Hash) && options.key?(:name) && options.except(:name, :algorithm).empty?
         end
 
+        def add_column_for_alter(table_name, column_name, type, options = {})
+          td = create_table_definition(table_name)
+          cd = td.new_column_definition(column_name, type, options)
+          schema_creation.accept(AddColumnDefinition.new(cd))
+        end
+
+        def remove_column_for_alter(table_name, column_name, type = nil, options = {})
+          "DROP COLUMN #{quote_column_name(column_name)}"
+        end
+
+        def remove_columns_for_alter(table_name, *column_names)
+          column_names.map { |column_name| remove_column_for_alter(table_name, column_name) }
+        end
+
         def insert_versions_sql(versions)
           sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name)
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index 147e16e9fa..d9ac8db6a8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -240,7 +240,7 @@ module ActiveRecord
                 rollback_transaction if transaction
               else
                 begin
-                  commit_transaction
+                  commit_transaction if transaction
                 rescue Exception
                   rollback_transaction(transaction) unless transaction.state.completed?
                   raise
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 8c889f98f5..fc80d332f9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "../type"
-require_relative "determine_if_preparable_visitor"
-require_relative "schema_cache"
-require_relative "sql_type_metadata"
-require_relative "abstract/schema_dumper"
-require_relative "abstract/schema_creation"
+require "active_record/connection_adapters/determine_if_preparable_visitor"
+require "active_record/connection_adapters/schema_cache"
+require "active_record/connection_adapters/sql_type_metadata"
+require "active_record/connection_adapters/abstract/schema_dumper"
+require "active_record/connection_adapters/abstract/schema_creation"
+require "active_support/concurrency/load_interlock_aware_monitor"
 require "arel/collectors/bind"
 require "arel/collectors/composite"
 require "arel/collectors/sql_string"
@@ -105,10 +105,11 @@ module ActiveRecord
         @logger              = logger
         @config              = config
         @pool                = nil
+        @idle_since          = Concurrent.monotonic_time
         @schema_cache        = SchemaCache.new self
         @quoted_column_names, @quoted_table_names = {}, {}
         @visitor = arel_visitor
-        @lock = Monitor.new
+        @lock = ActiveSupport::Concurrency::LoadInterlockAwareMonitor.new
 
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
           @prepared_statements = true
@@ -164,6 +165,7 @@ module ActiveRecord
               "Current thread: #{Thread.current}."
           end
 
+          @idle_since = Concurrent.monotonic_time
           @owner = nil
         else
           raise ActiveRecordError, "Cannot expire connection, it is not currently leased."
@@ -183,6 +185,12 @@ module ActiveRecord
         end
       end
 
+      # Seconds since this connection was returned to the pool
+      def seconds_idle # :nodoc:
+        return 0 if in_use?
+        Concurrent.monotonic_time - @idle_since
+      end
+
       def unprepared_statement
         old_prepared_statements, @prepared_statements = @prepared_statements, false
         yield
@@ -196,16 +204,6 @@ module ActiveRecord
         self.class::ADAPTER_NAME
       end
 
-      def supports_migrations? # :nodoc:
-        true
-      end
-      deprecate :supports_migrations?
-
-      def supports_primary_key? # :nodoc:
-        true
-      end
-      deprecate :supports_primary_key?
-
       # Does this adapter support DDL rollbacks in transactions? That is, would
       # CREATE TABLE or ALTER TABLE get rolled back by a transaction?
       def supports_ddl_transactions?
@@ -274,6 +272,11 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support creating invalid constraints?
+      def supports_validate_constraints?
+        false
+      end
+
       # Does this adapter support creating foreign key constraints
       # in the same statement as creating the table?
       def supports_foreign_keys_in_create?
@@ -377,6 +380,19 @@ module ActiveRecord
         reset_transaction
       end
 
+      # Immediately forget this connection ever existed. Unlike disconnect!,
+      # this will not communicate with the server.
+      #
+      # After calling this method, the behavior of all other methods becomes
+      # undefined. This is called internally just before a forked process gets
+      # rid of a connection that belonged to its parent.
+      def discard!
+        # This should be overridden by concrete adapters.
+        #
+        # Prevent @connection's finalizer from touching the socket, or
+        # otherwise communicating with its server, when it is collected.
+      end
+
       # Reset the state of this connection, directing the DBMS to clear
       # transactions and other connection-related server-side state. Usually a
       # database-dependent operation.
@@ -402,10 +418,7 @@ module ActiveRecord
       # Checks whether the connection to the database is still active (i.e. not stale).
       # This is done under the hood by calling #active?. If the connection
       # is no longer active, then this method will reconnect to the database.
-      def verify!(*ignored)
-        if ignored.size > 0
-          ActiveSupport::Deprecation.warn("Passing arguments to #verify method of the connection has no effect and has been deprecated. Please remove all arguments from the #verify method call.")
-        end
+      def verify!
         reconnect! unless active?
       end
 
@@ -478,6 +491,8 @@ module ActiveRecord
           m.alias_type %r(number)i,    "decimal"
           m.alias_type %r(double)i,    "float"
 
+          m.register_type %r(^json)i, Type::Json.new
+
           m.register_type(%r(decimal)i) do |sql_type|
             scale = extract_scale(sql_type)
             precision = extract_precision(sql_type)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 7cd086084a..479131caad 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "abstract_adapter"
-require_relative "statement_pool"
-require_relative "mysql/column"
-require_relative "mysql/explain_pretty_printer"
-require_relative "mysql/quoting"
-require_relative "mysql/schema_creation"
-require_relative "mysql/schema_definitions"
-require_relative "mysql/schema_dumper"
-require_relative "mysql/schema_statements"
-require_relative "mysql/type_metadata"
+require "active_record/connection_adapters/abstract_adapter"
+require "active_record/connection_adapters/statement_pool"
+require "active_record/connection_adapters/mysql/column"
+require "active_record/connection_adapters/mysql/explain_pretty_printer"
+require "active_record/connection_adapters/mysql/quoting"
+require "active_record/connection_adapters/mysql/schema_creation"
+require "active_record/connection_adapters/mysql/schema_definitions"
+require "active_record/connection_adapters/mysql/schema_dumper"
+require "active_record/connection_adapters/mysql/schema_statements"
+require "active_record/connection_adapters/mysql/type_metadata"
 
 require "active_support/core_ext/string/strip"
 
@@ -44,7 +44,7 @@ module ActiveRecord
         json:        { name: "json" },
       }
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         private def dealloc(stmt)
           stmt[:stmt].close
         end
@@ -284,7 +284,7 @@ module ActiveRecord
       def table_comment(table_name) # :nodoc:
         scope = quoted_scope(table_name)
 
-        query_value(<<-SQL.strip_heredoc, "SCHEMA")
+        query_value(<<-SQL.strip_heredoc, "SCHEMA").presence
           SELECT table_comment
           FROM information_schema.tables
           WHERE table_schema = #{scope[:schema]}
@@ -299,7 +299,7 @@ module ActiveRecord
       def bulk_change_table(table_name, operations) #:nodoc:
         sqls = operations.flat_map do |command, args|
           table, arguments = args.shift, args
-          method = :"#{command}_sql"
+          method = :"#{command}_for_alter"
 
           if respond_to?(method, true)
             send(method, table, *arguments)
@@ -311,6 +311,11 @@ module ActiveRecord
         execute("ALTER TABLE #{quote_table_name(table_name)} #{sqls}")
       end
 
+      def change_table_comment(table_name, comment) #:nodoc:
+        comment = "" if comment.nil?
+        execute("ALTER TABLE #{quote_table_name(table_name)} COMMENT #{quote(comment)}")
+      end
+
       # Renames a table.
       #
       # Example:
@@ -351,26 +356,27 @@ module ActiveRecord
 
       def change_column_default(table_name, column_name, default_or_changes) #:nodoc:
         default = extract_new_default_value(default_or_changes)
-        column = column_for(table_name, column_name)
-        change_column table_name, column_name, column.sql_type, default: default
+        change_column table_name, column_name, nil, default: default
       end
 
       def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
-        column = column_for(table_name, column_name)
-
         unless null || default.nil?
           execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
         end
 
-        change_column table_name, column_name, column.sql_type, null: null
+        change_column table_name, column_name, nil, null: null
+      end
+
+      def change_column_comment(table_name, column_name, comment) #:nodoc:
+        change_column table_name, column_name, nil, comment: comment
       end
 
       def change_column(table_name, column_name, type, options = {}) #:nodoc:
-        execute("ALTER TABLE #{quote_table_name(table_name)} #{change_column_sql(table_name, column_name, type, options)}")
+        execute("ALTER TABLE #{quote_table_name(table_name)} #{change_column_for_alter(table_name, column_name, type, options)}")
       end
 
       def rename_column(table_name, column_name, new_column_name) #:nodoc:
-        execute("ALTER TABLE #{quote_table_name(table_name)} #{rename_column_sql(table_name, column_name, new_column_name)}")
+        execute("ALTER TABLE #{quote_table_name(table_name)} #{rename_column_for_alter(table_name, column_name, new_column_name)}")
         rename_column_indexes(table_name, column_name, new_column_name)
       end
 
@@ -557,7 +563,6 @@ module ActiveRecord
           m.register_type %r(longblob)i,   Type::Binary.new(limit: 2**32 - 1)
           m.register_type %r(^float)i,     Type::Float.new(limit: 24)
           m.register_type %r(^double)i,    Type::Float.new(limit: 53)
-          m.register_type %r(^json)i,      Type::Json.new
 
           register_integer_type m, %r(^bigint)i,    limit: 8
           register_integer_type m, %r(^int)i,       limit: 4
@@ -600,25 +605,6 @@ module ActiveRecord
           end
         end
 
-        def add_index_length(quoted_columns, **options)
-          if length = options[:length]
-            case length
-            when Hash
-              length = length.symbolize_keys
-              quoted_columns.each { |name, column| column << "(#{length[name]})" if length[name].present? }
-            when Integer
-              quoted_columns.each { |name, column| column << "(#{length})" }
-            end
-          end
-
-          quoted_columns
-        end
-
-        def add_options_for_index_columns(quoted_columns, **options)
-          quoted_columns = add_index_length(quoted_columns, options)
-          super
-        end
-
         # See https://dev.mysql.com/doc/refman/5.7/en/error-messages-server.html
         ER_DUP_ENTRY            = 1062
         ER_NOT_NULL_VIOLATION   = 1048
@@ -630,6 +616,8 @@ module ActiveRecord
         ER_CANNOT_ADD_FOREIGN   = 1215
         ER_CANNOT_CREATE_TABLE  = 1005
         ER_LOCK_WAIT_TIMEOUT    = 1205
+        ER_QUERY_INTERRUPTED    = 1317
+        ER_QUERY_TIMEOUT        = 3024
 
         def translate_exception(exception, message)
           case error_number(exception)
@@ -654,20 +642,19 @@ module ActiveRecord
           when ER_LOCK_DEADLOCK
             Deadlocked.new(message)
           when ER_LOCK_WAIT_TIMEOUT
-            TransactionTimeout.new(message)
+            LockWaitTimeout.new(message)
+          when ER_QUERY_TIMEOUT
+            StatementTimeout.new(message)
+          when ER_QUERY_INTERRUPTED
+            QueryCanceled.new(message)
           else
             super
           end
         end
 
-        def add_column_sql(table_name, column_name, type, options = {})
-          td = create_table_definition(table_name)
-          cd = td.new_column_definition(column_name, type, options)
-          schema_creation.accept(AddColumnDefinition.new(cd))
-        end
-
-        def change_column_sql(table_name, column_name, type, options = {})
+        def change_column_for_alter(table_name, column_name, type, options = {})
           column = column_for(table_name, column_name)
+          type ||= column.sql_type
 
           unless options.key?(:default)
             options[:default] = column.default
@@ -686,7 +673,7 @@ module ActiveRecord
           schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
         end
 
-        def rename_column_sql(table_name, column_name, new_column_name)
+        def rename_column_for_alter(table_name, column_name, new_column_name)
           column  = column_for(table_name, column_name)
           options = {
             default: column.default,
@@ -700,31 +687,23 @@ module ActiveRecord
           schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
         end
 
-        def remove_column_sql(table_name, column_name, type = nil, options = {})
-          "DROP #{quote_column_name(column_name)}"
-        end
-
-        def remove_columns_sql(table_name, *column_names)
-          column_names.map { |column_name| remove_column_sql(table_name, column_name) }
-        end
-
-        def add_index_sql(table_name, column_name, options = {})
+        def add_index_for_alter(table_name, column_name, options = {})
           index_name, index_type, index_columns, _, index_algorithm, index_using = add_index_options(table_name, column_name, options)
           index_algorithm[0, 0] = ", " if index_algorithm.present?
           "ADD #{index_type} INDEX #{quote_column_name(index_name)} #{index_using} (#{index_columns})#{index_algorithm}"
         end
 
-        def remove_index_sql(table_name, options = {})
+        def remove_index_for_alter(table_name, options = {})
           index_name = index_name_for_remove(table_name, options)
-          "DROP INDEX #{index_name}"
+          "DROP INDEX #{quote_column_name(index_name)}"
         end
 
-        def add_timestamps_sql(table_name, options = {})
-          [add_column_sql(table_name, :created_at, :datetime, options), add_column_sql(table_name, :updated_at, :datetime, options)]
+        def add_timestamps_for_alter(table_name, options = {})
+          [add_column_for_alter(table_name, :created_at, :datetime, options), add_column_for_alter(table_name, :updated_at, :datetime, options)]
         end
 
-        def remove_timestamps_sql(table_name, options = {})
-          [remove_column_sql(table_name, :updated_at), remove_column_sql(table_name, :created_at)]
+        def remove_timestamps_for_alter(table_name, options = {})
+          [remove_column_for_alter(table_name, :updated_at), remove_column_for_alter(table_name, :created_at)]
         end
 
         # MySQL is too stupid to create a temporary table for use subquery, so we have
diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index 16273fb5f1..5d81de9fe1 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -11,11 +11,11 @@ module ActiveRecord
 
       # Instantiates a new column in the table.
       #
-      # +name+ is the column's name, such as <tt>supplier_id</tt> in <tt>supplier_id int</tt>.
+      # +name+ is the column's name, such as <tt>supplier_id</tt> in <tt>supplier_id bigint</tt>.
       # +default+ is the type-casted default value, such as +new+ in <tt>sales_stage varchar(20) default 'new'</tt>.
       # +sql_type_metadata+ is various information about the type of the column
       # +null+ determines if this column allows +NULL+ values.
-      def initialize(name, default, sql_type_metadata = nil, null = true, table_name = nil, default_function = nil, collation = nil, comment: nil)
+      def initialize(name, default, sql_type_metadata = nil, null = true, table_name = nil, default_function = nil, collation = nil, comment: nil, **)
         @name = name.freeze
         @table_name = table_name
         @sql_type_metadata = sql_type_metadata
diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index 29542f917e..508132accb 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -183,13 +183,25 @@ module ActiveRecord
 
           raise(AdapterNotSpecified, "database configuration does not specify adapter") unless spec.key?(:adapter)
 
+          # Require the adapter itself and give useful feedback about
+          #   1. Missing adapter gems and
+          #   2. Adapter gems' missing dependencies.
           path_to_adapter = "active_record/connection_adapters/#{spec[:adapter]}_adapter"
           begin
             require path_to_adapter
-          rescue Gem::LoadError => e
-            raise Gem::LoadError, "Specified '#{spec[:adapter]}' for database adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord)."
           rescue LoadError => e
-            raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.", e.backtrace
+            # We couldn't require the adapter itself. Raise an exception that
+            # points out config typos and missing gems.
+            if e.path == path_to_adapter
+              # We can assume that a non-builtin adapter was specified, so it's
+              # either misspelled or missing from Gemfile.
+              raise e.class, "Could not load the '#{spec[:adapter]}' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
+
+            # Bubbled up from the adapter require. Prefix the exception message
+            # with some guidance about how to address it and reraise.
+            else
+              raise e.class, "Error loading the '#{spec[:adapter]}' Active Record adapter. Missing a gem it depends on? #{e.message}", e.backtrace
+            end
           end
 
           adapter_method = "#{spec[:adapter]}_connection"
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
index b22a2e4da7..2ed4ad16ae 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
@@ -4,11 +4,6 @@ module ActiveRecord
   module ConnectionAdapters
     module MySQL
       module ColumnMethods
-        def primary_key(name, type = :primary_key, **options)
-          options[:auto_increment] = true if [:integer, :bigint].include?(type) && !options.key?(:default)
-          super
-        end
-
         def blob(*args, **options)
           args.each { |name| column(name, :blob, options) }
         end
@@ -37,10 +32,6 @@ module ActiveRecord
           args.each { |name| column(name, :longtext, options) }
         end
 
-        def json(*args, **options)
-          args.each { |name| column(name, :json, options) }
-        end
-
         def unsigned_integer(*args, **options)
           args.each { |name| column(name, :unsigned_integer, options) }
         end
@@ -68,7 +59,6 @@ module ActiveRecord
           when :primary_key
             type = :integer
             options[:limit] ||= 8
-            options[:auto_increment] = true
             options[:primary_key] = true
           when /\Aunsigned_(?<type>.+)\z/
             type = $~[:type].to_sym
@@ -82,6 +72,11 @@ module ActiveRecord
           def aliased_types(name, fallback)
             fallback
           end
+
+          def integer_like_primary_key_type(type, options)
+            options[:auto_increment] = true
+            type
+          end
       end
 
       class Table < ActiveRecord::ConnectionAdapters::Table
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
index 95eb77aea4..d23178e43c 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -8,6 +8,7 @@ module ActiveRecord
           def prepare_column_options(column)
             spec = super
             spec[:unsigned] = "true" if column.unsigned?
+            spec[:auto_increment] = "true" if column.auto_increment?
 
             if @connection.supports_virtual_columns? && column.virtual?
               spec[:as] = extract_expression_for_virtual_column(column)
@@ -18,6 +19,12 @@ module ActiveRecord
             spec
           end
 
+          def column_spec_for_primary_key(column)
+            spec = super
+            spec.delete(:auto_increment) if column.type == :integer && column.auto_increment?
+            spec
+          end
+
           def default_primary_key?(column)
             super && column.auto_increment? && !column.unsigned?
           end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
index 759493e3bd..ce50590651 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -5,13 +5,7 @@ module ActiveRecord
     module MySQL
       module SchemaStatements # :nodoc:
         # Returns an array of indexes for the given table.
-        def indexes(table_name, name = nil)
-          if name
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing name to #indexes is deprecated without replacement.
-            MSG
-          end
-
+        def indexes(table_name)
           indexes = []
           current_index = nil
           execute_and_free("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA") do |result|
@@ -28,23 +22,26 @@ module ActiveRecord
                   index_using = mysql_index_type
                 end
 
-                indexes << IndexDefinition.new(
+                indexes << [
                   row[:Table],
                   row[:Key_name],
                   row[:Non_unique].to_i == 0,
+                  [],
+                  lengths: {},
+                  orders: {},
                   type: index_type,
                   using: index_using,
                   comment: row[:Index_comment].presence
-                )
+                ]
               end
 
-              indexes.last.columns << row[:Column_name]
-              indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
-              indexes.last.orders.merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
+              indexes.last[-2] << row[:Column_name]
+              indexes.last[-1][:lengths].merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
+              indexes.last[-1][:orders].merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
             end
           end
 
-          indexes
+          indexes.map { |index| IndexDefinition.new(*index) }
         end
 
         def remove_column(table_name, column_name, type = nil, options = {})
@@ -109,6 +106,18 @@ module ActiveRecord
             super unless specifier == "RESTRICT"
           end
 
+          def add_index_length(quoted_columns, **options)
+            lengths = options_for_index_columns(options[:length])
+            quoted_columns.each do |name, column|
+              column << "(#{lengths[name]})" if lengths[name].present?
+            end
+          end
+
+          def add_options_for_index_columns(quoted_columns, **options)
+            quoted_columns = add_index_length(quoted_columns, options)
+            super
+          end
+
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
 
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index 2c2321872d..bfdc7995f0 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -1,11 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "abstract_mysql_adapter"
-require_relative "mysql/database_statements"
+require "active_record/connection_adapters/abstract_mysql_adapter"
+require "active_record/connection_adapters/mysql/database_statements"
 
-gem "mysql2", ">= 0.3.18", "< 0.5"
+gem "mysql2", "~> 0.4.4"
 require "mysql2"
-raise "mysql2 0.4.3 is not supported. Please upgrade to 0.4.4+" if Mysql2::VERSION == "0.4.3"
 
 module ActiveRecord
   module ConnectionHandling # :nodoc:
@@ -105,6 +104,11 @@ module ActiveRecord
         @connection.close
       end
 
+      def discard! # :nodoc:
+        @connection.automatic_close = false
+        @connection = nil
+      end
+
       private
 
         def connect
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 1b67cee24b..469ef3f5a0 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -7,11 +7,38 @@ module ActiveRecord
       delegate :array, :oid, :fmod, to: :sql_type_metadata
       alias :array? :array
 
+      def initialize(*, max_identifier_length: 63, **)
+        super
+        @max_identifier_length = max_identifier_length
+      end
+
       def serial?
         return unless default_function
 
-        %r{\Anextval\('"?#{table_name}_#{name}_seq"?'::regclass\)\z} === default_function
+        if %r{\Anextval\('"?(?<sequence_name>.+_(?<suffix>seq\d*))"?'::regclass\)\z} =~ default_function
+          sequence_name_from_parts(table_name, name, suffix) == sequence_name
+        end
       end
+
+      protected
+        attr_reader :max_identifier_length
+
+      private
+        def sequence_name_from_parts(table_name, column_name, suffix)
+          over_length = [table_name, column_name, suffix].map(&:length).sum + 2 - max_identifier_length
+
+          if over_length > 0
+            column_name_length = [(max_identifier_length - suffix.length - 2) / 2, column_name.length].min
+            over_length -= column_name.length - column_name_length
+            column_name = column_name[0, column_name_length - [over_length, 0].min]
+          end
+
+          if over_length > 0
+            table_name = table_name[0, table_name.length - over_length]
+          end
+
+          "#{table_name}_#{column_name}_#{suffix}"
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index b28418d74f..542ca75d3e 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -1,27 +1,27 @@
 # frozen_string_literal: true
 
-require_relative "oid/array"
-require_relative "oid/bit"
-require_relative "oid/bit_varying"
-require_relative "oid/bytea"
-require_relative "oid/cidr"
-require_relative "oid/date_time"
-require_relative "oid/decimal"
-require_relative "oid/enum"
-require_relative "oid/hstore"
-require_relative "oid/inet"
-require_relative "oid/jsonb"
-require_relative "oid/money"
-require_relative "oid/oid"
-require_relative "oid/point"
-require_relative "oid/legacy_point"
-require_relative "oid/range"
-require_relative "oid/specialized_string"
-require_relative "oid/uuid"
-require_relative "oid/vector"
-require_relative "oid/xml"
+require "active_record/connection_adapters/postgresql/oid/array"
+require "active_record/connection_adapters/postgresql/oid/bit"
+require "active_record/connection_adapters/postgresql/oid/bit_varying"
+require "active_record/connection_adapters/postgresql/oid/bytea"
+require "active_record/connection_adapters/postgresql/oid/cidr"
+require "active_record/connection_adapters/postgresql/oid/date_time"
+require "active_record/connection_adapters/postgresql/oid/decimal"
+require "active_record/connection_adapters/postgresql/oid/enum"
+require "active_record/connection_adapters/postgresql/oid/hstore"
+require "active_record/connection_adapters/postgresql/oid/inet"
+require "active_record/connection_adapters/postgresql/oid/jsonb"
+require "active_record/connection_adapters/postgresql/oid/money"
+require "active_record/connection_adapters/postgresql/oid/oid"
+require "active_record/connection_adapters/postgresql/oid/point"
+require "active_record/connection_adapters/postgresql/oid/legacy_point"
+require "active_record/connection_adapters/postgresql/oid/range"
+require "active_record/connection_adapters/postgresql/oid/specialized_string"
+require "active_record/connection_adapters/postgresql/oid/uuid"
+require "active_record/connection_adapters/postgresql/oid/vector"
+require "active_record/connection_adapters/postgresql/oid/xml"
 
-require_relative "oid/type_map_initializer"
+require "active_record/connection_adapters/postgresql/oid/type_map_initializer"
 
 module ActiveRecord
   module ConnectionAdapters
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
index 7d5d7d91e6..a89aa5ea09 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
@@ -35,7 +35,7 @@ module ActiveRecord
             if value.is_a?(::Range)
               from = type_cast_single_for_database(value.begin)
               to = type_cast_single_for_database(value.end)
-              "[#{from},#{to}#{value.exclude_end? ? ')' : ']'}"
+              ::Range.new(from, to, value.exclude_end?)
             else
               super
             end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index a0a22ba0f1..9fdeab06c1 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -101,6 +101,8 @@ module ActiveRecord
               end
             when OID::Array::Data
               _quote(encode_array(value))
+            when Range
+              _quote(encode_range(value))
             else
               super
             end
@@ -117,6 +119,8 @@ module ActiveRecord
               value.to_s
             when OID::Array::Data
               encode_array(value)
+            when Range
+              encode_range(value)
             else
               super
             end
@@ -133,6 +137,10 @@ module ActiveRecord
             result
           end
 
+          def encode_range(range)
+            "[#{type_cast(range.first)},#{type_cast(range.last)}#{range.exclude_end? ? ')' : ']'}"
+          end
+
           def determine_encoding_of_strings_in_array(value)
             case value
             when ::Array then determine_encoding_of_strings_in_array(value.first)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
index 386d22a9bd..8df91c988b 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
@@ -4,26 +4,21 @@ module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
       module ReferentialIntegrity # :nodoc:
-        def supports_disable_referential_integrity? # :nodoc:
-          true
-        end
-
         def disable_referential_integrity # :nodoc:
-          if supports_disable_referential_integrity?
-            original_exception = nil
+          original_exception = nil
 
-            begin
-              transaction(requires_new: true) do
-                execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} DISABLE TRIGGER ALL" }.join(";"))
-              end
-            rescue ActiveRecord::ActiveRecordError => e
-              original_exception = e
+          begin
+            transaction(requires_new: true) do
+              execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} DISABLE TRIGGER ALL" }.join(";"))
             end
+          rescue ActiveRecord::ActiveRecordError => e
+            original_exception = e
+          end
 
-            begin
-              yield
-            rescue ActiveRecord::InvalidForeignKey => e
-              warn <<-WARNING
+          begin
+            yield
+          rescue ActiveRecord::InvalidForeignKey => e
+            warn <<-WARNING
 WARNING: Rails was not able to disable referential integrity.
 
 This is most likely caused due to missing permissions.
@@ -32,17 +27,14 @@ Rails needs superuser privileges to disable referential integrity.
     cause: #{original_exception.try(:message)}
 
               WARNING
-              raise e
-            end
+            raise e
+          end
 
-            begin
-              transaction(requires_new: true) do
-                execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} ENABLE TRIGGER ALL" }.join(";"))
-              end
-            rescue ActiveRecord::ActiveRecordError
+          begin
+            transaction(requires_new: true) do
+              execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} ENABLE TRIGGER ALL" }.join(";"))
             end
-          else
-            yield
+          rescue ActiveRecord::ActiveRecordError
           end
         end
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
index 59f661da25..8e381a92cf 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
@@ -5,6 +5,18 @@ module ActiveRecord
     module PostgreSQL
       class SchemaCreation < AbstractAdapter::SchemaCreation # :nodoc:
         private
+          def visit_AlterTable(o)
+            super << o.constraint_validations.map { |fk| visit_ValidateConstraint fk }.join(" ")
+          end
+
+          def visit_AddForeignKey(o)
+            super.dup.tap { |sql| sql << " NOT VALID" unless o.validate? }
+          end
+
+          def visit_ValidateConstraint(name)
+            "VALIDATE CONSTRAINT #{quote_column_name(name)}"
+          end
+
           def add_column_options!(sql, options)
             if options[:collation]
               sql << " COLLATE \"#{options[:collation]}\""
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
index f1489e4d69..6047217fcd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
@@ -44,15 +44,8 @@ module ActiveRecord
         # a record (as primary keys cannot be +nil+). This might be done via the
         # +SecureRandom.uuid+ method and a +before_save+ callback, for instance.
         def primary_key(name, type = :primary_key, **options)
-          options[:auto_increment] = true if [:integer, :bigint].include?(type) && !options.key?(:default)
           if type == :uuid
             options[:default] = options.fetch(:default, "gen_random_uuid()")
-          elsif options.delete(:auto_increment) == true && %i(integer bigint).include?(type)
-            type = if type == :bigint || options[:limit] == 8
-              :bigserial
-            else
-              :serial
-            end
           end
 
           super
@@ -102,10 +95,6 @@ module ActiveRecord
           args.each { |name| column(name, :int8range, options) }
         end
 
-        def json(*args, **options)
-          args.each { |name| column(name, :json, options) }
-        end
-
         def jsonb(*args, **options)
           args.each { |name| column(name, :jsonb, options) }
         end
@@ -185,11 +174,33 @@ module ActiveRecord
 
       class TableDefinition < ActiveRecord::ConnectionAdapters::TableDefinition
         include ColumnMethods
+
+        private
+          def integer_like_primary_key_type(type, options)
+            if type == :bigint || options[:limit] == 8
+              :bigserial
+            else
+              :serial
+            end
+          end
       end
 
       class Table < ActiveRecord::ConnectionAdapters::Table
         include ColumnMethods
       end
+
+      class AlterTable < ActiveRecord::ConnectionAdapters::AlterTable
+        attr_reader :constraint_validations
+
+        def initialize(td)
+          super
+          @constraint_validations = []
+        end
+
+        def validate_constraint(name)
+          @constraint_validations << name
+        end
+      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
index c0dbb166b7..84643d20da 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
@@ -5,6 +5,18 @@ module ActiveRecord
     module PostgreSQL
       class SchemaDumper < ConnectionAdapters::SchemaDumper # :nodoc:
         private
+
+          def extensions(stream)
+            extensions = @connection.extensions
+            if extensions.any?
+              stream.puts "  # These are extensions that must be enabled in order to support this database"
+              extensions.sort.each do |extension|
+                stream.puts "  enable_extension #{extension.inspect}"
+              end
+              stream.puts
+            end
+          end
+
           def prepare_column_options(column)
             spec = super
             spec[:array] = "true" if column.array?
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 9e2f61e6ce..bf5fbb30e1 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/string/strip"
-
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
@@ -66,12 +64,7 @@ module ActiveRecord
         end
 
         # Verifies existence of an index with a given name.
-        def index_name_exists?(table_name, index_name, default = nil)
-          unless default.nil?
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing default to #index_name_exists? is deprecated without replacement.
-            MSG
-          end
+        def index_name_exists?(table_name, index_name)
           table = quoted_scope(table_name)
           index = quoted_scope(index_name)
 
@@ -89,21 +82,12 @@ module ActiveRecord
         end
 
         # Returns an array of indexes for the given table.
-        def indexes(table_name, name = nil) # :nodoc:
-          if name
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing name to #indexes is deprecated without replacement.
-            MSG
-          end
-
+        def indexes(table_name) # :nodoc:
           scope = quoted_scope(table_name)
 
           result = query(<<-SQL, "SCHEMA")
             SELECT distinct i.relname, d.indisunique, d.indkey, pg_get_indexdef(d.indexrelid), t.oid,
-                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment,
-            (SELECT COUNT(*) FROM pg_opclass o
-               JOIN (SELECT unnest(string_to_array(d.indclass::text, ' '))::int oid) c
-                 ON o.oid = c.oid WHERE o.opcdefault = 'f')
+                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment
             FROM pg_class t
             INNER JOIN pg_index d ON t.oid = d.indrelid
             INNER JOIN pg_class i ON d.indexrelid = i.oid
@@ -122,11 +106,13 @@ module ActiveRecord
             inddef = row[3]
             oid = row[4]
             comment = row[5]
-            opclass = row[6]
 
             using, expressions, where = inddef.scan(/ USING (\w+?) \((.+?)\)(?: WHERE (.+))?\z/).flatten
 
-            if indkey.include?(0) || opclass > 0
+            orders = {}
+            opclasses = {}
+
+            if indkey.include?(0)
               columns = expressions
             else
               columns = Hash[query(<<-SQL.strip_heredoc, "SCHEMA")].values_at(*indkey).compact
@@ -136,10 +122,12 @@ module ActiveRecord
                 AND a.attnum IN (#{indkey.join(",")})
               SQL
 
-              # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
-              orders = Hash[
-                expressions.scan(/(\w+) DESC/).flatten.map { |order_column| [order_column, :desc] }
-              ]
+              # add info on sort order (only desc order is explicitly specified, asc is the default)
+              # and non-default opclasses
+              expressions.scan(/(\w+)(?: (?!DESC)(\w+))?(?: (DESC))?/).each do |column, opclass, desc|
+                opclasses[column] = opclass.to_sym if opclass
+                orders[column] = :desc if desc
+              end
             end
 
             IndexDefinition.new(
@@ -148,6 +136,7 @@ module ActiveRecord
               unique,
               columns,
               orders: orders,
+              opclasses: opclasses,
               where: where,
               using: using.to_sym,
               comment: comment.presence
@@ -405,50 +394,23 @@ module ActiveRecord
 
         def change_column(table_name, column_name, type, options = {}) #:nodoc:
           clear_cache!
-          quoted_table_name = quote_table_name(table_name)
-          quoted_column_name = quote_column_name(column_name)
-          sql_type = type_to_sql(type, options)
-          sql = "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}".dup
-          if options[:collation]
-            sql << " COLLATE \"#{options[:collation]}\""
-          end
-          if options[:using]
-            sql << " USING #{options[:using]}"
-          elsif options[:cast_as]
-            cast_as_type = type_to_sql(options[:cast_as], options)
-            sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
-          end
-          execute sql
-
-          change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
-          change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
-          change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
+          sqls, procs = change_column_for_alter(table_name, column_name, type, options)
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{sqls.join(", ")}"
+          procs.each(&:call)
         end
 
         # Changes the default value of a table column.
         def change_column_default(table_name, column_name, default_or_changes) # :nodoc:
-          clear_cache!
-          column = column_for(table_name, column_name)
-          return unless column
-
-          default = extract_new_default_value(default_or_changes)
-          alter_column_query = "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} %s"
-          if default.nil?
-            # <tt>DEFAULT NULL</tt> results in the same behavior as <tt>DROP DEFAULT</tt>. However, PostgreSQL will
-            # cast the default to the columns type, which leaves us with a default like "default NULL::character varying".
-            execute alter_column_query % "DROP DEFAULT"
-          else
-            execute alter_column_query % "SET DEFAULT #{quote_default_expression(default, column)}"
-          end
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{change_column_default_for_alter(table_name, column_name, default_or_changes)}"
         end
 
         def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
           clear_cache!
           unless null || default.nil?
             column = column_for(table_name, column_name)
-            execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote_default_expression(default, column)} WHERE #{quote_column_name(column_name)} IS NULL") if column
+            execute "UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote_default_expression(default, column)} WHERE #{quote_column_name(column_name)} IS NULL" if column
           end
-          execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{change_column_null_for_alter(table_name, column_name, null, default)}"
         end
 
         # Adds comment for given table column or drops it if +comment+ is a +nil+
@@ -471,8 +433,8 @@ module ActiveRecord
         end
 
         def add_index(table_name, column_name, options = {}) #:nodoc:
-          index_name, index_type, index_columns, index_options, index_algorithm, index_using, comment = add_index_options(table_name, column_name, options)
-          execute("CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns})#{index_options}").tap do
+          index_name, index_type, index_columns_and_opclasses, index_options, index_algorithm, index_using, comment = add_index_options(table_name, column_name, options)
+          execute("CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns_and_opclasses})#{index_options}").tap do
             execute "COMMENT ON INDEX #{quote_column_name(index_name)} IS #{quote(comment)}" if comment
           end
         end
@@ -512,7 +474,7 @@ module ActiveRecord
         def foreign_keys(table_name)
           scope = quoted_scope(table_name)
           fk_info = exec_query(<<-SQL.strip_heredoc, "SCHEMA")
-            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete
+            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete, c.convalidated AS valid
             FROM pg_constraint c
             JOIN pg_class t1 ON c.conrelid = t1.oid
             JOIN pg_class t2 ON c.confrelid = t2.oid
@@ -534,6 +496,7 @@ module ActiveRecord
 
             options[:on_delete] = extract_foreign_key_action(row["on_delete"])
             options[:on_update] = extract_foreign_key_action(row["on_update"])
+            options[:validate] = row["valid"]
 
             ForeignKeyDefinition.new(table_name, row["to_table"], options)
           end
@@ -594,6 +557,43 @@ module ActiveRecord
           PostgreSQL::SchemaDumper.create(self, options)
         end
 
+        # Validates the given constraint.
+        #
+        # Validates the constraint named +constraint_name+ on +accounts+.
+        #
+        #   validate_constraint :accounts, :constraint_name
+        def validate_constraint(table_name, constraint_name)
+          return unless supports_validate_constraints?
+
+          at = create_alter_table table_name
+          at.validate_constraint constraint_name
+
+          execute schema_creation.accept(at)
+        end
+
+        # Validates the given foreign key.
+        #
+        # Validates the foreign key on +accounts.branch_id+.
+        #
+        #   validate_foreign_key :accounts, :branches
+        #
+        # Validates the foreign key on +accounts.owner_id+.
+        #
+        #   validate_foreign_key :accounts, column: :owner_id
+        #
+        # Validates the foreign key named +special_fk_name+ on the +accounts+ table.
+        #
+        #   validate_foreign_key :accounts, name: :special_fk_name
+        #
+        # The +options+ hash accepts the same keys as SchemaStatements#add_foreign_key.
+        def validate_foreign_key(from_table, options_or_to_table = {})
+          return unless supports_validate_constraints?
+
+          fk_name_to_validate = foreign_key_for!(from_table, options_or_to_table).name
+
+          validate_constraint from_table, fk_name_to_validate
+        end
+
         private
           def schema_creation
             PostgreSQL::SchemaCreation.new(self)
@@ -603,6 +603,10 @@ module ActiveRecord
             PostgreSQL::TableDefinition.new(*args)
           end
 
+          def create_alter_table(name)
+            PostgreSQL::AlterTable.new create_table_definition(name)
+          end
+
           def new_column_from_field(table_name, field)
             column_name, type, default, notnull, oid, fmod, collation, comment = field
             type_metadata = fetch_type_metadata(column_name, type, oid.to_i, fmod.to_i)
@@ -617,7 +621,8 @@ module ActiveRecord
               table_name,
               default_function,
               collation,
-              comment: comment.presence
+              comment: comment.presence,
+              max_identifier_length: max_identifier_length
             )
           end
 
@@ -641,6 +646,66 @@ module ActiveRecord
             end
           end
 
+          def change_column_sql(table_name, column_name, type, options = {})
+            quoted_column_name = quote_column_name(column_name)
+            sql_type = type_to_sql(type, options)
+            sql = "ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}".dup
+            if options[:collation]
+              sql << " COLLATE \"#{options[:collation]}\""
+            end
+            if options[:using]
+              sql << " USING #{options[:using]}"
+            elsif options[:cast_as]
+              cast_as_type = type_to_sql(options[:cast_as], options)
+              sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
+            end
+
+            sql
+          end
+
+          def change_column_for_alter(table_name, column_name, type, options = {})
+            sqls = [change_column_sql(table_name, column_name, type, options)]
+            procs = []
+            sqls << change_column_default_for_alter(table_name, column_name, options[:default]) if options.key?(:default)
+            sqls << change_column_null_for_alter(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+            procs << Proc.new { change_column_comment(table_name, column_name, options[:comment]) } if options.key?(:comment)
+
+            [sqls, procs]
+          end
+
+
+          # Changes the default value of a table column.
+          def change_column_default_for_alter(table_name, column_name, default_or_changes) # :nodoc:
+            column = column_for(table_name, column_name)
+            return unless column
+
+            default = extract_new_default_value(default_or_changes)
+            alter_column_query = "ALTER COLUMN #{quote_column_name(column_name)} %s"
+            if default.nil?
+              # <tt>DEFAULT NULL</tt> results in the same behavior as <tt>DROP DEFAULT</tt>. However, PostgreSQL will
+              # cast the default to the columns type, which leaves us with a default like "default NULL::character varying".
+              alter_column_query % "DROP DEFAULT"
+            else
+              alter_column_query % "SET DEFAULT #{quote_default_expression(default, column)}"
+            end
+          end
+
+          def change_column_null_for_alter(table_name, column_name, null, default = nil) #:nodoc:
+            "ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL"
+          end
+
+          def add_index_opclass(quoted_columns, **options)
+            opclasses = options_for_index_columns(options[:opclass])
+            quoted_columns.each do |name, column|
+              column << " #{opclasses[name]}" if opclasses[name].present?
+            end
+          end
+
+          def add_options_for_index_columns(quoted_columns, **options)
+            quoted_columns = add_index_opclass(quoted_columns, options)
+            super
+          end
+
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
             scope[:type] ||= "'r','v','m'" # (r)elation/table, (v)iew, (m)aterialized view
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 4d37a292d6..23fc69d649 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -4,20 +4,20 @@
 gem "pg", "~> 0.18"
 require "pg"
 
-require_relative "abstract_adapter"
-require_relative "statement_pool"
-require_relative "postgresql/column"
-require_relative "postgresql/database_statements"
-require_relative "postgresql/explain_pretty_printer"
-require_relative "postgresql/oid"
-require_relative "postgresql/quoting"
-require_relative "postgresql/referential_integrity"
-require_relative "postgresql/schema_creation"
-require_relative "postgresql/schema_definitions"
-require_relative "postgresql/schema_dumper"
-require_relative "postgresql/schema_statements"
-require_relative "postgresql/type_metadata"
-require_relative "postgresql/utils"
+require "active_record/connection_adapters/abstract_adapter"
+require "active_record/connection_adapters/statement_pool"
+require "active_record/connection_adapters/postgresql/column"
+require "active_record/connection_adapters/postgresql/database_statements"
+require "active_record/connection_adapters/postgresql/explain_pretty_printer"
+require "active_record/connection_adapters/postgresql/oid"
+require "active_record/connection_adapters/postgresql/quoting"
+require "active_record/connection_adapters/postgresql/referential_integrity"
+require "active_record/connection_adapters/postgresql/schema_creation"
+require "active_record/connection_adapters/postgresql/schema_definitions"
+require "active_record/connection_adapters/postgresql/schema_dumper"
+require "active_record/connection_adapters/postgresql/schema_statements"
+require "active_record/connection_adapters/postgresql/type_metadata"
+require "active_record/connection_adapters/postgresql/utils"
 
 module ActiveRecord
   module ConnectionHandling # :nodoc:
@@ -142,6 +142,10 @@ module ActiveRecord
         true
       end
 
+      def supports_validate_constraints?
+        true
+      end
+
       def supports_views?
         true
       end
@@ -166,7 +170,7 @@ module ActiveRecord
         { concurrently: "CONCURRENTLY" }
       end
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         def initialize(connection, max)
           super(max)
           @connection = connection
@@ -182,7 +186,6 @@ module ActiveRecord
         end
 
         private
-
           def dealloc(key)
             @connection.query "DEALLOCATE #{key}" if connection_active?
           rescue PG::Error
@@ -273,6 +276,11 @@ module ActiveRecord
         end
       end
 
+      def discard! # :nodoc:
+        @connection.socket_io.reopen(IO::NULL)
+        @connection = nil
+      end
+
       def native_database_types #:nodoc:
         NATIVE_DATABASE_TYPES
       end
@@ -312,14 +320,14 @@ module ActiveRecord
 
       def get_advisory_lock(lock_id) # :nodoc:
         unless lock_id.is_a?(Integer) && lock_id.bit_length <= 63
-          raise(ArgumentError, "Postgres requires advisory lock ids to be a signed 64 bit integer")
+          raise(ArgumentError, "PostgreSQL requires advisory lock ids to be a signed 64 bit integer")
         end
         query_value("SELECT pg_try_advisory_lock(#{lock_id})")
       end
 
       def release_advisory_lock(lock_id) # :nodoc:
         unless lock_id.is_a?(Integer) && lock_id.bit_length <= 63
-          raise(ArgumentError, "Postgres requires advisory lock ids to be a signed 64 bit integer")
+          raise(ArgumentError, "PostgreSQL requires advisory lock ids to be a signed 64 bit integer")
         end
         query_value("SELECT pg_advisory_unlock(#{lock_id})")
       end
@@ -337,25 +345,20 @@ module ActiveRecord
       end
 
       def extension_enabled?(name)
-        if supports_extensions?
-          res = exec_query("SELECT EXISTS(SELECT * FROM pg_available_extensions WHERE name = '#{name}' AND installed_version IS NOT NULL) as enabled", "SCHEMA")
-          res.cast_values.first
-        end
+        res = exec_query("SELECT EXISTS(SELECT * FROM pg_available_extensions WHERE name = '#{name}' AND installed_version IS NOT NULL) as enabled", "SCHEMA")
+        res.cast_values.first
       end
 
       def extensions
-        if supports_extensions?
-          exec_query("SELECT extname FROM pg_extension", "SCHEMA").cast_values
-        else
-          super
-        end
+        exec_query("SELECT extname FROM pg_extension", "SCHEMA").cast_values
       end
 
       # Returns the configured supported identifier length supported by PostgreSQL
-      def table_alias_length
+      def max_identifier_length
         @max_identifier_length ||= query_value("SHOW max_identifier_length", "SCHEMA").to_i
       end
-      alias index_name_length table_alias_length
+      alias table_alias_length max_identifier_length
+      alias index_name_length max_identifier_length
 
       # Set the authorized user for this session
       def session_auth=(user)
@@ -387,7 +390,6 @@ module ActiveRecord
       end
 
       private
-
         # See https://www.postgresql.org/docs/current/static/errcodes-appendix.html
         VALUE_LIMIT_VIOLATION = "22001"
         NUMERIC_VALUE_OUT_OF_RANGE = "22003"
@@ -396,6 +398,8 @@ module ActiveRecord
         UNIQUE_VIOLATION      = "23505"
         SERIALIZATION_FAILURE = "40001"
         DEADLOCK_DETECTED     = "40P01"
+        LOCK_NOT_AVAILABLE    = "55P03"
+        QUERY_CANCELED        = "57014"
 
         def translate_exception(exception, message)
           return exception unless exception.respond_to?(:result)
@@ -415,6 +419,10 @@ module ActiveRecord
             SerializationFailure.new(message)
           when DEADLOCK_DETECTED
             Deadlocked.new(message)
+          when LOCK_NOT_AVAILABLE
+            LockWaitTimeout.new(message)
+          when QUERY_CANCELED
+            QueryCanceled.new(message)
           else
             super
           end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
index 501f17dbad..c9855019c1 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
@@ -3,27 +3,16 @@
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
-      module ColumnMethods
-        def primary_key(name, type = :primary_key, **options)
-          if %i(integer bigint).include?(type) && (options.delete(:auto_increment) == true || !options.key?(:default))
-            type = :primary_key
-          end
-
-          super
-        end
-      end
-
       class TableDefinition < ActiveRecord::ConnectionAdapters::TableDefinition
-        include ColumnMethods
-
         def references(*args, **options)
           super(*args, type: :integer, **options)
         end
         alias :belongs_to :references
-      end
 
-      class Table < ActiveRecord::ConnectionAdapters::Table
-        include ColumnMethods
+        private
+          def integer_like_primary_key_type(type, options)
+            :primary_key
+          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
index a512702b7b..58e5138e02 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
@@ -5,13 +5,7 @@ module ActiveRecord
     module SQLite3
       module SchemaStatements # :nodoc:
         # Returns an array of indexes for the given table.
-        def indexes(table_name, name = nil)
-          if name
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing name to #indexes is deprecated without replacement.
-            MSG
-          end
-
+        def indexes(table_name)
           exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").map do |row|
             index_sql = query_value(<<-SQL, "SCHEMA")
               SELECT sql
@@ -29,20 +23,26 @@ module ActiveRecord
               col["name"]
             end
 
+            # Add info on sort order for columns (only desc order is explicitly specified, asc is
+            # the default)
+            orders = {}
+            if index_sql # index_sql can be null in case of primary key indexes
+              index_sql.scan(/"(\w+)" DESC/).flatten.each { |order_column|
+                orders[order_column] = :desc
+              }
+            end
+
             IndexDefinition.new(
               table_name,
               row["name"],
               row["unique"] != 0,
               columns,
-              where: where
+              where: where,
+              orders: orders
             )
           end
         end
 
-        def update_table_definition(table_name, base)
-          SQLite3::Table.new(table_name, base)
-        end
-
         def create_schema_dumper(options)
           SQLite3::SchemaDumper.create(self, options)
         end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 6fdd666486..c72db15ce3 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "abstract_adapter"
-require_relative "statement_pool"
-require_relative "sqlite3/explain_pretty_printer"
-require_relative "sqlite3/quoting"
-require_relative "sqlite3/schema_creation"
-require_relative "sqlite3/schema_definitions"
-require_relative "sqlite3/schema_dumper"
-require_relative "sqlite3/schema_statements"
+require "active_record/connection_adapters/abstract_adapter"
+require "active_record/connection_adapters/statement_pool"
+require "active_record/connection_adapters/sqlite3/explain_pretty_printer"
+require "active_record/connection_adapters/sqlite3/quoting"
+require "active_record/connection_adapters/sqlite3/schema_creation"
+require "active_record/connection_adapters/sqlite3/schema_definitions"
+require "active_record/connection_adapters/sqlite3/schema_dumper"
+require "active_record/connection_adapters/sqlite3/schema_statements"
 
 gem "sqlite3", "~> 1.3.6"
 require "sqlite3"
@@ -70,7 +70,8 @@ module ActiveRecord
         time:         { name: "time" },
         date:         { name: "date" },
         binary:       { name: "blob" },
-        boolean:      { name: "boolean" }
+        boolean:      { name: "boolean" },
+        json:         { name: "json" },
       }
 
       ##
@@ -90,9 +91,8 @@ module ActiveRecord
       #   Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
       class_attribute :represent_boolean_as_integer, default: false
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         private
-
           def dealloc(stmt)
             stmt[:stmt].close unless stmt[:stmt].closed?
           end
@@ -135,6 +135,10 @@ module ActiveRecord
         true
       end
 
+      def supports_json?
+        true
+      end
+
       def supports_multi_insert?
         sqlite_version >= "3.7.11"
       end
@@ -370,6 +374,10 @@ module ActiveRecord
       end
 
       private
+        def initialize_type_map(m = type_map)
+          super
+          register_class_with_limit m, %r(int)i, SQLite3Integer
+        end
 
         def table_structure(table_name)
           structure = exec_query("PRAGMA table_info(#{quote_table_name(table_name)})", "SCHEMA")
@@ -399,18 +407,21 @@ module ActiveRecord
           options[:id] = false
           create_table(to, options) do |definition|
             @definition = definition
-            @definition.primary_key(from_primary_key) if from_primary_key.present?
+            if from_primary_key.is_a?(Array)
+              @definition.primary_keys from_primary_key
+            end
             columns(from).each do |column|
               column_name = options[:rename] ?
                 (options[:rename][column.name] ||
                  options[:rename][column.name.to_sym] ||
                  column.name) : column.name
-              next if column_name == from_primary_key
 
               @definition.column(column_name, column.type,
                 limit: column.limit, default: column.default,
                 precision: column.precision, scale: column.scale,
-                null: column.null, collation: column.collation)
+                null: column.null, collation: column.collation,
+                primary_key: column_name == from_primary_key
+              )
             end
             yield @definition if block_given?
           end
@@ -423,6 +434,9 @@ module ActiveRecord
         def copy_table_indexes(from, to, rename = {})
           indexes(from).each do |index|
             name = index.name
+            # indexes sqlite creates for internal use start with `sqlite_` and
+            # don't need to be copied
+            next if name.starts_with?("sqlite_")
             if to == "a#{from}"
               name = "t#{name}"
             elsif from == "a#{to}"
@@ -525,6 +539,17 @@ module ActiveRecord
         def configure_connection
           execute("PRAGMA foreign_keys = ON", "SCHEMA")
         end
+
+        class SQLite3Integer < Type::Integer # :nodoc:
+          private
+            def _limit
+              # INTEGER storage class can be stored 8 bytes value.
+              # See https://www.sqlite.org/datatype3.html#storage_classes_and_datatypes
+              limit || 8
+            end
+        end
+
+        ActiveRecord::Type.register(:integer, SQLite3Integer, adapter: :sqlite3)
     end
     ActiveSupport.run_load_hooks(:active_record_sqlite3adapter, SQLite3Adapter)
   end
diff --git a/activerecord/lib/active_record/connection_handling.rb b/activerecord/lib/active_record/connection_handling.rb
index 9a47edfba4..88d28dc52a 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -140,6 +140,6 @@ module ActiveRecord
     end
 
     delegate :clear_active_connections!, :clear_reloadable_connections!,
-      :clear_all_connections!, to: :connection_handler
+      :clear_all_connections!, :flush_idle_connections!, to: :connection_handler
   end
 end
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 945c4eca78..481159e501 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -76,25 +76,13 @@ module ActiveRecord
       # scope being ignored is error-worthy, rather than a warning.
       mattr_accessor :error_on_ignored_order, instance_writer: false, default: false
 
-      def self.error_on_ignored_order_or_limit
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
-          The flag error_on_ignored_order_or_limit is deprecated. Limits are
-          now supported. Please use error_on_ignored_order instead.
-        MSG
-        error_on_ignored_order
-      end
-
-      def error_on_ignored_order_or_limit
-        self.class.error_on_ignored_order_or_limit
-      end
-
-      def self.error_on_ignored_order_or_limit=(value)
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
-          The flag error_on_ignored_order_or_limit is deprecated. Limits are
-          now supported. Please use error_on_ignored_order= instead.
-        MSG
-        self.error_on_ignored_order = value
-      end
+      # :singleton-method:
+      # Specify the behavior for unsafe raw query methods. Values are as follows
+      #   deprecated - Warnings are logged when unsafe raw SQL is passed to
+      #                query methods.
+      #   disabled   - Unsafe raw SQL passed to query methods results in
+      #                UnknownAttributeReference exception.
+      mattr_accessor :allow_unsafe_raw_sql, instance_writer: false, default: :deprecated
 
       ##
       # :singleton-method:
@@ -289,7 +277,8 @@ module ActiveRecord
           relation = Relation.create(self, arel_table, predicate_builder)
 
           if finder_needs_type_condition? && !ignore_default_scope?
-            relation.where(type_condition).create_with(inheritance_column.to_s => sti_name)
+            relation.where!(type_condition)
+            relation.create_with!(inheritance_column.to_s => sti_name)
           else
             relation
           end
diff --git a/activerecord/lib/active_record/counter_cache.rb b/activerecord/lib/active_record/counter_cache.rb
index 5005d58f1c..ee4f818cbf 100644
--- a/activerecord/lib/active_record/counter_cache.rb
+++ b/activerecord/lib/active_record/counter_cache.rb
@@ -53,7 +53,7 @@ module ActiveRecord
           unscoped.where(primary_key => object.id).update_all(updates)
         end
 
-        return true
+        true
       end
 
       # A generic "counter updater" implementation, intended primarily to be
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index f373b98035..1a3e6e4d09 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -221,6 +221,8 @@ module ActiveRecord
       def detect_enum_conflict!(enum_name, method_name, klass_method = false)
         if klass_method && dangerous_class_method?(method_name)
           raise_conflict_error(enum_name, method_name, type: "class")
+        elsif klass_method && method_defined_within?(method_name, Relation)
+          raise_conflict_error(enum_name, method_name, type: "class", source: Relation.name)
         elsif !klass_method && dangerous_attribute_method?(method_name)
           raise_conflict_error(enum_name, method_name)
         elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module)
diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index 9ef3316393..efcbd44776 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -335,8 +335,40 @@ module ActiveRecord
   class IrreversibleOrderError < ActiveRecordError
   end
 
-  # TransactionTimeout will be raised when lock wait timeout expires.
-  # Wait time value is set by innodb_lock_wait_timeout.
-  class TransactionTimeout < StatementInvalid
+  # LockWaitTimeout will be raised when lock wait timeout exceeded.
+  class LockWaitTimeout < StatementInvalid
+  end
+
+  # StatementTimeout will be raised when statement timeout exceeded.
+  class StatementTimeout < StatementInvalid
+  end
+
+  # QueryCanceled will be raised when canceling statement due to user request.
+  class QueryCanceled < StatementInvalid
+  end
+
+  # UnknownAttributeReference is raised when an unknown and potentially unsafe
+  # value is passed to a query method when allow_unsafe_raw_sql is set to
+  # :disabled. For example, passing a non column name value to a relation's
+  # #order method might cause this exception.
+  #
+  # When working around this exception, caution should be taken to avoid SQL
+  # injection vulnerabilities when passing user-provided values to query
+  # methods. Known-safe values can be passed to query methods by wrapping them
+  # in Arel.sql.
+  #
+  # For example, with allow_unsafe_raw_sql set to :disabled, the following
+  # code would raise this exception:
+  #
+  #   Post.order("length(title)").first
+  #
+  # The desired result can be accomplished by wrapping the known-safe string
+  # in Arel.sql:
+  #
+  #   Post.order(Arel.sql("length(title)")).first
+  #
+  # Again, such a workaround should *not* be used when passing user-provided
+  # values, such as request parameters or model attributes to query methods.
+  class UnknownAttributeReference < ActiveRecordError
   end
 end
diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb
index 8bb54a24b7..7ccb938888 100644
--- a/activerecord/lib/active_record/explain.rb
+++ b/activerecord/lib/active_record/explain.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "explain_registry"
+require "active_record/explain_registry"
 
 module ActiveRecord
   module Explain
diff --git a/activerecord/lib/active_record/explain_subscriber.rb b/activerecord/lib/active_record/explain_subscriber.rb
index 9252fa3fed..a86217abc0 100644
--- a/activerecord/lib/active_record/explain_subscriber.rb
+++ b/activerecord/lib/active_record/explain_subscriber.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/notifications"
-require_relative "explain_registry"
+require "active_record/explain_registry"
 
 module ActiveRecord
   class ExplainSubscriber # :nodoc:
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index 12169fffa9..86f13d75d5 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -6,8 +6,8 @@ require "zlib"
 require "set"
 require "active_support/dependencies"
 require "active_support/core_ext/digest/uuid"
-require_relative "fixture_set/file"
-require_relative "errors"
+require "active_record/fixture_set/file"
+require "active_record/errors"
 
 module ActiveRecord
   class FixtureClassNotFound < ActiveRecord::ActiveRecordError #:nodoc:
diff --git a/activerecord/lib/active_record/gem_version.rb b/activerecord/lib/active_record/gem_version.rb
index 7ccb57b305..7e47dac016 100644
--- a/activerecord/lib/active_record/gem_version.rb
+++ b/activerecord/lib/active_record/gem_version.rb
@@ -10,7 +10,7 @@ module ActiveRecord
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activerecord/lib/active_record/internal_metadata.rb b/activerecord/lib/active_record/internal_metadata.rb
index 14795cc815..5a65edf27e 100644
--- a/activerecord/lib/active_record/internal_metadata.rb
+++ b/activerecord/lib/active_record/internal_metadata.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "scoping/default"
-require_relative "scoping/named"
+require "active_record/scoping/default"
+require "active_record/scoping/named"
 
 module ActiveRecord
   # This class is used to create a table that keeps track of values and keys such
diff --git a/activerecord/lib/active_record/legacy_yaml_adapter.rb b/activerecord/lib/active_record/legacy_yaml_adapter.rb
index 23644aab8f..ffa095dd94 100644
--- a/activerecord/lib/active_record/legacy_yaml_adapter.rb
+++ b/activerecord/lib/active_record/legacy_yaml_adapter.rb
@@ -8,7 +8,7 @@ module ActiveRecord
       case coder["active_record_yaml_version"]
       when 1, 2 then coder
       else
-        if coder["attributes"].is_a?(AttributeSet)
+        if coder["attributes"].is_a?(ActiveModel::AttributeSet)
           Rails420.convert(klass, coder)
         else
           Rails41.convert(klass, coder)
diff --git a/activerecord/lib/active_record/locking/pessimistic.rb b/activerecord/lib/active_record/locking/pessimistic.rb
index 72bccd4906..bb85c47e06 100644
--- a/activerecord/lib/active_record/locking/pessimistic.rb
+++ b/activerecord/lib/active_record/locking/pessimistic.rb
@@ -63,12 +63,13 @@ module ActiveRecord
       def lock!(lock = true)
         if persisted?
           if changed?
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Locking a record with unpersisted changes is deprecated and will raise an
-              exception in Rails 5.2. Use `save` to persist the changes, or `reload` to
-              discard them explicitly.
+            raise(<<-MSG.squish)
+              Locking a record with unpersisted changes is not supported. Use
+              `save` to persist the changes, or `reload` to discard them
+              explicitly.
             MSG
           end
+
           reload(lock: lock)
         end
         self
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 52ca4671c2..5c10d4ff24 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -354,9 +354,9 @@ module ActiveRecord
   # to match the structure of your database.
   #
   # To roll the database back to a previous migration version, use
-  # <tt>rails db:migrate VERSION=X</tt> where <tt>X</tt> is the version to which
+  # <tt>rails db:rollback VERSION=X</tt> where <tt>X</tt> is the version to which
   # you wish to downgrade. Alternatively, you can also use the STEP option if you
-  # wish to rollback last few migrations. <tt>rails db:migrate STEP=2</tt> will rollback
+  # wish to rollback last few migrations. <tt>rails db:rollback STEP=2</tt> will rollback
   # the latest two migrations.
   #
   # If any of the migrations throw an <tt>ActiveRecord::IrreversibleMigration</tt> exception,
@@ -581,7 +581,8 @@ module ActiveRecord
       def load_schema_if_pending!
         if ActiveRecord::Migrator.needs_migration? || !ActiveRecord::Migrator.any_migrations?
           # Roundtrip to Rake to allow plugins to hook into database initialization.
-          FileUtils.cd Rails.root do
+          root = defined?(ENGINE_ROOT) ? ENGINE_ROOT : Rails.root
+          FileUtils.cd(root) do
             current_config = Base.connection_config
             Base.clear_all_connections!
             system("bin/rails db:test:prepare")
@@ -733,6 +734,24 @@ module ActiveRecord
       execute_block { yield helper }
     end
 
+    # Used to specify an operation that is only run when migrating up
+    # (for example, populating a new column with its initial values).
+    #
+    # In the following example, the new column +published+ will be given
+    # the value +true+ for all existing records.
+    #
+    #    class AddPublishedToPosts < ActiveRecord::Migration[5.2]
+    #      def change
+    #        add_column :posts, :published, :boolean, default: false
+    #        up_only do
+    #          execute "update posts set published = 'true'"
+    #        end
+    #      end
+    #    end
+    def up_only
+      execute_block { yield } unless reverting?
+    end
+
     # Runs the given migration classes.
     # Last argument can specify options:
     # - :direction (default is :up)
@@ -1026,12 +1045,7 @@ module ActiveRecord
         new(:up, migrations(migrations_paths), nil)
       end
 
-      def schema_migrations_table_name
-        SchemaMigration.table_name
-      end
-      deprecate :schema_migrations_table_name
-
-      def get_all_versions(connection = Base.connection)
+      def get_all_versions
         if SchemaMigration.table_exists?
           SchemaMigration.all_versions.map(&:to_i)
         else
@@ -1039,12 +1053,13 @@ module ActiveRecord
         end
       end
 
-      def current_version(connection = Base.connection)
-        get_all_versions(connection).max || 0
+      def current_version(connection = nil)
+        get_all_versions.max || 0
+      rescue ActiveRecord::NoDatabaseError
       end
 
-      def needs_migration?(connection = Base.connection)
-        (migrations(migrations_paths).collect(&:version) - get_all_versions(connection)).size > 0
+      def needs_migration?(connection = nil)
+        (migrations(migrations_paths).collect(&:version) - get_all_versions).size > 0
       end
 
       def any_migrations?
@@ -1229,7 +1244,7 @@ module ActiveRecord
 
       # Return true if a valid version is not provided.
       def invalid_target?
-        !target && @target_version && @target_version > 0
+        @target_version && @target_version != 0 && !target
       end
 
       def execute_migration_in_transaction(migration, direction)
diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index a3a5e0fa16..81ef4828f8 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -110,7 +110,7 @@ module ActiveRecord
 
       private
 
-        module StraightReversions
+        module StraightReversions # :nodoc:
           private
             { transaction:       :transaction,
               execute_block:     :execute_block,
@@ -161,8 +161,8 @@ module ActiveRecord
           table, columns, options = *args
           options ||= {}
 
-          index_name = options[:name]
-          options_hash = index_name ? { name: index_name } : { column: columns }
+          options_hash = options.slice(:name, :algorithm)
+          options_hash[:column] = columns if !options_hash[:name]
 
           [:remove_index, [table, options_hash]]
         end
diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 784292f3f9..bd8c054c28 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -16,10 +16,27 @@ module ActiveRecord
       V5_2 = Current
 
       class V5_1 < V5_2
+        def change_column(table_name, column_name, type, options = {})
+          if adapter_name == "PostgreSQL"
+            clear_cache!
+            sql = connection.send(:change_column_sql, table_name, column_name, type, options)
+            execute "ALTER TABLE #{quote_table_name(table_name)} #{sql}"
+            change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
+            change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+            change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
+          else
+            super
+          end
+        end
       end
 
       class V5_0 < V5_1
         module TableDefinition
+          def primary_key(name, type = :primary_key, **options)
+            type = :integer if type == :primary_key
+            super
+          end
+
           def references(*args, **options)
             super(*args, type: :integer, **options)
           end
@@ -47,11 +64,8 @@ module ActiveRecord
           end
 
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
@@ -60,21 +74,46 @@ module ActiveRecord
 
         def change_table(table_name, options = {})
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
           end
         end
 
+        def create_join_table(table_1, table_2, column_options: {}, **options)
+          column_options.reverse_merge!(type: :integer)
+
+          if block_given?
+            super do |t|
+              yield compatible_table_definition(t)
+            end
+          else
+            super
+          end
+        end
+
+        def add_column(table_name, column_name, type, options = {})
+          if type == :primary_key
+            type = :integer
+            options[:primary_key] = true
+          end
+          super
+        end
+
         def add_reference(table_name, ref_name, **options)
           super(table_name, ref_name, type: :integer, **options)
         end
         alias :add_belongs_to :add_reference
+
+        private
+          def compatible_table_definition(t)
+            class << t
+              prepend TableDefinition
+            end
+            t
+          end
       end
 
       class V4_2 < V5_0
@@ -93,11 +132,8 @@ module ActiveRecord
 
         def create_table(table_name, options = {})
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
@@ -106,11 +142,8 @@ module ActiveRecord
 
         def change_table(table_name, options = {})
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
@@ -146,6 +179,12 @@ module ActiveRecord
         end
 
         private
+          def compatible_table_definition(t)
+            class << t
+              prepend TableDefinition
+            end
+            super
+          end
 
           def index_name_for_remove(table_name, options = {})
             index_name = index_name(table_name, options)
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 34c0ef4e75..1941d3d5ea 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -115,20 +115,6 @@ module ActiveRecord
     # If true, the default table name for a Product class will be "products". If false, it would just be "product".
     # See table_name for the full rules on table/class naming. This is true, by default.
 
-    ##
-    # :singleton-method: ignored_columns
-    # :call-seq: ignored_columns
-    #
-    # The list of columns names the model should ignore. Ignored columns won't have attribute
-    # accessors defined, and won't be referenced in SQL queries.
-
-    ##
-    # :singleton-method: ignored_columns=
-    # :call-seq: ignored_columns=(columns)
-    #
-    # Sets the columns names the model should ignore. Ignored columns won't have attribute
-    # accessors defined, and won't be referenced in SQL queries.
-
     included do
       mattr_accessor :primary_key_prefix_type, instance_writer: false
 
@@ -138,9 +124,9 @@ module ActiveRecord
       class_attribute :internal_metadata_table_name, instance_accessor: false, default: "ar_internal_metadata"
       class_attribute :protected_environments, instance_accessor: false, default: [ "production" ]
       class_attribute :pluralize_table_names, instance_writer: false, default: true
-      class_attribute :ignored_columns, instance_accessor: false, default: [].freeze
 
       self.inheritance_column = "type"
+      self.ignored_columns = [].freeze
 
       delegate :type_for_attribute, to: :class
 
@@ -271,6 +257,22 @@ module ActiveRecord
         @explicit_inheritance_column = true
       end
 
+      # The list of columns names the model should ignore. Ignored columns won't have attribute
+      # accessors defined, and won't be referenced in SQL queries.
+      def ignored_columns
+        if defined?(@ignored_columns)
+          @ignored_columns
+        else
+          superclass.ignored_columns
+        end
+      end
+
+      # Sets the columns names the model should ignore. Ignored columns won't have attribute
+      # accessors defined, and won't be referenced in SQL queries.
+      def ignored_columns=(columns)
+        @ignored_columns = columns.map(&:to_s)
+      end
+
       def sequence_name
         if base_class == self
           @sequence_name ||= reset_sequence_name
@@ -321,11 +323,11 @@ module ActiveRecord
       end
 
       def attributes_builder # :nodoc:
-        @attributes_builder ||= AttributeSet::Builder.new(attribute_types, primary_key) do |name|
-          unless columns_hash.key?(name)
-            _default_attributes[name].dup
-          end
+        unless defined?(@attributes_builder) && @attributes_builder
+          defaults = _default_attributes.except(*(column_names - [primary_key]))
+          @attributes_builder = ActiveModel::AttributeSet::Builder.new(attribute_types, defaults)
         end
+        @attributes_builder
       end
 
       def columns_hash # :nodoc:
@@ -344,7 +346,7 @@ module ActiveRecord
       end
 
       def yaml_encoder # :nodoc:
-        @yaml_encoder ||= AttributeSet::YAMLEncoder.new(attribute_types)
+        @yaml_encoder ||= ActiveModel::AttributeSet::YAMLEncoder.new(attribute_types)
       end
 
       # Returns the type of the attribute with the given name, after applying
@@ -374,7 +376,7 @@ module ActiveRecord
       end
 
       def _default_attributes # :nodoc:
-        @default_attributes ||= AttributeSet.new({})
+        @default_attributes ||= ActiveModel::AttributeSet.new({})
       end
 
       # Returns an array of column names as strings.
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 435c81c153..fa20bce3a9 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -63,6 +63,18 @@ module ActiveRecord
     #   member.update params[:member]
     #   member.avatar.icon # => 'sad'
     #
+    # If you want to update the current avatar without providing the id, you must add <tt>:update_only</tt> option.
+    #
+    #   class Member < ActiveRecord::Base
+    #     has_one :avatar
+    #     accepts_nested_attributes_for :avatar, update_only: true
+    #   end
+    #
+    #   params = { member: { avatar_attributes: { icon: 'sad' } } }
+    #   member.update params[:member]
+    #   member.avatar.id # => 2
+    #   member.avatar.icon # => 'sad'
+    #
     # By default you will only be able to set and update attributes on the
     # associated model. If you want to destroy the associated model through the
     # attributes hash, you have to enable it first using the
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index fbbf9082cc..a13b0d0181 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -71,6 +71,132 @@ module ActiveRecord
         klass.allocate.init_with("attributes" => attributes, "new_record" => false, &block)
       end
 
+      # Updates an object (or multiple objects) and saves it to the database, if validations pass.
+      # The resulting object is returned whether the object was saved successfully to the database or not.
+      #
+      # ==== Parameters
+      #
+      # * +id+ - This should be the id or an array of ids to be updated.
+      # * +attributes+ - This should be a hash of attributes or an array of hashes.
+      #
+      # ==== Examples
+      #
+      #   # Updates one record
+      #   Person.update(15, user_name: "Samuel", group: "expert")
+      #
+      #   # Updates multiple records
+      #   people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
+      #   Person.update(people.keys, people.values)
+      #
+      #   # Updates multiple records from the result of a relation
+      #   people = Person.where(group: "expert")
+      #   people.update(group: "masters")
+      #
+      # Note: Updating a large number of records will run an UPDATE
+      # query for each record, which may cause a performance issue.
+      # When running callbacks is not needed for each record update,
+      # it is preferred to use {update_all}[rdoc-ref:Relation#update_all]
+      # for updating all records in a single query.
+      def update(id = :all, attributes)
+        if id.is_a?(Array)
+          id.map { |one_id| find(one_id) }.each_with_index { |object, idx|
+            object.update(attributes[idx])
+          }
+        elsif id == :all
+          all.each { |record| record.update(attributes) }
+        else
+          if ActiveRecord::Base === id
+            raise ArgumentError,
+              "You are passing an instance of ActiveRecord::Base to `update`. " \
+              "Please pass the id of the object by calling `.id`."
+          end
+          object = find(id)
+          object.update(attributes)
+          object
+        end
+      end
+
+      # Destroy an object (or multiple objects) that has the given id. The object is instantiated first,
+      # therefore all callbacks and filters are fired off before the object is deleted. This method is
+      # less efficient than #delete but allows cleanup methods and other actions to be run.
+      #
+      # This essentially finds the object (or multiple objects) with the given id, creates a new object
+      # from the attributes, and then calls destroy on it.
+      #
+      # ==== Parameters
+      #
+      # * +id+ - This should be the id or an array of ids to be destroyed.
+      #
+      # ==== Examples
+      #
+      #   # Destroy a single object
+      #   Todo.destroy(1)
+      #
+      #   # Destroy multiple objects
+      #   todos = [1,2,3]
+      #   Todo.destroy(todos)
+      def destroy(id)
+        if id.is_a?(Array)
+          find(id).each(&:destroy)
+        else
+          find(id).destroy
+        end
+      end
+
+      # Deletes the row with a primary key matching the +id+ argument, using a
+      # SQL +DELETE+ statement, and returns the number of rows deleted. Active
+      # Record objects are not instantiated, so the object's callbacks are not
+      # executed, including any <tt>:dependent</tt> association options.
+      #
+      # You can delete multiple rows at once by passing an Array of <tt>id</tt>s.
+      #
+      # Note: Although it is often much faster than the alternative, #destroy,
+      # skipping callbacks might bypass business logic in your application
+      # that ensures referential integrity or performs other essential jobs.
+      #
+      # ==== Examples
+      #
+      #   # Delete a single row
+      #   Todo.delete(1)
+      #
+      #   # Delete multiple rows
+      #   Todo.delete([2,3,4])
+      def delete(id_or_array)
+        where(primary_key => id_or_array).delete_all
+      end
+
+      def _insert_record(values) # :nodoc:
+        primary_key_value = nil
+
+        if primary_key && Hash === values
+          arel_primary_key = arel_attribute(primary_key)
+          primary_key_value = values[arel_primary_key]
+
+          if !primary_key_value && prefetch_primary_key?
+            primary_key_value = next_sequence_value
+            values[arel_primary_key] = primary_key_value
+          end
+        end
+
+        if values.empty?
+          im = arel_table.compile_insert(connection.empty_insert_statement_value)
+          im.into arel_table
+        else
+          im = arel_table.compile_insert(_substitute_values(values))
+        end
+
+        connection.insert(im, "#{self} Create", primary_key || false, primary_key_value)
+      end
+
+      def _update_record(values, id, id_was) # :nodoc:
+        bind = predicate_builder.build_bind_attribute(primary_key, id_was || id)
+        um = arel_table.where(
+          arel_attribute(primary_key).eq(bind)
+        ).compile_update(_substitute_values(values), primary_key)
+
+        connection.update(um, "#{self} Update")
+      end
+
       private
         # Called by +instantiate+ to decide which class to use for a new
         # record instance.
@@ -80,6 +206,13 @@ module ActiveRecord
         def discriminate_class_for_record(record)
           self
         end
+
+        def _substitute_values(values)
+          values.map do |attr, value|
+            bind = predicate_builder.build_bind_attribute(attr.name, value)
+            [attr, bind]
+          end
+        end
     end
 
     # Returns true if this object hasn't been saved yet -- that is, a record
@@ -228,7 +361,7 @@ module ActiveRecord
     def becomes(klass)
       became = klass.new
       became.instance_variable_set("@attributes", @attributes)
-      became.instance_variable_set("@mutation_tracker", @mutation_tracker) if defined?(@mutation_tracker)
+      became.instance_variable_set("@mutations_from_database", @mutations_from_database) if defined?(@mutations_from_database)
       became.instance_variable_set("@changed_attributes", attributes_changed_by_setter)
       became.instance_variable_set("@new_record", new_record?)
       became.instance_variable_set("@destroyed", destroyed?)
@@ -577,7 +710,7 @@ module ActiveRecord
         rows_affected = 0
         @_trigger_update_callback = true
       else
-        rows_affected = self.class.unscoped._update_record attributes_values, id, id_in_database
+        rows_affected = self.class._update_record(attributes_values, id, id_in_database)
         @_trigger_update_callback = rows_affected > 0
       end
 
@@ -591,7 +724,7 @@ module ActiveRecord
     def _create_record(attribute_names = self.attribute_names)
       attributes_values = arel_attributes_with_values_for_create(attribute_names)
 
-      new_id = self.class.unscoped.insert attributes_values
+      new_id = self.class._insert_record(attributes_values)
       self.id ||= new_id if self.class.primary_key
 
       @new_record = false
diff --git a/activerecord/lib/active_record/query_cache.rb b/activerecord/lib/active_record/query_cache.rb
index 3d5babb8b7..8e23128333 100644
--- a/activerecord/lib/active_record/query_cache.rb
+++ b/activerecord/lib/active_record/query_cache.rb
@@ -26,16 +26,19 @@ module ActiveRecord
     end
 
     def self.run
-      caching_pool = ActiveRecord::Base.connection_pool
-      caching_was_enabled = caching_pool.query_cache_enabled
+      ActiveRecord::Base.connection_handler.connection_pool_list.map do |pool|
+        caching_was_enabled = pool.query_cache_enabled
 
-      caching_pool.enable_query_cache!
+        pool.enable_query_cache!
 
-      [caching_pool, caching_was_enabled]
+        [pool, caching_was_enabled]
+      end
     end
 
-    def self.complete((caching_pool, caching_was_enabled))
-      caching_pool.disable_query_cache! unless caching_was_enabled
+    def self.complete(caching_pools)
+      caching_pools.each do |pool, caching_was_enabled|
+        pool.disable_query_cache! unless caching_was_enabled
+      end
 
       ActiveRecord::Base.connection_handler.connection_pool_list.each do |pool|
         pool.release_connection if pool.active_connection? && !pool.connection.transaction_open?
diff --git a/activerecord/lib/active_record/querying.rb b/activerecord/lib/active_record/querying.rb
index f780538319..3996d5661f 100644
--- a/activerecord/lib/active_record/querying.rb
+++ b/activerecord/lib/active_record/querying.rb
@@ -7,7 +7,7 @@ module ActiveRecord
     delegate :first_or_create, :first_or_create!, :first_or_initialize, to: :all
     delegate :find_or_create_by, :find_or_create_by!, :find_or_initialize_by, to: :all
     delegate :find_by, :find_by!, to: :all
-    delegate :destroy, :destroy_all, :delete, :delete_all, :update, :update_all, to: :all
+    delegate :destroy_all, :delete_all, :update_all, to: :all
     delegate :find_each, :find_in_batches, :in_batches, to: :all
     delegate :select, :group, :order, :except, :reorder, :limit, :offset, :joins, :left_joins, :left_outer_joins, :or,
              :where, :rewhere, :preload, :eager_load, :includes, :from, :lock, :readonly, :extending,
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index ead42d64ec..4538ed6a5f 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -53,8 +53,8 @@ module ActiveRecord
     # to avoid cross references when loading a constant for the
     # first time. Also, make it output to STDERR.
     console do |app|
-      require_relative "railties/console_sandbox" if app.sandbox?
-      require_relative "base"
+      require "active_record/railties/console_sandbox" if app.sandbox?
+      require "active_record/base"
       unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDERR, STDOUT)
         console = ActiveSupport::Logger.new(STDERR)
         Rails.logger.extend ActiveSupport::Logger.broadcast console
@@ -62,7 +62,7 @@ module ActiveRecord
     end
 
     runner do
-      require_relative "base"
+      require "active_record/base"
     end
 
     initializer "active_record.initialize_timezone" do
@@ -90,12 +90,15 @@ module ActiveRecord
             filename = File.join(app.config.paths["db"].first, "schema_cache.yml")
 
             if File.file?(filename)
+              current_version = ActiveRecord::Migrator.current_version
+              next if current_version.nil?
+
               cache = YAML.load(File.read(filename))
-              if cache.version == ActiveRecord::Migrator.current_version
+              if cache.version == current_version
                 connection.schema_cache = cache
                 connection_pool.schema_cache = cache.dup
               else
-                warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{ActiveRecord::Migrator.current_version}, but the one in the cache is #{cache.version}."
+                warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{current_version}, but the one in the cache is #{cache.version}."
               end
             end
           end
@@ -106,7 +109,7 @@ module ActiveRecord
     initializer "active_record.warn_on_records_fetched_greater_than" do
       if config.active_record.warn_on_records_fetched_greater_than
         ActiveSupport.on_load(:active_record) do
-          require_relative "relation/record_fetch_warning"
+          require "active_record/relation/record_fetch_warning"
         end
       end
     end
@@ -146,7 +149,7 @@ end_warning
 
     # Expose database runtime to controller for logging.
     initializer "active_record.log_runtime" do
-      require_relative "railties/controller_runtime"
+      require "active_record/railties/controller_runtime"
       ActiveSupport.on_load(:action_controller) do
         include ActiveRecord::Railties::ControllerRuntime
       end
@@ -177,7 +180,16 @@ end_warning
     initializer "active_record.clear_active_connections" do
       config.after_initialize do
         ActiveSupport.on_load(:active_record) do
+          # Ideally the application doesn't connect to the database during boot,
+          # but sometimes it does. In case it did, we want to empty out the
+          # connection pools so that a non-database-using process (e.g. a master
+          # process in a forking server model) doesn't retain a needless
+          # connection. If it was needed, the incremental cost of reestablishing
+          # this connection is trivial: the rest of the pool would need to be
+          # populated anyway.
+
           clear_active_connections!
+          flush_idle_connections!
         end
       end
     end
diff --git a/activerecord/lib/active_record/railties/controller_runtime.rb b/activerecord/lib/active_record/railties/controller_runtime.rb
index 3cf66980a5..2ae733f657 100644
--- a/activerecord/lib/active_record/railties/controller_runtime.rb
+++ b/activerecord/lib/active_record/railties/controller_runtime.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attr_internal"
-require_relative "../log_subscriber"
+require "active_record/log_subscriber"
 
 module ActiveRecord
   module Railties # :nodoc:
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index 691b3612d8..fce3e1c5cf 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -4,16 +4,16 @@ require "active_record"
 
 db_namespace = namespace :db do
   desc "Set the environment value for the database"
-  task "environment:set" => [:environment, :load_config] do
+  task "environment:set" => :load_config do
     ActiveRecord::InternalMetadata.create_table
     ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
   end
 
-  task check_protected_environments: [:environment, :load_config] do
+  task check_protected_environments: :load_config do
     ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
   end
 
-  task :load_config do
+  task load_config: :environment do
     ActiveRecord::Base.configurations       = ActiveRecord::Tasks::DatabaseTasks.database_configuration || {}
     ActiveRecord::Migrator.migrations_paths = ActiveRecord::Tasks::DatabaseTasks.migrations_paths
   end
@@ -56,7 +56,7 @@ db_namespace = namespace :db do
   end
 
   desc "Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog)."
-  task migrate: [:environment, :load_config] do
+  task migrate: :load_config do
     ActiveRecord::Tasks::DatabaseTasks.migrate
     db_namespace["_dump"].invoke
   end
@@ -78,7 +78,7 @@ db_namespace = namespace :db do
 
   namespace :migrate do
     # desc  'Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).'
-    task redo: [:environment, :load_config] do
+    task redo: :load_config do
       raise "Empty VERSION provided" if ENV["VERSION"] && ENV["VERSION"].empty?
 
       if ENV["VERSION"]
@@ -94,24 +94,35 @@ db_namespace = namespace :db do
     task reset: ["db:drop", "db:create", "db:migrate"]
 
     # desc 'Runs the "up" for a given migration VERSION.'
-    task up: [:environment, :load_config] do
+    task up: :load_config do
       raise "VERSION is required" if !ENV["VERSION"] || ENV["VERSION"].empty?
 
-      version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
-      ActiveRecord::Migrator.run(:up, ActiveRecord::Tasks::DatabaseTasks.migrations_paths, version)
+      ActiveRecord::Tasks::DatabaseTasks.check_target_version
+
+      ActiveRecord::Migrator.run(
+        :up,
+        ActiveRecord::Tasks::DatabaseTasks.migrations_paths,
+        ActiveRecord::Tasks::DatabaseTasks.target_version
+      )
       db_namespace["_dump"].invoke
     end
 
     # desc 'Runs the "down" for a given migration VERSION.'
-    task down: [:environment, :load_config] do
+    task down: :load_config do
       raise "VERSION is required - To go down one migration, use db:rollback" if !ENV["VERSION"] || ENV["VERSION"].empty?
-      version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
-      ActiveRecord::Migrator.run(:down, ActiveRecord::Tasks::DatabaseTasks.migrations_paths, version)
+
+      ActiveRecord::Tasks::DatabaseTasks.check_target_version
+
+      ActiveRecord::Migrator.run(
+        :down,
+        ActiveRecord::Tasks::DatabaseTasks.migrations_paths,
+        ActiveRecord::Tasks::DatabaseTasks.target_version
+      )
       db_namespace["_dump"].invoke
     end
 
     desc "Display status of migrations"
-    task status: [:environment, :load_config] do
+    task status: :load_config do
       unless ActiveRecord::SchemaMigration.table_exists?
         abort "Schema migrations table does not exist yet."
       end
@@ -129,14 +140,14 @@ db_namespace = namespace :db do
   end
 
   desc "Rolls the schema back to the previous version (specify steps w/ STEP=n)."
-  task rollback: [:environment, :load_config] do
+  task rollback: :load_config do
     step = ENV["STEP"] ? ENV["STEP"].to_i : 1
     ActiveRecord::Migrator.rollback(ActiveRecord::Tasks::DatabaseTasks.migrations_paths, step)
     db_namespace["_dump"].invoke
   end
 
   # desc 'Pushes the schema to the next version (specify steps w/ STEP=n).'
-  task forward: [:environment, :load_config] do
+  task forward: :load_config do
     step = ENV["STEP"] ? ENV["STEP"].to_i : 1
     ActiveRecord::Migrator.forward(ActiveRecord::Tasks::DatabaseTasks.migrations_paths, step)
     db_namespace["_dump"].invoke
@@ -146,12 +157,12 @@ db_namespace = namespace :db do
   task reset: [ "db:drop", "db:setup" ]
 
   # desc "Retrieves the charset for the current environment's database"
-  task charset: [:environment, :load_config] do
+  task charset: :load_config do
     puts ActiveRecord::Tasks::DatabaseTasks.charset_current
   end
 
   # desc "Retrieves the collation for the current environment's database"
-  task collation: [:environment, :load_config] do
+  task collation: :load_config do
     begin
       puts ActiveRecord::Tasks::DatabaseTasks.collation_current
     rescue NoMethodError
@@ -160,12 +171,12 @@ db_namespace = namespace :db do
   end
 
   desc "Retrieves the current schema version number"
-  task version: [:environment, :load_config] do
+  task version: :load_config do
     puts "Current version: #{ActiveRecord::Migrator.current_version}"
   end
 
   # desc "Raises an error if there are pending migrations"
-  task abort_if_pending_migrations: [:environment, :load_config] do
+  task abort_if_pending_migrations: :load_config do
     pending_migrations = ActiveRecord::Migrator.open(ActiveRecord::Tasks::DatabaseTasks.migrations_paths).pending_migrations
 
     if pending_migrations.any?
@@ -188,8 +199,8 @@ db_namespace = namespace :db do
 
   namespace :fixtures do
     desc "Loads fixtures into the current environment's database. Load specific fixtures using FIXTURES=x,y. Load from subdirectory in test/fixtures using FIXTURES_DIR=z. Specify an alternative path (eg. spec/fixtures) using FIXTURES_PATH=spec/fixtures."
-    task load: [:environment, :load_config] do
-      require_relative "../fixtures"
+    task load: :load_config do
+      require "active_record/fixtures"
 
       base_dir = ActiveRecord::Tasks::DatabaseTasks.fixtures_path
 
@@ -210,8 +221,8 @@ db_namespace = namespace :db do
     end
 
     # desc "Search for a fixture given a LABEL or ID. Specify an alternative path (eg. spec/fixtures) using FIXTURES_PATH=spec/fixtures."
-    task identify: [:environment, :load_config] do
-      require_relative "../fixtures"
+    task identify: :load_config do
+      require "active_record/fixtures"
 
       label, id = ENV["LABEL"], ENV["ID"]
       raise "LABEL or ID required" if label.blank? && id.blank?
@@ -236,8 +247,8 @@ db_namespace = namespace :db do
 
   namespace :schema do
     desc "Creates a db/schema.rb file that is portable against any DB supported by Active Record"
-    task dump: [:environment, :load_config] do
-      require_relative "../schema_dumper"
+    task dump: :load_config do
+      require "active_record/schema_dumper"
       filename = ENV["SCHEMA"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema.rb")
       File.open(filename, "w:utf-8") do |file|
         ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
@@ -246,7 +257,7 @@ db_namespace = namespace :db do
     end
 
     desc "Loads a schema.rb file into the database"
-    task load: [:environment, :load_config, :check_protected_environments] do
+    task load: [:load_config, :check_protected_environments] do
       ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, ENV["SCHEMA"])
     end
 
@@ -256,14 +267,14 @@ db_namespace = namespace :db do
 
     namespace :cache do
       desc "Creates a db/schema_cache.yml file."
-      task dump: [:environment, :load_config] do
+      task dump: :load_config do
         conn = ActiveRecord::Base.connection
         filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.yml")
         ActiveRecord::Tasks::DatabaseTasks.dump_schema_cache(conn, filename)
       end
 
       desc "Clears a db/schema_cache.yml file."
-      task clear: [:environment, :load_config] do
+      task clear: :load_config do
         filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.yml")
         rm_f filename, verbose: false
       end
@@ -273,7 +284,7 @@ db_namespace = namespace :db do
 
   namespace :structure do
     desc "Dumps the database structure to db/structure.sql. Specify another file with SCHEMA=db/my_structure.sql"
-    task dump: [:environment, :load_config] do
+    task dump: :load_config do
       filename = ENV["SCHEMA"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "structure.sql")
       current_config = ActiveRecord::Tasks::DatabaseTasks.current_config
       ActiveRecord::Tasks::DatabaseTasks.structure_dump(current_config, filename)
@@ -288,7 +299,7 @@ db_namespace = namespace :db do
     end
 
     desc "Recreates the databases from the structure.sql file"
-    task load: [:environment, :load_config, :check_protected_environments] do
+    task load: [:load_config, :check_protected_environments] do
       ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:sql, ENV["SCHEMA"])
     end
 
@@ -313,7 +324,7 @@ db_namespace = namespace :db do
       begin
         should_reconnect = ActiveRecord::Base.connection_pool.active_connection?
         ActiveRecord::Schema.verbose = false
-        ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :ruby, ENV["SCHEMA"]
+        ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :ruby, ENV["SCHEMA"], "test"
       ensure
         if should_reconnect
           ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[ActiveRecord::Tasks::DatabaseTasks.env])
@@ -323,16 +334,16 @@ db_namespace = namespace :db do
 
     # desc "Recreate the test database from an existent structure.sql file"
     task load_structure: %w(db:test:purge) do
-      ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :sql, ENV["SCHEMA"]
+      ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :sql, ENV["SCHEMA"], "test"
     end
 
     # desc "Empty the test database"
-    task purge: %w(environment load_config check_protected_environments) do
+    task purge: %w(load_config check_protected_environments) do
       ActiveRecord::Tasks::DatabaseTasks.purge ActiveRecord::Base.configurations["test"]
     end
 
     # desc 'Load the test schema'
-    task prepare: %w(environment load_config) do
+    task prepare: :load_config do
       unless ActiveRecord::Base.configurations.blank?
         db_namespace["test:load"].invoke
       end
diff --git a/activerecord/lib/active_record/railties/jdbcmysql_error.rb b/activerecord/lib/active_record/railties/jdbcmysql_error.rb
deleted file mode 100644
index 72c75ddd52..0000000000
--- a/activerecord/lib/active_record/railties/jdbcmysql_error.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-# frozen_string_literal: true
-
-#FIXME Remove if ArJdbcMysql will give.
-module ArJdbcMySQL #:nodoc:
-  class Error < StandardError #:nodoc:
-    attr_accessor :error_number, :sql_state
-
-    def initialize(msg)
-      super
-      @error_number = nil
-      @sql_state    = nil
-    end
-
-    # Mysql gem compatibility
-    alias_method :errno, :error_number
-    alias_method :error, :message
-  end
-end
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 889e24dd1a..87bfd75bca 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/string/filters"
-require "active_support/deprecation"
 require "concurrent/map"
 
 module ActiveRecord
@@ -174,11 +173,6 @@ module ActiveRecord
         scope ? [scope] : []
       end
 
-      def scope_chain
-        chain.map(&:scopes)
-      end
-      deprecate :scope_chain
-
       def build_join_constraint(table, foreign_table)
         key         = join_keys.key
         foreign_key = join_keys.foreign_key
@@ -292,13 +286,17 @@ module ActiveRecord
       end
 
       def get_join_keys(association_klass)
-        JoinKeys.new(join_pk(association_klass), join_foreign_key)
+        JoinKeys.new(join_primary_key(association_klass), join_foreign_key)
       end
 
       def build_scope(table, predicate_builder = predicate_builder(table))
         Relation.create(klass, table, predicate_builder)
       end
 
+      def join_primary_key(_)
+        foreign_key
+      end
+
       def join_foreign_key
         active_record_primary_key
       end
@@ -313,10 +311,6 @@ module ActiveRecord
           PredicateBuilder.new(TableMetadata.new(klass, table))
         end
 
-        def join_pk(_)
-          foreign_key
-        end
-
         def primary_key(klass)
           klass.primary_key || raise(UnknownPrimaryKey.new(klass))
         end
@@ -425,21 +419,13 @@ module ActiveRecord
 
       def initialize(name, scope, options, active_record)
         super
-        @automatic_inverse_of = nil
         @type         = options[:as] && (options[:foreign_type] || "#{options[:as]}_type")
-        @foreign_type = options[:foreign_type] || "#{name}_type"
+        @foreign_type = options[:polymorphic] && (options[:foreign_type] || "#{name}_type")
         @constructable = calculate_constructable(macro, options)
         @association_scope_cache = Concurrent::Map.new
 
         if options[:class_name] && options[:class_name].class == Class
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Passing a class to the `class_name` is deprecated and will raise
-            an ArgumentError in Rails 5.2. It eagerloads more classes than
-            necessary and potentially creates circular dependencies.
-
-            Please pass the class name as a string:
-            `#{macro} :#{name}, class_name: '#{options[:class_name]}'`
-          MSG
+          raise ArgumentError, "A class was passed to `:class_name` but we are expecting a string."
         end
       end
 
@@ -609,12 +595,14 @@ module ActiveRecord
         # If it cannot find a suitable inverse association name, it returns
         # +nil+.
         def inverse_name
-          options.fetch(:inverse_of) do
-            @automatic_inverse_of ||= automatic_inverse_of
+          unless defined?(@inverse_name)
+            @inverse_name = options.fetch(:inverse_of) { automatic_inverse_of }
           end
+
+          @inverse_name
         end
 
-        # returns either false or the inverse association name that it finds.
+        # returns either +nil+ or the inverse association name that it finds.
         def automatic_inverse_of
           if can_find_inverse_of_automatically?(self)
             inverse_name = ActiveSupport::Inflector.underscore(options[:as] || active_record.name.demodulize).to_sym
@@ -631,8 +619,6 @@ module ActiveRecord
               return inverse_name
             end
           end
-
-          false
         end
 
         # Checks if the inverse reflection that is returned from the
@@ -736,6 +722,10 @@ module ActiveRecord
         end
       end
 
+      def join_primary_key(klass)
+        polymorphic? ? association_primary_key(klass) : association_primary_key
+      end
+
       def join_foreign_key
         foreign_key
       end
@@ -745,10 +735,6 @@ module ActiveRecord
         def calculate_constructable(macro, options)
           !polymorphic?
         end
-
-        def join_pk(klass)
-          polymorphic? ? association_primary_key(klass) : association_primary_key
-        end
     end
 
     class HasAndBelongsToManyReflection < AssociationReflection # :nodoc:
@@ -853,10 +839,6 @@ module ActiveRecord
         source_reflection.join_scopes(table, predicate_builder) + super
       end
 
-      def source_type_scope
-        through_reflection.klass.where(foreign_type => options[:source_type])
-      end
-
       def has_scope?
         scope || options[:source_type] ||
           source_reflection.has_scope? ||
@@ -1016,29 +998,24 @@ module ActiveRecord
     end
 
     class PolymorphicReflection < AbstractReflection # :nodoc:
-      delegate :klass, :scope, :plural_name, :type, :get_join_keys, to: :@reflection
+      delegate :klass, :scope, :plural_name, :type, :get_join_keys, :scope_for, to: :@reflection
 
       def initialize(reflection, previous_reflection)
         @reflection = reflection
         @previous_reflection = previous_reflection
       end
 
-      def scopes
-        scopes = @previous_reflection.scopes
-        scopes << @previous_reflection.source_type_scope
-      end
-
       def join_scopes(table, predicate_builder) # :nodoc:
         scopes = @previous_reflection.join_scopes(table, predicate_builder) + super
-        scopes << @previous_reflection.source_type_scope
+        scopes << build_scope(table, predicate_builder).instance_exec(nil, &source_type_scope)
       end
 
       def constraints
-        @reflection.constraints + [source_type_info]
+        @reflection.constraints + [source_type_scope]
       end
 
       private
-        def source_type_info
+        def source_type_scope
           type = @previous_reflection.foreign_type
           source_type = @previous_reflection.options[:source_type]
           lambda { |object| where(type => source_type) }
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 42a9d8492b..081ef5771f 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -36,67 +36,6 @@ module ActiveRecord
       reset
     end
 
-    def insert(values) # :nodoc:
-      primary_key_value = nil
-
-      if primary_key && Hash === values
-        primary_key_value = values[values.keys.find { |k|
-          k.name == primary_key
-        }]
-
-        if !primary_key_value && klass.prefetch_primary_key?
-          primary_key_value = klass.next_sequence_value
-          values[arel_attribute(klass.primary_key)] = primary_key_value
-        end
-      end
-
-      im = arel.create_insert
-      im.into @table
-
-      substitutes = substitute_values values
-
-      if values.empty? # empty insert
-        im.values = Arel.sql(connection.empty_insert_statement_value)
-      else
-        im.insert substitutes
-      end
-
-      @klass.connection.insert(
-        im,
-        "SQL",
-        primary_key || false,
-        primary_key_value,
-        nil,
-      )
-    end
-
-    def _update_record(values, id, id_was) # :nodoc:
-      substitutes = substitute_values values
-
-      scope = @klass.unscoped
-
-      if @klass.finder_needs_type_condition?
-        scope.unscope!(where: @klass.inheritance_column)
-      end
-
-      relation = scope.where(@klass.primary_key => (id_was || id))
-      um = relation
-        .arel
-        .compile_update(substitutes, @klass.primary_key)
-
-      @klass.connection.update(
-        um,
-        "SQL",
-      )
-    end
-
-    def substitute_values(values) # :nodoc:
-      values.map do |arel_attr, value|
-        bind = predicate_builder.build_bind_attribute(arel_attr.name, value)
-        [arel_attr, bind]
-      end
-    end
-
     def arel_attribute(name) # :nodoc:
       klass.arel_attribute(name, table)
     end
@@ -243,9 +182,10 @@ module ActiveRecord
     end
 
     # Converts relation objects to Array.
-    def to_a
+    def to_ary
       records.dup
     end
+    alias to_a to_ary
 
     def records # :nodoc:
       load
@@ -359,6 +299,11 @@ module ActiveRecord
     def update_all(updates)
       raise ArgumentError, "Empty list of attributes to change" if updates.blank?
 
+      if eager_loading?
+        relation = apply_join_dependency
+        return relation.update_all(updates)
+      end
+
       stmt = Arel::UpdateManager.new
 
       stmt.set Arel.sql(@klass.send(:sanitize_sql_for_assignment, updates))
@@ -373,51 +318,7 @@ module ActiveRecord
         stmt.wheres = arel.constraints
       end
 
-      @klass.connection.update stmt, "SQL"
-    end
-
-    # Updates an object (or multiple objects) and saves it to the database, if validations pass.
-    # The resulting object is returned whether the object was saved successfully to the database or not.
-    #
-    # ==== Parameters
-    #
-    # * +id+ - This should be the id or an array of ids to be updated.
-    # * +attributes+ - This should be a hash of attributes or an array of hashes.
-    #
-    # ==== Examples
-    #
-    #   # Updates one record
-    #   Person.update(15, user_name: 'Samuel', group: 'expert')
-    #
-    #   # Updates multiple records
-    #   people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
-    #   Person.update(people.keys, people.values)
-    #
-    #   # Updates multiple records from the result of a relation
-    #   people = Person.where(group: 'expert')
-    #   people.update(group: 'masters')
-    #
-    # Note: Updating a large number of records will run an
-    # UPDATE query for each record, which may cause a performance
-    # issue. When running callbacks is not needed for each record update,
-    # it is preferred to use #update_all for updating all records
-    # in a single query.
-    def update(id = :all, attributes)
-      if id.is_a?(Array)
-        id.map.with_index { |one_id, idx| update(one_id, attributes[idx]) }
-      elsif id == :all
-        records.each { |record| record.update(attributes) }
-      else
-        if ActiveRecord::Base === id
-          raise ArgumentError, <<-MSG.squish
-            You are passing an instance of ActiveRecord::Base to `update`.
-            Please pass the id of the object by calling `.id`.
-          MSG
-        end
-        object = find(id)
-        object.update(attributes)
-        object
-      end
+      @klass.connection.update stmt, "#{@klass} Update All"
     end
 
     # Destroys the records by instantiating each
@@ -440,33 +341,6 @@ module ActiveRecord
       records.each(&:destroy).tap { reset }
     end
 
-    # Destroy an object (or multiple objects) that has the given id. The object is instantiated first,
-    # therefore all callbacks and filters are fired off before the object is deleted. This method is
-    # less efficient than #delete but allows cleanup methods and other actions to be run.
-    #
-    # This essentially finds the object (or multiple objects) with the given id, creates a new object
-    # from the attributes, and then calls destroy on it.
-    #
-    # ==== Parameters
-    #
-    # * +id+ - Can be either an Integer or an Array of Integers.
-    #
-    # ==== Examples
-    #
-    #   # Destroy a single object
-    #   Todo.destroy(1)
-    #
-    #   # Destroy multiple objects
-    #   todos = [1,2,3]
-    #   Todo.destroy(todos)
-    def destroy(id)
-      if id.is_a?(Array)
-        id.map { |one_id| destroy(one_id) }
-      else
-        find(id).destroy
-      end
-    end
-
     # Deletes the records without instantiating the records
     # first, and hence not calling the {#destroy}[rdoc-ref:Persistence#destroy]
     # method nor invoking callbacks.
@@ -494,6 +368,11 @@ module ActiveRecord
         raise ActiveRecordError.new("delete_all doesn't support #{invalid_methods.join(', ')}")
       end
 
+      if eager_loading?
+        relation = apply_join_dependency
+        return relation.delete_all
+      end
+
       stmt = Arel::DeleteManager.new
       stmt.from(table)
 
@@ -503,35 +382,12 @@ module ActiveRecord
         stmt.wheres = arel.constraints
       end
 
-      affected = @klass.connection.delete(stmt, "SQL")
+      affected = @klass.connection.delete(stmt, "#{@klass} Destroy")
 
       reset
       affected
     end
 
-    # Deletes the row with a primary key matching the +id+ argument, using a
-    # SQL +DELETE+ statement, and returns the number of rows deleted. Active
-    # Record objects are not instantiated, so the object's callbacks are not
-    # executed, including any <tt>:dependent</tt> association options.
-    #
-    # You can delete multiple rows at once by passing an Array of <tt>id</tt>s.
-    #
-    # Note: Although it is often much faster than the alternative,
-    # #destroy, skipping callbacks might bypass business logic in
-    # your application that ensures referential integrity or performs other
-    # essential jobs.
-    #
-    # ==== Examples
-    #
-    #   # Delete a single row
-    #   Todo.delete(1)
-    #
-    #   # Delete multiple rows
-    #   Todo.delete([2,3,4])
-    def delete(id_or_array)
-      where(primary_key => id_or_array).delete_all
-    end
-
     # Causes the records to be loaded from the database if they have not
     # been loaded already. You can use this if for some reason you need
     # to explicitly load some records before actually using them. The
@@ -645,6 +501,11 @@ module ActiveRecord
       limit_value || offset_value
     end
 
+    def alias_tracker(joins = [], aliases = nil) # :nodoc:
+      joins += [aliases] if aliases
+      ActiveRecord::Associations::AliasTracker.create(connection, table.name, joins)
+    end
+
     protected
 
       def load_records(records)
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index 356ad0dcd6..561869017a 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "batches/batch_enumerator"
+require "active_record/relation/batches/batch_enumerator"
 
 module ActiveRecord
   module Batches
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 42d43224fa..d49472fc70 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -130,7 +130,7 @@ module ActiveRecord
     #      end
     def calculate(operation, column_name)
       if has_include?(column_name)
-        relation = construct_relation_for_association_calculations
+        relation = apply_join_dependency
         relation.distinct! if operation.to_s.downcase == "count"
 
         relation.calculate(operation, column_name)
@@ -180,8 +180,10 @@ module ActiveRecord
       end
 
       if has_include?(column_names.first)
-        construct_relation_for_association_calculations.pluck(*column_names)
+        relation = apply_join_dependency
+        relation.pluck(*column_names)
       else
+        enforce_raw_sql_whitelist(column_names)
         relation = spawn
         relation.select_values = column_names.map { |cn|
           @klass.has_attribute?(cn) || @klass.attribute_alias?(cn) ? arel_attribute(cn) : cn
@@ -215,7 +217,7 @@ module ActiveRecord
         if operation == "count"
           column_name ||= select_for_count
           if column_name == :all
-            if distinct && !(has_limit_or_offset? && order_values.any?)
+            if distinct && (group_values.any? || !(has_limit_or_offset? && order_values.any?))
               column_name = primary_key
             end
           elsif column_name =~ /\s*DISTINCT[\s(]+/i
@@ -391,7 +393,7 @@ module ActiveRecord
       def build_count_subquery(relation, column_name, distinct)
         relation.select_values = [
           if column_name == :all
-            distinct ? table[Arel.star] : Arel.sql("1")
+            distinct ? table[Arel.star] : Arel.sql(FinderMethods::ONE_AS_ONE)
           else
             column_alias = Arel.sql("count_column")
             aggregate_column(column_name).as(column_alias)
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 48af777b69..4863befec8 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -38,7 +38,7 @@ module ActiveRecord
     # may vary depending on the klass of a relation, so we create a subclass of Relation
     # for each different klass, and the delegations are compiled into that subclass only.
 
-    delegate :to_xml, :encode_with, :length, :each, :uniq, :to_ary, :join,
+    delegate :to_xml, :encode_with, :length, :each, :uniq, :join,
              :[], :&, :|, :+, :-, :sample, :reverse, :rotate, :compact, :in_groups, :in_groups_of,
              :to_sentence, :to_formatted_s, :as_json,
              :shuffle, :split, :slice, :index, :rindex, to: :records
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index c92d5a52f4..ff06ecbee1 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -18,9 +18,10 @@ module ActiveRecord
     #   Person.find([1])        # returns an array for the object with ID = 1
     #   Person.where("administrator = 1").order("created_on DESC").find(1)
     #
-    # NOTE: The returned records may not be in the same order as the ids you
-    # provide since database rows are unordered. You will need to provide an explicit QueryMethods#order
-    # option if you want the results to be sorted.
+    # NOTE: The returned records are in the same order as the ids you provide.
+    # If you want the results to be sorted by database, you can use ActiveRecord::QueryMethods#where
+    # method and provide an explicit ActiveRecord::QueryMethods#order option.
+    # But ActiveRecord::QueryMethods#where method doesn't raise ActiveRecord::RecordNotFound.
     #
     # ==== Find with lock
     #
@@ -88,7 +89,7 @@ module ActiveRecord
       where(arg, *args).take!
     rescue ::RangeError
       raise RecordNotFound.new("Couldn't find #{@klass.name} with an out of range value",
-                               @klass.name)
+                               @klass.name, @klass.primary_key)
     end
 
     # Gives a record (or N records if a parameter is supplied) without any implied
@@ -284,7 +285,7 @@ module ActiveRecord
     # * Hash - Finds the record that matches these +find+-style conditions
     #   (such as <tt>{name: 'David'}</tt>).
     # * +false+ - Returns always +false+.
-    # * No args - Returns +false+ if the table is empty, +true+ otherwise.
+    # * No args - Returns +false+ if the relation is empty, +true+ otherwise.
     #
     # For more information about specifying conditions as a hash or array,
     # see the Conditions section in the introduction to ActiveRecord::Base.
@@ -300,6 +301,7 @@ module ActiveRecord
     #   Person.exists?(name: 'David')
     #   Person.exists?(false)
     #   Person.exists?
+    #   Person.where(name: 'Spartacus', rating: 4).exists?
     def exists?(conditions = :none)
       if Base === conditions
         raise ArgumentError, <<-MSG.squish
@@ -310,12 +312,12 @@ module ActiveRecord
 
       return false if !conditions || limit_value == 0
 
-      relation = self unless eager_loading?
-      relation ||= apply_join_dependency(self, construct_join_dependency(eager_loading: false))
-
-      return false if ActiveRecord::NullRelation === relation
+      if eager_loading?
+        relation = apply_join_dependency(construct_join_dependency(eager_loading: false))
+        return relation.exists?(conditions)
+      end
 
-      relation = construct_relation_for_exists(relation, conditions)
+      relation = construct_relation_for_exists(conditions)
 
       skip_query_cache_if_necessary { connection.select_value(relation.arel, "#{name} Exists") } ? true : false
     rescue ::RangeError
@@ -338,7 +340,7 @@ module ActiveRecord
       if ids.nil?
         error = "Couldn't find #{name}".dup
         error << " with#{conditions}" if conditions
-        raise RecordNotFound.new(error, name)
+        raise RecordNotFound.new(error, name, key)
       elsif Array(ids).size == 1
         error = "Couldn't find #{name} with '#{key}'=#{ids}#{conditions}"
         raise RecordNotFound.new(error, name, key, ids)
@@ -346,7 +348,7 @@ module ActiveRecord
         error = "Couldn't find all #{name.pluralize} with '#{key}': ".dup
         error << "(#{ids.join(", ")})#{conditions} (found #{result_size} results, but was looking for #{expected_size})."
         error << " Couldn't find #{name.pluralize(not_found_ids.size)} with #{key.to_s.pluralize(not_found_ids.size)} #{not_found_ids.join(', ')}." if not_found_ids
-        raise RecordNotFound.new(error, name, primary_key, ids)
+        raise RecordNotFound.new(error, name, key, ids)
       end
     end
 
@@ -366,17 +368,16 @@ module ActiveRecord
         # preexisting join in joins_values to categorizations (by way of
         # the `has_many :through` for categories).
         #
-        join_dependency = construct_join_dependency(joins_values)
+        join_dependency = construct_join_dependency
 
-        aliases  = join_dependency.aliases
-        relation = select aliases.columns
-        relation = apply_join_dependency(relation, join_dependency)
+        relation = apply_join_dependency(join_dependency)
+        relation._select!(join_dependency.aliases.columns)
 
         yield relation, join_dependency
       end
 
-      def construct_relation_for_exists(relation, conditions)
-        relation = relation.except(:select, :distinct, :order)._select!(ONE_AS_ONE).limit!(1)
+      def construct_relation_for_exists(conditions)
+        relation = except(:select, :distinct, :order)._select!(ONE_AS_ONE).limit!(1)
 
         case conditions
         when Array, Hash
@@ -388,17 +389,15 @@ module ActiveRecord
         relation
       end
 
-      def construct_join_dependency(joins = [], eager_loading: true)
+      def construct_join_dependency(eager_loading: true)
         including = eager_load_values + includes_values
-        ActiveRecord::Associations::JoinDependency.new(klass, table, including, joins, eager_loading: eager_loading)
-      end
-
-      def construct_relation_for_association_calculations
-        apply_join_dependency(self, construct_join_dependency(joins_values))
+        ActiveRecord::Associations::JoinDependency.new(
+          klass, table, including, alias_tracker(joins_values), eager_loading: eager_loading
+        )
       end
 
-      def apply_join_dependency(relation, join_dependency)
-        relation = relation.except(:includes, :eager_load, :preload).joins!(join_dependency)
+      def apply_join_dependency(join_dependency = construct_join_dependency)
+        relation = except(:includes, :eager_load, :preload).joins!(join_dependency)
 
         if using_limitable_reflections?(join_dependency.reflections)
           relation
@@ -435,9 +434,12 @@ module ActiveRecord
 
         ids = ids.flatten.compact.uniq
 
+        model_name = @klass.name
+
         case ids.size
         when 0
-          raise RecordNotFound, "Couldn't find #{@klass.name} without an ID"
+          error_message = "Couldn't find #{model_name} without an ID"
+          raise RecordNotFound.new(error_message, model_name, primary_key)
         when 1
           result = find_one(ids.first)
           expects_array ? [ result ] : result
@@ -445,7 +447,8 @@ module ActiveRecord
           find_some(ids)
         end
       rescue ::RangeError
-        raise RecordNotFound, "Couldn't find #{@klass.name} with an out of range ID"
+        error_message = "Couldn't find #{model_name} with an out of range ID"
+        raise RecordNotFound.new(error_message, model_name, primary_key, ids)
       end
 
       def find_one(id)
diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index 03824ffff9..b736b21525 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -112,22 +112,20 @@ module ActiveRecord
           if other.klass == relation.klass
             relation.joins!(*other.joins_values)
           else
-            joins_dependency, rest = other.joins_values.partition do |join|
+            alias_tracker = nil
+            joins_dependency = other.joins_values.map do |join|
               case join
               when Hash, Symbol, Array
-                true
+                alias_tracker ||= other.alias_tracker
+                ActiveRecord::Associations::JoinDependency.new(
+                  other.klass, other.table, join, alias_tracker
+                )
               else
-                false
+                join
               end
             end
 
-            join_dependency = ActiveRecord::Associations::JoinDependency.new(
-              other.klass, other.table, joins_dependency, []
-            )
-
-            relation.joins! rest
-
-            @relation = relation.joins join_dependency
+            relation.joins!(*joins_dependency)
           end
         end
 
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index 5c42414072..885c26d7aa 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -13,6 +13,7 @@ module ActiveRecord
       register_handler(Range, RangeHandler.new(self))
       register_handler(Relation, RelationHandler.new)
       register_handler(Array, ArrayHandler.new(self))
+      register_handler(Set, ArrayHandler.new(self))
     end
 
     def build_from_hash(attributes)
@@ -123,11 +124,11 @@ module ActiveRecord
   end
 end
 
-require_relative "predicate_builder/array_handler"
-require_relative "predicate_builder/base_handler"
-require_relative "predicate_builder/basic_object_handler"
-require_relative "predicate_builder/range_handler"
-require_relative "predicate_builder/relation_handler"
+require "active_record/relation/predicate_builder/array_handler"
+require "active_record/relation/predicate_builder/base_handler"
+require "active_record/relation/predicate_builder/basic_object_handler"
+require "active_record/relation/predicate_builder/range_handler"
+require "active_record/relation/predicate_builder/relation_handler"
 
-require_relative "predicate_builder/association_query_value"
-require_relative "predicate_builder/polymorphic_array_value"
+require "active_record/relation/predicate_builder/association_query_value"
+require "active_record/relation/predicate_builder/polymorphic_array_value"
diff --git a/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
index f51ea4fde0..c8bbfa5051 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
@@ -4,6 +4,10 @@ module ActiveRecord
   class PredicateBuilder
     class RelationHandler # :nodoc:
       def call(attribute, value)
+        if value.eager_loading?
+          value = value.send(:apply_join_dependency)
+        end
+
         if value.select_values.empty?
           value = value.select(value.arel_attribute(value.klass.primary_key))
         end
diff --git a/activerecord/lib/active_record/relation/query_attribute.rb b/activerecord/lib/active_record/relation/query_attribute.rb
index 5a9a7fd432..3532f28858 100644
--- a/activerecord/lib/active_record/relation/query_attribute.rb
+++ b/activerecord/lib/active_record/relation/query_attribute.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../attribute"
+require "active_model/attribute"
 
 module ActiveRecord
   class Relation
-    class QueryAttribute < Attribute # :nodoc:
+    class QueryAttribute < ActiveModel::Attribute # :nodoc:
       def type_cast(value)
         value
       end
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index c88603fde2..749223422f 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "from_clause"
-require_relative "query_attribute"
-require_relative "where_clause"
-require_relative "where_clause_factory"
+require "active_record/relation/from_clause"
+require "active_record/relation/query_attribute"
+require "active_record/relation/where_clause"
+require "active_record/relation/where_clause_factory"
 require "active_model/forbidden_attributes_protection"
 
 module ActiveRecord
@@ -295,6 +295,7 @@ module ActiveRecord
       spawn.order!(*args)
     end
 
+    # Same as #order but operates on relation in-place instead of copying.
     def order!(*args) # :nodoc:
       preprocess_order_args(args)
 
@@ -316,6 +317,7 @@ module ActiveRecord
       spawn.reorder!(*args)
     end
 
+    # Same as #reorder but operates on relation in-place instead of copying.
     def reorder!(*args) # :nodoc:
       preprocess_order_args(args)
 
@@ -441,7 +443,7 @@ module ActiveRecord
     #   => SELECT "users".* FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
     #
     def left_outer_joins(*args)
-      check_if_method_has_arguments!(:left_outer_joins, args)
+      check_if_method_has_arguments!(__callee__, args)
 
       args.compact!
       args.flatten!
@@ -898,8 +900,8 @@ module ActiveRecord
     end
 
     # Returns the Arel object associated with the relation.
-    def arel # :nodoc:
-      @arel ||= build_arel
+    def arel(aliases = nil) # :nodoc:
+      @arel ||= build_arel(aliases)
     end
 
     protected
@@ -921,16 +923,16 @@ module ActiveRecord
         raise ImmutableRelation if defined?(@arel) && @arel
       end
 
-      def build_arel
+      def build_arel(aliases)
         arel = Arel::SelectManager.new(table)
 
-        build_joins(arel, joins_values.flatten) unless joins_values.empty?
-        build_left_outer_joins(arel, left_outer_joins_values.flatten) unless left_outer_joins_values.empty?
+        aliases = build_joins(arel, joins_values.flatten, aliases) unless joins_values.empty?
+        build_left_outer_joins(arel, left_outer_joins_values.flatten, aliases) unless left_outer_joins_values.empty?
 
         arel.where(where_clause.ast) unless where_clause.empty?
         arel.having(having_clause.ast) unless having_clause.empty?
         if limit_value
-          limit_attribute = Attribute.with_cast_value(
+          limit_attribute = ActiveModel::Attribute.with_cast_value(
             "LIMIT".freeze,
             connection.sanitize_limit(limit_value),
             Type.default_value,
@@ -938,7 +940,7 @@ module ActiveRecord
           arel.take(Arel::Nodes::BindParam.new(limit_attribute))
         end
         if offset_value
-          offset_attribute = Attribute.with_cast_value(
+          offset_attribute = ActiveModel::Attribute.with_cast_value(
             "OFFSET".freeze,
             offset_value.to_i,
             Type.default_value,
@@ -963,6 +965,9 @@ module ActiveRecord
         name = from_clause.name
         case opts
         when Relation
+          if opts.eager_loading?
+            opts = opts.send(:apply_join_dependency)
+          end
           name ||= "subquery"
           opts.arel.as(name.to_s)
         else
@@ -970,7 +975,7 @@ module ActiveRecord
         end
       end
 
-      def build_left_outer_joins(manager, outer_joins)
+      def build_left_outer_joins(manager, outer_joins, aliases)
         buckets = outer_joins.group_by do |join|
           case join
           when Hash, Symbol, Array
@@ -980,10 +985,10 @@ module ActiveRecord
           end
         end
 
-        build_join_query(manager, buckets, Arel::Nodes::OuterJoin)
+        build_join_query(manager, buckets, Arel::Nodes::OuterJoin, aliases)
       end
 
-      def build_joins(manager, joins)
+      def build_joins(manager, joins, aliases)
         buckets = joins.group_by do |join|
           case join
           when String
@@ -999,10 +1004,10 @@ module ActiveRecord
           end
         end
 
-        build_join_query(manager, buckets, Arel::Nodes::InnerJoin)
+        build_join_query(manager, buckets, Arel::Nodes::InnerJoin, aliases)
       end
 
-      def build_join_query(manager, buckets, join_type)
+      def build_join_query(manager, buckets, join_type, aliases)
         buckets.default = []
 
         association_joins         = buckets[:association_join]
@@ -1011,9 +1016,10 @@ module ActiveRecord
         string_joins              = buckets[:string_join].map(&:strip).uniq
 
         join_list = join_nodes + convert_join_strings_to_ast(manager, string_joins)
+        alias_tracker = alias_tracker(join_list, aliases)
 
         join_dependency = ActiveRecord::Associations::JoinDependency.new(
-          klass, table, association_joins, join_list
+          klass, table, association_joins, alias_tracker
         )
 
         joins = join_dependency.join_constraints(stashed_association_joins, join_type)
@@ -1021,7 +1027,7 @@ module ActiveRecord
 
         manager.join_sources.concat(join_list)
 
-        manager
+        alias_tracker.aliases
       end
 
       def convert_join_strings_to_ast(table, joins)
@@ -1034,6 +1040,8 @@ module ActiveRecord
       def build_select(arel)
         if select_values.any?
           arel.project(*arel_columns(select_values.uniq))
+        elsif @klass.ignored_columns.any?
+          arel.project(*arel_columns(@klass.column_names))
         else
           arel.project(table[Arel.star])
         end
@@ -1070,7 +1078,7 @@ module ActiveRecord
             end
             o.split(",").map! do |s|
               s.strip!
-              s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || s.concat(" DESC")
+              s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || (s << " DESC")
             end
           else
             o
@@ -1079,6 +1087,10 @@ module ActiveRecord
       end
 
       def does_not_support_reverse?(order)
+        # Account for String subclasses like Arel::Nodes::SqlLiteral that
+        # override methods like #count.
+        order = String.new(order) unless order.instance_of?(String)
+
         # Uses SQL function with multiple arguments.
         (order.include?(",") && order.split(",").find { |section| section.count("(") != section.count(")") }) ||
           # Uses "nulls first" like construction.
@@ -1112,6 +1124,12 @@ module ActiveRecord
           klass.send(:sanitize_sql_for_order, arg)
         end
         order_args.flatten!
+
+        @klass.enforce_raw_sql_whitelist(
+          order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a },
+          whitelist: AttributeMethods::ClassMethods::COLUMN_NAME_ORDER_WHITELIST
+        )
+
         validate_order_args(order_args)
 
         references = order_args.grep(String)
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index 424894f835..617d8de8b2 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -2,7 +2,7 @@
 
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/hash/slice"
-require_relative "merger"
+require "active_record/relation/merger"
 
 module ActiveRecord
   module SpawnMethods
diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index 752bb38481..a502713e56 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -47,7 +47,7 @@ module ActiveRecord
       end
 
       def to_h(table_name = nil)
-        equalities = predicates.grep(Arel::Nodes::Equality)
+        equalities = equalities(predicates)
         if table_name
           equalities = equalities.select do |node|
             node.left.relation.name == table_name
@@ -90,6 +90,20 @@ module ActiveRecord
         end
 
       private
+        def equalities(predicates)
+          equalities = []
+
+          predicates.each do |node|
+            case node
+            when Arel::Nodes::Equality
+              equalities << node
+            when Arel::Nodes::And
+              equalities.concat equalities(node.children)
+            end
+          end
+
+          equalities
+        end
 
         def predicates_unreferenced_by(other)
           predicates.reject do |n|
@@ -121,7 +135,7 @@ module ActiveRecord
         end
 
         def except_predicates(columns)
-          self.predicates.reject do |node|
+          predicates.reject do |node|
             case node
             when Arel::Nodes::Between, Arel::Nodes::In, Arel::Nodes::NotIn, Arel::Nodes::Equality, Arel::Nodes::NotEqual, Arel::Nodes::LessThan, Arel::Nodes::LessThanOrEqual, Arel::Nodes::GreaterThan, Arel::Nodes::GreaterThanOrEqual
               subrelation = (node.left.kind_of?(Arel::Attributes::Attribute) ? node.left : node.right)
diff --git a/activerecord/lib/active_record/sanitization.rb b/activerecord/lib/active_record/sanitization.rb
index 91a4f1fad6..21f8bc7cb2 100644
--- a/activerecord/lib/active_record/sanitization.rb
+++ b/activerecord/lib/active_record/sanitization.rb
@@ -30,8 +30,6 @@ module ActiveRecord
           end
         end
         alias :sanitize_sql :sanitize_sql_for_conditions
-        alias :sanitize_conditions :sanitize_sql
-        deprecate sanitize_conditions: :sanitize_sql
 
         # Accepts an array, hash, or string of SQL conditions and sanitizes
         # them into a valid SQL fragment for a SET clause.
@@ -65,7 +63,17 @@ module ActiveRecord
         #   # => "id ASC"
         def sanitize_sql_for_order(condition) # :doc:
           if condition.is_a?(Array) && condition.first.to_s.include?("?")
-            sanitize_sql_array(condition)
+            enforce_raw_sql_whitelist([condition.first],
+              whitelist: AttributeMethods::ClassMethods::COLUMN_NAME_ORDER_WHITELIST
+            )
+
+            # Ensure we aren't dealing with a subclass of String that might
+            # override methods we use (eg. Arel::Nodes::SqlLiteral).
+            if condition.first.kind_of?(String) && !condition.first.instance_of?(String)
+              condition = [String.new(condition.first), *condition[1..-1]]
+            end
+
+            Arel.sql(sanitize_sql_array(condition))
           else
             condition
           end
@@ -112,7 +120,8 @@ module ActiveRecord
         def sanitize_sql_hash_for_assignment(attrs, table) # :doc:
           c = connection
           attrs.map do |attr, value|
-            value = type_for_attribute(attr.to_s).serialize(value)
+            type = type_for_attribute(attr.to_s)
+            value = type.serialize(type.cast(value))
             "#{c.quote_table_name_for_assignment(table, attr)} = #{c.quote(value)}"
           end.join(", ")
         end
@@ -207,10 +216,5 @@ module ActiveRecord
           end
         end
     end
-
-    def quoted_id # :nodoc:
-      self.class.connection.quote(@attributes[self.class.primary_key].value_for_database)
-    end
-    deprecate :quoted_id
   end
 end
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 8d0311fabd..16ccba6b6c 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -82,16 +82,8 @@ HEADER
         stream.puts "end"
       end
 
+      # extensions are only supported by PostgreSQL
       def extensions(stream)
-        return unless @connection.supports_extensions?
-        extensions = @connection.extensions
-        if extensions.any?
-          stream.puts "  # These are extensions that must be enabled in order to support this database"
-          extensions.sort.each do |extension|
-            stream.puts "  enable_extension #{extension.inspect}"
-          end
-          stream.puts
-        end
       end
 
       def tables(stream)
@@ -192,8 +184,9 @@ HEADER
           "name: #{index.name.inspect}",
         ]
         index_parts << "unique: true" if index.unique
-        index_parts << "length: { #{format_options(index.lengths)} }" if index.lengths.present?
-        index_parts << "order: { #{format_options(index.orders)} }" if index.orders.present?
+        index_parts << "length: #{format_index_parts(index.lengths)}" if index.lengths.present?
+        index_parts << "order: #{format_index_parts(index.orders)}" if index.orders.present?
+        index_parts << "opclass: #{format_index_parts(index.opclasses)}" if index.opclasses.present?
         index_parts << "where: #{index.where.inspect}" if index.where
         index_parts << "using: #{index.using.inspect}" if !@connection.default_index_type?(index)
         index_parts << "type: #{index.type.inspect}" if index.type
@@ -239,6 +232,14 @@ HEADER
         options.map { |key, value| "#{key}: #{value.inspect}" }.join(", ")
       end
 
+      def format_index_parts(options)
+        if options.is_a?(Hash)
+          "{ #{format_options(options)} }"
+        else
+          options.inspect
+        end
+      end
+
       def remove_prefix_and_suffix(table)
         prefix = Regexp.escape(@options[:table_name_prefix].to_s)
         suffix = Regexp.escape(@options[:table_name_suffix].to_s)
diff --git a/activerecord/lib/active_record/schema_migration.rb b/activerecord/lib/active_record/schema_migration.rb
index 339a5334a8..f2d8b038fa 100644
--- a/activerecord/lib/active_record/schema_migration.rb
+++ b/activerecord/lib/active_record/schema_migration.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "scoping/default"
-require_relative "scoping/named"
+require "active_record/scoping/default"
+require "active_record/scoping/named"
 
 module ActiveRecord
   # This class is used to create a table that keeps track of which migrations
diff --git a/activerecord/lib/active_record/scoping.rb b/activerecord/lib/active_record/scoping.rb
index da585a9562..01ac56570a 100644
--- a/activerecord/lib/active_record/scoping.rb
+++ b/activerecord/lib/active_record/scoping.rb
@@ -11,23 +11,23 @@ module ActiveRecord
       include Named
     end
 
-    module ClassMethods
-      def current_scope(skip_inherited_scope = false) # :nodoc:
+    module ClassMethods # :nodoc:
+      def current_scope(skip_inherited_scope = false)
         ScopeRegistry.value_for(:current_scope, self, skip_inherited_scope)
       end
 
-      def current_scope=(scope) #:nodoc:
+      def current_scope=(scope)
         ScopeRegistry.set_value_for(:current_scope, self, scope)
       end
 
       # Collects attributes from scopes that should be applied when creating
       # an AR instance for the particular class this is called on.
-      def scope_attributes # :nodoc:
+      def scope_attributes
         all.scope_for_create
       end
 
       # Are there attributes associated with this scope?
-      def scope_attributes? # :nodoc:
+      def scope_attributes?
         current_scope
       end
     end
diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index 86ae374318..8c612df27a 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -111,7 +111,7 @@ module ActiveRecord
               # The user has defined their own default scope method, so call that
               evaluate_default_scope do
                 if scope = default_scope
-                  (base_rel ||= relation).merge(scope)
+                  (base_rel ||= relation).merge!(scope)
                 end
               end
             elsif default_scopes.any?
@@ -119,7 +119,7 @@ module ActiveRecord
               evaluate_default_scope do
                 default_scopes.inject(base_rel) do |default_scope, scope|
                   scope = scope.respond_to?(:to_proc) ? scope : scope.method(:call)
-                  default_scope.merge(base_rel.instance_exec(&scope))
+                  default_scope.merge!(base_rel.instance_exec(&scope))
                 end
               end
             end
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index 6fa096c1fe..752655aa05 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -24,8 +24,14 @@ module ActiveRecord
         # You can define a scope that applies to all finders using
         # {default_scope}[rdoc-ref:Scoping::Default::ClassMethods#default_scope].
         def all
+          current_scope = self.current_scope
+
           if current_scope
-            current_scope.clone
+            if self == current_scope.klass
+              current_scope.clone
+            else
+              relation.merge!(current_scope)
+            end
           else
             default_scoped
           end
@@ -165,6 +171,12 @@ module ActiveRecord
               "a class method with the same name."
           end
 
+          if method_defined_within?(name, Relation)
+            raise ArgumentError, "You tried to define a scope named \"#{name}\" " \
+              "on the model \"#{self.name}\", but ActiveRecord::Relation already defined " \
+              "an instance method with the same name."
+          end
+
           valid_scope_name?(name)
           extension = Module.new(&block) if block
 
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 0f3f84ca08..4657e51e6d 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -164,13 +164,12 @@ module ActiveRecord
       end
 
       def migrate
-        raise "Empty VERSION provided" if ENV["VERSION"] && ENV["VERSION"].empty?
+        check_target_version
 
         verbose = ENV["VERBOSE"] ? ENV["VERBOSE"] != "false" : true
-        version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
         scope = ENV["SCOPE"]
         verbose_was, Migration.verbose = Migration.verbose, verbose
-        Migrator.migrate(migrations_paths, version) do |migration|
+        Migrator.migrate(migrations_paths, target_version) do |migration|
           scope.blank? || scope == migration.scope
         end
         ActiveRecord::Base.clear_cache!
@@ -178,6 +177,16 @@ module ActiveRecord
         Migration.verbose = verbose_was
       end
 
+      def check_target_version
+        if target_version && !(Migration::MigrationFilenameRegexp.match?(ENV["VERSION"]) || /\A\d+\z/.match?(ENV["VERSION"]))
+          raise "Invalid format of target version: `VERSION=#{ENV['VERSION']}`"
+        end
+      end
+
+      def target_version
+        ENV["VERSION"].to_i if ENV["VERSION"] && !ENV["VERSION"].empty?
+      end
+
       def charset_current(environment = env)
         charset ActiveRecord::Base.configurations[environment]
       end
@@ -225,22 +234,22 @@ module ActiveRecord
         class_for_adapter(configuration["adapter"]).new(*arguments).structure_load(filename, structure_load_flags)
       end
 
-      def load_schema(configuration, format = ActiveRecord::Base.schema_format, file = nil) # :nodoc:
+      def load_schema(configuration, format = ActiveRecord::Base.schema_format, file = nil, environment = env) # :nodoc:
         file ||= schema_file(format)
 
+        check_schema_file(file)
+        ActiveRecord::Base.establish_connection(configuration)
+
         case format
         when :ruby
-          check_schema_file(file)
-          ActiveRecord::Base.establish_connection(configuration)
           load(file)
         when :sql
-          check_schema_file(file)
           structure_load(configuration, file)
         else
           raise ArgumentError, "unknown format #{format.inspect}"
         end
         ActiveRecord::InternalMetadata.create_table
-        ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+        ActiveRecord::InternalMetadata[:environment] = environment
       end
 
       def schema_file(format = ActiveRecord::Base.schema_format)
@@ -253,8 +262,8 @@ module ActiveRecord
       end
 
       def load_schema_current(format = ActiveRecord::Base.schema_format, file = nil, environment = env)
-        each_current_configuration(environment) { |configuration|
-          load_schema configuration, format, file
+        each_current_configuration(environment) { |configuration, configuration_environment|
+          load_schema configuration, format, file, configuration_environment
         }
         ActiveRecord::Base.establish_connection(environment.to_sym)
       end
@@ -301,9 +310,10 @@ module ActiveRecord
           environments = [environment]
           environments << "test" if environment == "development"
 
-          configurations = ActiveRecord::Base.configurations.values_at(*environments)
-          configurations.compact.each do |configuration|
-            yield configuration unless configuration["database"].blank?
+          ActiveRecord::Base.configurations.slice(*environments).each do |configuration_environment, configuration|
+            next unless configuration["database"]
+
+            yield configuration, configuration_environment
           end
         end
 
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index 84265aa9e3..e697fa6def 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -3,8 +3,6 @@
 module ActiveRecord
   module Tasks # :nodoc:
     class MySQLDatabaseTasks # :nodoc:
-      ACCESS_DENIED_ERROR = 1045
-
       delegate :connection, :establish_connection, to: ActiveRecord::Base
 
       def initialize(configuration)
@@ -21,20 +19,6 @@ module ActiveRecord
         else
           raise
         end
-      rescue error_class => error
-        if error.respond_to?(:errno) && error.errno == ACCESS_DENIED_ERROR
-          $stdout.print error.message
-          establish_connection root_configuration_without_database
-          connection.create_database configuration["database"], creation_options
-          if configuration["username"] != "root"
-            connection.execute grant_statement.gsub(/\s+/, " ").strip
-          end
-          establish_connection configuration
-        else
-          $stderr.puts error.inspect
-          $stderr.puts "Couldn't create database for #{configuration.inspect}, #{creation_options.inspect}"
-          $stderr.puts "(If you set the charset manually, make sure you have a matching collation)" if configuration["encoding"]
-        end
       end
 
       def drop
@@ -99,37 +83,6 @@ module ActiveRecord
           end
         end
 
-        def error_class
-          if configuration["adapter"].include?("jdbc")
-            require_relative "../railties/jdbcmysql_error"
-            ArJdbcMySQL::Error
-          elsif defined?(Mysql2)
-            Mysql2::Error
-          else
-            StandardError
-          end
-        end
-
-        def grant_statement
-          <<-SQL
-GRANT ALL PRIVILEGES ON `#{configuration['database']}`.*
-  TO '#{configuration['username']}'@'localhost'
-IDENTIFIED BY '#{configuration['password']}' WITH GRANT OPTION;
-          SQL
-        end
-
-        def root_configuration_without_database
-          configuration_without_database.merge(
-            "username" => "root",
-            "password" => root_password
-          )
-        end
-
-        def root_password
-          $stdout.print "Please provide the root password for your MySQL installation\n>"
-          $stdin.gets.strip
-        end
-
         def prepare_command_options
           args = {
             "host"      => "--host",
diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb
index 6761f2da25..97cba5d1c7 100644
--- a/activerecord/lib/active_record/transactions.rb
+++ b/activerecord/lib/active_record/transactions.rb
@@ -285,7 +285,7 @@ module ActiveRecord
             fire_on = Array(options[:on])
             assert_valid_transaction_action(fire_on)
             options[:if] = Array(options[:if])
-            options[:if].unshift("transaction_include_any_action?(#{fire_on})")
+            options[:if].unshift(-> { transaction_include_any_action?(fire_on) })
           end
         end
 
diff --git a/activerecord/lib/active_record/type.rb b/activerecord/lib/active_record/type.rb
index fa22df92b8..c303186ef2 100644
--- a/activerecord/lib/active_record/type.rb
+++ b/activerecord/lib/active_record/type.rb
@@ -2,21 +2,21 @@
 
 require "active_model/type"
 
-require_relative "type/internal/timezone"
+require "active_record/type/internal/timezone"
 
-require_relative "type/date"
-require_relative "type/date_time"
-require_relative "type/decimal_without_scale"
-require_relative "type/json"
-require_relative "type/time"
-require_relative "type/text"
-require_relative "type/unsigned_integer"
+require "active_record/type/date"
+require "active_record/type/date_time"
+require "active_record/type/decimal_without_scale"
+require "active_record/type/json"
+require "active_record/type/time"
+require "active_record/type/text"
+require "active_record/type/unsigned_integer"
 
-require_relative "type/serialized"
-require_relative "type/adapter_specific_registry"
+require "active_record/type/serialized"
+require "active_record/type/adapter_specific_registry"
 
-require_relative "type/type_map"
-require_relative "type/hash_lookup_type_map"
+require "active_record/type/type_map"
+require "active_record/type/hash_lookup_type_map"
 
 module ActiveRecord
   module Type
diff --git a/activerecord/lib/active_record/type_caster.rb b/activerecord/lib/active_record/type_caster.rb
index ed2e4fb79c..2e5f45fa3d 100644
--- a/activerecord/lib/active_record/type_caster.rb
+++ b/activerecord/lib/active_record/type_caster.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "type_caster/map"
-require_relative "type_caster/connection"
+require "active_record/type_caster/map"
+require "active_record/type_caster/connection"
 
 module ActiveRecord
   module TypeCaster # :nodoc:
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index 3f5c879f2f..ca27a3f0ab 100644
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -86,8 +86,8 @@ module ActiveRecord
   end
 end
 
-require_relative "validations/associated"
-require_relative "validations/uniqueness"
-require_relative "validations/presence"
-require_relative "validations/absence"
-require_relative "validations/length"
+require "active_record/validations/associated"
+require "active_record/validations/uniqueness"
+require "active_record/validations/presence"
+require "active_record/validations/absence"
+require "active_record/validations/length"
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index f4ad58c087..4c2c5dd852 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -205,9 +205,7 @@ module ActiveRecord
       #                                      | # Boom! We now have a duplicate
       #                                      | # title!
       #
-      # This could even happen if you use transactions with the 'serializable'
-      # isolation level. The best way to work around this problem is to add a unique
-      # index to the database table using
+      # The best way to work around this problem is to add a unique index to the database table using
       # {connection.add_index}[rdoc-ref:ConnectionAdapters::SchemaStatements#add_index].
       # In the rare case that a race condition occurs, the database will guarantee
       # the field's uniqueness.
diff --git a/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb b/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb.tt
index 60050e0bf8..60050e0bf8 100644
--- a/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb
+++ b/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb b/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb.tt
index 5f7201cfe1..5f7201cfe1 100644
--- a/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb b/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb.tt
index 481c70201b..481c70201b 100644
--- a/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/model/templates/model.rb b/activerecord/lib/rails/generators/active_record/model/templates/model.rb.tt
index 55dc65c8ad..55dc65c8ad 100644
--- a/activerecord/lib/rails/generators/active_record/model/templates/model.rb
+++ b/activerecord/lib/rails/generators/active_record/model/templates/model.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/model/templates/module.rb b/activerecord/lib/rails/generators/active_record/model/templates/module.rb.tt
index a3bf1c37b6..a3bf1c37b6 100644
--- a/activerecord/lib/rails/generators/active_record/model/templates/module.rb
+++ b/activerecord/lib/rails/generators/active_record/model/templates/module.rb.tt
diff --git a/activerecord/test/cases/adapters/mysql2/active_schema_test.rb b/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
index a6b83ec377..4e73c557ed 100644
--- a/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
@@ -9,7 +9,7 @@ class Mysql2ActiveSchemaTest < ActiveRecord::Mysql2TestCase
   def setup
     ActiveRecord::Base.connection.singleton_class.class_eval do
       alias_method :execute_without_stub, :execute
-      def execute(sql, name = nil) return sql end
+      def execute(sql, name = nil) sql end
     end
   end
 
diff --git a/activerecord/test/cases/adapters/mysql2/auto_increment_test.rb b/activerecord/test/cases/adapters/mysql2/auto_increment_test.rb
new file mode 100644
index 0000000000..4c67633946
--- /dev/null
+++ b/activerecord/test/cases/adapters/mysql2/auto_increment_test.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "support/schema_dumping_helper"
+
+class Mysql2AutoIncrementTest < ActiveRecord::Mysql2TestCase
+  include SchemaDumpingHelper
+
+  def setup
+    @connection = ActiveRecord::Base.connection
+  end
+
+  def teardown
+    @connection.drop_table :auto_increments, if_exists: true
+  end
+
+  def test_auto_increment_without_primary_key
+    @connection.create_table :auto_increments, id: false, force: true do |t|
+      t.integer :id, null: false, auto_increment: true
+      t.index :id
+    end
+    output = dump_table_schema("auto_increments")
+    assert_match(/t\.integer\s+"id",\s+null: false,\s+auto_increment: true$/, output)
+  end
+
+  def test_auto_increment_with_composite_primary_key
+    @connection.create_table :auto_increments, primary_key: [:id, :created_at], force: true do |t|
+      t.integer :id, null: false, auto_increment: true
+      t.datetime :created_at, null: false
+    end
+    output = dump_table_schema("auto_increments")
+    assert_match(/t\.integer\s+"id",\s+null: false,\s+auto_increment: true$/, output)
+  end
+end
diff --git a/activerecord/test/cases/adapters/mysql2/connection_test.rb b/activerecord/test/cases/adapters/mysql2/connection_test.rb
index 9d81d506a0..13b4096671 100644
--- a/activerecord/test/cases/adapters/mysql2/connection_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/connection_test.rb
@@ -65,18 +65,6 @@ class Mysql2ConnectionTest < ActiveRecord::Mysql2TestCase
     assert @connection.active?
   end
 
-  def test_verify_with_args_is_deprecated
-    assert_deprecated do
-      @connection.verify!(option: true)
-    end
-    assert_deprecated do
-      @connection.verify!([])
-    end
-    assert_deprecated do
-      @connection.verify!({})
-    end
-  end
-
   def test_execute_after_disconnect
     @connection.disconnect!
 
@@ -186,10 +174,10 @@ class Mysql2ConnectionTest < ActiveRecord::Mysql2TestCase
     assert_equal "SCHEMA", @subscriber.logged[0][1]
   end
 
-  def test_logs_name_rename_column_sql
+  def test_logs_name_rename_column_for_alter
     @connection.execute "CREATE TABLE `bar_baz` (`foo` varchar(255))"
     @subscriber.logged.clear
-    @connection.send(:rename_column_sql, "bar_baz", "foo", "foo2")
+    @connection.send(:rename_column_for_alter, "bar_baz", "foo", "foo2")
     assert_equal "SCHEMA", @subscriber.logged[0][1]
   ensure
     @connection.execute "DROP TABLE `bar_baz`"
diff --git a/activerecord/test/cases/adapters/mysql2/explain_test.rb b/activerecord/test/cases/adapters/mysql2/explain_test.rb
index 2736f7cf0e..b8e778f0b0 100644
--- a/activerecord/test/cases/adapters/mysql2/explain_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/explain_test.rb
@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "models/developer"
-require "models/computer"
+require "models/author"
+require "models/post"
 
 class Mysql2ExplainTest < ActiveRecord::Mysql2TestCase
-  fixtures :developers
+  fixtures :authors
 
   def test_explain_for_one_query
-    explain = Developer.where(id: 1).explain
-    assert_match %(EXPLAIN for: SELECT `developers`.* FROM `developers` WHERE `developers`.`id` = 1), explain
-    assert_match %r(developers |.* const), explain
+    explain = Author.where(id: 1).explain
+    assert_match %(EXPLAIN for: SELECT `authors`.* FROM `authors` WHERE `authors`.`id` = 1), explain
+    assert_match %r(authors |.* const), explain
   end
 
   def test_explain_with_eager_loading
-    explain = Developer.where(id: 1).includes(:audit_logs).explain
-    assert_match %(EXPLAIN for: SELECT `developers`.* FROM `developers` WHERE `developers`.`id` = 1), explain
-    assert_match %r(developers |.* const), explain
-    assert_match %(EXPLAIN for: SELECT `audit_logs`.* FROM `audit_logs` WHERE `audit_logs`.`developer_id` = 1), explain
-    assert_match %r(audit_logs |.* ALL), explain
+    explain = Author.where(id: 1).includes(:posts).explain
+    assert_match %(EXPLAIN for: SELECT `authors`.* FROM `authors` WHERE `authors`.`id` = 1), explain
+    assert_match %r(authors |.* const), explain
+    assert_match %(EXPLAIN for: SELECT `posts`.* FROM `posts` WHERE `posts`.`author_id` = 1), explain
+    assert_match %r(posts |.* ALL), explain
   end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/transaction_test.rb b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
index 25d9f69a89..cb183cc54c 100644
--- a/activerecord/test/cases/adapters/mysql2/transaction_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
@@ -60,9 +60,87 @@ module ActiveRecord
       end
     end
 
-    test "raises TransactionTimeout when mysql raises ER_LOCK_WAIT_TIMEOUT" do
-      assert_raises(ActiveRecord::TransactionTimeout) do
-        ActiveRecord::Base.connection.execute("SIGNAL SQLSTATE 'HY000' SET MESSAGE_TEXT = 'Testing error', MYSQL_ERRNO = 1205;")
+    test "raises LockWaitTimeout when lock wait timeout exceeded" do
+      assert_raises(ActiveRecord::LockWaitTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET innodb_lock_wait_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET innodb_lock_wait_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises StatementTimeout when statement timeout exceeded" do
+      skip unless ActiveRecord::Base.connection.show_variable("max_execution_time")
+      assert_raises(ActiveRecord::StatementTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET max_execution_time = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET max_execution_time = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises QueryCanceled when canceling statement due to user request" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch.count_down
+            sleep(0.5)
+            conn = Sample.connection
+            pid = conn.query_value("SELECT id FROM information_schema.processlist WHERE info LIKE '% FOR UPDATE'")
+            conn.execute("KILL QUERY #{pid}")
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch.wait
+            Sample.lock.find(s.id)
+          end
+        ensure
+          thread.join
+        end
       end
     end
   end
diff --git a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
index 9929237546..99c53dadeb 100644
--- a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
@@ -59,6 +59,9 @@ class PostgresqlActiveSchemaTest < ActiveRecord::PostgreSQLTestCase
       assert_equal expected, add_index(:people, "lower(last_name)", using: type, unique: true)
     end
 
+    expected = %(CREATE  INDEX  "index_people_on_last_name" ON "people" USING gist ("last_name" bpchar_pattern_ops))
+    assert_equal expected, add_index(:people, :last_name, using: :gist, opclass: { last_name: :bpchar_pattern_ops })
+
     assert_raise ArgumentError do
       add_index(:people, :last_name, algorithm: :copy)
     end
diff --git a/activerecord/test/cases/adapters/postgresql/citext_test.rb b/activerecord/test/cases/adapters/postgresql/citext_test.rb
index 050614cade..a25f102bad 100644
--- a/activerecord/test/cases/adapters/postgresql/citext_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/citext_test.rb
@@ -3,78 +3,76 @@
 require "cases/helper"
 require "support/schema_dumping_helper"
 
-if ActiveRecord::Base.connection.supports_extensions?
-  class PostgresqlCitextTest < ActiveRecord::PostgreSQLTestCase
-    include SchemaDumpingHelper
-    class Citext < ActiveRecord::Base
-      self.table_name = "citexts"
-    end
-
-    def setup
-      @connection = ActiveRecord::Base.connection
+class PostgresqlCitextTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+  class Citext < ActiveRecord::Base
+    self.table_name = "citexts"
+  end
 
-      enable_extension!("citext", @connection)
+  def setup
+    @connection = ActiveRecord::Base.connection
 
-      @connection.create_table("citexts") do |t|
-        t.citext "cival"
-      end
-    end
+    enable_extension!("citext", @connection)
 
-    teardown do
-      @connection.drop_table "citexts", if_exists: true
-      disable_extension!("citext", @connection)
+    @connection.create_table("citexts") do |t|
+      t.citext "cival"
     end
+  end
 
-    def test_citext_enabled
-      assert @connection.extension_enabled?("citext")
-    end
+  teardown do
+    @connection.drop_table "citexts", if_exists: true
+    disable_extension!("citext", @connection)
+  end
 
-    def test_column
-      column = Citext.columns_hash["cival"]
-      assert_equal :citext, column.type
-      assert_equal "citext", column.sql_type
-      assert_not column.array?
+  def test_citext_enabled
+    assert @connection.extension_enabled?("citext")
+  end
 
-      type = Citext.type_for_attribute("cival")
-      assert_not type.binary?
-    end
+  def test_column
+    column = Citext.columns_hash["cival"]
+    assert_equal :citext, column.type
+    assert_equal "citext", column.sql_type
+    assert_not column.array?
 
-    def test_change_table_supports_json
-      @connection.transaction do
-        @connection.change_table("citexts") do |t|
-          t.citext "username"
-        end
-        Citext.reset_column_information
-        column = Citext.columns_hash["username"]
-        assert_equal :citext, column.type
+    type = Citext.type_for_attribute("cival")
+    assert_not type.binary?
+  end
 
-        raise ActiveRecord::Rollback # reset the schema change
+  def test_change_table_supports_json
+    @connection.transaction do
+      @connection.change_table("citexts") do |t|
+        t.citext "username"
       end
-    ensure
       Citext.reset_column_information
+      column = Citext.columns_hash["username"]
+      assert_equal :citext, column.type
+
+      raise ActiveRecord::Rollback # reset the schema change
     end
+  ensure
+    Citext.reset_column_information
+  end
 
-    def test_write
-      x = Citext.new(cival: "Some CI Text")
-      x.save!
-      citext = Citext.first
-      assert_equal "Some CI Text", citext.cival
+  def test_write
+    x = Citext.new(cival: "Some CI Text")
+    x.save!
+    citext = Citext.first
+    assert_equal "Some CI Text", citext.cival
 
-      citext.cival = "Some NEW CI Text"
-      citext.save!
+    citext.cival = "Some NEW CI Text"
+    citext.save!
 
-      assert_equal "Some NEW CI Text", citext.reload.cival
-    end
+    assert_equal "Some NEW CI Text", citext.reload.cival
+  end
 
-    def test_select_case_insensitive
-      @connection.execute "insert into citexts (cival) values('Cased Text')"
-      x = Citext.where(cival: "cased text").first
-      assert_equal "Cased Text", x.cival
-    end
+  def test_select_case_insensitive
+    @connection.execute "insert into citexts (cival) values('Cased Text')"
+    x = Citext.where(cival: "cased text").first
+    assert_equal "Cased Text", x.cival
+  end
 
-    def test_schema_dump_with_shorthand
-      output = dump_table_schema("citexts")
-      assert_match %r[t\.citext "cival"], output
-    end
+  def test_schema_dump_with_shorthand
+    output = dump_table_schema("citexts")
+    assert_match %r[t\.citext "cival"], output
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index 2bb217a8b1..81358b8fc4 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -103,7 +103,7 @@ module ActiveRecord
     end
 
     def test_indexes_logs_name
-      assert_deprecated { @connection.indexes("items", "hello") }
+      @connection.indexes("items")
       assert_equal "SCHEMA", @subscriber.logged[0][1]
     end
 
diff --git a/activerecord/test/cases/adapters/postgresql/explain_test.rb b/activerecord/test/cases/adapters/postgresql/explain_test.rb
index 16fec94ede..be525383e9 100644
--- a/activerecord/test/cases/adapters/postgresql/explain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/explain_test.rb
@@ -1,22 +1,22 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "models/developer"
-require "models/computer"
+require "models/author"
+require "models/post"
 
 class PostgreSQLExplainTest < ActiveRecord::PostgreSQLTestCase
-  fixtures :developers
+  fixtures :authors
 
   def test_explain_for_one_query
-    explain = Developer.where(id: 1).explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
+    explain = Author.where(id: 1).explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
     assert_match %(QUERY PLAN), explain
   end
 
   def test_explain_with_eager_loading
-    explain = Developer.where(id: 1).includes(:audit_logs).explain
+    explain = Author.where(id: 1).includes(:posts).explain
     assert_match %(QUERY PLAN), explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
-    assert_match %r(EXPLAIN for: SELECT "audit_logs"\.\* FROM "audit_logs" WHERE "audit_logs"\."developer_id" = (?:\$1 \[\["developer_id", 1\]\]|1)), explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
+    assert_match %r(EXPLAIN for: SELECT "posts"\.\* FROM "posts" WHERE "posts"\."author_id" = (?:\$1 \[\["author_id", 1\]\]|1)), explain
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb b/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
index e589e3ab1b..df97ab11e7 100644
--- a/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
@@ -22,10 +22,6 @@ class PostgresqlExtensionMigrationTest < ActiveRecord::PostgreSQLTestCase
 
     @connection = ActiveRecord::Base.connection
 
-    unless @connection.supports_extensions?
-      return skip("no extension support")
-    end
-
     @old_schema_migration_table_name = ActiveRecord::SchemaMigration.table_name
     @old_table_name_prefix = ActiveRecord::Base.table_name_prefix
     @old_table_name_suffix = ActiveRecord::Base.table_name_suffix
diff --git a/activerecord/test/cases/adapters/postgresql/hstore_test.rb b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
index 97a8a257c5..f09e34b5f2 100644
--- a/activerecord/test/cases/adapters/postgresql/hstore_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
@@ -3,378 +3,376 @@
 require "cases/helper"
 require "support/schema_dumping_helper"
 
-if ActiveRecord::Base.connection.supports_extensions?
-  class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
-    include SchemaDumpingHelper
-    class Hstore < ActiveRecord::Base
-      self.table_name = "hstores"
+class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+  class Hstore < ActiveRecord::Base
+    self.table_name = "hstores"
 
-      store_accessor :settings, :language, :timezone
-    end
+    store_accessor :settings, :language, :timezone
+  end
 
-    class FakeParameters
-      def to_unsafe_h
-        { "hi" => "hi" }
-      end
+  class FakeParameters
+    def to_unsafe_h
+      { "hi" => "hi" }
     end
+  end
 
-    def setup
-      @connection = ActiveRecord::Base.connection
+  def setup
+    @connection = ActiveRecord::Base.connection
 
-      enable_extension!("hstore", @connection)
+    enable_extension!("hstore", @connection)
 
-      @connection.transaction do
-        @connection.create_table("hstores") do |t|
-          t.hstore "tags", default: ""
-          t.hstore "payload", array: true
-          t.hstore "settings"
-        end
+    @connection.transaction do
+      @connection.create_table("hstores") do |t|
+        t.hstore "tags", default: ""
+        t.hstore "payload", array: true
+        t.hstore "settings"
       end
-      Hstore.reset_column_information
-      @column = Hstore.columns_hash["tags"]
-      @type = Hstore.type_for_attribute("tags")
-    end
-
-    teardown do
-      @connection.drop_table "hstores", if_exists: true
-      disable_extension!("hstore", @connection)
     end
+    Hstore.reset_column_information
+    @column = Hstore.columns_hash["tags"]
+    @type = Hstore.type_for_attribute("tags")
+  end
 
-    def test_hstore_included_in_extensions
-      assert @connection.respond_to?(:extensions), "connection should have a list of extensions"
-      assert_includes @connection.extensions, "hstore", "extension list should include hstore"
-    end
+  teardown do
+    @connection.drop_table "hstores", if_exists: true
+    disable_extension!("hstore", @connection)
+  end
 
-    def test_disable_enable_hstore
-      assert @connection.extension_enabled?("hstore")
-      @connection.disable_extension "hstore"
-      assert_not @connection.extension_enabled?("hstore")
-      @connection.enable_extension "hstore"
-      assert @connection.extension_enabled?("hstore")
-    ensure
-      # Restore column(s) dropped by `drop extension hstore cascade;`
-      load_schema
-    end
+  def test_hstore_included_in_extensions
+    assert @connection.respond_to?(:extensions), "connection should have a list of extensions"
+    assert_includes @connection.extensions, "hstore", "extension list should include hstore"
+  end
 
-    def test_column
-      assert_equal :hstore, @column.type
-      assert_equal "hstore", @column.sql_type
-      assert_not @column.array?
+  def test_disable_enable_hstore
+    assert @connection.extension_enabled?("hstore")
+    @connection.disable_extension "hstore"
+    assert_not @connection.extension_enabled?("hstore")
+    @connection.enable_extension "hstore"
+    assert @connection.extension_enabled?("hstore")
+  ensure
+    # Restore column(s) dropped by `drop extension hstore cascade;`
+    load_schema
+  end
 
-      assert_not @type.binary?
-    end
+  def test_column
+    assert_equal :hstore, @column.type
+    assert_equal "hstore", @column.sql_type
+    assert_not @column.array?
 
-    def test_default
-      @connection.add_column "hstores", "permissions", :hstore, default: '"users"=>"read", "articles"=>"write"'
-      Hstore.reset_column_information
+    assert_not @type.binary?
+  end
 
-      assert_equal({ "users" => "read", "articles" => "write" }, Hstore.column_defaults["permissions"])
-      assert_equal({ "users" => "read", "articles" => "write" }, Hstore.new.permissions)
-    ensure
-      Hstore.reset_column_information
-    end
+  def test_default
+    @connection.add_column "hstores", "permissions", :hstore, default: '"users"=>"read", "articles"=>"write"'
+    Hstore.reset_column_information
 
-    def test_change_table_supports_hstore
-      @connection.transaction do
-        @connection.change_table("hstores") do |t|
-          t.hstore "users", default: ""
-        end
-        Hstore.reset_column_information
-        column = Hstore.columns_hash["users"]
-        assert_equal :hstore, column.type
+    assert_equal({ "users" => "read", "articles" => "write" }, Hstore.column_defaults["permissions"])
+    assert_equal({ "users" => "read", "articles" => "write" }, Hstore.new.permissions)
+  ensure
+    Hstore.reset_column_information
+  end
 
-        raise ActiveRecord::Rollback # reset the schema change
+  def test_change_table_supports_hstore
+    @connection.transaction do
+      @connection.change_table("hstores") do |t|
+        t.hstore "users", default: ""
       end
-    ensure
       Hstore.reset_column_information
+      column = Hstore.columns_hash["users"]
+      assert_equal :hstore, column.type
+
+      raise ActiveRecord::Rollback # reset the schema change
     end
+  ensure
+    Hstore.reset_column_information
+  end
 
-    def test_hstore_migration
-      hstore_migration = Class.new(ActiveRecord::Migration::Current) do
-        def change
-          change_table("hstores") do |t|
-            t.hstore :keys
-          end
+  def test_hstore_migration
+    hstore_migration = Class.new(ActiveRecord::Migration::Current) do
+      def change
+        change_table("hstores") do |t|
+          t.hstore :keys
         end
       end
-
-      hstore_migration.new.suppress_messages do
-        hstore_migration.migrate(:up)
-        assert_includes @connection.columns(:hstores).map(&:name), "keys"
-        hstore_migration.migrate(:down)
-        assert_not_includes @connection.columns(:hstores).map(&:name), "keys"
-      end
     end
 
-    def test_cast_value_on_write
-      x = Hstore.new tags: { "bool" => true, "number" => 5 }
-      assert_equal({ "bool" => true, "number" => 5 }, x.tags_before_type_cast)
-      assert_equal({ "bool" => "true", "number" => "5" }, x.tags)
-      x.save
-      assert_equal({ "bool" => "true", "number" => "5" }, x.reload.tags)
+    hstore_migration.new.suppress_messages do
+      hstore_migration.migrate(:up)
+      assert_includes @connection.columns(:hstores).map(&:name), "keys"
+      hstore_migration.migrate(:down)
+      assert_not_includes @connection.columns(:hstores).map(&:name), "keys"
     end
+  end
 
-    def test_type_cast_hstore
-      assert_equal({ "1" => "2" }, @type.deserialize("\"1\"=>\"2\""))
-      assert_equal({}, @type.deserialize(""))
-      assert_equal({ "key" => nil }, @type.deserialize("key => NULL"))
-      assert_equal({ "c" => "}", '"a"' => 'b "a b' }, @type.deserialize(%q(c=>"}", "\"a\""=>"b \"a b")))
-    end
+  def test_cast_value_on_write
+    x = Hstore.new tags: { "bool" => true, "number" => 5 }
+    assert_equal({ "bool" => true, "number" => 5 }, x.tags_before_type_cast)
+    assert_equal({ "bool" => "true", "number" => "5" }, x.tags)
+    x.save
+    assert_equal({ "bool" => "true", "number" => "5" }, x.reload.tags)
+  end
 
-    def test_with_store_accessors
-      x = Hstore.new(language: "fr", timezone: "GMT")
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+  def test_type_cast_hstore
+    assert_equal({ "1" => "2" }, @type.deserialize("\"1\"=>\"2\""))
+    assert_equal({}, @type.deserialize(""))
+    assert_equal({ "key" => nil }, @type.deserialize("key => NULL"))
+    assert_equal({ "c" => "}", '"a"' => 'b "a b' }, @type.deserialize(%q(c=>"}", "\"a\""=>"b \"a b")))
+  end
 
-      x.save!
-      x = Hstore.first
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+  def test_with_store_accessors
+    x = Hstore.new(language: "fr", timezone: "GMT")
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-      x.language = "de"
-      x.save!
+    x.save!
+    x = Hstore.first
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-      x = Hstore.first
-      assert_equal "de", x.language
-      assert_equal "GMT", x.timezone
-    end
+    x.language = "de"
+    x.save!
 
-    def test_duplication_with_store_accessors
-      x = Hstore.new(language: "fr", timezone: "GMT")
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+    x = Hstore.first
+    assert_equal "de", x.language
+    assert_equal "GMT", x.timezone
+  end
 
-      y = x.dup
-      assert_equal "fr", y.language
-      assert_equal "GMT", y.timezone
-    end
+  def test_duplication_with_store_accessors
+    x = Hstore.new(language: "fr", timezone: "GMT")
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-    def test_yaml_round_trip_with_store_accessors
-      x = Hstore.new(language: "fr", timezone: "GMT")
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+    y = x.dup
+    assert_equal "fr", y.language
+    assert_equal "GMT", y.timezone
+  end
 
-      y = YAML.load(YAML.dump(x))
-      assert_equal "fr", y.language
-      assert_equal "GMT", y.timezone
-    end
+  def test_yaml_round_trip_with_store_accessors
+    x = Hstore.new(language: "fr", timezone: "GMT")
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-    def test_changes_in_place
-      hstore = Hstore.create!(settings: { "one" => "two" })
-      hstore.settings["three"] = "four"
-      hstore.save!
-      hstore.reload
+    y = YAML.load(YAML.dump(x))
+    assert_equal "fr", y.language
+    assert_equal "GMT", y.timezone
+  end
 
-      assert_equal "four", hstore.settings["three"]
-      assert_not hstore.changed?
-    end
+  def test_changes_in_place
+    hstore = Hstore.create!(settings: { "one" => "two" })
+    hstore.settings["three"] = "four"
+    hstore.save!
+    hstore.reload
 
-    def test_dirty_from_user_equal
-      settings = { "alongkey" => "anything", "key" => "value" }
-      hstore = Hstore.create!(settings: settings)
+    assert_equal "four", hstore.settings["three"]
+    assert_not hstore.changed?
+  end
 
-      hstore.settings = { "key" => "value", "alongkey" => "anything" }
-      assert_equal settings, hstore.settings
-      refute hstore.changed?
-    end
+  def test_dirty_from_user_equal
+    settings = { "alongkey" => "anything", "key" => "value" }
+    hstore = Hstore.create!(settings: settings)
 
-    def test_hstore_dirty_from_database_equal
-      settings = { "alongkey" => "anything", "key" => "value" }
-      hstore = Hstore.create!(settings: settings)
-      hstore.reload
+    hstore.settings = { "key" => "value", "alongkey" => "anything" }
+    assert_equal settings, hstore.settings
+    refute hstore.changed?
+  end
 
-      assert_equal settings, hstore.settings
-      hstore.settings = settings
-      refute hstore.changed?
-    end
+  def test_hstore_dirty_from_database_equal
+    settings = { "alongkey" => "anything", "key" => "value" }
+    hstore = Hstore.create!(settings: settings)
+    hstore.reload
 
-    def test_gen1
-      assert_equal('" "=>""', @type.serialize(" " => ""))
-    end
+    assert_equal settings, hstore.settings
+    hstore.settings = settings
+    refute hstore.changed?
+  end
 
-    def test_gen2
-      assert_equal('","=>""', @type.serialize("," => ""))
-    end
+  def test_gen1
+    assert_equal('" "=>""', @type.serialize(" " => ""))
+  end
 
-    def test_gen3
-      assert_equal('"="=>""', @type.serialize("=" => ""))
-    end
+  def test_gen2
+    assert_equal('","=>""', @type.serialize("," => ""))
+  end
 
-    def test_gen4
-      assert_equal('">"=>""', @type.serialize(">" => ""))
-    end
+  def test_gen3
+    assert_equal('"="=>""', @type.serialize("=" => ""))
+  end
 
-    def test_parse1
-      assert_equal({ "a" => nil, "b" => nil, "c" => "NuLl", "null" => "c" }, @type.deserialize('a=>null,b=>NuLl,c=>"NuLl",null=>c'))
-    end
+  def test_gen4
+    assert_equal('">"=>""', @type.serialize(">" => ""))
+  end
 
-    def test_parse2
-      assert_equal({ " " => " " },  @type.deserialize("\\ =>\\ "))
-    end
+  def test_parse1
+    assert_equal({ "a" => nil, "b" => nil, "c" => "NuLl", "null" => "c" }, @type.deserialize('a=>null,b=>NuLl,c=>"NuLl",null=>c'))
+  end
 
-    def test_parse3
-      assert_equal({ "=" => ">" },  @type.deserialize("==>>"))
-    end
+  def test_parse2
+    assert_equal({ " " => " " },  @type.deserialize("\\ =>\\ "))
+  end
 
-    def test_parse4
-      assert_equal({ "=a" => "q=w" },   @type.deserialize('\=a=>q=w'))
-    end
+  def test_parse3
+    assert_equal({ "=" => ">" },  @type.deserialize("==>>"))
+  end
 
-    def test_parse5
-      assert_equal({ "=a" => "q=w" },   @type.deserialize('"=a"=>q\=w'))
-    end
+  def test_parse4
+    assert_equal({ "=a" => "q=w" },   @type.deserialize('\=a=>q=w'))
+  end
 
-    def test_parse6
-      assert_equal({ "\"a" => "q>w" },  @type.deserialize('"\"a"=>q>w'))
-    end
+  def test_parse5
+    assert_equal({ "=a" => "q=w" },   @type.deserialize('"=a"=>q\=w'))
+  end
 
-    def test_parse7
-      assert_equal({ "\"a" => "q\"w" }, @type.deserialize('\"a=>q"w'))
-    end
+  def test_parse6
+    assert_equal({ "\"a" => "q>w" },  @type.deserialize('"\"a"=>q>w'))
+  end
 
-    def test_rewrite
-      @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
-      x = Hstore.first
-      x.tags = { '"a\'' => "b" }
-      assert x.save!
-    end
+  def test_parse7
+    assert_equal({ "\"a" => "q\"w" }, @type.deserialize('\"a=>q"w'))
+  end
 
-    def test_select
-      @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
-      x = Hstore.first
-      assert_equal({ "1" => "2" }, x.tags)
-    end
+  def test_rewrite
+    @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
+    x = Hstore.first
+    x.tags = { '"a\'' => "b" }
+    assert x.save!
+  end
 
-    def test_array_cycle
-      assert_array_cycle([{ "AA" => "BB", "CC" => "DD" }, { "AA" => nil }])
-    end
+  def test_select
+    @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
+    x = Hstore.first
+    assert_equal({ "1" => "2" }, x.tags)
+  end
 
-    def test_array_strings_with_quotes
-      assert_array_cycle([{ "this has" => 'some "s that need to be escaped"' }])
-    end
+  def test_array_cycle
+    assert_array_cycle([{ "AA" => "BB", "CC" => "DD" }, { "AA" => nil }])
+  end
 
-    def test_array_strings_with_commas
-      assert_array_cycle([{ "this,has" => "many,values" }])
-    end
+  def test_array_strings_with_quotes
+    assert_array_cycle([{ "this has" => 'some "s that need to be escaped"' }])
+  end
 
-    def test_array_strings_with_array_delimiters
-      assert_array_cycle(["{" => "}"])
-    end
+  def test_array_strings_with_commas
+    assert_array_cycle([{ "this,has" => "many,values" }])
+  end
 
-    def test_array_strings_with_null_strings
-      assert_array_cycle([{ "NULL" => "NULL" }])
-    end
+  def test_array_strings_with_array_delimiters
+    assert_array_cycle(["{" => "}"])
+  end
 
-    def test_contains_nils
-      assert_array_cycle([{ "NULL" => nil }])
-    end
+  def test_array_strings_with_null_strings
+    assert_array_cycle([{ "NULL" => "NULL" }])
+  end
 
-    def test_select_multikey
-      @connection.execute "insert into hstores (tags) VALUES ('1=>2,2=>3')"
-      x = Hstore.first
-      assert_equal({ "1" => "2", "2" => "3" }, x.tags)
-    end
+  def test_contains_nils
+    assert_array_cycle([{ "NULL" => nil }])
+  end
 
-    def test_create
-      assert_cycle("a" => "b", "1" => "2")
-    end
+  def test_select_multikey
+    @connection.execute "insert into hstores (tags) VALUES ('1=>2,2=>3')"
+    x = Hstore.first
+    assert_equal({ "1" => "2", "2" => "3" }, x.tags)
+  end
 
-    def test_nil
-      assert_cycle("a" => nil)
-    end
+  def test_create
+    assert_cycle("a" => "b", "1" => "2")
+  end
 
-    def test_quotes
-      assert_cycle("a" => 'b"ar', '1"foo' => "2")
-    end
+  def test_nil
+    assert_cycle("a" => nil)
+  end
 
-    def test_whitespace
-      assert_cycle("a b" => "b ar", '1"foo' => "2")
-    end
+  def test_quotes
+    assert_cycle("a" => 'b"ar', '1"foo' => "2")
+  end
 
-    def test_backslash
-      assert_cycle('a\\b' => 'b\\ar', '1"foo' => "2")
-    end
+  def test_whitespace
+    assert_cycle("a b" => "b ar", '1"foo' => "2")
+  end
 
-    def test_comma
-      assert_cycle("a, b" => "bar", '1"foo' => "2")
-    end
+  def test_backslash
+    assert_cycle('a\\b' => 'b\\ar', '1"foo' => "2")
+  end
 
-    def test_arrow
-      assert_cycle("a=>b" => "bar", '1"foo' => "2")
-    end
+  def test_comma
+    assert_cycle("a, b" => "bar", '1"foo' => "2")
+  end
 
-    def test_quoting_special_characters
-      assert_cycle("ca" => "cà", "ac" => "àc")
-    end
+  def test_arrow
+    assert_cycle("a=>b" => "bar", '1"foo' => "2")
+  end
 
-    def test_multiline
-      assert_cycle("a\nb" => "c\nd")
-    end
+  def test_quoting_special_characters
+    assert_cycle("ca" => "cà", "ac" => "àc")
+  end
 
-    class TagCollection
-      def initialize(hash); @hash = hash end
-      def to_hash; @hash end
-      def self.load(hash); new(hash) end
-      def self.dump(object); object.to_hash end
-    end
+  def test_multiline
+    assert_cycle("a\nb" => "c\nd")
+  end
 
-    class HstoreWithSerialize < Hstore
-      serialize :tags, TagCollection
-    end
+  class TagCollection
+    def initialize(hash); @hash = hash end
+    def to_hash; @hash end
+    def self.load(hash); new(hash) end
+    def self.dump(object); object.to_hash end
+  end
 
-    def test_hstore_with_serialized_attributes
-      HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
-      record = HstoreWithSerialize.first
-      assert_instance_of TagCollection, record.tags
-      assert_equal({ "one" => "two" }, record.tags.to_hash)
-      record.tags = TagCollection.new("three" => "four")
-      record.save!
-      assert_equal({ "three" => "four" }, HstoreWithSerialize.first.tags.to_hash)
-    end
+  class HstoreWithSerialize < Hstore
+    serialize :tags, TagCollection
+  end
 
-    def test_clone_hstore_with_serialized_attributes
-      HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
-      record = HstoreWithSerialize.first
-      dupe = record.dup
-      assert_equal({ "one" => "two" }, dupe.tags.to_hash)
-    end
+  def test_hstore_with_serialized_attributes
+    HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
+    record = HstoreWithSerialize.first
+    assert_instance_of TagCollection, record.tags
+    assert_equal({ "one" => "two" }, record.tags.to_hash)
+    record.tags = TagCollection.new("three" => "four")
+    record.save!
+    assert_equal({ "three" => "four" }, HstoreWithSerialize.first.tags.to_hash)
+  end
 
-    def test_schema_dump_with_shorthand
-      output = dump_table_schema("hstores")
-      assert_match %r[t\.hstore "tags",\s+default: {}], output
-    end
+  def test_clone_hstore_with_serialized_attributes
+    HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
+    record = HstoreWithSerialize.first
+    dupe = record.dup
+    assert_equal({ "one" => "two" }, dupe.tags.to_hash)
+  end
+
+  def test_schema_dump_with_shorthand
+    output = dump_table_schema("hstores")
+    assert_match %r[t\.hstore "tags",\s+default: {}], output
+  end
+
+  def test_supports_to_unsafe_h_values
+    assert_equal("\"hi\"=>\"hi\"", @type.serialize(FakeParameters.new))
+  end
 
-    def test_supports_to_unsafe_h_values
-      assert_equal("\"hi\"=>\"hi\"", @type.serialize(FakeParameters.new))
+  private
+    def assert_array_cycle(array)
+      # test creation
+      x = Hstore.create!(payload: array)
+      x.reload
+      assert_equal(array, x.payload)
+
+      # test updating
+      x = Hstore.create!(payload: [])
+      x.payload = array
+      x.save!
+      x.reload
+      assert_equal(array, x.payload)
     end
 
-    private
-      def assert_array_cycle(array)
-        # test creation
-        x = Hstore.create!(payload: array)
-        x.reload
-        assert_equal(array, x.payload)
-
-        # test updating
-        x = Hstore.create!(payload: [])
-        x.payload = array
-        x.save!
-        x.reload
-        assert_equal(array, x.payload)
-      end
+    def assert_cycle(hash)
+      # test creation
+      x = Hstore.create!(tags: hash)
+      x.reload
+      assert_equal(hash, x.tags)
 
-      def assert_cycle(hash)
-        # test creation
-        x = Hstore.create!(tags: hash)
-        x.reload
-        assert_equal(hash, x.tags)
-
-        # test updating
-        x = Hstore.create!(tags: {})
-        x.tags = hash
-        x.save!
-        x.reload
-        assert_equal(hash, x.tags)
-      end
-  end
+      # test updating
+      x = Hstore.create!(tags: {})
+      x.tags = hash
+      x.save!
+      x.reload
+      assert_equal(hash, x.tags)
+    end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index f199519d86..1951230c8a 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -248,12 +248,12 @@ module ActiveRecord
 
       def test_index_with_opclass
         with_example_table do
-          @connection.add_index "ex", "data varchar_pattern_ops"
-          index = @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data_varchar_pattern_ops" }
-          assert_equal "data varchar_pattern_ops", index.columns
+          @connection.add_index "ex", "data", opclass: "varchar_pattern_ops"
+          index = @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data" }
+          assert_equal ["data"], index.columns
 
-          @connection.remove_index "ex", "data varchar_pattern_ops"
-          assert_not @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data_varchar_pattern_ops" }
+          @connection.remove_index "ex", "data"
+          assert_not @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data" }
         end
       end
 
diff --git a/activerecord/test/cases/adapters/postgresql/range_test.rb b/activerecord/test/cases/adapters/postgresql/range_test.rb
index b4a776d04d..a75fdef698 100644
--- a/activerecord/test/cases/adapters/postgresql/range_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/range_test.rb
@@ -232,6 +232,57 @@ _SQL
       end
     end
 
+    def test_create_tstzrange_preserve_usec
+      tstzrange = Time.parse("2010-01-01 14:30:00.670277 +0100")...Time.parse("2011-02-02 14:30:00.745125 CDT")
+      round_trip(@new_range, :tstz_range, tstzrange)
+      assert_equal @new_range.tstz_range, tstzrange
+      assert_equal @new_range.tstz_range, Time.parse("2010-01-01 13:30:00.670277 UTC")...Time.parse("2011-02-02 19:30:00.745125 UTC")
+    end
+
+    def test_update_tstzrange_preserve_usec
+      assert_equal_round_trip(@first_range, :tstz_range,
+                              Time.parse("2010-01-01 14:30:00.245124 CDT")...Time.parse("2011-02-02 14:30:00.451274 CET"))
+      assert_nil_round_trip(@first_range, :tstz_range,
+                            Time.parse("2010-01-01 14:30:00.245124 +0100")...Time.parse("2010-01-01 13:30:00.245124 +0000"))
+    end
+
+    def test_create_tsrange_preseve_usec
+      tz = ::ActiveRecord::Base.default_timezone
+      assert_equal_round_trip(@new_range, :ts_range,
+                              Time.send(tz, 2010, 1, 1, 14, 30, 0, 125435)...Time.send(tz, 2011, 2, 2, 14, 30, 0, 225435))
+    end
+
+    def test_update_tsrange_preserve_usec
+      tz = ::ActiveRecord::Base.default_timezone
+      assert_equal_round_trip(@first_range, :ts_range,
+                              Time.send(tz, 2010, 1, 1, 14, 30, 0, 142432)...Time.send(tz, 2011, 2, 2, 14, 30, 0, 224242))
+      assert_nil_round_trip(@first_range, :ts_range,
+                            Time.send(tz, 2010, 1, 1, 14, 30, 0, 142432)...Time.send(tz, 2010, 1, 1, 14, 30, 0, 142432))
+    end
+
+    def test_timezone_awareness_tsrange_preserve_usec
+      tz = "Pacific Time (US & Canada)"
+
+      in_time_zone tz do
+        PostgresqlRange.reset_column_information
+        time_string = "2017-09-26 07:30:59.132451 -0700"
+        time = Time.zone.parse(time_string)
+        assert time.usec > 0
+
+        record = PostgresqlRange.new(ts_range: time_string..time_string)
+        assert_equal time..time, record.ts_range
+        assert_equal ActiveSupport::TimeZone[tz], record.ts_range.begin.time_zone
+        assert_equal time.usec, record.ts_range.begin.usec
+
+        record.save!
+        record.reload
+
+        assert_equal time..time, record.ts_range
+        assert_equal ActiveSupport::TimeZone[tz], record.ts_range.begin.time_zone
+        assert_equal time.usec, record.ts_range.begin.usec
+      end
+    end
+
     def test_create_numrange
       assert_equal_round_trip(@new_range, :num_range,
                               BigDecimal.new("0.5")...BigDecimal.new("1"))
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index 5a64da028b..1126908761 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -459,7 +459,7 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
         assert_equal :btree, index_d.using
         assert_equal :gin,   index_e.using
 
-        assert_equal :desc,  index_d.orders[INDEX_D_COLUMN]
+        assert_equal :desc,  index_d.orders
       end
     end
 
@@ -500,6 +500,38 @@ class SchemaForeignKeyTest < ActiveRecord::PostgreSQLTestCase
   end
 end
 
+class SchemaIndexOpclassTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+    @connection.create_table "trains" do |t|
+      t.string :name
+      t.text :description
+    end
+  end
+
+  teardown do
+    @connection.drop_table "trains", if_exists: true
+  end
+
+  def test_string_opclass_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_description ON trains USING btree(name text_pattern_ops, description text_pattern_ops)"
+
+    output = dump_table_schema "trains"
+
+    assert_match(/opclass: :text_pattern_ops/, output)
+  end
+
+  def test_non_default_opclass_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_description ON trains USING btree(name, description text_pattern_ops)"
+
+    output = dump_table_schema "trains"
+
+    assert_match(/opclass: \{ description: :text_pattern_ops \}/, output)
+  end
+end
+
 class DefaultsUsingMultipleSchemasAndDomainTest < ActiveRecord::PostgreSQLTestCase
   setup do
     @connection = ActiveRecord::Base.connection
diff --git a/activerecord/test/cases/adapters/postgresql/serial_test.rb b/activerecord/test/cases/adapters/postgresql/serial_test.rb
index 3c020a88d0..6a99323be5 100644
--- a/activerecord/test/cases/adapters/postgresql/serial_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/serial_test.rb
@@ -86,3 +86,71 @@ class PostgresqlBigSerialTest < ActiveRecord::PostgreSQLTestCase
     assert_match %r{t\.bigint\s+"serials_id",\s+default: -> \{ "nextval\('postgresql_big_serials_id_seq'::regclass\)" \}$}, output
   end
 end
+
+module SequenceNameDetectionTestCases
+  class CollidedSequenceNameTest < ActiveRecord::PostgreSQLTestCase
+    include SchemaDumpingHelper
+
+    def setup
+      @connection = ActiveRecord::Base.connection
+      @connection.create_table :foo_bar, force: true do |t|
+        t.serial :baz_id
+      end
+      @connection.create_table :foo, force: true do |t|
+        t.serial :bar_id
+        t.bigserial :bar_baz_id
+      end
+    end
+
+    def teardown
+      @connection.drop_table :foo_bar, if_exists: true
+      @connection.drop_table :foo, if_exists: true
+    end
+
+    def test_serial_columns
+      columns = @connection.columns(:foo)
+      columns.each do |column|
+        assert_equal :integer, column.type
+        assert column.serial?
+      end
+    end
+
+    def test_schema_dump_with_collided_sequence_name
+      output = dump_table_schema "foo"
+      assert_match %r{t\.serial\s+"bar_id",\s+null: false$}, output
+      assert_match %r{t\.bigserial\s+"bar_baz_id",\s+null: false$}, output
+    end
+  end
+
+  class LongerSequenceNameDetectionTest < ActiveRecord::PostgreSQLTestCase
+    include SchemaDumpingHelper
+
+    def setup
+      @table_name = "long_table_name_to_test_sequence_name_detection_for_serial_cols"
+      @connection = ActiveRecord::Base.connection
+      @connection.create_table @table_name, force: true do |t|
+        t.serial :seq
+        t.bigserial :bigseq
+      end
+    end
+
+    def teardown
+      @connection.drop_table @table_name, if_exists: true
+    end
+
+    def test_serial_columns
+      columns = @connection.columns(@table_name)
+      columns.each do |column|
+        assert_equal :integer, column.type
+        assert column.serial?
+      end
+    end
+
+    def test_schema_dump_with_long_table_name
+      output = dump_table_schema @table_name
+      assert_match %r{create_table "#{@table_name}", force: :cascade}, output
+      assert_match %r{t\.serial\s+"seq",\s+null: false$}, output
+      assert_match %r{t\.bigserial\s+"bigseq",\s+null: false$}, output
+    end
+  end
+end
diff --git a/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb b/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
index a3eb4f9e67..fef4b02b04 100644
--- a/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
@@ -23,7 +23,7 @@ module ActiveRecord
             assert_equal "bar", cache["foo"]
 
             pid = fork {
-              lookup = cache["foo"];
+              lookup = cache["foo"]
               exit!(!lookup)
             }
 
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index f56adf4a5e..c24dfeb345 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -91,6 +91,90 @@ module ActiveRecord
       end
     end
 
+    test "raises LockWaitTimeout when lock wait timeout exceeded" do
+      skip unless ActiveRecord::Base.connection.postgresql_version >= 90300
+      assert_raises(ActiveRecord::LockWaitTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET lock_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET lock_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises QueryCanceled when statement timeout exceeded" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET statement_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET statement_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises QueryCanceled when canceling statement due to user request" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch.count_down
+            sleep(0.5)
+            conn = Sample.connection
+            pid = conn.query_value("SELECT pid FROM pg_stat_activity WHERE query LIKE '% FOR UPDATE'")
+            conn.execute("SELECT pg_cancel_backend(#{pid})")
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch.wait
+            Sample.lock.find(s.id)
+          end
+        ensure
+          thread.join
+        end
+      end
+    end
+
     private
 
       def with_warning_suppression
diff --git a/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb b/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
index 449023b6eb..8212ed4263 100644
--- a/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
@@ -30,6 +30,6 @@ class PostgresqlTypeLookupTest < ActiveRecord::PostgreSQLTestCase
     big_range = 0..123456789123456789
 
     assert_raises(ActiveModel::RangeError) { int_range.serialize(big_range) }
-    assert_equal "[0,123456789123456789]", bigint_range.serialize(big_range)
+    assert_equal "[0,123456789123456789]", @connection.type_cast(bigint_range.serialize(big_range))
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index 466d281e85..c24e0cb330 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -222,68 +222,66 @@ class PostgresqlUUIDGenerationTest < ActiveRecord::PostgreSQLTestCase
     connection.execute "DROP FUNCTION IF EXISTS my_uuid_generator();"
   end
 
-  if ActiveRecord::Base.connection.supports_extensions?
-    def test_id_is_uuid
-      assert_equal :uuid, UUID.columns_hash["id"].type
-      assert UUID.primary_key
-    end
+  def test_id_is_uuid
+    assert_equal :uuid, UUID.columns_hash["id"].type
+    assert UUID.primary_key
+  end
 
-    def test_id_has_a_default
-      u = UUID.create
-      assert_not_nil u.id
-    end
+  def test_id_has_a_default
+    u = UUID.create
+    assert_not_nil u.id
+  end
 
-    def test_auto_create_uuid
-      u = UUID.create
-      u.reload
-      assert_not_nil u.other_uuid
-    end
+  def test_auto_create_uuid
+    u = UUID.create
+    u.reload
+    assert_not_nil u.other_uuid
+  end
 
-    def test_pk_and_sequence_for_uuid_primary_key
-      pk, seq = connection.pk_and_sequence_for("pg_uuids")
-      assert_equal "id", pk
-      assert_nil seq
-    end
+  def test_pk_and_sequence_for_uuid_primary_key
+    pk, seq = connection.pk_and_sequence_for("pg_uuids")
+    assert_equal "id", pk
+    assert_nil seq
+  end
 
-    def test_schema_dumper_for_uuid_primary_key
-      schema = dump_table_schema "pg_uuids"
-      assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: -> { "uuid_generate_v1\(\)" }/, schema)
-      assert_match(/t\.uuid "other_uuid", default: -> { "uuid_generate_v4\(\)" }/, schema)
-    end
+  def test_schema_dumper_for_uuid_primary_key
+    schema = dump_table_schema "pg_uuids"
+    assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: -> { "uuid_generate_v1\(\)" }/, schema)
+    assert_match(/t\.uuid "other_uuid", default: -> { "uuid_generate_v4\(\)" }/, schema)
+  end
+
+  def test_schema_dumper_for_uuid_primary_key_with_custom_default
+    schema = dump_table_schema "pg_uuids_2"
+    assert_match(/\bcreate_table "pg_uuids_2", id: :uuid, default: -> { "my_uuid_generator\(\)" }/, schema)
+    assert_match(/t\.uuid "other_uuid_2", default: -> { "my_uuid_generator\(\)" }/, schema)
+  end
 
-    def test_schema_dumper_for_uuid_primary_key_with_custom_default
-      schema = dump_table_schema "pg_uuids_2"
-      assert_match(/\bcreate_table "pg_uuids_2", id: :uuid, default: -> { "my_uuid_generator\(\)" }/, schema)
-      assert_match(/t\.uuid "other_uuid_2", default: -> { "my_uuid_generator\(\)" }/, schema)
+  def test_schema_dumper_for_uuid_primary_key_default
+    schema = dump_table_schema "pg_uuids_3"
+    if connection.supports_pgcrypto_uuid?
+      assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "gen_random_uuid\(\)" }/, schema)
+    else
+      assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
     end
+  end
+
+  def test_schema_dumper_for_uuid_primary_key_default_in_legacy_migration
+    @verbose_was = ActiveRecord::Migration.verbose
+    ActiveRecord::Migration.verbose = false
 
-    def test_schema_dumper_for_uuid_primary_key_default
-      schema = dump_table_schema "pg_uuids_3"
-      if connection.supports_pgcrypto_uuid?
-        assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "gen_random_uuid\(\)" }/, schema)
-      else
-        assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
+    migration = Class.new(ActiveRecord::Migration[5.0]) do
+      def version; 101 end
+      def migrate(x)
+        create_table("pg_uuids_4", id: :uuid)
       end
-    end
+    end.new
+    ActiveRecord::Migrator.new(:up, [migration]).migrate
 
-    def test_schema_dumper_for_uuid_primary_key_default_in_legacy_migration
-      @verbose_was = ActiveRecord::Migration.verbose
-      ActiveRecord::Migration.verbose = false
-
-      migration = Class.new(ActiveRecord::Migration[5.0]) do
-        def version; 101 end
-        def migrate(x)
-          create_table("pg_uuids_4", id: :uuid)
-        end
-      end.new
-      ActiveRecord::Migrator.new(:up, [migration]).migrate
-
-      schema = dump_table_schema "pg_uuids_4"
-      assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
-    ensure
-      drop_table "pg_uuids_4"
-      ActiveRecord::Migration.verbose = @verbose_was
-    end
+    schema = dump_table_schema "pg_uuids_4"
+    assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
+  ensure
+    drop_table "pg_uuids_4"
+    ActiveRecord::Migration.verbose = @verbose_was
   end
 end
 
@@ -302,38 +300,36 @@ class PostgresqlUUIDTestNilDefault < ActiveRecord::PostgreSQLTestCase
     drop_table "pg_uuids"
   end
 
-  if ActiveRecord::Base.connection.supports_extensions?
-    def test_id_allows_default_override_via_nil
-      col_desc = connection.execute("SELECT pg_get_expr(d.adbin, d.adrelid) as default
-                                    FROM pg_attribute a
-                                    LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum
-                                    WHERE a.attname='id' AND a.attrelid = 'pg_uuids'::regclass").first
-      assert_nil col_desc["default"]
-    end
+  def test_id_allows_default_override_via_nil
+    col_desc = connection.execute("SELECT pg_get_expr(d.adbin, d.adrelid) as default
+                                  FROM pg_attribute a
+                                  LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum
+                                  WHERE a.attname='id' AND a.attrelid = 'pg_uuids'::regclass").first
+    assert_nil col_desc["default"]
+  end
 
-    def test_schema_dumper_for_uuid_primary_key_with_default_override_via_nil
-      schema = dump_table_schema "pg_uuids"
-      assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: nil/, schema)
-    end
+  def test_schema_dumper_for_uuid_primary_key_with_default_override_via_nil
+    schema = dump_table_schema "pg_uuids"
+    assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: nil/, schema)
+  end
 
-    def test_schema_dumper_for_uuid_primary_key_with_default_nil_in_legacy_migration
-      @verbose_was = ActiveRecord::Migration.verbose
-      ActiveRecord::Migration.verbose = false
-
-      migration = Class.new(ActiveRecord::Migration[5.0]) do
-        def version; 101 end
-        def migrate(x)
-          create_table("pg_uuids_4", id: :uuid, default: nil)
-        end
-      end.new
-      ActiveRecord::Migrator.new(:up, [migration]).migrate
-
-      schema = dump_table_schema "pg_uuids_4"
-      assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: nil/, schema)
-    ensure
-      drop_table "pg_uuids_4"
-      ActiveRecord::Migration.verbose = @verbose_was
-    end
+  def test_schema_dumper_for_uuid_primary_key_with_default_nil_in_legacy_migration
+    @verbose_was = ActiveRecord::Migration.verbose
+    ActiveRecord::Migration.verbose = false
+
+    migration = Class.new(ActiveRecord::Migration[5.0]) do
+      def version; 101 end
+      def migrate(x)
+        create_table("pg_uuids_4", id: :uuid, default: nil)
+      end
+    end.new
+    ActiveRecord::Migrator.new(:up, [migration]).migrate
+
+    schema = dump_table_schema "pg_uuids_4"
+    assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: nil/, schema)
+  ensure
+    drop_table "pg_uuids_4"
+    ActiveRecord::Migration.verbose = @verbose_was
   end
 end
 
@@ -367,23 +363,21 @@ class PostgresqlUUIDTestInverseOf < ActiveRecord::PostgreSQLTestCase
     drop_table "pg_uuid_posts"
   end
 
-  if ActiveRecord::Base.connection.supports_extensions?
-    def test_collection_association_with_uuid
-      post    = UuidPost.create!
-      comment = post.uuid_comments.create!
-      assert post.uuid_comments.find(comment.id)
-    end
+  def test_collection_association_with_uuid
+    post    = UuidPost.create!
+    comment = post.uuid_comments.create!
+    assert post.uuid_comments.find(comment.id)
+  end
 
-    def test_find_with_uuid
-      UuidPost.create!
-      assert_raise ActiveRecord::RecordNotFound do
-        UuidPost.find(123456)
-      end
+  def test_find_with_uuid
+    UuidPost.create!
+    assert_raise ActiveRecord::RecordNotFound do
+      UuidPost.find(123456)
     end
+  end
 
-    def test_find_by_with_uuid
-      UuidPost.create!
-      assert_nil UuidPost.find_by(id: 789)
-    end
+  def test_find_by_with_uuid
+    UuidPost.create!
+    assert_nil UuidPost.find_by(id: 789)
   end
 end
diff --git a/activerecord/test/cases/adapters/sqlite3/explain_test.rb b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
index 3b081d34e1..b6d2ccdb53 100644
--- a/activerecord/test/cases/adapters/sqlite3/explain_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "models/developer"
-require "models/computer"
+require "models/author"
+require "models/post"
 
 class SQLite3ExplainTest < ActiveRecord::SQLite3TestCase
-  fixtures :developers
+  fixtures :authors
 
   def test_explain_for_one_query
-    explain = Developer.where(id: 1).explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
-    assert_match(/(SEARCH )?TABLE developers USING (INTEGER )?PRIMARY KEY/, explain)
+    explain = Author.where(id: 1).explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
+    assert_match(/(SEARCH )?TABLE authors USING (INTEGER )?PRIMARY KEY/, explain)
   end
 
   def test_explain_with_eager_loading
-    explain = Developer.where(id: 1).includes(:audit_logs).explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
-    assert_match(/(SEARCH )?TABLE developers USING (INTEGER )?PRIMARY KEY/, explain)
-    assert_match %r(EXPLAIN for: SELECT "audit_logs"\.\* FROM "audit_logs" WHERE "audit_logs"\."developer_id" = (?:\? \[\["developer_id", 1\]\]|1)), explain
-    assert_match(/(SCAN )?TABLE audit_logs/, explain)
+    explain = Author.where(id: 1).includes(:posts).explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
+    assert_match(/(SEARCH )?TABLE authors USING (INTEGER )?PRIMARY KEY/, explain)
+    assert_match %r(EXPLAIN for: SELECT "posts"\.\* FROM "posts" WHERE "posts"\."author_id" = (?:\? \[\["author_id", 1\]\]|1)), explain
+    assert_match(/(SCAN )?TABLE posts/, explain)
   end
 end
diff --git a/activerecord/test/cases/adapters/sqlite3/json_test.rb b/activerecord/test/cases/adapters/sqlite3/json_test.rb
new file mode 100644
index 0000000000..6f247fcd22
--- /dev/null
+++ b/activerecord/test/cases/adapters/sqlite3/json_test.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "cases/json_shared_test_cases"
+
+class SQLite3JSONTest < ActiveRecord::SQLite3TestCase
+  include JSONSharedTestCases
+
+  def setup
+    super
+    @connection.create_table("json_data_type") do |t|
+      t.json "payload", default: {}
+      t.json "settings"
+    end
+  end
+
+  def test_default
+    @connection.add_column "json_data_type", "permissions", column_type, default: { "users": "read", "posts": ["read", "write"] }
+    klass.reset_column_information
+
+    assert_equal({ "users" => "read", "posts" => ["read", "write"] }, klass.column_defaults["permissions"])
+    assert_equal({ "users" => "read", "posts" => ["read", "write"] }, klass.new.permissions)
+  end
+
+  private
+    def column_type
+      :json
+    end
+end
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index 2b51a32db6..1357719422 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -269,14 +269,6 @@ module ActiveRecord
         end
       end
 
-      def test_indexes_logs_name
-        with_example_table do
-          assert_logged [["PRAGMA index_list(\"ex\")", "SCHEMA", []]] do
-            assert_deprecated { @conn.indexes("ex", "hello") }
-          end
-        end
-      end
-
       def test_table_exists_logs_name
         with_example_table do
           sql = <<-SQL
@@ -368,6 +360,51 @@ module ActiveRecord
         end
       end
 
+      class Barcode < ActiveRecord::Base
+        self.primary_key = "code"
+      end
+
+      def test_copy_table_with_existing_records_have_custom_primary_key
+        connection = Barcode.connection
+        connection.create_table(:barcodes, primary_key: "code", id: :string, limit: 42, force: true) do |t|
+          t.text :other_attr
+        end
+        code = "214fe0c2-dd47-46df-b53b-66090b3c1d40"
+        Barcode.create!(code: code, other_attr: "xxx")
+
+        connection.change_table "barcodes" do |t|
+          connection.remove_column("barcodes", "other_attr")
+        end
+
+        assert_equal code, Barcode.first.id
+      ensure
+        Barcode.reset_column_information
+      end
+
+      def test_copy_table_with_composite_primary_keys
+        connection = Barcode.connection
+        connection.create_table(:barcodes, primary_key: ["region", "code"], force: true) do |t|
+          t.string :region
+          t.string :code
+          t.text :other_attr
+        end
+        region = "US"
+        code = "214fe0c2-dd47-46df-b53b-66090b3c1d40"
+        Barcode.create!(region: region, code: code, other_attr: "xxx")
+
+        connection.change_table "barcodes" do |t|
+          connection.remove_column("barcodes", "other_attr")
+        end
+
+        assert_equal ["region", "code"], connection.primary_keys("barcodes")
+
+        barcode = Barcode.first
+        assert_equal region, barcode.region
+        assert_equal code, barcode.code
+      ensure
+        Barcode.reset_column_information
+      end
+
       def test_supports_extensions
         assert_not @conn.supports_extensions?, "does not support extensions"
       end
diff --git a/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb b/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
index 42b3841d41..61002435a4 100644
--- a/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
@@ -10,7 +10,7 @@ class SQLite3StatementPoolTest < ActiveRecord::SQLite3TestCase
       assert_equal "bar", cache["foo"]
 
       pid = fork {
-        lookup = cache["foo"];
+        lookup = cache["foo"]
         exit!(!lookup)
       }
 
diff --git a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
index e69cfe5e52..829e12fbc8 100644
--- a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
+++ b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
@@ -37,7 +37,7 @@ class CascadedEagerLoadingTest < ActiveRecord::TestCase
 
   def test_eager_association_loading_with_hmt_does_not_table_name_collide_when_joining_associations
     authors = Author.joins(:posts).eager_load(:comments).where(posts: { tags_count: 1 }).to_a
-    assert_equal 1, assert_no_queries { authors.size }
+    assert_equal 3, assert_no_queries { authors.size }
     assert_equal 10, assert_no_queries { authors[0].comments.size }
   end
 
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 559f0e9338..9a042c74db 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -427,7 +427,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
   def test_eager_association_loading_with_belongs_to_and_order_string_with_quoted_table_name
     quoted_posts_id = Comment.connection.quote_table_name("posts") + "." + Comment.connection.quote_column_name("id")
     assert_nothing_raised do
-      Comment.includes(:post).references(:posts).order(quoted_posts_id)
+      Comment.includes(:post).references(:posts).order(Arel.sql(quoted_posts_id))
     end
   end
 
@@ -874,14 +874,14 @@ class EagerAssociationTest < ActiveRecord::TestCase
       posts(:thinking, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: "UPPER(posts.title)", limit: 2, offset: 1
+        order: Arel.sql("UPPER(posts.title)"), limit: 2, offset: 1
       ).to_a
     )
     assert_equal(
       posts(:sti_post_and_comments, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: "UPPER(posts.title) DESC", limit: 2, offset: 1
+        order: Arel.sql("UPPER(posts.title) DESC"), limit: 2, offset: 1
       ).to_a
     )
   end
@@ -891,14 +891,14 @@ class EagerAssociationTest < ActiveRecord::TestCase
       posts(:thinking, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: ["UPPER(posts.title)", "posts.id"], limit: 2, offset: 1
+        order: [Arel.sql("UPPER(posts.title)"), "posts.id"], limit: 2, offset: 1
       ).to_a
     )
     assert_equal(
       posts(:sti_post_and_comments, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: ["UPPER(posts.title) DESC", "posts.id"], limit: 2, offset: 1
+        order: [Arel.sql("UPPER(posts.title) DESC"), "posts.id"], limit: 2, offset: 1
       ).to_a
     )
   end
@@ -1501,6 +1501,10 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal posts(:welcome), post
   end
 
+  test "eager-loading with a polymorphic association and using the existential predicate" do
+    assert_equal true, authors(:david).essays.eager_load(:writer).exists?
+  end
+
   # CollectionProxy#reader is expensive, so the preloader avoids calling it.
   test "preloading has_many_through association avoids calling association.reader" do
     ActiveRecord::Associations::HasManyAssociation.any_instance.expects(:reader).never
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index 979dd986de..c817d7267b 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -88,12 +88,6 @@ class DeveloperWithSymbolClassName < Developer
   has_and_belongs_to_many :projects, class_name: :ProjectWithSymbolsForKeys
 end
 
-ActiveSupport::Deprecation.silence do
-  class DeveloperWithConstantClassName < Developer
-    has_and_belongs_to_many :projects, class_name: ProjectWithSymbolsForKeys
-  end
-end
-
 class DeveloperWithExtendOption < Developer
   module NamedExtension
     def category
@@ -954,13 +948,6 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_with_constant_class_name
-    assert_nothing_raised do
-      developer = DeveloperWithConstantClassName.new
-      developer.projects
-    end
-  end
-
   def test_alternate_database
     professor = Professor.create(name: "Plum")
     course = Course.create(name: "Forensics")
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 6bd11a5d81..4ca11af791 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -831,7 +831,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_find_scoped_grouped_having
-    assert_equal 1, authors(:david).popular_grouped_posts.length
+    assert_equal 2, authors(:david).popular_grouped_posts.length
     assert_equal 0, authors(:mary).popular_grouped_posts.length
   end
 
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 521b388cee..046020e310 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -1250,10 +1250,18 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     TenantMembership.current_member = nil
   end
 
+  def test_has_many_through_with_scope_that_has_joined_same_table_with_parent_relation
+    assert_equal authors(:david), Author.joins(:comments_for_first_author).take
+  end
+
   def test_has_many_through_with_unscope_should_affect_to_through_scope
     assert_equal [comments(:eager_other_comment1)], authors(:mary).unordered_comments
   end
 
+  def test_has_many_through_with_scope_should_accept_string_and_hash_join
+    assert_equal authors(:david), Author.joins({ comments_for_first_author: :post }, "inner join posts posts_alias on authors.id = posts_alias.author_id").eager_load(:categories).take
+  end
+
   def test_has_many_through_with_scope_should_respect_table_alias
     family = Family.create!
     users = 3.times.map { User.create! }
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index 2a9ebd19ed..ec5d95080b 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -30,7 +30,8 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     ActiveRecord::SQLCounter.clear_log
     companies(:first_firm).account
   ensure
-    assert ActiveRecord::SQLCounter.log_all.all? { |sql| /order by/i !~ sql }, "ORDER BY was used in the query"
+    log_all = ActiveRecord::SQLCounter.log_all
+    assert log_all.all? { |sql| /order by/i !~ sql }, "ORDER BY was used in the query: #{log_all}"
   end
 
   def test_has_one_cache_nils
diff --git a/activerecord/test/cases/associations/inner_join_association_test.rb b/activerecord/test/cases/associations/inner_join_association_test.rb
index 23be344419..7be875fec6 100644
--- a/activerecord/test/cases/associations/inner_join_association_test.rb
+++ b/activerecord/test/cases/associations/inner_join_association_test.rb
@@ -27,6 +27,24 @@ class InnerJoinAssociationTest < ActiveRecord::TestCase
     end
   end
 
+  def test_construct_finder_sql_does_not_table_name_collide_on_duplicate_associations_with_left_outer_joins
+    sql = Person.joins(agents: :agents).left_outer_joins(agents: :agents).to_sql
+    assert_match(/agents_people_4/i, sql)
+  end
+
+  def test_construct_finder_sql_does_not_table_name_collide_with_string_joins
+    sql = Person.joins(:agents).joins("JOIN people agents_people ON agents_people.primary_contact_id = people.id").to_sql
+    assert_match(/agents_people_2/i, sql)
+  end
+
+  def test_construct_finder_sql_does_not_table_name_collide_with_aliased_joins
+    people = Person.arel_table
+    agents = people.alias("agents_people")
+    constraint = agents[:primary_contact_id].eq(people[:id])
+    sql = Person.joins(:agents).joins(agents.create_join(agents, agents.create_on(constraint))).to_sql
+    assert_match(/agents_people_2/i, sql)
+  end
+
   def test_construct_finder_sql_ignores_empty_joins_hash
     sql = Author.joins({}).to_sql
     assert_no_match(/JOIN/i, sql)
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index e13cf93dcf..c0d328ca8a 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -484,7 +484,10 @@ class InverseHasManyTests < ActiveRecord::TestCase
   def test_raise_record_not_found_error_when_no_ids_are_passed
     man = Man.create!
 
-    assert_raise(ActiveRecord::RecordNotFound) { man.interests.find() }
+    exception = assert_raise(ActiveRecord::RecordNotFound) { man.interests.load.find() }
+
+    assert_equal exception.model, "Interest"
+    assert_equal exception.primary_key, "id"
   end
 
   def test_trying_to_use_inverses_that_dont_exist_should_raise_an_error
@@ -672,6 +675,16 @@ class InversePolymorphicBelongsToTests < ActiveRecord::TestCase
     assert_equal old_inversed_man.object_id, new_inversed_man.object_id
   end
 
+  def test_inversed_instance_should_not_be_reloaded_after_stale_state_changed_with_validation
+    face = Face.new man: Man.new
+
+    old_inversed_man = face.man
+    face.save!
+    new_inversed_man = face.man
+
+    assert_equal old_inversed_man.object_id, new_inversed_man.object_id
+  end
+
   def test_should_not_try_to_set_inverse_instances_when_the_inverse_is_a_has_many
     i = interests(:llama_wrangling)
     m = i.polymorphic_man
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index 3e37e512ca..65d30d011b 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -24,6 +24,11 @@ require "models/category"
 require "models/categorization"
 require "models/membership"
 require "models/essay"
+require "models/hotel"
+require "models/department"
+require "models/chef"
+require "models/cake_designer"
+require "models/drink_designer"
 
 class NestedThroughAssociationsTest < ActiveRecord::TestCase
   fixtures :authors, :author_addresses, :books, :posts, :subscriptions, :subscribers, :tags, :taggings,
@@ -425,6 +430,11 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     assert authors.empty?
   end
 
+  def test_nested_has_many_through_with_scope_on_polymorphic_reflection
+    authors = Author.joins(:ordered_posts).where("posts.id" => posts(:misc_by_bob).id)
+    assert_equal [authors(:mary), authors(:bob)], authors.distinct.sort_by(&:id)
+  end
+
   def test_has_many_through_with_foreign_key_option_on_through_reflection
     assert_equal [posts(:welcome), posts(:authorless)], people(:david).agents_posts.order("posts.id")
     assert_equal [authors(:david)], references(:david_unicyclist).agents_posts_authors
@@ -569,6 +579,37 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     assert !c.post_taggings.empty?
   end
 
+  def test_polymorphic_has_many_through_when_through_association_has_not_loaded
+    cake_designer = CakeDesigner.create!(chef: Chef.new)
+    drink_designer = DrinkDesigner.create!(chef: Chef.new)
+    department = Department.create!(chefs: [cake_designer.chef, drink_designer.chef])
+    Hotel.create!(departments: [department])
+    hotel = Hotel.includes(:cake_designers, :drink_designers).take
+
+    assert_equal [cake_designer], hotel.cake_designers
+    assert_equal [drink_designer], hotel.drink_designers
+  end
+
+  def test_polymorphic_has_many_through_when_through_association_has_already_loaded
+    cake_designer = CakeDesigner.create!(chef: Chef.new)
+    drink_designer = DrinkDesigner.create!(chef: Chef.new)
+    department = Department.create!(chefs: [cake_designer.chef, drink_designer.chef])
+    Hotel.create!(departments: [department])
+    hotel = Hotel.includes(:chefs, :cake_designers, :drink_designers).take
+
+    assert_equal [cake_designer], hotel.cake_designers
+    assert_equal [drink_designer], hotel.drink_designers
+  end
+
+  def test_polymorphic_has_many_through_joined_different_table_twice
+    cake_designer = CakeDesigner.create!(chef: Chef.new)
+    drink_designer = DrinkDesigner.create!(chef: Chef.new)
+    department = Department.create!(chefs: [cake_designer.chef, drink_designer.chef])
+    hotel = Hotel.create!(departments: [department])
+
+    assert_equal hotel, Hotel.joins(:cake_designers, :drink_designers).take
+  end
+
   private
 
     def assert_includes_and_joins_equal(query, expected, association)
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 0ea8ef5cea..c48f7d3518 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -200,12 +200,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   if current_adapter?(:Mysql2Adapter)
     test "read attributes_before_type_cast on a boolean" do
       bool = Boolean.create!("value" => false)
-      if RUBY_PLATFORM.include?("java")
-        # JRuby will return the value before typecast as string.
-        assert_equal "0", bool.reload.attributes_before_type_cast["value"]
-      else
-        assert_equal 0, bool.reload.attributes_before_type_cast["value"]
-      end
+      assert_equal 0, bool.reload.attributes_before_type_cast["value"]
     end
   end
 
@@ -999,6 +994,11 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert_equal ["title"], model.accessed_fields
   end
 
+  test "generated attribute methods ancestors have correct class" do
+    mod = Topic.send(:generated_attribute_methods)
+    assert_match %r(GeneratedAttributeMethods), mod.inspect
+  end
+
   private
 
     def new_topic_like_ar_class(&block)
@@ -1019,14 +1019,6 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       ActiveRecord::Base.time_zone_aware_types = old_types
     end
 
-    def cached_columns
-      Topic.columns.map(&:name)
-    end
-
-    def time_related_columns_on_topic
-      Topic.columns.select { |c| [:time, :date, :datetime, :timestamp].include?(c.type) }
-    end
-
     def privatize(method_signature)
       @target.class_eval(<<-private_method, __FILE__, __LINE__ + 1)
         private
diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index 29a25b4461..2caf2a63d4 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -108,12 +108,14 @@ module ActiveRecord
 
       assert_equal 6, klass.attribute_types.length
       assert_equal 6, klass.column_defaults.length
+      assert_equal 6, klass.attribute_names.length
       assert_not klass.attribute_types.include?("wibble")
 
       klass.attribute :wibble, Type::Value.new
 
       assert_equal 7, klass.attribute_types.length
       assert_equal 7, klass.column_defaults.length
+      assert_equal 7, klass.attribute_names.length
       assert_includes klass.attribute_types, "wibble"
     end
 
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 1a1d4ce039..3497f6aae4 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -891,11 +891,9 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal 2147483648, company.rating
   end
 
-  unless current_adapter?(:SQLite3Adapter)
-    def test_bignum_pk
-      company = Company.create!(id: 2147483648, name: "foo")
-      assert_equal company, Company.find(company.id)
-    end
+  def test_bignum_pk
+    company = Company.create!(id: 2147483648, name: "foo")
+    assert_equal company, Company.find(company.id)
   end
 
   # TODO: extend defaults tests to other databases!
@@ -1444,17 +1442,57 @@ class BasicsTest < ActiveRecord::TestCase
     cache_columns = Developer.connection.schema_cache.columns_hash(Developer.table_name)
     assert_includes cache_columns.keys, "first_name"
     assert_not_includes Developer.columns_hash.keys, "first_name"
+    assert_not_includes SubDeveloper.columns_hash.keys, "first_name"
+    assert_not_includes SymbolIgnoredDeveloper.columns_hash.keys, "first_name"
   end
 
   test "ignored columns have no attribute methods" do
     refute Developer.new.respond_to?(:first_name)
     refute Developer.new.respond_to?(:first_name=)
     refute Developer.new.respond_to?(:first_name?)
+    refute SubDeveloper.new.respond_to?(:first_name)
+    refute SubDeveloper.new.respond_to?(:first_name=)
+    refute SubDeveloper.new.respond_to?(:first_name?)
+    refute SymbolIgnoredDeveloper.new.respond_to?(:first_name)
+    refute SymbolIgnoredDeveloper.new.respond_to?(:first_name=)
+    refute SymbolIgnoredDeveloper.new.respond_to?(:first_name?)
   end
 
   test "ignored columns don't prevent explicit declaration of attribute methods" do
     assert Developer.new.respond_to?(:last_name)
     assert Developer.new.respond_to?(:last_name=)
     assert Developer.new.respond_to?(:last_name?)
+    assert SubDeveloper.new.respond_to?(:last_name)
+    assert SubDeveloper.new.respond_to?(:last_name=)
+    assert SubDeveloper.new.respond_to?(:last_name?)
+    assert SymbolIgnoredDeveloper.new.respond_to?(:last_name)
+    assert SymbolIgnoredDeveloper.new.respond_to?(:last_name=)
+    assert SymbolIgnoredDeveloper.new.respond_to?(:last_name?)
+  end
+
+  test "ignored columns are stored as an array of string" do
+    assert_equal(%w(first_name last_name), Developer.ignored_columns)
+    assert_equal(%w(first_name last_name), SymbolIgnoredDeveloper.ignored_columns)
+  end
+
+  test "when #reload called, ignored columns' attribute methods are not defined" do
+    developer = Developer.create!(name: "Developer")
+    refute developer.respond_to?(:first_name)
+    refute developer.respond_to?(:first_name=)
+
+    developer.reload
+
+    refute developer.respond_to?(:first_name)
+    refute developer.respond_to?(:first_name=)
+  end
+
+  test "ignored columns not included in SELECT" do
+    query = Developer.all.to_sql.downcase
+
+    # ignored column
+    refute query.include?("first_name")
+
+    # regular column
+    assert query.include?("name")
   end
 end
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index c965404b07..be8aeed5ac 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -586,34 +586,6 @@ class EachTest < ActiveRecord::TestCase
     end
   end
 
-  test ".error_on_ignored_order_or_limit= is deprecated" do
-    begin
-      prev = ActiveRecord::Base.error_on_ignored_order
-      assert_deprecated "Please use error_on_ignored_order= instead." do
-        ActiveRecord::Base.error_on_ignored_order_or_limit = true
-      end
-      assert ActiveRecord::Base.error_on_ignored_order
-    ensure
-      ActiveRecord::Base.error_on_ignored_order = prev
-    end
-  end
-
-  test ".error_on_ignored_order_or_limit is deprecated" do
-    expected = ActiveRecord::Base.error_on_ignored_order
-    actual = assert_deprecated "Please use error_on_ignored_order instead." do
-      ActiveRecord::Base.error_on_ignored_order_or_limit
-    end
-    assert_equal expected, actual
-  end
-
-  test "#error_on_ignored_order_or_limit is deprecated" do
-    expected = ActiveRecord::Base.error_on_ignored_order
-    actual = assert_deprecated "Please use error_on_ignored_order instead." do
-      Post.new.error_on_ignored_order_or_limit
-    end
-    assert_equal expected, actual
-  end
-
   test ".find_each respects table alias" do
     assert_queries(1) do
       table_alias = Post.arel_table.alias("omg_posts")
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index b47fd0af41..55b50e4f84 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -260,6 +260,10 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal 3, Account.joins(:firm).distinct.order(:firm_id).limit(3).offset(2).count
   end
 
+  def test_distinct_count_with_group_by_and_order_and_limit
+    assert_equal({ 6 => 2 }, Account.group(:firm_id).distinct.order("1 DESC").limit(1).count)
+  end
+
   def test_should_group_by_summed_field_having_condition
     c = Account.group(:firm_id).having("sum(credit_limit) > 50").sum(:credit_limit)
     assert_nil        c[1]
@@ -659,14 +663,14 @@ class CalculationsTest < ActiveRecord::TestCase
   end
 
   def test_pluck_with_selection_clause
-    assert_equal [50, 53, 55, 60], Account.pluck("DISTINCT credit_limit").sort
-    assert_equal [50, 53, 55, 60], Account.pluck("DISTINCT accounts.credit_limit").sort
-    assert_equal [50, 53, 55, 60], Account.pluck("DISTINCT(credit_limit)").sort
+    assert_equal [50, 53, 55, 60], Account.pluck(Arel.sql("DISTINCT credit_limit")).sort
+    assert_equal [50, 53, 55, 60], Account.pluck(Arel.sql("DISTINCT accounts.credit_limit")).sort
+    assert_equal [50, 53, 55, 60], Account.pluck(Arel.sql("DISTINCT(credit_limit)")).sort
 
     # MySQL returns "SUM(DISTINCT(credit_limit))" as the column name unless
     # an alias is provided.  Without the alias, the column cannot be found
     # and properly typecast.
-    assert_equal [50 + 53 + 55 + 60], Account.pluck("SUM(DISTINCT(credit_limit)) as credit_limit")
+    assert_equal [50 + 53 + 55 + 60], Account.pluck(Arel.sql("SUM(DISTINCT(credit_limit)) as credit_limit"))
   end
 
   def test_plucks_with_ids
@@ -768,7 +772,7 @@ class CalculationsTest < ActiveRecord::TestCase
     companies = Company.order(:name).limit(3).load
 
     assert_queries 1 do
-      assert_equal ["37signals", "Apex", "Ex Nihilo"], companies.pluck("DISTINCT name")
+      assert_equal ["37signals", "Apex", "Ex Nihilo"], companies.pluck(Arel.sql("DISTINCT name"))
     end
   end
 
diff --git a/activerecord/test/cases/collection_cache_key_test.rb b/activerecord/test/cases/collection_cache_key_test.rb
index c137693211..19d6464a22 100644
--- a/activerecord/test/cases/collection_cache_key_test.rb
+++ b/activerecord/test/cases/collection_cache_key_test.rb
@@ -73,6 +73,16 @@ module ActiveRecord
       assert_equal last_developer_timestamp.to_s(ActiveRecord::Base.cache_timestamp_format), $3
     end
 
+    test "cache_key for relation with includes" do
+      comments = Comment.includes(:post).where("posts.type": "Post")
+      assert_match(/\Acomments\/query-(\h+)-(\d+)-(\d+)\z/, comments.cache_key)
+    end
+
+    test "cache_key for loaded relation with includes" do
+      comments = Comment.includes(:post).where("posts.type": "Post").load
+      assert_match(/\Acomments\/query-(\h+)-(\d+)-(\d+)\z/, comments.cache_key)
+    end
+
     test "it triggers at most one query" do
       developers = Developer.where(name: "David")
 
diff --git a/activerecord/test/cases/comment_test.rb b/activerecord/test/cases/comment_test.rb
index 1bcafd4b55..584e03d196 100644
--- a/activerecord/test/cases/comment_test.rb
+++ b/activerecord/test/cases/comment_test.rb
@@ -142,5 +142,27 @@ if ActiveRecord::Base.connection.supports_comments?
       assert_match %r[t\.string\s+"absent_comment"\n], output
       assert_no_match %r[t\.string\s+"absent_comment", comment:\n], output
     end
+
+    def test_change_table_comment
+      @connection.change_table_comment :commenteds, "Edited table comment"
+      assert_equal "Edited table comment", @connection.table_comment("commenteds")
+    end
+
+    def test_change_table_comment_to_nil
+      @connection.change_table_comment :commenteds, nil
+      assert_nil @connection.table_comment("commenteds")
+    end
+
+    def test_change_column_comment
+      @connection.change_column_comment :commenteds, :name, "Edited column comment"
+      column = Commented.columns_hash["name"]
+      assert_equal "Edited column comment", column.comment
+    end
+
+    def test_change_column_comment_to_nil
+      @connection.change_column_comment :commenteds, :name, nil
+      column = Commented.columns_hash["name"]
+      assert_nil column.comment
+    end
   end
 end
diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index 74d0ed348e..cae74a2b9b 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -1,10 +1,15 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "models/person"
 
 module ActiveRecord
   module ConnectionAdapters
     class ConnectionHandlerTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      fixtures :people
+
       def setup
         @handler = ConnectionHandler.new
         @spec_name = "primary"
@@ -139,6 +144,33 @@ module ActiveRecord
           rd.close
         end
 
+        def test_forked_child_doesnt_mangle_parent_connection
+          object_id = ActiveRecord::Base.connection.object_id
+          assert ActiveRecord::Base.connection.active?
+
+          rd, wr = IO.pipe
+          rd.binmode
+          wr.binmode
+
+          pid = fork {
+            rd.close
+            if ActiveRecord::Base.connection.active?
+              wr.write Marshal.dump ActiveRecord::Base.connection.object_id
+            end
+            wr.close
+
+            exit # allow finalizers to run
+          }
+
+          wr.close
+
+          Process.waitpid pid
+          assert_not_equal object_id, Marshal.load(rd.read)
+          rd.close
+
+          assert_equal 3, ActiveRecord::Base.connection.select_value("SELECT COUNT(*) FROM people")
+        end
+
         def test_retrieve_connection_pool_copies_schema_cache_from_ancestor_pool
           @pool.schema_cache = @pool.connection.schema_cache
           @pool.schema_cache.add("posts")
diff --git a/activerecord/test/cases/connection_pool_test.rb b/activerecord/test/cases/connection_pool_test.rb
index 2bfe490602..1e08cc74dc 100644
--- a/activerecord/test/cases/connection_pool_test.rb
+++ b/activerecord/test/cases/connection_pool_test.rb
@@ -156,6 +156,53 @@ module ActiveRecord
         @pool.connections.each { |conn| conn.close if conn.in_use? }
       end
 
+      def test_flush
+        idle_conn = @pool.checkout
+        recent_conn = @pool.checkout
+        active_conn = @pool.checkout
+
+        @pool.checkin idle_conn
+        @pool.checkin recent_conn
+
+        assert_equal 3, @pool.connections.length
+
+        def idle_conn.seconds_idle
+          1000
+        end
+
+        @pool.flush(30)
+
+        assert_equal 2, @pool.connections.length
+
+        assert_equal [recent_conn, active_conn].sort_by(&:__id__), @pool.connections.sort_by(&:__id__)
+      ensure
+        @pool.checkin active_conn
+      end
+
+      def test_flush_bang
+        idle_conn = @pool.checkout
+        recent_conn = @pool.checkout
+        active_conn = @pool.checkout
+        _dead_conn = Thread.new { @pool.checkout }.join
+
+        @pool.checkin idle_conn
+        @pool.checkin recent_conn
+
+        assert_equal 4, @pool.connections.length
+
+        def idle_conn.seconds_idle
+          1000
+        end
+
+        @pool.flush!
+
+        assert_equal 1, @pool.connections.length
+
+        assert_equal [active_conn].sort_by(&:__id__), @pool.connections.sort_by(&:__id__)
+      ensure
+        @pool.checkin active_conn
+      end
+
       def test_remove_connection
         conn = @pool.checkout
         assert conn.in_use?
@@ -205,6 +252,14 @@ module ActiveRecord
         end.join
       end
 
+      def test_checkout_order_is_lifo
+        conn1 = @pool.checkout
+        conn2 = @pool.checkout
+        @pool.checkin conn1
+        @pool.checkin conn2
+        assert_equal [conn2, conn1], 2.times.map { @pool.checkout }
+      end
+
       # The connection pool is "fair" if threads waiting for
       # connections receive them in the order in which they began
       # waiting.  This ensures that we don't timeout one HTTP request
diff --git a/activerecord/test/cases/connection_specification/resolver_test.rb b/activerecord/test/cases/connection_specification/resolver_test.rb
index 3fa0ca8366..5b80f16a44 100644
--- a/activerecord/test/cases/connection_specification/resolver_test.rb
+++ b/activerecord/test/cases/connection_specification/resolver_test.rb
@@ -19,7 +19,7 @@ module ActiveRecord
             spec "ridiculous://foo?encoding=utf8"
           end
 
-          assert_match "Could not load 'active_record/connection_adapters/ridiculous_adapter'", error.message
+          assert_match "Could not load the 'ridiculous' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", error.message
         end
 
         # The abstract adapter is used simply to bypass the bit of code that
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 78cb89ccc5..7cda712112 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -308,6 +308,24 @@ class EnumTest < ActiveRecord::TestCase
     end
   end
 
+  test "reserved enum values for relation" do
+    relation_method_samples = [
+      :records,
+      :to_ary,
+      :scope_for_create
+    ]
+
+    relation_method_samples.each do |value|
+      e = assert_raises(ArgumentError, "enum value `#{value}` should not be allowed") do
+        Class.new(ActiveRecord::Base) do
+          self.table_name = "books"
+          enum category: [:other, value]
+        end
+      end
+      assert_match(/You tried to define an enum named .* on the model/, e.message)
+    end
+  end
+
   test "overriding enum method should not raise" do
     assert_nothing_raised do
       Class.new(ActiveRecord::Base) do
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index 55496147c1..e936c56ab8 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -9,6 +9,7 @@ require "models/company"
 require "models/tagging"
 require "models/topic"
 require "models/reply"
+require "models/rating"
 require "models/entrant"
 require "models/project"
 require "models/developer"
@@ -119,6 +120,21 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal "The Fourth Topic of the day", records[2].title
   end
 
+  def test_find_with_ids_with_no_id_passed
+    exception = assert_raises(ActiveRecord::RecordNotFound) { Topic.find }
+    assert_equal exception.model, "Topic"
+    assert_equal exception.primary_key, "id"
+  end
+
+  def test_find_with_ids_with_id_out_of_range
+    exception = assert_raises(ActiveRecord::RecordNotFound) do
+      Topic.find("9999999999999999999999999999999")
+    end
+
+    assert_equal exception.model, "Topic"
+    assert_equal exception.primary_key, "id"
+  end
+
   def test_find_passing_active_record_object_is_not_permitted
     assert_raises(ArgumentError) do
       Topic.find(Topic.last)
@@ -156,6 +172,32 @@ class FinderTest < ActiveRecord::TestCase
     assert_raise(NoMethodError) { Topic.exists?([1, 2]) }
   end
 
+  def test_exists_with_scope
+    davids = Author.where(name: "David")
+    assert_equal true, davids.exists?
+    assert_equal true, davids.exists?(authors(:david).id)
+    assert_equal false, davids.exists?(authors(:mary).id)
+    assert_equal false, davids.exists?("42")
+    assert_equal false, davids.exists?(42)
+    assert_equal false, davids.exists?(davids.new.id)
+
+    fake = Author.where(name: "fake author")
+    assert_equal false, fake.exists?
+    assert_equal false, fake.exists?(authors(:david).id)
+  end
+
+  def test_exists_uses_existing_scope
+    post = authors(:david).posts.first
+    authors = Author.includes(:posts).where(name: "David", posts: { id: post.id })
+    assert_equal true, authors.exists?(authors(:david).id)
+  end
+
+  def test_any_with_scope_on_hash_includes
+    post = authors(:david).posts.first
+    categories = Categorization.includes(author: :posts).where(posts: { id: post.id })
+    assert_equal true, categories.exists?
+  end
+
   def test_exists_with_polymorphic_relation
     post = Post.create!(title: "Post", body: "default", taggings: [Tagging.new(comment: "tagging comment")])
     relation = Post.tagged_with_comment("tagging comment")
@@ -212,7 +254,7 @@ class FinderTest < ActiveRecord::TestCase
 
   # Ensure +exists?+ runs without an error by excluding order value.
   def test_exists_with_order
-    assert_equal true, Topic.order("invalid sql here").exists?
+    assert_equal true, Topic.order(Arel.sql("invalid sql here")).exists?
   end
 
   def test_exists_with_joins
@@ -244,6 +286,13 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal true, author.unique_categorized_posts.includes(:special_comments).order("comments.tags_count DESC").limit(1).exists?
   end
 
+  def test_exists_should_reference_correct_aliases_while_joining_tables_of_has_many_through_association
+    assert_nothing_raised do
+      developer = developers(:david)
+      developer.ratings.includes(comment: :post).where(posts: { id: 1 }).exists?
+    end
+  end
+
   def test_exists_with_empty_table_and_no_args_given
     Topic.delete_all
     assert_equal false, Topic.exists?
@@ -618,7 +667,7 @@ class FinderTest < ActiveRecord::TestCase
 
   def test_last_with_irreversible_order
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("coalesce(author_name, title)").last
+      Topic.order(Arel.sql("coalesce(author_name, title)")).last
     end
   end
 
diff --git a/activerecord/test/cases/instrumentation_test.rb b/activerecord/test/cases/instrumentation_test.rb
new file mode 100644
index 0000000000..e6e8468757
--- /dev/null
+++ b/activerecord/test/cases/instrumentation_test.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/book"
+
+module ActiveRecord
+  class InstrumentationTest < ActiveRecord::TestCase
+    def test_payload_name_on_load
+      Book.create(name: "test book")
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "SELECT"
+          assert_equal "Book Load", event.payload[:name]
+        end
+      end
+      Book.first
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_create
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "INSERT"
+          assert_equal "Book Create", event.payload[:name]
+        end
+      end
+      Book.create(name: "test book")
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_update
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "UPDATE"
+          assert_equal "Book Update", event.payload[:name]
+        end
+      end
+      book = Book.create(name: "test book")
+      book.update_attribute(:name, "new name")
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_update_all
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "UPDATE"
+          assert_equal "Book Update All", event.payload[:name]
+        end
+      end
+      Book.create(name: "test book")
+      Book.update_all(name: "new name")
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_destroy
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "DELETE"
+          assert_equal "Book Destroy", event.payload[:name]
+        end
+      end
+      book = Book.create(name: "test book")
+      book.destroy
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+  end
+end
diff --git a/activerecord/test/cases/invertible_migration_test.rb b/activerecord/test/cases/invertible_migration_test.rb
index 20e747142b..ebe0b0aa87 100644
--- a/activerecord/test/cases/invertible_migration_test.rb
+++ b/activerecord/test/cases/invertible_migration_test.rb
@@ -161,6 +161,15 @@ module ActiveRecord
       end
     end
 
+    class UpOnlyMigration < SilentMigration
+      def change
+        add_column :horses, :oldie, :integer, default: 0
+        up_only { execute "update horses set oldie = 1" }
+      end
+    end
+
+    self.use_transactional_tests = false
+
     setup do
       @verbose_was, ActiveRecord::Migration.verbose = ActiveRecord::Migration.verbose, false
     end
@@ -295,6 +304,8 @@ module ActiveRecord
 
         migration2.migrate(:down)
         assert_equal false, Horse.connection.extension_enabled?("hstore")
+      ensure
+        enable_extension!("hstore", ActiveRecord::Base.connection)
       end
     end
 
@@ -376,5 +387,23 @@ module ActiveRecord
               "horses_index_named index should not exist"
       end
     end
+
+    def test_up_only
+      InvertibleMigration.new.migrate(:up)
+      horse1 = Horse.create
+      # populates existing horses with oldie = 1 but new ones have default 0
+      UpOnlyMigration.new.migrate(:up)
+      Horse.reset_column_information
+      horse1.reload
+      horse2 = Horse.create
+
+      assert 1, horse1.oldie # created before migration
+      assert 0, horse2.oldie # created after migration
+
+      UpOnlyMigration.new.migrate(:down) # should be no error
+      connection = ActiveRecord::Base.connection
+      assert !connection.column_exists?(:horses, :oldie)
+      Horse.reset_column_information
+    end
   end
 end
diff --git a/activerecord/test/cases/json_attribute_test.rb b/activerecord/test/cases/json_attribute_test.rb
index 63f3c77fc3..afc39d0420 100644
--- a/activerecord/test/cases/json_attribute_test.rb
+++ b/activerecord/test/cases/json_attribute_test.rb
@@ -19,14 +19,14 @@ class JsonAttributeTest < ActiveRecord::TestCase
   def setup
     super
     @connection.create_table("json_data_type") do |t|
-      t.text "payload"
-      t.text "settings"
+      t.string "payload"
+      t.string "settings"
     end
   end
 
   private
     def column_type
-      :text
+      :string
     end
 
     def klass
diff --git a/activerecord/test/cases/json_shared_test_cases.rb b/activerecord/test/cases/json_shared_test_cases.rb
index 56ec8c8a82..b0c0f2c283 100644
--- a/activerecord/test/cases/json_shared_test_cases.rb
+++ b/activerecord/test/cases/json_shared_test_cases.rb
@@ -23,7 +23,7 @@ module JSONSharedTestCases
   def test_column
     column = klass.columns_hash["payload"]
     assert_equal column_type, column.type
-    assert_equal column_type.to_s, column.sql_type
+    assert_type_match column_type, column.sql_type
 
     type = klass.type_for_attribute("payload")
     assert_not type.binary?
@@ -36,7 +36,7 @@ module JSONSharedTestCases
     klass.reset_column_information
     column = klass.columns_hash["users"]
     assert_equal column_type, column.type
-    assert_equal column_type.to_s, column.sql_type
+    assert_type_match column_type, column.sql_type
   end
 
   def test_schema_dumping
@@ -66,26 +66,26 @@ module JSONSharedTestCases
   end
 
   def test_rewrite
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k":"v"}')|)
+    @connection.execute(insert_statement_per_database('{"k":"v"}'))
     x = klass.first
     x.payload = { '"a\'' => "b" }
     assert x.save!
   end
 
   def test_select
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k":"v"}')|)
+    @connection.execute(insert_statement_per_database('{"k":"v"}'))
     x = klass.first
     assert_equal({ "k" => "v" }, x.payload)
   end
 
   def test_select_multikey
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k1":"v1", "k2":"v2", "k3":[1,2,3]}')|)
+    @connection.execute(insert_statement_per_database('{"k1":"v1", "k2":"v2", "k3":[1,2,3]}'))
     x = klass.first
     assert_equal({ "k1" => "v1", "k2" => "v2", "k3" => [1, 2, 3] }, x.payload)
   end
 
   def test_null_json
-    @connection.execute("insert into json_data_type (payload) VALUES(null)")
+    @connection.execute(insert_statement_per_database("null"))
     x = klass.first
     assert_nil(x.payload)
   end
@@ -107,13 +107,13 @@ module JSONSharedTestCases
   end
 
   def test_select_array_json_value
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|)
+    @connection.execute(insert_statement_per_database('["v0",{"k1":"v1"}]'))
     x = klass.first
     assert_equal(["v0", { "k1" => "v1" }], x.payload)
   end
 
   def test_rewrite_array_json_value
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|)
+    @connection.execute(insert_statement_per_database('["v0",{"k1":"v1"}]'))
     x = klass.first
     x.payload = ["v1", { "k2" => "v2" }, "v3"]
     assert x.save!
@@ -253,4 +253,17 @@ module JSONSharedTestCases
     def klass
       JsonDataType
     end
+
+    def assert_type_match(type, sql_type)
+      native_type = ActiveRecord::Base.connection.native_database_types[type][:name]
+      assert_match %r(\A#{native_type}\b), sql_type
+    end
+
+    def insert_statement_per_database(values)
+      if current_adapter?(:OracleAdapter)
+        "insert into json_data_type (id, payload) VALUES (json_data_type_seq.nextval, '#{values}')"
+      else
+        "insert into json_data_type (payload) VALUES ('#{values}')"
+      end
+    end
 end
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index 743680ba92..e857180bd1 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -565,18 +565,18 @@ unless in_memory_db?
       end
     end
 
-    # Locking a record reloads it.
-    def test_sane_lock_method
+    def test_lock_does_not_raise_when_the_object_is_not_dirty
+      person = Person.find 1
       assert_nothing_raised do
-        Person.transaction do
-          person = Person.find 1
-          old, person.first_name = person.first_name, "fooman"
-          # Locking a dirty record is deprecated
-          assert_deprecated do
-            person.lock!
-          end
-          assert_equal old, person.first_name
-        end
+        person.lock!
+      end
+    end
+
+    def test_lock_raises_when_the_record_is_dirty
+      person = Person.find 1
+      person.first_name = "fooman"
+      assert_raises(RuntimeError) do
+        person.lock!
       end
     end
 
@@ -611,14 +611,12 @@ unless in_memory_db?
       end
     end
 
-    if current_adapter?(:PostgreSQLAdapter, :OracleAdapter)
-      def test_no_locks_no_wait
-        first, second = duel { Person.find 1 }
-        assert first.end > second.end
-      end
-
-      private
+    def test_no_locks_no_wait
+      first, second = duel { Person.find 1 }
+      assert first.end > second.end
+    end
 
+    private
       def duel(zzz = 5)
         t0, t1, t2, t3 = nil, nil, nil, nil
 
@@ -646,6 +644,5 @@ unless in_memory_db?
         assert t3 > t2
         [t0.to_f..t1.to_f, t2.to_f..t3.to_f]
       end
-    end
   end
 end
diff --git a/activerecord/test/cases/migration/change_schema_test.rb b/activerecord/test/cases/migration/change_schema_test.rb
index 7b0644e9c0..38a906c8f5 100644
--- a/activerecord/test/cases/migration/change_schema_test.rb
+++ b/activerecord/test/cases/migration/change_schema_test.rb
@@ -264,19 +264,18 @@ module ActiveRecord
           t.column :foo, :timestamp
         end
 
-        klass = Class.new(ActiveRecord::Base)
-        klass.table_name = "testings"
+        column = connection.columns(:testings).find { |c| c.name == "foo" }
 
-        assert_equal :datetime, klass.columns_hash["foo"].type
+        assert_equal :datetime, column.type
 
         if current_adapter?(:PostgreSQLAdapter)
-          assert_equal "timestamp without time zone", klass.columns_hash["foo"].sql_type
+          assert_equal "timestamp without time zone", column.sql_type
         elsif current_adapter?(:Mysql2Adapter)
-          assert_equal "timestamp", klass.columns_hash["foo"].sql_type
+          assert_equal "timestamp", column.sql_type
         elsif current_adapter?(:OracleAdapter)
-          assert_equal "TIMESTAMP(6)", klass.columns_hash["foo"].sql_type
+          assert_equal "TIMESTAMP(6)", column.sql_type
         else
-          assert_equal klass.connection.type_to_sql("datetime"), klass.columns_hash["foo"].sql_type
+          assert_equal connection.type_to_sql("datetime"), column.sql_type
         end
       end
 
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 0b5e983f14..58bc558619 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -213,6 +213,11 @@ module ActiveRecord
         assert_equal [:remove_index, [:table, { name: "new_index" }]], remove
       end
 
+      def test_invert_add_index_with_algorithm_option
+        remove = @recorder.inverse_of :add_index, [:table, :one, algorithm: :concurrently]
+        assert_equal [:remove_index, [:table, { column: :one, algorithm: :concurrently }]], remove
+      end
+
       def test_invert_remove_index
         add = @recorder.inverse_of :remove_index, [:table, :one]
         assert_equal [:add_index, [:table, :one]], add
diff --git a/activerecord/test/cases/migration/compatibility_test.rb b/activerecord/test/cases/migration/compatibility_test.rb
index cb3b02c02a..cc2391f349 100644
--- a/activerecord/test/cases/migration/compatibility_test.rb
+++ b/activerecord/test/cases/migration/compatibility_test.rb
@@ -16,7 +16,7 @@ module ActiveRecord
         ActiveRecord::Migration.verbose = false
 
         connection.create_table :testings do |t|
-          t.column :foo, :string, limit: 100
+          t.column :foo, :string, limit: 5
           t.column :bar, :string, limit: 100
         end
       end
@@ -126,15 +126,32 @@ module ActiveRecord
         end
         assert_match(/LegacyMigration < ActiveRecord::Migration\[4\.2\]/, e.message)
       end
+
+      if current_adapter?(:PostgreSQLAdapter)
+        class Testing < ActiveRecord::Base
+        end
+
+        def test_legacy_change_column_with_null_executes_update
+          migration = Class.new(ActiveRecord::Migration[5.1]) {
+            def migrate(x)
+              change_column :testings, :foo, :string, limit: 10, null: false, default: "foobar"
+            end
+          }.new
+
+          Testing.create!
+          ActiveRecord::Migrator.new(:up, [migration]).migrate
+          assert_equal ["foobar"], Testing.all.map(&:foo)
+        ensure
+          ActiveRecord::Base.clear_cache!
+        end
+      end
     end
   end
 end
 
-class LegacyPrimaryKeyTest < ActiveRecord::TestCase
+module LegacyPrimaryKeyTestCases
   include SchemaDumpingHelper
 
-  self.use_transactional_tests = false
-
   class LegacyPrimaryKey < ActiveRecord::Base
   end
 
@@ -152,7 +169,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   end
 
   def test_legacy_primary_key_should_be_auto_incremented
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_table :legacy_primary_keys do |t|
           t.references :legacy_ref
@@ -182,7 +199,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   def test_legacy_integer_primary_key_should_not_be_auto_incremented
     skip if current_adapter?(:SQLite3Adapter)
 
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_table :legacy_primary_keys, id: :integer do |t|
         end
@@ -199,9 +216,90 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     assert_match %r{create_table "legacy_primary_keys", id: :integer, default: nil}, schema
   end
 
+  if current_adapter?(:Mysql2Adapter, :PostgreSQLAdapter)
+    def test_legacy_primary_key_in_create_table_should_be_integer
+      @migration = Class.new(migration_class) {
+        def change
+          create_table :legacy_primary_keys, id: false do |t|
+            t.primary_key :id
+          end
+        end
+      }.new
+
+      @migration.migrate(:up)
+
+      schema = dump_table_schema "legacy_primary_keys"
+      assert_match %r{create_table "legacy_primary_keys", id: :(?:integer|serial), (?!default: nil)}, schema
+    end
+
+    def test_legacy_primary_key_in_change_table_should_be_integer
+      @migration = Class.new(migration_class) {
+        def change
+          create_table :legacy_primary_keys, id: false do |t|
+            t.integer :dummy
+          end
+          change_table :legacy_primary_keys do |t|
+            t.primary_key :id
+          end
+        end
+      }.new
+
+      @migration.migrate(:up)
+
+      schema = dump_table_schema "legacy_primary_keys"
+      assert_match %r{create_table "legacy_primary_keys", id: :(?:integer|serial), (?!default: nil)}, schema
+    end
+
+    def test_add_column_with_legacy_primary_key_should_be_integer
+      @migration = Class.new(migration_class) {
+        def change
+          create_table :legacy_primary_keys, id: false do |t|
+            t.integer :dummy
+          end
+          add_column :legacy_primary_keys, :id, :primary_key
+        end
+      }.new
+
+      @migration.migrate(:up)
+
+      schema = dump_table_schema "legacy_primary_keys"
+      assert_match %r{create_table "legacy_primary_keys", id: :(?:integer|serial), (?!default: nil)}, schema
+    end
+  end
+
+  def test_legacy_join_table_foreign_keys_should_be_integer
+    @migration = Class.new(migration_class) {
+      def change
+        create_join_table :apples, :bananas do |t|
+        end
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    schema = dump_table_schema "apples_bananas"
+    assert_match %r{integer "apple_id", null: false}, schema
+    assert_match %r{integer "banana_id", null: false}, schema
+  end
+
+  def test_legacy_join_table_column_options_should_be_overwritten
+    @migration = Class.new(migration_class) {
+      def change
+        create_join_table :apples, :bananas, column_options: { type: :bigint } do |t|
+        end
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    schema = dump_table_schema "apples_bananas"
+    assert_match %r{bigint "apple_id", null: false}, schema
+    assert_match %r{bigint "banana_id", null: false}, schema
+  end
+
   if current_adapter?(:Mysql2Adapter)
     def test_legacy_bigint_primary_key_should_be_auto_incremented
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: :bigint
         end
@@ -218,7 +316,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     end
   else
     def test_legacy_bigint_primary_key_should_not_be_auto_incremented
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: :bigint do |t|
           end
@@ -236,3 +334,27 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     end
   end
 end
+
+module LegacyPrimaryKeyTest
+  class V5_0 < ActiveRecord::TestCase
+    include LegacyPrimaryKeyTestCases
+
+    self.use_transactional_tests = false
+
+    private
+      def migration_class
+        ActiveRecord::Migration[5.0]
+      end
+  end
+
+  class V4_2 < ActiveRecord::TestCase
+    include LegacyPrimaryKeyTestCases
+
+    self.use_transactional_tests = false
+
+    private
+      def migration_class
+        ActiveRecord::Migration[4.2]
+      end
+  end
+end
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index 499d072de5..079be04946 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -227,6 +227,74 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           end
         end
 
+        if ActiveRecord::Base.connection.supports_validate_constraints?
+          def test_add_invalid_foreign_key
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
+
+            foreign_keys = @connection.foreign_keys("astronauts")
+            assert_equal 1, foreign_keys.size
+
+            fk = foreign_keys.first
+            refute fk.validated?
+          end
+
+          def test_validate_foreign_key_infers_column
+            @connection.add_foreign_key :astronauts, :rockets, validate: false
+            refute @connection.foreign_keys("astronauts").first.validated?
+
+            @connection.validate_foreign_key :astronauts, :rockets
+            assert @connection.foreign_keys("astronauts").first.validated?
+          end
+
+          def test_validate_foreign_key_by_column
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
+            refute @connection.foreign_keys("astronauts").first.validated?
+
+            @connection.validate_foreign_key :astronauts, column: "rocket_id"
+            assert @connection.foreign_keys("astronauts").first.validated?
+          end
+
+          def test_validate_foreign_key_by_symbol_column
+            @connection.add_foreign_key :astronauts, :rockets, column: :rocket_id, validate: false
+            refute @connection.foreign_keys("astronauts").first.validated?
+
+            @connection.validate_foreign_key :astronauts, column: :rocket_id
+            assert @connection.foreign_keys("astronauts").first.validated?
+          end
+
+          def test_validate_foreign_key_by_name
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk", validate: false
+            refute @connection.foreign_keys("astronauts").first.validated?
+
+            @connection.validate_foreign_key :astronauts, name: "fancy_named_fk"
+            assert @connection.foreign_keys("astronauts").first.validated?
+          end
+
+          def test_validate_foreign_non_existing_foreign_key_raises
+            assert_raises ArgumentError do
+              @connection.validate_foreign_key :astronauts, :rockets
+            end
+          end
+
+          def test_validate_constraint_by_name
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk", validate: false
+
+            @connection.validate_constraint :astronauts, "fancy_named_fk"
+            assert @connection.foreign_keys("astronauts").first.validated?
+          end
+        else
+          # Foreign key should still be created, but should not be invalid
+          def test_add_invalid_foreign_key
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
+
+            foreign_keys = @connection.foreign_keys("astronauts")
+            assert_equal 1, foreign_keys.size
+
+            fk = foreign_keys.first
+            assert fk.validated?
+          end
+        end
+
         def test_schema_dumping
           @connection.add_foreign_key :astronauts, :rockets
           output = dump_table_schema "astronauts"
diff --git a/activerecord/test/cases/migration/index_test.rb b/activerecord/test/cases/migration/index_test.rb
index bf1ebdb4c5..b25c6d84bc 100644
--- a/activerecord/test/cases/migration/index_test.rb
+++ b/activerecord/test/cases/migration/index_test.rb
@@ -33,10 +33,8 @@ module ActiveRecord
         connection.add_index(table_name, [:foo], name: "old_idx")
         connection.rename_index(table_name, "old_idx", "new_idx")
 
-        assert_deprecated do
-          assert_not connection.index_name_exists?(table_name, "old_idx", false)
-          assert connection.index_name_exists?(table_name, "new_idx", true)
-        end
+        assert_not connection.index_name_exists?(table_name, "old_idx")
+        assert connection.index_name_exists?(table_name, "new_idx")
       end
 
       def test_rename_index_too_long
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index 07afa89779..b18af2ab55 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -1106,17 +1106,4 @@ class CopyMigrationsTest < ActiveRecord::TestCase
   def test_unknown_migration_version_should_raise_an_argument_error
     assert_raise(ArgumentError) { ActiveRecord::Migration[1.0] }
   end
-
-  def test_deprecate_initialize_internal_tables
-    assert_deprecated { ActiveRecord::Base.connection.initialize_schema_migrations_table }
-    assert_deprecated { ActiveRecord::Base.connection.initialize_internal_metadata_table }
-  end
-
-  def test_deprecate_supports_migrations
-    assert_deprecated { ActiveRecord::Base.connection.supports_migrations? }
-  end
-
-  def test_deprecate_schema_migrations_table_name
-    assert_deprecated { ActiveRecord::Migrator.schema_migrations_table_name }
-  end
 end
diff --git a/activerecord/test/cases/migrator_test.rb b/activerecord/test/cases/migrator_test.rb
index ee10be119c..1047ba1367 100644
--- a/activerecord/test/cases/migrator_test.rb
+++ b/activerecord/test/cases/migrator_test.rb
@@ -66,6 +66,26 @@ class MigratorTest < ActiveRecord::TestCase
       list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
       ActiveRecord::Migrator.new(:up, list, 3).run
     end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, -1).run
+    end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, 0).run
+    end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, 3).migrate
+    end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, -1).migrate
+    end
   end
 
   def test_finds_migrations
diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 170fd02b6f..4cc66a2e49 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -73,17 +73,39 @@ class PersistenceTest < ActiveRecord::TestCase
     topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" } }
     updated = Topic.update(topic_data.keys, topic_data.values)
 
-    assert_equal 2, updated.size
+    assert_equal [1, 2], updated.map(&:id)
     assert_equal "1 updated", Topic.find(1).content
     assert_equal "2 updated", Topic.find(2).content
   end
 
+  def test_update_many_with_duplicated_ids
+    updated = Topic.update([1, 1, 2], [
+      { "content" => "1 duplicated" }, { "content" => "1 updated" }, { "content" => "2 updated" }
+    ])
+
+    assert_equal [1, 1, 2], updated.map(&:id)
+    assert_equal "1 updated", Topic.find(1).content
+    assert_equal "2 updated", Topic.find(2).content
+  end
+
+  def test_update_many_with_invalid_id
+    topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" }, 99999 => {} }
+
+    assert_raise(ActiveRecord::RecordNotFound) do
+      Topic.update(topic_data.keys, topic_data.values)
+    end
+
+    assert_not_equal "1 updated", Topic.find(1).content
+    assert_not_equal "2 updated", Topic.find(2).content
+  end
+
   def test_class_level_update_is_affected_by_scoping
     topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" } }
 
     assert_raise(ActiveRecord::RecordNotFound) do
       Topic.where("1=0").scoping { Topic.update(topic_data.keys, topic_data.values) }
     end
+
     assert_not_equal "1 updated", Topic.find(1).content
     assert_not_equal "2 updated", Topic.find(2).content
   end
@@ -95,27 +117,31 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_delete_all_with_joins_and_where_part_is_hash
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.joins(:toys).where(where_args).count
+    pets = Pet.joins(:toys).where(toys: { name: "Bone" })
+
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
+  end
+
+  def test_delete_all_with_joins_and_where_part_is_not_hash
+    pets = Pet.joins(:toys).where("toys.name = ?", "Bone")
 
-    assert_equal count, 1
-    assert_equal count, Pet.joins(:toys).where(where_args).delete_all
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
   end
 
   def test_delete_all_with_left_joins
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.left_joins(:toys).where(where_args).count
+    pets = Pet.left_joins(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, 1
-    assert_equal count, Pet.left_joins(:toys).where(where_args).delete_all
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
   end
 
-  def test_delete_all_with_joins_and_where_part_is_not_hash
-    where_args = ["toys.name = ?", "Bone"]
-    count = Pet.joins(:toys).where(where_args).count
+  def test_delete_all_with_includes
+    pets = Pet.includes(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, 1
-    assert_equal count, Pet.joins(:toys).where(where_args).delete_all
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
   end
 
   def test_increment_attribute
@@ -172,15 +198,25 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_destroy_many
-    clients = Client.all.merge!(order: "id").find([2, 3])
+    clients = Client.find([2, 3])
 
     assert_difference("Client.count", -2) do
-      destroyed = Client.destroy([2, 3]).sort_by(&:id)
+      destroyed = Client.destroy([2, 3])
       assert_equal clients, destroyed
       assert destroyed.all?(&:frozen?), "destroyed clients should be frozen"
     end
   end
 
+  def test_destroy_many_with_invalid_id
+    clients = Client.find([2, 3])
+
+    assert_raise(ActiveRecord::RecordNotFound) do
+      Client.destroy([2, 3, 99999])
+    end
+
+    assert_equal clients, Client.find([2, 3])
+  end
+
   def test_becomes
     assert_kind_of Reply, topics(:first).becomes(Reply)
     assert_equal "The First Topic", topics(:first).becomes(Reply).title
@@ -470,10 +506,18 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(topic.id) }
   end
 
-  def test_record_not_found_exception
+  def test_find_raises_record_not_found_exception
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(99999) }
   end
 
+  def test_update_raises_record_not_found_exception
+    assert_raise(ActiveRecord::RecordNotFound) { Topic.update(99999, approved: true) }
+  end
+
+  def test_destroy_raises_record_not_found_exception
+    assert_raise(ActiveRecord::RecordNotFound) { Topic.destroy(99999) }
+  end
+
   def test_update_all
     assert_equal Topic.count, Topic.update_all("content = 'bulk updated!'")
     assert_equal "bulk updated!", Topic.find(1).content
@@ -497,17 +541,24 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_update_all_with_joins
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.left_joins(:toys).where(where_args).count
+    pets = Pet.joins(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, Pet.joins(:toys).where(where_args).update_all(name: "Bob")
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.update_all(name: "Bob")
   end
 
   def test_update_all_with_left_joins
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.left_joins(:toys).where(where_args).count
+    pets = Pet.left_joins(:toys).where(toys: { name: "Bone" })
+
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.update_all(name: "Bob")
+  end
+
+  def test_update_all_with_includes
+    pets = Pet.includes(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, Pet.left_joins(:toys).where(where_args).update_all(name: "Bob")
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.update_all(name: "Bob")
   end
 
   def test_update_all_with_non_standard_table_name
@@ -917,7 +968,9 @@ class PersistenceTest < ActiveRecord::TestCase
     should_be_destroyed_reply = Reply.create("title" => "hello", "content" => "world")
     Topic.find(1).replies << should_be_destroyed_reply
 
-    Topic.destroy(1)
+    topic = Topic.destroy(1)
+    assert topic.destroyed?
+
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(1) }
     assert_raise(ActiveRecord::RecordNotFound) { Reply.find(should_be_destroyed_reply.id) }
   end
@@ -929,6 +982,7 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::RecordNotFound) do
       Topic.where("1=0").scoping { Topic.destroy(1) }
     end
+
     assert_nothing_raised { Topic.find(1) }
     assert_nothing_raised { Reply.find(should_not_be_destroyed_reply.id) }
   end
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index a36d786b40..7f6c2382ca 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -156,10 +156,6 @@ class PrimaryKeysTest < ActiveRecord::TestCase
     assert_nothing_raised { MixedCaseMonkey.find(1).destroy }
   end
 
-  def test_deprecate_supports_primary_key
-    assert_deprecated { ActiveRecord::Base.connection.supports_primary_key? }
-  end
-
   def test_primary_key_returns_value_if_it_exists
     klass = Class.new(ActiveRecord::Base) do
       self.table_name = "developers"
diff --git a/activerecord/test/cases/query_cache_test.rb b/activerecord/test/cases/query_cache_test.rb
index 5cb537b623..46f90b0bca 100644
--- a/activerecord/test/cases/query_cache_test.rb
+++ b/activerecord/test/cases/query_cache_test.rb
@@ -452,6 +452,15 @@ class QueryCacheTest < ActiveRecord::TestCase
     end
   end
 
+  def test_query_cache_is_enabled_on_all_connection_pools
+    middleware {
+      ActiveRecord::Base.connection_handler.connection_pool_list.each do |pool|
+        assert pool.query_cache_enabled
+        assert pool.connection.query_cache_enabled
+      end
+    }.call({})
+  end
+
   private
     def middleware(&app)
       executor = Class.new(ActiveSupport::Executor)
diff --git a/activerecord/test/cases/quoting_test.rb b/activerecord/test/cases/quoting_test.rb
index 59d3bbb573..897d252cf8 100644
--- a/activerecord/test/cases/quoting_test.rb
+++ b/activerecord/test/cases/quoting_test.rb
@@ -83,23 +83,6 @@ module ActiveRecord
         end
       end
 
-      class QuotedOne
-        def quoted_id
-          1
-        end
-      end
-      class SubQuotedOne < QuotedOne
-      end
-      def test_quote_with_quoted_id
-        assert_deprecated(/defined on \S+::QuotedOne at .*quoting_test\.rb:[0-9]/) do
-          assert_equal 1, @quoter.quote(QuotedOne.new)
-        end
-
-        assert_deprecated(/defined on \S+::SubQuotedOne\(\S+::QuotedOne\) at .*quoting_test\.rb:[0-9]/) do
-          assert_equal 1, @quoter.quote(SubQuotedOne.new)
-        end
-      end
-
       def test_quote_nil
         assert_equal "NULL", @quoter.quote(nil)
       end
@@ -207,26 +190,6 @@ module ActiveRecord
         obj = Class.new.new
         assert_raise(TypeError) { @conn.type_cast(obj) }
       end
-
-      def test_type_cast_object_which_responds_to_quoted_id
-        quoted_id_obj = Class.new {
-          def quoted_id
-            "'zomg'"
-          end
-
-          def id
-            10
-          end
-        }.new
-        assert_equal 10, @conn.type_cast(quoted_id_obj)
-
-        quoted_id_obj = Class.new {
-          def quoted_id
-            "'zomg'"
-          end
-        }.new
-        assert_raise(TypeError) { @conn.type_cast(quoted_id_obj) }
-      end
     end
 
     class QuoteBooleanTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/reaper_test.rb b/activerecord/test/cases/reaper_test.rb
index 49170abe6f..6c7727ab1b 100644
--- a/activerecord/test/cases/reaper_test.rb
+++ b/activerecord/test/cases/reaper_test.rb
@@ -18,6 +18,7 @@ module ActiveRecord
 
       class FakePool
         attr_reader :reaped
+        attr_reader :flushed
 
         def initialize
           @reaped = false
@@ -26,6 +27,10 @@ module ActiveRecord
         def reap
           @reaped = true
         end
+
+        def flush
+          @flushed = true
+        end
       end
 
       # A reaper with nil time should never reap connections
@@ -47,6 +52,7 @@ module ActiveRecord
           Thread.pass
         end
         assert fp.reaped
+        assert fp.flushed
       end
 
       def test_pool_has_reaper
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index 4cd2d3aedc..37c2235f1a 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -25,7 +25,6 @@ require "models/chef"
 require "models/department"
 require "models/cake_designer"
 require "models/drink_designer"
-require "models/mocktail_designer"
 require "models/recipe"
 
 class ReflectionTest < ActiveRecord::TestCase
@@ -254,32 +253,6 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal expected, actual
   end
 
-  def test_scope_chain
-    expected = [
-      [Tagging.reflect_on_association(:tag).scope, Post.reflect_on_association(:first_blue_tags).scope],
-      [Post.reflect_on_association(:first_taggings).scope],
-      [Author.reflect_on_association(:misc_posts).scope]
-    ]
-    actual = assert_deprecated do
-      Author.reflect_on_association(:misc_post_first_blue_tags).scope_chain
-    end
-    assert_equal expected, actual
-
-    expected = [
-      [
-        Tagging.reflect_on_association(:blue_tag).scope,
-        Post.reflect_on_association(:first_blue_tags_2).scope,
-        Author.reflect_on_association(:misc_post_first_blue_tags_2).scope
-      ],
-      [],
-      []
-    ]
-    actual = assert_deprecated do
-      Author.reflect_on_association(:misc_post_first_blue_tags_2).scope_chain
-    end
-    assert_equal expected, actual
-  end
-
   def test_scope_chain_does_not_interfere_with_hmt_with_polymorphic_case
     @hotel = Hotel.create!
     @department = @hotel.departments.create!
@@ -366,9 +339,16 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::UnknownPrimaryKey) { reflection.active_record_primary_key }
   end
 
+  def test_type
+    assert_equal "taggable_type", Post.reflect_on_association(:taggings).type.to_s
+    assert_equal "imageable_class", Post.reflect_on_association(:images).type.to_s
+    assert_nil Post.reflect_on_association(:readers).type
+  end
+
   def test_foreign_type
     assert_equal "sponsorable_type", Sponsor.reflect_on_association(:sponsorable).foreign_type.to_s
     assert_equal "sponsorable_type", Sponsor.reflect_on_association(:thing).foreign_type.to_s
+    assert_nil Sponsor.reflect_on_association(:sponsor_club).foreign_type
   end
 
   def test_collection_association
@@ -409,26 +389,15 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal "category_id", Post.reflect_on_association(:categorizations).foreign_key.to_s
   end
 
-  def test_through_reflection_scope_chain_does_not_modify_other_reflections
-    orig_conds = assert_deprecated do
-      Post.reflect_on_association(:first_blue_tags_2).scope_chain
-    end.inspect
-    assert_deprecated do
-      Author.reflect_on_association(:misc_post_first_blue_tags_2).scope_chain
-    end
-    assert_equal orig_conds, assert_deprecated {
-      Post.reflect_on_association(:first_blue_tags_2).scope_chain
-    }.inspect
-  end
-
   def test_symbol_for_class_name
     assert_equal Client, Firm.reflect_on_association(:unsorted_clients_with_symbol).klass
   end
 
   def test_class_for_class_name
-    assert_deprecated do
-      assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm), :validate?
+    error = assert_raises(ArgumentError) do
+      ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm)
     end
+    assert_equal "A class was passed to `:class_name` but we are expecting a string.", error.message
   end
 
   def test_join_table
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index fd5985ffe7..b424ca91de 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -68,7 +68,7 @@ module ActiveRecord
       relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
       left     = relation.table[:id].eq(10)
       right    = relation.table[:id].eq(10)
-      combine  = left.and right
+      combine  = left.or(right)
       relation.where! combine
       assert_equal({}, relation.where_values_hash)
     end
@@ -274,18 +274,32 @@ module ActiveRecord
       assert_equal({ 2 => 1, 4 => 3, 5 => 1 }, authors(:david).posts.merge(posts_with_special_comments_with_ratings).count)
     end
 
+    def test_relation_merging_keeps_joining_order
+      authors  = Author.where(id: 1)
+      posts    = Post.joins(:author).merge(authors)
+      comments = Comment.joins(:post).merge(posts)
+      ratings  = Rating.joins(:comment).merge(comments)
+
+      assert_equal 3, ratings.count
+    end
+
     class EnsureRoundTripTypeCasting < ActiveRecord::Type::Value
       def type
         :string
       end
 
+      def cast(value)
+        raise value unless value == "value from user"
+        "cast value"
+      end
+
       def deserialize(value)
         raise value unless value == "type cast for database"
         "type cast from database"
       end
 
       def serialize(value)
-        raise value unless value == "value from user"
+        raise value unless value == "cast value"
         "type cast for database"
       end
     end
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index ae1dc35bff..675aafabda 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -19,12 +19,12 @@ require "models/tyre"
 require "models/minivan"
 require "models/possession"
 require "models/reader"
+require "models/category"
 require "models/categorization"
 require "models/edge"
 
 class RelationTest < ActiveRecord::TestCase
-  fixtures :authors, :author_addresses, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :posts, :comments,
-    :tags, :taggings, :cars, :minivans
+  fixtures :authors, :author_addresses, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :categories_posts, :posts, :comments, :tags, :taggings, :cars, :minivans
 
   class TopicWithCallbacks < ActiveRecord::Base
     self.table_name = :topics
@@ -195,6 +195,18 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal(relation.map(&:post_count).sort, subquery.values.sort)
   end
 
+  def test_finding_with_subquery_with_eager_loading_in_from
+    relation = Comment.includes(:post).where("posts.type": "Post")
+    assert_equal relation.to_a, Comment.select("*").from(relation).to_a
+    assert_equal relation.to_a, Comment.select("subquery.*").from(relation).to_a
+    assert_equal relation.to_a, Comment.select("a.*").from(relation, :a).to_a
+  end
+
+  def test_finding_with_subquery_with_eager_loading_in_where
+    relation = Comment.includes(:post).where("posts.type": "Post")
+    assert_equal relation.sort_by(&:id), Comment.where(id: relation).sort_by(&:id)
+  end
+
   def test_finding_with_conditions
     assert_equal ["David"], Author.where(name: "David").map(&:name)
     assert_equal ["Mary"],  Author.where(["name = ?", "Mary"]).map(&:name)
@@ -238,7 +250,7 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_reverse_order_with_function
-    topics = Topic.order("length(title)").reverse_order
+    topics = Topic.order(Arel.sql("length(title)")).reverse_order
     assert_equal topics(:second).title, topics.first.title
   end
 
@@ -248,24 +260,24 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_reverse_order_with_function_other_predicates
-    topics = Topic.order("author_name, length(title), id").reverse_order
+    topics = Topic.order(Arel.sql("author_name, length(title), id")).reverse_order
     assert_equal topics(:second).title, topics.first.title
-    topics = Topic.order("length(author_name), id, length(title)").reverse_order
+    topics = Topic.order(Arel.sql("length(author_name), id, length(title)")).reverse_order
     assert_equal topics(:fifth).title, topics.first.title
   end
 
   def test_reverse_order_with_multiargument_function
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(author_name, title)").reverse_order
+      Topic.order(Arel.sql("concat(author_name, title)")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(lower(author_name), title)").reverse_order
+      Topic.order(Arel.sql("concat(lower(author_name), title)")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(author_name, lower(title))").reverse_order
+      Topic.order(Arel.sql("concat(author_name, lower(title))")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(lower(author_name), title, length(title)").reverse_order
+      Topic.order(Arel.sql("concat(lower(author_name), title, length(title)")).reverse_order
     end
   end
 
@@ -277,10 +289,10 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_reverse_order_with_nulls_first_or_last
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("title NULLS FIRST").reverse_order
+      Topic.order(Arel.sql("title NULLS FIRST")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("title nulls last").reverse_order
+      Topic.order(Arel.sql("title nulls last")).reverse_order
     end
   end
 
@@ -373,29 +385,29 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_finding_with_cross_table_order_and_limit
     tags = Tag.includes(:taggings).
-              order("tags.name asc", "taggings.taggable_id asc", "REPLACE('abc', taggings.taggable_type, taggings.taggable_type)").
+              order("tags.name asc", "taggings.taggable_id asc", Arel.sql("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)")).
               limit(1).to_a
     assert_equal 1, tags.length
   end
 
   def test_finding_with_complex_order_and_limit
-    tags = Tag.includes(:taggings).references(:taggings).order("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)").limit(1).to_a
+    tags = Tag.includes(:taggings).references(:taggings).order(Arel.sql("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)")).limit(1).to_a
     assert_equal 1, tags.length
   end
 
   def test_finding_with_complex_order
-    tags = Tag.includes(:taggings).references(:taggings).order("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)").to_a
+    tags = Tag.includes(:taggings).references(:taggings).order(Arel.sql("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)")).to_a
     assert_equal 3, tags.length
   end
 
   def test_finding_with_sanitized_order
-    query = Tag.order(["field(id, ?)", [1, 3, 2]]).to_sql
+    query = Tag.order([Arel.sql("field(id, ?)"), [1, 3, 2]]).to_sql
     assert_match(/field\(id, 1,3,2\)/, query)
 
-    query = Tag.order(["field(id, ?)", []]).to_sql
+    query = Tag.order([Arel.sql("field(id, ?)"), []]).to_sql
     assert_match(/field\(id, NULL\)/, query)
 
-    query = Tag.order(["field(id, ?)", nil]).to_sql
+    query = Tag.order([Arel.sql("field(id, ?)"), nil]).to_sql
     assert_match(/field\(id, NULL\)/, query)
   end
 
@@ -845,32 +857,6 @@ class RelationTest < ActiveRecord::TestCase
     }
   end
 
-  def test_exists
-    davids = Author.where(name: "David")
-    assert davids.exists?
-    assert davids.exists?(authors(:david).id)
-    assert ! davids.exists?(authors(:mary).id)
-    assert ! davids.exists?("42")
-    assert ! davids.exists?(42)
-    assert ! davids.exists?(davids.new.id)
-
-    fake = Author.where(name: "fake author")
-    assert ! fake.exists?
-    assert ! fake.exists?(authors(:david).id)
-  end
-
-  def test_exists_uses_existing_scope
-    post = authors(:david).posts.first
-    authors = Author.includes(:posts).where(name: "David", posts: { id: post.id })
-    assert authors.exists?(authors(:david).id)
-  end
-
-  def test_any_with_scope_on_hash_includes
-    post = authors(:david).posts.first
-    categories = Categorization.includes(author: :posts).where(posts: { id: post.id })
-    assert categories.exists?
-  end
-
   def test_last
     authors = Author.all
     assert_equal authors(:bob), authors.last
@@ -953,13 +939,13 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal 11, posts.count(:all)
     assert_equal 11, posts.count(:id)
 
-    assert_equal 1, posts.where("comments_count > 1").count
-    assert_equal 9, posts.where(comments_count: 0).count
+    assert_equal 3, posts.where("comments_count > 1").count
+    assert_equal 6, posts.where(comments_count: 0).count
   end
 
   def test_count_with_block
     posts = Post.all
-    assert_equal 10, posts.count { |p| p.comments_count.even? }
+    assert_equal 8, posts.count { |p| p.comments_count.even? }
   end
 
   def test_count_on_association_relation
@@ -976,10 +962,10 @@ class RelationTest < ActiveRecord::TestCase
   def test_count_with_distinct
     posts = Post.all
 
-    assert_equal 3, posts.distinct(true).count(:comments_count)
+    assert_equal 4, posts.distinct(true).count(:comments_count)
     assert_equal 11, posts.distinct(false).count(:comments_count)
 
-    assert_equal 3, posts.distinct(true).select(:comments_count).count
+    assert_equal 4, posts.distinct(true).select(:comments_count).count
     assert_equal 11, posts.distinct(false).select(:comments_count).count
   end
 
@@ -1018,7 +1004,7 @@ class RelationTest < ActiveRecord::TestCase
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
-    assert_no_queries { assert_equal 9, best_posts.size }
+    assert_no_queries { assert_equal 6, best_posts.size }
   end
 
   def test_size_with_limit
@@ -1029,7 +1015,7 @@ class RelationTest < ActiveRecord::TestCase
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
-    assert_no_queries { assert_equal 9, best_posts.size }
+    assert_no_queries { assert_equal 6, best_posts.size }
   end
 
   def test_size_with_zero_limit
@@ -1052,7 +1038,7 @@ class RelationTest < ActiveRecord::TestCase
   def test_count_complex_chained_relations
     posts = Post.select("comments_count").where("id is not null").group("author_id").where("comments_count > 0")
 
-    expected = { 1 => 2 }
+    expected = { 1 => 4, 2 => 1 }
     assert_equal expected, posts.count
   end
 
@@ -1203,6 +1189,15 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal "hen", hen.name
   end
 
+  def test_create_with_polymorphic_association
+    author = authors(:david)
+    post = posts(:welcome)
+    comment = Comment.where(post: post, author: author).create!(body: "hello")
+
+    assert_equal author, comment.author
+    assert_equal post, comment.post
+  end
+
   def test_first_or_create
     parrot = Bird.where(color: "green").first_or_create(name: "parrot")
     assert_kind_of Bird, parrot
@@ -1593,7 +1588,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.order("comments.body")
     assert_equal ["comments"], scope.references_values
 
-    scope = Post.order("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}")
+    scope = Post.order(Arel.sql("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}"))
     if current_adapter?(:OracleAdapter)
       assert_equal ["COMMENTS"], scope.references_values
     else
@@ -1610,7 +1605,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.order("comments.body asc")
     assert_equal ["comments"], scope.references_values
 
-    scope = Post.order("foo(comments.body)")
+    scope = Post.order(Arel.sql("foo(comments.body)"))
     assert_equal [], scope.references_values
   end
 
@@ -1618,7 +1613,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.reorder("comments.body")
     assert_equal %w(comments), scope.references_values
 
-    scope = Post.reorder("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}")
+    scope = Post.reorder(Arel.sql("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}"))
     if current_adapter?(:OracleAdapter)
       assert_equal ["COMMENTS"], scope.references_values
     else
@@ -1635,7 +1630,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.reorder("comments.body asc")
     assert_equal %w(comments), scope.references_values
 
-    scope = Post.reorder("foo(comments.body)")
+    scope = Post.reorder(Arel.sql("foo(comments.body)"))
     assert_equal [], scope.references_values
   end
 
@@ -1806,6 +1801,14 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal post, custom_post_relation.joins(:author).where!(title: post.title).take
   end
 
+  test "arel_attribute respects a custom table" do
+    assert_equal [posts(:sti_comments)], custom_post_relation.ranked_by_comments.limit_by(1).to_a
+  end
+
+  test "alias_tracker respects a custom table" do
+    assert_equal posts(:welcome), custom_post_relation("categories_posts").joins(:categories).first
+  end
+
   test "#load" do
     relation = Post.all
     assert_queries(1) do
@@ -1912,9 +1915,22 @@ class RelationTest < ActiveRecord::TestCase
     end
   end
 
+  test "#where with set" do
+    david = authors(:david)
+    mary = authors(:mary)
+
+    authors = Author.where(name: ["David", "Mary"].to_set)
+    assert_equal [david, mary], authors
+  end
+
+  test "#where with empty set" do
+    authors = Author.where(name: Set.new)
+    assert_empty authors
+  end
+
   private
-    def custom_post_relation
-      table_alias = Post.arel_table.alias("omg_posts")
+    def custom_post_relation(alias_name = "omg_posts")
+      table_alias = Post.arel_table.alias(alias_name)
       table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
       predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
 
diff --git a/activerecord/test/cases/sanitize_test.rb b/activerecord/test/cases/sanitize_test.rb
index 082d663675..85a555fe35 100644
--- a/activerecord/test/cases/sanitize_test.rb
+++ b/activerecord/test/cases/sanitize_test.rb
@@ -153,18 +153,6 @@ class SanitizeTest < ActiveRecord::TestCase
     assert_equal "name=#{quoted_bambi_and_thumper}", bind("name=?", "Bambi\nand\nThumper".mb_chars)
   end
 
-  def test_bind_record
-    o = Class.new {
-      def quoted_id
-        1
-      end
-    }.new
-    assert_deprecated { assert_equal "1", bind("?", o) }
-
-    os = [o] * 3
-    assert_deprecated { assert_equal "1,1,1", bind("?", os) }
-  end
-
   def test_named_bind_with_postgresql_type_casts
     l = Proc.new { bind(":a::integer '2009-01-01'::date", a: "10") }
     assert_nothing_raised(&l)
diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index 799a65c61e..a612ce9bb2 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -177,14 +177,14 @@ class SchemaDumperTest < ActiveRecord::TestCase
 
   def test_schema_dumps_index_columns_in_right_order
     index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*company_index/).first.strip
-    if current_adapter?(:PostgreSQLAdapter)
-      assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", order: { rating: :desc }', index_definition
-    elsif current_adapter?(:Mysql2Adapter)
+    if current_adapter?(:Mysql2Adapter)
       if ActiveRecord::Base.connection.supports_index_sort_order?
         assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", length: { type: 10 }, order: { rating: :desc }', index_definition
       else
         assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", length: { type: 10 }', index_definition
       end
+    elsif ActiveRecord::Base.connection.supports_index_sort_order?
+      assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", order: { rating: :desc }', index_definition
     else
       assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index"', index_definition
     end
@@ -199,6 +199,24 @@ class SchemaDumperTest < ActiveRecord::TestCase
     end
   end
 
+  def test_schema_dumps_index_sort_order
+    index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*_name_and_rating/).first.strip
+    if ActiveRecord::Base.connection.supports_index_sort_order?
+      assert_equal 't.index ["name", "rating"], name: "index_companies_on_name_and_rating", order: :desc', index_definition
+    else
+      assert_equal 't.index ["name", "rating"], name: "index_companies_on_name_and_rating"', index_definition
+    end
+  end
+
+  def test_schema_dumps_index_length
+    index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*_name_and_description/).first.strip
+    if current_adapter?(:Mysql2Adapter)
+      assert_equal 't.index ["name", "description"], name: "index_companies_on_name_and_description", length: 10', index_definition
+    else
+      assert_equal 't.index ["name", "description"], name: "index_companies_on_name_and_description"', index_definition
+    end
+  end
+
   def test_schema_dump_should_honor_nonstandard_primary_keys
     output = standard_dump
     match = output.match(%r{create_table "movies"(.*)do})
@@ -294,34 +312,32 @@ class SchemaDumperTest < ActiveRecord::TestCase
       assert_match %r{t\.oid\s+"obj_id"$}, output
     end
 
-    if ActiveRecord::Base.connection.supports_extensions?
-      def test_schema_dump_includes_extensions
-        connection = ActiveRecord::Base.connection
+    def test_schema_dump_includes_extensions
+      connection = ActiveRecord::Base.connection
 
-        connection.stubs(:extensions).returns(["hstore"])
-        output = perform_schema_dump
-        assert_match "# These are extensions that must be enabled", output
-        assert_match %r{enable_extension "hstore"}, output
+      connection.stubs(:extensions).returns(["hstore"])
+      output = perform_schema_dump
+      assert_match "# These are extensions that must be enabled", output
+      assert_match %r{enable_extension "hstore"}, output
 
-        connection.stubs(:extensions).returns([])
-        output = perform_schema_dump
-        assert_no_match "# These are extensions that must be enabled", output
-        assert_no_match %r{enable_extension}, output
-      end
+      connection.stubs(:extensions).returns([])
+      output = perform_schema_dump
+      assert_no_match "# These are extensions that must be enabled", output
+      assert_no_match %r{enable_extension}, output
+    end
 
-      def test_schema_dump_includes_extensions_in_alphabetic_order
-        connection = ActiveRecord::Base.connection
+    def test_schema_dump_includes_extensions_in_alphabetic_order
+      connection = ActiveRecord::Base.connection
 
-        connection.stubs(:extensions).returns(["hstore", "uuid-ossp", "xml2"])
-        output = perform_schema_dump
-        enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
-        assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
+      connection.stubs(:extensions).returns(["hstore", "uuid-ossp", "xml2"])
+      output = perform_schema_dump
+      enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
+      assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
 
-        connection.stubs(:extensions).returns(["uuid-ossp", "xml2", "hstore"])
-        output = perform_schema_dump
-        enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
-        assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
-      end
+      connection.stubs(:extensions).returns(["uuid-ossp", "xml2", "hstore"])
+      output = perform_schema_dump
+      enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
+      assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
     end
   end
 
diff --git a/activerecord/test/cases/scoping/default_scoping_test.rb b/activerecord/test/cases/scoping/default_scoping_test.rb
index 716ca29eda..fdfeabaa3b 100644
--- a/activerecord/test/cases/scoping/default_scoping_test.rb
+++ b/activerecord/test/cases/scoping/default_scoping_test.rb
@@ -120,49 +120,49 @@ class DefaultScopingTest < ActiveRecord::TestCase
   def test_unscope_with_where_attributes
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(name: "David").unscope(where: :name).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
 
     expected_2 = Developer.order("salary DESC").collect(&:name)
     received_2 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope({ where: :name }, :select).collect(&:name)
-    assert_equal expected_2, received_2
+    assert_equal expected_2.sort, received_2.sort
 
     expected_3 = Developer.order("salary DESC").collect(&:name)
     received_3 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope(:select, :where).collect(&:name)
-    assert_equal expected_3, received_3
+    assert_equal expected_3.sort, received_3.sort
 
     expected_4 = Developer.order("salary DESC").collect(&:name)
     received_4 = DeveloperOrderedBySalary.where.not("name" => "Jamis").unscope(where: :name).collect(&:name)
-    assert_equal expected_4, received_4
+    assert_equal expected_4.sort, received_4.sort
 
     expected_5 = Developer.order("salary DESC").collect(&:name)
     received_5 = DeveloperOrderedBySalary.where.not("name" => ["Jamis", "David"]).unscope(where: :name).collect(&:name)
-    assert_equal expected_5, received_5
+    assert_equal expected_5.sort, received_5.sort
 
     expected_6 = Developer.order("salary DESC").collect(&:name)
     received_6 = DeveloperOrderedBySalary.where(Developer.arel_table["name"].eq("David")).unscope(where: :name).collect(&:name)
-    assert_equal expected_6, received_6
+    assert_equal expected_6.sort, received_6.sort
 
     expected_7 = Developer.order("salary DESC").collect(&:name)
     received_7 = DeveloperOrderedBySalary.where(Developer.arel_table[:name].eq("David")).unscope(where: :name).collect(&:name)
-    assert_equal expected_7, received_7
+    assert_equal expected_7.sort, received_7.sort
   end
 
   def test_unscope_comparison_where_clauses
     # unscoped for WHERE (`developers`.`id` <= 2)
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(id: -Float::INFINITY..2).unscope(where: :id).collect { |dev| dev.name }
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
 
     # unscoped for WHERE (`developers`.`id` < 2)
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(id: -Float::INFINITY...2).unscope(where: :id).collect { |dev| dev.name }
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_unscope_multiple_where_clauses
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(name: "Jamis").where(id: 1).unscope(where: [:name, :id]).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_unscope_string_where_clauses_involved
@@ -172,23 +172,23 @@ class DefaultScopingTest < ActiveRecord::TestCase
     dev_ordered_relation = DeveloperOrderedBySalary.where(name: "Jamis").where("created_at > ?", 1.year.ago)
     received = dev_ordered_relation.unscope(where: [:name]).collect(&:name)
 
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_unscope_with_grouping_attributes
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.group(:name).unscope(:group).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
 
     expected_2 = Developer.order("salary DESC").collect(&:name)
     received_2 = DeveloperOrderedBySalary.group("name").unscope(:group).collect(&:name)
-    assert_equal expected_2, received_2
+    assert_equal expected_2.sort, received_2.sort
   end
 
   def test_unscope_with_limit_in_query
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.limit(1).unscope(:limit).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_order_to_unscope_reordering
@@ -472,7 +472,7 @@ class DefaultScopingTest < ActiveRecord::TestCase
   test "a scope can remove the condition from the default scope" do
     scope = DeveloperCalledJamis.david2
     assert_equal 1, scope.where_clause.ast.children.length
-    assert_equal Developer.where(name: "David"), scope
+    assert_equal Developer.where(name: "David").map(&:id), scope.map(&:id)
   end
 
   def test_with_abstract_class_where_clause_should_not_be_duplicated
diff --git a/activerecord/test/cases/scoping/named_scoping_test.rb b/activerecord/test/cases/scoping/named_scoping_test.rb
index b0431a4e34..17d3f27bb1 100644
--- a/activerecord/test/cases/scoping/named_scoping_test.rb
+++ b/activerecord/test/cases/scoping/named_scoping_test.rb
@@ -151,6 +151,22 @@ class NamedScopingTest < ActiveRecord::TestCase
     assert_equal "The scope body needs to be callable.", e.message
   end
 
+  def test_scopes_name_is_relation_method
+    conflicts = [
+      :records,
+      :to_ary,
+      :to_sql,
+      :explain
+    ]
+
+    conflicts.each do |name|
+      e = assert_raises ArgumentError do
+        Class.new(Post).class_eval { scope name, -> { where(approved: true) } }
+      end
+      assert_match(/You tried to define a scope named \"#{name}\" on the model/, e.message)
+    end
+  end
+
   def test_active_records_have_scope_named__all__
     assert !Topic.all.empty?
 
diff --git a/activerecord/test/cases/scoping/relation_scoping_test.rb b/activerecord/test/cases/scoping/relation_scoping_test.rb
index f3b84d88c2..116f8e83aa 100644
--- a/activerecord/test/cases/scoping/relation_scoping_test.rb
+++ b/activerecord/test/cases/scoping/relation_scoping_test.rb
@@ -240,6 +240,20 @@ class RelationScopingTest < ActiveRecord::TestCase
     assert_nil SpecialComment.current_scope
   end
 
+  def test_scoping_respects_current_class
+    Comment.unscoped do
+      assert_equal "a comment...", Comment.all.what_are_you
+      assert_equal "a special comment...", SpecialComment.all.what_are_you
+    end
+  end
+
+  def test_scoping_respects_sti_constraint
+    Comment.unscoped do
+      assert_equal comments(:greetings), Comment.find(1)
+      assert_raises(ActiveRecord::RecordNotFound) { SpecialComment.find(1) }
+    end
+  end
+
   def test_circular_joins_with_scoping_does_not_crash
     posts = Post.joins(comments: :post).scoping do
       Post.first(10)
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index 1495d2ab89..5a094ead42 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -357,8 +357,15 @@ module ActiveRecord
       ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
       ActiveRecord::Tasks::DatabaseTasks.migrate
 
+      ENV["VERBOSE"] = ""
+      ENV["VERSION"] = ""
+      ActiveRecord::Migrator.expects(:migrate).with("custom/path", nil)
+      ActiveRecord::Migration.expects(:verbose=).with(true)
+      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
+      ActiveRecord::Tasks::DatabaseTasks.migrate
+
       ENV["VERBOSE"] = "yes"
-      ENV["VERSION"] = "unknown"
+      ENV["VERSION"] = "0"
       ActiveRecord::Migrator.expects(:migrate).with("custom/path", 0)
       ActiveRecord::Migration.expects(:verbose=).with(true)
       ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
@@ -367,15 +374,47 @@ module ActiveRecord
       ENV["VERBOSE"], ENV["VERSION"] = verbose, version
     end
 
-    def test_migrate_raise_error_on_empty_version
+    def test_migrate_raise_error_on_invalid_version_format
       version = ENV["VERSION"]
-      ENV["VERSION"] = ""
+
+      ENV["VERSION"] = "unknown"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0 "
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1."
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_"
       e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
-      assert_equal "Empty VERSION provided", e.message
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_name"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
     ensure
       ENV["VERSION"] = version
     end
 
+    def test_migrate_raise_error_on_failed_check_target_version
+      ActiveRecord::Tasks::DatabaseTasks.stubs(:check_target_version).raises("foo")
+
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_equal "foo", e.message
+    end
+
     def test_migrate_clears_schema_cache_afterward
       ActiveRecord::Base.expects(:clear_cache!)
       ActiveRecord::Tasks::DatabaseTasks.migrate
@@ -444,6 +483,108 @@ module ActiveRecord
     end
   end
 
+  class DatabaseTaskTargetVersionTest < ActiveRecord::TestCase
+    def test_target_version_returns_nil_if_version_does_not_exist
+      version = ENV.delete("VERSION")
+      assert_nil ActiveRecord::Tasks::DatabaseTasks.target_version
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_target_version_returns_nil_if_version_is_empty
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = ""
+      assert_nil ActiveRecord::Tasks::DatabaseTasks.target_version
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_target_version_returns_converted_to_integer_env_version_if_version_exists
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = "0"
+      assert_equal ENV["VERSION"].to_i, ActiveRecord::Tasks::DatabaseTasks.target_version
+
+      ENV["VERSION"] = "42"
+      assert_equal ENV["VERSION"].to_i, ActiveRecord::Tasks::DatabaseTasks.target_version
+
+      ENV["VERSION"] = "042"
+      assert_equal ENV["VERSION"].to_i, ActiveRecord::Tasks::DatabaseTasks.target_version
+    ensure
+      ENV["VERSION"] = version
+    end
+  end
+
+  class DatabaseTaskCheckTargetVersionTest < ActiveRecord::TestCase
+    def test_check_target_version_does_not_raise_error_on_empty_version
+      version = ENV["VERSION"]
+      ENV["VERSION"] = ""
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_check_target_version_does_not_raise_error_if_version_is_not_setted
+      version = ENV.delete("VERSION")
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_check_target_version_raises_error_on_invalid_version_format
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = "unknown"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0 "
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1."
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_name"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_check_target_version_does_not_raise_error_on_valid_version_format
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = "0"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+
+      ENV["VERSION"] = "1"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+
+      ENV["VERSION"] = "001"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+
+      ENV["VERSION"] = "001_name.rb"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+    ensure
+      ENV["VERSION"] = version
+    end
+  end
+
   class DatabaseTasksStructureDumpTest < ActiveRecord::TestCase
     include DatabaseTasksSetupper
 
diff --git a/activerecord/test/cases/tasks/mysql_rake_test.rb b/activerecord/test/cases/tasks/mysql_rake_test.rb
index 98fe24baa0..047153e7cc 100644
--- a/activerecord/test/cases/tasks/mysql_rake_test.rb
+++ b/activerecord/test/cases/tasks/mysql_rake_test.rb
@@ -75,7 +75,7 @@ if current_adapter?(:Mysql2Adapter)
       end
     end
 
-    class MysqlDBCreateAsRootTest < ActiveRecord::TestCase
+    class MysqlDBCreateWithInvalidPermissionsTest < ActiveRecord::TestCase
       def setup
         @connection    = stub("Connection", create_database: true)
         @error         = Mysql2::Error.new("Invalid permissions")
@@ -86,13 +86,8 @@ if current_adapter?(:Mysql2Adapter)
           "password" => "wossname"
         }
 
-        $stdin.stubs(:gets).returns("secret\n")
-        $stdout.stubs(:print).returns(nil)
-        @error.stubs(:errno).returns(1045)
         ActiveRecord::Base.stubs(:connection).returns(@connection)
-        ActiveRecord::Base.stubs(:establish_connection).
-          raises(@error).
-          then.returns(true)
+        ActiveRecord::Base.stubs(:establish_connection).raises(@error)
 
         $stdout, @original_stdout = StringIO.new, $stdout
         $stderr, @original_stderr = StringIO.new, $stderr
@@ -102,75 +97,11 @@ if current_adapter?(:Mysql2Adapter)
         $stdout, $stderr = @original_stdout, @original_stderr
       end
 
-      def test_root_password_is_requested
-        assert_permissions_granted_for("pat")
-        $stdin.expects(:gets).returns("secret\n")
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_connection_established_as_root
-        assert_permissions_granted_for("pat")
-        ActiveRecord::Base.expects(:establish_connection).with(
-          "adapter"  => "mysql2",
-          "database" => nil,
-          "username" => "root",
-          "password" => "secret"
-        )
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_database_created_by_root
-        assert_permissions_granted_for("pat")
-        @connection.expects(:create_database).
-          with("my-app-db", {})
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_grant_privileges_for_normal_user
-        assert_permissions_granted_for("pat")
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_do_not_grant_privileges_for_root_user
-        @configuration["username"] = "root"
-        @configuration["password"] = ""
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_connection_established_as_normal_user
-        assert_permissions_granted_for("pat")
-        ActiveRecord::Base.expects(:establish_connection).returns do
-          ActiveRecord::Base.expects(:establish_connection).with(
-            "adapter"  => "mysql2",
-            "database" => "my-app-db",
-            "username" => "pat",
-            "password" => "secret"
-          )
-
-          raise @error
+      def test_raises_error
+        assert_raises(Mysql2::Error) do
+          ActiveRecord::Tasks::DatabaseTasks.create @configuration
         end
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
       end
-
-      def test_sends_output_to_stderr_when_other_errors
-        @error.stubs(:errno).returns(42)
-
-        $stderr.expects(:puts).at_least_once.returns(nil)
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      private
-
-        def assert_permissions_granted_for(db_user)
-          db_name = @configuration["database"]
-          db_password = @configuration["password"]
-          @connection.expects(:execute).with("GRANT ALL PRIVILEGES ON `#{db_name}`.* TO '#{db_user}'@'localhost' IDENTIFIED BY '#{db_password}' WITH GRANT OPTION;")
-        end
     end
 
     class MySQLDBDropTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/tasks/postgresql_rake_test.rb b/activerecord/test/cases/tasks/postgresql_rake_test.rb
index 6302e84884..ca1defa332 100644
--- a/activerecord/test/cases/tasks/postgresql_rake_test.rb
+++ b/activerecord/test/cases/tasks/postgresql_rake_test.rb
@@ -229,7 +229,6 @@ if current_adapter?(:PostgreSQLAdapter)
 
         ActiveRecord::Base.stubs(:connection).returns(@connection)
         ActiveRecord::Base.stubs(:establish_connection).returns(true)
-        Kernel.stubs(:system)
       end
 
       def teardown
@@ -333,7 +332,6 @@ if current_adapter?(:PostgreSQLAdapter)
 
         ActiveRecord::Base.stubs(:connection).returns(@connection)
         ActiveRecord::Base.stubs(:establish_connection).returns(true)
-        Kernel.stubs(:system)
       end
 
       def test_structure_load
diff --git a/activerecord/test/cases/test_case.rb b/activerecord/test/cases/test_case.rb
index e57ebf56c8..06a8693a7d 100644
--- a/activerecord/test/cases/test_case.rb
+++ b/activerecord/test/cases/test_case.rb
@@ -110,7 +110,7 @@ module ActiveRecord
     # FIXME: this needs to be refactored so specific database can add their own
     # ignored SQL, or better yet, use a different notification for the queries
     # instead examining the SQL content.
-    oracle_ignored     = [/^select .*nextval/i, /^SAVEPOINT/, /^ROLLBACK TO/, /^\s*select .* from all_triggers/im, /^\s*select .* from all_constraints/im, /^\s*select .* from all_tab_cols/im]
+    oracle_ignored     = [/^select .*nextval/i, /^SAVEPOINT/, /^ROLLBACK TO/, /^\s*select .* from all_triggers/im, /^\s*select .* from all_constraints/im, /^\s*select .* from all_tab_cols/im, /^\s*select .* from all_sequences/im]
     mysql_ignored      = [/^SHOW FULL TABLES/i, /^SHOW FULL FIELDS/, /^SHOW CREATE TABLE /i, /^SHOW VARIABLES /, /^\s*SELECT (?:column_name|table_name)\b.*\bFROM information_schema\.(?:key_column_usage|tables)\b/im]
     postgresql_ignored = [/^\s*select\b.*\bfrom\b.*pg_namespace\b/im, /^\s*select tablename\b.*from pg_tables\b/im, /^\s*select\b.*\battname\b.*\bfrom\b.*\bpg_attribute\b/im, /^SHOW search_path/i]
     sqlite3_ignored =    [/^\s*SELECT name\b.*\bFROM sqlite_master/im, /^\s*SELECT sql\b.*\bFROM sqlite_master/im]
diff --git a/activerecord/test/cases/transaction_isolation_test.rb b/activerecord/test/cases/transaction_isolation_test.rb
index b1ebccdcc3..eaafd13360 100644
--- a/activerecord/test/cases/transaction_isolation_test.rb
+++ b/activerecord/test/cases/transaction_isolation_test.rb
@@ -15,9 +15,7 @@ unless ActiveRecord::Base.connection.supports_transaction_isolation?
       end
     end
   end
-end
-
-if ActiveRecord::Base.connection.supports_transaction_isolation?
+else
   class TransactionIsolationTest < ActiveRecord::TestCase
     self.use_transactional_tests = false
 
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index 7fd125ab74..5c8ae4d3cb 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -954,27 +954,25 @@ class TransactionsWithTransactionalFixturesTest < ActiveRecord::TestCase
   end
 end if Topic.connection.supports_savepoints?
 
-if current_adapter?(:PostgreSQLAdapter)
+if ActiveRecord::Base.connection.supports_transaction_isolation?
   class ConcurrentTransactionTest < TransactionTest
     # This will cause transactions to overlap and fail unless they are performed on
     # separate database connections.
-    unless in_memory_db?
-      def test_transaction_per_thread
-        threads = 3.times.map do
-          Thread.new do
-            Topic.transaction do
-              topic = Topic.find(1)
-              topic.approved = !topic.approved?
-              assert topic.save!
-              topic.approved = !topic.approved?
-              assert topic.save!
-            end
-            Topic.connection.close
+    def test_transaction_per_thread
+      threads = 3.times.map do
+        Thread.new do
+          Topic.transaction do
+            topic = Topic.find(1)
+            topic.approved = !topic.approved?
+            assert topic.save!
+            topic.approved = !topic.approved?
+            assert topic.save!
           end
+          Topic.connection.close
         end
-
-        threads.each(&:join)
       end
+
+      threads.each(&:join)
     end
 
     # Test for dirty reads among simultaneous transactions.
diff --git a/activerecord/test/cases/unsafe_raw_sql_test.rb b/activerecord/test/cases/unsafe_raw_sql_test.rb
new file mode 100644
index 0000000000..72d4997d0b
--- /dev/null
+++ b/activerecord/test/cases/unsafe_raw_sql_test.rb
@@ -0,0 +1,299 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/post"
+require "models/comment"
+
+class UnsafeRawSqlTest < ActiveRecord::TestCase
+  fixtures :posts, :comments
+
+  test "order: allows string column name" do
+    ids_expected = Post.order(Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("title").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("title").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows symbol column name" do
+    ids_expected = Post.order(Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(:title).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(:title).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows downcase symbol direction" do
+    ids_expected = Post.order(Arel.sql("title") => Arel.sql("asc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(title: :asc).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(title: :asc).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows upcase symbol direction" do
+    ids_expected = Post.order(Arel.sql("title") => Arel.sql("ASC")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(title: :ASC).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(title: :ASC).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows string direction" do
+    ids_expected = Post.order(Arel.sql("title") => Arel.sql("asc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(title: "asc").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(title: "asc").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows multiple columns" do
+    ids_expected = Post.order(Arel.sql("author_id"), Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(:author_id, :title).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(:author_id, :title).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows mixed" do
+    ids_expected = Post.order(Arel.sql("author_id"), Arel.sql("title") => Arel.sql("asc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(:author_id, title: :asc).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(:author_id, title: :asc).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows table and column name" do
+    ids_expected = Post.order(Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("posts.title").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("posts.title").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows column name and direction in string" do
+    ids_expected = Post.order(Arel.sql("title desc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("title desc").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("title desc").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows table name, column name and direction in string" do
+    ids_expected = Post.order(Arel.sql("title desc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("posts.title desc").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("posts.title desc").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: disallows invalid column name" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order("len(title) asc").pluck(:id)
+      end
+    end
+  end
+
+  test "order: disallows invalid direction" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ArgumentError) do
+        Post.order(title: :foo).pluck(:id)
+      end
+    end
+  end
+
+  test "order: disallows invalid column with direction" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order("len(title)" => :asc).pluck(:id)
+      end
+    end
+  end
+
+  test "order: always allows Arel" do
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(Arel.sql("length(title)")).pluck(:title) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(Arel.sql("length(title)")).pluck(:title) }
+
+    assert_equal ids_depr, ids_disabled
+  end
+
+  test "order: allows Arel.sql with binds" do
+    ids_expected = Post.order(Arel.sql("REPLACE(title, 'misc', 'zzzz'), id")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order([Arel.sql("REPLACE(title, ?, ?), id"), "misc", "zzzz"]).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order([Arel.sql("REPLACE(title, ?, ?), id"), "misc", "zzzz"]).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: disallows invalid bind statement" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order(["REPLACE(title, ?, ?), id", "misc", "zzzz"]).pluck(:id)
+      end
+    end
+  end
+
+  test "order: disallows invalid Array arguments" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order(["author_id", "length(title)"]).pluck(:id)
+      end
+    end
+  end
+
+  test "order: allows valid Array arguments" do
+    ids_expected = Post.order(Arel.sql("author_id, length(title)")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(["author_id", Arel.sql("length(title)")]).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(["author_id", Arel.sql("length(title)")]).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: logs deprecation warning for unrecognized column" do
+    with_unsafe_raw_sql_deprecated do
+      assert_deprecated(/Dangerous query method/) do
+        Post.order("length(title)")
+      end
+    end
+  end
+
+  test "pluck: allows string column name" do
+    titles_expected = Post.pluck(Arel.sql("title"))
+
+    titles_depr     = with_unsafe_raw_sql_deprecated { Post.pluck("title") }
+    titles_disabled = with_unsafe_raw_sql_disabled   { Post.pluck("title") }
+
+    assert_equal titles_expected, titles_depr
+    assert_equal titles_expected, titles_disabled
+  end
+
+  test "pluck: allows symbol column name" do
+    titles_expected = Post.pluck(Arel.sql("title"))
+
+    titles_depr     = with_unsafe_raw_sql_deprecated { Post.pluck(:title) }
+    titles_disabled = with_unsafe_raw_sql_disabled   { Post.pluck(:title) }
+
+    assert_equal titles_expected, titles_depr
+    assert_equal titles_expected, titles_disabled
+  end
+
+  test "pluck: allows multiple column names" do
+    values_expected = Post.pluck(Arel.sql("title"), Arel.sql("id"))
+
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.pluck(:title, :id) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.pluck(:title, :id) }
+
+    assert_equal values_expected, values_depr
+    assert_equal values_expected, values_disabled
+  end
+
+  test "pluck: allows column names with includes" do
+    values_expected = Post.includes(:comments).pluck(Arel.sql("title"), Arel.sql("id"))
+
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.includes(:comments).pluck(:title, :id) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.includes(:comments).pluck(:title, :id) }
+
+    assert_equal values_expected, values_depr
+    assert_equal values_expected, values_disabled
+  end
+
+  test "pluck: allows auto-generated attributes" do
+    values_expected = Post.pluck(Arel.sql("tags_count"))
+
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.pluck(:tags_count) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.pluck(:tags_count) }
+
+    assert_equal values_expected, values_depr
+    assert_equal values_expected, values_disabled
+  end
+
+  test "pluck: allows table and column names" do
+    titles_expected = Post.pluck(Arel.sql("title"))
+
+    titles_depr     = with_unsafe_raw_sql_deprecated { Post.pluck("posts.title") }
+    titles_disabled = with_unsafe_raw_sql_disabled   { Post.pluck("posts.title") }
+
+    assert_equal titles_expected, titles_depr
+    assert_equal titles_expected, titles_disabled
+  end
+
+  test "pluck: disallows invalid column name" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.pluck("length(title)")
+      end
+    end
+  end
+
+  test "pluck: disallows invalid column name amongst valid names" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.pluck(:title, "length(title)")
+      end
+    end
+  end
+
+  test "pluck: disallows invalid column names with includes" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.includes(:comments).pluck(:title, "length(title)")
+      end
+    end
+  end
+
+  test "pluck: always allows Arel" do
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.includes(:comments).pluck(:title, Arel.sql("length(title)")) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.includes(:comments).pluck(:title, Arel.sql("length(title)")) }
+
+    assert_equal values_depr, values_disabled
+  end
+
+  test "pluck: logs deprecation warning" do
+    with_unsafe_raw_sql_deprecated do
+      assert_deprecated(/Dangerous query method/) do
+        Post.includes(:comments).pluck(:title, "length(title)")
+      end
+    end
+  end
+
+  def with_unsafe_raw_sql_disabled(&blk)
+    with_config(:disabled, &blk)
+  end
+
+  def with_unsafe_raw_sql_deprecated(&blk)
+    with_config(:deprecated, &blk)
+  end
+
+  def with_config(new_value, &blk)
+    old_value = ActiveRecord::Base.allow_unsafe_raw_sql
+    ActiveRecord::Base.allow_unsafe_raw_sql = new_value
+    blk.call
+  ensure
+    ActiveRecord::Base.allow_unsafe_raw_sql = old_value
+  end
+end
diff --git a/activerecord/test/fixtures/other_posts.yml b/activerecord/test/fixtures/other_posts.yml
index 39ff763547..3e11a33802 100644
--- a/activerecord/test/fixtures/other_posts.yml
+++ b/activerecord/test/fixtures/other_posts.yml
@@ -5,3 +5,4 @@ second_welcome:
   author_id: 1
   title: Welcome to the another weblog
   body: It's really nice today
+  comments_count: 1
diff --git a/activerecord/test/fixtures/posts.yml b/activerecord/test/fixtures/posts.yml
index 86d46f753a..8d7e1e0ae7 100644
--- a/activerecord/test/fixtures/posts.yml
+++ b/activerecord/test/fixtures/posts.yml
@@ -28,6 +28,7 @@ sti_comments:
   author_id: 1
   title: sti comments
   body: hello
+  comments_count: 5
   type: Post
 
 sti_post_and_comments:
@@ -35,6 +36,7 @@ sti_post_and_comments:
   author_id: 1
   title: sti me
   body: hello
+  comments_count: 2
   type: StiPost
 
 sti_habtm:
@@ -50,6 +52,8 @@ eager_other:
   title: eager loading with OR'd conditions
   body: hello
   type: Post
+  comments_count: 1
+  tags_count: 3
 
 misc_by_bob:
   id: 8
@@ -57,6 +61,7 @@ misc_by_bob:
   title: misc post by bob
   body: hello
   type: Post
+  tags_count: 1
 
 misc_by_mary:
   id: 9
@@ -64,6 +69,7 @@ misc_by_mary:
   title: misc post by mary
   body: hello
   type: Post
+  tags_count: 1
 
 other_by_bob:
   id: 10
@@ -71,6 +77,7 @@ other_by_bob:
   title: other post by bob
   body: hello
   type: Post
+  tags_count: 1
 
 other_by_mary:
   id: 11
@@ -78,3 +85,4 @@ other_by_mary:
   title: other post by mary
   body: hello
   type: Post
+  tags_count: 1
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 3371fcbfcc..cb8686f315 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -22,6 +22,7 @@ class Author < ActiveRecord::Base
   has_many :comments_containing_the_letter_e, through: :posts, source: :comments
   has_many :comments_with_order_and_conditions, -> { order("comments.body").where("comments.body like 'Thank%'") }, through: :posts, source: :comments
   has_many :comments_with_include, -> { includes(:post).where(posts: { type: "Post" }) }, through: :posts, source: :comments
+  has_many :comments_for_first_author, -> { for_first_author }, through: :posts, source: :comments
 
   has_many :first_posts
   has_many :comments_on_first_posts, -> { order("posts.id desc, comments.id asc") }, through: :first_posts, source: :comments
@@ -100,10 +101,12 @@ class Author < ActiveRecord::Base
   has_many :taggings,        through: :posts, source: :taggings
   has_many :taggings_2,      through: :posts, source: :tagging
   has_many :tags,            through: :posts
+  has_many :ordered_tags,    through: :posts
   has_many :post_categories, through: :posts, source: :categories
   has_many :tagging_tags,    through: :taggings, source: :tag
 
   has_many :similar_posts, -> { distinct }, through: :tags, source: :tagged_posts
+  has_many :ordered_posts, -> { distinct }, through: :ordered_tags, source: :tagged_posts
   has_many :distinct_tags, -> { select("DISTINCT tags.*").order("tags.name") }, through: :posts, source: :tags
 
   has_many :tags_with_primary_key, through: :posts
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index 740aa593ac..5ab433f2d9 100644
--- a/activerecord/test/models/comment.rb
+++ b/activerecord/test/models/comment.rb
@@ -60,6 +60,10 @@ end
 
 class SpecialComment < Comment
   default_scope { where(deleted_at: nil) }
+
+  def self.what_are_you
+    "a special comment..."
+  end
 end
 
 class SubSpecialComment < SpecialComment
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index 56aafca60b..8881c69368 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -87,6 +87,17 @@ class Developer < ActiveRecord::Base
   private :track_instance_count
 end
 
+class SubDeveloper < Developer
+end
+
+class SymbolIgnoredDeveloper < ActiveRecord::Base
+  self.table_name = "developers"
+  self.ignored_columns = [:first_name, :last_name]
+
+  attr_accessor :last_name
+  define_attribute_method "last_name"
+end
+
 class AuditLog < ActiveRecord::Base
   belongs_to :developer, validate: true
   belongs_to :unvalidated_developer, class_name: "Developer"
diff --git a/activerecord/test/models/drink_designer.rb b/activerecord/test/models/drink_designer.rb
index 1c407844c5..eb6701b84e 100644
--- a/activerecord/test/models/drink_designer.rb
+++ b/activerecord/test/models/drink_designer.rb
@@ -3,3 +3,6 @@
 class DrinkDesigner < ActiveRecord::Base
   has_one :chef, as: :employable
 end
+
+class MocktailDesigner < DrinkDesigner
+end
diff --git a/activerecord/test/models/face.rb b/activerecord/test/models/face.rb
index 796aaa4dc9..948435136d 100644
--- a/activerecord/test/models/face.rb
+++ b/activerecord/test/models/face.rb
@@ -8,4 +8,8 @@ class Face < ActiveRecord::Base
   # These is a "broken" inverse_of for the purposes of testing
   belongs_to :horrible_man, class_name: "Man", inverse_of: :horrible_face
   belongs_to :horrible_polymorphic_man, polymorphic: true, inverse_of: :horrible_polymorphic_face
+
+  validate do
+    man
+  end
 end
diff --git a/activerecord/test/models/mocktail_designer.rb b/activerecord/test/models/mocktail_designer.rb
deleted file mode 100644
index 123ff4fb3d..0000000000
--- a/activerecord/test/models/mocktail_designer.rb
+++ /dev/null
@@ -1,4 +0,0 @@
-# frozen_string_literal: true
-
-class MocktailDesigner < DrinkDesigner
-end
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 4c8e847354..780a2c17f5 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -21,7 +21,7 @@ class Post < ActiveRecord::Base
 
   scope :containing_the_letter_a, -> { where("body LIKE '%a%'") }
   scope :titled_with_an_apostrophe, -> { where("title LIKE '%''%'") }
-  scope :ranked_by_comments,      -> { order("comments_count DESC") }
+  scope :ranked_by_comments, -> { order(arel_attribute(:comments_count).desc) }
 
   scope :limit_by, lambda { |l| limit(l) }
   scope :locked, -> { lock }
@@ -115,6 +115,7 @@ class Post < ActiveRecord::Base
   has_many :misc_tags, -> { where tags: { name: "Misc" } }, through: :taggings, source: :tag
   has_many :funky_tags, through: :taggings, source: :tag
   has_many :super_tags, through: :taggings
+  has_many :ordered_tags, through: :taggings
   has_many :tags_with_primary_key, through: :taggings, source: :tag_with_primary_key
   has_one :tagging, as: :taggable
 
@@ -318,5 +319,9 @@ class FakeKlass
     def arel_attribute(name, table)
       table[name]
     end
+
+    def enforce_raw_sql_whitelist(*args)
+      # noop
+    end
   end
 end
diff --git a/activerecord/test/models/tag.rb b/activerecord/test/models/tag.rb
index 4495ac4a09..bc13c3a42d 100644
--- a/activerecord/test/models/tag.rb
+++ b/activerecord/test/models/tag.rb
@@ -12,4 +12,5 @@ class OrderedTag < Tag
   self.table_name = "tags"
 
   has_many :taggings, -> { order("taggings.id DESC") }, foreign_key: "tag_id"
+  has_many :tagged_posts, through: :taggings, source: "taggable", source_type: "Post"
 end
diff --git a/activerecord/test/models/tagging.rb b/activerecord/test/models/tagging.rb
index fc0af026c5..861fde633f 100644
--- a/activerecord/test/models/tagging.rb
+++ b/activerecord/test/models/tagging.rb
@@ -8,6 +8,7 @@ class Tagging < ActiveRecord::Base
   belongs_to :tag, -> { includes(:tagging) }
   belongs_to :super_tag,   class_name: "Tag", foreign_key: "super_tag_id"
   belongs_to :invalid_tag, class_name: "Tag", foreign_key: "tag_id"
+  belongs_to :ordered_tag, class_name: "OrderedTag", foreign_key: "tag_id"
   belongs_to :blue_tag, -> { where tags: { name: "Blue" } }, class_name: "Tag", foreign_key: :tag_id
   belongs_to :tag_with_primary_key, class_name: "Tag", foreign_key: :tag_id, primary_key: :custom_primary_key
   belongs_to :taggable, polymorphic: true, counter_cache: :tags_count
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 8f872c38ba..bf66846840 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -191,6 +191,7 @@ ActiveRecord::Schema.define do
     t.string :resource_id
     t.string :resource_type
     t.integer :developer_id
+    t.datetime :updated_at
     t.datetime :deleted_at
     t.integer :comments
   end
@@ -204,6 +205,8 @@ ActiveRecord::Schema.define do
     t.bigint :rating, default: 1
     t.integer :account_id
     t.string :description, default: ""
+    t.index [:name, :rating], order: :desc
+    t.index [:name, :description], length: 10
     t.index [:firm_id, :type, :rating], name: "company_index", length: { type: 10 }, order: { rating: :desc }
     t.index [:firm_id, :type], name: "company_partial_index", where: "(rating > 10)"
     t.index :name, name: "company_name_index", using: :btree
diff --git a/activestorage/CHANGELOG.md b/activestorage/CHANGELOG.md
index 358552313f..c5171e7490 100644
--- a/activestorage/CHANGELOG.md
+++ b/activestorage/CHANGELOG.md
@@ -1,3 +1,12 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   Fix the gem adding the migrations files to the package.
+
+    *Yuji Yaginuma*
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
 *   Added to Rails.
 
     *DHH*
diff --git a/activestorage/README.md b/activestorage/README.md
index 17d98978bb..8af0409ec5 100644
--- a/activestorage/README.md
+++ b/activestorage/README.md
@@ -12,6 +12,10 @@ A key difference to how Active Storage works compared to other attachment soluti
 
 `Blob` models store attachment metadata (filename, content-type, etc.), and their identifier key in the storage service. Blob models do not store the actual binary data. They are intended to be immutable in spirit. One file, one blob. You can associate the same blob with multiple application models as well. And if you want to do transformations of a given `Blob`, the idea is that you'll simply create a new one, rather than attempt to mutate the existing one (though of course you can delete the previous version later if you don't need it).
 
+## Installation
+
+Run `rails active_storage:install` to copy over active_storage migrations.
+
 ## Examples
 
 One attachment:
@@ -24,7 +28,7 @@ class User < ApplicationRecord
 end
 
 # Attach an avatar to the user.
-user.avatar.attach(io: File.open("~/face.jpg"), filename: "avatar.jpg", content_type: "image/jpg")
+user.avatar.attach(io: File.open("/path/to/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
 
 # Does the user have an avatar?
 user.avatar.attached? # => true
@@ -63,7 +67,7 @@ end
 ```
 
 ```erb
-<%= form_with model: @message do |form| %>
+<%= form_with model: @message, local: true do |form| %>
   <%= form.text_field :title, placeholder: "Title" %><br>
   <%= form.text_area :content %><br><br>
 
@@ -139,3 +143,17 @@ Active Storage, with its included JavaScript library, supports uploading directl
 ## License
 
 Active Storage is released under the [MIT License](https://opensource.org/licenses/MIT).
+
+ ## Support
+
+API documentation is at:
+
+* http://api.rubyonrails.org
+
+Bug reports for the Ruby on Rails project can be filed here:
+
+* https://github.com/rails/rails/issues
+
+Feature requests should be discussed on the rails-core mailing list here:
+
+* https://groups.google.com/forum/?fromgroups#!forum/rubyonrails-core
diff --git a/activestorage/Rakefile b/activestorage/Rakefile
index aa71a65f6e..2aa4d2a76f 100644
--- a/activestorage/Rakefile
+++ b/activestorage/Rakefile
@@ -11,4 +11,6 @@ Rake::TestTask.new do |test|
   test.warning = false
 end
 
+task :package
+
 task default: :test
diff --git a/activestorage/activestorage.gemspec b/activestorage/activestorage.gemspec
index 911e1a0469..7f7f1a26ac 100644
--- a/activestorage/activestorage.gemspec
+++ b/activestorage/activestorage.gemspec
@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.email    = "david@loudthinking.com"
   s.homepage = "http://rubyonrails.org"
 
-  s.files        = Dir["CHANGELOG.md", "MIT-LICENSE", "README.md", "lib/**/*", "app/**/*", "config/**/*"]
+  s.files        = Dir["CHANGELOG.md", "MIT-LICENSE", "README.md", "lib/**/*", "app/**/*", "config/**/*", "db/**/*"]
   s.require_path = "lib"
 
   s.metadata = {
diff --git a/activestorage/app/controllers/active_storage/blobs_controller.rb b/activestorage/app/controllers/active_storage/blobs_controller.rb
index 00aa8567c8..a17e3852f9 100644
--- a/activestorage/app/controllers/active_storage/blobs_controller.rb
+++ b/activestorage/app/controllers/active_storage/blobs_controller.rb
@@ -6,20 +6,11 @@
 # authenticated redirection controller.
 class ActiveStorage::BlobsController < ActionController::Base
   def show
-    if blob = find_signed_blob
-      expires_in 5.minutes # service_url defaults to 5 minutes
-      redirect_to blob.service_url(disposition: disposition_param)
+    if blob = ActiveStorage::Blob.find_signed(params[:signed_id])
+      expires_in ActiveStorage::Blob.service.url_expires_in
+      redirect_to blob.service_url(disposition: params[:disposition])
     else
       head :not_found
     end
   end
-
-  private
-    def find_signed_blob
-      ActiveStorage::Blob.find_signed(params[:signed_id])
-    end
-
-    def disposition_param
-      params[:disposition].presence_in(%w( inline attachment )) || "inline"
-    end
 end
diff --git a/activestorage/app/controllers/active_storage/disk_controller.rb b/activestorage/app/controllers/active_storage/disk_controller.rb
index 41e6d61bff..a7e10c0696 100644
--- a/activestorage/app/controllers/active_storage/disk_controller.rb
+++ b/activestorage/app/controllers/active_storage/disk_controller.rb
@@ -5,10 +5,12 @@
 # Always go through the BlobsController, or your own authenticated controller, rather than directly
 # to the service url.
 class ActiveStorage::DiskController < ActionController::Base
+  skip_forgery_protection if default_protect_from_forgery
+
   def show
     if key = decode_verified_key
       send_data disk_service.download(key),
-        disposition: disposition_param, content_type: params[:content_type]
+        disposition: params[:disposition], content_type: params[:content_type]
     else
       head :not_found
     end
@@ -38,10 +40,6 @@ class ActiveStorage::DiskController < ActionController::Base
       ActiveStorage.verifier.verified(params[:encoded_key], purpose: :blob_key)
     end
 
-    def disposition_param
-      params[:disposition].presence || "inline"
-    end
-
 
     def decode_verified_token
       ActiveStorage.verifier.verified(params[:encoded_token], purpose: :blob_token)
diff --git a/activestorage/app/controllers/active_storage/previews_controller.rb b/activestorage/app/controllers/active_storage/previews_controller.rb
new file mode 100644
index 0000000000..9e8cf27b6e
--- /dev/null
+++ b/activestorage/app/controllers/active_storage/previews_controller.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class ActiveStorage::PreviewsController < ActionController::Base
+  def show
+    if blob = ActiveStorage::Blob.find_signed(params[:signed_blob_id])
+      expires_in ActiveStorage::Blob.service.url_expires_in
+      redirect_to ActiveStorage::Preview.new(blob, params[:variation_key]).processed.service_url(disposition: params[:disposition])
+    else
+      head :not_found
+    end
+  end
+end
diff --git a/activestorage/app/controllers/active_storage/variants_controller.rb b/activestorage/app/controllers/active_storage/variants_controller.rb
index 02e3010626..dc5e78ecc0 100644
--- a/activestorage/app/controllers/active_storage/variants_controller.rb
+++ b/activestorage/app/controllers/active_storage/variants_controller.rb
@@ -6,24 +6,11 @@
 # authenticated redirection controller.
 class ActiveStorage::VariantsController < ActionController::Base
   def show
-    if blob = find_signed_blob
-      expires_in 5.minutes # service_url defaults to 5 minutes
-      redirect_to ActiveStorage::Variant.new(blob, decoded_variation).processed.service_url(disposition: disposition_param)
+    if blob = ActiveStorage::Blob.find_signed(params[:signed_blob_id])
+      expires_in ActiveStorage::Blob.service.url_expires_in
+      redirect_to ActiveStorage::Variant.new(blob, params[:variation_key]).processed.service_url(disposition: params[:disposition])
     else
       head :not_found
     end
   end
-
-  private
-    def find_signed_blob
-      ActiveStorage::Blob.find_signed(params[:signed_blob_id])
-    end
-
-    def decoded_variation
-      ActiveStorage::Variation.decode(params[:variation_key])
-    end
-
-    def disposition_param
-      params[:disposition].presence_in(%w( inline attachment )) || "inline"
-    end
 end
diff --git a/activestorage/app/jobs/active_storage/analyze_job.rb b/activestorage/app/jobs/active_storage/analyze_job.rb
new file mode 100644
index 0000000000..2a952f9f74
--- /dev/null
+++ b/activestorage/app/jobs/active_storage/analyze_job.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+# Provides asynchronous analysis of ActiveStorage::Blob records via ActiveStorage::Blob#analyze_later.
+class ActiveStorage::AnalyzeJob < ActiveStorage::BaseJob
+  def perform(blob)
+    blob.analyze
+  end
+end
diff --git a/activestorage/app/jobs/active_storage/base_job.rb b/activestorage/app/jobs/active_storage/base_job.rb
new file mode 100644
index 0000000000..6caab42a2d
--- /dev/null
+++ b/activestorage/app/jobs/active_storage/base_job.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ActiveStorage::BaseJob < ActiveJob::Base
+  queue_as { ActiveStorage.queue }
+end
diff --git a/activestorage/app/jobs/active_storage/purge_job.rb b/activestorage/app/jobs/active_storage/purge_job.rb
index 990ab27c9f..98874d2250 100644
--- a/activestorage/app/jobs/active_storage/purge_job.rb
+++ b/activestorage/app/jobs/active_storage/purge_job.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-# Provides delayed purging of ActiveStorage::Blob records via ActiveStorage::Blob#purge_later.
-class ActiveStorage::PurgeJob < ActiveJob::Base
+# Provides asynchronous purging of ActiveStorage::Blob records via ActiveStorage::Blob#purge_later.
+class ActiveStorage::PurgeJob < ActiveStorage::BaseJob
   # FIXME: Limit this to a custom ActiveStorage error
   retry_on StandardError
 
diff --git a/activestorage/app/models/active_storage/attachment.rb b/activestorage/app/models/active_storage/attachment.rb
index 29226e8ee9..9f61a5dbf3 100644
--- a/activestorage/app/models/active_storage/attachment.rb
+++ b/activestorage/app/models/active_storage/attachment.rb
@@ -14,6 +14,8 @@ class ActiveStorage::Attachment < ActiveRecord::Base
 
   delegate_missing_to :blob
 
+  after_create_commit :analyze_blob_later
+
   # Synchronously purges the blob (deletes it from the configured service) and destroys the attachment.
   def purge
     blob.purge
@@ -25,4 +27,9 @@ class ActiveStorage::Attachment < ActiveRecord::Base
     blob.purge_later
     destroy
   end
+
+  private
+    def analyze_blob_later
+      blob.analyze_later unless blob.analyzed?
+    end
 end
diff --git a/activestorage/app/models/active_storage/blob.rb b/activestorage/app/models/active_storage/blob.rb
index e6cf08ce83..acaf22fac1 100644
--- a/activestorage/app/models/active_storage/blob.rb
+++ b/activestorage/app/models/active_storage/blob.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_storage/analyzer/null_analyzer"
+
 # A blob is a record that contains the metadata about a file and a key for where that file resides on the service.
 # Blobs can be created in two ways:
 #
@@ -14,13 +16,20 @@
 # update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file.
 # If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one.
 class ActiveStorage::Blob < ActiveRecord::Base
+  class UnpreviewableError < StandardError; end
+  class UnrepresentableError < StandardError; end
+
   self.table_name = "active_storage_blobs"
 
   has_secure_token :key
-  store :metadata, coder: JSON
+  store :metadata, accessors: [ :analyzed ], coder: JSON
 
   class_attribute :service
 
+  has_many :attachments
+
+  has_one_attached :preview_image
+
   class << self
     # You can used the signed ID of a blob to refer to it on the client side without fear of tampering.
     # This is particularly helpful for direct uploads where the client-side needs to refer to the blob
@@ -101,24 +110,76 @@ class ActiveStorage::Blob < ActiveRecord::Base
     content_type.start_with?("text")
   end
 
-  # Returns an ActiveStorage::Variant instance with the set of +transformations+
-  # passed in. This is only relevant for image files, and it allows any image to
-  # be transformed for size, colors, and the like. Example:
+  # Returns an ActiveStorage::Variant instance with the set of +transformations+ provided. This is only relevant for image
+  # files, and it allows any image to be transformed for size, colors, and the like. Example:
   #
   #   avatar.variant(resize: "100x100").processed.service_url
   #
-  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100.
+  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100px.
   # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
   #
   # Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a
   # specific variant that can be created by a controller on-demand. Like so:
   #
-  #   <%= image_tag url_for(Current.user.avatar.variant(resize: "100x100")) %>
+  #   <%= image_tag Current.user.avatar.variant(resize: "100x100") %>
   #
   # This will create a URL for that specific blob with that specific variant, which the ActiveStorage::VariantsController
   # can then produce on-demand.
   def variant(transformations)
-    ActiveStorage::Variant.new(self, ActiveStorage::Variation.new(transformations))
+    ActiveStorage::Variant.new(self, ActiveStorage::Variation.wrap(transformations))
+  end
+
+
+  # Returns an ActiveStorage::Preview instance with the set of +transformations+ provided. A preview is an image generated
+  # from a non-image blob. Active Storage comes with built-in previewers for videos and PDF documents. The video previewer
+  # extracts the first frame from a video and the PDF previewer extracts the first page from a PDF document.
+  #
+  #   blob.preview(resize: "100x100").processed.service_url
+  #
+  # Avoid processing previews synchronously in views. Instead, link to a controller action that processes them on demand.
+  # Active Storage provides one, but you may want to create your own (for example, if you need authentication). Here’s
+  # how to use the built-in version:
+  #
+  #   <%= image_tag video.preview(resize: "100x100") %>
+  #
+  # This method raises ActiveStorage::Blob::UnpreviewableError if no previewer accepts the receiving blob. To determine
+  # whether a blob is accepted by any previewer, call ActiveStorage::Blob#previewable?.
+  def preview(transformations)
+    if previewable?
+      ActiveStorage::Preview.new(self, ActiveStorage::Variation.wrap(transformations))
+    else
+      raise UnpreviewableError
+    end
+  end
+
+  # Returns true if any registered previewer accepts the blob. By default, this will return true for videos and PDF documents.
+  def previewable?
+    ActiveStorage.previewers.any? { |klass| klass.accept?(self) }
+  end
+
+
+  # Returns an ActiveStorage::Preview instance for a previewable blob or an ActiveStorage::Variant instance for an image blob.
+  #
+  #   blob.representation(resize: "100x100").processed.service_url
+  #
+  # Raises ActiveStorage::Blob::UnrepresentableError if the receiving blob is neither an image nor previewable. Call
+  # ActiveStorage::Blob#representable? to determine whether a blob is representable.
+  #
+  # See ActiveStorage::Blob#preview and ActiveStorage::Blob#variant for more information.
+  def representation(transformations)
+    case
+    when previewable?
+      preview transformations
+    when image?
+      variant transformations
+    else
+      raise UnrepresentableError
+    end
+  end
+
+  # Returns true if the blob is an image or is previewable.
+  def representable?
+    image? || previewable?
   end
 
 
@@ -126,13 +187,13 @@ class ActiveStorage::Blob < ActiveRecord::Base
   # with users. Instead, the +service_url+ should only be exposed as a redirect from a stable, possibly authenticated URL.
   # Hiding the +service_url+ behind a redirect also gives you the power to change services without updating all URLs. And
   # it allows permanent URLs that redirect to the +service_url+ to be cached in the view.
-  def service_url(expires_in: 5.minutes, disposition: :inline)
-    service.url key, expires_in: expires_in, disposition: "#{disposition}; #{filename.parameters}", filename: filename, content_type: content_type
+  def service_url(expires_in: service.url_expires_in, disposition: "inline")
+    service.url key, expires_in: expires_in, disposition: disposition, filename: filename, content_type: content_type
   end
 
   # Returns a URL that can be used to directly upload a file for this blob on the service. This URL is intended to be
   # short-lived for security and only generated on-demand by the client-side JavaScript responsible for doing the uploading.
-  def service_url_for_direct_upload(expires_in: 5.minutes)
+  def service_url_for_direct_upload(expires_in: service.url_expires_in)
     service.url_for_direct_upload key, expires_in: expires_in, content_type: content_type, content_length: byte_size, checksum: checksum
   end
 
@@ -165,11 +226,52 @@ class ActiveStorage::Blob < ActiveRecord::Base
   end
 
 
+  # Extracts and stores metadata from the file associated with this blob using a relevant analyzer. Active Storage comes
+  # with built-in analyzers for images and videos. See ActiveStorage::Analyzer::ImageAnalyzer and
+  # ActiveStorage::Analyzer::VideoAnalyzer for information about the specific attributes they extract and the third-party
+  # libraries they require.
+  #
+  # To choose the analyzer for a blob, Active Storage calls +accept?+ on each registered analyzer in order. It uses the
+  # first analyzer for which +accept?+ returns true when given the blob. If no registered analyzer accepts the blob, no
+  # metadata is extracted from it.
+  #
+  # In a Rails application, add or remove analyzers by manipulating +Rails.application.config.active_storage.analyzers+
+  # in an initializer:
+  #
+  #   # Add a custom analyzer for Microsoft Office documents:
+  #   Rails.application.config.active_storage.analyzers.append DOCXAnalyzer
+  #
+  #   # Remove the built-in video analyzer:
+  #   Rails.application.config.active_storage.analyzers.delete ActiveStorage::Analyzer::VideoAnalyzer
+  #
+  # Outside of a Rails application, manipulate +ActiveStorage.analyzers+ instead.
+  #
+  # You won't ordinarily need to call this method from a Rails application. New blobs are automatically and asynchronously
+  # analyzed via #analyze_later when they're attached for the first time.
+  def analyze
+    update! metadata: metadata.merge(extract_metadata_via_analyzer)
+  end
+
+  # Enqueues an ActiveStorage::AnalyzeJob which calls #analyze.
+  #
+  # This method is automatically called for a blob when it's attached for the first time. You can call it to analyze a blob
+  # again (e.g. if you add a new analyzer or modify an existing one).
+  def analyze_later
+    ActiveStorage::AnalyzeJob.perform_later(self)
+  end
+
+  # Returns true if the blob has been analyzed.
+  def analyzed?
+    analyzed
+  end
+
+
   # Deletes the file on the service that's associated with this blob. This should only be done if the blob is going to be
   # deleted as well or you will essentially have a dead reference. It's recommended to use the +#purge+ and +#purge_later+
   # methods in most circumstances.
   def delete
-    service.delete key
+    service.delete(key)
+    service.delete_prefixed("variants/#{key}/") if image?
   end
 
   # Deletes the file on the service and then destroys the blob record. This is the recommended way to dispose of unwanted
@@ -196,4 +298,17 @@ class ActiveStorage::Blob < ActiveRecord::Base
         io.rewind
       end.base64digest
     end
+
+
+    def extract_metadata_via_analyzer
+      analyzer.metadata.merge(analyzed: true)
+    end
+
+    def analyzer
+      analyzer_class.new(self)
+    end
+
+    def analyzer_class
+      ActiveStorage.analyzers.detect { |klass| klass.accept?(self) } || ActiveStorage::Analyzer::NullAnalyzer
+    end
 end
diff --git a/activestorage/app/models/active_storage/filename.rb b/activestorage/app/models/active_storage/filename.rb
index dead6b6d33..79d55dc889 100644
--- a/activestorage/app/models/active_storage/filename.rb
+++ b/activestorage/app/models/active_storage/filename.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-# Encapsulates a string representing a filename to provide convenience access to parts of it and a sanitized version.
-# This is what's returned by ActiveStorage::Blob#filename. A Filename instance is comparable so it can be used for sorting.
+# Encapsulates a string representing a filename to provide convenient access to parts of it and sanitization.
+# A Filename instance is returned by ActiveStorage::Blob#filename, and is comparable so it can be used for sorting.
 class ActiveStorage::Filename
   include Comparable
 
@@ -9,23 +9,31 @@ class ActiveStorage::Filename
     @filename = filename
   end
 
-  # Returns the basename of the filename.
+  # Returns the part of the filename preceding any extension.
   #
   #   ActiveStorage::Filename.new("racecar.jpg").base # => "racecar"
+  #   ActiveStorage::Filename.new("racecar").base     # => "racecar"
+  #   ActiveStorage::Filename.new(".gitignore").base  # => ".gitignore"
   def base
     File.basename @filename, extension_with_delimiter
   end
 
-  # Returns the extension with delimiter of the filename.
+  # Returns the extension of the filename (i.e. the substring following the last dot, excluding a dot at the
+  # beginning) with the dot that precedes it. If the filename has no extension, an empty string is returned.
   #
   #   ActiveStorage::Filename.new("racecar.jpg").extension_with_delimiter # => ".jpg"
+  #   ActiveStorage::Filename.new("racecar").extension_with_delimiter     # => ""
+  #   ActiveStorage::Filename.new(".gitignore").extension_with_delimiter  # => ""
   def extension_with_delimiter
     File.extname @filename
   end
 
-  # Returns the extension without delimiter of the filename.
+  # Returns the extension of the filename (i.e. the substring following the last dot, excluding a dot at
+  # the beginning). If the filename has no extension, an empty string is returned.
   #
   #   ActiveStorage::Filename.new("racecar.jpg").extension_without_delimiter # => "jpg"
+  #   ActiveStorage::Filename.new("racecar").extension_without_delimiter     # => ""
+  #   ActiveStorage::Filename.new(".gitignore").extension_without_delimiter  # => ""
   def extension_without_delimiter
     extension_with_delimiter.from(1).to_s
   end
@@ -37,7 +45,7 @@ class ActiveStorage::Filename
   #   ActiveStorage::Filename.new("foo:bar.jpg").sanitized # => "foo-bar.jpg"
   #   ActiveStorage::Filename.new("foo/bar.jpg").sanitized # => "foo-bar.jpg"
   #
-  # ...and any other character unsafe for URLs or storage is converted or stripped.
+  # Characters considered unsafe for storage (e.g. \, $, and the RTL override character) are replaced with a dash.
   def sanitized
     @filename.encode(Encoding::UTF_8, invalid: :replace, undef: :replace, replace: "�").strip.tr("\u{202E}%$|:;/\t\r\n\\", "-")
   end
diff --git a/activestorage/app/models/active_storage/preview.rb b/activestorage/app/models/active_storage/preview.rb
new file mode 100644
index 0000000000..be5053edae
--- /dev/null
+++ b/activestorage/app/models/active_storage/preview.rb
@@ -0,0 +1,90 @@
+# frozen_string_literal: true
+
+# Some non-image blobs can be previewed: that is, they can be presented as images. A video blob can be previewed by
+# extracting its first frame, and a PDF blob can be previewed by extracting its first page.
+#
+# A previewer extracts a preview image from a blob. Active Storage provides previewers for videos and PDFs:
+# ActiveStorage::Previewer::VideoPreviewer and ActiveStorage::Previewer::PDFPreviewer. Build custom previewers by
+# subclassing ActiveStorage::Previewer and implementing the requisite methods. Consult the ActiveStorage::Previewer
+# documentation for more details on what's required of previewers.
+#
+# To choose the previewer for a blob, Active Storage calls +accept?+ on each registered previewer in order. It uses the
+# first previewer for which +accept?+ returns true when given the blob. In a Rails application, add or remove previewers
+# by manipulating +Rails.application.config.active_storage.previewers+ in an initializer:
+#
+#   Rails.application.config.active_storage.previewers
+#   # => [ ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer ]
+#
+#   # Add a custom previewer for Microsoft Office documents:
+#   Rails.application.config.active_storage.previewers << DOCXPreviewer
+#   # => [ ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer, DOCXPreviewer ]
+#
+# Outside of a Rails application, modify +ActiveStorage.previewers+ instead.
+#
+# The built-in previewers rely on third-party system libraries:
+#
+# * {ffmpeg}[https://www.ffmpeg.org]
+# * {mupdf}[https://mupdf.com]
+#
+# These libraries are not provided by Rails. You must install them yourself to use the built-in previewers. Before you
+# install and use third-party software, make sure you understand the licensing implications of doing so.
+class ActiveStorage::Preview
+  class UnprocessedError < StandardError; end
+
+  attr_reader :blob, :variation
+
+  def initialize(blob, variation_or_variation_key)
+    @blob, @variation = blob, ActiveStorage::Variation.wrap(variation_or_variation_key)
+  end
+
+  # Processes the preview if it has not been processed yet. Returns the receiving Preview instance for convenience:
+  #
+  #   blob.preview(resize: "100x100").processed.service_url
+  #
+  # Processing a preview generates an image from its blob and attaches the preview image to the blob. Because the preview
+  # image is stored with the blob, it is only generated once.
+  def processed
+    process unless processed?
+    self
+  end
+
+  # Returns the blob's attached preview image.
+  def image
+    blob.preview_image
+  end
+
+  # Returns the URL of the preview's variant on the service. Raises ActiveStorage::Preview::UnprocessedError if the
+  # preview has not been processed yet.
+  #
+  # This method synchronously processes a variant of the preview image, so do not call it in views. Instead, generate
+  # a stable URL that redirects to the short-lived URL returned by this method.
+  def service_url(**options)
+    if processed?
+      variant.service_url(options)
+    else
+      raise UnprocessedError
+    end
+  end
+
+  private
+    def processed?
+      image.attached?
+    end
+
+    def process
+      previewer.preview { |attachable| image.attach(attachable) }
+    end
+
+    def variant
+      ActiveStorage::Variant.new(image, variation).processed
+    end
+
+
+    def previewer
+      previewer_class.new(blob)
+    end
+
+    def previewer_class
+      ActiveStorage.previewers.detect { |klass| klass.accept?(blob) }
+    end
+end
diff --git a/activestorage/app/models/active_storage/variant.rb b/activestorage/app/models/active_storage/variant.rb
index 02bf32b352..fa5aa69bd3 100644
--- a/activestorage/app/models/active_storage/variant.rb
+++ b/activestorage/app/models/active_storage/variant.rb
@@ -38,8 +38,8 @@ class ActiveStorage::Variant
   attr_reader :blob, :variation
   delegate :service, to: :blob
 
-  def initialize(blob, variation)
-    @blob, @variation = blob, variation
+  def initialize(blob, variation_or_variation_key)
+    @blob, @variation = blob, ActiveStorage::Variation.wrap(variation_or_variation_key)
   end
 
   # Returns the variant instance itself after it's been processed or an existing processing has been found on the service.
@@ -50,7 +50,7 @@ class ActiveStorage::Variant
 
   # Returns a combination key of the blob and the variation that together identifies a specific variant.
   def key
-    "variants/#{blob.key}/#{variation.key}"
+    "variants/#{blob.key}/#{Digest::SHA256.hexdigest(variation.key)}"
   end
 
   # Returns the URL of the variant on the service. This URL is intended to be short-lived for security and not used directly
@@ -61,10 +61,14 @@ class ActiveStorage::Variant
   # Use <tt>url_for(variant)</tt> (or the implied form, like +link_to variant+ or +redirect_to variant+) to get the stable URL
   # for a variant that points to the ActiveStorage::VariantsController, which in turn will use this +service_call+ method
   # for its redirection.
-  def service_url(expires_in: 5.minutes, disposition: :inline)
+  def service_url(expires_in: service.url_expires_in, disposition: :inline)
     service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename, content_type: blob.content_type
   end
 
+  # Returns the receiving variant. Allows ActiveStorage::Variant and ActiveStorage::Preview instances to be used interchangeably.
+  def image
+    self
+  end
 
   private
     def processed?
diff --git a/activestorage/app/models/active_storage/variation.rb b/activestorage/app/models/active_storage/variation.rb
index bf269e2a8f..13bad87cac 100644
--- a/activestorage/app/models/active_storage/variation.rb
+++ b/activestorage/app/models/active_storage/variation.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/object/inclusion"
-
 # A set of transformations that can be applied to a blob to create a variant. This class is exposed via
 # the ActiveStorage::Blob#variant method and should rarely be used directly.
 #
@@ -15,7 +13,21 @@ class ActiveStorage::Variation
   attr_reader :transformations
 
   class << self
-    # Returns a variation instance with the transformations that were encoded by +encode+.
+    # Returns a Variation instance based on the given variator. If the variator is a Variation, it is
+    # returned unmodified. If it is a String, it is passed to ActiveStorage::Variation.decode. Otherwise,
+    # it is assumed to be a transformations Hash and is passed directly to the constructor.
+    def wrap(variator)
+      case variator
+      when self
+        variator
+      when String
+        decode variator
+      else
+        new variator
+      end
+    end
+
+    # Returns a Variation instance with the transformations that were encoded by +encode+.
     def decode(key)
       new ActiveStorage.verifier.verify(key, purpose: :variation)
     end
diff --git a/activestorage/config/routes.rb b/activestorage/config/routes.rb
index 168788475c..1eae21445a 100644
--- a/activestorage/config/routes.rb
+++ b/activestorage/config/routes.rb
@@ -1,30 +1,43 @@
 # frozen_string_literal: true
 
 Rails.application.routes.draw do
-  get "/rails/active_storage/blobs/:signed_id/*filename" => "active_storage/blobs#show", as: :rails_service_blob
+  get "/rails/active_storage/blobs/:signed_id/*filename" => "active_storage/blobs#show", as: :rails_service_blob, internal: true
 
-  direct :rails_blob do |blob|
-    route_for(:rails_service_blob, blob.signed_id, blob.filename)
+  direct :rails_blob do |blob, options|
+    route_for(:rails_service_blob, blob.signed_id, blob.filename, options)
   end
 
-  resolve("ActiveStorage::Blob")       { |blob| route_for(:rails_blob, blob) }
-  resolve("ActiveStorage::Attachment") { |attachment| route_for(:rails_blob, attachment.blob) }
+  resolve("ActiveStorage::Blob")       { |blob, options| route_for(:rails_blob, blob) }
+  resolve("ActiveStorage::Attachment") { |attachment, options| route_for(:rails_blob, attachment.blob, options) }
 
 
-  get "/rails/active_storage/variants/:signed_blob_id/:variation_key/*filename" => "active_storage/variants#show", as: :rails_blob_variation
+  get "/rails/active_storage/variants/:signed_blob_id/:variation_key/*filename" => "active_storage/variants#show", as: :rails_blob_variation, internal: true
 
-  direct :rails_variant do |variant|
+  direct :rails_variant do |variant, options|
     signed_blob_id = variant.blob.signed_id
     variation_key  = variant.variation.key
     filename       = variant.blob.filename
 
-    route_for(:rails_blob_variation, signed_blob_id, variation_key, filename)
+    route_for(:rails_blob_variation, signed_blob_id, variation_key, filename, options)
   end
 
-  resolve("ActiveStorage::Variant") { |variant| route_for(:rails_variant, variant) }
+  resolve("ActiveStorage::Variant") { |variant, options| route_for(:rails_variant, variant, options) }
 
 
-  get  "/rails/active_storage/disk/:encoded_key/*filename" => "active_storage/disk#show", as: :rails_disk_service
-  put  "/rails/active_storage/disk/:encoded_token" => "active_storage/disk#update", as: :update_rails_disk_service
-  post "/rails/active_storage/direct_uploads" => "active_storage/direct_uploads#create", as: :rails_direct_uploads
+  get "/rails/active_storage/previews/:signed_blob_id/:variation_key/*filename" => "active_storage/previews#show", as: :rails_blob_preview, internal: true
+
+  direct :rails_preview do |preview, options|
+    signed_blob_id = preview.blob.signed_id
+    variation_key  = preview.variation.key
+    filename       = preview.blob.filename
+
+    route_for(:rails_blob_preview, signed_blob_id, variation_key, filename, options)
+  end
+
+  resolve("ActiveStorage::Preview") { |preview, options| route_for(:rails_preview, preview, options) }
+
+
+  get  "/rails/active_storage/disk/:encoded_key/*filename" => "active_storage/disk#show", as: :rails_disk_service, internal: true
+  put  "/rails/active_storage/disk/:encoded_token" => "active_storage/disk#update", as: :update_rails_disk_service, internal: true
+  post "/rails/active_storage/direct_uploads" => "active_storage/direct_uploads#create", as: :rails_direct_uploads, internal: true
 end
diff --git a/activestorage/lib/active_storage.rb b/activestorage/lib/active_storage.rb
index ccc1d4a163..d1ff6b7032 100644
--- a/activestorage/lib/active_storage.rb
+++ b/activestorage/lib/active_storage.rb
@@ -26,13 +26,19 @@
 require "active_record"
 require "active_support"
 require "active_support/rails"
-require_relative "active_storage/version"
+require "active_storage/version"
 
 module ActiveStorage
   extend ActiveSupport::Autoload
 
   autoload :Attached
   autoload :Service
+  autoload :Previewer
+  autoload :Analyzer
 
+  mattr_accessor :logger
   mattr_accessor :verifier
+  mattr_accessor :queue
+  mattr_accessor :previewers, default: []
+  mattr_accessor :analyzers, default: []
 end
diff --git a/activestorage/lib/active_storage/analyzer.rb b/activestorage/lib/active_storage/analyzer.rb
new file mode 100644
index 0000000000..837785a12b
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require "active_storage/downloading"
+
+module ActiveStorage
+  # This is an abstract base class for analyzers, which extract metadata from blobs. See
+  # ActiveStorage::Analyzer::ImageAnalyzer for an example of a concrete subclass.
+  class Analyzer
+    include Downloading
+
+    attr_reader :blob
+
+    # Implement this method in a concrete subclass. Have it return true when given a blob from which
+    # the analyzer can extract metadata.
+    def self.accept?(blob)
+      false
+    end
+
+    def initialize(blob)
+      @blob = blob
+    end
+
+    # Override this method in a concrete subclass. Have it return a Hash of metadata.
+    def metadata
+      raise NotImplementedError
+    end
+
+    private
+      def logger
+        ActiveStorage.logger
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/image_analyzer.rb b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
new file mode 100644
index 0000000000..25e0251e6e
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # Extracts width and height in pixels from an image blob.
+  #
+  # Example:
+  #
+  #   ActiveStorage::Analyzer::ImageAnalyzer.new(blob).metadata
+  #   # => { width: 4104, height: 2736 }
+  #
+  # This analyzer relies on the third-party {MiniMagick}[https://github.com/minimagick/minimagick] gem. MiniMagick requires
+  # the {ImageMagick}[http://www.imagemagick.org] system library. These libraries are not provided by Rails; you must
+  # install them yourself to use this analyzer.
+  class Analyzer::ImageAnalyzer < Analyzer
+    def self.accept?(blob)
+      blob.image?
+    end
+
+    def metadata
+      read_image do |image|
+        { width: image.width, height: image.height }
+      end
+    rescue LoadError
+      logger.info "Skipping image analysis because the mini_magick gem isn't installed"
+      {}
+    end
+
+    private
+      def read_image
+        download_blob_to_tempfile do |file|
+          require "mini_magick"
+          yield MiniMagick::Image.new(file.path)
+        end
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/null_analyzer.rb b/activestorage/lib/active_storage/analyzer/null_analyzer.rb
new file mode 100644
index 0000000000..8ff7ce48e5
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/null_analyzer.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Analyzer::NullAnalyzer < Analyzer # :nodoc:
+    def self.accept?(blob)
+      true
+    end
+
+    def metadata
+      {}
+    end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/video_analyzer.rb b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
new file mode 100644
index 0000000000..1c144baa37
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/hash/compact"
+
+module ActiveStorage
+  # Extracts the following from a video blob:
+  #
+  # * Width (pixels)
+  # * Height (pixels)
+  # * Duration (seconds)
+  # * Angle (degrees)
+  # * Aspect ratio
+  #
+  # Example:
+  #
+  #   ActiveStorage::VideoAnalyzer.new(blob).metadata
+  #   # => { width: 640, height: 480, duration: 5.0, angle: 0, aspect_ratio: [4, 3] }
+  #
+  # This analyzer requires the {ffmpeg}[https://www.ffmpeg.org] system library, which is not provided by Rails. You must
+  # install ffmpeg yourself to use this analyzer.
+  class Analyzer::VideoAnalyzer < Analyzer
+    class_attribute :ffprobe_path, default: "ffprobe"
+
+    def self.accept?(blob)
+      blob.video?
+    end
+
+    def metadata
+      { width: width, height: height, duration: duration, angle: angle, aspect_ratio: aspect_ratio }.compact
+    end
+
+    private
+      def width
+        rotated? ? raw_height : raw_width
+      end
+
+      def height
+        rotated? ? raw_width : raw_height
+      end
+
+      def raw_width
+        Integer(video_stream["width"]) if video_stream["width"]
+      end
+
+      def raw_height
+        Integer(video_stream["height"]) if video_stream["height"]
+      end
+
+      def duration
+        Float(video_stream["duration"]) if video_stream["duration"]
+      end
+
+      def angle
+        Integer(tags["rotate"]) if tags["rotate"]
+      end
+
+      def aspect_ratio
+        if descriptor = video_stream["display_aspect_ratio"]
+          descriptor.split(":", 2).collect(&:to_i)
+        end
+      end
+
+      def rotated?
+        angle == 90 || angle == 270
+      end
+
+
+      def tags
+        @tags ||= video_stream["tags"] || {}
+      end
+
+      def video_stream
+        @video_stream ||= streams.detect { |stream| stream["codec_type"] == "video" } || {}
+      end
+
+      def streams
+        probe["streams"] || []
+      end
+
+      def probe
+        download_blob_to_tempfile { |file| probe_from(file) }
+      end
+
+      def probe_from(file)
+        IO.popen([ ffprobe_path, "-print_format", "json", "-show_streams", "-v", "error", file.path ]) do |output|
+          JSON.parse(output.read)
+        end
+      rescue Errno::ENOENT
+        logger.info "Skipping video analysis because ffmpeg isn't installed"
+        {}
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/attached/macros.rb b/activestorage/lib/active_storage/attached/macros.rb
index 35a081adc4..2b38a9b887 100644
--- a/activestorage/lib/active_storage/attached/macros.rb
+++ b/activestorage/lib/active_storage/attached/macros.rb
@@ -12,6 +12,10 @@ module ActiveStorage
     # There is no column defined on the model side, Active Storage takes
     # care of the mapping between your records and the attachment.
     #
+    # To avoid N+1 queries, you can include the attached blobs in your query like so:
+    #
+    #   User.with_attached_avatar
+    #
     # Under the covers, this relationship is implemented as a +has_one+ association to a
     # ActiveStorage::Attachment record and a +has_one-through+ association to a
     # ActiveStorage::Blob record. These associations are available as +avatar_attachment+
@@ -28,11 +32,17 @@ module ActiveStorage
         def #{name}
           @active_storage_attached_#{name} ||= ActiveStorage::Attached::One.new("#{name}", self, dependent: #{dependent == :purge_later ? ":purge_later" : "false"})
         end
+
+        def #{name}=(attachable)
+          #{name}.attach(attachable)
+        end
       CODE
 
       has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record
       has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob
 
+      scope :"with_attached_#{name}", -> { includes("#{name}_attachment": :blob) }
+
       if dependent == :purge_later
         before_destroy { public_send(name).purge_later }
       end
@@ -67,6 +77,10 @@ module ActiveStorage
         def #{name}
           @active_storage_attached_#{name} ||= ActiveStorage::Attached::Many.new("#{name}", self, dependent: #{dependent == :purge_later ? ":purge_later" : "false"})
         end
+
+        def #{name}=(attachables)
+          #{name}.attach(attachables)
+        end
       CODE
 
       has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment"
diff --git a/activestorage/lib/active_storage/attached/many.rb b/activestorage/lib/active_storage/attached/many.rb
index 59b7d7d559..6eace65b79 100644
--- a/activestorage/lib/active_storage/attached/many.rb
+++ b/activestorage/lib/active_storage/attached/many.rb
@@ -13,15 +13,18 @@ module ActiveStorage
     end
 
     # Associates one or several attachments with the current record, saving them to the database.
-    # Examples:
     #
     #   document.images.attach(params[:images]) # Array of ActionDispatch::Http::UploadedFile objects
     #   document.images.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
-    #   document.images.attach(io: File.open("~/racecar.jpg"), filename: "racecar.jpg", content_type: "image/jpg")
+    #   document.images.attach(io: File.open("/path/to/racecar.jpg"), filename: "racecar.jpg", content_type: "image/jpg")
     #   document.images.attach([ first_blob, second_blob ])
     def attach(*attachables)
       attachables.flatten.collect do |attachable|
-        attachments.create!(name: name, blob: create_blob_from(attachable))
+        if record.new_record?
+          attachments.build(record: record, blob: create_blob_from(attachable))
+        else
+          attachments.create!(record: record, blob: create_blob_from(attachable))
+        end
       end
     end
 
@@ -36,6 +39,11 @@ module ActiveStorage
       attachments.any?
     end
 
+    # Deletes associated attachments without purging them, leaving their respective blobs in place.
+    def detach
+      attachments.destroy_all if attached?
+    end
+
     # Directly purges each associated attachment (i.e. destroys the blobs and
     # attachments and deletes the files on the service).
     def purge
diff --git a/activestorage/lib/active_storage/attached/one.rb b/activestorage/lib/active_storage/attached/one.rb
index ac90f32d95..0244232b2c 100644
--- a/activestorage/lib/active_storage/attached/one.rb
+++ b/activestorage/lib/active_storage/attached/one.rb
@@ -14,17 +14,16 @@ module ActiveStorage
     end
 
     # Associates a given attachment with the current record, saving it to the database.
-    # Examples:
     #
     #   person.avatar.attach(params[:avatar]) # ActionDispatch::Http::UploadedFile object
     #   person.avatar.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
-    #   person.avatar.attach(io: File.open("~/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
+    #   person.avatar.attach(io: File.open("/path/to/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
     #   person.avatar.attach(avatar_blob) # ActiveStorage::Blob object
     def attach(attachable)
       if attached? && dependent == :purge_later
         replace attachable
       else
-        write_attachment create_attachment_from(attachable)
+        write_attachment build_attachment_from(attachable)
       end
     end
 
@@ -39,6 +38,14 @@ module ActiveStorage
       attachment.present?
     end
 
+    # Deletes the attachment without purging it, leaving its blob in place.
+    def detach
+      if attached?
+        attachment.destroy
+        write_attachment nil
+      end
+    end
+
     # Directly purges the attachment (i.e. destroys the blob and
     # attachment and deletes the file on the service).
     def purge
@@ -59,14 +66,14 @@ module ActiveStorage
       def replace(attachable)
         blob.tap do
           transaction do
-            destroy
-            write_attachment create_attachment_from(attachable)
+            detach
+            write_attachment build_attachment_from(attachable)
           end
         end.purge_later
       end
 
-      def create_attachment_from(attachable)
-        ActiveStorage::Attachment.create!(record: record, name: name, blob: create_blob_from(attachable))
+      def build_attachment_from(attachable)
+        ActiveStorage::Attachment.new(record: record, name: name, blob: create_blob_from(attachable))
       end
 
       def write_attachment(attachment)
diff --git a/activestorage/lib/active_storage/downloading.rb b/activestorage/lib/active_storage/downloading.rb
new file mode 100644
index 0000000000..3dac6b116a
--- /dev/null
+++ b/activestorage/lib/active_storage/downloading.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  module Downloading
+    private
+      # Opens a new tempfile in #tempdir and copies blob data into it. Yields the tempfile.
+      def download_blob_to_tempfile # :doc:
+        Tempfile.open("ActiveStorage", tempdir) do |file|
+          download_blob_to file
+          yield file
+        end
+      end
+
+      # Efficiently downloads blob data into the given file.
+      def download_blob_to(file) # :doc:
+        file.binmode
+        blob.download { |chunk| file.write(chunk) }
+        file.rewind
+      end
+
+      # Returns the directory in which tempfiles should be opened. Defaults to +Dir.tmpdir+.
+      def tempdir # :doc:
+        Dir.tmpdir
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/engine.rb b/activestorage/lib/active_storage/engine.rb
index 590a36a30a..b870e6d4d6 100644
--- a/activestorage/lib/active_storage/engine.rb
+++ b/activestorage/lib/active_storage/engine.rb
@@ -3,19 +3,29 @@
 require "rails"
 require "active_storage"
 
+require "active_storage/previewer/pdf_previewer"
+require "active_storage/previewer/video_previewer"
+
+require "active_storage/analyzer/image_analyzer"
+require "active_storage/analyzer/video_analyzer"
+
 module ActiveStorage
   class Engine < Rails::Engine # :nodoc:
     isolate_namespace ActiveStorage
 
     config.active_storage = ActiveSupport::OrderedOptions.new
+    config.active_storage.previewers = [ ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer ]
+    config.active_storage.analyzers = [ ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer ]
+    config.active_storage.paths = ActiveSupport::OrderedOptions.new
 
     config.eager_load_namespaces << ActiveStorage
 
-    initializer "active_storage.logger" do
-      require "active_storage/service"
-
+    initializer "active_storage.configs" do
       config.after_initialize do |app|
-        ActiveStorage::Service.logger = app.config.active_storage.logger || Rails.logger
+        ActiveStorage.logger     = app.config.active_storage.logger || Rails.logger
+        ActiveStorage.queue      = app.config.active_storage.queue
+        ActiveStorage.previewers = app.config.active_storage.previewers || []
+        ActiveStorage.analyzers  = app.config.active_storage.analyzers || []
       end
     end
 
@@ -59,5 +69,21 @@ module ActiveStorage
         end
       end
     end
+
+    initializer "active_storage.paths" do
+      config.after_initialize do |app|
+        if ffprobe_path = app.config.active_storage.paths.ffprobe
+          ActiveStorage::Analyzer::VideoAnalyzer.ffprobe_path = ffprobe_path
+        end
+
+        if ffmpeg_path = app.config.active_storage.paths.ffmpeg
+          ActiveStorage::Previewer::VideoPreviewer.ffmpeg_path = ffmpeg_path
+        end
+
+        if mutool_path = app.config.active_storage.paths.mutool
+          ActiveStorage::Previewer::PDFPreviewer.mutool_path = mutool_path
+        end
+      end
+    end
   end
 end
diff --git a/activestorage/lib/active_storage/gem_version.rb b/activestorage/lib/active_storage/gem_version.rb
index e1d7b3493a..f048bb0b77 100644
--- a/activestorage/lib/active_storage/gem_version.rb
+++ b/activestorage/lib/active_storage/gem_version.rb
@@ -10,7 +10,7 @@ module ActiveStorage
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activestorage/lib/active_storage/log_subscriber.rb b/activestorage/lib/active_storage/log_subscriber.rb
index 0d00a75c0e..a4e148c1a5 100644
--- a/activestorage/lib/active_storage/log_subscriber.rb
+++ b/activestorage/lib/active_storage/log_subscriber.rb
@@ -18,6 +18,10 @@ module ActiveStorage
       info event, color("Deleted file from key: #{key_in(event)}", RED)
     end
 
+    def service_delete_prefixed(event)
+      info event, color("Deleted files by key prefix: #{event.payload[:prefix]}", RED)
+    end
+
     def service_exist(event)
       debug event, color("Checked if file exists at key: #{key_in(event)} (#{event.payload[:exist] ? "yes" : "no"})", BLUE)
     end
@@ -27,7 +31,7 @@ module ActiveStorage
     end
 
     def logger
-      ActiveStorage::Service.logger
+      ActiveStorage.logger
     end
 
     private
diff --git a/activestorage/lib/active_storage/previewer.rb b/activestorage/lib/active_storage/previewer.rb
new file mode 100644
index 0000000000..3d485988e9
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+require "active_storage/downloading"
+
+module ActiveStorage
+  # This is an abstract base class for previewers, which generate images from blobs. See
+  # ActiveStorage::Previewer::PDFPreviewer and ActiveStorage::Previewer::VideoPreviewer for examples of
+  # concrete subclasses.
+  class Previewer
+    include Downloading
+
+    attr_reader :blob
+
+    # Implement this method in a concrete subclass. Have it return true when given a blob from which
+    # the previewer can generate an image.
+    def self.accept?(blob)
+      false
+    end
+
+    def initialize(blob)
+      @blob = blob
+    end
+
+    # Override this method in a concrete subclass. Have it yield an attachable preview image (i.e.
+    # anything accepted by ActiveStorage::Attached::One#attach).
+    def preview
+      raise NotImplementedError
+    end
+
+    private
+      # Executes a system command, capturing its binary output in a tempfile. Yields the tempfile.
+      #
+      # Use this method to shell out to a system library (e.g. mupdf or ffmpeg) for preview image
+      # generation. The resulting tempfile can be used as the +:io+ value in an attachable Hash:
+      #
+      #   def preview
+      #     download_blob_to_tempfile do |input|
+      #       draw "my-drawing-command", input.path, "--format", "png", "-" do |output|
+      #         yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+      #       end
+      #     end
+      #   end
+      #
+      # The output tempfile is opened in the directory returned by ActiveStorage::Downloading#tempdir.
+      def draw(*argv) # :doc:
+        Tempfile.open("ActiveStorage", tempdir) do |file|
+          capture(*argv, to: file)
+          yield file
+        end
+      end
+
+      def capture(*argv, to:)
+        to.binmode
+        IO.popen(argv) { |out| IO.copy_stream(out, to) }
+        to.rewind
+      end
+
+      def logger
+        ActiveStorage.logger
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/previewer/pdf_previewer.rb b/activestorage/lib/active_storage/previewer/pdf_previewer.rb
new file mode 100644
index 0000000000..b84aefcc9c
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer/pdf_previewer.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Previewer::PDFPreviewer < Previewer
+    class_attribute :mutool_path, default: "mutool"
+
+    def self.accept?(blob)
+      blob.content_type == "application/pdf"
+    end
+
+    def preview
+      download_blob_to_tempfile do |input|
+        draw_first_page_from input do |output|
+          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+        end
+      end
+    end
+
+    private
+      def draw_first_page_from(file, &block)
+        draw mutool_path, "draw", "-F", "png", "-o", "-", file.path, "1", &block
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/previewer/video_previewer.rb b/activestorage/lib/active_storage/previewer/video_previewer.rb
new file mode 100644
index 0000000000..5d06e33f44
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer/video_previewer.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Previewer::VideoPreviewer < Previewer
+    class_attribute :ffmpeg_path, default: "ffmpeg"
+
+    def self.accept?(blob)
+      blob.video?
+    end
+
+    def preview
+      download_blob_to_tempfile do |input|
+        draw_relevant_frame_from input do |output|
+          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+        end
+      end
+    end
+
+    private
+      def draw_relevant_frame_from(file, &block)
+        draw ffmpeg_path, "-i", file.path, "-y", "-vcodec", "png",
+          "-vf", "thumbnail", "-vframes", "1", "-f", "image2", "-", &block
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/service.rb b/activestorage/lib/active_storage/service.rb
index b80fdea1ab..c8f675db86 100644
--- a/activestorage/lib/active_storage/service.rb
+++ b/activestorage/lib/active_storage/service.rb
@@ -4,6 +4,7 @@ require "active_storage/log_subscriber"
 
 module ActiveStorage
   class IntegrityError < StandardError; end
+
   # Abstract class serving as an interface for concrete services.
   #
   # The available services are:
@@ -40,7 +41,7 @@ module ActiveStorage
     extend ActiveSupport::Autoload
     autoload :Configurator
 
-    class_attribute :logger
+    class_attribute :url_expires_in, default: 5.minutes
 
     class << self
       # Configure an Active Storage service by name from a set of configurations,
@@ -77,6 +78,11 @@ module ActiveStorage
       raise NotImplementedError
     end
 
+    # Delete files at keys starting with the +prefix+.
+    def delete_prefixed(prefix)
+      raise NotImplementedError
+    end
+
     # Return +true+ if a file exists at the +key+.
     def exist?(key)
       raise NotImplementedError
@@ -103,15 +109,19 @@ module ActiveStorage
     end
 
     private
-      def instrument(operation, key, payload = {}, &block)
+      def instrument(operation, payload = {}, &block)
         ActiveSupport::Notifications.instrument(
           "service_#{operation}.active_storage",
-          payload.merge(key: key, service: service_name), &block)
+          payload.merge(service: service_name), &block)
       end
 
       def service_name
         # ActiveStorage::Service::DiskService => Disk
         self.class.name.split("::").third.remove("Service")
       end
+
+      def content_disposition_with(type: "inline", filename:)
+        (type.to_s.presence_in(%w( attachment inline )) || "inline") + "; #{filename.parameters}"
+      end
   end
 end
diff --git a/activestorage/lib/active_storage/service/azure_storage_service.rb b/activestorage/lib/active_storage/service/azure_storage_service.rb
index 895cc9c2f1..19b09991b3 100644
--- a/activestorage/lib/active_storage/service/azure_storage_service.rb
+++ b/activestorage/lib/active_storage/service/azure_storage_service.rb
@@ -19,7 +19,7 @@ module ActiveStorage
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         begin
           blobs.create_block_blob(container, key, io, content_md5: checksum)
         rescue Azure::Core::Http::HTTPError
@@ -28,13 +28,13 @@ module ActiveStorage
       end
     end
 
-    def download(key)
+    def download(key, &block)
       if block_given?
-        instrument :streaming_download, key do
+        instrument :streaming_download, key: key do
           stream(key, &block)
         end
       else
-        instrument :download, key do
+        instrument :download, key: key do
           _, io = blobs.get_blob(container, key)
           io.force_encoding(Encoding::BINARY)
         end
@@ -42,7 +42,7 @@ module ActiveStorage
     end
 
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         begin
           blobs.delete_blob(container, key)
         rescue Azure::Core::Http::HTTPError
@@ -51,8 +51,24 @@ module ActiveStorage
       end
     end
 
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        marker = nil
+
+        loop do
+          results = blobs.list_blobs(container, prefix: prefix, marker: marker)
+
+          results.each do |blob|
+            blobs.delete_blob(container, blob.name)
+          end
+
+          break unless marker = results.continuation_token.presence
+        end
+      end
+    end
+
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = blob_for(key).present?
         payload[:exist] = answer
         answer
@@ -60,13 +76,13 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, disposition:, content_type:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         base_url = url_for(key)
         generated_url = signer.signed_uri(
           URI(base_url), false,
           permissions: "r",
           expiry: format_expiry(expires_in),
-          content_disposition: disposition,
+          content_disposition: content_disposition_with(type: disposition, filename: filename),
           content_type: content_type
         ).to_s
 
@@ -77,7 +93,7 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         base_url = url_for(key)
         generated_url = signer.signed_uri(URI(base_url), false, permissions: "rw",
           expiry: format_expiry(expires_in)).to_s
@@ -108,15 +124,15 @@ module ActiveStorage
       end
 
       # Reads the object for the given key in chunks, yielding each to the block.
-      def stream(key, options = {}, &block)
+      def stream(key)
         blob = blob_for(key)
 
         chunk_size = 5.megabytes
         offset = 0
 
         while offset < blob.properties[:content_length]
-          _, io = blobs.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
-          yield io
+          _, chunk = blobs.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
+          yield chunk.force_encoding(Encoding::BINARY)
           offset += chunk_size
         end
       end
diff --git a/activestorage/lib/active_storage/service/disk_service.rb b/activestorage/lib/active_storage/service/disk_service.rb
index f600753a08..a8728c5bc3 100644
--- a/activestorage/lib/active_storage/service/disk_service.rb
+++ b/activestorage/lib/active_storage/service/disk_service.rb
@@ -16,7 +16,7 @@ module ActiveStorage
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         IO.copy_stream(io, make_path_for(key))
         ensure_integrity_of(key, checksum) if checksum
       end
@@ -24,7 +24,7 @@ module ActiveStorage
 
     def download(key)
       if block_given?
-        instrument :streaming_download, key do
+        instrument :streaming_download, key: key do
           File.open(path_for(key), "rb") do |file|
             while data = file.read(64.kilobytes)
               yield data
@@ -32,14 +32,14 @@ module ActiveStorage
           end
         end
       else
-        instrument :download, key do
+        instrument :download, key: key do
           File.binread path_for(key)
         end
       end
     end
 
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         begin
           File.delete path_for(key)
         rescue Errno::ENOENT
@@ -48,8 +48,16 @@ module ActiveStorage
       end
     end
 
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        Dir.glob(path_for("#{prefix}*")).each do |path|
+          FileUtils.rm_rf(path)
+        end
+      end
+    end
+
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = File.exist? path_for(key)
         payload[:exist] = answer
         answer
@@ -57,16 +65,17 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, disposition:, content_type:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         verified_key_with_expiration = ActiveStorage.verifier.generate(key, expires_in: expires_in, purpose: :blob_key)
 
         generated_url =
           if defined?(Rails.application)
             Rails.application.routes.url_helpers.rails_disk_service_path \
               verified_key_with_expiration,
-              filename: filename, disposition: disposition, content_type: content_type
+              filename: filename, disposition: content_disposition_with(type: disposition, filename: filename), content_type: content_type
           else
-            "/rails/active_storage/disk/#{verified_key_with_expiration}/#{filename}?content_type=#{content_type}&disposition=#{disposition}"
+            "/rails/active_storage/disk/#{verified_key_with_expiration}/#{filename}?content_type=#{content_type}" \
+              "&disposition=#{content_disposition_with(type: disposition, filename: filename)}"
           end
 
         payload[:url] = generated_url
@@ -76,7 +85,7 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         verified_token_with_expiration = ActiveStorage.verifier.generate(
           {
             key: key,
diff --git a/activestorage/lib/active_storage/service/gcs_service.rb b/activestorage/lib/active_storage/service/gcs_service.rb
index 685dd61a0a..6f6f4105fe 100644
--- a/activestorage/lib/active_storage/service/gcs_service.rb
+++ b/activestorage/lib/active_storage/service/gcs_service.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "google-cloud-storage", "~> 1.8"
+
 require "google/cloud/storage"
 require "active_support/core_ext/object/to_query"
 
@@ -7,34 +9,42 @@ module ActiveStorage
   # Wraps the Google Cloud Storage as an Active Storage service. See ActiveStorage::Service for the generic API
   # documentation that applies to all services.
   class Service::GCSService < Service
-    attr_reader :client, :bucket
-
-    def initialize(project:, keyfile:, bucket:, **options)
-      @client = Google::Cloud::Storage.new(project: project, keyfile: keyfile, **options)
-      @bucket = @client.bucket(bucket)
+    def initialize(**config)
+      @config = config
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         begin
-          bucket.create_file(io, key, md5: checksum)
+          # The official GCS client library doesn't allow us to create a file with no Content-Type metadata.
+          # We need the file we create to have no Content-Type so we can control it via the response-content-type
+          # param in signed URLs. Workaround: let the GCS client create the file with an inferred
+          # Content-Type (usually "application/octet-stream") then clear it.
+          bucket.create_file(io, key, md5: checksum).update do |file|
+            file.content_type = nil
+          end
         rescue Google::Cloud::InvalidArgumentError
           raise ActiveStorage::IntegrityError
         end
       end
     end
 
-    # FIXME: Add streaming when given a block
+    # FIXME: Download in chunks when given a block.
     def download(key)
-      instrument :download, key do
+      instrument :download, key: key do
         io = file_for(key).download
         io.rewind
-        io.read
+
+        if block_given?
+          yield io.read
+        else
+          io.read
+        end
       end
     end
 
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         begin
           file_for(key).delete
         rescue Google::Cloud::NotFoundError
@@ -43,8 +53,14 @@ module ActiveStorage
       end
     end
 
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        bucket.files(prefix: prefix).all(&:delete)
+      end
+    end
+
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = file_for(key).exists?
         payload[:exist] = answer
         answer
@@ -52,9 +68,9 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, content_type:, disposition:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         generated_url = file_for(key).signed_url expires: expires_in, query: {
-          "response-content-disposition" => disposition,
+          "response-content-disposition" => content_disposition_with(type: disposition, filename: filename),
           "response-content-type" => content_type
         }
 
@@ -65,7 +81,7 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         generated_url = bucket.signed_url key, method: "PUT", expires: expires_in,
           content_type: content_type, content_md5: checksum
 
@@ -80,8 +96,18 @@ module ActiveStorage
     end
 
     private
+      attr_reader :config
+
       def file_for(key)
         bucket.file(key, skip_lookup: true)
       end
+
+      def bucket
+        @bucket ||= client.bucket(config.fetch(:bucket))
+      end
+
+      def client
+        @client ||= Google::Cloud::Storage.new(config.except(:bucket))
+      end
   end
 end
diff --git a/activestorage/lib/active_storage/service/mirror_service.rb b/activestorage/lib/active_storage/service/mirror_service.rb
index 39e922f7ab..7eca8ce7f4 100644
--- a/activestorage/lib/active_storage/service/mirror_service.rb
+++ b/activestorage/lib/active_storage/service/mirror_service.rb
@@ -35,6 +35,11 @@ module ActiveStorage
       perform_across_services :delete, key
     end
 
+    # Delete files at keys starting with the +prefix+ on all services.
+    def delete_prefixed(prefix)
+      perform_across_services :delete_prefixed, prefix
+    end
+
     private
       def each_service(&block)
         [ primary, *mirrors ].each(&block)
diff --git a/activestorage/lib/active_storage/service/s3_service.rb b/activestorage/lib/active_storage/service/s3_service.rb
index e074269353..c95672f338 100644
--- a/activestorage/lib/active_storage/service/s3_service.rb
+++ b/activestorage/lib/active_storage/service/s3_service.rb
@@ -17,7 +17,7 @@ module ActiveStorage
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         begin
           object_for(key).put(upload_options.merge(body: io, content_md5: checksum))
         rescue Aws::S3::Errors::BadDigest
@@ -26,26 +26,32 @@ module ActiveStorage
       end
     end
 
-    def download(key)
+    def download(key, &block)
       if block_given?
-        instrument :streaming_download, key do
+        instrument :streaming_download, key: key do
           stream(key, &block)
         end
       else
-        instrument :download, key do
+        instrument :download, key: key do
           object_for(key).get.body.read.force_encoding(Encoding::BINARY)
         end
       end
     end
 
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         object_for(key).delete
       end
     end
 
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        bucket.objects(prefix: prefix).batch_delete!
+      end
+    end
+
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = object_for(key).exists?
         payload[:exist] = answer
         answer
@@ -53,9 +59,9 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, disposition:, content_type:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         generated_url = object_for(key).presigned_url :get, expires_in: expires_in.to_i,
-          response_content_disposition: disposition,
+          response_content_disposition: content_disposition_with(type: disposition, filename: filename),
           response_content_type: content_type
 
         payload[:url] = generated_url
@@ -65,7 +71,7 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         generated_url = object_for(key).presigned_url :put, expires_in: expires_in.to_i,
           content_type: content_type, content_length: content_length, content_md5: checksum
 
@@ -85,14 +91,14 @@ module ActiveStorage
       end
 
       # Reads the object for the given key in chunks, yielding each to the block.
-      def stream(key, options = {}, &block)
+      def stream(key)
         object = object_for(key)
 
         chunk_size = 5.megabytes
         offset = 0
 
         while offset < object.content_length
-          yield object.read(options.merge(range: "bytes=#{offset}-#{offset + chunk_size - 1}"))
+          yield object.get(range: "bytes=#{offset}-#{offset + chunk_size - 1}").body.read.force_encoding(Encoding::BINARY)
           offset += chunk_size
         end
       end
diff --git a/activestorage/package.json b/activestorage/package.json
index b481295a8d..621706000b 100644
--- a/activestorage/package.json
+++ b/activestorage/package.json
@@ -1,6 +1,6 @@
 {
   "name": "activestorage",
-  "version": "5.2.0.alpha",
+  "version": "5.2.0-beta2",
   "description": "Attach cloud and local files in Rails applications",
   "main": "app/assets/javascripts/activestorage.js",
   "files": [
diff --git a/activestorage/test/analyzer/image_analyzer_test.rb b/activestorage/test/analyzer/image_analyzer_test.rb
new file mode 100644
index 0000000000..9087072215
--- /dev/null
+++ b/activestorage/test/analyzer/image_analyzer_test.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/analyzer/image_analyzer"
+
+class ActiveStorage::Analyzer::ImageAnalyzerTest < ActiveSupport::TestCase
+  test "analyzing an image" do
+    blob = create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg")
+    metadata = blob.tap(&:analyze).metadata
+
+    assert_equal 4104, metadata[:width]
+    assert_equal 2736, metadata[:height]
+  end
+end
diff --git a/activestorage/test/analyzer/video_analyzer_test.rb b/activestorage/test/analyzer/video_analyzer_test.rb
new file mode 100644
index 0000000000..b3b9c97fe4
--- /dev/null
+++ b/activestorage/test/analyzer/video_analyzer_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/analyzer/video_analyzer"
+
+class ActiveStorage::Analyzer::VideoAnalyzerTest < ActiveSupport::TestCase
+  test "analyzing a video" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    metadata = blob.tap(&:analyze).metadata
+
+    assert_equal 640, metadata[:width]
+    assert_equal 480, metadata[:height]
+    assert_equal [4, 3], metadata[:aspect_ratio]
+    assert_equal 5.166648, metadata[:duration]
+    assert_not_includes metadata, :angle
+  end
+
+  test "analyzing a rotated video" do
+    blob = create_file_blob(filename: "rotated_video.mp4", content_type: "video/mp4")
+    metadata = blob.tap(&:analyze).metadata
+
+    assert_equal 480, metadata[:width]
+    assert_equal 640, metadata[:height]
+    assert_equal [4, 3], metadata[:aspect_ratio]
+    assert_equal 5.227975, metadata[:duration]
+    assert_equal 90, metadata[:angle]
+  end
+
+  test "analyzing a video without a video stream" do
+    blob = create_file_blob(filename: "video_without_video_stream.mp4", content_type: "video/mp4")
+    assert_equal({ "analyzed" => true }, blob.tap(&:analyze).metadata)
+  end
+end
diff --git a/activestorage/test/controllers/blobs_controller_test.rb b/activestorage/test/controllers/blobs_controller_test.rb
index c37b9c8a10..97177e64c2 100644
--- a/activestorage/test/controllers/blobs_controller_test.rb
+++ b/activestorage/test/controllers/blobs_controller_test.rb
@@ -5,7 +5,7 @@ require "database/setup"
 
 class ActiveStorage::BlobsControllerTest < ActionDispatch::IntegrationTest
   setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+    @blob = create_file_blob filename: "racecar.jpg"
   end
 
   test "showing blob utilizes browser caching" do
diff --git a/activestorage/test/controllers/previews_controller_test.rb b/activestorage/test/controllers/previews_controller_test.rb
new file mode 100644
index 0000000000..c3151a710e
--- /dev/null
+++ b/activestorage/test/controllers/previews_controller_test.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::PreviewsControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    @blob = create_file_blob filename: "report.pdf", content_type: "application/pdf"
+  end
+
+  test "showing preview inline" do
+    get rails_blob_preview_url(
+      filename: @blob.filename,
+      signed_blob_id: @blob.signed_id,
+      variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
+
+    assert @blob.preview_image.attached?
+    assert_redirected_to(/report\.png\?.*disposition=inline/)
+
+    image = read_image(@blob.preview_image.variant(resize: "100x100"))
+    assert_equal 77, image.width
+    assert_equal 100, image.height
+  end
+end
diff --git a/activestorage/test/controllers/variants_controller_test.rb b/activestorage/test/controllers/variants_controller_test.rb
index 0a049f3bc4..6c70d73786 100644
--- a/activestorage/test/controllers/variants_controller_test.rb
+++ b/activestorage/test/controllers/variants_controller_test.rb
@@ -5,7 +5,7 @@ require "database/setup"
 
 class ActiveStorage::VariantsControllerTest < ActionDispatch::IntegrationTest
   setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+    @blob = create_file_blob filename: "racecar.jpg"
   end
 
   test "showing variant inline" do
@@ -16,7 +16,7 @@ class ActiveStorage::VariantsControllerTest < ActionDispatch::IntegrationTest
 
     assert_redirected_to(/racecar\.jpg\?.*disposition=inline/)
 
-    image = read_image_variant(@blob.variant(resize: "100x100"))
+    image = read_image(@blob.variant(resize: "100x100"))
     assert_equal 100, image.width
     assert_equal 67, image.height
   end
diff --git a/activestorage/test/database/setup.rb b/activestorage/test/database/setup.rb
index 87564499e6..705650a25d 100644
--- a/activestorage/test/database/setup.rb
+++ b/activestorage/test/database/setup.rb
@@ -3,5 +3,5 @@
 require_relative "create_users_migration"
 
 ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
-ActiveRecord::Migrator.migrate File.expand_path("../../../db/migrate", __FILE__)
+ActiveRecord::Migrator.migrate File.expand_path("../../db/migrate", __dir__)
 ActiveStorageCreateUsers.migrate(:up)
diff --git a/activestorage/test/dummy/bin/bundle b/activestorage/test/dummy/bin/bundle
index 277e128251..5015ba6f8b 100755
--- a/activestorage/test/dummy/bin/bundle
+++ b/activestorage/test/dummy/bin/bundle
@@ -1,5 +1,5 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile", __FILE__)
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
 load Gem.bin_path("bundler", "bundle")
diff --git a/activestorage/test/dummy/config/application.rb b/activestorage/test/dummy/config/application.rb
index 7ee6625bb5..06cbc453a2 100644
--- a/activestorage/test/dummy/config/application.rb
+++ b/activestorage/test/dummy/config/application.rb
@@ -19,7 +19,7 @@ Bundler.require(*Rails.groups)
 
 module Dummy
   class Application < Rails::Application
-    config.load_defaults 5.1
+    config.load_defaults 5.2
 
     config.active_storage.service = :local
   end
diff --git a/activestorage/test/dummy/config/environments/test.rb b/activestorage/test/dummy/config/environments/test.rb
index ce0889e8ae..74a802d98c 100644
--- a/activestorage/test/dummy/config/environments/test.rb
+++ b/activestorage/test/dummy/config/environments/test.rb
@@ -30,6 +30,9 @@ Rails.application.configure do
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
+  # Disable request forgery protection in test environment.
+  config.action_controller.allow_forgery_protection = false
+
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
 end
diff --git a/activestorage/test/fixtures/files/report.pdf b/activestorage/test/fixtures/files/report.pdf
new file mode 100644
index 0000000000..cccb9b5d64
--- /dev/null
+++ b/activestorage/test/fixtures/files/report.pdf
diff --git a/activestorage/test/fixtures/files/rotated_video.mp4 b/activestorage/test/fixtures/files/rotated_video.mp4
new file mode 100644
index 0000000000..4c7a4e9e57
--- /dev/null
+++ b/activestorage/test/fixtures/files/rotated_video.mp4
diff --git a/activestorage/test/fixtures/files/video.mp4 b/activestorage/test/fixtures/files/video.mp4
new file mode 100644
index 0000000000..8fb1c5b24d
--- /dev/null
+++ b/activestorage/test/fixtures/files/video.mp4
diff --git a/activestorage/test/fixtures/files/video_without_video_stream.mp4 b/activestorage/test/fixtures/files/video_without_video_stream.mp4
new file mode 100644
index 0000000000..e6a55f868b
--- /dev/null
+++ b/activestorage/test/fixtures/files/video_without_video_stream.mp4
diff --git a/activestorage/test/models/attachments_test.rb b/activestorage/test/models/attachments_test.rb
index ac346c0087..20eec3c220 100644
--- a/activestorage/test/models/attachments_test.rb
+++ b/activestorage/test/models/attachments_test.rb
@@ -15,7 +15,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "funky.jpg", @user.avatar.filename.to_s
   end
 
-  test "attach existing sgid blob" do
+  test "attach existing blob from a signed ID" do
     @user.avatar.attach create_blob(filename: "funky.jpg").signed_id
     assert_equal "funky.jpg", @user.avatar.filename.to_s
   end
@@ -27,7 +27,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
 
   test "attach new blob from an UploadedFile" do
     file = file_fixture "racecar.jpg"
-    @user.avatar.attach Rack::Test::UploadedFile.new file
+    @user.avatar.attach Rack::Test::UploadedFile.new file.to_s
     assert_equal "racecar.jpg", @user.avatar.filename.to_s
   end
 
@@ -56,6 +56,40 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert ActiveStorage::Blob.service.exist?(@user.avatar.key)
   end
 
+  test "attach blob to new record" do
+    user = User.new(name: "Jason")
+
+    assert_no_changes -> { user.new_record? } do
+      assert_no_difference -> { ActiveStorage::Attachment.count } do
+        user.avatar.attach create_blob(filename: "funky.jpg")
+      end
+    end
+
+    assert user.avatar.attached?
+    assert_equal "funky.jpg", user.avatar.filename.to_s
+
+    assert_difference -> { ActiveStorage::Attachment.count }, +1 do
+      user.save!
+    end
+
+    assert user.reload.avatar.attached?
+    assert_equal "funky.jpg", user.avatar.filename.to_s
+  end
+
+  test "build new record with attached blob" do
+    assert_no_difference -> { ActiveStorage::Attachment.count } do
+      @user = User.new(name: "Jason", avatar: { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" })
+    end
+
+    assert @user.new_record?
+    assert @user.avatar.attached?
+    assert_equal "town.jpg", @user.avatar.filename.to_s
+
+    @user.save!
+    assert @user.reload.avatar.attached?
+    assert_equal "town.jpg", @user.avatar.filename.to_s
+  end
+
   test "access underlying associations of new blob" do
     @user.avatar.attach create_blob(filename: "funky.jpg")
     assert_equal @user, @user.avatar_attachment.record
@@ -63,6 +97,52 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "funky.jpg", @user.avatar_attachment.blob.filename.to_s
   end
 
+  test "analyze newly-attached blob" do
+    perform_enqueued_jobs do
+      @user.avatar.attach create_file_blob
+    end
+
+    assert_equal 4104, @user.avatar.reload.metadata[:width]
+    assert_equal 2736, @user.avatar.metadata[:height]
+  end
+
+  test "analyze attached blob only once" do
+    blob = create_file_blob
+
+    perform_enqueued_jobs do
+      @user.avatar.attach blob
+    end
+
+    assert blob.reload.analyzed?
+
+    @user.avatar.attachment.destroy
+
+    assert_no_enqueued_jobs do
+      @user.reload.avatar.attach blob
+    end
+  end
+
+  test "preserve existing metadata when analyzing a newly-attached blob" do
+    blob = create_file_blob(metadata: { foo: "bar" })
+
+    perform_enqueued_jobs do
+      @user.avatar.attach blob
+    end
+
+    assert_equal "bar", blob.reload.metadata[:foo]
+  end
+
+  test "detach blob" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+    avatar_blob_id = @user.avatar.blob.id
+    avatar_key = @user.avatar.key
+
+    @user.avatar.detach
+    assert_not @user.avatar.attached?
+    assert ActiveStorage::Blob.exists?(avatar_blob_id)
+    assert ActiveStorage::Blob.service.exist?(avatar_key)
+  end
+
   test "purge attached blob" do
     @user.avatar.attach create_blob(filename: "funky.jpg")
     avatar_key = @user.avatar.key
@@ -84,6 +164,19 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     end
   end
 
+  test "find with attached blob" do
+    records = %w[alice bob].map do |name|
+      User.create!(name: name).tap do |user|
+        user.avatar.attach create_blob(filename: "#{name}.jpg")
+      end
+    end
+
+    users = User.where(id: records.map(&:id)).with_attached_avatar.all
+
+    assert_equal "alice.jpg", users.first.avatar.filename.to_s
+    assert_equal "bob.jpg", users.second.avatar.filename.to_s
+  end
+
 
   test "attach existing blobs" do
     @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
@@ -101,6 +194,48 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "country.jpg", @user.highlights.second.filename.to_s
   end
 
+  test "attach blobs to new record" do
+    user = User.new(name: "Jason")
+
+    assert_no_changes -> { user.new_record? } do
+      assert_no_difference -> { ActiveStorage::Attachment.count } do
+        user.highlights.attach(
+          { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" },
+          { io: StringIO.new("IT"), filename: "country.jpg", content_type: "image/jpg" })
+      end
+    end
+
+    assert user.highlights.attached?
+    assert_equal "town.jpg", user.highlights.first.filename.to_s
+    assert_equal "country.jpg", user.highlights.second.filename.to_s
+
+    assert_difference -> { ActiveStorage::Attachment.count }, +2 do
+      user.save!
+    end
+
+    assert user.reload.highlights.attached?
+    assert_equal "town.jpg", user.highlights.first.filename.to_s
+    assert_equal "country.jpg", user.highlights.second.filename.to_s
+  end
+
+  test "build new record with attached blobs" do
+    assert_no_difference -> { ActiveStorage::Attachment.count } do
+      @user = User.new(name: "Jason", highlights: [
+        { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" },
+        { io: StringIO.new("IT"), filename: "country.jpg", content_type: "image/jpg" }])
+    end
+
+    assert @user.new_record?
+    assert @user.highlights.attached?
+    assert_equal "town.jpg", @user.highlights.first.filename.to_s
+    assert_equal "country.jpg", @user.highlights.second.filename.to_s
+
+    @user.save!
+    assert @user.reload.highlights.attached?
+    assert_equal "town.jpg", @user.highlights.first.filename.to_s
+    assert_equal "country.jpg", @user.highlights.second.filename.to_s
+  end
+
   test "find attached blobs" do
     @user.highlights.attach(
       { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" },
@@ -122,6 +257,68 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "town.jpg", @user.highlights_attachments.first.blob.filename.to_s
   end
 
+  test "analyze newly-attached blobs" do
+    perform_enqueued_jobs do
+      @user.highlights.attach(
+        create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg"),
+        create_file_blob(filename: "video.mp4", content_type: "video/mp4"))
+    end
+
+    assert_equal 4104, @user.highlights.first.metadata[:width]
+    assert_equal 2736, @user.highlights.first.metadata[:height]
+
+    assert_equal 640, @user.highlights.second.metadata[:width]
+    assert_equal 480, @user.highlights.second.metadata[:height]
+  end
+
+  test "analyze attached blobs only once" do
+    blobs = [
+      create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg"),
+      create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    ]
+
+    perform_enqueued_jobs do
+      @user.highlights.attach(blobs)
+    end
+
+    assert blobs.each(&:reload).all?(&:analyzed?)
+
+    @user.highlights.attachments.destroy_all
+
+    assert_no_enqueued_jobs do
+      @user.highlights.attach(blobs)
+    end
+  end
+
+  test "preserve existing metadata when analyzing newly-attached blobs" do
+    blobs = [
+      create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", metadata: { foo: "bar" }),
+      create_file_blob(filename: "video.mp4", content_type: "video/mp4", metadata: { foo: "bar" })
+    ]
+
+    perform_enqueued_jobs do
+      @user.highlights.attach(blobs)
+    end
+
+    blobs.each do |blob|
+      assert_equal "bar", blob.reload.metadata[:foo]
+    end
+  end
+
+  test "detach blobs" do
+    @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
+    highlight_blob_ids = @user.highlights.collect { |highlight| highlight.blob.id }
+    highlight_keys = @user.highlights.collect(&:key)
+
+    @user.highlights.detach
+    assert_not @user.highlights.attached?
+
+    assert ActiveStorage::Blob.exists?(highlight_blob_ids.first)
+    assert ActiveStorage::Blob.exists?(highlight_blob_ids.second)
+
+    assert ActiveStorage::Blob.service.exist?(highlight_keys.first)
+    assert ActiveStorage::Blob.service.exist?(highlight_keys.second)
+  end
 
   test "purge attached blobs" do
     @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
diff --git a/activestorage/test/models/blob_test.rb b/activestorage/test/models/blob_test.rb
index 6e815997ba..f94e65ed77 100644
--- a/activestorage/test/models/blob_test.rb
+++ b/activestorage/test/models/blob_test.rb
@@ -41,13 +41,21 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     end
   end
 
-  test "purge removes from external service" do
+  test "purge deletes file from external service" do
     blob = create_blob
 
     blob.purge
     assert_not ActiveStorage::Blob.service.exist?(blob.key)
   end
 
+  test "purge deletes variants from external service" do
+    blob = create_file_blob
+    variant = blob.variant(resize: "100>").processed
+
+    blob.purge
+    assert_not ActiveStorage::Blob.service.exist?(variant.key)
+  end
+
   private
     def expected_url_for(blob, disposition: :inline)
       query_string = { content_type: blob.content_type, disposition: "#{disposition}; #{blob.filename.parameters}" }.to_param
diff --git a/activestorage/test/models/preview_test.rb b/activestorage/test/models/preview_test.rb
new file mode 100644
index 0000000000..bcd8442f4b
--- /dev/null
+++ b/activestorage/test/models/preview_test.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::PreviewTest < ActiveSupport::TestCase
+  test "previewing a PDF" do
+    blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+    preview = blob.preview(resize: "640x280").processed
+
+    assert preview.image.attached?
+    assert_equal "report.png", preview.image.filename.to_s
+    assert_equal "image/png", preview.image.content_type
+
+    image = read_image(preview.image)
+    assert_equal 612, image.width
+    assert_equal 792, image.height
+  end
+
+  test "previewing an MP4 video" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    preview = blob.preview(resize: "640x280").processed
+
+    assert preview.image.attached?
+    assert_equal "video.png", preview.image.filename.to_s
+    assert_equal "image/png", preview.image.content_type
+
+    image = read_image(preview.image)
+    assert_equal 640, image.width
+    assert_equal 480, image.height
+  end
+
+  test "previewing an unpreviewable blob" do
+    blob = create_file_blob
+
+    assert_raises ActiveStorage::Blob::UnpreviewableError do
+      blob.preview resize: "640x280"
+    end
+  end
+end
diff --git a/activestorage/test/models/representation_test.rb b/activestorage/test/models/representation_test.rb
new file mode 100644
index 0000000000..29fe61aee4
--- /dev/null
+++ b/activestorage/test/models/representation_test.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::RepresentationTest < ActiveSupport::TestCase
+  test "representing an image" do
+    blob = create_file_blob
+    representation = blob.representation(resize: "100x100").processed
+
+    image = read_image(representation.image)
+    assert_equal 100, image.width
+    assert_equal 67, image.height
+  end
+
+  test "representing a PDF" do
+    blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+    representation = blob.representation(resize: "640x280").processed
+
+    image = read_image(representation.image)
+    assert_equal 612, image.width
+    assert_equal 792, image.height
+  end
+
+  test "representing an MP4 video" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    representation = blob.representation(resize: "640x280").processed
+
+    image = read_image(representation.image)
+    assert_equal 640, image.width
+    assert_equal 480, image.height
+  end
+
+  test "representing an unrepresentable blob" do
+    blob = create_blob
+
+    assert_raises ActiveStorage::Blob::UnrepresentableError do
+      blob.representation resize: "100x100"
+    end
+  end
+end
diff --git a/activestorage/test/models/variant_test.rb b/activestorage/test/models/variant_test.rb
index ca112ab907..b7d20ab55a 100644
--- a/activestorage/test/models/variant_test.rb
+++ b/activestorage/test/models/variant_test.rb
@@ -5,14 +5,14 @@ require "database/setup"
 
 class ActiveStorage::VariantTest < ActiveSupport::TestCase
   setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+    @blob = create_file_blob filename: "racecar.jpg"
   end
 
   test "resized variation" do
     variant = @blob.variant(resize: "100x100").processed
     assert_match(/racecar\.jpg/, variant.service_url)
 
-    image = read_image_variant(variant)
+    image = read_image(variant)
     assert_equal 100, image.width
     assert_equal 67, image.height
   end
@@ -21,9 +21,14 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
     variant = @blob.variant(resize: "100x100", monochrome: true).processed
     assert_match(/racecar\.jpg/, variant.service_url)
 
-    image = read_image_variant(variant)
+    image = read_image(variant)
     assert_equal 100, image.width
     assert_equal 67, image.height
     assert_match(/Gray/, image.colorspace)
   end
+
+  test "service_url doesn't grow in length despite long variant options" do
+    variant = @blob.variant(font: "a" * 10_000).processed
+    assert_operator variant.service_url.length, :<, 500
+  end
 end
diff --git a/activestorage/test/previewer/pdf_previewer_test.rb b/activestorage/test/previewer/pdf_previewer_test.rb
new file mode 100644
index 0000000000..fe32f39be4
--- /dev/null
+++ b/activestorage/test/previewer/pdf_previewer_test.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/previewer/pdf_previewer"
+
+class ActiveStorage::Previewer::PDFPreviewerTest < ActiveSupport::TestCase
+  setup do
+    @blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+  end
+
+  test "previewing a PDF document" do
+    ActiveStorage::Previewer::PDFPreviewer.new(@blob).preview do |attachable|
+      assert_equal "image/png", attachable[:content_type]
+      assert_equal "report.png", attachable[:filename]
+
+      image = MiniMagick::Image.read(attachable[:io])
+      assert_equal 612, image.width
+      assert_equal 792, image.height
+    end
+  end
+end
diff --git a/activestorage/test/previewer/video_previewer_test.rb b/activestorage/test/previewer/video_previewer_test.rb
new file mode 100644
index 0000000000..dba9b0d7e2
--- /dev/null
+++ b/activestorage/test/previewer/video_previewer_test.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/previewer/video_previewer"
+
+class ActiveStorage::Previewer::VideoPreviewerTest < ActiveSupport::TestCase
+  setup do
+    @blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+  end
+
+  test "previewing an MP4 video" do
+    ActiveStorage::Previewer::VideoPreviewer.new(@blob).preview do |attachable|
+      assert_equal "image/png", attachable[:content_type]
+      assert_equal "video.png", attachable[:filename]
+
+      image = MiniMagick::Image.read(attachable[:io])
+      assert_equal 640, image.width
+      assert_equal 480, image.height
+    end
+  end
+end
diff --git a/activestorage/test/service/azure_storage_service_test.rb b/activestorage/test/service/azure_storage_service_test.rb
index 4729bdfbc5..be31bbe858 100644
--- a/activestorage/test/service/azure_storage_service_test.rb
+++ b/activestorage/test/service/azure_storage_service_test.rb
@@ -11,9 +11,9 @@ if SERVICE_CONFIGURATIONS[:azure]
 
     test "signed URL generation" do
       url = @service.url(FIXTURE_KEY, expires_in: 5.minutes,
-        disposition: "inline; filename=\"avatar.png\"", filename: "avatar.png", content_type: "image/png")
+        disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png")
 
-      assert_match(/(\S+)&rscd=inline%3B\+filename%3D%22avatar.png%22&rsct=image%2Fpng/, url)
+      assert_match(/(\S+)&rscd=inline%3B\+filename%3D%22avatar\.png%22%3B\+filename\*%3DUTF-8%27%27avatar\.png&rsct=image%2Fpng/, url)
       assert_match SERVICE_CONFIGURATIONS[:azure][:container], url
     end
   end
diff --git a/activestorage/test/service/configurations.example.yml b/activestorage/test/service/configurations.example.yml
index 56ed37be5d..43cc013bc8 100644
--- a/activestorage/test/service/configurations.example.yml
+++ b/activestorage/test/service/configurations.example.yml
@@ -7,7 +7,7 @@
 #
 # gcs:
 #   service: GCS
-#   keyfile: {
+#   credentials: {
 #     type: "service_account",
 #     project_id: "",
 #     private_key_id: "",
diff --git a/activestorage/test/service/disk_service_test.rb b/activestorage/test/service/disk_service_test.rb
index e07d1d88bc..4a6361b920 100644
--- a/activestorage/test/service/disk_service_test.rb
+++ b/activestorage/test/service/disk_service_test.rb
@@ -9,6 +9,6 @@ class ActiveStorage::Service::DiskServiceTest < ActiveSupport::TestCase
 
   test "url generation" do
     assert_match(/rails\/active_storage\/disk\/.*\/avatar\.png\?content_type=image%2Fpng&disposition=inline/,
-      @service.url(FIXTURE_KEY, expires_in: 5.minutes, disposition: "inline; filename=\"avatar.png\"", filename: "avatar.png", content_type: "image/png"))
+      @service.url(FIXTURE_KEY, expires_in: 5.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png"))
   end
 end
diff --git a/activestorage/test/service/gcs_service_test.rb b/activestorage/test/service/gcs_service_test.rb
index f664cee90b..7efcd60fb7 100644
--- a/activestorage/test/service/gcs_service_test.rb
+++ b/activestorage/test/service/gcs_service_test.rb
@@ -32,12 +32,21 @@ if SERVICE_CONFIGURATIONS[:gcs]
     end
 
     test "signed URL generation" do
-      freeze_time do
-        url = SERVICE.bucket.signed_url(FIXTURE_KEY, expires: 120) +
-          "&response-content-disposition=inline%3B+filename%3D%22test.txt%22" +
-          "&response-content-type=text%2Fplain"
+      assert_match(/storage\.googleapis\.com\/.*response-content-disposition=inline.*test\.txt.*response-content-type=text%2Fplain/,
+        @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("test.txt"), content_type: "text/plain"))
+    end
+
+    test "signed URL response headers" do
+      begin
+        key  = SecureRandom.base58(24)
+        data = "Something else entirely!"
+        @service.upload(key, StringIO.new(data), checksum: Digest::MD5.base64digest(data))
 
-        assert_equal url, @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: "inline; filename=\"test.txt\"", filename: "test.txt", content_type: "text/plain")
+        url = @service.url(key, expires_in: 2.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("test.txt"), content_type: "text/plain")
+        response = Net::HTTP.get_response(URI(url))
+        assert_equal "text/plain", response.header["Content-Type"]
+      ensure
+        @service.delete key
       end
     end
   end
diff --git a/activestorage/test/service/mirror_service_test.rb b/activestorage/test/service/mirror_service_test.rb
index 93e86eff70..92101b1282 100644
--- a/activestorage/test/service/mirror_service_test.rb
+++ b/activestorage/test/service/mirror_service_test.rb
@@ -47,9 +47,11 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   end
 
   test "URL generation in primary service" do
+    filename = ActiveStorage::Filename.new("test.txt")
+
     freeze_time do
-      assert_equal SERVICE.primary.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: "test.txt", content_type: "text/plain"),
-        @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: "test.txt", content_type: "text/plain")
+      assert_equal SERVICE.primary.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain"),
+        @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain")
     end
   end
 
diff --git a/activestorage/test/service/s3_service_test.rb b/activestorage/test/service/s3_service_test.rb
index c07d6396b1..c3818422aa 100644
--- a/activestorage/test/service/s3_service_test.rb
+++ b/activestorage/test/service/s3_service_test.rb
@@ -33,7 +33,7 @@ if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].pr
 
     test "signed URL generation" do
       url = @service.url(FIXTURE_KEY, expires_in: 5.minutes,
-        disposition: "inline; filename=\"avatar.png\"", filename: "avatar.png", content_type: "image/png")
+        disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png")
 
       assert_match(/s3\.(\S+)?amazonaws.com.*response-content-disposition=inline.*avatar\.png.*response-content-type=image%2Fpng/, url)
       assert_match SERVICE_CONFIGURATIONS[:s3][:bucket], url
diff --git a/activestorage/test/service/shared_service_tests.rb b/activestorage/test/service/shared_service_tests.rb
index a9e1cb6ce9..ce28c4393a 100644
--- a/activestorage/test/service/shared_service_tests.rb
+++ b/activestorage/test/service/shared_service_tests.rb
@@ -50,6 +50,16 @@ module ActiveStorage::Service::SharedServiceTests
       assert_equal FIXTURE_DATA, @service.download(FIXTURE_KEY)
     end
 
+    test "downloading in chunks" do
+      chunks = []
+
+      @service.download(FIXTURE_KEY) do |chunk|
+        chunks << chunk
+      end
+
+      assert_equal [ FIXTURE_DATA ], chunks
+    end
+
     test "existing" do
       assert @service.exist?(FIXTURE_KEY)
       assert_not @service.exist?(FIXTURE_KEY + "nonsense")
@@ -65,5 +75,22 @@ module ActiveStorage::Service::SharedServiceTests
         @service.delete SecureRandom.base58(24)
       end
     end
+
+    test "deleting by prefix" do
+      begin
+        @service.upload("a/a/a", StringIO.new(FIXTURE_DATA))
+        @service.upload("a/a/b", StringIO.new(FIXTURE_DATA))
+        @service.upload("a/b/a", StringIO.new(FIXTURE_DATA))
+
+        @service.delete_prefixed("a/a/")
+        assert_not @service.exist?("a/a/a")
+        assert_not @service.exist?("a/a/b")
+        assert @service.exist?("a/b/a")
+      ensure
+        @service.delete("a/a/a")
+        @service.delete("a/a/b")
+        @service.delete("a/b/a")
+      end
+    end
   end
 end
diff --git a/activestorage/test/template/image_tag_test.rb b/activestorage/test/template/image_tag_test.rb
index dedc58452e..80f183e0e3 100644
--- a/activestorage/test/template/image_tag_test.rb
+++ b/activestorage/test/template/image_tag_test.rb
@@ -7,7 +7,7 @@ class ActiveStorage::ImageTagTest < ActionView::TestCase
   tests ActionView::Helpers::AssetTagHelper
 
   setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+    @blob = create_file_blob filename: "racecar.jpg"
   end
 
   test "blob" do
@@ -19,6 +19,12 @@ class ActiveStorage::ImageTagTest < ActionView::TestCase
     assert_dom_equal %(<img src="#{polymorphic_url variant}" />), image_tag(variant)
   end
 
+  test "preview" do
+    blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+    preview = blob.preview(resize: "100x100")
+    assert_dom_equal %(<img src="#{polymorphic_url preview}" />), image_tag(preview)
+  end
+
   test "attachment" do
     attachment = ActiveStorage::Attachment.new(blob: @blob)
     assert_dom_equal %(<img src="#{polymorphic_url attachment}" />), image_tag(attachment)
diff --git a/activestorage/test/test_helper.rb b/activestorage/test/test_helper.rb
index 2a969fa326..aaf1d452ea 100644
--- a/activestorage/test/test_helper.rb
+++ b/activestorage/test/test_helper.rb
@@ -1,11 +1,13 @@
 # frozen_string_literal: true
 
-require File.expand_path("../../test/dummy/config/environment.rb", __FILE__)
+ENV["RAILS_ENV"] ||= "test"
+require_relative "dummy/config/environment.rb"
 
 require "bundler/setup"
 require "active_support"
 require "active_support/test_case"
 require "active_support/testing/autorun"
+require "mini_magick"
 
 begin
   require "byebug"
@@ -22,7 +24,7 @@ Minitest.backtrace_filter = Minitest::BacktraceFilter.new
 
 require "yaml"
 SERVICE_CONFIGURATIONS = begin
-  erb = ERB.new(Pathname.new(File.expand_path("../service/configurations.yml", __FILE__)).read)
+  erb = ERB.new(Pathname.new(File.expand_path("service/configurations.yml", __dir__)).read)
   configuration = YAML.load(erb.result) || {}
   configuration.deep_symbolize_keys
 rescue Errno::ENOENT
@@ -32,30 +34,28 @@ end
 
 require "tmpdir"
 ActiveStorage::Blob.service = ActiveStorage::Service::DiskService.new(root: Dir.mktmpdir("active_storage_tests"))
-ActiveStorage::Service.logger = ActiveSupport::Logger.new(nil)
 
+ActiveStorage.logger = ActiveSupport::Logger.new(nil)
 ActiveStorage.verifier = ActiveSupport::MessageVerifier.new("Testing")
 
 class ActiveSupport::TestCase
-  self.file_fixture_path = File.expand_path("../fixtures/files", __FILE__)
+  self.file_fixture_path = File.expand_path("fixtures/files", __dir__)
 
   private
     def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain")
       ActiveStorage::Blob.create_after_upload! io: StringIO.new(data), filename: filename, content_type: content_type
     end
 
-    def create_image_blob(filename: "racecar.jpg", content_type: "image/jpeg")
-      ActiveStorage::Blob.create_after_upload! \
-        io: file_fixture(filename).open,
-        filename: filename, content_type: content_type
+    def create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", metadata: nil)
+      ActiveStorage::Blob.create_after_upload! io: file_fixture(filename).open, filename: filename, content_type: content_type, metadata: metadata
     end
 
     def create_blob_before_direct_upload(filename: "hello.txt", byte_size:, checksum:, content_type: "text/plain")
       ActiveStorage::Blob.create_before_direct_upload! filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type
     end
 
-    def read_image_variant(variant)
-      MiniMagick::Image.open variant.service.send(:path_for, variant.key)
+    def read_image(blob_or_variant)
+      MiniMagick::Image.open blob_or_variant.service.send(:path_for, blob_or_variant.key)
     end
 end
 
diff --git a/activestorage/yarn.lock b/activestorage/yarn.lock
index dd09577445..41742be201 100644
--- a/activestorage/yarn.lock
+++ b/activestorage/yarn.lock
@@ -1219,12 +1219,6 @@ escope@^3.6.0:
     esrecurse "^4.1.0"
     estraverse "^4.1.1"
 
-eslint-config-airbnb-base@^11.3.1:
-  version "11.3.1"
-  resolved "https://registry.yarnpkg.com/eslint-config-airbnb-base/-/eslint-config-airbnb-base-11.3.1.tgz#c0ab108c9beed503cb999e4c60f4ef98eda0ed30"
-  dependencies:
-    eslint-restricted-globals "^0.1.1"
-
 eslint-import-resolver-node@^0.3.1:
   version "0.3.1"
   resolved "https://registry.yarnpkg.com/eslint-import-resolver-node/-/eslint-import-resolver-node-0.3.1.tgz#4422574cde66a9a7b099938ee4d508a199e0e3cc"
@@ -1254,10 +1248,6 @@ eslint-plugin-import@^2.7.0:
     minimatch "^3.0.3"
     read-pkg-up "^2.0.0"
 
-eslint-restricted-globals@^0.1.1:
-  version "0.1.1"
-  resolved "https://registry.yarnpkg.com/eslint-restricted-globals/-/eslint-restricted-globals-0.1.1.tgz#35f0d5cbc64c2e3ed62e93b4b1a7af05ba7ed4d7"
-
 eslint-scope@^3.7.1:
   version "3.7.1"
   resolved "https://registry.yarnpkg.com/eslint-scope/-/eslint-scope-3.7.1.tgz#3d63c3edfda02e06e01a452ad88caacc7cdcb6e8"
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index f158d5357d..42c4406967 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,273 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Changed default behaviour of `ActiveSupport::SecurityUtils.secure_compare`,
+    to make it not leak length information even for variable length string.
+
+    Renamed old `ActiveSupport::SecurityUtils.secure_compare` to `fixed_length_secure_compare`,
+    and started raising `ArgumentError` in case of length mismatch of passed strings.
+
+    *Vipul A M*
+
+*   Make `ActiveSupport::TimeZone.all` return only time zones that are in
+    `ActiveSupport::TimeZone::MAPPING`.
+
+    Fixes #7245.
+
+    *Chris LaRose*
+
+*   MemCacheStore: Support expiring counters.
+
+    Pass `expires_in: [seconds]` to `#increment` and `#decrement` options
+    to set the Memcached TTL (time-to-live) if the counter doesn't exist.
+    If the counter exists, Memcached doesn't extend its expiry when it's
+    incremented or decremented.
+
+    ```
+    Rails.cache.increment("my_counter", 1, expires_in: 2.minutes)
+    ```
+
+    *Takumasa Ochi*
+
+*   Handle `TZInfo::AmbiguousTime` errors
+
+    Make `ActiveSupport::TimeWithZone` match Ruby's handling of ambiguous
+    times by choosing the later period, e.g.
+
+    Ruby:
+    ```
+    ENV["TZ"] = "Europe/Moscow"
+    Time.local(2014, 10, 26, 1, 0, 0)   # => 2014-10-26 01:00:00 +0300
+    ```
+
+    Before:
+    ```
+    >> "2014-10-26 01:00:00".in_time_zone("Moscow")
+    TZInfo::AmbiguousTime: 26/10/2014 01:00 is an ambiguous local time.
+    ```
+
+    After:
+    ```
+    >> "2014-10-26 01:00:00".in_time_zone("Moscow")
+    => Sun, 26 Oct 2014 01:00:00 MSK +03:00
+    ```
+
+    Fixes #17395.
+
+    *Andrew White*
+
+*   Redis cache store.
+
+    ```
+    # Defaults to `redis://localhost:6379/0`. Only use for dev/test.
+    config.cache_store = :redis_cache_store
+
+    # Supports all common cache store options (:namespace, :compress,
+    # :compress_threshold, :expires_in, :race_condition_tool) and all
+    # Redis options.
+    cache_password = Rails.application.secrets.redis_cache_password
+    config.cache_store = :redis_cache_store, driver: :hiredis,
+      namespace: 'myapp-cache', compress: true, timeout: 1,
+      url: "redis://:#{cache_password}@myapp-cache-1:6379/0"
+
+    # Supports Redis::Distributed with multiple hosts
+    config.cache_store = :redis_cache_store, driver: :hiredis
+      namespace: 'myapp-cache', compress: true,
+      url: %w[
+        redis://myapp-cache-1:6379/0
+        redis://myapp-cache-1:6380/0
+        redis://myapp-cache-2:6379/0
+        redis://myapp-cache-2:6380/0
+        redis://myapp-cache-3:6379/0
+        redis://myapp-cache-3:6380/0
+      ]
+
+    # Or pass a builder block
+    config.cache_store = :redis_cache_store,
+      namespace: 'myapp-cache', compress: true,
+      redis: -> { Redis.new … }
+    ```
+
+    Deployment note: Take care to use a *dedicated Redis cache* rather
+    than pointing this at your existing Redis server. It won't cope well
+    with mixed usage patterns and it won't expire cache entries by default.
+
+    Redis cache server setup guide: https://redis.io/topics/lru-cache
+
+    *Jeremy Daer*
+
+*   Cache: Enable compression by default for values > 1kB.
+
+    Compression has long been available, but opt-in and at a 16kB threshold.
+    It wasn't enabled by default due to CPU cost. Today it's cheap and typical
+    cache data is eminently compressible, such as HTML or JSON fragments.
+    Compression dramatically reduces Memcached/Redis mem usage, which means
+    the same cache servers can store more data, which means higher hit rates.
+
+    To disable compression, pass `compress: false` to the initializer.
+
+    *Jeremy Daer*
+
+*   Allow `Range#include?` on TWZ ranges
+
+    In #11474 we prevented TWZ ranges being iterated over which matched
+    Ruby's handling of Time ranges and as a consequence `include?`
+    stopped working with both Time ranges and TWZ ranges. However in
+    ruby/ruby@b061634 support was added for `include?` to use `cover?`
+    for 'linear' objects. Since we have no way of making Ruby consider
+    TWZ instances as 'linear' we have to override `Range#include?`.
+
+    Fixes #30799.
+
+    *Andrew White*
+
+*   Fix acronym support in `humanize`
+
+    Acronym inflections are stored with lowercase keys in the hash but
+    the match wasn't being lowercased before being looked up in the hash.
+    This shouldn't have any performance impact because before it would
+    fail to find the acronym and perform the `downcase` operation anyway.
+
+    Fixes #31052.
+
+    *Andrew White*
+
+*   Add same method signature for `Time#prev_year` and `Time#next_year`
+    in accordance with `Date#prev_year`, `Date#next_year`.
+
+    Allows pass argument for `Time#prev_year` and `Time#next_year`.
+
+    Before:
+    ```
+    Time.new(2017, 9, 16, 17, 0).prev_year    # => 2016-09-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).prev_year(1)
+    # => ArgumentError: wrong number of arguments (given 1, expected 0)
+
+    Time.new(2017, 9, 16, 17, 0).next_year    # => 2018-09-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).next_year(1)
+    # => ArgumentError: wrong number of arguments (given 1, expected 0)
+    ```
+
+    After:
+    ```
+    Time.new(2017, 9, 16, 17, 0).prev_year    # => 2016-09-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).prev_year(1) # => 2016-09-16 17:00:00 +0300
+
+    Time.new(2017, 9, 16, 17, 0).next_year    # => 2018-09-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).next_year(1) # => 2018-09-16 17:00:00 +0300
+    ```
+
+    *bogdanvlviv*
+
+*   Add same method signature for `Time#prev_month` and `Time#next_month`
+    in accordance with `Date#prev_month`, `Date#next_month`.
+
+    Allows pass argument for `Time#prev_month` and `Time#next_month`.
+
+    Before:
+    ```
+    Time.new(2017, 9, 16, 17, 0).prev_month    # => 2017-08-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).prev_month(1)
+    # => ArgumentError: wrong number of arguments (given 1, expected 0)
+
+    Time.new(2017, 9, 16, 17, 0).next_month    # => 2017-10-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).next_month(1)
+    # => ArgumentError: wrong number of arguments (given 1, expected 0)
+    ```
+
+    After:
+    ```
+    Time.new(2017, 9, 16, 17, 0).prev_month    # => 2017-08-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).prev_month(1) # => 2017-08-16 17:00:00 +0300
+
+    Time.new(2017, 9, 16, 17, 0).next_month    # => 2017-10-16 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).next_month(1) # => 2017-10-16 17:00:00 +0300
+    ```
+
+    *bogdanvlviv*
+
+*   Add same method signature for `Time#prev_day` and `Time#next_day`
+    in accordance with `Date#prev_day`, `Date#next_day`.
+
+    Allows pass argument for `Time#prev_day` and `Time#next_day`.
+
+    Before:
+    ```
+    Time.new(2017, 9, 16, 17, 0).prev_day    # => 2017-09-15 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).prev_day(1)
+    # => ArgumentError: wrong number of arguments (given 1, expected 0)
+
+    Time.new(2017, 9, 16, 17, 0).next_day    # => 2017-09-17 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).next_day(1)
+    # => ArgumentError: wrong number of arguments (given 1, expected 0)
+    ```
+
+    After:
+    ```
+    Time.new(2017, 9, 16, 17, 0).prev_day    # => 2017-09-15 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).prev_day(1) # => 2017-09-15 17:00:00 +0300
+
+    Time.new(2017, 9, 16, 17, 0).next_day    # => 2017-09-17 17:00:00 +0300
+    Time.new(2017, 9, 16, 17, 0).next_day(1) # => 2017-09-17 17:00:00 +0300
+    ```
+
+    *bogdanvlviv*
+
+*   `IO#to_json` now returns the `to_s` representation, rather than
+    attempting to convert to an array. This fixes a bug where `IO#to_json`
+    would raise an `IOError` when called on an unreadable object.
+
+    Fixes #26132.
+
+    *Paul Kuruvilla*
+
+*   Remove deprecated `halt_callback_chains_on_return_false` option.
+
+    *Rafael Mendonça França*
+
+*   Remove deprecated `:if` and `:unless` string filter for callbacks.
+
+    *Rafael Mendonça França*
+
+*   `Hash#slice` now falls back to Ruby 2.5+'s built-in definition if defined.
+
+    *Akira Matsuda*
+
+*   Deprecate `secrets.secret_token`.
+
+    The architecture for secrets had a big upgrade between Rails 3 and Rails 4,
+    when the default changed from using `secret_token` to `secret_key_base`.
+
+    `secret_token` has been soft deprecated in documentation for four years
+    but is still in place to support apps created before Rails 4.
+    Deprecation warnings have been added to help developers upgrade their
+    applications to `secret_key_base`.
+
+    *claudiob*, *Kasper Timm Hansen*
+
+*   Return an instance of `HashWithIndifferentAccess` from `HashWithIndifferentAccess#transform_keys`.
+
+    *Yuji Yaginuma*
+
+*   Add key rotation support to `MessageEncryptor` and `MessageVerifier`
+
+    This change introduces a `rotate` method to both the `MessageEncryptor` and
+    `MessageVerifier` classes. This method accepts the same arguments and
+    options as the given classes' constructor. The `encrypt_and_verify` method
+    for `MessageEncryptor` and the `verified` method for `MessageVerifier` also
+    accept an optional keyword argument `:on_rotation` block which is called
+    when a rotated instance is used to decrypt or verify the message.
+
+    *Michael J Coyne*
+
+*   Deprecate `Module#reachable?` method.
+
+    *bogdanvlviv*
+
 *   Add `config/credentials.yml.enc` to store production app secrets.
 
     Allows saving any authentication credentials for third party services
@@ -30,12 +300,12 @@
     Previously:
 
         'one_two'.camelize(true)
-        => nil
+        # => nil
 
     Now:
 
         'one_two'.camelize(true)
-        => ArgumentError: Invalid option, use either :upper or :lower.
+        # => ArgumentError: Invalid option, use either :upper or :lower.
 
     *Ricardo Díaz*
 
@@ -50,12 +320,12 @@
     Prior to Rails 5.1:
 
         5.minutes % 2.minutes
-        => 60
+        # => 60
 
     Now:
 
         5.minutes % 2.minutes
-        => 1 minute
+        # => 1 minute
 
     Fixes #29603 and #29743.
 
diff --git a/activesupport/README.rdoc b/activesupport/README.rdoc
index 8b47933bd2..c770324be8 100644
--- a/activesupport/README.rdoc
+++ b/activesupport/README.rdoc
@@ -30,7 +30,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index 79b12f36b9..68be94f99d 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -24,11 +24,11 @@
 #++
 
 require "securerandom"
-require_relative "active_support/dependencies/autoload"
-require_relative "active_support/version"
-require_relative "active_support/logger"
-require_relative "active_support/lazy_load_hooks"
-require_relative "active_support/core_ext/date_and_time/compatibility"
+require "active_support/dependencies/autoload"
+require "active_support/version"
+require "active_support/logger"
+require "active_support/lazy_load_hooks"
+require "active_support/core_ext/date_and_time/compatibility"
 
 module ActiveSupport
   extend ActiveSupport::Autoload
@@ -82,18 +82,6 @@ module ActiveSupport
 
   cattr_accessor :test_order # :nodoc:
 
-  def self.halt_callback_chains_on_return_false
-    ActiveSupport::Deprecation.warn(<<-MSG.squish)
-      ActiveSupport.halt_callback_chains_on_return_false is deprecated and will be removed in Rails 5.2.
-    MSG
-  end
-
-  def self.halt_callback_chains_on_return_false=(value)
-    ActiveSupport::Deprecation.warn(<<-MSG.squish)
-      ActiveSupport.halt_callback_chains_on_return_false= is deprecated and will be removed in Rails 5.2.
-    MSG
-  end
-
   def self.to_time_preserves_timezone
     DateAndTime::Compatibility.preserve_timezone
   end
diff --git a/activesupport/lib/active_support/all.rb b/activesupport/lib/active_support/all.rb
index 6638b25419..4adf446af8 100644
--- a/activesupport/lib/active_support/all.rb
+++ b/activesupport/lib/active_support/all.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "time"
-require_relative "core_ext"
+require "active_support/time"
+require "active_support/core_ext"
diff --git a/activesupport/lib/active_support/benchmarkable.rb b/activesupport/lib/active_support/benchmarkable.rb
index 5573f6750e..f481d68198 100644
--- a/activesupport/lib/active_support/benchmarkable.rb
+++ b/activesupport/lib/active_support/benchmarkable.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/benchmark"
-require_relative "core_ext/hash/keys"
+require "active_support/core_ext/benchmark"
+require "active_support/core_ext/hash/keys"
 
 module ActiveSupport
   module Benchmarkable
diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 49d8965cb1..395aa5e8f1 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -1,21 +1,22 @@
 # frozen_string_literal: true
 
 require "zlib"
-require_relative "core_ext/array/extract_options"
-require_relative "core_ext/array/wrap"
-require_relative "core_ext/module/attribute_accessors"
-require_relative "core_ext/numeric/bytes"
-require_relative "core_ext/numeric/time"
-require_relative "core_ext/object/to_param"
-require_relative "core_ext/string/inflections"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/numeric/bytes"
+require "active_support/core_ext/numeric/time"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/string/inflections"
 
 module ActiveSupport
   # See ActiveSupport::Cache::Store for documentation.
   module Cache
-    autoload :FileStore,     "active_support/cache/file_store"
-    autoload :MemoryStore,   "active_support/cache/memory_store"
-    autoload :MemCacheStore, "active_support/cache/mem_cache_store"
-    autoload :NullStore,     "active_support/cache/null_store"
+    autoload :FileStore,        "active_support/cache/file_store"
+    autoload :MemoryStore,      "active_support/cache/memory_store"
+    autoload :MemCacheStore,    "active_support/cache/mem_cache_store"
+    autoload :NullStore,        "active_support/cache/null_store"
+    autoload :RedisCacheStore,  "active_support/cache/redis_cache_store"
 
     # These options mean something to all cache implementations. Individual cache
     # implementations may support additional options.
@@ -90,11 +91,16 @@ module ActiveSupport
       private
         def retrieve_cache_key(key)
           case
-          when key.respond_to?(:cache_key_with_version) then key.cache_key_with_version
-          when key.respond_to?(:cache_key)              then key.cache_key
-          when key.is_a?(Array)                         then key.map { |element| retrieve_cache_key(element) }.to_param
-          when key.respond_to?(:to_a)                   then retrieve_cache_key(key.to_a)
-          else                                               key.to_param
+          when key.respond_to?(:cache_key_with_version)
+            key.cache_key_with_version
+          when key.respond_to?(:cache_key)
+            key.cache_key
+          when key.is_a?(Hash)
+            key.sort_by { |k, _| k.to_s }.collect { |k, v| "#{k}=#{v}" }.to_param
+          when key.respond_to?(:to_a)
+            key.to_a.collect { |element| retrieve_cache_key(element) }.to_param
+          else
+            key.to_param
           end.to_s
         end
 
@@ -148,12 +154,11 @@ module ActiveSupport
     #   cache.namespace = -> { @last_mod_time }  # Set the namespace to a variable
     #   @last_mod_time = Time.now  # Invalidate the entire cache by changing namespace
     #
-    # Caches can also store values in a compressed format to save space and
-    # reduce time spent sending data. Since there is overhead, values must be
-    # large enough to warrant compression. To turn on compression either pass
-    # <tt>compress: true</tt> in the initializer or as an option to +fetch+
-    # or +write+. To specify the threshold at which to compress values, set the
-    # <tt>:compress_threshold</tt> option. The default threshold is 16K.
+    # Cached data larger than 1kB are compressed by default. To turn off
+    # compression, pass <tt>compress: false</tt> to the initializer or to
+    # individual +fetch+ or +write+ method calls. The 1kB compression
+    # threshold is configurable with the <tt>:compress_threshold</tt> option,
+    # specified in bytes.
     class Store
       cattr_accessor :logger, instance_writer: true
 
@@ -212,8 +217,7 @@ module ActiveSupport
       # ask whether you should force a cache write. Otherwise, it's clearer to
       # just call <tt>Cache#write</tt>.
       #
-      # Setting <tt>:compress</tt> will store a large cache entry set by the call
-      # in a compressed format.
+      # Setting <tt>compress: false</tt> disables compression of the cache entry.
       #
       # Setting <tt>:expires_in</tt> will set an expiration time on the cache.
       # All caches support auto-expiring content after a specified number of
@@ -562,34 +566,34 @@ module ActiveSupport
           end
         end
 
-        # Prefixes a key with the namespace. Namespace and key will be delimited
-        # with a colon.
-        def normalize_key(key, options)
-          key = expanded_key(key)
-          namespace = options[:namespace] if options
-          prefix = namespace.is_a?(Proc) ? namespace.call : namespace
-          key = "#{prefix}:#{key}" if prefix
-          key
+        # Expands and namespaces the cache key. May be overridden by
+        # cache stores to do additional normalization.
+        def normalize_key(key, options = nil)
+          namespace_key Cache.expand_cache_key(key), options
         end
 
-        # Expands key to be a consistent string value. Invokes +cache_key+ if
-        # object responds to +cache_key+. Otherwise, +to_param+ method will be
-        # called. If the key is a Hash, then keys will be sorted alphabetically.
-        def expanded_key(key)
-          return key.cache_key.to_s if key.respond_to?(:cache_key)
+        # Prefix the key with a namespace string:
+        #
+        #   namespace_key 'foo', namespace: 'cache'
+        #   # => 'cache:foo'
+        #
+        # With a namespace block:
+        #
+        #   namespace_key 'foo', namespace: -> { 'cache' }
+        #   # => 'cache:foo'
+        def namespace_key(key, options = nil)
+          options = merged_options(options)
+          namespace = options[:namespace]
 
-          case key
-          when Array
-            if key.size > 1
-              key = key.collect { |element| expanded_key(element) }
-            else
-              key = key.first
-            end
-          when Hash
-            key = key.sort_by { |k, _| k.to_s }.collect { |k, v| "#{k}=#{v}" }
+          if namespace.respond_to?(:call)
+            namespace = namespace.call
           end
 
-          key.to_param
+          if namespace
+            "#{namespace}:#{key}"
+          else
+            key
+          end
         end
 
         def normalize_version(key, options = nil)
@@ -658,7 +662,7 @@ module ActiveSupport
     class Entry # :nodoc:
       attr_reader :version
 
-      DEFAULT_COMPRESS_LIMIT = 16.kilobytes
+      DEFAULT_COMPRESS_LIMIT = 1.kilobyte
 
       # Creates a new cache entry for the specified value. Options supported are
       # +:compress+, +:compress_threshold+, and +:expires_in+.
@@ -733,8 +737,8 @@ module ActiveSupport
 
       private
         def should_compress?(value, options)
-          if value && options[:compress]
-            compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT
+          if value && options.fetch(:compress, true)
+            compress_threshold = options.fetch(:compress_threshold, DEFAULT_COMPRESS_LIMIT)
             serialized_value_size = (value.is_a?(String) ? value : Marshal.dump(value)).bytesize
 
             return true if serialized_value_size >= compress_threshold
diff --git a/activesupport/lib/active_support/cache/file_store.rb b/activesupport/lib/active_support/cache/file_store.rb
index 28df2c066e..0812cc34c7 100644
--- a/activesupport/lib/active_support/cache/file_store.rb
+++ b/activesupport/lib/active_support/cache/file_store.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/marshal"
-require_relative "../core_ext/file/atomic"
-require_relative "../core_ext/string/conversions"
+require "active_support/core_ext/marshal"
+require "active_support/core_ext/file/atomic"
+require "active_support/core_ext/string/conversions"
 require "uri/common"
 
 module ActiveSupport
@@ -39,9 +39,8 @@ module ActiveSupport
       def cleanup(options = nil)
         options = merged_options(options)
         search_dir(cache_path) do |fname|
-          key = file_path_key(fname)
-          entry = read_entry(key, options)
-          delete_entry(key, options) if entry && entry.expired?
+          entry = read_entry(fname, options)
+          delete_entry(fname, options) if entry && entry.expired?
         end
       end
 
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index d7bd914722..50f072388d 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -8,8 +8,8 @@ rescue LoadError => e
 end
 
 require "digest/md5"
-require_relative "../core_ext/marshal"
-require_relative "../core_ext/array/extract_options"
+require "active_support/core_ext/marshal"
+require "active_support/core_ext/array/extract_options"
 
 module ActiveSupport
   module Cache
@@ -122,7 +122,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:increment, name, amount: amount) do
           rescue_error_with nil do
-            @data.incr(normalize_key(name, options), amount)
+            @data.incr(normalize_key(name, options), amount, options[:expires_in])
           end
         end
       end
@@ -135,7 +135,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:decrement, name, amount: amount) do
           rescue_error_with nil do
-            @data.decr(normalize_key(name, options), amount)
+            @data.decr(normalize_key(name, options), amount, options[:expires_in])
           end
         end
       end
diff --git a/activesupport/lib/active_support/cache/redis_cache_store.rb b/activesupport/lib/active_support/cache/redis_cache_store.rb
new file mode 100644
index 0000000000..3cf002f67e
--- /dev/null
+++ b/activesupport/lib/active_support/cache/redis_cache_store.rb
@@ -0,0 +1,404 @@
+# frozen_string_literal: true
+
+begin
+  gem "redis", ">= 4.0.1"
+  require "redis"
+  require "redis/distributed"
+rescue LoadError
+  warn "The Redis cache store requires the redis gem, version 4.0.1 or later. Please add it to your Gemfile: `gem \"redis\", \"~> 4.0\"`"
+  raise
+end
+
+# Prefer the hiredis driver but don't require it.
+begin
+  require "redis/connection/hiredis"
+rescue LoadError
+end
+
+require "digest/sha2"
+require "active_support/core_ext/marshal"
+
+module ActiveSupport
+  module Cache
+    # Redis cache store.
+    #
+    # Deployment note: Take care to use a *dedicated Redis cache* rather
+    # than pointing this at your existing Redis server. It won't cope well
+    # with mixed usage patterns and it won't expire cache entries by default.
+    #
+    # Redis cache server setup guide: https://redis.io/topics/lru-cache
+    #
+    # * Supports vanilla Redis, hiredis, and Redis::Distributed.
+    # * Supports Memcached-like sharding across Redises with Redis::Distributed.
+    # * Fault tolerant. If the Redis server is unavailable, no exceptions are
+    #   raised. Cache fetches are all misses and writes are dropped.
+    # * Local cache. Hot in-memory primary cache within block/middleware scope.
+    # * +read_multi+ and +write_multi+ support for Redis mget/mset. Use Redis::Distributed
+    #   4.0.1+ for distributed mget support.
+    # * +delete_matched+ support for Redis KEYS globs.
+    class RedisCacheStore < Store
+      # Keys are truncated with their own SHA2 digest if they exceed 1kB
+      MAX_KEY_BYTESIZE = 1024
+
+      DEFAULT_REDIS_OPTIONS = {
+        connect_timeout:    20,
+        read_timeout:       1,
+        write_timeout:      1,
+        reconnect_attempts: 0,
+      }
+
+      DEFAULT_ERROR_HANDLER = -> (method:, returning:, exception:) {
+        logger.error { "RedisCacheStore: #{method} failed, returned #{returning.inspect}: #{e.class}: #{e.message}" } if logger
+      }
+
+      DELETE_GLOB_LUA = "for i, name in ipairs(redis.call('KEYS', ARGV[1])) do redis.call('DEL', name); end"
+      private_constant :DELETE_GLOB_LUA
+
+      # Support raw values in the local cache strategy.
+      module LocalCacheWithRaw # :nodoc:
+        private
+          def read_entry(key, options)
+            entry = super
+            if options[:raw] && local_cache && entry
+              entry = deserialize_entry(entry.value)
+            end
+            entry
+          end
+
+          def write_entry(key, entry, options)
+            if options[:raw] && local_cache
+              raw_entry = Entry.new(entry.value.to_s)
+              raw_entry.expires_at = entry.expires_at
+              super(key, raw_entry, options)
+            else
+              super
+            end
+          end
+
+          def write_multi_entries(entries, options)
+            if options[:raw] && local_cache
+              raw_entries = entries.map do |key, entry|
+                raw_entry = Entry.new(entry.value.to_s)
+                raw_entry.expires_at = entry.expires_at
+              end.to_h
+
+              super(raw_entries, options)
+            else
+              super
+            end
+          end
+      end
+
+      prepend Strategy::LocalCache
+      prepend LocalCacheWithRaw
+
+      class << self
+        # Factory method to create a new Redis instance.
+        #
+        # Handles four options: :redis block, :redis instance, single :url
+        # string, and multiple :url strings.
+        #
+        #   Option  Class       Result
+        #   :redis  Proc    ->  options[:redis].call
+        #   :redis  Object  ->  options[:redis]
+        #   :url    String  ->  Redis.new(url: …)
+        #   :url    Array   ->  Redis::Distributed.new([{ url: … }, { url: … }, …])
+        #
+        def build_redis(redis: nil, url: nil, **redis_options) #:nodoc:
+          urls = Array(url)
+
+          if redis.respond_to?(:call)
+            redis.call
+          elsif redis
+            redis
+          elsif urls.size > 1
+            build_redis_distributed_client urls: urls, **redis_options
+          else
+            build_redis_client url: urls.first, **redis_options
+          end
+        end
+
+        private
+          def build_redis_distributed_client(urls:, **redis_options)
+            ::Redis::Distributed.new([], DEFAULT_REDIS_OPTIONS.merge(redis_options)).tap do |dist|
+              urls.each { |u| dist.add_node url: u }
+            end
+          end
+
+          def build_redis_client(url:, **redis_options)
+            ::Redis.new DEFAULT_REDIS_OPTIONS.merge(redis_options.merge(url: url))
+          end
+      end
+
+      attr_reader :redis_options
+      attr_reader :max_key_bytesize
+
+      # Creates a new Redis cache store.
+      #
+      # Handles three options: block provided to instantiate, single URL
+      # provided, and multiple URLs provided.
+      #
+      #   :redis Proc   -> options[:redis].call
+      #   :url   String -> Redis.new(url: …)
+      #   :url   Array  -> Redis::Distributed.new([{ url: … }, { url: … }, …])
+      #
+      # No namespace is set by default. Provide one if the Redis cache
+      # server is shared with other apps: <tt>namespace: 'myapp-cache'<tt>.
+      #
+      # Compression is enabled by default with a 1kB threshold, so cached
+      # values larger than 1kB are automatically compressed. Disable by
+      # passing <tt>cache: false</tt> or change the threshold by passing
+      # <tt>compress_threshold: 4.kilobytes</tt>.
+      #
+      # No expiry is set on cache entries by default. Redis is expected to
+      # be configured with an eviction policy that automatically deletes
+      # least-recently or -frequently used keys when it reaches max memory.
+      # See https://redis.io/topics/lru-cache for cache server setup.
+      #
+      # Race condition TTL is not set by default. This can be used to avoid
+      # "thundering herd" cache writes when hot cache entries are expired.
+      # See <tt>ActiveSupport::Cache::Store#fetch</tt> for more.
+      def initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, expires_in: nil, race_condition_ttl: nil, error_handler: DEFAULT_ERROR_HANDLER, **redis_options)
+        @redis_options = redis_options
+
+        @max_key_bytesize = MAX_KEY_BYTESIZE
+        @error_handler = error_handler
+
+        super namespace: namespace,
+          compress: compress, compress_threshold: compress_threshold,
+          expires_in: expires_in, race_condition_ttl: race_condition_ttl
+      end
+
+      def redis
+        @redis ||= self.class.build_redis(**redis_options)
+      end
+
+      def inspect
+        instance = @redis || @redis_options
+        "<##{self.class} options=#{options.inspect} redis=#{instance.inspect}>"
+      end
+
+      # Cache Store API implementation.
+      #
+      # Read multiple values at once. Returns a hash of requested keys ->
+      # fetched values.
+      def read_multi(*names)
+        if mget_capable?
+          read_multi_mget(*names)
+        else
+          super
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Supports Redis KEYS glob patterns:
+      #
+      #   h?llo matches hello, hallo and hxllo
+      #   h*llo matches hllo and heeeello
+      #   h[ae]llo matches hello and hallo, but not hillo
+      #   h[^e]llo matches hallo, hbllo, ... but not hello
+      #   h[a-b]llo matches hallo and hbllo
+      #
+      # Use \ to escape special characters if you want to match them verbatim.
+      #
+      # See https://redis.io/commands/KEYS for more.
+      #
+      # Failsafe: Raises errors.
+      def delete_matched(matcher, options = nil)
+        instrument :delete_matched, matcher do
+          case matcher
+          when String
+            redis.eval DELETE_GLOB_LUA, [], [namespace_key(matcher, options)]
+          else
+            raise ArgumentError, "Only Redis glob strings are supported: #{matcher.inspect}"
+          end
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Increment a cached value. This method uses the Redis incr atomic
+      # operator and can only be used on values written with the :raw option.
+      # Calling it on a value not stored with :raw will initialize that value
+      # to zero.
+      #
+      # Failsafe: Raises errors.
+      def increment(name, amount = 1, options = nil)
+        instrument :increment, name, amount: amount do
+          redis.incrby normalize_key(name, options), amount
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Decrement a cached value. This method uses the Redis decr atomic
+      # operator and can only be used on values written with the :raw option.
+      # Calling it on a value not stored with :raw will initialize that value
+      # to zero.
+      #
+      # Failsafe: Raises errors.
+      def decrement(name, amount = 1, options = nil)
+        instrument :decrement, name, amount: amount do
+          redis.decrby normalize_key(name, options), amount
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Removes expired entries. Handled natively by Redis least-recently-/
+      # least-frequently-used expiry, so manual cleanup is not supported.
+      def cleanup(options = nil)
+        super
+      end
+
+      # Clear the entire cache on all Redis servers. Safe to use on
+      # shared servers if the cache is namespaced.
+      #
+      # Failsafe: Raises errors.
+      def clear(options = nil)
+        failsafe :clear do
+          if namespace = merged_options(options)[namespace]
+            delete_matched "*", namespace: namespace
+          else
+            redis.flushdb
+          end
+        end
+      end
+
+      def mget_capable? #:nodoc:
+        set_redis_capabilities unless defined? @mget_capable
+        @mget_capable
+      end
+
+      def mset_capable? #:nodoc:
+        set_redis_capabilities unless defined? @mset_capable
+        @mset_capable
+      end
+
+      private
+        def set_redis_capabilities
+          case redis
+          when Redis::Distributed
+            @mget_capable = true
+            @mset_capable = false
+          else
+            @mget_capable = true
+            @mset_capable = true
+          end
+        end
+
+        # Store provider interface:
+        # Read an entry from the cache.
+        def read_entry(key, options = nil)
+          failsafe :read_entry do
+            deserialize_entry redis.get(key)
+          end
+        end
+
+        def read_multi_mget(*names)
+          options = names.extract_options!
+          options = merged_options(options)
+
+          keys = names.map { |name| normalize_key(name, options) }
+          values = redis.mget(*keys)
+
+          names.zip(values).each_with_object({}) do |(name, value), results|
+            if value
+              entry = deserialize_entry(value)
+              unless entry.nil? || entry.expired? || entry.mismatched?(normalize_version(name, options))
+                results[name] = entry.value
+              end
+            end
+          end
+        end
+
+        # Write an entry to the cache.
+        #
+        # Requires Redis 2.6.12+ for extended SET options.
+        def write_entry(key, entry, unless_exist: false, raw: false, expires_in: nil, race_condition_ttl: nil, **options)
+          value = raw ? entry.value.to_s : serialize_entry(entry)
+
+          # If race condition TTL is in use, ensure that cache entries
+          # stick around a bit longer after they would have expired
+          # so we can purposefully serve stale entries.
+          if race_condition_ttl && expires_in && expires_in > 0 && !raw
+            expires_in += 5.minutes
+          end
+
+          failsafe :write_entry do
+            if unless_exist || expires_in
+              modifiers = {}
+              modifiers[:nx] = unless_exist
+              modifiers[:px] = (1000 * expires_in.to_f).ceil if expires_in
+
+              redis.set key, value, modifiers
+            else
+              redis.set key, value
+            end
+          end
+        end
+
+        # Delete an entry from the cache.
+        def delete_entry(key, options)
+          failsafe :delete_entry, returning: false do
+            redis.del key
+          end
+        end
+
+        # Nonstandard store provider API to write multiple values at once.
+        def write_multi_entries(entries, expires_in: nil, **options)
+          if entries.any?
+            if mset_capable? && expires_in.nil?
+              failsafe :write_multi_entries do
+                redis.mapped_mset(entries)
+              end
+            else
+              super
+            end
+          end
+        end
+
+        # Truncate keys that exceed 1kB.
+        def normalize_key(key, options)
+          truncate_key super
+        end
+
+        def truncate_key(key)
+          if key.bytesize > max_key_bytesize
+            suffix = ":sha2:#{Digest::SHA2.hexdigest(key)}"
+            truncate_at = max_key_bytesize - suffix.bytesize
+            "#{key.byteslice(0, truncate_at)}#{suffix}"
+          else
+            key
+          end
+        end
+
+        def deserialize_entry(raw_value)
+          if raw_value
+            entry = Marshal.load(raw_value) rescue raw_value
+            entry.is_a?(Entry) ? entry : Entry.new(entry)
+          end
+        end
+
+        def serialize_entry(entry)
+          Marshal.dump(entry)
+        end
+
+        def failsafe(method, returning: nil)
+          yield
+        rescue ::Redis::BaseConnectionError => e
+          handle_exception exception: e, method: method, returning: returning
+          returning
+        end
+
+        def handle_exception(exception:, method:, returning:)
+          if @error_handler
+            @error_handler.(method: method, exception: exception, returning: returning)
+          end
+        rescue => failsafe
+          warn "RedisCacheStore ignored exception in handle_exception: #{failsafe.class}: #{failsafe.message}\n  #{failsafe.backtrace.join("\n  ")}"
+        end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/cache/strategy/local_cache.rb b/activesupport/lib/active_support/cache/strategy/local_cache.rb
index a3eef1190a..aaa9638fa8 100644
--- a/activesupport/lib/active_support/cache/strategy/local_cache.rb
+++ b/activesupport/lib/active_support/cache/strategy/local_cache.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../core_ext/object/duplicable"
-require_relative "../../core_ext/string/inflections"
-require_relative "../../per_thread_registry"
+require "active_support/core_ext/object/duplicable"
+require "active_support/core_ext/string/inflections"
+require "active_support/per_thread_registry"
 
 module ActiveSupport
   module Cache
diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index e1cbfc945c..0ed4681b7d 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "descendants_tracker"
-require_relative "core_ext/array/extract_options"
-require_relative "core_ext/class/attribute"
-require_relative "core_ext/kernel/reporting"
-require_relative "core_ext/kernel/singleton_class"
-require_relative "core_ext/string/filters"
-require_relative "deprecation"
+require "active_support/concern"
+require "active_support/descendants_tracker"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/string/filters"
+require "active_support/deprecation"
 require "thread"
 
 module ActiveSupport
@@ -298,8 +298,8 @@ module ActiveSupport
           @kind    = kind
           @filter  = filter
           @key     = compute_identifier filter
-          @if      = Array(options[:if])
-          @unless  = Array(options[:unless])
+          @if      = check_conditionals(Array(options[:if]))
+          @unless  = check_conditionals(Array(options[:unless]))
         end
 
         def filter; @key; end
@@ -323,7 +323,7 @@ module ActiveSupport
 
         def duplicates?(other)
           case @filter
-          when Symbol, String
+          when Symbol
             matches?(other.kind, other.filter)
           else
             false
@@ -350,9 +350,21 @@ module ActiveSupport
         end
 
         private
+          def check_conditionals(conditionals)
+            if conditionals.any? { |c| c.is_a?(String) }
+              raise ArgumentError, <<-MSG.squish
+                Passing string to be evaluated in :if and :unless conditional
+                options is not supported. Pass a symbol for an instance method,
+                or a lambda, proc or block, instead.
+              MSG
+            end
+
+            conditionals
+          end
+
           def compute_identifier(filter)
             case filter
-            when String, ::Proc
+            when ::Proc
               filter.object_id
             else
               filter
@@ -427,7 +439,6 @@ module ActiveSupport
         # Filters support:
         #
         #   Symbols:: A method to call.
-        #   Strings:: Some content to evaluate.
         #   Procs::   A proc to call with the object.
         #   Objects:: An object with a <tt>before_foo</tt> method on it to call.
         #
@@ -437,8 +448,6 @@ module ActiveSupport
           case filter
           when Symbol
             new(nil, filter, [], nil)
-          when String
-            new(nil, :instance_exec, [:value], compile_lambda(filter))
           when Conditionals::Value
             new(filter, :call, [:target, :value], nil)
           when ::Proc
@@ -455,10 +464,6 @@ module ActiveSupport
             new(filter, method_to_call, [:target], nil)
           end
         end
-
-        def self.compile_lambda(filter)
-          eval("lambda { |value| #{filter} }")
-        end
       end
 
       # Execute before and after filters in a sequence instead of
@@ -651,26 +656,17 @@ module ActiveSupport
         #
         # ===== Options
         #
-        # * <tt>:if</tt> - A symbol, a string (deprecated) or an array of symbols,
-        #   each naming an instance method or a proc; the callback will be called
-        #   only when they all return a true value.
-        # * <tt>:unless</tt> - A symbol, a string (deprecated) or an array of symbols,
-        #   each naming an instance method or a proc; the callback will be called
-        #   only when they all return a false value.
+        # * <tt>:if</tt> - A symbol or an array of symbols, each naming an instance
+        #   method or a proc; the callback will be called only when they all return
+        #   a true value.
+        # * <tt>:unless</tt> - A symbol or an array of symbols, each naming an
+        #   instance method or a proc; the callback will be called only when they
+        #   all return a false value.
         # * <tt>:prepend</tt> - If +true+, the callback will be prepended to the
         #   existing chain rather than appended.
         def set_callback(name, *filter_list, &block)
           type, filters, options = normalize_callback_params(filter_list, block)
 
-          if options[:if].is_a?(String) || options[:unless].is_a?(String)
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing string to be evaluated in :if and :unless conditional
-              options is deprecated and will be removed in Rails 5.2 without
-              replacement. Pass a symbol for an instance method, or a lambda,
-              proc or block, instead.
-            MSG
-          end
-
           self_chain = get_callbacks name
           mapped = filters.map do |filter|
             Callback.build(self_chain, filter, type, options)
@@ -695,13 +691,6 @@ module ActiveSupport
         def skip_callback(name, *filter_list, &block)
           type, filters, options = normalize_callback_params(filter_list, block)
 
-          if options[:if].is_a?(String) || options[:unless].is_a?(String)
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing string to :if and :unless conditional options is deprecated
-              and will be removed in Rails 5.2 without replacement.
-            MSG
-          end
-
           options[:raise] = true unless options.key?(:raise)
 
           __update_callbacks(name) do |target, chain|
diff --git a/activesupport/lib/active_support/concern.rb b/activesupport/lib/active_support/concern.rb
index 32b5ca986b..b0a0d845e5 100644
--- a/activesupport/lib/active_support/concern.rb
+++ b/activesupport/lib/active_support/concern.rb
@@ -113,7 +113,7 @@ module ActiveSupport
     def append_features(base)
       if base.instance_variable_defined?(:@_dependencies)
         base.instance_variable_get(:@_dependencies) << self
-        return false
+        false
       else
         return false if base < self
         @_dependencies.each { |dep| base.include(dep) }
diff --git a/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb b/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb
new file mode 100644
index 0000000000..a8455c0048
--- /dev/null
+++ b/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require "monitor"
+
+module ActiveSupport
+  module Concurrency
+    # A monitor that will permit dependency loading while blocked waiting for
+    # the lock.
+    class LoadInterlockAwareMonitor < Monitor
+      # Enters an exclusive section, but allows dependency loading while blocked
+      def mon_enter
+        mon_try_enter ||
+          ActiveSupport::Dependencies.interlock.permit_concurrent_loads { super }
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/configurable.rb b/activesupport/lib/active_support/configurable.rb
index 8e8e27b4ec..4d6f7819bb 100644
--- a/activesupport/lib/active_support/configurable.rb
+++ b/activesupport/lib/active_support/configurable.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "ordered_options"
-require_relative "core_ext/array/extract_options"
-require_relative "core_ext/regexp"
+require "active_support/concern"
+require "active_support/ordered_options"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   # Configurable provides a <tt>config</tt> method to store and retrieve
diff --git a/activesupport/lib/active_support/core_ext/array.rb b/activesupport/lib/active_support/core_ext/array.rb
index fdc209ef68..6d83b76882 100644
--- a/activesupport/lib/active_support/core_ext/array.rb
+++ b/activesupport/lib/active_support/core_ext/array.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "array/wrap"
-require_relative "array/access"
-require_relative "array/conversions"
-require_relative "array/extract_options"
-require_relative "array/grouping"
-require_relative "array/prepend_and_append"
-require_relative "array/inquiry"
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/array/access"
+require "active_support/core_ext/array/conversions"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/array/grouping"
+require "active_support/core_ext/array/prepend_and_append"
+require "active_support/core_ext/array/inquiry"
diff --git a/activesupport/lib/active_support/core_ext/array/access.rb b/activesupport/lib/active_support/core_ext/array/access.rb
index d67f99df0e..b7ff7a3907 100644
--- a/activesupport/lib/active_support/core_ext/array/access.rb
+++ b/activesupport/lib/active_support/core_ext/array/access.rb
@@ -35,8 +35,8 @@ class Array
   #   people.without "Aaron", "Todd"
   #   # => ["David", "Rafael"]
   #
-  # Note: This is an optimization of `Enumerable#without` that uses `Array#-`
-  # instead of `Array#reject` for performance reasons.
+  # Note: This is an optimization of <tt>Enumerable#without</tt> that uses <tt>Array#-</tt>
+  # instead of <tt>Array#reject</tt> for performance reasons.
   def without(*elements)
     self - elements
   end
diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index 6e17a81f0f..ea688ed2ea 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../../xml_mini"
-require_relative "../hash/keys"
-require_relative "../string/inflections"
-require_relative "../object/to_param"
-require_relative "../object/to_query"
+require "active_support/xml_mini"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
 
 class Array
   # Converts the array to a comma-separated sentence where the last element is
@@ -181,7 +181,7 @@ class Array
   #   </messages>
   #
   def to_xml(options = {})
-    require_relative "../../builder" unless defined?(Builder)
+    require "active_support/builder" unless defined?(Builder)
 
     options = options.dup
     options[:indent]  ||= 2
diff --git a/activesupport/lib/active_support/core_ext/array/inquiry.rb b/activesupport/lib/active_support/core_ext/array/inquiry.rb
index 4f4a9fa361..92c61bf201 100644
--- a/activesupport/lib/active_support/core_ext/array/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/array/inquiry.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../array_inquirer"
+require "active_support/array_inquirer"
 
 class Array
   # Wraps the array in an +ArrayInquirer+ object, which gives a friendlier way
diff --git a/activesupport/lib/active_support/core_ext/big_decimal.rb b/activesupport/lib/active_support/core_ext/big_decimal.rb
index 5568db689b..9e6a9d6331 100644
--- a/activesupport/lib/active_support/core_ext/big_decimal.rb
+++ b/activesupport/lib/active_support/core_ext/big_decimal.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-require_relative "big_decimal/conversions"
+require "active_support/core_ext/big_decimal/conversions"
diff --git a/activesupport/lib/active_support/core_ext/class.rb b/activesupport/lib/active_support/core_ext/class.rb
index 65e1d68399..1c110fd07b 100644
--- a/activesupport/lib/active_support/core_ext/class.rb
+++ b/activesupport/lib/active_support/core_ext/class.rb
@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 
-require_relative "class/attribute"
-require_relative "class/subclasses"
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/class/subclasses"
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index 3453fc4ac6..7928efb871 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../kernel/singleton_class"
-require_relative "../module/redefine_method"
-require_relative "../array/extract_options"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/core_ext/array/extract_options"
 
 class Class
   # Declare a class-level attribute whose value is inheritable by subclasses.
diff --git a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
index b4dbcc6698..a77354e153 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
@@ -3,4 +3,4 @@
 # cattr_* became mattr_* aliases in 7dfbd91b0780fbd6a1dd9bfbc176e10894871d2d,
 # but we keep this around for libraries that directly require it knowing they
 # want cattr_*. No need to deprecate.
-require_relative "../module/attribute_accessors"
+require "active_support/core_ext/module/attribute_accessors"
diff --git a/activesupport/lib/active_support/core_ext/class/subclasses.rb b/activesupport/lib/active_support/core_ext/class/subclasses.rb
index 4c910feb44..75e65337b7 100644
--- a/activesupport/lib/active_support/core_ext/class/subclasses.rb
+++ b/activesupport/lib/active_support/core_ext/class/subclasses.rb
@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../module/anonymous"
-require_relative "../module/reachable"
-
 class Class
   begin
     # Test if this Ruby supports each_object against singleton_class
diff --git a/activesupport/lib/active_support/core_ext/date.rb b/activesupport/lib/active_support/core_ext/date.rb
index 2a2ed5496f..cce73f2db2 100644
--- a/activesupport/lib/active_support/core_ext/date.rb
+++ b/activesupport/lib/active_support/core_ext/date.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "date/acts_like"
-require_relative "date/blank"
-require_relative "date/calculations"
-require_relative "date/conversions"
-require_relative "date/zones"
+require "active_support/core_ext/date/acts_like"
+require "active_support/core_ext/date/blank"
+require "active_support/core_ext/date/calculations"
+require "active_support/core_ext/date/conversions"
+require "active_support/core_ext/date/zones"
diff --git a/activesupport/lib/active_support/core_ext/date/acts_like.rb b/activesupport/lib/active_support/core_ext/date/acts_like.rb
index 81769129b5..c8077f3774 100644
--- a/activesupport/lib/active_support/core_ext/date/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/date/acts_like.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../object/acts_like"
+require "active_support/core_ext/object/acts_like"
 
 class Date
   # Duck-types as a Date-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 1a19ee8b1e..1cd7acb05d 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../../duration"
-require_relative "../object/acts_like"
-require_relative "zones"
-require_relative "../time/zones"
-require_relative "../date_and_time/calculations"
+require "active_support/duration"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/date/zones"
+require "active_support/core_ext/time/zones"
+require "active_support/core_ext/date_and_time/calculations"
 
 class Date
   include DateAndTime::Calculations
diff --git a/activesupport/lib/active_support/core_ext/date/conversions.rb b/activesupport/lib/active_support/core_ext/date/conversions.rb
index 88fb572725..870119dc7f 100644
--- a/activesupport/lib/active_support/core_ext/date/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date/conversions.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../../inflector/methods"
-require_relative "zones"
-require_relative "../module/redefine_method"
+require "active_support/inflector/methods"
+require "active_support/core_ext/date/zones"
+require "active_support/core_ext/module/redefine_method"
 
 class Date
   DATE_FORMATS = {
diff --git a/activesupport/lib/active_support/core_ext/date/zones.rb b/activesupport/lib/active_support/core_ext/date/zones.rb
index 1aed070df0..2dcf97cff8 100644
--- a/activesupport/lib/active_support/core_ext/date/zones.rb
+++ b/activesupport/lib/active_support/core_ext/date/zones.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../date_and_time/zones"
+require "active_support/core_ext/date_and_time/zones"
 
 class Date
   include DateAndTime::Zones
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
index 8546f7e57b..f6cb1a384c 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../object/try"
+require "active_support/core_ext/object/try"
 
 module DateAndTime
   module Calculations
@@ -20,9 +20,9 @@ module DateAndTime
       advance(days: -1)
     end
 
-    # Returns a new date/time representing the previous day.
-    def prev_day
-      advance(days: -1)
+    # Returns a new date/time the specified number of days ago.
+    def prev_day(days = 1)
+      advance(days: -days)
     end
 
     # Returns a new date/time representing tomorrow.
@@ -30,9 +30,9 @@ module DateAndTime
       advance(days: 1)
     end
 
-    # Returns a new date/time representing the next day.
-    def next_day
-      advance(days: 1)
+    # Returns a new date/time the specified number of days in the future.
+    def next_day(days = 1)
+      advance(days: days)
     end
 
     # Returns true if the date/time is today.
@@ -188,9 +188,9 @@ module DateAndTime
       end
     end
 
-    # Short-hand for months_since(1).
-    def next_month
-      months_since(1)
+    # Returns a new date/time the specified number of months in the future.
+    def next_month(months = 1)
+      advance(months: months)
     end
 
     # Short-hand for months_since(3)
@@ -198,9 +198,9 @@ module DateAndTime
       months_since(3)
     end
 
-    # Short-hand for years_since(1).
-    def next_year
-      years_since(1)
+    # Returns a new date/time the specified number of years in the future.
+    def next_year(years = 1)
+      advance(years: years)
     end
 
     # Returns a new date/time representing the given day in the previous week.
@@ -223,11 +223,15 @@ module DateAndTime
     end
     alias_method :last_weekday, :prev_weekday
 
+    # Returns a new date/time the specified number of months ago.
+    def prev_month(months = 1)
+      advance(months: -months)
+    end
+
     # Short-hand for months_ago(1).
-    def prev_month
+    def last_month
       months_ago(1)
     end
-    alias_method :last_month, :prev_month
 
     # Short-hand for months_ago(3).
     def prev_quarter
@@ -235,11 +239,15 @@ module DateAndTime
     end
     alias_method :last_quarter, :prev_quarter
 
+    # Returns a new date/time the specified number of years ago.
+    def prev_year(years = 1)
+      advance(years: -years)
+    end
+
     # Short-hand for years_ago(1).
-    def prev_year
+    def last_year
       years_ago(1)
     end
-    alias_method :last_year, :prev_year
 
     # Returns the number of days to the start of the week on the given day.
     # Week is assumed to start on +start_day+, default is
@@ -322,20 +330,28 @@ module DateAndTime
       beginning_of_year..end_of_year
     end
 
-    # Returns specific next occurring day of week
+    # Returns a new date/time representing the next occurrence of the specified day of week.
+    #
+    #   today = Date.today               # => Thu, 14 Dec 2017
+    #   today.next_occurring(:monday)    # => Mon, 18 Dec 2017
+    #   today.next_occurring(:thursday)  # => Thu, 21 Dec 2017
     def next_occurring(day_of_week)
       current_day_number = wday != 0 ? wday - 1 : 6
       from_now = DAYS_INTO_WEEK.fetch(day_of_week) - current_day_number
       from_now += 7 unless from_now > 0
-      since(from_now.days)
+      advance(days: from_now)
     end
 
-    # Returns specific previous occurring day of week
+    # Returns a new date/time representing the previous occurrence of the specified day of week.
+    #
+    #   today = Date.today               # => Thu, 14 Dec 2017
+    #   today.prev_occurring(:monday)    # => Mon, 11 Dec 2017
+    #   today.prev_occurring(:thursday)  # => Thu, 07 Dec 2017
     def prev_occurring(day_of_week)
       current_day_number = wday != 0 ? wday - 1 : 6
       ago = current_day_number - DAYS_INTO_WEEK.fetch(day_of_week)
       ago += 7 unless ago > 0
-      ago(ago.days)
+      advance(days: -ago)
     end
 
     private
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
index 5b3aabf6a5..d33c36ef73 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../module/attribute_accessors"
+require "active_support/core_ext/module/attribute_accessors"
 
 module DateAndTime
   module Compatibility
diff --git a/activesupport/lib/active_support/core_ext/date_time.rb b/activesupport/lib/active_support/core_ext/date_time.rb
index b3d6773e4f..790dbeec1b 100644
--- a/activesupport/lib/active_support/core_ext/date_time.rb
+++ b/activesupport/lib/active_support/core_ext/date_time.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "date_time/acts_like"
-require_relative "date_time/blank"
-require_relative "date_time/calculations"
-require_relative "date_time/compatibility"
-require_relative "date_time/conversions"
+require "active_support/core_ext/date_time/acts_like"
+require "active_support/core_ext/date_time/blank"
+require "active_support/core_ext/date_time/calculations"
+require "active_support/core_ext/date_time/compatibility"
+require "active_support/core_ext/date_time/conversions"
diff --git a/activesupport/lib/active_support/core_ext/date_time/acts_like.rb b/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
index 02acb5fe21..5dccdfe219 100644
--- a/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../object/acts_like"
+require "active_support/core_ext/object/acts_like"
 
 class DateTime
   # Duck-types as a Date-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
index bb9714545e..2d6b49722d 100644
--- a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "../date_and_time/compatibility"
-require_relative "../module/redefine_method"
+require "active_support/core_ext/date_and_time/compatibility"
+require "active_support/core_ext/module/redefine_method"
 
 class DateTime
   include DateAndTime::Compatibility
 
   silence_redefinition_of_method :to_time
 
-  # Either return an instance of `Time` with the same UTC offset
-  # as +self+ or an instance of `Time` representing the same time
+  # Either return an instance of +Time+ with the same UTC offset
+  # as +self+ or an instance of +Time+ representing the same time
   # in the the local system timezone depending on the setting of
   # on the setting of +ActiveSupport.to_time_preserves_timezone+.
   def to_time
diff --git a/activesupport/lib/active_support/core_ext/date_time/conversions.rb b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
index e4c8f9898d..29725c89f7 100644
--- a/activesupport/lib/active_support/core_ext/date_time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../../inflector/methods"
-require_relative "../time/conversions"
-require_relative "calculations"
-require_relative "../../values/time_zone"
+require "active_support/inflector/methods"
+require "active_support/core_ext/time/conversions"
+require "active_support/core_ext/date_time/calculations"
+require "active_support/values/time_zone"
 
 class DateTime
   # Convert to a formatted string. See Time::DATE_FORMATS for predefined formats.
diff --git a/activesupport/lib/active_support/core_ext/file.rb b/activesupport/lib/active_support/core_ext/file.rb
index 3c2364167d..64553bfa4e 100644
--- a/activesupport/lib/active_support/core_ext/file.rb
+++ b/activesupport/lib/active_support/core_ext/file.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-require_relative "file/atomic"
+require "active_support/core_ext/file/atomic"
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index a74a8c15a6..e19aeaa983 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "hash/compact"
-require_relative "hash/conversions"
-require_relative "hash/deep_merge"
-require_relative "hash/except"
-require_relative "hash/indifferent_access"
-require_relative "hash/keys"
-require_relative "hash/reverse_merge"
-require_relative "hash/slice"
-require_relative "hash/transform_values"
+require "active_support/core_ext/hash/compact"
+require "active_support/core_ext/hash/conversions"
+require "active_support/core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/except"
+require "active_support/core_ext/hash/indifferent_access"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/hash/reverse_merge"
+require "active_support/core_ext/hash/slice"
+require "active_support/core_ext/hash/transform_values"
diff --git a/activesupport/lib/active_support/core_ext/hash/conversions.rb b/activesupport/lib/active_support/core_ext/hash/conversions.rb
index 0c0701134e..11d28d12a1 100644
--- a/activesupport/lib/active_support/core_ext/hash/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/hash/conversions.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "../../xml_mini"
-require_relative "../../time"
-require_relative "../object/blank"
-require_relative "../object/to_param"
-require_relative "../object/to_query"
-require_relative "../array/wrap"
-require_relative "reverse_merge"
-require_relative "../string/inflections"
+require "active_support/xml_mini"
+require "active_support/time"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/hash/reverse_merge"
+require "active_support/core_ext/string/inflections"
 
 class Hash
   # Returns a string containing an XML representation of its receiver:
@@ -73,7 +73,7 @@ class Hash
   # configure your own builder with the <tt>:builder</tt> option. The method also accepts
   # options like <tt>:dasherize</tt> and friends, they are forwarded to the builder.
   def to_xml(options = {})
-    require_relative "../../builder" unless defined?(Builder)
+    require "active_support/builder" unless defined?(Builder)
 
     options = options.dup
     options[:indent]  ||= 2
diff --git a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
index 4681d986db..a38f33f128 100644
--- a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
+++ b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../hash_with_indifferent_access"
+require "active_support/hash_with_indifferent_access"
 
 class Hash
   # Returns an <tt>ActiveSupport::HashWithIndifferentAccess</tt> out of its receiver:
diff --git a/activesupport/lib/active_support/core_ext/hash/slice.rb b/activesupport/lib/active_support/core_ext/hash/slice.rb
index 94dc225edb..2bd0a56ea4 100644
--- a/activesupport/lib/active_support/core_ext/hash/slice.rb
+++ b/activesupport/lib/active_support/core_ext/hash/slice.rb
@@ -21,9 +21,8 @@ class Hash
   #   valid_keys = [:mass, :velocity, :time]
   #   search(options.slice(*valid_keys))
   def slice(*keys)
-    keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
-    keys.each_with_object(self.class.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
-  end
+    keys.each_with_object(Hash.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
+  end unless method_defined?(:slice)
 
   # Replaces the hash with only the given keys.
   # Returns a hash containing the removed key/value pairs.
@@ -31,7 +30,6 @@ class Hash
   #   { a: 1, b: 2, c: 3, d: 4 }.slice!(:a, :b)
   #   # => {:c=>3, :d=>4}
   def slice!(*keys)
-    keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
     omit = slice(*self.keys - keys)
     hash = slice(*keys)
     hash.default      = default
diff --git a/activesupport/lib/active_support/core_ext/integer.rb b/activesupport/lib/active_support/core_ext/integer.rb
index df80e7ffdb..d22701306a 100644
--- a/activesupport/lib/active_support/core_ext/integer.rb
+++ b/activesupport/lib/active_support/core_ext/integer.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "integer/multiple"
-require_relative "integer/inflections"
-require_relative "integer/time"
+require "active_support/core_ext/integer/multiple"
+require "active_support/core_ext/integer/inflections"
+require "active_support/core_ext/integer/time"
diff --git a/activesupport/lib/active_support/core_ext/integer/inflections.rb b/activesupport/lib/active_support/core_ext/integer/inflections.rb
index 7192e92346..aef3266f28 100644
--- a/activesupport/lib/active_support/core_ext/integer/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/integer/inflections.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector"
+require "active_support/inflector"
 
 class Integer
   # Ordinalize turns a number into an ordinal string used to denote the
diff --git a/activesupport/lib/active_support/core_ext/integer/time.rb b/activesupport/lib/active_support/core_ext/integer/time.rb
index 30c8f3bcf2..5efb89cf9f 100644
--- a/activesupport/lib/active_support/core_ext/integer/time.rb
+++ b/activesupport/lib/active_support/core_ext/integer/time.rb
@@ -1,29 +1,20 @@
 # frozen_string_literal: true
 
-require_relative "../../duration"
-require_relative "../numeric/time"
+require "active_support/duration"
+require "active_support/core_ext/numeric/time"
 
 class Integer
-  # Enables the use of time calculations and declarations, like <tt>45.minutes +
-  # 2.hours + 4.years</tt>.
+  # Returns a Duration instance matching the number of months provided.
   #
-  # These methods use Time#advance for precise date calculations when using
-  # <tt>from_now</tt>, +ago+, etc. as well as adding or subtracting their
-  # results from a Time object.
-  #
-  #   # equivalent to Time.now.advance(months: 1)
-  #   1.month.from_now
-  #
-  #   # equivalent to Time.now.advance(years: 2)
-  #   2.years.from_now
-  #
-  #   # equivalent to Time.now.advance(months: 4, years: 5)
-  #   (4.months + 5.years).from_now
+  #   2.months # => 2 months
   def months
     ActiveSupport::Duration.months(self)
   end
   alias :month :months
 
+  # Returns a Duration instance matching the number of years provided.
+  #
+  #   2.years # => 2 years
   def years
     ActiveSupport::Duration.years(self)
   end
diff --git a/activesupport/lib/active_support/core_ext/kernel.rb b/activesupport/lib/active_support/core_ext/kernel.rb
index 30810ce315..0f4356fbdd 100644
--- a/activesupport/lib/active_support/core_ext/kernel.rb
+++ b/activesupport/lib/active_support/core_ext/kernel.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "kernel/agnostics"
-require_relative "kernel/concern"
-require_relative "kernel/reporting"
-require_relative "kernel/singleton_class"
+require "active_support/core_ext/kernel/agnostics"
+require "active_support/core_ext/kernel/concern"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/kernel/singleton_class"
diff --git a/activesupport/lib/active_support/core_ext/kernel/concern.rb b/activesupport/lib/active_support/core_ext/kernel/concern.rb
index 32af9981a5..0b2baed780 100644
--- a/activesupport/lib/active_support/core_ext/kernel/concern.rb
+++ b/activesupport/lib/active_support/core_ext/kernel/concern.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../module/concerning"
+require "active_support/core_ext/module/concerning"
 
 module Kernel
   module_function
diff --git a/activesupport/lib/active_support/core_ext/module.rb b/activesupport/lib/active_support/core_ext/module.rb
index 8445643730..d91e3fba6a 100644
--- a/activesupport/lib/active_support/core_ext/module.rb
+++ b/activesupport/lib/active_support/core_ext/module.rb
@@ -1,14 +1,14 @@
 # frozen_string_literal: true
 
-require_relative "module/aliasing"
-require_relative "module/introspection"
-require_relative "module/anonymous"
-require_relative "module/reachable"
-require_relative "module/attribute_accessors"
-require_relative "module/attribute_accessors_per_thread"
-require_relative "module/attr_internal"
-require_relative "module/concerning"
-require_relative "module/delegation"
-require_relative "module/deprecation"
-require_relative "module/redefine_method"
-require_relative "module/remove_method"
+require "active_support/core_ext/module/aliasing"
+require "active_support/core_ext/module/introspection"
+require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/module/reachable"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/attribute_accessors_per_thread"
+require "active_support/core_ext/module/attr_internal"
+require "active_support/core_ext/module/concerning"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/module/deprecation"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/core_ext/module/remove_method"
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
index e667c1f4a4..580baffa2b 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../array/extract_options"
-require_relative "../regexp"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/regexp"
 
 # Extends the module object with class/module and instance accessors for
 # class/module attributes, just like the native attr* accessors for instance
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
index 90a350c5dc..4b9b6ea9bd 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../array/extract_options"
-require_relative "../regexp"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/regexp"
 
 # Extends the module object with class/module and instance accessors for
 # class/module attributes, just like the native attr* accessors for instance
diff --git a/activesupport/lib/active_support/core_ext/module/concerning.rb b/activesupport/lib/active_support/core_ext/module/concerning.rb
index 17c202a24a..800bf213cc 100644
--- a/activesupport/lib/active_support/core_ext/module/concerning.rb
+++ b/activesupport/lib/active_support/core_ext/module/concerning.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../concern"
+require "active_support/concern"
 
 class Module
   # = Bite-sized separation of concerns
@@ -22,7 +22,7 @@ class Module
   #
   # == Using comments:
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -42,7 +42,7 @@ class Module
   #
   # Noisy syntax.
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -70,7 +70,7 @@ class Module
   # increased overhead can be a reasonable tradeoff even if it reduces our
   # at-a-glance perception of how things work.
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -82,7 +82,7 @@ class Module
   # By quieting the mix-in noise, we arrive at a natural, low-ceremony way to
   # separate bite-sized concerns.
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -101,7 +101,7 @@ class Module
   #   end
   #
   #   Todo.ancestors
-  #   # => [Todo, Todo::EventTracking, Object]
+  #   # => [Todo, Todo::EventTracking, ApplicationRecord, Object]
   #
   # This small step has some wonderful ripple effects. We can
   # * grok the behavior of our class in one glance,
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index 1840dc942f..a77f903db5 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "set"
-require_relative "../regexp"
+require "active_support/core_ext/regexp"
 
 class Module
   # Error generated by +delegate+ when a method is called on +nil+ and +allow_nil+
diff --git a/activesupport/lib/active_support/core_ext/module/introspection.rb b/activesupport/lib/active_support/core_ext/module/introspection.rb
index 540385ef6f..c5bb598bd1 100644
--- a/activesupport/lib/active_support/core_ext/module/introspection.rb
+++ b/activesupport/lib/active_support/core_ext/module/introspection.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector"
+require "active_support/inflector"
 
 class Module
   # Returns the name of the module containing this one.
diff --git a/activesupport/lib/active_support/core_ext/module/reachable.rb b/activesupport/lib/active_support/core_ext/module/reachable.rb
index 91b230b46c..e9cbda5245 100644
--- a/activesupport/lib/active_support/core_ext/module/reachable.rb
+++ b/activesupport/lib/active_support/core_ext/module/reachable.rb
@@ -1,10 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "anonymous"
-require_relative "../string/inflections"
+require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/string/inflections"
 
 class Module
   def reachable? #:nodoc:
     !anonymous? && name.safe_constantize.equal?(self)
   end
+  deprecate :reachable?
 end
diff --git a/activesupport/lib/active_support/core_ext/module/remove_method.rb b/activesupport/lib/active_support/core_ext/module/remove_method.rb
index 704f144bdd..97eb5f9eca 100644
--- a/activesupport/lib/active_support/core_ext/module/remove_method.rb
+++ b/activesupport/lib/active_support/core_ext/module/remove_method.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "redefine_method"
+require "active_support/core_ext/module/redefine_method"
 
 class Module
   # Removes the named method, if it exists.
diff --git a/activesupport/lib/active_support/core_ext/numeric.rb b/activesupport/lib/active_support/core_ext/numeric.rb
index 76e33a7cb0..0b04e359f9 100644
--- a/activesupport/lib/active_support/core_ext/numeric.rb
+++ b/activesupport/lib/active_support/core_ext/numeric.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "numeric/bytes"
-require_relative "numeric/time"
-require_relative "numeric/inquiry"
-require_relative "numeric/conversions"
+require "active_support/core_ext/numeric/bytes"
+require "active_support/core_ext/numeric/time"
+require "active_support/core_ext/numeric/inquiry"
+require "active_support/core_ext/numeric/conversions"
diff --git a/activesupport/lib/active_support/core_ext/numeric/conversions.rb b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
index 05528f5069..f6c2713986 100644
--- a/activesupport/lib/active_support/core_ext/numeric/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../big_decimal/conversions"
-require_relative "../../number_helper"
-require_relative "../module/deprecation"
+require "active_support/core_ext/big_decimal/conversions"
+require "active_support/number_helper"
+require "active_support/core_ext/module/deprecation"
 
 module ActiveSupport::NumericWithFormat
   # Provides options for converting numbers into formatted strings.
@@ -108,19 +108,19 @@ module ActiveSupport::NumericWithFormat
     when Integer, String
       super(format)
     when :phone
-      return ActiveSupport::NumberHelper.number_to_phone(self, options || {})
+      ActiveSupport::NumberHelper.number_to_phone(self, options || {})
     when :currency
-      return ActiveSupport::NumberHelper.number_to_currency(self, options || {})
+      ActiveSupport::NumberHelper.number_to_currency(self, options || {})
     when :percentage
-      return ActiveSupport::NumberHelper.number_to_percentage(self, options || {})
+      ActiveSupport::NumberHelper.number_to_percentage(self, options || {})
     when :delimited
-      return ActiveSupport::NumberHelper.number_to_delimited(self, options || {})
+      ActiveSupport::NumberHelper.number_to_delimited(self, options || {})
     when :rounded
-      return ActiveSupport::NumberHelper.number_to_rounded(self, options || {})
+      ActiveSupport::NumberHelper.number_to_rounded(self, options || {})
     when :human
-      return ActiveSupport::NumberHelper.number_to_human(self, options || {})
+      ActiveSupport::NumberHelper.number_to_human(self, options || {})
     when :human_size
-      return ActiveSupport::NumberHelper.number_to_human_size(self, options || {})
+      ActiveSupport::NumberHelper.number_to_human_size(self, options || {})
     when Symbol
       super()
     else
diff --git a/activesupport/lib/active_support/core_ext/numeric/time.rb b/activesupport/lib/active_support/core_ext/numeric/time.rb
index 0cee87cb86..bc4627f7a2 100644
--- a/activesupport/lib/active_support/core_ext/numeric/time.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/time.rb
@@ -1,25 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "../../duration"
-require_relative "../time/calculations"
-require_relative "../time/acts_like"
-require_relative "../date/calculations"
-require_relative "../date/acts_like"
+require "active_support/duration"
+require "active_support/core_ext/time/calculations"
+require "active_support/core_ext/time/acts_like"
+require "active_support/core_ext/date/calculations"
+require "active_support/core_ext/date/acts_like"
 
 class Numeric
-  # Enables the use of time calculations and declarations, like 45.minutes + 2.hours + 4.years.
+  # Returns a Duration instance matching the number of seconds provided.
   #
-  # These methods use Time#advance for precise date calculations when using from_now, ago, etc.
-  # as well as adding or subtracting their results from a Time object. For example:
-  #
-  #   # equivalent to Time.current.advance(months: 1)
-  #   1.month.from_now
-  #
-  #   # equivalent to Time.current.advance(years: 2)
-  #   2.years.from_now
-  #
-  #   # equivalent to Time.current.advance(months: 4, years: 5)
-  #   (4.months + 5.years).from_now
+  #   2.seconds # => 2 seconds
   def seconds
     ActiveSupport::Duration.seconds(self)
   end
@@ -66,10 +56,10 @@ class Numeric
   alias :fortnight :fortnights
 
   # Returns the number of milliseconds equivalent to the seconds provided.
-  # Used with the standard time durations, like 1.hour.in_milliseconds --
-  # so we can feed them to JavaScript functions like getTime().
+  # Used with the standard time durations.
   #
-  #   2.in_milliseconds # => 2_000
+  #   2.in_milliseconds # => 2000
+  #   1.hour.in_milliseconds # => 3600000
   def in_milliseconds
     self * 1000
   end
diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index 23f5eec8c7..efd34cc692 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -1,16 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "object/acts_like"
-require_relative "object/blank"
-require_relative "object/duplicable"
-require_relative "object/deep_dup"
-require_relative "object/try"
-require_relative "object/inclusion"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/object/duplicable"
+require "active_support/core_ext/object/deep_dup"
+require "active_support/core_ext/object/try"
+require "active_support/core_ext/object/inclusion"
 
-require_relative "object/conversions"
-require_relative "object/instance_variables"
+require "active_support/core_ext/object/conversions"
+require "active_support/core_ext/object/instance_variables"
 
-require_relative "object/json"
-require_relative "object/to_param"
-require_relative "object/to_query"
-require_relative "object/with_options"
+require "active_support/core_ext/object/json"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/object/with_options"
diff --git a/activesupport/lib/active_support/core_ext/object/acts_like.rb b/activesupport/lib/active_support/core_ext/object/acts_like.rb
index 2eb72f6b3a..403ee20e39 100644
--- a/activesupport/lib/active_support/core_ext/object/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/object/acts_like.rb
@@ -7,6 +7,15 @@ class Object
   # <tt>x.acts_like?(:date)</tt> to do duck-type-safe comparisons, since classes that
   # we want to act like Time simply need to define an <tt>acts_like_time?</tt> method.
   def acts_like?(duck)
-    respond_to? :"acts_like_#{duck}?"
+    case duck
+    when :time
+      respond_to? :acts_like_time?
+    when :date
+      respond_to? :acts_like_date?
+    when :string
+      respond_to? :acts_like_string?
+    else
+      respond_to? :"acts_like_#{duck}?"
+    end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/object/blank.rb b/activesupport/lib/active_support/core_ext/object/blank.rb
index 397adbdb5a..e42ad852dd 100644
--- a/activesupport/lib/active_support/core_ext/object/blank.rb
+++ b/activesupport/lib/active_support/core_ext/object/blank.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../regexp"
+require "active_support/core_ext/regexp"
 
 class Object
   # An object is blank if it's false, empty, or a whitespace string.
diff --git a/activesupport/lib/active_support/core_ext/object/conversions.rb b/activesupport/lib/active_support/core_ext/object/conversions.rb
index fdc154188a..624fb8d77c 100644
--- a/activesupport/lib/active_support/core_ext/object/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/object/conversions.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "to_param"
-require_relative "to_query"
-require_relative "../array/conversions"
-require_relative "../hash/conversions"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/array/conversions"
+require "active_support/core_ext/hash/conversions"
diff --git a/activesupport/lib/active_support/core_ext/object/deep_dup.rb b/activesupport/lib/active_support/core_ext/object/deep_dup.rb
index 4021b15de6..c66c5eb2d9 100644
--- a/activesupport/lib/active_support/core_ext/object/deep_dup.rb
+++ b/activesupport/lib/active_support/core_ext/object/deep_dup.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "duplicable"
+require "active_support/core_ext/object/duplicable"
 
 class Object
   # Returns a deep copy of object if it's duplicable. If it's
diff --git a/activesupport/lib/active_support/core_ext/object/json.rb b/activesupport/lib/active_support/core_ext/object/json.rb
index 30495313d2..f7c623fe13 100644
--- a/activesupport/lib/active_support/core_ext/object/json.rb
+++ b/activesupport/lib/active_support/core_ext/object/json.rb
@@ -5,14 +5,14 @@ require "json"
 require "bigdecimal"
 require "uri/generic"
 require "pathname"
-require_relative "../big_decimal/conversions" # for #to_s
-require_relative "../hash/except"
-require_relative "../hash/slice"
-require_relative "instance_variables"
+require "active_support/core_ext/big_decimal/conversions" # for #to_s
+require "active_support/core_ext/hash/except"
+require "active_support/core_ext/hash/slice"
+require "active_support/core_ext/object/instance_variables"
 require "time"
-require_relative "../time/conversions"
-require_relative "../date_time/conversions"
-require_relative "../date/conversions"
+require "active_support/core_ext/time/conversions"
+require "active_support/core_ext/date_time/conversions"
+require "active_support/core_ext/date/conversions"
 
 # The JSON gem adds a few modules to Ruby core classes containing :to_json definition, overwriting
 # their default behavior. That said, we need to define the basic to_json method in all of them,
@@ -135,6 +135,12 @@ module Enumerable
   end
 end
 
+class IO
+  def as_json(options = nil) #:nodoc:
+    to_s
+  end
+end
+
 class Range
   def as_json(options = nil) #:nodoc:
     to_s
diff --git a/activesupport/lib/active_support/core_ext/object/to_param.rb b/activesupport/lib/active_support/core_ext/object/to_param.rb
index c57488bcbc..6d2bdd70f3 100644
--- a/activesupport/lib/active_support/core_ext/object/to_param.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_param.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-require_relative "to_query"
+require "active_support/core_ext/object/to_query"
diff --git a/activesupport/lib/active_support/core_ext/object/with_options.rb b/activesupport/lib/active_support/core_ext/object/with_options.rb
index 47766f6012..2838fd76be 100644
--- a/activesupport/lib/active_support/core_ext/object/with_options.rb
+++ b/activesupport/lib/active_support/core_ext/object/with_options.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../option_merger"
+require "active_support/option_merger"
 
 class Object
   # An elegant way to factor duplication out of options passed to a series of
@@ -62,7 +62,7 @@ class Object
   #
   #   validates :content, length: { minimum: 50 }, if: -> { content.present? }
   #
-  # Hence the inherited default for `if` key is ignored.
+  # Hence the inherited default for +if+ key is ignored.
   #
   # NOTE: You cannot call class methods implicitly inside of with_options.
   # You can access these methods using the class name instead:
diff --git a/activesupport/lib/active_support/core_ext/range.rb b/activesupport/lib/active_support/core_ext/range.rb
index 89bbbfcb81..4074e91d17 100644
--- a/activesupport/lib/active_support/core_ext/range.rb
+++ b/activesupport/lib/active_support/core_ext/range.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "range/conversions"
-require_relative "range/include_range"
-require_relative "range/overlaps"
-require_relative "range/each"
+require "active_support/core_ext/range/conversions"
+require "active_support/core_ext/range/include_range"
+require "active_support/core_ext/range/include_time_with_zone"
+require "active_support/core_ext/range/overlaps"
+require "active_support/core_ext/range/each"
diff --git a/activesupport/lib/active_support/core_ext/range/conversions.rb b/activesupport/lib/active_support/core_ext/range/conversions.rb
index 37868f5875..8832fbcb3c 100644
--- a/activesupport/lib/active_support/core_ext/range/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/range/conversions.rb
@@ -2,7 +2,13 @@
 
 module ActiveSupport::RangeWithFormat
   RANGE_FORMATS = {
-    db: Proc.new { |start, stop| "BETWEEN '#{start.to_s(:db)}' AND '#{stop.to_s(:db)}'" }
+    db: -> (start, stop) do
+      case start
+      when String then "BETWEEN '#{start}' AND '#{stop}'"
+      else
+        "BETWEEN '#{start.to_s(:db)}' AND '#{stop.to_s(:db)}'"
+      end
+    end
   }
 
   # Convert range to a formatted string. See RANGE_FORMATS for predefined formats.
diff --git a/activesupport/lib/active_support/core_ext/range/each.rb b/activesupport/lib/active_support/core_ext/range/each.rb
index cdff6393d7..2f22cd0e92 100644
--- a/activesupport/lib/active_support/core_ext/range/each.rb
+++ b/activesupport/lib/active_support/core_ext/range/each.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/time_with_zone"
+
 module ActiveSupport
   module EachTimeWithZone #:nodoc:
     def each(&block)
@@ -15,7 +17,7 @@ module ActiveSupport
     private
 
       def ensure_iteration_allowed
-        raise TypeError, "can't iterate from #{first.class}" if first.is_a?(Time)
+        raise TypeError, "can't iterate from #{first.class}" if first.is_a?(TimeWithZone)
       end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/range/include_time_with_zone.rb b/activesupport/lib/active_support/core_ext/range/include_time_with_zone.rb
new file mode 100644
index 0000000000..5f80acf68e
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/range/include_time_with_zone.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "active_support/time_with_zone"
+
+module ActiveSupport
+  module IncludeTimeWithZone #:nodoc:
+    # Extends the default Range#include? to support ActiveSupport::TimeWithZone.
+    #
+    #   (1.hour.ago..1.hour.from_now).include?(Time.current) # => true
+    #
+    def include?(value)
+      if first.is_a?(TimeWithZone)
+        cover?(value)
+      elsif last.is_a?(TimeWithZone)
+        cover?(value)
+      else
+        super
+      end
+    end
+  end
+end
+
+Range.prepend(ActiveSupport::IncludeTimeWithZone)
diff --git a/activesupport/lib/active_support/core_ext/string.rb b/activesupport/lib/active_support/core_ext/string.rb
index 491eec2fc9..757d15c51a 100644
--- a/activesupport/lib/active_support/core_ext/string.rb
+++ b/activesupport/lib/active_support/core_ext/string.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "string/conversions"
-require_relative "string/filters"
-require_relative "string/multibyte"
-require_relative "string/starts_ends_with"
-require_relative "string/inflections"
-require_relative "string/access"
-require_relative "string/behavior"
-require_relative "string/output_safety"
-require_relative "string/exclude"
-require_relative "string/strip"
-require_relative "string/inquiry"
-require_relative "string/indent"
-require_relative "string/zones"
+require "active_support/core_ext/string/conversions"
+require "active_support/core_ext/string/filters"
+require "active_support/core_ext/string/multibyte"
+require "active_support/core_ext/string/starts_ends_with"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/string/access"
+require "active_support/core_ext/string/behavior"
+require "active_support/core_ext/string/output_safety"
+require "active_support/core_ext/string/exclude"
+require "active_support/core_ext/string/strip"
+require "active_support/core_ext/string/inquiry"
+require "active_support/core_ext/string/indent"
+require "active_support/core_ext/string/zones"
diff --git a/activesupport/lib/active_support/core_ext/string/conversions.rb b/activesupport/lib/active_support/core_ext/string/conversions.rb
index f8f6524b2b..29a88b07ad 100644
--- a/activesupport/lib/active_support/core_ext/string/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/string/conversions.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../time/calculations"
+require "active_support/core_ext/time/calculations"
 
 class String
   # Converts a string to a Time value.
diff --git a/activesupport/lib/active_support/core_ext/string/inflections.rb b/activesupport/lib/active_support/core_ext/string/inflections.rb
index b5bb385033..8af301734a 100644
--- a/activesupport/lib/active_support/core_ext/string/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/string/inflections.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector/methods"
-require_relative "../../inflector/transliterate"
+require "active_support/inflector/methods"
+require "active_support/inflector/transliterate"
 
 # String inflections define new methods on the String class to transform names for different purposes.
 # For instance, you can figure out the name of a table from the name of a class.
@@ -174,7 +174,7 @@ class String
   #   <%= link_to(@person.name, person_path) %>
   #   # => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
   #
-  # To preserve the case of the characters in a string, use the `preserve_case` argument.
+  # To preserve the case of the characters in a string, use the +preserve_case+ argument.
   #
   #   class Person
   #     def to_param
diff --git a/activesupport/lib/active_support/core_ext/string/inquiry.rb b/activesupport/lib/active_support/core_ext/string/inquiry.rb
index 92069981b6..a796d5fb4f 100644
--- a/activesupport/lib/active_support/core_ext/string/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/string/inquiry.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../string_inquirer"
+require "active_support/string_inquirer"
 
 class String
   # Wraps the current string in the <tt>ActiveSupport::StringInquirer</tt> class,
diff --git a/activesupport/lib/active_support/core_ext/string/multibyte.rb b/activesupport/lib/active_support/core_ext/string/multibyte.rb
index fba5b166a2..07c0d16398 100644
--- a/activesupport/lib/active_support/core_ext/string/multibyte.rb
+++ b/activesupport/lib/active_support/core_ext/string/multibyte.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../multibyte"
+require "active_support/multibyte"
 
 class String
   # == Multibyte proxy
@@ -16,6 +16,8 @@ class String
   #   >> "lj".mb_chars.upcase.to_s
   #   => "LJ"
   #
+  # NOTE: An above example is useful for pre Ruby 2.4. Ruby 2.4 supports Unicode case mappings.
+  #
   # == Method chaining
   #
   # All the methods on the Chars proxy which normally return a string will return a Chars object. This allows
diff --git a/activesupport/lib/active_support/core_ext/string/output_safety.rb b/activesupport/lib/active_support/core_ext/string/output_safety.rb
index 600b41da10..f3bdc2977e 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 require "erb"
-require_relative "../kernel/singleton_class"
-require_relative "../module/redefine_method"
-require_relative "../../multibyte/unicode"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/multibyte/unicode"
 
 class ERB
   module Util
@@ -15,9 +15,6 @@ class ERB
     # A utility method for escaping HTML tag characters.
     # This method is also aliased as <tt>h</tt>.
     #
-    # In your ERB templates, use this method to escape any unsafe content. For example:
-    #   <%= h @person.name %>
-    #
     #   puts html_escape('is a > 0 & a < 10?')
     #   # => is a &gt; 0 &amp; a &lt; 10?
     def html_escape(s)
@@ -253,7 +250,7 @@ class String
   # Marks a string as trusted safe. It will be inserted into HTML with no
   # additional escaping performed. It is your responsibility to ensure that the
   # string contains no malicious content. This method is equivalent to the
-  # `raw` helper in views. It is recommended that you use `sanitize` instead of
+  # +raw+ helper in views. It is recommended that you use +sanitize+ instead of
   # this method. It should never be called on user input.
   def html_safe
     ActiveSupport::SafeBuffer.new(self)
diff --git a/activesupport/lib/active_support/core_ext/string/zones.rb b/activesupport/lib/active_support/core_ext/string/zones.rb
index db30c03a8e..55dc231464 100644
--- a/activesupport/lib/active_support/core_ext/string/zones.rb
+++ b/activesupport/lib/active_support/core_ext/string/zones.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "conversions"
-require_relative "../time/zones"
+require "active_support/core_ext/string/conversions"
+require "active_support/core_ext/time/zones"
 
 class String
   # Converts String to a TimeWithZone in the current zone if Time.zone or Time.zone_default
diff --git a/activesupport/lib/active_support/core_ext/time.rb b/activesupport/lib/active_support/core_ext/time.rb
index 4e16274443..c809def05f 100644
--- a/activesupport/lib/active_support/core_ext/time.rb
+++ b/activesupport/lib/active_support/core_ext/time.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "time/acts_like"
-require_relative "time/calculations"
-require_relative "time/compatibility"
-require_relative "time/conversions"
-require_relative "time/zones"
+require "active_support/core_ext/time/acts_like"
+require "active_support/core_ext/time/calculations"
+require "active_support/core_ext/time/compatibility"
+require "active_support/core_ext/time/conversions"
+require "active_support/core_ext/time/zones"
diff --git a/activesupport/lib/active_support/core_ext/time/acts_like.rb b/activesupport/lib/active_support/core_ext/time/acts_like.rb
index 309418df42..8572b49639 100644
--- a/activesupport/lib/active_support/core_ext/time/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/time/acts_like.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../object/acts_like"
+require "active_support/core_ext/object/acts_like"
 
 class Time
   # Duck-types as a Time-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 0e51df44ef..120768dec5 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "../../duration"
-require_relative "conversions"
-require_relative "../../time_with_zone"
-require_relative "zones"
-require_relative "../date_and_time/calculations"
-require_relative "../date/calculations"
+require "active_support/duration"
+require "active_support/core_ext/time/conversions"
+require "active_support/time_with_zone"
+require "active_support/core_ext/time/zones"
+require "active_support/core_ext/date_and_time/calculations"
+require "active_support/core_ext/date/calculations"
 
 class Time
   include DateAndTime::Calculations
diff --git a/activesupport/lib/active_support/core_ext/time/compatibility.rb b/activesupport/lib/active_support/core_ext/time/compatibility.rb
index 147ae0f802..495e4f307b 100644
--- a/activesupport/lib/active_support/core_ext/time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/time/compatibility.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../date_and_time/compatibility"
-require_relative "../module/redefine_method"
+require "active_support/core_ext/date_and_time/compatibility"
+require "active_support/core_ext/module/redefine_method"
 
 class Time
   include DateAndTime::Compatibility
diff --git a/activesupport/lib/active_support/core_ext/time/conversions.rb b/activesupport/lib/active_support/core_ext/time/conversions.rb
index e3fc930ef6..345cb2832c 100644
--- a/activesupport/lib/active_support/core_ext/time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/time/conversions.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector/methods"
-require_relative "../../values/time_zone"
+require "active_support/inflector/methods"
+require "active_support/values/time_zone"
 
 class Time
   DATE_FORMATS = {
diff --git a/activesupport/lib/active_support/core_ext/time/zones.rb b/activesupport/lib/active_support/core_ext/time/zones.rb
index c48edb135f..a5588fd488 100644
--- a/activesupport/lib/active_support/core_ext/time/zones.rb
+++ b/activesupport/lib/active_support/core_ext/time/zones.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../time_with_zone"
-require_relative "acts_like"
-require_relative "../date_and_time/zones"
+require "active_support/time_with_zone"
+require "active_support/core_ext/time/acts_like"
+require "active_support/core_ext/date_and_time/zones"
 
 class Time
   include DateAndTime::Zones
@@ -55,10 +55,10 @@ class Time
     #     end
     #   end
     #
-    #  NOTE: This won't affect any <tt>ActiveSupport::TimeWithZone</tt>
-    #  objects that have already been created, e.g. any model timestamp
-    #  attributes that have been read before the block will remain in
-    #  the application's default timezone.
+    # NOTE: This won't affect any <tt>ActiveSupport::TimeWithZone</tt>
+    # objects that have already been created, e.g. any model timestamp
+    # attributes that have been read before the block will remain in
+    # the application's default timezone.
     def use_zone(time_zone)
       new_zone = find_zone!(time_zone)
       begin
diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index ad2f21205f..82c10b3079 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -4,17 +4,17 @@ require "set"
 require "thread"
 require "concurrent/map"
 require "pathname"
-require_relative "core_ext/module/aliasing"
-require_relative "core_ext/module/attribute_accessors"
-require_relative "core_ext/module/introspection"
-require_relative "core_ext/module/anonymous"
-require_relative "core_ext/object/blank"
-require_relative "core_ext/kernel/reporting"
-require_relative "core_ext/load_error"
-require_relative "core_ext/name_error"
-require_relative "core_ext/string/starts_ends_with"
-require_relative "dependencies/interlock"
-require_relative "inflector"
+require "active_support/core_ext/module/aliasing"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/introspection"
+require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/load_error"
+require "active_support/core_ext/name_error"
+require "active_support/core_ext/string/starts_ends_with"
+require "active_support/dependencies/interlock"
+require "active_support/inflector"
 
 module ActiveSupport #:nodoc:
   module Dependencies #:nodoc:
@@ -615,7 +615,7 @@ module ActiveSupport #:nodoc:
       return false if desc.is_a?(Module) && desc.anonymous?
       name = to_constant_name desc
       return false unless qualified_const_defined?(name)
-      return autoloaded_constants.include?(name)
+      autoloaded_constants.include?(name)
     end
 
     # Will the provided constant descriptor be unloaded?
diff --git a/activesupport/lib/active_support/dependencies/autoload.rb b/activesupport/lib/active_support/dependencies/autoload.rb
index 1c3775f5eb..1cee85d98f 100644
--- a/activesupport/lib/active_support/dependencies/autoload.rb
+++ b/activesupport/lib/active_support/dependencies/autoload.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../inflector/methods"
+require "active_support/inflector/methods"
 
 module ActiveSupport
   # Autoload and eager load conveniences for your library.
diff --git a/activesupport/lib/active_support/dependencies/interlock.rb b/activesupport/lib/active_support/dependencies/interlock.rb
index 4e9595ed42..948be75638 100644
--- a/activesupport/lib/active_support/dependencies/interlock.rb
+++ b/activesupport/lib/active_support/dependencies/interlock.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../concurrency/share_lock"
+require "active_support/concurrency/share_lock"
 
 module ActiveSupport #:nodoc:
   module Dependencies #:nodoc:
diff --git a/activesupport/lib/active_support/deprecation.rb b/activesupport/lib/active_support/deprecation.rb
index e6550fdcd0..a1ad2ca465 100644
--- a/activesupport/lib/active_support/deprecation.rb
+++ b/activesupport/lib/active_support/deprecation.rb
@@ -14,13 +14,13 @@ module ActiveSupport
     # a circular require warning for active_support/deprecation.rb.
     #
     # So, we define the constant first, and load dependencies later.
-    require_relative "deprecation/instance_delegator"
-    require_relative "deprecation/behaviors"
-    require_relative "deprecation/reporting"
-    require_relative "deprecation/constant_accessor"
-    require_relative "deprecation/method_wrappers"
-    require_relative "deprecation/proxy_wrappers"
-    require_relative "core_ext/module/deprecation"
+    require "active_support/deprecation/instance_delegator"
+    require "active_support/deprecation/behaviors"
+    require "active_support/deprecation/reporting"
+    require "active_support/deprecation/constant_accessor"
+    require "active_support/deprecation/method_wrappers"
+    require "active_support/deprecation/proxy_wrappers"
+    require "active_support/core_ext/module/deprecation"
 
     include Singleton
     include InstanceDelegator
diff --git a/activesupport/lib/active_support/deprecation/behaviors.rb b/activesupport/lib/active_support/deprecation/behaviors.rb
index 967320bcb9..581db5f449 100644
--- a/activesupport/lib/active_support/deprecation/behaviors.rb
+++ b/activesupport/lib/active_support/deprecation/behaviors.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../notifications"
+require "active_support/notifications"
 
 module ActiveSupport
   # Raised when <tt>ActiveSupport::Deprecation::Behavior#behavior</tt> is set with <tt>:raise</tt>.
@@ -27,7 +27,7 @@ module ActiveSupport
             if defined?(Rails.logger) && Rails.logger
               Rails.logger
             else
-              require_relative "../logger"
+              require "active_support/logger"
               ActiveSupport::Logger.new($stderr)
             end
         logger.warn message
diff --git a/activesupport/lib/active_support/deprecation/constant_accessor.rb b/activesupport/lib/active_support/deprecation/constant_accessor.rb
index 0dfd96d134..1ed0015812 100644
--- a/activesupport/lib/active_support/deprecation/constant_accessor.rb
+++ b/activesupport/lib/active_support/deprecation/constant_accessor.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../inflector/methods"
-
 module ActiveSupport
   class Deprecation
     # DeprecatedConstantAccessor transforms a constant into a deprecated one by
@@ -17,7 +15,7 @@ module ActiveSupport
     #
     #   PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto)
     #
-    #   (In a later update, the original implementation of `PLANETS` has been removed.)
+    #   # (In a later update, the original implementation of `PLANETS` has been removed.)
     #
     #   PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune)
     #   include ActiveSupport::Deprecation::DeprecatedConstantAccessor
@@ -29,6 +27,8 @@ module ActiveSupport
     #        ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"]
     module DeprecatedConstantAccessor
       def self.included(base)
+        require "active_support/inflector/methods"
+
         extension = Module.new do
           def const_missing(missing_const_name)
             if class_variable_defined?(:@@_deprecated_constants)
diff --git a/activesupport/lib/active_support/deprecation/instance_delegator.rb b/activesupport/lib/active_support/deprecation/instance_delegator.rb
index 539357c83e..8beda373a2 100644
--- a/activesupport/lib/active_support/deprecation/instance_delegator.rb
+++ b/activesupport/lib/active_support/deprecation/instance_delegator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/kernel/singleton_class"
-require_relative "../core_ext/module/delegation"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   class Deprecation
diff --git a/activesupport/lib/active_support/deprecation/method_wrappers.rb b/activesupport/lib/active_support/deprecation/method_wrappers.rb
index 8c942ed9a5..c4b78102eb 100644
--- a/activesupport/lib/active_support/deprecation/method_wrappers.rb
+++ b/activesupport/lib/active_support/deprecation/method_wrappers.rb
@@ -1,16 +1,14 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/module/aliasing"
-require_relative "../core_ext/array/extract_options"
+require "active_support/core_ext/module/aliasing"
+require "active_support/core_ext/array/extract_options"
 
 module ActiveSupport
   class Deprecation
     module MethodWrapper
       # Declare that a method has been deprecated.
       #
-      #   module Fred
-      #     extend self
-      #
+      #   class Fred
       #     def aaa; end
       #     def bbb; end
       #     def ccc; end
@@ -22,15 +20,15 @@ module ActiveSupport
       #   ActiveSupport::Deprecation.deprecate_methods(Fred, :aaa, bbb: :zzz, ccc: 'use Bar#ccc instead')
       #   # => Fred
       #
-      #   Fred.aaa
+      #   Fred.new.aaa
       #   # DEPRECATION WARNING: aaa is deprecated and will be removed from Rails 5.1. (called from irb_binding at (irb):10)
       #   # => nil
       #
-      #   Fred.bbb
+      #   Fred.new.bbb
       #   # DEPRECATION WARNING: bbb is deprecated and will be removed from Rails 5.1 (use zzz instead). (called from irb_binding at (irb):11)
       #   # => nil
       #
-      #   Fred.ccc
+      #   Fred.new.ccc
       #   # DEPRECATION WARNING: ccc is deprecated and will be removed from Rails 5.1 (use Bar#ccc instead). (called from irb_binding at (irb):12)
       #   # => nil
       #
@@ -39,7 +37,7 @@ module ActiveSupport
       #   ActiveSupport::Deprecation.deprecate_methods(Fred, ddd: :zzz, deprecator: custom_deprecator)
       #   # => [:ddd]
       #
-      #   Fred.ddd
+      #   Fred.new.ddd
       #   DEPRECATION WARNING: ddd is deprecated and will be removed from MyGem next-release (use zzz instead). (called from irb_binding at (irb):15)
       #   # => nil
       #
@@ -48,7 +46,7 @@ module ActiveSupport
       #   custom_deprecator.deprecate_methods(Fred, eee: :zzz)
       #   # => [:eee]
       #
-      #   Fred.eee
+      #   Fred.new.eee
       #   DEPRECATION WARNING: eee is deprecated and will be removed from MyGem next-release (use zzz instead). (called from irb_binding at (irb):18)
       #   # => nil
       def deprecate_methods(target_module, *method_names)
diff --git a/activesupport/lib/active_support/deprecation/proxy_wrappers.rb b/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
index 1920d75faf..896c0d2d8e 100644
--- a/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
+++ b/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../inflector/methods"
-require_relative "../core_ext/regexp"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   class Deprecation
@@ -114,7 +113,7 @@ module ActiveSupport
     #
     #   PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto)
     #
-    #   (In a later update, the original implementation of `PLANETS` has been removed.)
+    #   # (In a later update, the original implementation of `PLANETS` has been removed.)
     #
     #   PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune)
     #   PLANETS = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('PLANETS', 'PLANETS_POST_2006')
@@ -125,6 +124,8 @@ module ActiveSupport
     #        ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"]
     class DeprecatedConstantProxy < DeprecationProxy
       def initialize(old_const, new_const, deprecator = ActiveSupport::Deprecation.instance, message: "#{old_const} is deprecated! Use #{new_const} instead.")
+        require "active_support/inflector/methods"
+
         @old_const = old_const
         @new_const = new_const
         @deprecator = deprecator
diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
index 34024fa8c6..1af3411a8a 100644
--- a/activesupport/lib/active_support/duration.rb
+++ b/activesupport/lib/active_support/duration.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/array/conversions"
-require_relative "core_ext/module/delegation"
-require_relative "core_ext/object/acts_like"
-require_relative "core_ext/string/filters"
-require_relative "deprecation"
+require "active_support/core_ext/array/conversions"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/string/filters"
+require "active_support/deprecation"
 
 module ActiveSupport
   # Provides accurate date and time measurements using Date#advance and
diff --git a/activesupport/lib/active_support/duration/iso8601_parser.rb b/activesupport/lib/active_support/duration/iso8601_parser.rb
index a002424cd9..1847eeaa86 100644
--- a/activesupport/lib/active_support/duration/iso8601_parser.rb
+++ b/activesupport/lib/active_support/duration/iso8601_parser.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "strscan"
-require_relative "../core_ext/regexp"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   class Duration
@@ -118,7 +118,7 @@ module ActiveSupport
             raise_parsing_error "(only last part can be fractional)"
           end
 
-          return true
+          true
         end
     end
   end
diff --git a/activesupport/lib/active_support/duration/iso8601_serializer.rb b/activesupport/lib/active_support/duration/iso8601_serializer.rb
index 985eac113f..bb177ae5b7 100644
--- a/activesupport/lib/active_support/duration/iso8601_serializer.rb
+++ b/activesupport/lib/active_support/duration/iso8601_serializer.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/object/blank"
-require_relative "../core_ext/hash/transform_values"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/hash/transform_values"
 
 module ActiveSupport
   class Duration
diff --git a/activesupport/lib/active_support/encrypted_configuration.rb b/activesupport/lib/active_support/encrypted_configuration.rb
index b403048627..c52d3869de 100644
--- a/activesupport/lib/active_support/encrypted_configuration.rb
+++ b/activesupport/lib/active_support/encrypted_configuration.rb
@@ -22,6 +22,12 @@ module ActiveSupport
       ""
     end
 
+    def write(contents)
+      deserialize(contents)
+
+      super
+    end
+
     def config
       @config ||= deserialize(read).deep_symbolize_keys
     end
@@ -36,7 +42,7 @@ module ActiveSupport
       end
 
       def deserialize(config)
-        config.present? ? YAML.load(config) : {}
+        config.present? ? YAML.load(config, content_path) : {}
       end
   end
 end
diff --git a/activesupport/lib/active_support/encrypted_file.rb b/activesupport/lib/active_support/encrypted_file.rb
index 1c4c1cb457..3d1455fb95 100644
--- a/activesupport/lib/active_support/encrypted_file.rb
+++ b/activesupport/lib/active_support/encrypted_file.rb
@@ -2,8 +2,6 @@
 
 require "pathname"
 require "active_support/message_encryptor"
-require "active_support/core_ext/string/strip"
-require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   class EncryptedFile
diff --git a/activesupport/lib/active_support/execution_wrapper.rb b/activesupport/lib/active_support/execution_wrapper.rb
index fd87d84795..f48c586cad 100644
--- a/activesupport/lib/active_support/execution_wrapper.rb
+++ b/activesupport/lib/active_support/execution_wrapper.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "callbacks"
+require "active_support/callbacks"
 
 module ActiveSupport
   class ExecutionWrapper
diff --git a/activesupport/lib/active_support/executor.rb b/activesupport/lib/active_support/executor.rb
index e6487ba69d..ce391b07ec 100644
--- a/activesupport/lib/active_support/executor.rb
+++ b/activesupport/lib/active_support/executor.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "execution_wrapper"
+require "active_support/execution_wrapper"
 
 module ActiveSupport
   class Executor < ExecutionWrapper
diff --git a/activesupport/lib/active_support/file_update_checker.rb b/activesupport/lib/active_support/file_update_checker.rb
index bcf7b9de64..1a0bb10815 100644
--- a/activesupport/lib/active_support/file_update_checker.rb
+++ b/activesupport/lib/active_support/file_update_checker.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/time/calculations"
+require "active_support/core_ext/time/calculations"
 
 module ActiveSupport
   # FileUpdateChecker specifies the API used by Rails to watch files
diff --git a/activesupport/lib/active_support/gem_version.rb b/activesupport/lib/active_support/gem_version.rb
index 2a7ef2f820..1e09adbb52 100644
--- a/activesupport/lib/active_support/gem_version.rb
+++ b/activesupport/lib/active_support/gem_version.rb
@@ -10,7 +10,7 @@ module ActiveSupport
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 12291af443..2e2ed8a25d 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/hash/keys"
-require_relative "core_ext/hash/reverse_merge"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/hash/reverse_merge"
 
 module ActiveSupport
   # Implements a hash where keys <tt>:foo</tt> and <tt>"foo"</tt> are considered
@@ -306,6 +306,21 @@ module ActiveSupport
       dup.tap { |hash| hash.transform_values!(*args, &block) }
     end
 
+    def transform_keys(*args, &block)
+      return to_enum(:transform_keys) unless block_given?
+      dup.tap { |hash| hash.transform_keys!(*args, &block) }
+    end
+
+    def slice(*keys)
+      keys.map! { |key| convert_key(key) }
+      self.class.new(super)
+    end
+
+    def slice!(*keys)
+      keys.map! { |key| convert_key(key) }
+      super
+    end
+
     def compact
       dup.tap(&:compact!)
     end
diff --git a/activesupport/lib/active_support/i18n.rb b/activesupport/lib/active_support/i18n.rb
index 80f1475630..d60b3eff30 100644
--- a/activesupport/lib/active_support/i18n.rb
+++ b/activesupport/lib/active_support/i18n.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/hash/deep_merge"
-require_relative "core_ext/hash/except"
-require_relative "core_ext/hash/slice"
+require "active_support/core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/except"
+require "active_support/core_ext/hash/slice"
 begin
   require "i18n"
 rescue LoadError => e
   $stderr.puts "The i18n gem is not available. Please add it to your Gemfile and run bundle install"
   raise e
 end
-require_relative "lazy_load_hooks"
+require "active_support/lazy_load_hooks"
 
 ActiveSupport.run_load_hooks(:i18n)
 I18n.load_path << File.expand_path("locale/en.yml", __dir__)
diff --git a/activesupport/lib/active_support/i18n_railtie.rb b/activesupport/lib/active_support/i18n_railtie.rb
index 369aecff69..ce8bfbfd8c 100644
--- a/activesupport/lib/active_support/i18n_railtie.rb
+++ b/activesupport/lib/active_support/i18n_railtie.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "file_update_checker"
-require_relative "core_ext/array/wrap"
+require "active_support/file_update_checker"
+require "active_support/core_ext/array/wrap"
 
 # :enddoc:
 
diff --git a/activesupport/lib/active_support/inflections.rb b/activesupport/lib/active_support/inflections.rb
index e8e1657111..baf1cb3038 100644
--- a/activesupport/lib/active_support/inflections.rb
+++ b/activesupport/lib/active_support/inflections.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "inflector/inflections"
+require "active_support/inflector/inflections"
 
 #--
 # Defines the standard inflection rules. These are the starting point for
diff --git a/activesupport/lib/active_support/inflector.rb b/activesupport/lib/active_support/inflector.rb
index a6adb15a18..d77f04c9c5 100644
--- a/activesupport/lib/active_support/inflector.rb
+++ b/activesupport/lib/active_support/inflector.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 # in case active_support/inflector is required without the rest of active_support
-require_relative "inflector/inflections"
-require_relative "inflector/transliterate"
-require_relative "inflector/methods"
+require "active_support/inflector/inflections"
+require "active_support/inflector/transliterate"
+require "active_support/inflector/methods"
 
-require_relative "inflections"
-require_relative "core_ext/string/inflections"
+require "active_support/inflections"
+require "active_support/core_ext/string/inflections"
diff --git a/activesupport/lib/active_support/inflector/inflections.rb b/activesupport/lib/active_support/inflector/inflections.rb
index 36dfbc5f42..0450a4be4c 100644
--- a/activesupport/lib/active_support/inflector/inflections.rb
+++ b/activesupport/lib/active_support/inflector/inflections.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "../core_ext/array/prepend_and_append"
-require_relative "../core_ext/regexp"
-require_relative "../i18n"
+require "active_support/core_ext/array/prepend_and_append"
+require "active_support/core_ext/regexp"
+require "active_support/i18n"
+require "active_support/deprecation"
 
 module ActiveSupport
   module Inflector
@@ -67,16 +68,21 @@ module ActiveSupport
       end
 
       attr_reader :plurals, :singulars, :uncountables, :humans, :acronyms, :acronym_regex
+      deprecate :acronym_regex
+
+      attr_reader :acronyms_camelize_regex, :acronyms_underscore_regex # :nodoc:
 
       def initialize
-        @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], Uncountables.new, [], {}, /(?=a)b/
+        @plurals, @singulars, @uncountables, @humans, @acronyms = [], [], Uncountables.new, [], {}
+        define_acronym_regex_patterns
       end
 
       # Private, for the test suite.
       def initialize_dup(orig) # :nodoc:
-        %w(plurals singulars uncountables humans acronyms acronym_regex).each do |scope|
+        %w(plurals singulars uncountables humans acronyms).each do |scope|
           instance_variable_set("@#{scope}", orig.send(scope).dup)
         end
+        define_acronym_regex_patterns
       end
 
       # Specifies a new acronym. An acronym must be specified as it will appear
@@ -130,7 +136,7 @@ module ActiveSupport
       #   camelize 'mcdonald'   # => 'McDonald'
       def acronym(word)
         @acronyms[word.downcase] = word
-        @acronym_regex = /#{@acronyms.values.join("|")}/
+        define_acronym_regex_patterns
       end
 
       # Specifies a new pluralization rule and its replacement. The rule can
@@ -225,6 +231,14 @@ module ActiveSupport
           instance_variable_set "@#{scope}", []
         end
       end
+
+      private
+
+        def define_acronym_regex_patterns
+          @acronym_regex             = @acronyms.empty? ? /(?=a)b/ : /#{@acronyms.values.join("|")}/
+          @acronyms_camelize_regex   = /^(?:#{@acronym_regex}(?=\b|[A-Z_])|\w)/
+          @acronyms_underscore_regex = /(?:(?<=([A-Za-z\d]))|\b)(#{@acronym_regex})(?=\b|[^a-z])/
+        end
     end
 
     # Yields a singleton instance of Inflector::Inflections so you can specify
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 9398ed60a4..60eeaa77cb 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../inflections"
-require_relative "../core_ext/regexp"
+require "active_support/inflections"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   # The Inflector transforms words from singular to plural, class names to table
@@ -71,7 +71,7 @@ module ActiveSupport
       if uppercase_first_letter
         string = string.sub(/^[a-z\d]*/) { |match| inflections.acronyms[match] || match.capitalize }
       else
-        string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { |match| match.downcase }
+        string = string.sub(inflections.acronyms_camelize_regex) { |match| match.downcase }
       end
       string.gsub!(/(?:_|(\/))([a-z\d]*)/i) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" }
       string.gsub!("/".freeze, "::".freeze)
@@ -92,7 +92,7 @@ module ActiveSupport
     def underscore(camel_cased_word)
       return camel_cased_word unless /[A-Z-]|::/.match?(camel_cased_word)
       word = camel_cased_word.to_s.gsub("::".freeze, "/".freeze)
-      word.gsub!(/(?:(?<=([A-Za-z\d]))|\b)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1 && '_'.freeze }#{$2.downcase}" }
+      word.gsub!(inflections.acronyms_underscore_regex) { "#{$1 && '_'.freeze }#{$2.downcase}" }
       word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
       word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
       word.tr!("-".freeze, "_".freeze)
@@ -138,7 +138,7 @@ module ActiveSupport
       result.tr!("_".freeze, " ".freeze)
 
       result.gsub!(/([a-z\d]*)/i) do |match|
-        "#{inflections.acronyms[match] || match.downcase}"
+        "#{inflections.acronyms[match.downcase] || match.downcase}"
       end
 
       if capitalize
diff --git a/activesupport/lib/active_support/inflector/transliterate.rb b/activesupport/lib/active_support/inflector/transliterate.rb
index aa7b21734e..6f2ca4999c 100644
--- a/activesupport/lib/active_support/inflector/transliterate.rb
+++ b/activesupport/lib/active_support/inflector/transliterate.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/string/multibyte"
-require_relative "../i18n"
+require "active_support/core_ext/string/multibyte"
+require "active_support/i18n"
 
 module ActiveSupport
   module Inflector
@@ -71,17 +71,23 @@ module ActiveSupport
     # a 'pretty' URL.
     #
     #   parameterize("Donald E. Knuth") # => "donald-e-knuth"
-    #   parameterize("^trés|Jolie-- ")  # => "tres-jolie"
+    #   parameterize("^très|Jolie-- ")  # => "tres-jolie"
     #
-    # To use a custom separator, override the `separator` argument.
+    # To use a custom separator, override the +separator+ argument.
     #
     #  parameterize("Donald E. Knuth", separator: '_') # => "donald_e_knuth"
-    #  parameterize("^trés|Jolie-- ", separator: '_')  # => "tres_jolie"
+    #  parameterize("^très|Jolie__ ", separator: '_')  # => "tres_jolie"
     #
-    # To preserve the case of the characters in a string, use the `preserve_case` argument.
+    # To preserve the case of the characters in a string, use the +preserve_case+ argument.
     #
     #   parameterize("Donald E. Knuth", preserve_case: true) # => "Donald-E-Knuth"
-    #   parameterize("^trés|Jolie-- ", preserve_case: true) # => "tres-Jolie"
+    #   parameterize("^très|Jolie-- ", preserve_case: true) # => "tres-Jolie"
+    #
+    # It preserves dashes and underscores unless they are used as separators:
+    #
+    #  parameterize("^très|Jolie__ ")                 # => "tres-jolie__"
+    #  parameterize("^très|Jolie-- ", separator: "_") # => "tres_jolie--"
+    #  parameterize("^très_Jolie-- ", separator: ".") # => "tres_jolie--"
     #
     def parameterize(string, separator: "-", preserve_case: false)
       # Replace accented chars with their ASCII equivalents.
diff --git a/activesupport/lib/active_support/json.rb b/activesupport/lib/active_support/json.rb
index b5672025fb..d7887175c0 100644
--- a/activesupport/lib/active_support/json.rb
+++ b/activesupport/lib/active_support/json.rb
@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 
-require_relative "json/decoding"
-require_relative "json/encoding"
+require "active_support/json/decoding"
+require "active_support/json/encoding"
diff --git a/activesupport/lib/active_support/json/decoding.rb b/activesupport/lib/active_support/json/decoding.rb
index caa4082dde..8c0e016dc5 100644
--- a/activesupport/lib/active_support/json/decoding.rb
+++ b/activesupport/lib/active_support/json/decoding.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/module/attribute_accessors"
-require_relative "../core_ext/module/delegation"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/delegation"
 require "json"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/json/encoding.rb b/activesupport/lib/active_support/json/encoding.rb
index 4016d13364..1339c75ffe 100644
--- a/activesupport/lib/active_support/json/encoding.rb
+++ b/activesupport/lib/active_support/json/encoding.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/object/json"
-require_relative "../core_ext/module/delegation"
+require "active_support/core_ext/object/json"
+require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   class << self
diff --git a/activesupport/lib/active_support/log_subscriber.rb b/activesupport/lib/active_support/log_subscriber.rb
index 05a11221bf..0f7be06c8e 100644
--- a/activesupport/lib/active_support/log_subscriber.rb
+++ b/activesupport/lib/active_support/log_subscriber.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/module/attribute_accessors"
-require_relative "core_ext/class/attribute"
-require_relative "subscriber"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/class/attribute"
+require "active_support/subscriber"
 
 module ActiveSupport
   # ActiveSupport::LogSubscriber is an object set to consume
diff --git a/activesupport/lib/active_support/log_subscriber/test_helper.rb b/activesupport/lib/active_support/log_subscriber/test_helper.rb
index 5b2abfc57c..3f19ef5009 100644
--- a/activesupport/lib/active_support/log_subscriber/test_helper.rb
+++ b/activesupport/lib/active_support/log_subscriber/test_helper.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../log_subscriber"
-require_relative "../logger"
-require_relative "../notifications"
+require "active_support/log_subscriber"
+require "active_support/logger"
+require "active_support/notifications"
 
 module ActiveSupport
   class LogSubscriber
diff --git a/activesupport/lib/active_support/logger.rb b/activesupport/lib/active_support/logger.rb
index 3397ac4c9f..8152a182b4 100644
--- a/activesupport/lib/active_support/logger.rb
+++ b/activesupport/lib/active_support/logger.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "logger_silence"
-require_relative "logger_thread_safe_level"
+require "active_support/logger_silence"
+require "active_support/logger_thread_safe_level"
 require "logger"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/logger_silence.rb b/activesupport/lib/active_support/logger_silence.rb
index 693c7a1947..89f32b6782 100644
--- a/activesupport/lib/active_support/logger_silence.rb
+++ b/activesupport/lib/active_support/logger_silence.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "core_ext/module/attribute_accessors"
+require "active_support/concern"
+require "active_support/core_ext/module/attribute_accessors"
 require "concurrent"
 
 module LoggerSilence
diff --git a/activesupport/lib/active_support/logger_thread_safe_level.rb b/activesupport/lib/active_support/logger_thread_safe_level.rb
index 3c7f53d92c..ba32813d3d 100644
--- a/activesupport/lib/active_support/logger_thread_safe_level.rb
+++ b/activesupport/lib/active_support/logger_thread_safe_level.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "concern"
+require "active_support/concern"
 
 module ActiveSupport
   module LoggerThreadSafeLevel # :nodoc:
diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb
index 27620f56be..27fd061947 100644
--- a/activesupport/lib/active_support/message_encryptor.rb
+++ b/activesupport/lib/active_support/message_encryptor.rb
@@ -2,9 +2,9 @@
 
 require "openssl"
 require "base64"
-require_relative "core_ext/array/extract_options"
-require_relative "message_verifier"
-require_relative "messages/metadata"
+require "active_support/core_ext/array/extract_options"
+require "active_support/message_verifier"
+require "active_support/messages/metadata"
 
 module ActiveSupport
   # MessageEncryptor is a simple way to encrypt values which get stored
@@ -54,7 +54,33 @@ module ActiveSupport
   #
   # Then the messages can be verified and returned upto the expire time.
   # Thereafter, verifying returns +nil+.
+  #
+  # === Rotating keys
+  #
+  # MessageEncryptor also supports rotating out old configurations by falling
+  # back to a stack of encryptors. Call +rotate+ to build and add an encryptor
+  # so +decrypt_and_verify+ will also try the fallback.
+  #
+  # By default any rotated encryptors use the values of the primary
+  # encryptor unless specified otherwise.
+  #
+  # You'd give your encryptor the new defaults:
+  #
+  #   crypt = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+  #
+  # Then gradually rotate the old values out by adding them as fallbacks. Any message
+  # generated with the old values will then work until the rotation is removed.
+  #
+  #   crypt.rotate old_secret            # Fallback to an old secret instead of @secret.
+  #   crypt.rotate cipher: "aes-256-cbc" # Fallback to an old cipher instead of aes-256-gcm.
+  #
+  # Though if both the secret and the cipher was changed at the same time,
+  # the above should be combined into:
+  #
+  #   crypt.rotate old_secret, cipher: "aes-256-cbc"
   class MessageEncryptor
+    prepend Messages::Rotator::Encryptor
+
     class << self
       attr_accessor :use_authenticated_message_encryption #:nodoc:
 
@@ -126,7 +152,7 @@ module ActiveSupport
 
     # Decrypt and verify a message. We need to verify the message in order to
     # avoid padding attacks. Reference: https://www.limited-entropy.com/padding-oracle-attacks/.
-    def decrypt_and_verify(data, purpose: nil)
+    def decrypt_and_verify(data, purpose: nil, **)
       _decrypt(verifier.verify(data), purpose)
     end
 
diff --git a/activesupport/lib/active_support/message_verifier.rb b/activesupport/lib/active_support/message_verifier.rb
index 7110d6d2c9..83c39c0a86 100644
--- a/activesupport/lib/active_support/message_verifier.rb
+++ b/activesupport/lib/active_support/message_verifier.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 require "base64"
-require_relative "core_ext/object/blank"
-require_relative "security_utils"
-require_relative "messages/metadata"
+require "active_support/core_ext/object/blank"
+require "active_support/security_utils"
+require "active_support/messages/metadata"
+require "active_support/messages/rotator"
 
 module ActiveSupport
   # +MessageVerifier+ makes it easy to generate and verify messages which are
@@ -30,7 +31,7 @@ module ActiveSupport
   #
   # +MessageVerifier+ creates HMAC signatures using SHA1 hash algorithm by default.
   # If you want to use a different hash algorithm, you can change it by providing
-  # `:digest` key as an option while initializing the verifier:
+  # +:digest+ key as an option while initializing the verifier:
   #
   #   @verifier = ActiveSupport::MessageVerifier.new('s3Krit', digest: 'SHA256')
   #
@@ -73,7 +74,33 @@ module ActiveSupport
   # Then the messages can be verified and returned upto the expire time.
   # Thereafter, the +verified+ method returns +nil+ while +verify+ raises
   # <tt>ActiveSupport::MessageVerifier::InvalidSignature</tt>.
+  #
+  # === Rotating keys
+  #
+  # MessageVerifier also supports rotating out old configurations by falling
+  # back to a stack of verifiers. Call +rotate+ to build and add a verifier to
+  # so either +verified+ or +verify+ will also try verifying with the fallback.
+  #
+  # By default any rotated verifiers use the values of the primary
+  # verifier unless specified otherwise.
+  #
+  # You'd give your verifier the new defaults:
+  #
+  #   verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA512", serializer: JSON)
+  #
+  # Then gradually rotate the old values out by adding them as fallbacks. Any message
+  # generated with the old values will then work until the rotation is removed.
+  #
+  #   verifier.rotate old_secret          # Fallback to an old secret instead of @secret.
+  #   verifier.rotate digest: "SHA256"    # Fallback to an old digest instead of SHA512.
+  #   verifier.rotate serializer: Marshal # Fallback to an old serializer instead of JSON.
+  #
+  # Though the above would most likely be combined into one rotation:
+  #
+  #   verifier.rotate old_secret, digest: "SHA256", serializer: Marshal
   class MessageVerifier
+    prepend Messages::Rotator::Verifier
+
     class InvalidSignature < StandardError; end
 
     def initialize(secret, options = {})
@@ -120,7 +147,7 @@ module ActiveSupport
     #
     #   incompatible_message = "test--dad7b06c94abba8d46a15fafaef56c327665d5ff"
     #   verifier.verified(incompatible_message) # => TypeError: incompatible marshal file format
-    def verified(signed_message, purpose: nil)
+    def verified(signed_message, purpose: nil, **)
       if valid_message?(signed_message)
         begin
           data = signed_message.split("--".freeze)[0]
@@ -145,8 +172,8 @@ module ActiveSupport
     #
     #   other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit'
     #   other_verifier.verify(signed_message) # => ActiveSupport::MessageVerifier::InvalidSignature
-    def verify(signed_message, purpose: nil)
-      verified(signed_message, purpose: purpose) || raise(InvalidSignature)
+    def verify(*args)
+      verified(*args) || raise(InvalidSignature)
     end
 
     # Generates a signed message for the provided value.
diff --git a/activesupport/lib/active_support/messages/rotation_configuration.rb b/activesupport/lib/active_support/messages/rotation_configuration.rb
new file mode 100644
index 0000000000..bd50d6d348
--- /dev/null
+++ b/activesupport/lib/active_support/messages/rotation_configuration.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  module Messages
+    class RotationConfiguration # :nodoc:
+      attr_reader :signed, :encrypted
+
+      def initialize
+        @signed, @encrypted = [], []
+      end
+
+      def rotate(kind, *args)
+        case kind
+        when :signed
+          @signed << args
+        when :encrypted
+          @encrypted << args
+        end
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/messages/rotator.rb b/activesupport/lib/active_support/messages/rotator.rb
new file mode 100644
index 0000000000..823a399d67
--- /dev/null
+++ b/activesupport/lib/active_support/messages/rotator.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  module Messages
+    module Rotator # :nodoc:
+      def initialize(*, **options)
+        super
+
+        @options   = options
+        @rotations = []
+      end
+
+      def rotate(*secrets, **options)
+        @rotations << build_rotation(*secrets, @options.merge(options))
+      end
+
+      module Encryptor
+        include Rotator
+
+        def decrypt_and_verify(*args, on_rotation: nil, **options)
+          super
+        rescue MessageEncryptor::InvalidMessage, MessageVerifier::InvalidSignature
+          run_rotations(on_rotation) { |encryptor| encryptor.decrypt_and_verify(*args, options) } || raise
+        end
+
+        private
+          def build_rotation(secret = @secret, sign_secret = @sign_secret, options)
+            self.class.new(secret, sign_secret, options)
+          end
+      end
+
+      module Verifier
+        include Rotator
+
+        def verified(*args, on_rotation: nil, **options)
+          super || run_rotations(on_rotation) { |verifier| verifier.verified(*args, options) }
+        end
+
+        private
+          def build_rotation(secret = @secret, options)
+            self.class.new(secret, options)
+          end
+      end
+
+      private
+        def run_rotations(on_rotation)
+          @rotations.find do |rotation|
+            if message = yield(rotation) rescue next
+              on_rotation.call if on_rotation
+              return message
+            end
+          end
+        end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/multibyte/chars.rb b/activesupport/lib/active_support/multibyte/chars.rb
index d676827e8e..8152b8fd22 100644
--- a/activesupport/lib/active_support/multibyte/chars.rb
+++ b/activesupport/lib/active_support/multibyte/chars.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../json"
-require_relative "../core_ext/string/access"
-require_relative "../core_ext/string/behavior"
-require_relative "../core_ext/module/delegation"
-require_relative "../core_ext/regexp"
+require "active_support/json"
+require "active_support/core_ext/string/access"
+require "active_support/core_ext/string/behavior"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport #:nodoc:
   module Multibyte #:nodoc:
diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb
index 96a3463905..6207de8094 100644
--- a/activesupport/lib/active_support/notifications.rb
+++ b/activesupport/lib/active_support/notifications.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "notifications/instrumenter"
-require_relative "notifications/fanout"
-require_relative "per_thread_registry"
+require "active_support/notifications/instrumenter"
+require "active_support/notifications/fanout"
+require "active_support/per_thread_registry"
 
 module ActiveSupport
   # = Notifications
diff --git a/activesupport/lib/active_support/number_helper/number_converter.rb b/activesupport/lib/active_support/number_helper/number_converter.rb
index 5ea9c8f113..06ba797a13 100644
--- a/activesupport/lib/active_support/number_helper/number_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_converter.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/big_decimal/conversions"
-require_relative "../core_ext/object/blank"
-require_relative "../core_ext/hash/keys"
-require_relative "../i18n"
-require_relative "../core_ext/class/attribute"
+require "active_support/core_ext/big_decimal/conversions"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/hash/keys"
+require "active_support/i18n"
+require "active_support/core_ext/class/attribute"
 
 module ActiveSupport
   module NumberHelper
diff --git a/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb b/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
index 1943b9e295..3f037c73ed 100644
--- a/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/numeric/inquiry"
+require "active_support/core_ext/numeric/inquiry"
 
 module ActiveSupport
   module NumberHelper
diff --git a/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb b/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
index 3b62fe6819..eb528a0583 100644
--- a/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
@@ -37,26 +37,6 @@ module ActiveSupport
 
       private
 
-        def digits_and_rounded_number(precision)
-          if zero?
-            [1, 0]
-          else
-            digits = digit_count(number)
-            multiplier = 10**(digits - precision)
-            rounded_number = calculate_rounded_number(multiplier)
-            digits = digit_count(rounded_number) # After rounding, the number of digits may have changed
-            [digits, rounded_number]
-          end
-        end
-
-        def calculate_rounded_number(multiplier)
-          (number / BigDecimal.new(multiplier.to_f.to_s)).round * multiplier
-        end
-
-        def digit_count(number)
-          number.zero? ? 1 : (Math.log10(absolute_number(number)) + 1).floor
-        end
-
         def strip_insignificant_zeros
           options[:strip_insignificant_zeros]
         end
diff --git a/activesupport/lib/active_support/option_merger.rb b/activesupport/lib/active_support/option_merger.rb
index 42cbbe7c42..ab9ca727f6 100644
--- a/activesupport/lib/active_support/option_merger.rb
+++ b/activesupport/lib/active_support/option_merger.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/deep_merge"
 
 module ActiveSupport
   class OptionMerger #:nodoc:
diff --git a/activesupport/lib/active_support/ordered_options.rb b/activesupport/lib/active_support/ordered_options.rb
index fa7825b3ba..c4e419f546 100644
--- a/activesupport/lib/active_support/ordered_options.rb
+++ b/activesupport/lib/active_support/ordered_options.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 module ActiveSupport
   # Usually key value pairs are handled something like this:
@@ -24,7 +24,7 @@ module ActiveSupport
   # To raise an exception when the value is blank, append a
   # bang to the key name, like:
   #
-  #   h.dog! # => raises KeyError: key not found: :dog
+  #   h.dog! # => raises KeyError: :dog is blank
   #
   class OrderedOptions < Hash
     alias_method :_get, :[] # preserve the original #[] method
@@ -46,7 +46,7 @@ module ActiveSupport
         bangs = name_string.chomp!("!")
 
         if bangs
-          fetch(name_string.to_sym).presence || raise(KeyError.new("#{name_string} is blank."))
+          self[name_string].presence || raise(KeyError.new(":#{name_string} is blank"))
         else
           self[name_string]
         end
diff --git a/activesupport/lib/active_support/per_thread_registry.rb b/activesupport/lib/active_support/per_thread_registry.rb
index dd0cc6a604..eb92fb4371 100644
--- a/activesupport/lib/active_support/per_thread_registry.rb
+++ b/activesupport/lib/active_support/per_thread_registry.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/module/delegation"
+require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   # NOTE: This approach has been deprecated for end-user code in favor of {thread_mattr_accessor}[rdoc-ref:Module#thread_mattr_accessor] and friends.
diff --git a/activesupport/lib/active_support/rails.rb b/activesupport/lib/active_support/rails.rb
index fe82d1cc14..5c34a0abb3 100644
--- a/activesupport/lib/active_support/rails.rb
+++ b/activesupport/lib/active_support/rails.rb
@@ -11,25 +11,25 @@
 # Rails and can change anytime.
 
 # Defines Object#blank? and Object#present?.
-require_relative "core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 # Rails own autoload, eager_load, etc.
-require_relative "dependencies/autoload"
+require "active_support/dependencies/autoload"
 
 # Support for ClassMethods and the included macro.
-require_relative "concern"
+require "active_support/concern"
 
 # Defines Class#class_attribute.
-require_relative "core_ext/class/attribute"
+require "active_support/core_ext/class/attribute"
 
 # Defines Module#delegate.
-require_relative "core_ext/module/delegation"
+require "active_support/core_ext/module/delegation"
 
 # Defines ActiveSupport::Deprecation.
-require_relative "deprecation"
+require "active_support/deprecation"
 
 # Defines Regexp#match?.
 #
 # This should be removed when Rails needs Ruby 2.4 or later, and the require
 # added where other Regexp extensions are being used (easy to grep).
-require_relative "core_ext/regexp"
+require "active_support/core_ext/regexp"
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index fe132ca7c6..8560eae110 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "i18n_railtie"
+require "active_support/i18n_railtie"
 
 module ActiveSupport
   class Railtie < Rails::Railtie # :nodoc:
@@ -36,14 +36,14 @@ module ActiveSupport
       rescue TZInfo::DataSourceNotFound => e
         raise e.exception "tzinfo-data is not present. Please add gem 'tzinfo-data' to your Gemfile and run bundle install"
       end
-      require_relative "core_ext/time/zones"
+      require "active_support/core_ext/time/zones"
       Time.zone_default = Time.find_zone!(app.config.time_zone)
     end
 
     # Sets the default week start
     # If assigned value is not a valid day symbol (e.g. :sunday, :monday, ...), an exception will be raised.
     initializer "active_support.initialize_beginning_of_week" do |app|
-      require_relative "core_ext/date/calculations"
+      require "active_support/core_ext/date/calculations"
       beginning_of_week_default = Date.find_beginning_of_week!(app.config.beginning_of_week)
 
       Date.beginning_of_week_default = beginning_of_week_default
diff --git a/activesupport/lib/active_support/reloader.rb b/activesupport/lib/active_support/reloader.rb
index 44062e3491..b26d9c3665 100644
--- a/activesupport/lib/active_support/reloader.rb
+++ b/activesupport/lib/active_support/reloader.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "execution_wrapper"
+require "active_support/execution_wrapper"
 
 module ActiveSupport
   #--
@@ -28,14 +28,17 @@ module ActiveSupport
 
     define_callbacks :class_unload
 
+    # Registers a callback that will run once at application startup and every time the code is reloaded.
     def self.to_prepare(*args, &block)
       set_callback(:prepare, *args, &block)
     end
 
+    # Registers a callback that will run immediately before the classes are unloaded.
     def self.before_class_unload(*args, &block)
       set_callback(:class_unload, *args, &block)
     end
 
+    # Registers a callback that will run immediately after the classes are unloaded.
     def self.after_class_unload(*args, &block)
       set_callback(:class_unload, :after, *args, &block)
     end
diff --git a/activesupport/lib/active_support/rescuable.rb b/activesupport/lib/active_support/rescuable.rb
index 2f6aeef48a..e0fa29cacb 100644
--- a/activesupport/lib/active_support/rescuable.rb
+++ b/activesupport/lib/active_support/rescuable.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "core_ext/class/attribute"
-require_relative "core_ext/string/inflections"
+require "active_support/concern"
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/string/inflections"
 
 module ActiveSupport
   # Rescuable module adds support for easier exception handling.
diff --git a/activesupport/lib/active_support/security_utils.rb b/activesupport/lib/active_support/security_utils.rb
index 51870559ec..20b6b9cd3f 100644
--- a/activesupport/lib/active_support/security_utils.rb
+++ b/activesupport/lib/active_support/security_utils.rb
@@ -1,17 +1,15 @@
 # frozen_string_literal: true
 
-require "digest"
+require "digest/sha2"
 
 module ActiveSupport
   module SecurityUtils
-    # Constant time string comparison.
+    # Constant time string comparison, for fixed length strings.
     #
     # The values compared should be of fixed length, such as strings
-    # that have already been processed by HMAC. This should not be used
-    # on variable length plaintext strings because it could leak length info
-    # via timing attacks.
-    def secure_compare(a, b)
-      return false unless a.bytesize == b.bytesize
+    # that have already been processed by HMAC. Raises in case of length mismatch.
+    def fixed_length_secure_compare(a, b)
+      raise ArgumentError, "string length mismatch." unless a.bytesize == b.bytesize
 
       l = a.unpack "C#{a.bytesize}"
 
@@ -19,11 +17,15 @@ module ActiveSupport
       b.each_byte { |byte| res |= byte ^ l.shift }
       res == 0
     end
-    module_function :secure_compare
+    module_function :fixed_length_secure_compare
 
-    def variable_size_secure_compare(a, b) # :nodoc:
-      secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b))
+    # Constant time string comparison, for variable length strings.
+    #
+    # The values are first processed by SHA256, so that we don't leak length info
+    # via timing attacks.
+    def secure_compare(a, b)
+      fixed_length_secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b)) && a == b
     end
-    module_function :variable_size_secure_compare
+    module_function :secure_compare
   end
 end
diff --git a/activesupport/lib/active_support/subscriber.rb b/activesupport/lib/active_support/subscriber.rb
index 7913bb815e..d6dd5474d0 100644
--- a/activesupport/lib/active_support/subscriber.rb
+++ b/activesupport/lib/active_support/subscriber.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "per_thread_registry"
-require_relative "notifications"
+require "active_support/per_thread_registry"
+require "active_support/notifications"
 
 module ActiveSupport
   # ActiveSupport::Subscriber is an object set to consume
diff --git a/activesupport/lib/active_support/tagged_logging.rb b/activesupport/lib/active_support/tagged_logging.rb
index fe13eaed4e..8561cba9f1 100644
--- a/activesupport/lib/active_support/tagged_logging.rb
+++ b/activesupport/lib/active_support/tagged_logging.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/module/delegation"
-require_relative "core_ext/object/blank"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/object/blank"
 require "logger"
-require_relative "logger"
+require "active_support/logger"
 
 module ActiveSupport
   # Wraps any standard Logger object to provide tagging capabilities.
diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index bc42758f76..d1f7e6ea09 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -2,16 +2,15 @@
 
 gem "minitest" # make sure we get the gem, not stdlib
 require "minitest"
-require_relative "testing/tagged_logging"
-require_relative "testing/setup_and_teardown"
-require_relative "testing/assertions"
-require_relative "testing/deprecation"
-require_relative "testing/declarative"
-require_relative "testing/isolation"
-require_relative "testing/constant_lookup"
-require_relative "testing/time_helpers"
-require_relative "testing/file_fixtures"
-require_relative "core_ext/kernel/reporting"
+require "active_support/testing/tagged_logging"
+require "active_support/testing/setup_and_teardown"
+require "active_support/testing/assertions"
+require "active_support/testing/deprecation"
+require "active_support/testing/declarative"
+require "active_support/testing/isolation"
+require "active_support/testing/constant_lookup"
+require "active_support/testing/time_helpers"
+require "active_support/testing/file_fixtures"
 
 module ActiveSupport
   class TestCase < ::Minitest::Test
diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index e2bc51ff7a..b24aa36ede 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -159,7 +159,7 @@ module ActiveSupport
         if to == UNTRACKED
           error = "#{expression.inspect} didn't change"
           error = "#{message}.\n#{error}" if message
-          assert_not_equal before, after, error
+          assert before != after, error
         else
           error = "#{expression.inspect} didn't change to #{to}"
           error = "#{message}.\n#{error}" if message
@@ -190,7 +190,7 @@ module ActiveSupport
 
         error = "#{expression.inspect} did change to #{after}"
         error = "#{message}.\n#{error}" if message
-        assert_equal before, after, error
+        assert before == after, error
 
         retval
       end
diff --git a/activesupport/lib/active_support/testing/constant_lookup.rb b/activesupport/lib/active_support/testing/constant_lookup.rb
index 0fedd486fb..51167e9237 100644
--- a/activesupport/lib/active_support/testing/constant_lookup.rb
+++ b/activesupport/lib/active_support/testing/constant_lookup.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../concern"
-require_relative "../inflector"
+require "active_support/concern"
+require "active_support/inflector"
 
 module ActiveSupport
   module Testing
diff --git a/activesupport/lib/active_support/testing/deprecation.rb b/activesupport/lib/active_support/testing/deprecation.rb
index 4fda4832cc..f655435729 100644
--- a/activesupport/lib/active_support/testing/deprecation.rb
+++ b/activesupport/lib/active_support/testing/deprecation.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../deprecation"
-require_relative "../core_ext/regexp"
+require "active_support/deprecation"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   module Testing
diff --git a/activesupport/lib/active_support/testing/isolation.rb b/activesupport/lib/active_support/testing/isolation.rb
index 954197a3cc..fa9bebb181 100644
--- a/activesupport/lib/active_support/testing/isolation.rb
+++ b/activesupport/lib/active_support/testing/isolation.rb
@@ -55,7 +55,7 @@ module ActiveSupport
           write.close
           result = read.read
           Process.wait2(pid)
-          return result.unpack("m")[0]
+          result.unpack("m")[0]
         end
       end
 
diff --git a/activesupport/lib/active_support/testing/setup_and_teardown.rb b/activesupport/lib/active_support/testing/setup_and_teardown.rb
index 18de7185d9..1dbf3c5da0 100644
--- a/activesupport/lib/active_support/testing/setup_and_teardown.rb
+++ b/activesupport/lib/active_support/testing/setup_and_teardown.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../concern"
-require_relative "../callbacks"
+require "active_support/concern"
+require "active_support/callbacks"
 
 module ActiveSupport
   module Testing
diff --git a/activesupport/lib/active_support/testing/time_helpers.rb b/activesupport/lib/active_support/testing/time_helpers.rb
index fa5f46736c..8c620e7f8c 100644
--- a/activesupport/lib/active_support/testing/time_helpers.rb
+++ b/activesupport/lib/active_support/testing/time_helpers.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/string/strip" # for strip_heredoc
-require_relative "../core_ext/time/calculations"
+require "active_support/core_ext/string/strip" # for strip_heredoc
+require "active_support/core_ext/time/calculations"
 require "concurrent/map"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/time.rb b/activesupport/lib/active_support/time.rb
index fb1c5cee1c..51854675bf 100644
--- a/activesupport/lib/active_support/time.rb
+++ b/activesupport/lib/active_support/time.rb
@@ -9,12 +9,12 @@ end
 require "date"
 require "time"
 
-require_relative "core_ext/time"
-require_relative "core_ext/date"
-require_relative "core_ext/date_time"
+require "active_support/core_ext/time"
+require "active_support/core_ext/date"
+require "active_support/core_ext/date_time"
 
-require_relative "core_ext/integer/time"
-require_relative "core_ext/numeric/time"
+require "active_support/core_ext/integer/time"
+require "active_support/core_ext/numeric/time"
 
-require_relative "core_ext/string/conversions"
-require_relative "core_ext/string/zones"
+require "active_support/core_ext/string/conversions"
+require "active_support/core_ext/string/zones"
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index 59cafa193e..20650ce714 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "duration"
-require_relative "values/time_zone"
-require_relative "core_ext/object/acts_like"
-require_relative "core_ext/date_and_time/compatibility"
+require "active_support/duration"
+require "active_support/values/time_zone"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/date_and_time/compatibility"
 
 module ActiveSupport
   # A Time-like class that can represent a time in any time zone. Necessary
diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index c871f11422..4d81ac939e 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -2,7 +2,7 @@
 
 require "tzinfo"
 require "concurrent/map"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 module ActiveSupport
   # The TimeZone class serves as a wrapper around TZInfo::Timezone instances.
@@ -30,7 +30,7 @@ module ActiveSupport
   class TimeZone
     # Keys are Rails TimeZone names, values are TZInfo identifiers.
     MAPPING = {
-      "International Date Line West" => "Pacific/Midway",
+      "International Date Line West" => "Etc/GMT+12",
       "Midway Island"                => "Pacific/Midway",
       "American Samoa"               => "Pacific/Pago_Pago",
       "Hawaii"                       => "Pacific/Honolulu",
@@ -256,6 +256,13 @@ module ActiveSupport
         @country_zones[code] ||= load_country_zones(code)
       end
 
+      def clear #:nodoc:
+        @lazy_zones_map = Concurrent::Map.new
+        @country_zones  = Concurrent::Map.new
+        @zones = nil
+        @zones_map = nil
+      end
+
       private
         def load_country_zones(code)
           country = TZInfo::Country.get(code)
@@ -269,9 +276,8 @@ module ActiveSupport
         end
 
         def zones_map
-          @zones_map ||= begin
-            MAPPING.each_key { |place| self[place] } # load all the zones
-            @lazy_zones_map
+          @zones_map ||= MAPPING.each_with_object({}) do |(name, _), zones|
+            zones[name] = self[name]
           end
         end
     end
@@ -506,7 +512,7 @@ module ActiveSupport
     # Available so that TimeZone instances respond like TZInfo::Timezone
     # instances.
     def period_for_local(time, dst = true)
-      tzinfo.period_for_local(time, dst)
+      tzinfo.period_for_local(time, dst) { |periods| periods.last }
     end
 
     def periods_for_local(time) #:nodoc:
diff --git a/activesupport/lib/active_support/xml_mini.rb b/activesupport/lib/active_support/xml_mini.rb
index d49ee4508e..ee2048cb54 100644
--- a/activesupport/lib/active_support/xml_mini.rb
+++ b/activesupport/lib/active_support/xml_mini.rb
@@ -3,9 +3,9 @@
 require "time"
 require "base64"
 require "bigdecimal"
-require_relative "core_ext/module/delegation"
-require_relative "core_ext/string/inflections"
-require_relative "core_ext/date_time/calculations"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/date_time/calculations"
 
 module ActiveSupport
   # = XmlMini
@@ -199,7 +199,7 @@ module ActiveSupport
         if name.is_a?(Module)
           name
         else
-          require_relative "xml_mini/#{name.downcase}"
+          require "active_support/xml_mini/#{name.downcase}"
           ActiveSupport.const_get("XmlMini_#{name}")
         end
       end
diff --git a/activesupport/lib/active_support/xml_mini/jdom.rb b/activesupport/lib/active_support/xml_mini/jdom.rb
index ecfe389f10..7f94a64016 100644
--- a/activesupport/lib/active_support/xml_mini/jdom.rb
+++ b/activesupport/lib/active_support/xml_mini/jdom.rb
@@ -5,7 +5,7 @@ raise "JRuby is required to use the JDOM backend for XmlMini" unless RUBY_PLATFO
 require "jruby"
 include Java
 
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 java_import javax.xml.parsers.DocumentBuilder unless defined? DocumentBuilder
 java_import javax.xml.parsers.DocumentBuilderFactory unless defined? DocumentBuilderFactory
diff --git a/activesupport/lib/active_support/xml_mini/libxml.rb b/activesupport/lib/active_support/xml_mini/libxml.rb
index b1be38fadf..0b000fea60 100644
--- a/activesupport/lib/active_support/xml_mini/libxml.rb
+++ b/activesupport/lib/active_support/xml_mini/libxml.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "libxml"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/libxmlsax.rb b/activesupport/lib/active_support/xml_mini/libxmlsax.rb
index 3ad494310d..dcf16e6084 100644
--- a/activesupport/lib/active_support/xml_mini/libxmlsax.rb
+++ b/activesupport/lib/active_support/xml_mini/libxmlsax.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "libxml"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/nokogiri.rb b/activesupport/lib/active_support/xml_mini/nokogiri.rb
index 1987330c25..5ee6fc8159 100644
--- a/activesupport/lib/active_support/xml_mini/nokogiri.rb
+++ b/activesupport/lib/active_support/xml_mini/nokogiri.rb
@@ -6,7 +6,7 @@ rescue LoadError => e
   $stderr.puts "You don't have nokogiri installed in your application. Please add it to your Gemfile and run bundle install"
   raise e
 end
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/nokogirisax.rb b/activesupport/lib/active_support/xml_mini/nokogirisax.rb
index fb57eb8867..b01ed00a14 100644
--- a/activesupport/lib/active_support/xml_mini/nokogirisax.rb
+++ b/activesupport/lib/active_support/xml_mini/nokogirisax.rb
@@ -6,7 +6,7 @@ rescue LoadError => e
   $stderr.puts "You don't have nokogiri installed in your application. Please add it to your Gemfile and run bundle install"
   raise e
 end
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/rexml.rb b/activesupport/lib/active_support/xml_mini/rexml.rb
index 5fd8978fc0..32458d5b0d 100644
--- a/activesupport/lib/active_support/xml_mini/rexml.rb
+++ b/activesupport/lib/active_support/xml_mini/rexml.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/kernel/reporting"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb b/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
index 2fa2d7af88..16b7abc679 100644
--- a/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
@@ -8,7 +8,9 @@ module CacheIncrementDecrementBehavior
     assert_equal 2, @cache.read("foo").to_i
     assert_equal 3, @cache.increment("foo")
     assert_equal 3, @cache.read("foo").to_i
-    assert_nil @cache.increment("bar")
+
+    missing = @cache.increment("bar")
+    assert(missing.nil? || missing == 1)
   end
 
   def test_decrement
@@ -18,6 +20,8 @@ module CacheIncrementDecrementBehavior
     assert_equal 2, @cache.read("foo").to_i
     assert_equal 1, @cache.decrement("foo")
     assert_equal 1, @cache.read("foo").to_i
-    assert_nil @cache.decrement("bar")
+
+    missing = @cache.decrement("bar")
+    assert(missing.nil? || missing == -1)
   end
 end
diff --git a/activesupport/test/cache/behaviors/cache_store_behavior.rb b/activesupport/test/cache/behaviors/cache_store_behavior.rb
index 582e902f72..73a9b2a71c 100644
--- a/activesupport/test/cache/behaviors/cache_store_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_store_behavior.rb
@@ -146,6 +146,16 @@ module CacheStoreBehavior
     assert_nil @cache.read("foo")
   end
 
+  def test_read_and_write_uncompressed_small_data
+    @cache.write("foo", "bar", compress: false)
+    assert_equal "bar", @cache.read("foo")
+  end
+
+  def test_read_and_write_uncompressed_nil
+    @cache.write("foo", nil, compress: false)
+    assert_nil @cache.read("foo")
+  end
+
   def test_cache_key
     obj = Object.new
     def obj.cache_key
diff --git a/activesupport/test/cache/behaviors/local_cache_behavior.rb b/activesupport/test/cache/behaviors/local_cache_behavior.rb
index 8dec8090b1..f7302df4c8 100644
--- a/activesupport/test/cache/behaviors/local_cache_behavior.rb
+++ b/activesupport/test/cache/behaviors/local_cache_behavior.rb
@@ -20,7 +20,11 @@ module LocalCacheBehavior
   end
 
   def test_cleanup_clears_local_cache_but_not_remote_cache
-    skip unless @cache.class.instance_methods(false).include?(:cleanup)
+    begin
+      @cache.cleanup
+    rescue NotImplementedError
+      skip
+    end
 
     @cache.with_local_cache do
       @cache.write("foo", "bar")
diff --git a/activesupport/test/cache/cache_entry_test.rb b/activesupport/test/cache/cache_entry_test.rb
index 51b214ad8f..80ff7ad564 100644
--- a/activesupport/test/cache/cache_entry_test.rb
+++ b/activesupport/test/cache/cache_entry_test.rb
@@ -14,16 +14,23 @@ class CacheEntryTest < ActiveSupport::TestCase
     end
   end
 
-  def test_compress_values
+  def test_compressed_values
     value = "value" * 100
     entry = ActiveSupport::Cache::Entry.new(value, compress: true, compress_threshold: 1)
     assert_equal value, entry.value
     assert(value.bytesize > entry.size, "value is compressed")
   end
 
-  def test_non_compress_values
+  def test_compressed_by_default
     value = "value" * 100
-    entry = ActiveSupport::Cache::Entry.new(value)
+    entry = ActiveSupport::Cache::Entry.new(value, compress_threshold: 1)
+    assert_equal value, entry.value
+    assert(value.bytesize > entry.size, "value is compressed")
+  end
+
+  def test_uncompressed_values
+    value = "value" * 100
+    entry = ActiveSupport::Cache::Entry.new(value, compress: false)
     assert_equal value, entry.value
     assert_equal value.bytesize, entry.size
   end
diff --git a/activesupport/test/cache/stores/file_store_test.rb b/activesupport/test/cache/stores/file_store_test.rb
index 391ab60b3a..66231b0a82 100644
--- a/activesupport/test/cache/stores/file_store_test.rb
+++ b/activesupport/test/cache/stores/file_store_test.rb
@@ -118,6 +118,7 @@ class FileStoreTest < ActiveSupport::TestCase
       assert_not @cache.exist?("foo")
       assert @cache.exist?("baz")
       assert @cache.exist?("quux")
+      assert_equal 2, Dir.glob(File.join(cache_dir, "**")).size
     end
   end
 
diff --git a/activesupport/test/cache/stores/mem_cache_store_test.rb b/activesupport/test/cache/stores/mem_cache_store_test.rb
index 1b73fb65eb..99624caf8a 100644
--- a/activesupport/test/cache/stores/mem_cache_store_test.rb
+++ b/activesupport/test/cache/stores/mem_cache_store_test.rb
@@ -57,6 +57,22 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     end
   end
 
+  def test_increment_expires_in
+    cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
+    cache.clear
+    assert_called_with cache.instance_variable_get(:@data), :incr, [ "foo", 1, 60 ] do
+      cache.increment("foo", 1, expires_in: 60)
+    end
+  end
+
+  def test_decrement_expires_in
+    cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
+    cache.clear
+    assert_called_with cache.instance_variable_get(:@data), :decr, [ "foo", 1, 60 ] do
+      cache.decrement("foo", 1, expires_in: 60)
+    end
+  end
+
   def test_local_cache_raw_values_with_marshal
     cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
     cache.clear
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
new file mode 100644
index 0000000000..988de9207f
--- /dev/null
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -0,0 +1,151 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/cache"
+require "active_support/cache/redis_cache_store"
+require_relative "../behaviors"
+
+module ActiveSupport::Cache::RedisCacheStoreTests
+  class LookupTest < ActiveSupport::TestCase
+    test "may be looked up as :redis_cache_store" do
+      assert_kind_of ActiveSupport::Cache::RedisCacheStore,
+        ActiveSupport::Cache.lookup_store(:redis_cache_store)
+    end
+  end
+
+  class InitializationTest < ActiveSupport::TestCase
+    test "omitted URL uses Redis client with default settings" do
+      assert_called_with Redis, :new, [
+        url: nil,
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build
+      end
+    end
+
+    test "no URLs uses Redis client with default settings" do
+      assert_called_with Redis, :new, [
+        url: nil,
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build url: []
+      end
+    end
+
+    test "singular URL uses Redis client" do
+      assert_called_with Redis, :new, [
+        url: "redis://localhost:6379/0",
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build url: "redis://localhost:6379/0"
+      end
+    end
+
+    test "one URL uses Redis client" do
+      assert_called_with Redis, :new, [
+        url: "redis://localhost:6379/0",
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build url: %w[ redis://localhost:6379/0 ]
+      end
+    end
+
+    test "multiple URLs uses Redis::Distributed client" do
+      assert_called_with Redis, :new, [
+        [ url: "redis://localhost:6379/0",
+          connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+          reconnect_attempts: 0 ],
+        [ url: "redis://localhost:6379/1",
+          connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+          reconnect_attempts: 0 ],
+      ], returns: Redis.new do
+        @cache = build url: %w[ redis://localhost:6379/0 redis://localhost:6379/1 ]
+        assert_kind_of ::Redis::Distributed, @cache.redis
+      end
+    end
+
+    test "block argument uses yielded client" do
+      block = -> { :custom_redis_client }
+      assert_called block, :call do
+        build redis: block
+      end
+    end
+
+    private
+      def build(**kwargs)
+        ActiveSupport::Cache::RedisCacheStore.new(**kwargs).tap do |cache|
+          cache.redis
+        end
+      end
+  end
+
+  class StoreTest < ActiveSupport::TestCase
+    setup do
+      @namespace = "namespace"
+
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, expires_in: 60)
+      #@cache.logger = Logger.new($stdout)  # For test debugging
+
+      # For LocalCacheBehavior tests
+      @peek = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace)
+    end
+
+    teardown do
+      @cache.clear
+      @cache.redis.disconnect!
+    end
+  end
+
+  class RedisCacheStoreCommonBehaviorTest < StoreTest
+    include CacheStoreBehavior
+    include CacheStoreVersionBehavior
+    include LocalCacheBehavior
+    include CacheIncrementDecrementBehavior
+    include AutoloadingCacheBehavior
+  end
+
+  # Separate test class so we can omit the namespace which causes expected,
+  # appropriate complaints about incompatible string encodings.
+  class KeyEncodingSafetyTest < StoreTest
+    include EncodedKeyCacheBehavior
+
+    setup do
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1)
+      @cache.logger = nil
+    end
+  end
+
+  class StoreAPITest < StoreTest
+  end
+
+  class FailureSafetyTest < StoreTest
+    test "fetch read failure returns nil" do
+    end
+
+    test "fetch read failure does not attempt to write" do
+    end
+
+    test "write failure returns nil" do
+    end
+  end
+
+  class DeleteMatchedTest < StoreTest
+    test "deletes keys matching glob" do
+      @cache.write("foo", "bar")
+      @cache.write("fu", "baz")
+      @cache.delete_matched("foo*")
+      assert !@cache.exist?("foo")
+      assert @cache.exist?("fu")
+    end
+
+    test "fails with regexp matchers" do
+      assert_raise ArgumentError do
+        @cache.delete_matched(/OO/i)
+      end
+    end
+  end
+end
diff --git a/activesupport/test/callbacks_test.rb b/activesupport/test/callbacks_test.rb
index 3902e41a60..5f894db46f 100644
--- a/activesupport/test/callbacks_test.rb
+++ b/activesupport/test/callbacks_test.rb
@@ -193,13 +193,6 @@ module CallbacksTest
     before_save Proc.new { |r| r.history << "b00m" }, if: :no
     before_save Proc.new { |r| r.history << [:before_save, :symbol] }, unless: :no
     before_save Proc.new { |r| r.history << "b00m" }, unless: :yes
-    # string
-    ActiveSupport::Deprecation.silence do
-      before_save Proc.new { |r| r.history << [:before_save, :string] }, if: "yes"
-      before_save Proc.new { |r| r.history << "b00m" }, if: "no"
-      before_save Proc.new { |r| r.history << [:before_save, :string] }, unless: "no"
-      before_save Proc.new { |r| r.history << "b00m" }, unless: "yes"
-    end
     # Combined if and unless
     before_save Proc.new { |r| r.history << [:before_save, :combined_symbol] }, if: :yes, unless: :no
     before_save Proc.new { |r| r.history << "b00m" }, if: :yes, unless: :yes
@@ -592,8 +585,6 @@ module CallbacksTest
         [:before_save, :proc],
         [:before_save, :symbol],
         [:before_save, :symbol],
-        [:before_save, :string],
-        [:before_save, :string],
         [:before_save, :combined_symbol],
       ], person.history
     end
@@ -1182,14 +1173,15 @@ module CallbacksTest
     end
   end
 
-  class DeprecatedWarningTest < ActiveSupport::TestCase
-    def test_deprecate_string_conditional_options
+  class NotSupportedStringConditionalTest < ActiveSupport::TestCase
+    def test_string_conditional_options
       klass = Class.new(Record)
 
-      assert_deprecated { klass.before_save :tweedle, if: "true" }
-      assert_deprecated { klass.after_save :tweedle, unless: "false" }
-      assert_deprecated { klass.skip_callback :save, :before, :tweedle, if: "true" }
-      assert_deprecated { klass.skip_callback :save, :after, :tweedle, unless: "false" }
+      assert_raises(ArgumentError) { klass.before_save :tweedle, if: ["true"] }
+      assert_raises(ArgumentError) { klass.before_save :tweedle, if: "true" }
+      assert_raises(ArgumentError) { klass.after_save :tweedle, unless: "false" }
+      assert_raises(ArgumentError) { klass.skip_callback :save, :before, :tweedle, if: "true" }
+      assert_raises(ArgumentError) { klass.skip_callback :save, :after, :tweedle, unless: "false" }
     end
   end
 
diff --git a/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb b/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb
new file mode 100644
index 0000000000..2d0f45ec5f
--- /dev/null
+++ b/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "concurrent/atomic/count_down_latch"
+require "active_support/concurrency/load_interlock_aware_monitor"
+
+module ActiveSupport
+  module Concurrency
+    class LoadInterlockAwareMonitorTest < ActiveSupport::TestCase
+      def setup
+        @monitor = ActiveSupport::Concurrency::LoadInterlockAwareMonitor.new
+      end
+
+      def test_entering_with_no_blocking
+        assert @monitor.mon_enter
+      end
+
+      def test_entering_with_blocking
+        load_interlock_latch = Concurrent::CountDownLatch.new
+        monitor_latch = Concurrent::CountDownLatch.new
+
+        able_to_use_monitor = false
+        able_to_load = false
+
+        thread_with_load_interlock = Thread.new do
+          ActiveSupport::Dependencies.interlock.running do
+            load_interlock_latch.count_down
+            monitor_latch.wait
+
+            @monitor.synchronize do
+              able_to_use_monitor = true
+            end
+          end
+        end
+
+        thread_with_monitor_lock = Thread.new do
+          @monitor.synchronize do
+            monitor_latch.count_down
+            load_interlock_latch.wait
+
+            ActiveSupport::Dependencies.interlock.loading do
+              able_to_load = true
+            end
+          end
+        end
+
+        thread_with_load_interlock.join
+        thread_with_monitor_lock.join
+
+        assert able_to_use_monitor
+        assert able_to_load
+      end
+    end
+  end
+end
diff --git a/activesupport/test/core_ext/date_and_time_behavior.rb b/activesupport/test/core_ext/date_and_time_behavior.rb
index 256353c309..91b92043d0 100644
--- a/activesupport/test/core_ext/date_and_time_behavior.rb
+++ b/activesupport/test/core_ext/date_and_time_behavior.rb
@@ -9,6 +9,11 @@ module DateAndTimeBehavior
   end
 
   def test_prev_day
+    assert_equal date_time_init(2005, 2, 24, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(-2)
+    assert_equal date_time_init(2005, 2, 23, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(0)
+    assert_equal date_time_init(2005, 2, 21, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(1)
+    assert_equal date_time_init(2005, 2, 20, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(2)
     assert_equal date_time_init(2005, 2, 21, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day
     assert_equal date_time_init(2005, 2, 28, 10, 10, 10), date_time_init(2005, 3, 2, 10, 10, 10).prev_day.prev_day
   end
@@ -19,6 +24,11 @@ module DateAndTimeBehavior
   end
 
   def test_next_day
+    assert_equal date_time_init(2005, 2, 20, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(-2)
+    assert_equal date_time_init(2005, 2, 21, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(0)
+    assert_equal date_time_init(2005, 2, 23, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(1)
+    assert_equal date_time_init(2005, 2, 24, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(2)
     assert_equal date_time_init(2005, 2, 23, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day
     assert_equal date_time_init(2005, 3, 2, 10, 10, 10),  date_time_init(2005, 2, 28, 10, 10, 10).next_day.next_day
   end
@@ -151,6 +161,16 @@ module DateAndTimeBehavior
     assert_equal date_time_init(2015, 1, 5, 15, 15, 10), date_time_init(2015, 1, 3, 15, 15, 10).next_weekday
   end
 
+  def test_next_month
+    assert_equal date_time_init(2004, 12, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(-2)
+    assert_equal date_time_init(2005, 1, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(0)
+    assert_equal date_time_init(2005, 3, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(1)
+    assert_equal date_time_init(2005, 4, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(2)
+    assert_equal date_time_init(2005, 3, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month
+    assert_equal date_time_init(2005, 4, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month.next_month
+  end
+
   def test_next_month_on_31st
     assert_equal date_time_init(2005, 9, 30, 15, 15, 10), date_time_init(2005, 8, 31, 15, 15, 10).next_month
   end
@@ -160,7 +180,13 @@ module DateAndTimeBehavior
   end
 
   def test_next_year
+    assert_equal date_time_init(2003, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(-2)
+    assert_equal date_time_init(2004, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(-1)
+    assert_equal date_time_init(2005, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(0)
+    assert_equal date_time_init(2006, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(1)
+    assert_equal date_time_init(2007, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(2)
     assert_equal date_time_init(2006, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year
+    assert_equal date_time_init(2007, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year.next_year
   end
 
   def test_prev_week
@@ -203,6 +229,16 @@ module DateAndTimeBehavior
     assert_equal date_time_init(2015, 1, 2, 15, 15, 10), date_time_init(2015, 1, 4, 15, 15, 10).prev_weekday
   end
 
+  def test_prev_month
+    assert_equal date_time_init(2005, 4, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(-2)
+    assert_equal date_time_init(2005, 3, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(0)
+    assert_equal date_time_init(2005, 1, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(1)
+    assert_equal date_time_init(2004, 12, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(2)
+    assert_equal date_time_init(2005, 1, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month
+    assert_equal date_time_init(2004, 12, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month.prev_month
+  end
+
   def test_prev_month_on_31st
     assert_equal date_time_init(2004, 2, 29, 10, 10, 10), date_time_init(2004, 3, 31, 10, 10, 10).prev_month
   end
@@ -212,7 +248,21 @@ module DateAndTimeBehavior
   end
 
   def test_prev_year
+    assert_equal date_time_init(2007, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(-2)
+    assert_equal date_time_init(2006, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(-1)
+    assert_equal date_time_init(2005, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(0)
+    assert_equal date_time_init(2004, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(1)
+    assert_equal date_time_init(2003, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(2)
     assert_equal date_time_init(2004, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year
+    assert_equal date_time_init(2003, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year.prev_year
+  end
+
+  def test_last_month_on_31st
+    assert_equal date_time_init(2004, 2, 29, 0, 0, 0), date_time_init(2004, 3, 31, 0, 0, 0).last_month
+  end
+
+  def test_last_year
+    assert_equal date_time_init(2004, 6, 5, 10, 0, 0), date_time_init(2005, 6, 5, 10, 0, 0).last_year
   end
 
   def test_days_to_week_start
@@ -278,6 +328,26 @@ module DateAndTimeBehavior
     assert_equal date_time_init(2007, 12, 31, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 12, 31, 10, 10, 10).end_of_year
   end
 
+  def test_next_occurring
+    assert_equal date_time_init(2017, 12, 18, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:monday)
+    assert_equal date_time_init(2017, 12, 19, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:tuesday)
+    assert_equal date_time_init(2017, 12, 20, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:wednesday)
+    assert_equal date_time_init(2017, 12, 21, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:thursday)
+    assert_equal date_time_init(2017, 12, 15, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:friday)
+    assert_equal date_time_init(2017, 12, 16, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:saturday)
+    assert_equal date_time_init(2017, 12, 17, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:sunday)
+  end
+
+  def test_prev_occurring
+    assert_equal date_time_init(2017, 12, 11, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:monday)
+    assert_equal date_time_init(2017, 12, 12, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:tuesday)
+    assert_equal date_time_init(2017, 12, 13, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:wednesday)
+    assert_equal date_time_init(2017, 12,  7, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:thursday)
+    assert_equal date_time_init(2017, 12,  8, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:friday)
+    assert_equal date_time_init(2017, 12,  9, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:saturday)
+    assert_equal date_time_init(2017, 12, 10, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:sunday)
+  end
+
   def test_monday_with_default_beginning_of_week_set
     with_bw_default(:saturday) do
       assert_equal date_time_init(2012, 9, 17, 0, 0, 0), date_time_init(2012, 9, 18, 0, 0, 0).monday
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index b8672eac4b..0c6f3f595a 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -120,10 +120,6 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Date.new(1582, 10, 4), Date.new(1583, 10, 14).prev_year
   end
 
-  def test_last_year
-    assert_equal Date.new(2004, 6, 5),  Date.new(2005, 6, 5).last_year
-  end
-
   def test_last_year_in_leap_years
     assert_equal Date.new(1999, 2, 28), Date.new(2000, 2, 29).last_year
   end
@@ -185,10 +181,6 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Date.new(1582, 10, 18), Date.new(1582, 10, 4).next_week
   end
 
-  def test_last_month_on_31st
-    assert_equal Date.new(2004, 2, 29), Date.new(2004, 3, 31).last_month
-  end
-
   def test_last_quarter_on_31st
     assert_equal Date.new(2004, 2, 29), Date.new(2004, 5, 31).last_quarter
   end
diff --git a/activesupport/test/core_ext/date_time_ext_test.rb b/activesupport/test/core_ext/date_time_ext_test.rb
index a3c2018a31..ed962803fa 100644
--- a/activesupport/test/core_ext/date_time_ext_test.rb
+++ b/activesupport/test/core_ext/date_time_ext_test.rb
@@ -30,28 +30,6 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     end
   end
 
-  def test_next_occur
-    datetime = DateTime.new(2016, 9, 24, 0, 0) # saturday
-    assert_equal datetime.next_occurring(:monday), datetime.since(2.days)
-    assert_equal datetime.next_occurring(:tuesday), datetime.since(3.days)
-    assert_equal datetime.next_occurring(:wednesday), datetime.since(4.days)
-    assert_equal datetime.next_occurring(:thursday), datetime.since(5.days)
-    assert_equal datetime.next_occurring(:friday), datetime.since(6.days)
-    assert_equal datetime.next_occurring(:saturday), datetime.since(1.week)
-    assert_equal datetime.next_occurring(:sunday), datetime.since(1.day)
-  end
-
-  def test_prev_occur
-    datetime = DateTime.new(2016, 9, 24, 0, 0) # saturday
-    assert_equal datetime.prev_occurring(:monday), datetime.ago(5.days)
-    assert_equal datetime.prev_occurring(:tuesday), datetime.ago(4.days)
-    assert_equal datetime.prev_occurring(:wednesday), datetime.ago(3.days)
-    assert_equal datetime.prev_occurring(:thursday), datetime.ago(2.days)
-    assert_equal datetime.prev_occurring(:friday), datetime.ago(1.day)
-    assert_equal datetime.prev_occurring(:saturday), datetime.ago(1.week)
-    assert_equal datetime.prev_occurring(:sunday), datetime.ago(6.days)
-  end
-
   def test_readable_inspect
     datetime = DateTime.new(2005, 2, 21, 14, 30, 0)
     assert_equal "Mon, 21 Feb 2005 14:30:00 +0000", datetime.readable_inspect
@@ -162,10 +140,6 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal DateTime.civil(2005, 4, 30, 23, 59, Rational(59999999999, 1000000000)), DateTime.civil(2005, 4, 20, 10, 10, 10).end_of_month
   end
 
-  def test_last_year
-    assert_equal DateTime.civil(2004, 6, 5, 10),  DateTime.civil(2005, 6, 5, 10, 0, 0).last_year
-  end
-
   def test_ago
     assert_equal DateTime.civil(2005, 2, 22, 10, 10, 9),  DateTime.civil(2005, 2, 22, 10, 10, 10).ago(1)
     assert_equal DateTime.civil(2005, 2, 22, 9, 10, 10),  DateTime.civil(2005, 2, 22, 10, 10, 10).ago(3600)
@@ -248,10 +222,6 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal DateTime.civil(2016, 2, 29), DateTime.civil(2016, 3, 7).last_week
   end
 
-  def test_last_month_on_31st
-    assert_equal DateTime.civil(2004, 2, 29), DateTime.civil(2004, 3, 31).last_month
-  end
-
   def test_last_quarter_on_31st
     assert_equal DateTime.civil(2004, 2, 29), DateTime.civil(2004, 5, 31).last_quarter
   end
diff --git a/activesupport/test/core_ext/load_error_test.rb b/activesupport/test/core_ext/load_error_test.rb
index 4fdd228ff8..41b11d0c33 100644
--- a/activesupport/test/core_ext/load_error_test.rb
+++ b/activesupport/test/core_ext/load_error_test.rb
@@ -5,7 +5,7 @@ require "active_support/core_ext/load_error"
 
 class TestLoadError < ActiveSupport::TestCase
   def test_with_require
-    assert_raise(LoadError) { require 'no_this_file_don\'t_exist' }
+    assert_raise(LoadError) { require "no_this_file_don't_exist" }
   end
   def test_with_load
     assert_raise(LoadError) { load "nor_does_this_one" }
diff --git a/activesupport/test/core_ext/module/reachable_test.rb b/activesupport/test/core_ext/module/reachable_test.rb
index a69fc6839e..097a72fa5b 100644
--- a/activesupport/test/core_ext/module/reachable_test.rb
+++ b/activesupport/test/core_ext/module/reachable_test.rb
@@ -5,13 +5,17 @@ require "active_support/core_ext/module/reachable"
 
 class AnonymousTest < ActiveSupport::TestCase
   test "an anonymous class or module is not reachable" do
-    assert !Module.new.reachable?
-    assert !Class.new.reachable?
+    assert_deprecated do
+      assert !Module.new.reachable?
+      assert !Class.new.reachable?
+    end
   end
 
   test "ordinary named classes or modules are reachable" do
-    assert Kernel.reachable?
-    assert Object.reachable?
+    assert_deprecated do
+      assert Kernel.reachable?
+      assert Object.reachable?
+    end
   end
 
   test "a named class or module whose constant has gone is not reachable" do
@@ -21,8 +25,10 @@ class AnonymousTest < ActiveSupport::TestCase
     self.class.send(:remove_const, :C)
     self.class.send(:remove_const, :M)
 
-    assert !c.reachable?
-    assert !m.reachable?
+    assert_deprecated do
+      assert !c.reachable?
+      assert !m.reachable?
+    end
   end
 
   test "a named class or module whose constants store different objects are not reachable" do
@@ -35,9 +41,11 @@ class AnonymousTest < ActiveSupport::TestCase
     eval "class C; end"
     eval "module M; end"
 
-    assert C.reachable?
-    assert M.reachable?
-    assert !c.reachable?
-    assert !m.reachable?
+    assert_deprecated do
+      assert C.reachable?
+      assert M.reachable?
+      assert !c.reachable?
+      assert !m.reachable?
+    end
   end
 end
diff --git a/activesupport/test/core_ext/module/remove_method_test.rb b/activesupport/test/core_ext/module/remove_method_test.rb
index dbf71b477d..8493be8d08 100644
--- a/activesupport/test/core_ext/module/remove_method_test.rb
+++ b/activesupport/test/core_ext/module/remove_method_test.rb
@@ -6,22 +6,22 @@ require "active_support/core_ext/module/remove_method"
 module RemoveMethodTests
   class A
     def do_something
-      return 1
+      1
     end
 
     def do_something_protected
-      return 1
+      1
     end
     protected :do_something_protected
 
     def do_something_private
-      return 1
+      1
     end
     private :do_something_private
 
     class << self
       def do_something_else
-        return 2
+        2
       end
     end
   end
diff --git a/activesupport/test/core_ext/object/instance_variables_test.rb b/activesupport/test/core_ext/object/instance_variables_test.rb
index b9ec827954..a3d8daab5b 100644
--- a/activesupport/test/core_ext/object/instance_variables_test.rb
+++ b/activesupport/test/core_ext/object/instance_variables_test.rb
@@ -19,7 +19,7 @@ class ObjectInstanceVariableTest < ActiveSupport::TestCase
   end
 
   def test_instance_exec_passes_arguments_to_block
-    assert_equal %w(hello goodbye), "hello".instance_exec("goodbye") { |v| [self, v] }
+    assert_equal %w(hello goodbye), "hello".dup.instance_exec("goodbye") { |v| [self, v] }
   end
 
   def test_instance_exec_with_frozen_obj
@@ -27,7 +27,7 @@ class ObjectInstanceVariableTest < ActiveSupport::TestCase
   end
 
   def test_instance_exec_nested
-    assert_equal %w(goodbye olleh bar), "hello".instance_exec("goodbye") { |arg|
+    assert_equal %w(goodbye olleh bar), "hello".dup.instance_exec("goodbye") { |arg|
       [arg] + instance_exec("bar") { |v| [reverse, v] } }
   end
 end
diff --git a/activesupport/test/core_ext/range_ext_test.rb b/activesupport/test/core_ext/range_ext_test.rb
index a96e3d62e8..049fac8fd4 100644
--- a/activesupport/test/core_ext/range_ext_test.rb
+++ b/activesupport/test/core_ext/range_ext_test.rb
@@ -16,6 +16,11 @@ class RangeTest < ActiveSupport::TestCase
     assert_equal "BETWEEN '2005-12-10 15:30:00' AND '2005-12-10 17:30:00'", date_range.to_s(:db)
   end
 
+  def test_to_s_with_alphabets
+    alphabet_range = ("a".."z")
+    assert_equal "BETWEEN 'a' AND 'z'", alphabet_range.to_s(:db)
+  end
+
   def test_to_s_with_numeric
     number_range = (1..100)
     assert_equal "BETWEEN '1' AND '100'", number_range.to_s(:db)
@@ -116,9 +121,12 @@ class RangeTest < ActiveSupport::TestCase
 
   def test_include_on_time_with_zone
     twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"] , Time.utc(2006, 11, 28, 10, 30))
-    assert_raises TypeError do
-      ((twz - 1.hour)..twz).include?(twz)
-    end
+    assert ((twz - 1.hour)..twz).include?(twz)
+  end
+
+  def test_case_equals_on_time_with_zone
+    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"] , Time.utc(2006, 11, 28, 10, 30))
+    assert ((twz - 1.hour)..twz) === twz
   end
 
   def test_date_time_with_each
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index 9fd6d8ac0f..5c5abe9fd1 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -197,7 +197,7 @@ class StringInflectionsTest < ActiveSupport::TestCase
   end
 
   def test_string_parameterized_underscore_preserve_case
-    StringToParameterizePreserceCaseWithUnderscore.each do |normal, slugged|
+    StringToParameterizePreserveCaseWithUnderscore.each do |normal, slugged|
       assert_equal(slugged, normal.parameterize(separator: "_", preserve_case: true))
     end
   end
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index dc2f4c5ac7..8cb17df01b 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -178,10 +178,6 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Time.local(2005, 2, 4, 19, 30, 59, Rational(999999999, 1000)), Time.local(2005, 2, 4, 19, 30, 10).end_of_minute
   end
 
-  def test_last_year
-    assert_equal Time.local(2004, 6, 5, 10),  Time.local(2005, 6, 5, 10, 0, 0).last_year
-  end
-
   def test_ago
     assert_equal Time.local(2005, 2, 22, 10, 10, 9),  Time.local(2005, 2, 22, 10, 10, 10).ago(1)
     assert_equal Time.local(2005, 2, 22, 9, 10, 10),  Time.local(2005, 2, 22, 10, 10, 10).ago(3600)
@@ -664,10 +660,6 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     end
   end
 
-  def test_last_month_on_31st
-    assert_equal Time.local(2004, 2, 29), Time.local(2004, 3, 31).last_month
-  end
-
   def test_xmlschema_is_available
     assert_nothing_raised { Time.now.xmlschema }
   end
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index 0f80a24758..ab96568956 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -50,6 +50,12 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     assert_raise(ArgumentError) { @twz.in_time_zone(Object.new) }
   end
 
+  def test_in_time_zone_with_ambiguous_time
+    with_env_tz "Europe/Moscow" do
+      assert_equal Time.utc(2014, 10, 25, 22, 0, 0), Time.local(2014, 10, 26, 1, 0, 0).in_time_zone("Moscow")
+    end
+  end
+
   def test_localtime
     assert_equal @twz.localtime, @twz.utc.getlocal
     assert_instance_of Time, @twz.localtime
@@ -1301,4 +1307,10 @@ class TimeWithZoneMethodsForString < ActiveSupport::TestCase
     assert_raise(ArgumentError) { @u.in_time_zone(Object.new) }
     assert_raise(ArgumentError) { @z.in_time_zone(Object.new) }
   end
+
+  def test_in_time_zone_with_ambiguous_time
+    with_tz_default "Moscow" do
+      assert_equal Time.utc(2014, 10, 25, 22, 0, 0), "2014-10-26 01:00:00".in_time_zone
+    end
+  end
 end
diff --git a/activesupport/test/encrypted_configuration_test.rb b/activesupport/test/encrypted_configuration_test.rb
index 53ea9e393f..0bc915be82 100644
--- a/activesupport/test/encrypted_configuration_test.rb
+++ b/activesupport/test/encrypted_configuration_test.rb
@@ -51,15 +51,15 @@ class EncryptedConfigurationTest < ActiveSupport::TestCase
     assert_equal "things", @credentials[:new]
   end
 
+  test "raise error when writing an invalid format value" do
+    assert_raise(Psych::SyntaxError) do
+      @credentials.change do |config_file|
+        config_file.write "login: *login\n  username: dummy"
+      end
+    end
+  end
+
   test "raises key error when accessing config via bang method" do
     assert_raise(KeyError) { @credentials.something! }
   end
-
-  private
-    def new_credentials_configuration
-      ActiveSupport::EncryptedConfiguration.new \
-        config_path: @credentials_config_path,
-        key_path: @credentials_key_path,
-        env_key: "RAILS_MASTER_KEY"
-    end
 end
diff --git a/activesupport/test/hash_with_indifferent_access_test.rb b/activesupport/test/hash_with_indifferent_access_test.rb
index b3788ee65c..41d653fa59 100644
--- a/activesupport/test/hash_with_indifferent_access_test.rb
+++ b/activesupport/test/hash_with_indifferent_access_test.rb
@@ -399,6 +399,36 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
   end
 
+  def test_indifferent_transform_keys
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@strings).transform_keys { |k| k * 2 }
+
+    assert_equal({ "aa" => 1, "bb" => 2 }, hash)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
+  end
+
+  def test_indifferent_transform_keys_bang
+    indifferent_strings = ActiveSupport::HashWithIndifferentAccess.new(@strings)
+    indifferent_strings.transform_keys! { |k| k * 2 }
+
+    assert_equal({ "aa" => 1, "bb" => 2 }, indifferent_strings)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
+  end
+
+  def test_indifferent_transform_values
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@strings).transform_values { |v| v * 2 }
+
+    assert_equal({ "a" => 2, "b" => 4 }, hash)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
+  end
+
+  def test_indifferent_transform_values_bang
+    indifferent_strings = ActiveSupport::HashWithIndifferentAccess.new(@strings)
+    indifferent_strings.transform_values! { |v| v * 2 }
+
+    assert_equal({ "a" => 2, "b" => 4 }, indifferent_strings)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
+  end
+
   def test_indifferent_compact
     hash_contain_nil_value = @strings.merge("z" => nil)
     hash = ActiveSupport::HashWithIndifferentAccess.new(hash_contain_nil_value)
diff --git a/activesupport/test/inflector_test.rb b/activesupport/test/inflector_test.rb
index eeec0ab1a5..0e3e576a70 100644
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -224,6 +224,12 @@ class InflectorTest < ActiveSupport::TestCase
     assert_equal("json_html_api", ActiveSupport::Inflector.underscore("JSONHTMLAPI"))
   end
 
+  def test_acronym_regexp_is_deprecated
+    assert_deprecated do
+      ActiveSupport::Inflector.inflections.acronym_regex
+    end
+  end
+
   def test_underscore
     CamelToUnderscore.each do |camel, underscore|
       assert_equal(underscore, ActiveSupport::Inflector.underscore(camel))
@@ -356,6 +362,19 @@ class InflectorTest < ActiveSupport::TestCase
     assert_equal("Col rpted bugs", ActiveSupport::Inflector.humanize("COL_rpted_bugs"))
   end
 
+  def test_humanize_with_acronyms
+    ActiveSupport::Inflector.inflections do |inflect|
+      inflect.acronym "LAX"
+      inflect.acronym "SFO"
+    end
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("LAX ROUNDTRIP TO SFO"))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("LAX ROUNDTRIP TO SFO", capitalize: false))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("lax roundtrip to sfo"))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("lax roundtrip to sfo", capitalize: false))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("Lax Roundtrip To Sfo"))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("Lax Roundtrip To Sfo", capitalize: false))
+  end
+
   def test_constantize
     run_constantize_tests_on do |string|
       ActiveSupport::Inflector.constantize(string)
diff --git a/activesupport/test/inflector_test_cases.rb b/activesupport/test/inflector_test_cases.rb
index f1214671ce..689370cccf 100644
--- a/activesupport/test/inflector_test_cases.rb
+++ b/activesupport/test/inflector_test_cases.rb
@@ -221,7 +221,7 @@ module InflectorTestCases
     "Test with malformed utf8 \251"       => "test_with_malformed_utf8"
   }
 
-  StringToParameterizePreserceCaseWithUnderscore = {
+  StringToParameterizePreserveCaseWithUnderscore = {
     "Donald E. Knuth"                     => "Donald_E_Knuth",
     "Random text with *(bad)* characters" => "Random_text_with_bad_characters",
     "With-some-dashes"                    => "With-some-dashes",
diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index eafa2e1712..d904f79ccf 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -210,7 +210,7 @@ class TestJSONEncoding < ActiveSupport::TestCase
 
   People = Class.new(BasicObject) do
     include Enumerable
-    def initialize()
+    def initialize
       @people = [
         { name: "John", address: { city: "London", country: "UK" } },
         { name: "Jean", address: { city: "Paris" , country: "France" } }
@@ -454,6 +454,10 @@ EXPECTED
     assert_equal '{"number":null}', NaNNumber.new.to_json
   end
 
+  def test_to_json_works_on_io_objects
+    assert_equal STDOUT.to_s.to_json, STDOUT.to_json
+  end
+
   private
 
     def object_keys(json_object)
diff --git a/activesupport/test/message_encryptor_test.rb b/activesupport/test/message_encryptor_test.rb
index 1fbe655642..9edf07f762 100644
--- a/activesupport/test/message_encryptor_test.rb
+++ b/activesupport/test/message_encryptor_test.rb
@@ -115,6 +115,72 @@ class MessageEncryptorTest < ActiveSupport::TestCase
     assert_equal "Ruby on Rails", encryptor.decrypt_and_verify(encrypted_message)
   end
 
+  def test_rotating_secret
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], cipher: "aes-256-gcm").encrypt_and_sign("old")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+    encryptor.rotate secrets[:old]
+
+    assert_equal "old", encryptor.decrypt_and_verify(old_message)
+  end
+
+  def test_rotating_serializer
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], cipher: "aes-256-gcm", serializer: JSON).
+      encrypt_and_sign(ahoy: :hoy)
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm", serializer: JSON)
+    encryptor.rotate secrets[:old]
+
+    assert_equal({ "ahoy" => "hoy" }, encryptor.decrypt_and_verify(old_message))
+  end
+
+  def test_rotating_aes_cbc_secrets
+    old_encryptor = ActiveSupport::MessageEncryptor.new(secrets[:old], "old sign", cipher: "aes-256-cbc")
+    old_message = old_encryptor.encrypt_and_sign("old")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret)
+    encryptor.rotate secrets[:old], "old sign", cipher: "aes-256-cbc"
+
+    assert_equal "old", encryptor.decrypt_and_verify(old_message)
+  end
+
+  def test_multiple_rotations
+    older_message = ActiveSupport::MessageEncryptor.new(secrets[:older], "older sign").encrypt_and_sign("older")
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], "old sign").encrypt_and_sign("old")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret)
+    encryptor.rotate secrets[:old], "old sign"
+    encryptor.rotate secrets[:older], "older sign"
+
+    assert_equal "new",   encryptor.decrypt_and_verify(encryptor.encrypt_and_sign("new"))
+    assert_equal "old",   encryptor.decrypt_and_verify(old_message)
+    assert_equal "older", encryptor.decrypt_and_verify(older_message)
+  end
+
+  def test_on_rotation_is_called_and_returns_modified_messages
+    older_message = ActiveSupport::MessageEncryptor.new(secrets[:older], "older sign").encrypt_and_sign(encoded: "message")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret)
+    encryptor.rotate secrets[:old]
+    encryptor.rotate secrets[:older], "older sign"
+
+    rotated = false
+    message = encryptor.decrypt_and_verify(older_message, on_rotation: proc { rotated = true })
+
+    assert_equal({ encoded: "message" }, message)
+    assert rotated
+  end
+
+  def test_with_rotated_metadata
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], cipher: "aes-256-gcm").
+      encrypt_and_sign("metadata", purpose: :rotation)
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+    encryptor.rotate secrets[:old]
+
+    assert_equal "metadata", encryptor.decrypt_and_verify(old_message, purpose: :rotation)
+  end
+
   private
     def assert_aead_not_decrypted(encryptor, value)
       assert_raise(ActiveSupport::MessageEncryptor::InvalidMessage) do
@@ -134,6 +200,10 @@ class MessageEncryptorTest < ActiveSupport::TestCase
       end
     end
 
+    def secrets
+      @secrets ||= Hash.new { |h, k| h[k] = SecureRandom.random_bytes(32) }
+    end
+
     def munge(base64_string)
       bits = ::Base64.strict_decode64(base64_string)
       bits.reverse!
diff --git a/activesupport/test/message_verifier_test.rb b/activesupport/test/message_verifier_test.rb
index fbeafca203..05d5c1cbc3 100644
--- a/activesupport/test/message_verifier_test.rb
+++ b/activesupport/test/message_verifier_test.rb
@@ -20,6 +20,7 @@ class MessageVerifierTest < ActiveSupport::TestCase
   def setup
     @verifier = ActiveSupport::MessageVerifier.new("Hey, I'm a secret!")
     @data = { some: "data", now: Time.utc(2010) }
+    @secret = SecureRandom.random_bytes(32)
   end
 
   def test_valid_message
@@ -90,6 +91,51 @@ class MessageVerifierTest < ActiveSupport::TestCase
     signed_message = "BAh7BzoJc29tZUkiCWRhdGEGOgZFVDoIbm93SXU6CVRpbWUNIIAbgAAAAAAHOgtvZmZzZXRpADoJem9uZUkiCFVUQwY7BkY=--d03c52c91dfe4ccc5159417c660461bcce005e96"
     assert_equal @data, @verifier.verify(signed_message)
   end
+
+  def test_rotating_secret
+    old_message = ActiveSupport::MessageVerifier.new("old", digest: "SHA1").generate("old")
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA1")
+    verifier.rotate "old"
+
+    assert_equal "old", verifier.verified(old_message)
+  end
+
+  def test_multiple_rotations
+    old_message   = ActiveSupport::MessageVerifier.new("old", digest: "SHA256").generate("old")
+    older_message = ActiveSupport::MessageVerifier.new("older", digest: "SHA1").generate("older")
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA512")
+    verifier.rotate "old",   digest: "SHA256"
+    verifier.rotate "older", digest: "SHA1"
+
+    assert_equal "new",   verifier.verified(verifier.generate("new"))
+    assert_equal "old",   verifier.verified(old_message)
+    assert_equal "older", verifier.verified(older_message)
+  end
+
+  def test_on_rotation_is_called_and_verified_returns_message
+    older_message = ActiveSupport::MessageVerifier.new("older", digest: "SHA1").generate(encoded: "message")
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA512")
+    verifier.rotate "old",   digest: "SHA256"
+    verifier.rotate "older", digest: "SHA1"
+
+    rotated = false
+    message = verifier.verified(older_message, on_rotation: proc { rotated = true })
+
+    assert_equal({ encoded: "message" }, message)
+    assert rotated
+  end
+
+  def test_rotations_with_metadata
+    old_message = ActiveSupport::MessageVerifier.new("old").generate("old", purpose: :rotation)
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret)
+    verifier.rotate "old"
+
+    assert_equal "old", verifier.verified(old_message, purpose: :rotation)
+  end
 end
 
 class MessageVerifierMetadataTest < ActiveSupport::TestCase
diff --git a/activesupport/test/messages/rotation_configuration_test.rb b/activesupport/test/messages/rotation_configuration_test.rb
new file mode 100644
index 0000000000..2f6824ed21
--- /dev/null
+++ b/activesupport/test/messages/rotation_configuration_test.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/messages/rotation_configuration"
+
+class MessagesRotationConfiguration < ActiveSupport::TestCase
+  def setup
+    @config = ActiveSupport::Messages::RotationConfiguration.new
+  end
+
+  def test_signed_configurations
+    @config.rotate :signed, "older secret", salt: "salt", digest: "SHA1"
+    @config.rotate :signed, "old secret", salt: "salt", digest: "SHA256"
+
+    assert_equal [
+      [ "older secret", salt: "salt", digest: "SHA1" ],
+      [ "old secret", salt: "salt", digest: "SHA256" ] ], @config.signed
+  end
+
+  def test_encrypted_configurations
+    @config.rotate :encrypted, "old raw key", cipher: "aes-256-gcm"
+
+    assert_equal [ [ "old raw key", cipher: "aes-256-gcm" ] ], @config.encrypted
+  end
+end
diff --git a/activesupport/test/ordered_options_test.rb b/activesupport/test/ordered_options_test.rb
index 7f2e774c02..2c67bb02ac 100644
--- a/activesupport/test/ordered_options_test.rb
+++ b/activesupport/test/ordered_options_test.rb
@@ -102,4 +102,17 @@ class OrderedOptionsTest < ActiveSupport::TestCase
     end
     assert_raises(KeyError) { a.non_existing_key! }
   end
+
+  def test_inheritable_options_with_bang
+    a = ActiveSupport::InheritableOptions.new(foo: :bar)
+
+    assert_nothing_raised { a.foo! }
+    assert_equal a.foo, a.foo!
+
+    assert_raises(KeyError) do
+      a.foo = nil
+      a.foo!
+    end
+    assert_raises(KeyError) { a.non_existing_key! }
+  end
 end
diff --git a/activesupport/test/security_utils_test.rb b/activesupport/test/security_utils_test.rb
index efd2bcfa0f..0a607594a2 100644
--- a/activesupport/test/security_utils_test.rb
+++ b/activesupport/test/security_utils_test.rb
@@ -9,8 +9,14 @@ class SecurityUtilsTest < ActiveSupport::TestCase
     assert_not ActiveSupport::SecurityUtils.secure_compare("a", "b")
   end
 
-  def test_variable_size_secure_compare_should_perform_string_comparison
-    assert ActiveSupport::SecurityUtils.variable_size_secure_compare("a", "a")
-    assert_not ActiveSupport::SecurityUtils.variable_size_secure_compare("a", "b")
+  def test_fixed_length_secure_compare_should_perform_string_comparison
+    assert ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "a")
+    assert !ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "b")
+  end
+
+  def test_fixed_length_secure_compare_raise_on_length_mismatch
+    assert_raises(ArgumentError, "string length mismatch.") do
+      ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "ab")
+    end
   end
 end
diff --git a/activesupport/test/test_case_test.rb b/activesupport/test/test_case_test.rb
index 65b1cb4a14..84e4953fe2 100644
--- a/activesupport/test/test_case_test.rb
+++ b/activesupport/test/test_case_test.rb
@@ -87,7 +87,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
 
   def test_expression_is_evaluated_in_the_appropriate_scope
     silence_warnings do
-      local_scope = "foo";
+      local_scope = "foo"
       local_scope = local_scope  # to suppress unused variable warning
       assert_difference("local_scope; @object.num") { @object.increment }
     end
@@ -179,6 +179,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   end
 
   def test_assert_changes_works_with_any_object
+    # Silences: instance variable @new_object not initialized.
     retval = silence_warnings do
       assert_changes :@new_object, from: nil, to: 42 do
         @new_object = 42
@@ -201,7 +202,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   def test_assert_changes_with_to_and_case_operator
     token = nil
 
-    assert_changes -> { token },  to: /\w{32}/ do
+    assert_changes -> { token }, to: /\w{32}/ do
       token = SecureRandom.hex
     end
   end
@@ -236,7 +237,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
       end
     end
 
-    assert_equal "@object.num should not change.\n\"@object.num\" did change to 1.\nExpected: 0\n  Actual: 1", error.message
+    assert_equal "@object.num should not change.\n\"@object.num\" did change to 1", error.message
   end
 end
 
diff --git a/activesupport/test/time_zone_test.rb b/activesupport/test/time_zone_test.rb
index acb0ecd226..405c8f315b 100644
--- a/activesupport/test/time_zone_test.rb
+++ b/activesupport/test/time_zone_test.rb
@@ -32,6 +32,12 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_period_for_local_with_ambigiuous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    period = zone.period_for_local(Time.utc(2015, 1, 1))
+    assert_equal period, zone.period_for_local(Time.utc(2014, 10, 26, 1, 0, 0))
+  end
+
   def test_from_integer_to_map
     assert_instance_of ActiveSupport::TimeZone, ActiveSupport::TimeZone[-28800] # PST
   end
@@ -195,6 +201,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_equal "EDT", twz.zone
   end
 
+  def test_local_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.local(2014, 10, 26, 1, 0, 0)
+  end
+
   def test_at
     zone = ActiveSupport::TimeZone["Eastern Time (US & Canada)"]
     secs = 946684800.0
@@ -303,6 +314,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_iso8601_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.parse("2014-10-26T01:00:00")
+  end
+
   def test_parse
     zone = ActiveSupport::TimeZone["Eastern Time (US & Canada)"]
     twz = zone.parse("1999-12-31 19:00:00")
@@ -412,6 +428,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_equal "argument out of range", exception.message
   end
 
+  def test_parse_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.parse("2014-10-26 01:00:00")
+  end
+
   def test_rfc3339
     zone = ActiveSupport::TimeZone["Eastern Time (US & Canada)"]
     twz = zone.rfc3339("1999-12-31T14:00:00-10:00")
@@ -604,6 +625,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_strptime_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.strptime("2014-10-26 01:00:00", "%Y-%m-%d %H:%M:%S")
+  end
+
   def test_utc_offset_lazy_loaded_from_tzinfo_when_not_passed_in_to_initialize
     tzinfo = TZInfo::Timezone.get("America/New_York")
     zone = ActiveSupport::TimeZone.create(tzinfo.name, nil, tzinfo)
@@ -692,6 +718,13 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_all_uninfluenced_by_time_zone_lookups_delegated_to_tzinfo
+    ActiveSupport::TimeZone.clear
+    galapagos = ActiveSupport::TimeZone["Pacific/Galapagos"]
+    all_zones = ActiveSupport::TimeZone.all
+    assert_not_includes all_zones, galapagos
+  end
+
   def test_index
     assert_nil ActiveSupport::TimeZone["bogus"]
     assert_instance_of ActiveSupport::TimeZone, ActiveSupport::TimeZone["Central Time (US & Canada)"]
diff --git a/ci/phantomjs.js b/ci/phantomjs.js
deleted file mode 100644
index 7a33fb14a3..0000000000
--- a/ci/phantomjs.js
+++ /dev/null
@@ -1,149 +0,0 @@
-/*
- * PhantomJS Runner QUnit Plugin 1.2.0
- *
- * PhantomJS binaries: http://phantomjs.org/download.html
- * Requires PhantomJS 1.6+ (1.7+ recommended)
- *
- * Run with:
- *   phantomjs runner.js [url-of-your-qunit-testsuite]
- *
- * e.g.
- *   phantomjs runner.js http://localhost/qunit/test/index.html
- */
-
-/*global phantom:false, require:false, console:false, window:false, QUnit:false */
-
-(function() {
-	'use strict';
-
-	var url, page, timeout,
-		args = require('system').args;
-
-	// arg[0]: scriptName, args[1...]: arguments
-	if (args.length < 2 || args.length > 3) {
-		console.error('Usage:\n  phantomjs runner.js [url-of-your-qunit-testsuite] [timeout-in-seconds]');
-		phantom.exit(1);
-	}
-
-	url = args[1];
-	page = require('webpage').create();
-	if (args[2] !== undefined) {
-		timeout = parseInt(args[2], 10);
-	}
-
-	// Route `console.log()` calls from within the Page context to the main Phantom context (i.e. current `this`)
-	page.onConsoleMessage = function(msg) {
-		console.log(msg);
-	};
-
-	page.onInitialized = function() {
-		page.evaluate(addLogging);
-	};
-
-	page.onCallback = function(message) {
-		var result,
-			failed;
-
-		if (message) {
-			if (message.name === 'QUnit.done') {
-				result = message.data;
-				failed = !result || !result.total || result.failed;
-
-				if (!result.total) {
-					console.error('No tests were executed. Are you loading tests asynchronously?');
-				}
-
-				phantom.exit(failed ? 1 : 0);
-			}
-		}
-	};
-
-	page.open(url, function(status) {
-		if (status !== 'success') {
-			console.error('Unable to access network: ' + status);
-			phantom.exit(1);
-		} else {
-			// Cannot do this verification with the 'DOMContentLoaded' handler because it
-			// will be too late to attach it if a page does not have any script tags.
-			var qunitMissing = page.evaluate(function() { return (typeof QUnit === 'undefined' || !QUnit); });
-			if (qunitMissing) {
-				console.error('The `QUnit` object is not present on this page.');
-				phantom.exit(1);
-			}
-
-			// Set a timeout on the test running, otherwise tests with async problems will hang forever
-			if (typeof timeout === 'number') {
-				setTimeout(function() {
-					console.error('The specified timeout of ' + timeout + ' seconds has expired. Aborting...');
-					phantom.exit(1);
-				}, timeout * 1000);
-			}
-
-			// Do nothing... the callback mechanism will handle everything!
-		}
-	});
-
-	function addLogging() {
-		window.document.addEventListener('DOMContentLoaded', function() {
-			var currentTestAssertions = [];
-
-			QUnit.log(function(details) {
-				var response;
-
-				// Ignore passing assertions
-				if (details.result) {
-					return;
-				}
-
-				response = details.message || '';
-
-				if (typeof details.expected !== 'undefined') {
-					if (response) {
-						response += ', ';
-					}
-
-					response += 'expected: ' + details.expected + ', but was: ' + details.actual;
-				}
-
-				if (details.source) {
-					response += "\n" + details.source;
-				}
-
-				currentTestAssertions.push('Failed assertion: ' + response);
-			});
-
-			QUnit.testDone(function(result) {
-				var i,
-					len,
-					name = '';
-
-				if (result.module) {
-					name += result.module + ': ';
-				}
-				name += result.name;
-
-				if (result.failed) {
-					console.log('\n' + 'Test failed: ' + name);
-
-					for (i = 0, len = currentTestAssertions.length; i < len; i++) {
-						console.log('    ' + currentTestAssertions[i]);
-					}
-				}
-
-				currentTestAssertions.length = 0;
-			});
-
-			QUnit.done(function(result) {
-				console.log('\n' + 'Took ' + result.runtime +  'ms to run ' + result.total + ' tests. ' + result.passed + ' passed, ' + result.failed + ' failed.');
-
-				if (typeof window.callPhantom === 'function') {
-					window.callPhantom({
-						'name': 'QUnit.done',
-						'data': result
-					});
-				}
-			});
-		}, false);
-	}
-})();
-
diff --git a/ci/qunit-selenium-runner.rb b/ci/qunit-selenium-runner.rb
new file mode 100644
index 0000000000..3a58377d77
--- /dev/null
+++ b/ci/qunit-selenium-runner.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require "qunit/selenium/test_runner"
+require "chromedriver/helper"
+
+driver_options = Selenium::WebDriver::Chrome::Options.new
+driver_options.add_argument("--headless")
+driver_options.add_argument("--disable-gpu")
+
+driver = ::Selenium::WebDriver.for(:chrome, options: driver_options)
+result = QUnit::Selenium::TestRunner.new(driver).open(ARGV[0], timeout: 60)
+driver.quit
+
+puts "Time: #{result.duration} seconds, Total: #{result.assertions[:total]}, Passed: #{result.assertions[:passed]}, Failed: #{result.assertions[:failed]}"
+exit(result.tests[:failed] > 0 ? 1 : 0)
diff --git a/ci/travis.rb b/ci/travis.rb
index b124358789..f521ef3cf6 100755
--- a/ci/travis.rb
+++ b/ci/travis.rb
@@ -135,7 +135,7 @@ class Build
     if activesupport? && !isolated?
       # There is a known issue with the listen tests that causes files to be
       # incorrectly GC'ed even when they are still in-use. The current solution
-      # is to only run them in isolation to avoid randomly failing our test suite.
+      # is to only run them in isolation to avoid random failures of our test suite.
       { "LISTEN" => "0" }
     else
       {}
diff --git a/guides/CHANGELOG.md b/guides/CHANGELOG.md
index d8b122d264..518b6abfb3 100644
--- a/guides/CHANGELOG.md
+++ b/guides/CHANGELOG.md
@@ -1 +1,10 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   No changes.
+
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/guides/CHANGELOG.md) for previous changes.
diff --git a/guides/assets/images/belongs_to.png b/guides/assets/images/belongs_to.png
index 1a9926e578..2b8c1d52ea 100644
--- a/guides/assets/images/belongs_to.png
+++ b/guides/assets/images/belongs_to.png
diff --git a/guides/assets/images/habtm.png b/guides/assets/images/habtm.png
index 41013b743d..7e508cc1a6 100644
--- a/guides/assets/images/habtm.png
+++ b/guides/assets/images/habtm.png
diff --git a/guides/assets/images/has_many.png b/guides/assets/images/has_many.png
index 0d67bea38b..36ccf9f0f6 100644
--- a/guides/assets/images/has_many.png
+++ b/guides/assets/images/has_many.png
diff --git a/guides/assets/images/has_many_through.png b/guides/assets/images/has_many_through.png
index b4da60e1fb..9e9caabd73 100644
--- a/guides/assets/images/has_many_through.png
+++ b/guides/assets/images/has_many_through.png
diff --git a/guides/assets/images/has_one.png b/guides/assets/images/has_one.png
index c70763856a..c29c6b9c59 100644
--- a/guides/assets/images/has_one.png
+++ b/guides/assets/images/has_one.png
diff --git a/guides/assets/images/has_one_through.png b/guides/assets/images/has_one_through.png
index 888a02b775..fdf13286c4 100644
--- a/guides/assets/images/has_one_through.png
+++ b/guides/assets/images/has_one_through.png
diff --git a/guides/assets/images/polymorphic.png b/guides/assets/images/polymorphic.png
index e0a7f6d64a..d630db9e01 100644
--- a/guides/assets/images/polymorphic.png
+++ b/guides/assets/images/polymorphic.png
diff --git a/guides/bug_report_templates/action_controller_gem.rb b/guides/bug_report_templates/action_controller_gem.rb
index 4d8d8db3e5..557b1d7bef 100644
--- a/guides/bug_report_templates/action_controller_gem.rb
+++ b/guides/bug_report_templates/action_controller_gem.rb
@@ -9,6 +9,9 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
   gem "rails", "5.1.0"
 end
@@ -19,7 +22,6 @@ require "action_controller/railtie"
 class TestApp < Rails::Application
   config.root = __dir__
   config.session_store :cookie_store, key: "cookie_store_key"
-  secrets.secret_token    = "secret_token"
   secrets.secret_key_base = "secret_key_base"
 
   config.logger = Logger.new($stdout)
diff --git a/guides/bug_report_templates/action_controller_master.rb b/guides/bug_report_templates/action_controller_master.rb
index 1f862e07da..732cdad259 100644
--- a/guides/bug_report_templates/action_controller_master.rb
+++ b/guides/bug_report_templates/action_controller_master.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "bundler", "< 1.16"
+
 begin
   require "bundler/inline"
 rescue LoadError => e
@@ -9,15 +11,16 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
 end
 
 require "action_controller/railtie"
 
 class TestApp < Rails::Application
   config.root = __dir__
-  secrets.secret_token    = "secret_token"
   secrets.secret_key_base = "secret_key_base"
 
   config.logger = Logger.new($stdout)
diff --git a/guides/bug_report_templates/active_job_gem.rb b/guides/bug_report_templates/active_job_gem.rb
index af777a86ef..013d1f8602 100644
--- a/guides/bug_report_templates/active_job_gem.rb
+++ b/guides/bug_report_templates/active_job_gem.rb
@@ -9,6 +9,9 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
   gem "activejob", "5.1.0"
 end
diff --git a/guides/bug_report_templates/active_job_master.rb b/guides/bug_report_templates/active_job_master.rb
index 39fb3f60a6..c0c67879f3 100644
--- a/guides/bug_report_templates/active_job_master.rb
+++ b/guides/bug_report_templates/active_job_master.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "bundler", "< 1.16"
+
 begin
   require "bundler/inline"
 rescue LoadError => e
@@ -9,8 +11,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
 end
 
 require "active_job"
diff --git a/guides/bug_report_templates/active_record_gem.rb b/guides/bug_report_templates/active_record_gem.rb
index 168e2dcc66..921917fbe9 100644
--- a/guides/bug_report_templates/active_record_gem.rb
+++ b/guides/bug_report_templates/active_record_gem.rb
@@ -9,6 +9,9 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
   gem "activerecord", "5.1.0"
   gem "sqlite3"
diff --git a/guides/bug_report_templates/active_record_master.rb b/guides/bug_report_templates/active_record_master.rb
index cbd2cff2b8..b1c83a51f6 100644
--- a/guides/bug_report_templates/active_record_master.rb
+++ b/guides/bug_report_templates/active_record_master.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "bundler", "< 1.16"
+
 begin
   require "bundler/inline"
 rescue LoadError => e
@@ -9,8 +11,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
   gem "sqlite3"
 end
 
diff --git a/guides/bug_report_templates/active_record_migrations_gem.rb b/guides/bug_report_templates/active_record_migrations_gem.rb
index b931ed0beb..9002b8f428 100644
--- a/guides/bug_report_templates/active_record_migrations_gem.rb
+++ b/guides/bug_report_templates/active_record_migrations_gem.rb
@@ -9,6 +9,9 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
   gem "activerecord", "5.1.0"
   gem "sqlite3"
@@ -34,7 +37,7 @@ end
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[5.0]
+class ChangeAmountToAddScale < ActiveRecord::Migration[5.1]
   def change
     reversible do |dir|
       dir.up do
diff --git a/guides/bug_report_templates/active_record_migrations_master.rb b/guides/bug_report_templates/active_record_migrations_master.rb
index 2c009c0563..0979a42a41 100644
--- a/guides/bug_report_templates/active_record_migrations_master.rb
+++ b/guides/bug_report_templates/active_record_migrations_master.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "bundler", "< 1.16"
+
 begin
   require "bundler/inline"
 rescue LoadError => e
@@ -9,8 +11,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
   gem "sqlite3"
 end
 
@@ -34,7 +38,7 @@ end
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[5.0]
+class ChangeAmountToAddScale < ActiveRecord::Migration[5.2]
   def change
     reversible do |dir|
       dir.up do
diff --git a/guides/bug_report_templates/benchmark.rb b/guides/bug_report_templates/benchmark.rb
index d0f5a634bc..520c5e8bab 100644
--- a/guides/bug_report_templates/benchmark.rb
+++ b/guides/bug_report_templates/benchmark.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "bundler", "< 1.16"
+
 begin
   require "bundler/inline"
 rescue LoadError => e
@@ -9,8 +11,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
   gem "benchmark-ips"
 end
 
diff --git a/guides/bug_report_templates/generic_gem.rb b/guides/bug_report_templates/generic_gem.rb
index c990bda005..60e8322c2a 100644
--- a/guides/bug_report_templates/generic_gem.rb
+++ b/guides/bug_report_templates/generic_gem.rb
@@ -9,6 +9,9 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
   gem "activesupport", "5.1.0"
 end
diff --git a/guides/bug_report_templates/generic_master.rb b/guides/bug_report_templates/generic_master.rb
index 1a9b99b624..f7c9fedf02 100644
--- a/guides/bug_report_templates/generic_master.rb
+++ b/guides/bug_report_templates/generic_master.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+gem "bundler", "< 1.16"
+
 begin
   require "bundler/inline"
 rescue LoadError => e
@@ -9,8 +11,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
 end
 
 require "active_support"
diff --git a/guides/rails_guides/levenshtein.rb b/guides/rails_guides/levenshtein.rb
index bafa6bfe9d..c48af797fa 100644
--- a/guides/rails_guides/levenshtein.rb
+++ b/guides/rails_guides/levenshtein.rb
@@ -38,7 +38,7 @@ module RailsGuides
         d[m] = x
       end
 
-      return x
+      x
     end
   end
 end
diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb
index 1f2fe91ea1..78820a7856 100644
--- a/guides/rails_guides/markdown/renderer.rb
+++ b/guides/rails_guides/markdown/renderer.rb
@@ -75,7 +75,7 @@ HTML
           #
           # It is important that we do not eat more than one newline
           # because formatting may be wrong otherwise. For example,
-          # if a bulleted list follows the first item is not rendered
+          # if a bulleted list follows, the first item is not rendered
           # as a list item, but as a paragraph starting with a plain
           # asterisk.
           body.gsub(/^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:](.*?)(\n(?=\n)|\Z)/m) do
diff --git a/guides/source/2_3_release_notes.md b/guides/source/2_3_release_notes.md
index 3f5a3c7ade..1020f4a8e7 100644
--- a/guides/source/2_3_release_notes.md
+++ b/guides/source/2_3_release_notes.md
@@ -231,7 +231,7 @@ Rails chooses between file, template, and action depending on whether there is a
 
 ### Application Controller Renamed
 
-If you're one of the people who has always been bothered by the special-case naming of `application.rb`, rejoice! It's been reworked to be application_controller.rb in Rails 2.3. In addition, there's a new rake task, `rake rails:update:application_controller` to do this automatically for you - and it will be run as part of the normal `rake rails:update` process.
+If you're one of the people who has always been bothered by the special-case naming of `application.rb`, rejoice! It's been reworked to be `application_controller.rb` in Rails 2.3. In addition, there's a new rake task, `rake rails:update:application_controller` to do this automatically for you - and it will be run as part of the normal `rake rails:update` process.
 
 * More Information:
     * [The Death of Application.rb](http://afreshcup.com/2008/11/17/rails-2x-the-death-of-applicationrb/)
@@ -304,7 +304,7 @@ Rails now keeps a per-request local cache of read from the remote cache stores,
 
 Rails can now provide localized views, depending on the locale that you have set. For example, suppose you have a `Posts` controller with a `show` action. By default, this will render `app/views/posts/show.html.erb`. But if you set `I18n.locale = :da`, it will render `app/views/posts/show.da.html.erb`. If the localized template isn't present, the undecorated version will be used. Rails also includes `I18n#available_locales` and `I18n::SimpleBackend#available_locales`, which return an array of the translations that are available in the current Rails project.
 
-In addition, you can use the same scheme to localize the rescue files in the `public` directory: `public/500.da.html` or `public/404.en.html` work, for example.
+In addition, you can use the same scheme to localize the rescue files in the public directory: `public/500.da.html` or `public/404.en.html` work, for example.
 
 ### Partial Scoping for Translations
 
diff --git a/guides/source/3_2_release_notes.md b/guides/source/3_2_release_notes.md
index 6570b19f97..ae6eb27f35 100644
--- a/guides/source/3_2_release_notes.md
+++ b/guides/source/3_2_release_notes.md
@@ -30,13 +30,13 @@ TIP: Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails.
 
 ### What to update in your apps
 
-* Update your Gemfile to depend on
+* Update your `Gemfile` to depend on
     * `rails = 3.2.0`
     * `sass-rails ~> 3.2.3`
     * `coffee-rails ~> 3.2.1`
     * `uglifier >= 1.0.3`
 
-* Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. You can start replacing these plugins by extracting them as gems and adding them in your Gemfile. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
+* Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. You can start replacing these plugins by extracting them as gems and adding them in your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
 
 * There are a couple of new configuration changes you'd want to add in `config/environments/development.rb`:
 
@@ -156,7 +156,7 @@ Railties
 
     will create indexes for `title` and `author` with the latter being a unique index. Some types such as decimal accept custom options. In the example, `price` will be a decimal column with precision and scale set to 7 and 2 respectively.
 
-* Turn gem has been removed from default Gemfile.
+* Turn gem has been removed from default `Gemfile`.
 
 * Remove old plugin generator `rails generate plugin` in favor of `rails plugin new` command.
 
diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md
index 6f1b75a42b..0921cd1979 100644
--- a/guides/source/4_0_release_notes.md
+++ b/guides/source/4_0_release_notes.md
@@ -66,7 +66,7 @@ Major Features
 * **ActiveRecord session store** ([commit](https://github.com/rails/rails/commit/0ffe19056c8e8b2f9ae9d487b896cad2ce9387ad)) - The ActiveRecord session store is extracted to a separate gem. Storing sessions in SQL is costly. Instead, use cookie sessions, memcache sessions, or a custom session store.
 * **ActiveModel mass assignment protection** ([commit](https://github.com/rails/rails/commit/f8c9a4d3e88181cee644f91e1342bfe896ca64c6)) - Rails 3 mass assignment protection is deprecated. Instead, use strong parameters.
 * **ActiveResource** ([commit](https://github.com/rails/rails/commit/f1637bf2bb00490203503fbd943b73406e043d1d)) - ActiveResource is extracted to a separate gem. ActiveResource was not widely used.
-* **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a Gemfile to manage installed gems.
+* **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a `Gemfile` to manage installed gems.
 
 ### ActionPack
 
diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md
index 6bf65757ec..2c5e665e33 100644
--- a/guides/source/4_1_release_notes.md
+++ b/guides/source/4_1_release_notes.md
@@ -274,7 +274,7 @@ for detailed changes.
 * The [Spring application
   preloader](https://github.com/rails/spring) is now installed
   by default for new applications. It uses the development group of
-  the Gemfile, so will not be installed in
+  the `Gemfile`, so will not be installed in
   production. ([Pull Request](https://github.com/rails/rails/pull/12958))
 
 * `BACKTRACE` environment variable to show unfiltered backtraces for test
diff --git a/guides/source/4_2_release_notes.md b/guides/source/4_2_release_notes.md
index a30bfc458a..7105df5634 100644
--- a/guides/source/4_2_release_notes.md
+++ b/guides/source/4_2_release_notes.md
@@ -179,7 +179,7 @@ change your code to use the explicit form (`render file: "foo/bar"`) instead.
 
 `respond_with` and the corresponding class-level `respond_to` have been moved
 to the [responders](https://github.com/plataformatec/responders) gem. Add
-`gem 'responders', '~> 2.0'` to your Gemfile to use it:
+`gem 'responders', '~> 2.0'` to your `Gemfile` to use it:
 
 ```ruby
 # app/controllers/users_controller.rb
@@ -368,7 +368,7 @@ Please refer to the [Changelog][railties] for detailed changes.
 
 ### Notable changes
 
-*   Introduced `web-console` in the default application Gemfile.
+*   Introduced `web-console` in the default application `Gemfile`.
     ([Pull Request](https://github.com/rails/rails/pull/11667))
 
 *   Added a `required` option to the model generator for associations.
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index 3805fd2a63..656838c6b8 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -775,7 +775,7 @@ Please refer to the [Changelog][active-record] for detailed changes.
 
 *   Added prepared statements support to `mysql2` adapter, for mysql2 0.4.4+,
     Previously this was only supported on the deprecated `mysql` legacy adapter.
-    To enable, set `prepared_statements: true` in config/database.yml.
+    To enable, set `prepared_statements: true` in `config/database.yml`.
     ([Pull Request](https://github.com/rails/rails/pull/23461))
 
 *   Added ability to call `ActionRecord::Relation#update` on relation objects
diff --git a/guides/source/5_1_release_notes.md b/guides/source/5_1_release_notes.md
index fa92b9e5f8..6b9a950a42 100644
--- a/guides/source/5_1_release_notes.md
+++ b/guides/source/5_1_release_notes.md
@@ -350,6 +350,10 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 *   Removed deprecated methods related to controller filters.
     ([Commit](https://github.com/rails/rails/commit/d7be30e8babf5e37a891522869e7b0191b79b757))
+    
+*   Removed deprecated support to `:text` and `:nothing` in `render`.
+    ([Commit](https://github.com/rails/rails/commit/79a5ea9eadb4d43b62afacedc0706cbe88c54496), 
+    [Commit](https://github.com/rails/rails/commit/57e1c99a280bdc1b324936a690350320a1cd8111))
 
 ### Deprecations
 
@@ -602,7 +606,7 @@ Please refer to the [Changelog][active-support] for detailed changes.
     ([Pull Request](https://github.com/rails/rails/pull/28157))
 
 *   Deprecated passing string to `:if` and `:unless` conditional options on `set_callback` and `skip_callback`.
-    ([Commit](https://github.com/rails/rails/commit/0952552)
+    ([Commit](https://github.com/rails/rails/commit/0952552))
 
 ### Notable changes
 
diff --git a/guides/source/5_2_release_notes.md b/guides/source/5_2_release_notes.md
new file mode 100644
index 0000000000..eb361e200a
--- /dev/null
+++ b/guides/source/5_2_release_notes.md
@@ -0,0 +1,210 @@
+**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
+
+Ruby on Rails 5.2 Release Notes
+===============================
+
+Highlights in Rails 5.2:
+
+* Active Storage
+* Redis Cache Store
+* HTTP/2 Early hints support
+* Credentials
+* Default Content Security Policy
+
+These release notes cover only the major changes. To learn about various bug
+fixes and changes, please refer to the change logs or check out the [list of
+commits](https://github.com/rails/rails/commits/5-2-stable) in the main Rails
+repository on GitHub.
+
+--------------------------------------------------------------------------------
+
+Upgrading to Rails 5.2
+----------------------
+
+If you're upgrading an existing application, it's a great idea to have good test
+coverage before going in. You should also first upgrade to Rails 5.1 in case you
+haven't and make sure your application still runs as expected before attempting
+an update to Rails 5.2.
+
+
+Major Features
+--------------
+
+### Active Storage
+
+[README](https://github.com/rails/rails/blob/d3893ec38ec61282c2598b01a298124356d6b35a/activestorage/README.md)
+
+### Redis Cache Store
+
+[Pull Request](https://github.com/rails/rails/pull/31134)
+
+
+### HTTP/2 Early hints support
+
+[Pull Request](https://github.com/rails/rails/pull/30744)
+
+
+### Credentials
+
+[Pull Request](https://github.com/rails/rails/pull/30067)
+
+
+### Default Content Security Policy
+
+[Pull Request](https://github.com/rails/rails/pull/31162)
+
+Incompatibilities
+-----------------
+
+ToDo
+
+Railties
+--------
+
+Please refer to the [Changelog][railties] for detailed changes.
+
+### Removals
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Action Cable
+-----------
+
+Please refer to the [Changelog][action-cable] for detailed changes.
+
+### Notable changes
+
+ToDo
+
+Action Pack
+-----------
+
+Please refer to the [Changelog][action-pack] for detailed changes.
+
+### Removals
+
+ToDo
+
+### Deprecations
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Action View
+-------------
+
+Please refer to the [Changelog][action-view] for detailed changes.
+
+### Removals
+
+ToDo
+
+### Deprecations
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Action Mailer
+-------------
+
+Please refer to the [Changelog][action-mailer] for detailed changes.
+
+### Notable changes
+
+ToDo
+
+Active Record
+-------------
+
+Please refer to the [Changelog][active-record] for detailed changes.
+
+ToDo
+
+### Deprecations
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Active Model
+------------
+
+Please refer to the [Changelog][active-model] for detailed changes.
+
+### Removals
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Active Storage
+--------------
+
+Please refer to the [Changelog][active-support] for detailed changes.
+
+### Notable changes
+
+ToDo
+
+Active Support
+--------------
+
+Please refer to the [Changelog][active-support] for detailed changes.
+
+### Removals
+
+ToDo
+
+### Deprecations
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Active Job
+-----------
+
+Please refer to the [Changelog][active-job] for detailed changes.
+
+### Removals
+
+ToDo
+
+### Notable changes
+
+ToDo
+
+Credits
+-------
+
+See the
+[full list of contributors to Rails](http://contributors.rubyonrails.org/) for
+the many people who spent many hours making Rails, the stable and robust
+framework it is. Kudos to all of them.
+
+[railties]:       https://github.com/rails/rails/blob/5-2-stable/railties/CHANGELOG.md
+[action-pack]:    https://github.com/rails/rails/blob/5-2-stable/actionpack/CHANGELOG.md
+[action-view]:    https://github.com/rails/rails/blob/5-2-stable/actionview/CHANGELOG.md
+[action-mailer]:  https://github.com/rails/rails/blob/5-2-stable/actionmailer/CHANGELOG.md
+[action-cable]:   https://github.com/rails/rails/blob/5-2-stable/actioncable/CHANGELOG.md
+[active-record]:  https://github.com/rails/rails/blob/5-2-stable/activerecord/CHANGELOG.md
+[active-model]:   https://github.com/rails/rails/blob/5-2-stable/activemodel/CHANGELOG.md
+[active-storage]: https://github.com/rails/rails/blob/5-2-stable/activestorage/CHANGELOG.md
+[active-support]: https://github.com/rails/rails/blob/5-2-stable/activesupport/CHANGELOG.md
+[active-job]:     https://github.com/rails/rails/blob/5-2-stable/activejob/CHANGELOG.md
diff --git a/guides/source/_welcome.html.erb b/guides/source/_welcome.html.erb
index 8afec00018..6959f992aa 100644
--- a/guides/source/_welcome.html.erb
+++ b/guides/source/_welcome.html.erb
@@ -16,6 +16,7 @@
 <% end %>
 <p>
 The guides for earlier releases:
+<a href="http://guides.rubyonrails.org/v5.1/">Rails 5.1</a>,
 <a href="http://guides.rubyonrails.org/v5.0/">Rails 5.0</a>,
 <a href="http://guides.rubyonrails.org/v4.2/">Rails 4.2</a>,
 <a href="http://guides.rubyonrails.org/v4.1/">Rails 4.1</a>,
diff --git a/guides/source/action_cable_overview.md b/guides/source/action_cable_overview.md
index 31151e0329..1a86b1fcbb 100644
--- a/guides/source/action_cable_overview.md
+++ b/guides/source/action_cable_overview.md
@@ -1,12 +1,12 @@
 Action Cable Overview
 =====================
 
-In this guide you will learn how Action Cable works and how to use WebSockets to
+In this guide, you will learn how Action Cable works and how to use WebSockets to
 incorporate real-time features into your Rails application.
 
 After reading this guide, you will know:
 
-* What Action Cable is and its integration on backend and frontend
+* What Action Cable is and its integration backend and frontend
 * How to setup Action Cable
 * How to setup channels
 * Deployment and Architecture setup for running Action Cable
@@ -129,7 +129,7 @@ subscriptions based on an identifier sent by the cable consumer.
 # app/channels/chat_channel.rb
 class ChatChannel < ApplicationCable::Channel
   # Called when the consumer has successfully
-  # become a subscriber of this channel.
+  # become a subscriber to this channel.
   def subscribed
   end
 end
@@ -225,7 +225,7 @@ A *broadcasting* is a pub/sub link where anything transmitted by a publisher
 is routed directly to the channel subscribers who are streaming that named
 broadcasting. Each channel can be streaming zero or more broadcastings.
 
-Broadcastings are purely an online queue and time dependent. If a consumer is
+Broadcastings are purely an online queue and time-dependent. If a consumer is
 not streaming (subscribed to a given channel), they'll not get the broadcast
 should they connect later.
 
@@ -515,8 +515,8 @@ user. For a user with an ID of 1, the broadcasting name would be
 The channel has been instructed to stream everything that arrives at
 `web_notifications:1` directly to the client by invoking the `received`
 callback. The data passed as argument is the hash sent as the second parameter
-to the server-side broadcast call, JSON encoded for the trip across the wire,
-and unpacked for the data argument arriving to `received`.
+to the server-side broadcast call, JSON encoded for the trip across the wire
+and unpacked for the data argument arriving as `received`.
 
 ### More Complete Examples
 
@@ -555,9 +555,8 @@ The async adapter is intended for development/testing and should not be used in
 
 ##### Redis Adapter
 
-Action Cable contains two Redis adapters: "normal" Redis and Evented Redis. Both
-of the adapters require users to provide a URL pointing to the Redis server.
-Additionally, a channel_prefix may be provided to avoid channel name collisions
+The Redis adapter requires users to provide a URL pointing to the Redis server.
+Additionally, a `channel_prefix` may be provided to avoid channel name collisions
 when using the same Redis server for multiple applications. See the [Redis PubSub documentation](https://redis.io/topics/pubsub#database-amp-scoping) for more details.
 
 ##### PostgreSQL Adapter
@@ -570,7 +569,7 @@ This may change in the future. [#27214](https://github.com/rails/rails/issues/27
 
 Action Cable will only accept requests from specified origins, which are
 passed to the server config as an array. The origins can be instances of
-strings or regular expressions, against which a check for match will be performed.
+strings or regular expressions, against which a check for the match will be performed.
 
 ```ruby
 config.action_cable.allowed_request_origins = ['http://rubyonrails.com', %r{http://ruby.*}]
@@ -593,7 +592,7 @@ environment configuration files.
 
 ### Other Configurations
 
-The other common option to configure, is the log tags applied to the
+The other common option to configure is the log tags applied to the
 per-connection logger. Here's an example that uses
 the user account id if available, else "no-account" while tagging:
 
@@ -608,7 +607,7 @@ config.action_cable.log_tags = [
 For a full list of all configuration options, see the
 `ActionCable::Server::Configuration` class.
 
-Also note that your server must provide at least the same number of database
+Also, note that your server must provide at least the same number of database
 connections as you have workers. The default worker pool size is set to 4, so
 that means you have to make at least that available. You can change that in
 `config/database.yml` through the `pool` attribute.
@@ -669,8 +668,8 @@ authentication. You can see one way of doing that with Devise in this [article](
 ## Dependencies
 
 Action Cable provides a subscription adapter interface to process its
-pubsub internals. By default, asynchronous, inline, PostgreSQL, evented
-Redis, and non-evented Redis adapters are included. The default adapter
+pubsub internals. By default, asynchronous, inline, PostgreSQL, and Redis
+adapters are included. The default adapter
 in new Rails applications is the asynchronous (`async`) adapter.
 
 The Ruby side of things is built on top of [websocket-driver](https://github.com/faye/websocket-driver-ruby),
diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index 2c3f74c3e1..6ecfb57db3 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -21,7 +21,7 @@ After reading this guide, you will know:
 What Does a Controller Do?
 --------------------------
 
-Action Controller is the C in MVC. After the router has determined which controller to use for a request, the controller is responsible for making sense of the request and producing the appropriate output. Luckily, Action Controller does most of the groundwork for you and uses smart conventions to make this as straightforward as possible.
+Action Controller is the C in [MVC](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). After the router has determined which controller to use for a request, the controller is responsible for making sense of the request, and producing the appropriate output. Luckily, Action Controller does most of the groundwork for you and uses smart conventions to make this as straightforward as possible.
 
 For most conventional [RESTful](https://en.wikipedia.org/wiki/Representational_state_transfer) applications, the controller will receive the request (this is invisible to you as the developer), fetch or save data from a model and use a view to create HTML output. If your controller needs to do things a little differently, that's not a problem, this is just the most common way for a controller to work.
 
@@ -400,9 +400,9 @@ Rails.application.config.session_store :cookie_store, key: '_your_app_session',
 Rails sets up (for the CookieStore) a secret key used for signing the session data in `config/credentials.yml.enc`. This can be changed with `bin/rails credentials:edit`.
 
 ```ruby
-# amazon:
-#  access_key_id: 123
-#  secret_access_key: 345
+# aws:
+#   access_key_id: 123
+#   secret_access_key: 345
 
 # Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
 secret_key_base: 492f...
@@ -654,8 +654,8 @@ class UsersController < ApplicationController
     @users = User.all
     respond_to do |format|
       format.html # index.html.erb
-      format.xml  { render xml: @users}
-      format.json { render json: @users}
+      format.xml  { render xml: @users }
+      format.json { render json: @users }
     end
   end
 end
@@ -784,9 +784,9 @@ The way this is done is to add a non-guessable token which is only known to your
 If you generate a form like this:
 
 ```erb
-<%= form_for @user do |f| %>
-  <%= f.text_field :username %>
-  <%= f.text_field :password %>
+<%= form_with model: @user, local: true do |form| %>
+  <%= form.text_field :username %>
+  <%= form.text_field :password %>
 <% end %>
 ```
 
@@ -1116,7 +1116,7 @@ Rails default exception handling displays a "500 Server Error" message for all e
 
 ### The Default 500 and 404 Templates
 
-By default a production application will render either a 404 or a 500 error message, in the development environment all unhandled exceptions are raised. These messages are contained in static HTML files in the `public` folder, in `404.html` and `500.html` respectively. You can customize these files to add some extra information and style, but remember that they are static HTML; i.e. you can't use ERB, SCSS, CoffeeScript, or layouts for them.
+By default a production application will render either a 404 or a 500 error message, in the development environment all unhandled exceptions are raised. These messages are contained in static HTML files in the public folder, in `404.html` and `500.html` respectively. You can customize these files to add some extra information and style, but remember that they are static HTML; i.e. you can't use ERB, SCSS, CoffeeScript, or layouts for them.
 
 ### `rescue_from`
 
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index 96ef9c4450..cb07781d1c 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -92,8 +92,8 @@ registered email address:
 class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
-  def welcome_email(user)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = 'http://example.com/login'
     mail(to: @user.email, subject: 'Welcome to My Awesome Site')
   end
@@ -176,7 +176,7 @@ $ bin/rails db:migrate
 Now that we have a user model to play with, we will just edit the
 `app/controllers/users_controller.rb` make it instruct the `UserMailer` to deliver
 an email to the newly created user by editing the create action and inserting a
-call to `UserMailer.welcome_email` right after the user is successfully saved.
+call to `UserMailer.with(user: @user).welcome_email` right after the user is successfully saved.
 
 Action Mailer is nicely integrated with Active Job so you can send emails outside
 of the request-response cycle, so the user doesn't have to wait on it:
@@ -191,7 +191,7 @@ class UsersController < ApplicationController
     respond_to do |format|
       if @user.save
         # Tell the UserMailer to send a welcome email after save
-        UserMailer.welcome_email(@user).deliver_later
+        UserMailer.with(user: @user).welcome_email.deliver_later
 
         format.html { redirect_to(@user, notice: 'User was successfully created.') }
         format.json { render json: @user, status: :created, location: @user }
@@ -220,12 +220,17 @@ If you want to send emails right away (from a cronjob for example) just call
 class SendWeeklySummary
   def run
     User.find_each do |user|
-      UserMailer.weekly_summary(user).deliver_now
+      UserMailer.with(user: user).weekly_summary.deliver_now
     end
   end
 end
 ```
 
+Any key value pair passed to `with` just becomes the `params` for the mailer
+action. So `with(user: @user, account: @user.account)` makes `params[:user]` and
+`params[:account]` available in the mailer action. Just like controllers have
+params.
+
 The method `welcome_email` returns an `ActionMailer::MessageDelivery` object which
 can then just be told `deliver_now` or `deliver_later` to send itself out. The
 `ActionMailer::MessageDelivery` object is just a wrapper around a `Mail::Message`. If
@@ -331,7 +336,7 @@ with the addresses separated by commas.
 
 ```ruby
 class AdminMailer < ApplicationMailer
-  default to: Proc.new { Admin.pluck(:email) },
+  default to: -> { Admin.pluck(:email) },
           from: 'notification@example.com'
 
   def new_registration(user)
@@ -351,8 +356,8 @@ address when they receive the email. The trick to doing that is to format the
 email address in the format `"Full Name" <email>`.
 
 ```ruby
-def welcome_email(user)
-  @user = user
+def welcome_email
+  @user = params[:user]
   email_with_name = %("#{@user.name}" <#{@user.email}>)
   mail(to: email_with_name, subject: 'Welcome to My Awesome Site')
 end
@@ -372,8 +377,8 @@ To change the default mailer view for your action you do something like:
 class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
-  def welcome_email(user)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = 'http://example.com/login'
     mail(to: @user.email,
          subject: 'Welcome to My Awesome Site',
@@ -394,8 +399,8 @@ templates or even render inline or text without using a template file:
 class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
-  def welcome_email(user)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = 'http://example.com/login'
     mail(to: @user.email,
          subject: 'Welcome to My Awesome Site') do |format|
@@ -453,8 +458,8 @@ the format block to specify different layouts for different formats:
 
 ```ruby
 class UserMailer < ApplicationMailer
-  def welcome_email(user)
-    mail(to: user.email) do |format|
+  def welcome_email
+    mail(to: params[:user].email) do |format|
       format.html { render layout: 'my_layout' }
       format.text
     end
@@ -477,7 +482,7 @@ special URL that renders them. In the above example, the preview class for
 ```ruby
 class UserMailerPreview < ActionMailer::Preview
   def welcome_email
-    UserMailer.welcome_email(User.first)
+    UserMailer.with(user: User.first).welcome_email
   end
 end
 ```
@@ -594,12 +599,12 @@ mailer action.
 
 ```ruby
 class UserMailer < ApplicationMailer
-  def welcome_email(user, company)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = user_url(@user)
-    delivery_options = { user_name: company.smtp_user,
-                         password: company.smtp_password,
-                         address: company.smtp_host }
+    delivery_options = { user_name: params[:company].smtp_user,
+                         password: params[:company].smtp_password,
+                         address: params[:company].smtp_host }
     mail(to: @user.email,
          subject: "Please see the Terms and Conditions attached",
          delivery_method_options: delivery_options)
@@ -616,9 +621,9 @@ will default to `text/plain` otherwise.
 
 ```ruby
 class UserMailer < ApplicationMailer
-  def welcome_email(user, email_body)
-    mail(to: user.email,
-         body: email_body,
+  def welcome_email
+    mail(to: params[:user].email,
+         body: params[:email_body],
          content_type: "text/html",
          subject: "Already rendered!")
   end
@@ -677,24 +682,43 @@ Action Mailer allows for you to specify a `before_action`, `after_action` and
 * You could use a `before_action` to populate the mail object with defaults,
   delivery_method_options or insert default headers and attachments.
 
+```ruby
+class InvitationsMailer < ApplicationMailer
+  before_action { @inviter, @invitee = params[:inviter], params[:invitee] }
+  before_action { @account = params[:inviter].account }
+
+  default to:       -> { @invitee.email_address },
+          from:     -> { common_address(@inviter) },
+          reply_to: -> { @inviter.email_address_with_name }
+
+  def account_invitation
+    mail subject: "#{@inviter.name} invited you to their Basecamp (#{@account.name})"
+  end
+
+  def project_invitation
+    @project    = params[:project]
+    @summarizer = ProjectInvitationSummarizer.new(@project.bucket)
+
+    mail subject: "#{@inviter.name.familiar} added you to a project in Basecamp (#{@account.name})"
+  end
+end
+```
+
 * You could use an `after_action` to do similar setup as a `before_action` but
   using instance variables set in your mailer action.
 
 ```ruby
 class UserMailer < ApplicationMailer
+  before_action { @business, @user = params[:business], params[:user] }
+
   after_action :set_delivery_options,
                :prevent_delivery_to_guests,
                :set_business_headers
 
-  def feedback_message(business, user)
-    @business = business
-    @user = user
-    mail
+  def feedback_message
   end
 
-  def campaign_message(business, user)
-    @business = business
-    @user = user
+  def campaign_message
   end
 
   private
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index a57623428f..fde2040173 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -149,10 +149,10 @@ end
 
 #### Jbuilder
 [Jbuilder](https://github.com/rails/jbuilder) is a gem that's
-maintained by the Rails team and included in the default Rails Gemfile.
+maintained by the Rails team and included in the default Rails `Gemfile`.
 It's similar to Builder, but is used to generate JSON, instead of XML.
 
-If you don't have it, you can add the following to your Gemfile:
+If you don't have it, you can add the following to your `Gemfile`:
 
 ```ruby
 gem 'jbuilder'
@@ -490,7 +490,7 @@ stylesheet_link_tag "application" # => <link href="/assets/application.css" medi
 
 #### stylesheet_path
 
-Computes the path to a stylesheet asset in the `app/assets/stylesheets` directory. If the source filename has no extension, `.css` will be appended. Full paths from the document root will be passed through. Used internally by stylesheet_link_tag to build the stylesheet path.
+Computes the path to a stylesheet asset in the `app/assets/stylesheets` directory. If the source filename has no extension, `.css` will be appended. Full paths from the document root will be passed through. Used internally by `stylesheet_link_tag` to build the stylesheet path.
 
 ```ruby
 stylesheet_path "application" # => /assets/application.css
@@ -1160,7 +1160,7 @@ Returns a string of option tags for pretty much any time zone in the world.
 Returns select and option tags for the given object and method, using `time_zone_options_for_select` to generate the list of option tags.
 
 ```ruby
-time_zone_select( "user", "time_zone")
+time_zone_select("user", "time_zone")
 ```
 
 #### date_field
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index 7a3ff12b63..914ef2c327 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -389,6 +389,25 @@ class GuestsCleanupJob < ApplicationJob
 end
 ```
 
+### Retrying or Discarding failed jobs
+
+It's also possible to retry or discard a job if an exception is raised during execution.
+For example:
+
+```ruby
+class RemoteServiceJob < ApplicationJob
+  retry_on CustomAppException # defaults to 3s wait, 5 attempts
+
+  discard_on ActiveJob::DeserializationError
+
+  def perform(*args)
+    # Might raise CustomAppException or ActiveJob::DeserializationError
+  end
+end
+```
+
+To get more details see the API Documentation for [ActiveJob::Exceptions](http://api.rubyonrails.org/classes/ActiveJob/Exceptions/ClassMethods.html).
+
 ### Deserialization
 
 GlobalID allows serializing full Active Record objects passed to `#perform`.
diff --git a/guides/source/active_model_basics.md b/guides/source/active_model_basics.md
index b8f076a27b..ee0472621b 100644
--- a/guides/source/active_model_basics.md
+++ b/guides/source/active_model_basics.md
@@ -464,7 +464,7 @@ a `password` accessor with certain validations on it.
 #### Requirements
 
 `ActiveModel::SecurePassword` depends on [`bcrypt`](https://github.com/codahale/bcrypt-ruby 'BCrypt'),
-so include this gem in your Gemfile to use `ActiveModel::SecurePassword` correctly.
+so include this gem in your `Gemfile` to use `ActiveModel::SecurePassword` correctly.
 In order to make this work, the model must have an accessor named `password_digest`.
 The `has_secure_password` will add the following validations on the `password` accessor:
 
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index 11aefcb05f..069a624984 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -304,6 +304,17 @@ user = User.find_by(name: 'David')
 user.destroy
 ```
 
+If you'd like to delete several records in bulk, you may use `destroy_all`
+method:
+
+```ruby
+# find and delete all users named David
+User.where(name: 'David').destroy_all
+
+# delete all users
+User.destroy_all
+```
+
 Validations
 -----------
 
diff --git a/guides/source/active_record_callbacks.md b/guides/source/active_record_callbacks.md
index 53417f012e..630dafe632 100644
--- a/guides/source/active_record_callbacks.md
+++ b/guides/source/active_record_callbacks.md
@@ -213,6 +213,7 @@ The following methods trigger callbacks:
 * `save!`
 * `save(validate: false)`
 * `toggle!`
+* `touch`
 * `update_attribute`
 * `update`
 * `update!`
@@ -245,7 +246,6 @@ Just as with validations, it is also possible to skip callbacks by using the fol
 * `increment`
 * `increment_counter`
 * `toggle`
-* `touch`
 * `update_column`
 * `update_columns`
 * `update_all`
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 678b80516f..4e28e31a53 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -414,7 +414,7 @@ end
 `find_in_batches` works on model classes, as seen above, and also on relations:
 
 ```ruby
-Invoice.pending.find_in_batches do |invoice|
+Invoice.pending.find_in_batches do |invoices|
   pending_invoices_export.add_invoices(invoices)
 end
 ```
@@ -801,7 +801,7 @@ The SQL that would be executed:
 SELECT * FROM articles WHERE id > 10 ORDER BY id DESC
 
 # Original query without `only`
-SELECT "articles".* FROM "articles" WHERE (id > 10) ORDER BY id desc LIMIT 20
+SELECT * FROM articles WHERE id > 10 ORDER BY id DESC LIMIT 20
 
 ```
 
@@ -820,14 +820,14 @@ Article.find(10).comments.reorder('name')
 The SQL that would be executed:
 
 ```sql
-SELECT * FROM articles WHERE id = 10
+SELECT * FROM articles WHERE id = 10 LIMIT 1
 SELECT * FROM comments WHERE article_id = 10 ORDER BY name
 ```
 
 In the case where the `reorder` clause is not used, the SQL executed would be:
 
 ```sql
-SELECT * FROM articles WHERE id = 10
+SELECT * FROM articles WHERE id = 10 LIMIT 1
 SELECT * FROM comments WHERE article_id = 10 ORDER BY posted_at DESC
 ```
 
@@ -1091,7 +1091,7 @@ This produces:
 
 ```sql
 SELECT articles.* FROM articles
-  INNER JOIN categories ON articles.category_id = categories.id
+  INNER JOIN categories ON categories.id = articles.category_id
   INNER JOIN comments ON comments.article_id = articles.id
 ```
 
@@ -1712,10 +1712,10 @@ Client.find_by_sql("SELECT * FROM clients
 
 ### `select_all`
 
-`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve objects from the database using custom SQL just like `find_by_sql` but will not instantiate them. Instead, you will get an array of hashes where each hash indicates a record.
+`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve objects from the database using custom SQL just like `find_by_sql` but will not instantiate them. This method will return an instance of `ActiveRecord::Result` class and calling `to_hash` on this object would return you an array of hashes where each hash indicates a record.
 
 ```ruby
-Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'")
+Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'").to_hash
 # => [
 #   {"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"},
 #   {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"}
@@ -1871,14 +1871,14 @@ All calculation methods work directly on a model:
 
 ```ruby
 Client.count
-# SELECT count(*) AS count_all FROM clients
+# SELECT COUNT(*) FROM clients
 ```
 
 Or on a relation:
 
 ```ruby
 Client.where(first_name: 'Ryan').count
-# SELECT count(*) AS count_all FROM clients WHERE (first_name = 'Ryan')
+# SELECT COUNT(*) FROM clients WHERE (first_name = 'Ryan')
 ```
 
 You can also use various finder methods on a relation for performing complex calculations:
@@ -1890,9 +1890,9 @@ Client.includes("orders").where(first_name: 'Ryan', orders: { status: 'received'
 Which will execute:
 
 ```sql
-SELECT count(DISTINCT clients.id) AS count_all FROM clients
-  LEFT OUTER JOIN orders ON orders.client_id = clients.id WHERE
-  (clients.first_name = 'Ryan' AND orders.status = 'received')
+SELECT COUNT(DISTINCT clients.id) FROM clients
+  LEFT OUTER JOIN orders ON orders.client_id = clients.id
+  WHERE (clients.first_name = 'Ryan' AND orders.status = 'received')
 ```
 
 ### Count
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 1438245f9c..66d2fbd939 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -674,44 +674,6 @@ M.parents       # => [X::Y, X, Object]
 
 NOTE: Defined in `active_support/core_ext/module/introspection.rb`.
 
-### Reachable
-
-A named module is reachable if it is stored in its corresponding constant. It means you can reach the module object via the constant.
-
-That is what ordinarily happens, if a module is called "M", the `M` constant exists and holds it:
-
-```ruby
-module M
-end
-
-M.reachable? # => true
-```
-
-But since constants and modules are indeed kind of decoupled, module objects can become unreachable:
-
-```ruby
-module M
-end
-
-orphan = Object.send(:remove_const, :M)
-
-# The module object is orphan now but it still has a name.
-orphan.name # => "M"
-
-# You cannot reach it via the constant M because it does not even exist.
-orphan.reachable? # => false
-
-# Let's define a module called "M" again.
-module M
-end
-
-# The constant M exists now again, and it stores a module
-# object called "M", but it is a new instance.
-orphan.reachable? # => false
-```
-
-NOTE: Defined in `active_support/core_ext/module/reachable.rb`.
-
 ### Anonymous
 
 A module may or may not have a name:
@@ -745,7 +707,6 @@ end
 
 m = Object.send(:remove_const, :M)
 
-m.reachable? # => false
 m.anonymous? # => false
 ```
 
@@ -1791,7 +1752,7 @@ The methods `to_date`, `to_time`, and `to_datetime` are basically convenience wr
 "2010-07-27 23:42:00".to_time(:local) # => 2010-07-27 23:42:00 +0200
 ```
 
-Default is `:utc`.
+Default is `:local`.
 
 Please refer to the documentation of `Date._parse` for further details.
 
@@ -1835,7 +1796,7 @@ NOTE: Defined in `active_support/core_ext/numeric/bytes.rb`.
 
 ### Time
 
-Enables the use of time calculations and declarations, like `45.minutes + 2.hours + 4.years`.
+Enables the use of time calculations and declarations, like `45.minutes + 2.hours + 4.weeks`.
 
 These methods use Time#advance for precise date calculations when using from_now, ago, etc.
 as well as adding or subtracting their results from a Time object. For example:
@@ -1844,13 +1805,15 @@ as well as adding or subtracting their results from a Time object. For example:
 # equivalent to Time.current.advance(months: 1)
 1.month.from_now
 
-# equivalent to Time.current.advance(years: 2)
-2.years.from_now
+# equivalent to Time.current.advance(weeks: 2)
+2.weeks.from_now
 
-# equivalent to Time.current.advance(months: 4, years: 5)
-(4.months + 5.years).from_now
+# equivalent to Time.current.advance(months: 4, weeks: 5)
+(4.months + 5.weeks).from_now
 ```
 
+WARNING. For other durations please refer to the time extensions to `Integer`.
+
 NOTE: Defined in `active_support/core_ext/numeric/time.rb`.
 
 ### Formatting
@@ -1986,6 +1949,28 @@ The method `ordinalize` returns the ordinal string corresponding to the receiver
 
 NOTE: Defined in `active_support/core_ext/integer/inflections.rb`.
 
+### Time
+
+Enables the use of time calculations and declarations, like `4.months + 5.years`.
+
+These methods use Time#advance for precise date calculations when using from_now, ago, etc.
+as well as adding or subtracting their results from a Time object. For example:
+
+```ruby
+# equivalent to Time.current.advance(months: 1)
+1.month.from_now
+
+# equivalent to Time.current.advance(years: 2)
+2.years.from_now
+
+# equivalent to Time.current.advance(months: 4, years: 5)
+(4.months + 5.years).from_now
+```
+
+WARNING. For other durations please refer to the time extensions to `Numeric`.
+
+NOTE: Defined in `active_support/core_ext/integer/time.rb`.
+
 Extensions to `BigDecimal`
 --------------------------
 ### `to_s`
@@ -2985,6 +2970,32 @@ Extensions to `Date`
 
 NOTE: All the following methods are defined in `active_support/core_ext/date/calculations.rb`.
 
+```ruby
+yesterday
+tomorrow
+beginning_of_week (at_beginning_of_week)
+end_of_week (at_end_of_week)
+monday
+sunday
+weeks_ago
+prev_week (last_week)
+next_week
+months_ago
+months_since
+beginning_of_month (at_beginning_of_month)
+end_of_month (at_end_of_month)
+last_month
+beginning_of_quarter (at_beginning_of_quarter)
+end_of_quarter (at_end_of_quarter)
+beginning_of_year (at_beginning_of_year)
+end_of_year (at_end_of_year)
+years_ago
+years_since
+last_year
+on_weekday?
+on_weekend?
+```
+
 INFO: The following calculation methods have edge cases in October 1582, since days 5..14 just do not exist. This guide does not document their behavior around those days for brevity, but it is enough to say that they do what you would expect. That is, `Date.new(1582, 10, 4).tomorrow` returns `Date.new(1582, 10, 15)` and so on. Please check `test/core_ext/date_ext_test.rb` in the Active Support test suite for expected behavior.
 
 #### `Date.current`
@@ -2995,68 +3006,6 @@ When making Date comparisons using methods which honor the user time zone, make
 
 #### Named dates
 
-##### `prev_year`, `next_year`
-
-In Ruby 1.9 `prev_year` and `next_year` return a date with the same day/month in the last or next year:
-
-```ruby
-d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
-d.prev_year              # => Fri, 08 May 2009
-d.next_year              # => Sun, 08 May 2011
-```
-
-If date is the 29th of February of a leap year, you obtain the 28th:
-
-```ruby
-d = Date.new(2000, 2, 29) # => Tue, 29 Feb 2000
-d.prev_year               # => Sun, 28 Feb 1999
-d.next_year               # => Wed, 28 Feb 2001
-```
-
-`prev_year` is aliased to `last_year`.
-
-##### `prev_month`, `next_month`
-
-In Ruby 1.9 `prev_month` and `next_month` return the date with the same day in the last or next month:
-
-```ruby
-d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
-d.prev_month             # => Thu, 08 Apr 2010
-d.next_month             # => Tue, 08 Jun 2010
-```
-
-If such a day does not exist, the last day of the corresponding month is returned:
-
-```ruby
-Date.new(2000, 5, 31).prev_month # => Sun, 30 Apr 2000
-Date.new(2000, 3, 31).prev_month # => Tue, 29 Feb 2000
-Date.new(2000, 5, 31).next_month # => Fri, 30 Jun 2000
-Date.new(2000, 1, 31).next_month # => Tue, 29 Feb 2000
-```
-
-`prev_month` is aliased to `last_month`.
-
-##### `prev_quarter`, `next_quarter`
-
-Same as `prev_month` and `next_month`. It returns the date with the same day in the previous or next quarter:
-
-```ruby
-t = Time.local(2010, 5, 8) # => Sat, 08 May 2010
-t.prev_quarter             # => Mon, 08 Feb 2010
-t.next_quarter             # => Sun, 08 Aug 2010
-```
-
-If such a day does not exist, the last day of the corresponding month is returned:
-
-```ruby
-Time.local(2000, 7, 31).prev_quarter  # => Sun, 30 Apr 2000
-Time.local(2000, 5, 31).prev_quarter  # => Tue, 29 Feb 2000
-Time.local(2000, 10, 31).prev_quarter # => Mon, 30 Oct 2000
-Time.local(2000, 11, 31).next_quarter # => Wed, 28 Feb 2001
-```
-
-`prev_quarter` is aliased to `last_quarter`.
-
 ##### `beginning_of_week`, `end_of_week`
 
 The methods `beginning_of_week` and `end_of_week` return the dates for the
@@ -3174,6 +3123,8 @@ Date.new(2012, 2, 29).years_ago(3)     # => Sat, 28 Feb 2009
 Date.new(2012, 2, 29).years_since(3)   # => Sat, 28 Feb 2015
 ```
 
+`last_year` is short-hand for `#years_ago(1)`.
+
 ##### `months_ago`, `months_since`
 
 The methods `months_ago` and `months_since` work analogously for months:
@@ -3190,6 +3141,8 @@ Date.new(2010, 4, 30).months_ago(2)    # => Sun, 28 Feb 2010
 Date.new(2009, 12, 31).months_since(2) # => Sun, 28 Feb 2010
 ```
 
+`last_month` is short-hand for `#months_ago(1)`.
+
 ##### `weeks_ago`
 
 The method `weeks_ago` works analogously for weeks:
@@ -3352,35 +3305,7 @@ WARNING: `DateTime` is not aware of DST rules and so some of these methods have
 
 NOTE: All the following methods are defined in `active_support/core_ext/date_time/calculations.rb`.
 
-The class `DateTime` is a subclass of `Date` so by loading `active_support/core_ext/date/calculations.rb` you inherit these methods and their aliases, except that they will always return datetimes:
-
-```ruby
-yesterday
-tomorrow
-beginning_of_week (at_beginning_of_week)
-end_of_week (at_end_of_week)
-monday
-sunday
-weeks_ago
-prev_week (last_week)
-next_week
-months_ago
-months_since
-beginning_of_month (at_beginning_of_month)
-end_of_month (at_end_of_month)
-prev_month (last_month)
-next_month
-beginning_of_quarter (at_beginning_of_quarter)
-end_of_quarter (at_end_of_quarter)
-beginning_of_year (at_beginning_of_year)
-end_of_year (at_end_of_year)
-years_ago
-years_since
-prev_year (last_year)
-next_year
-on_weekday?
-on_weekend?
-```
+The class `DateTime` is a subclass of `Date` so by loading `active_support/core_ext/date/calculations.rb` you inherit these methods and their aliases, except that they will always return datetimes.
 
 The following methods are reimplemented so you do **not** need to load `active_support/core_ext/date/calculations.rb` for these ones:
 
@@ -3528,8 +3453,6 @@ Extensions to `Time`
 
 NOTE: All the following methods are defined in `active_support/core_ext/time/calculations.rb`.
 
-Active Support adds to `Time` many of the methods available for `DateTime`:
-
 ```ruby
 past?
 today?
@@ -3541,6 +3464,8 @@ change
 advance
 ago
 since (in)
+prev_day
+next_day
 beginning_of_day (midnight, at_midnight, at_beginning_of_day)
 end_of_day
 beginning_of_hour (at_beginning_of_hour)
@@ -3556,15 +3481,17 @@ months_ago
 months_since
 beginning_of_month (at_beginning_of_month)
 end_of_month (at_end_of_month)
-prev_month (last_month)
+prev_month
 next_month
+last_month
 beginning_of_quarter (at_beginning_of_quarter)
 end_of_quarter (at_end_of_quarter)
 beginning_of_year (at_beginning_of_year)
 end_of_year (at_end_of_year)
 years_ago
 years_since
-prev_year (last_year)
+prev_year
+last_year
 next_year
 on_weekday?
 on_weekend?
@@ -3622,6 +3549,74 @@ now.all_year
 # => Fri, 01 Jan 2010 00:00:00 UTC +00:00..Fri, 31 Dec 2010 23:59:59 UTC +00:00
 ```
 
+#### `prev_day`, `next_day`
+
+In Ruby 1.9 `prev_day` and `next_day` return the date in the last or next day:
+
+```ruby
+d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
+d.prev_day               # => Fri, 07 May 2010
+d.next_day               # => Sun, 09 May 2010
+```
+
+#### `prev_month`, `next_month`
+
+In Ruby 1.9 `prev_month` and `next_month` return the date with the same day in the last or next month:
+
+```ruby
+d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
+d.prev_month             # => Thu, 08 Apr 2010
+d.next_month             # => Tue, 08 Jun 2010
+```
+
+If such a day does not exist, the last day of the corresponding month is returned:
+
+```ruby
+Date.new(2000, 5, 31).prev_month # => Sun, 30 Apr 2000
+Date.new(2000, 3, 31).prev_month # => Tue, 29 Feb 2000
+Date.new(2000, 5, 31).next_month # => Fri, 30 Jun 2000
+Date.new(2000, 1, 31).next_month # => Tue, 29 Feb 2000
+```
+
+#### `prev_year`, `next_year`
+
+In Ruby 1.9 `prev_year` and `next_year` return a date with the same day/month in the last or next year:
+
+```ruby
+d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
+d.prev_year              # => Fri, 08 May 2009
+d.next_year              # => Sun, 08 May 2011
+```
+
+If date is the 29th of February of a leap year, you obtain the 28th:
+
+```ruby
+d = Date.new(2000, 2, 29) # => Tue, 29 Feb 2000
+d.prev_year               # => Sun, 28 Feb 1999
+d.next_year               # => Wed, 28 Feb 2001
+```
+
+#### `prev_quarter`, `next_quarter`
+
+`prev_quarter` and `next_quarter` return the date with the same day in the previous or next quarter:
+
+```ruby
+t = Time.local(2010, 5, 8) # => 2010-05-08 00:00:00 +0300
+t.prev_quarter             # => 2010-02-08 00:00:00 +0200
+t.next_quarter             # => 2010-08-08 00:00:00 +0300
+```
+
+If such a day does not exist, the last day of the corresponding month is returned:
+
+```ruby
+Time.local(2000, 7, 31).prev_quarter  # => 2000-04-30 00:00:00 +0300
+Time.local(2000, 5, 31).prev_quarter  # => 2000-02-29 00:00:00 +0200
+Time.local(2000, 10, 31).prev_quarter # => 2000-07-31 00:00:00 +0300
+Time.local(2000, 11, 31).next_quarter # => 2001-03-01 00:00:00 +0200
+```
+
+`prev_quarter` is aliased to `last_quarter`.
+
 ### Time Constructors
 
 Active Support defines `Time.current` to be `Time.zone.now` if there's a user time zone defined, with fallback to `Time.now`:
diff --git a/guides/source/active_support_instrumentation.md b/guides/source/active_support_instrumentation.md
index 03c9183eb3..25f78fd940 100644
--- a/guides/source/active_support_instrumentation.md
+++ b/guides/source/active_support_instrumentation.md
@@ -197,6 +197,12 @@ INFO. Additional keys may be added by the caller.
 }
 ```
 
+### unpermitted_parameters.action_controller
+
+| Key     | Value            |
+| ------- | ---------------- |
+| `:keys` | Unpermitted keys |
+
 Action View
 -----------
 
@@ -304,7 +310,7 @@ Action Mailer
   mailer: "Notification",
   message_id: "4f5b5491f1774_181b23fc3d4434d38138e5@mba.local.mail",
   subject: "Rails Guides",
-  to: ["users@rails.com", "ddh@rails.com"],
+  to: ["users@rails.com", "dhh@rails.com"],
   from: ["me@rails.com"],
   date: Sat, 10 Mar 2012 14:18:09 +0100,
   mail: "..." # omitted for brevity
@@ -330,13 +336,29 @@ Action Mailer
   mailer: "Notification",
   message_id: "4f5b5491f1774_181b23fc3d4434d38138e5@mba.local.mail",
   subject: "Rails Guides",
-  to: ["users@rails.com", "ddh@rails.com"],
+  to: ["users@rails.com", "dhh@rails.com"],
   from: ["me@rails.com"],
   date: Sat, 10 Mar 2012 14:18:09 +0100,
   mail: "..." # omitted for brevity
 }
 ```
 
+### process.action_mailer
+
+| Key           | Value                    |
+| ------------- | ------------------------ |
+| `:mailer`     | Name of the mailer class |
+| `:action`     | The action               |
+| `:args`       | The arguments            |
+
+```ruby
+{
+  mailer: "Notification",
+  action: "welcome_email",
+  args: []
+}
+```
+
 Active Support
 --------------
 
@@ -450,6 +472,92 @@ Active Job
 | `:adapter`   | QueueAdapter object processing the job |
 | `:job`       | Job object                             |
 
+Action Cable
+------------
+
+### perform_action.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+| `:action`        | The action                |
+| `:data`          | A hash of data            |
+
+### transmit.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+| `:data`          | A hash of data            |
+| `:via`           | Via                       |
+
+### transmit_subscription_confirmation.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+
+### transmit_subscription_rejection.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+
+### broadcast.action_cable
+
+| Key             | Value                |
+| --------------- | -------------------- |
+| `:broadcasting` | A named broadcasting |
+| `:message`      | A hash of message    |
+| `:coder`        | The coder            |
+
+Active Storage
+--------------
+
+### service_upload.active_storage
+
+| Key          | Value                        |
+| ------------ | ---------------------------- |
+| `:key`       | Secure token                 |
+| `:service`   | Name of the service          |
+| `:checksum`  | Checksum to ensure integrity |
+
+### service_streaming_download.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+
+### service_download.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+
+### service_delete.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+
+### service_exist.active_storage
+
+| Key          | Value                       |
+| ------------ | --------------------------- |
+| `:key`       | Secure token                |
+| `:service`   | Name of the service         |
+| `:exist`     | File or blob exists or not  |
+
+### service_url.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+| `:url`       | Generated url       |
 
 Railties
 --------
@@ -549,4 +657,4 @@ end
 ```
 
 You should follow Rails conventions when defining your own events. The format is: `event.library`.
-If you application is sending Tweets, you should create an event named `tweet.twitter`.
+If your application is sending Tweets, you should create an event named `tweet.twitter`.
diff --git a/guides/source/api_app.md b/guides/source/api_app.md
index da1b7b25ef..b360f270d7 100644
--- a/guides/source/api_app.md
+++ b/guides/source/api_app.md
@@ -216,7 +216,6 @@ An API application comes with the following middleware by default:
 - `Rack::Head`
 - `Rack::ConditionalGet`
 - `Rack::ETag`
-- `MyApi::Application::Routes`
 
 See the [internal middleware](rails_on_rack.html#internal-middleware-stack)
 section of the Rack guide for further information on them.
@@ -415,8 +414,10 @@ Some common modules you might want to add:
 
 - `AbstractController::Translation`: Support for the `l` and `t` localization
   and translation methods.
-- `ActionController::HttpAuthentication::Basic` (or `Digest` or `Token`): Support
-  for basic, digest or token HTTP authentication.
+- Support for basic, digest or token HTTP authentication:
+  * `ActionController::HttpAuthentication::Basic::ControllerMethods`,
+  * `ActionController::HttpAuthentication::Digest::ControllerMethods`,
+  * `ActionController::HttpAuthentication::Token::ControllerMethods`
 - `ActionView::Layouts`: Support for layouts when rendering.
 - `ActionController::MimeResponds`: Support for `respond_to`.
 - `ActionController::Cookies`: Support for `cookies`, which includes
diff --git a/guides/source/api_documentation_guidelines.md b/guides/source/api_documentation_guidelines.md
index 2c153d3783..10b89433e7 100644
--- a/guides/source/api_documentation_guidelines.md
+++ b/guides/source/api_documentation_guidelines.md
@@ -16,7 +16,7 @@ RDoc
 ----
 
 The [Rails API documentation](http://api.rubyonrails.org) is generated with
-[RDoc](http://docs.seattlerb.org/rdoc/). To generate it, make sure you are
+[RDoc](https://ruby.github.io/rdoc/). To generate it, make sure you are
 in the rails root directory, run `bundle install` and execute:
 
 ```bash
@@ -26,9 +26,9 @@ in the rails root directory, run `bundle install` and execute:
 Resulting HTML files can be found in the ./doc/rdoc directory.
 
 Please consult the RDoc documentation for help with the
-[markup](http://docs.seattlerb.org/rdoc/RDoc/Markup.html),
+[markup](https://ruby.github.io/rdoc/RDoc/Markup.html),
 and also take into account these [additional
-directives](http://docs.seattlerb.org/rdoc/RDoc/Parser/Ruby.html).
+directives](https://ruby.github.io/rdoc/RDoc/Parser/Ruby.html).
 
 Wording
 -------
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index 17ab9c7600..e6d5aed135 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -35,7 +35,7 @@ rails new appname --skip-sprockets
 ```
 
 Rails automatically adds the `sass-rails`, `coffee-rails` and `uglifier`
-gems to your Gemfile, which are used by Sprockets for asset compression:
+gems to your `Gemfile`, which are used by Sprockets for asset compression:
 
 ```ruby
 gem 'sass-rails'
@@ -44,8 +44,8 @@ gem 'coffee-rails'
 ```
 
 Using the `--skip-sprockets` option will prevent Rails from adding
-them to your Gemfile, so if you later want to enable
-the asset pipeline you will have to add those gems to your Gemfile. Also,
+them to your `Gemfile`, so if you later want to enable
+the asset pipeline you will have to add those gems to your `Gemfile`. Also,
 creating an application with the `--skip-sprockets` option will generate
 a slightly different `config/application.rb` file, with a require statement
 for the sprockets railtie that is commented-out. You will have to remove
@@ -65,7 +65,7 @@ config.assets.js_compressor = :uglifier
 ```
 
 NOTE: The `sass-rails` gem is automatically used for CSS compression if included
-in the Gemfile and no `config.assets.css_compressor` option is set.
+in the `Gemfile` and no `config.assets.css_compressor` option is set.
 
 
 ### Main Features
@@ -154,7 +154,7 @@ environments. You can enable or disable it in your configuration through the
 
 More reading:
 
-* [Optimize caching](http://code.google.com/speed/page-speed/docs/caching.html)
+* [Optimize caching](https://developers.google.com/speed/docs/insights/LeverageBrowserCaching)
 * [Revving Filenames: don't use querystring](http://www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/)
 
 
@@ -181,7 +181,7 @@ When you generate a scaffold or a controller, Rails also generates a JavaScript
 file (or CoffeeScript file if the `coffee-rails` gem is in the `Gemfile`) and a
 Cascading Style Sheet file (or SCSS file if `sass-rails` is in the `Gemfile`)
 for that controller. Additionally, when generating a scaffold, Rails generates
-the file scaffolds.css (or scaffolds.scss if `sass-rails` is in the
+the file `scaffolds.css` (or `scaffolds.scss` if `sass-rails` is in the
 `Gemfile`.)
 
 For example, if you generate a `ProjectsController`, Rails will also add a new
@@ -202,7 +202,7 @@ will result in your assets being included more than once.
 
 WARNING: When using asset precompilation, you will need to ensure that your
 controller assets will be precompiled when loading them on a per page basis. By
-default .coffee and .scss files will not be precompiled on their own. See
+default `.coffee` and `.scss` files will not be precompiled on their own. See
 [Precompiling Assets](#precompiling-assets) for more information on how
 precompiling works.
 
@@ -726,7 +726,7 @@ include, you can add them to the `precompile` array in `config/initializers/asse
 Rails.application.config.assets.precompile += %w( admin.js admin.css )
 ```
 
-NOTE. Always specify an expected compiled filename that ends with .js or .css,
+NOTE. Always specify an expected compiled filename that ends with `.js` or `.css`,
 even if you want to add Sass or CoffeeScript files to the precompile array.
 
 The task also generates a `.sprockets-manifest-md5hash.json` (where `md5hash` is
@@ -850,7 +850,7 @@ This mode uses more memory, performs more poorly than the default and is not
 recommended.
 
 If you are deploying a production application to a system without any
-pre-existing JavaScript runtimes, you may want to add one to your Gemfile:
+pre-existing JavaScript runtimes, you may want to add one to your `Gemfile`:
 
 ```ruby
 group :production do
@@ -1090,7 +1090,7 @@ Possible options for JavaScript compression are `:closure`, `:uglifier` and
 `:yui`. These require the use of the `closure-compiler`, `uglifier` or
 `yui-compressor` gems, respectively.
 
-The default Gemfile includes [uglifier](https://github.com/lautis/uglifier).
+The default `Gemfile` includes [uglifier](https://github.com/lautis/uglifier).
 This gem wraps [UglifyJS](https://github.com/mishoo/UglifyJS) (written for
 NodeJS) in Ruby. It compresses your code by removing white space and comments,
 shortening local variable names, and performing other micro-optimizations such
@@ -1219,7 +1219,7 @@ Sprockets uses Processors, Transformers, Compressors, and Exporters to extend
 Sprockets functionality. Have a look at
 [Extending Sprockets](https://github.com/rails/sprockets/blob/master/guides/extending_sprockets.md)
 to learn more. Here we registered a preprocessor to add a comment to the end
-of text/css (.css) files.
+of text/css (`.css`) files.
 
 ```ruby
 module AddComment
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index b5bd24d027..9616647f15 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -906,7 +906,7 @@ The `belongs_to` association supports these options:
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -1257,7 +1257,7 @@ Setting the `:as` option indicates that this is a polymorphic association. Polym
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -1653,7 +1653,7 @@ Setting the `:as` option indicates that this is a polymorphic association, as di
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -2176,7 +2176,7 @@ end
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md
index c62194faf4..dea87a18f8 100644
--- a/guides/source/autoloading_and_reloading_constants.md
+++ b/guides/source/autoloading_and_reloading_constants.md
@@ -330,11 +330,17 @@ its resolution next. Let's define *parent* to be that qualifying class or module
 object, that is, `Billing` in the example above. The algorithm for qualified
 constants goes like this:
 
-1. The constant is looked up in the parent and its ancestors.
+1. The constant is looked up in the parent and its ancestors. In Ruby >= 2.5,
+`Object` is skipped if present among the ancestors. `Kernel` and `BasicObject`
+are still checked though.
 
 2. If the lookup fails, `const_missing` is invoked in the parent. The default
 implementation of `const_missing` raises `NameError`, but it can be overridden.
 
+INFO. In Ruby < 2.5 `String::Hash` evaluates to `Hash` and the interpreter
+issues a warning: "toplevel constant Hash referenced by String::Hash". Starting
+with 2.5, `String::Hash` raises `NameError` because `Object` is skipped.
+
 As you see, this algorithm is simpler than the one for relative constants. In
 particular, the nesting plays no role here, and modules are not special-cased,
 if neither they nor their ancestors have the constants, `Object` is **not**
@@ -954,7 +960,7 @@ to work on some subclass, things get interesting.
 While working with `Polygon` you do not need to be aware of all its descendants,
 because anything in the table is by definition a polygon, but when working with
 subclasses Active Record needs to be able to enumerate the types it is looking
-for. Let’s see an example.
+for. Let's see an example.
 
 `Rectangle.all` only loads rectangles by adding a type constraint to the query:
 
@@ -963,7 +969,7 @@ SELECT "polygons".* FROM "polygons"
 WHERE "polygons"."type" IN ("Rectangle")
 ```
 
-Let’s introduce now a subclass of `Rectangle`:
+Let's introduce now a subclass of `Rectangle`:
 
 ```ruby
 # app/models/square.rb
@@ -978,7 +984,7 @@ SELECT "polygons".* FROM "polygons"
 WHERE "polygons"."type" IN ("Rectangle", "Square")
 ```
 
-But there’s a caveat here: How does Active Record know that the class `Square`
+But there's a caveat here: How does Active Record know that the class `Square`
 exists at all?
 
 Even if the file `app/models/square.rb` exists and defines the `Square` class,
@@ -1049,7 +1055,7 @@ end
 
 The purpose of this setup would be that the application uses the class that
 corresponds to the environment via `AUTH_SERVICE`. In development mode
-`MockedAuthService` gets autoloaded when the initializer runs. Let’s suppose
+`MockedAuthService` gets autoloaded when the initializer runs. Let's suppose
 we do some requests, change its implementation, and hit the application again.
 To our surprise the changes are not reflected. Why?
 
@@ -1178,6 +1184,8 @@ end
 
 #### Qualified References
 
+WARNING. This gotcha is only possible in Ruby < 2.5.
+
 Given
 
 ```ruby
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 910a531068..780e69c146 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -32,7 +32,7 @@ Basic Caching
 This is an introduction to three types of caching techniques: page, action and
 fragment caching. By default Rails provides fragment caching. In order to use
 page and action caching you will need to add `actionpack-page_caching` and
-`actionpack-action_caching` to your Gemfile.
+`actionpack-action_caching` to your `Gemfile`.
 
 By default, caching is only enabled in your production environment. To play
 around with caching locally you'll want to enable caching in your local
@@ -181,7 +181,7 @@ cache.
 
 ### Shared Partial Caching
 
-It is possible to share partials and associated caching between files with different mime types. For example shared partial caching allows template writers to share a partial between HTML and Javascript files. When templates are collected in the template resolver file paths they only include the template language extension and not the mime type. Because of this templates can be used for multiple mime types. Both HTML and JavaScript requests will respond to the following code:
+It is possible to share partials and associated caching between files with different mime types. For example shared partial caching allows template writers to share a partial between HTML and JavaScript files. When templates are collected in the template resolver file paths they only include the template language extension and not the mime type. Because of this templates can be used for multiple mime types. Both HTML and JavaScript requests will respond to the following code:
 
 ```ruby
 render(partial: 'hotels/hotel', collection: @hotels, cached: true)
@@ -195,7 +195,7 @@ Another option is to include the full filename of the partial to render.
 render(partial: 'hotels/hotel.html.erb', collection: @hotels, cached: true)
 ```
 
-Will load a file named `hotels/hotel.html.erb` in any file mime type, for example you could include this partial in a Javascript file.
+Will load a file named `hotels/hotel.html.erb` in any file mime type, for example you could include this partial in a JavaScript file.
 
 ### Managing dependencies
 
@@ -366,9 +366,9 @@ There are some common options used by all cache implementations. These can be pa
 
 * `:namespace` - This option can be used to create a namespace within the cache store. It is especially useful if your application shares a cache with other applications.
 
-* `:compress` - This option can be used to indicate that compression should be used in the cache. This can be useful for transferring large cache entries over a slow network.
+* `:compress` - Enabled by default. Compresses cache entries so more data can be stored in the same memory footprint, leading to fewer cache evictions and higher hit rates.
 
-* `:compress_threshold` - This option is used in conjunction with the `:compress` option to indicate a threshold under which cache entries should not be compressed. This defaults to 16 kilobytes.
+* `:compress_threshold` - Defaults to 1kB. Cache entries larger than this threshold, specified in bytes, are compressed.
 
 * `:expires_in` - This option sets an expiration time in seconds for the cache entry when it will be automatically removed from the cache.
 
@@ -444,6 +444,53 @@ The `write` and `fetch` methods on this cache accept two additional options that
 config.cache_store = :mem_cache_store, "cache-1.example.com", "cache-2.example.com"
 ```
 
+### ActiveSupport::Cache::RedisCacheStore
+
+The Redis cache store takes advantage of Redis support for least-recently-used
+and least-frequently-used key eviction when it reaches max memory, allowing it
+to behave much like a Memcached cache server.
+
+Deployment note: Redis doesn't expire keys by default, so take care to use a
+dedicated Redis cache server. Don't fill up your persistent-Redis server with
+volatile cache data! Read the
+[Redis cache server setup guide](https://redis.io/topics/lru-cache) in detail.
+
+For an all-cache Redis server, set `maxmemory-policy` to an `allkeys` policy.
+Redis 4+ support least-frequently-used (`allkeys-lfu`) eviction, an excellent
+default choice. Redis 3 and earlier should use `allkeys-lru` for
+least-recently-used eviction.
+
+Set cache read and write timeouts relatively low. Regenerating a cached value
+is often faster than waiting more than a second to retrieve it. Both read and
+write timeouts default to 1 second, but may be set lower if your network is
+consistently low latency.
+
+Cache reads and writes never raise exceptions. They just return `nil` instead,
+behaving as if there was nothing in the cache. To gauge whether your cache is
+hitting exceptions, you may provide an `error_handler` to report to an
+exception gathering service. It must accept three keyword arguments: `method`,
+the cache store method that was originally called; `returning`, the value that
+was returned to the user, typically `nil`; and `exception`, the exception that
+was rescued.
+
+Putting it all together, a production Redis cache store may look something
+like this:
+
+```ruby
+cache_servers = %w[ "redis://cache-01:6379/0", "redis://cache-02:6379/0", … ],
+config.cache_store = :redis_cache_store, url: cache_servers,
+
+  connect_timeout: 30,  # Defaults to 20 seconds
+  read_timeout:    0.2, # Defaults to 1 second
+  write_timeout:   0.2, # Defaults to 1 second
+
+  error_handler: -> (method:, returning:, exception:) {
+    # Report errors to Sentry as warnings
+    Raven.capture_exception exception, level: 'warning",
+      tags: { method: method, returning: returning }
+  }
+```
+
 ### ActiveSupport::Cache::NullStore
 
 This cache store implementation is meant to be used only in development or test environments and it never stores anything. This can be very useful in development when you have code that interacts directly with `Rails.cache` but caching may interfere with being able to see the results of code changes. With this cache store, all `fetch` and `read` operations will result in a miss.
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index 2cd8e02a77..648645af7c 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -290,7 +290,7 @@ INFO: You can also use the alias "c" to invoke the console: `rails c`.
 You can specify the environment in which the `console` command should operate.
 
 ```bash
-$ bin/rails console staging
+$ bin/rails console -e staging
 ```
 
 If you wish to test out some code without changing any data, you can do that by invoking `rails console --sandbox`.
@@ -659,6 +659,6 @@ development:
 ...
 ```
 
-It also generated some lines in our database.yml configuration corresponding to our choice of PostgreSQL for database.
+It also generated some lines in our `database.yml` configuration corresponding to our choice of PostgreSQL for database.
 
 NOTE. The only catch with using the SCM options is that you have to make your application's directory first, then initialize your SCM, then you can run the `rails new` command to generate the basis of your app.
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 1c720ad82f..fee644d4d4 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -391,7 +391,7 @@ by setting up a Rake task which runs
     ```
 
   for all models and all boolean columns, after which the flag must be set to true
-by adding the following to your application.rb file:
+by adding the following to your `application.rb` file:
 
     ```ruby
     Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
@@ -487,6 +487,15 @@ Defaults to `'signed cookie'`.
   authenticated encrypted cookie salt. Defaults to `'authenticated encrypted
   cookie'`.
 
+* `config.action_dispatch.encrypted_cookie_cipher` sets the cipher to be
+  used for encrypted cookies. This defaults to `"aes-256-gcm"`.
+
+* `config.action_dispatch.signed_cookie_digest` sets the digest to be
+  used for signed cookies. This defaults to `"SHA1"`.
+
+* `config.action_dispatch.cookies_rotations` allows rotating
+  secrets, ciphers, and digests for encrypted and signed cookies.
+
 * `config.action_dispatch.perform_deep_munge` configures whether `deep_munge`
   method should be performed on the parameters. See [Security Guide](security.html#unsafe-query-generation)
   for more information. It defaults to `true`.
@@ -563,12 +572,14 @@ Defaults to `'signed cookie'`.
   error should be raised for missing translations.
 
 * `config.action_view.automatically_disable_submit_tag` determines whether
-  submit_tag should automatically disable on click, this defaults to `true`.
+  `submit_tag` should automatically disable on click, this defaults to `true`.
 
 * `config.action_view.debug_missing_translation` determines whether to wrap the missing translations key in a `<span>` tag or not. This defaults to `true`.
 
 * `config.action_view.form_with_generates_remote_forms` determines whether `form_with` generates remote forms or not. This defaults to `true`.
 
+* `config.action_view.form_with_generates_ids` determines whether `form_with` generates ids on inputs. This defaults to `true`.
+
 ### Configuring Action Mailer
 
 There are a number of settings available on `config.action_mailer`:
@@ -964,7 +975,7 @@ By default Rails ships with three environments: "development", "test", and "prod
 
 Imagine you have a server which mirrors the production environment but is only used for testing. Such a server is commonly called a "staging server". To define an environment called "staging" for this server, just create a file called `config/environments/staging.rb`. Please use the contents of any existing file in `config/environments` as a starting point and make the necessary changes from there.
 
-That environment is no different than the default ones, start a server with `rails server -e staging`, a console with `rails console staging`, `Rails.env.staging?` works, etc.
+That environment is no different than the default ones, start a server with `rails server -e staging`, a console with `rails console -e staging`, `Rails.env.staging?` works, etc.
 
 
 ### Deploy to a subdirectory (relative url root)
@@ -994,11 +1005,11 @@ Deploying your application using a reverse proxy has definite advantages over tr
 
 Many modern web servers can be used as a proxy server to balance third-party elements such as caching servers or application servers.
 
-One such application server you can use is [Unicorn](http://unicorn.bogomips.org/) to run behind a reverse proxy.
+One such application server you can use is [Unicorn](https://bogomips.org/unicorn/) to run behind a reverse proxy.
 
 In this case, you would need to configure the proxy server (NGINX, Apache, etc) to accept connections from your application server (Unicorn). By default Unicorn will listen for TCP connections on port 8080, but you can change the port or configure it to use sockets instead.
 
-You can find more information in the [Unicorn readme](http://unicorn.bogomips.org/README.html) and understand the [philosophy](http://unicorn.bogomips.org/PHILOSOPHY.html) behind it.
+You can find more information in the [Unicorn readme](https://bogomips.org/unicorn/README.html) and understand the [philosophy](https://bogomips.org/unicorn/PHILOSOPHY.html) behind it.
 
 Once you've configured the application server, you must proxy requests to it by configuring your web server appropriately. For example your NGINX config may include:
 
@@ -1026,7 +1037,7 @@ server {
 }
 ```
 
-Be sure to read the [NGINX documentation](http://nginx.org/en/docs/) for the most up-to-date information.
+Be sure to read the [NGINX documentation](https://nginx.org/en/docs/) for the most up-to-date information.
 
 
 Rails Environment Settings
@@ -1048,7 +1059,7 @@ After loading the framework and any gems in your application, Rails turns to loa
 
 NOTE: You can use subfolders to organize your initializers if you like, because Rails will look into the whole file hierarchy from the initializers folder on down.
 
-TIP: If you have any ordering dependency in your initializers, you can control the load order through naming. Initializer files are loaded in alphabetical order by their path. For example, `01_critical.rb` will be loaded before `02_normal.rb`.
+TIP: While Rails supports numbering of initializer file names for load ordering purposes, a better technique is to place any code that need to load in a specific order within the same file. This reduces file name churn, makes dependencies more explicit, and can help surface new concepts within your application.
 
 Initialization events
 ---------------------
@@ -1308,7 +1319,7 @@ know which pages it is allowed to index.
 
 Rails creates this file for you inside the `/public` folder. By default, it allows
 search engines to index all pages of your application. If you want to block
-indexing on all pages of you application, use this:
+indexing on all pages of your application, use this:
 
 ```
 User-agent: *
diff --git a/guides/source/documents.yaml b/guides/source/documents.yaml
index 59205ee465..2a4abab116 100644
--- a/guides/source/documents.yaml
+++ b/guides/source/documents.yaml
@@ -159,6 +159,11 @@
       url: engines.html
       description: This guide explains how to write a mountable engine.
       work_in_progress: true
+    -
+      name: Threading and Code Execution in Rails
+      url: threading_and_code_execution.html
+      description: This guide describes the considerations needed and tools available when working directly with concurrency in a Rails application.
+      work_in_progress: true
 -
   name: Contributing to Ruby on Rails
   documents:
@@ -189,6 +194,10 @@
       url: upgrading_ruby_on_rails.html
       description: This guide helps in upgrading applications to latest Ruby on Rails versions.
     -
+      name: Ruby on Rails 5.2 Release Notes
+      url: 5_2_release_notes.html
+      description: Release notes for Rails 5.2.
+    -
       name: Ruby on Rails 5.1 Release Notes
       url: 5_1_release_notes.html
       description: Release notes for Rails 5.1.
diff --git a/guides/source/engines.md b/guides/source/engines.md
index c7331b6ca4..33694cf76a 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -63,7 +63,7 @@ authentication for its parent applications, or
 [Thredded](https://github.com/thredded/thredded), an engine that provides forum
 functionality. There's also [Spree](https://github.com/spree/spree) which
 provides an e-commerce platform, and
-[RefineryCMS](https://github.com/refinery/refinerycms), a CMS engine.
+[Refinery CMS](https://github.com/refinery/refinerycms), a CMS engine.
 
 Finally, engines would not have been possible without the work of James Adam,
 Piotr Sarnacki, the Rails Core Team, and a number of other people. If you ever
@@ -537,12 +537,12 @@ directory at `app/views/blorgh/comments` and in it a new file called
 
 ```html+erb
 <h3>New comment</h3>
-<%= form_for [@article, @article.comments.build] do |f| %>
+<%= form_with(model: [@article, @article.comments.build], local: true) do |form| %>
   <p>
-    <%= f.label :text %><br>
-    <%= f.text_area :text %>
+    <%= form.label :text %><br>
+    <%= form.text_area :text %>
   </p>
-  <%= f.submit %>
+  <%= form.submit %>
 <% end %>
 ```
 
@@ -653,7 +653,7 @@ there isn't an application handy to test this out in, generate one using the
 $ rails new unicorn
 ```
 
-Usually, specifying the engine inside the Gemfile would be done by specifying it
+Usually, specifying the engine inside the `Gemfile` would be done by specifying it
 as a normal, everyday gem.
 
 ```ruby
@@ -783,8 +783,8 @@ added above the `title` field with this code:
 
 ```html+erb
 <div class="field">
-  <%= f.label :author_name %><br>
-  <%= f.text_field :author_name %>
+  <%= form.label :author_name %><br>
+  <%= form.text_field :author_name %>
 </div>
 ```
 
@@ -921,7 +921,7 @@ engine:
 mattr_accessor :author_class
 ```
 
-This method works like its brothers, `attr_accessor` and `cattr_accessor`, but
+This method works like its siblings, `attr_accessor` and `cattr_accessor`, but
 provides a setter and getter method on the module with the specified name. To
 use it, it must be referenced using `Blorgh.author_class`.
 
@@ -982,7 +982,7 @@ Blorgh.author_class = "User"
 WARNING: It's very important here to use the `String` version of the class,
 rather than the class itself. If you were to use the class, Rails would attempt
 to load that class and then reference the related table. This could lead to
-problems if the table wasn't already existing. Therefore, a `String` should be
+problems if the table didn't already exist. Therefore, a `String` should be
 used and then converted to a class using `constantize` in the engine later on.
 
 Go ahead and try to create a new article. You will see that it works exactly in the
@@ -1322,7 +1322,7 @@ engine.
 
 Assets within an engine work in an identical way to a full application. Because
 the engine class inherits from `Rails::Engine`, the application will know to
-look up assets in the engine's 'app/assets' and 'lib/assets' directories.
+look up assets in the engine's `app/assets` and `lib/assets` directories.
 
 Like all of the other components of an engine, the assets should be namespaced.
 This means that if you have an asset called `style.css`, it should be placed at
@@ -1361,7 +1361,7 @@ that only exists for your engine. In this case, the host application doesn't
 need to require `admin.css` or `admin.js`. Only the gem's admin layout needs
 these assets. It doesn't make sense for the host app to include
 `"blorgh/admin.css"` in its stylesheets. In this situation, you should
-explicitly define these assets for precompilation.  This tells sprockets to add
+explicitly define these assets for precompilation.  This tells Sprockets to add
 your engine assets when `bin/rails assets:precompile` is triggered.
 
 You can define assets for precompilation in `engine.rb`:
@@ -1501,6 +1501,7 @@ To hook into the initialization process of one of the following classes use the
 | `ActionController::Base`          | `action_controller`                  |
 | `ActionController::TestCase`      | `action_controller_test_case`        |
 | `ActionDispatch::IntegrationTest` | `action_dispatch_integration_test`   |
+| `ActionDispatch::SystemTestCase`  | `action_dispatch_system_test_case`   |
 | `ActionMailer::Base`              | `action_mailer`                      |
 | `ActionMailer::TestCase`          | `action_mailer_test_case`            |
 | `ActionView::Base`                | `action_view`                        |
@@ -1513,7 +1514,7 @@ To hook into the initialization process of one of the following classes use the
 
 ## Configuration hooks
 
-These are the available configuration hooks. They do not hook into any particular framework, instead they run in context of the entire application.
+These are the available configuration hooks. They do not hook into any particular framework, but instead they run in context of the entire application.
 
 | Hook                   | Use Case                                                                              |
 | ---------------------- | ------------------------------------------------------------------------------------- |
diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md
index f46f1648b3..f8ec389b01 100644
--- a/guides/source/form_helpers.md
+++ b/guides/source/form_helpers.md
@@ -274,10 +274,12 @@ There are a few things to note here:
 The resulting HTML is:
 
 ```html
-<form accept-charset="UTF-8" action="/articles" method="post" class="nifty_form">
-  <input id="article_title" name="article[title]" type="text" />
-  <textarea id="article_body" name="article[body]" cols="60" rows="12"></textarea>
-  <input name="commit" type="submit" value="Create" />
+<form class="nifty_form" id="new_article" action="/articles" accept-charset="UTF-8" method="post">
+  <input name="utf8" type="hidden" value="&#x2713;" />
+  <input type="hidden" name="authenticity_token" value="NRkFyRWxdYNfUg7vYxLOp2SLf93lvnl+QwDWorR42Dp6yZXPhHEb6arhDOIWcqGit8jfnrPwL781/xlrzj63TA==" />
+  <input type="text" name="article[title]" id="article_title" />
+  <textarea name="article[body]" id="article_body" cols="60" rows="12"></textarea>
+  <input type="submit" name="commit" value="Create" data-disable-with="Create" />
 </form>
 ```
 
@@ -299,9 +301,11 @@ You can create a similar binding without actually creating `<form>` tags with th
 which produces the following output:
 
 ```html
-<form accept-charset="UTF-8" action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-  <input id="contact_detail_phone_number" name="contact_detail[phone_number]" type="text" />
+<form class="new_person" id="new_person" action="/people" accept-charset="UTF-8" method="post">
+  <input name="utf8" type="hidden" value="&#x2713;" />
+  <input type="hidden" name="authenticity_token" value="bL13x72pldyDD8bgtkjKQakJCpd4A8JdXGbfksxBDHdf1uC0kCMqe2tvVdUYfidJt0fj3ihC4NxiVHv8GVYxJA==" />
+  <input type="text" name="person[name]" id="person_name" />
+  <input type="text" name="contact_detail[phone_number]" id="contact_detail_phone_number" />
 </form>
 ```
 
@@ -916,7 +920,7 @@ When an association accepts nested attributes `fields_for` renders its block onc
 ```ruby
 def new
   @person = Person.new
-  2.times { @person.addresses.build}
+  2.times { @person.addresses.build }
 end
 ```
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index 7c7b3a4c01..b007baea87 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -172,14 +172,14 @@ of the files and folders that Rails created by default:
 |app/|Contains the controllers, models, views, helpers, mailers, channels, jobs and assets for your application. You'll focus on this folder for the remainder of this guide.|
 |bin/|Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy or run your application.|
 |config/|Configure your application's routes, database, and more. This is covered in more detail in [Configuring Rails Applications](configuring.html).|
-|config.ru|Rack configuration for Rack based servers used to start the application.|
+|config.ru|Rack configuration for Rack based servers used to start the application. For more information about Rack, see the [Rack website](https://rack.github.io/).|
 |db/|Contains your current database schema, as well as the database migrations.|
 |Gemfile<br>Gemfile.lock|These files allow you to specify what gem dependencies are needed for your Rails application. These files are used by the Bundler gem. For more information about Bundler, see the [Bundler website](https://bundler.io).|
 |lib/|Extended modules for your application.|
 |log/|Application log files.|
 |package.json|This file allows you to specify what npm dependencies are needed for your Rails application. This file is used by Yarn. For more information about Yarn, see the [Yarn website](https://yarnpkg.com/lang/en/).|
 |public/|The only folder seen by the world as-is. Contains static files and compiled assets.|
-|Rakefile|This file locates and loads tasks that can be run from the command line. The task definitions are defined throughout the components of Rails. Rather than changing Rakefile, you should add your own tasks by adding files to the `lib/tasks` directory of your application.|
+|Rakefile|This file locates and loads tasks that can be run from the command line. The task definitions are defined throughout the components of Rails. Rather than changing `Rakefile`, you should add your own tasks by adding files to the `lib/tasks` directory of your application.|
 |README.md|This is a brief instruction manual for your application. You should edit this file to tell others what your application does, how to set it up, and so on.|
 |test/|Unit tests, fixtures, and other test apparatus. These are covered in [Testing Rails Applications](testing.html).|
 |tmp/|Temporary files (like cache and pid files).|
@@ -372,16 +372,17 @@ singular form `article` and makes meaningful use of the distinction.
 
 ```bash
 $ bin/rails routes
-      Prefix Verb   URI Pattern                  Controller#Action
-    articles GET    /articles(.:format)          articles#index
-             POST   /articles(.:format)          articles#create
- new_article GET    /articles/new(.:format)      articles#new
-edit_article GET    /articles/:id/edit(.:format) articles#edit
-     article GET    /articles/:id(.:format)      articles#show
-             PATCH  /articles/:id(.:format)      articles#update
-             PUT    /articles/:id(.:format)      articles#update
-             DELETE /articles/:id(.:format)      articles#destroy
-        root GET    /                            welcome#index
+       Prefix Verb   URI Pattern                  Controller#Action
+welcome_index GET    /welcome/index(.:format)     welcome#index
+     articles GET    /articles(.:format)          articles#index
+              POST   /articles(.:format)          articles#create
+  new_article GET    /articles/new(.:format)      articles#new
+ edit_article GET    /articles/:id/edit(.:format) articles#edit
+      article GET    /articles/:id(.:format)      articles#show
+              PATCH  /articles/:id(.:format)      articles#update
+              PUT    /articles/:id(.:format)      articles#update
+              DELETE /articles/:id(.:format)      articles#destroy
+         root GET    /                            welcome#index
 ```
 
 In the next section, you will add the ability to create new articles in your
@@ -567,15 +568,16 @@ To see what Rails will do with this, we look back at the output of
 ```bash
 $ bin/rails routes
       Prefix Verb   URI Pattern                  Controller#Action
-    articles GET    /articles(.:format)          articles#index
-             POST   /articles(.:format)          articles#create
- new_article GET    /articles/new(.:format)      articles#new
-edit_article GET    /articles/:id/edit(.:format) articles#edit
-     article GET    /articles/:id(.:format)      articles#show
-             PATCH  /articles/:id(.:format)      articles#update
-             PUT    /articles/:id(.:format)      articles#update
-             DELETE /articles/:id(.:format)      articles#destroy
-        root GET    /                            welcome#index
+welcome_index GET    /welcome/index(.:format)     welcome#index
+     articles GET    /articles(.:format)          articles#index
+              POST   /articles(.:format)          articles#create
+  new_article GET    /articles/new(.:format)      articles#new
+ edit_article GET    /articles/:id/edit(.:format) articles#edit
+      article GET    /articles/:id(.:format)      articles#show
+              PATCH  /articles/:id(.:format)      articles#update
+              PUT    /articles/:id(.:format)      articles#update
+              DELETE /articles/:id(.:format)      articles#destroy
+         root GET    /                            welcome#index
 ```
 
 The `articles_path` helper tells Rails to point the form to the URI Pattern
@@ -594,7 +596,7 @@ familiar error:
 You now need to create the `create` action within the `ArticlesController` for
 this to work.
 
-NOTE: by default `form_with` submits forms using Ajax thereby skipping full page
+NOTE: By default `form_with` submits forms using Ajax thereby skipping full page
 redirects. To make this guide easier to get into we've disabled that with
 `local: true` for now.
 
diff --git a/guides/source/i18n.md b/guides/source/i18n.md
index cb24822f86..2b545e6b82 100644
--- a/guides/source/i18n.md
+++ b/guides/source/i18n.md
@@ -977,7 +977,7 @@ en:
 ```
 
 NOTE: In order to use this helper, you need to install [DynamicForm](https://github.com/joelmoss/dynamic_form)
-gem by adding this line to your Gemfile: `gem 'dynamic_form'`.
+gem by adding this line to your `Gemfile`: `gem 'dynamic_form'`.
 
 ### Translations for Action Mailer E-Mail Subjects
 
@@ -1171,7 +1171,7 @@ Conclusion
 
 At this point you should have a good overview about how I18n support in Ruby on Rails works and are ready to start translating your project.
 
-If you want to discuss certain portions or have questions, please sign up to the [rails-i18n mailing list](http://groups.google.com/group/rails-i18n).
+If you want to discuss certain portions or have questions, please sign up to the [rails-i18n mailing list](https://groups.google.com/forum/#!forum/rails-i18n).
 
 
 Contributing to Rails I18n
@@ -1179,7 +1179,7 @@ Contributing to Rails I18n
 
 I18n support in Ruby on Rails was introduced in the release 2.2 and is still evolving. The project follows the good Ruby on Rails development tradition of evolving solutions in gems and real applications first, and only then cherry-picking the best-of-breed of most widely useful features for inclusion in the core.
 
-Thus we encourage everybody to experiment with new ideas and features in gems or other libraries and make them available to the community. (Don't forget to announce your work on our [mailing list](http://groups.google.com/group/rails-i18n)!)
+Thus we encourage everybody to experiment with new ideas and features in gems or other libraries and make them available to the community. (Don't forget to announce your work on our [mailing list](https://groups.google.com/forum/#!forum/rails-i18n)!)
 
 If you find your own locale (language) missing from our [example translations data](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) repository for Ruby on Rails, please [_fork_](https://github.com/guides/fork-a-project-and-submit-your-modifications) the repository, add your data and send a [pull request](https://help.github.com/articles/about-pull-requests/).
 
diff --git a/guides/source/initialization.md b/guides/source/initialization.md
index 1541ea38cd..c4f1df487b 100644
--- a/guides/source/initialization.md
+++ b/guides/source/initialization.md
@@ -93,7 +93,7 @@ require 'bundler/setup' # Set up gems listed in the Gemfile.
 
 In a standard Rails application, there's a `Gemfile` which declares all
 dependencies of the application. `config/boot.rb` sets
-`ENV['BUNDLE_GEMFILE']` to the location of this file. If the Gemfile
+`ENV['BUNDLE_GEMFILE']` to the location of this file. If the `Gemfile`
 exists, then `bundler/setup` is required. The require is used by Bundler to
 configure the load path for your Gemfile's dependencies.
 
diff --git a/guides/source/layout.html.erb b/guides/source/layout.html.erb
index 334595e4d2..3981199e95 100644
--- a/guides/source/layout.html.erb
+++ b/guides/source/layout.html.erb
@@ -99,9 +99,9 @@
           To get started, you can read our <%= link_to 'documentation contributions', 'http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#contributing-to-the-rails-documentation' %> section.
         </p>
         <p>
-          You may also find incomplete content, or stuff that is not up to date.
+          You may also find incomplete content or stuff that is not up to date.
           Please do add any missing documentation for master. Make sure to check
-          <%= link_to 'Edge Guides','http://edgeguides.rubyonrails.org' %> first to verify
+          <%= link_to 'Edge Guides', 'http://edgeguides.rubyonrails.org' %> first to verify
           if the issues are already fixed or not on the master branch.
           Check the <%= link_to 'Ruby on Rails Guides Guidelines', 'ruby_on_rails_guides_guidelines.html' %>
           for style and conventions.
@@ -111,7 +111,7 @@
           <%= link_to 'open an issue', 'https://github.com/rails/rails/issues' %>.
         </p>
         <p>And last but not least, any kind of discussion regarding Ruby on Rails
-          documentation is very welcome in the <%= link_to 'rubyonrails-docs mailing list', 'https://groups.google.com/forum/#!forum/rubyonrails-docs' %>.
+          documentation is very welcome on the <%= link_to 'rubyonrails-docs mailing list', 'https://groups.google.com/forum/#!forum/rubyonrails-docs' %>.
         </p>
       </div>
     </div>
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 76b325d0bf..4d79b2db89 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -71,23 +71,25 @@ If we want to display the properties of all the books in our view, we can do so
 <h1>Listing Books</h1>
 
 <table>
-  <tr>
-    <th>Title</th>
-    <th>Summary</th>
-    <th></th>
-    <th></th>
-    <th></th>
-  </tr>
-
-<% @books.each do |book| %>
-  <tr>
-    <td><%= book.title %></td>
-    <td><%= book.content %></td>
-    <td><%= link_to "Show", book %></td>
-    <td><%= link_to "Edit", edit_book_path(book) %></td>
-    <td><%= link_to "Remove", book, method: :delete, data: { confirm: "Are you sure?" } %></td>
-  </tr>
-<% end %>
+  <thead>
+    <tr>
+      <th>Title</th>
+      <th>Content</th>
+      <th colspan="3"></th>
+    </tr>
+  </thead>
+
+  <tbody>
+    <% @books.each do |book| %>
+      <tr>
+        <td><%= book.title %></td>
+        <td><%= book.content %></td>
+        <td><%= link_to "Show", book %></td>
+        <td><%= link_to "Edit", edit_book_path(book) %></td>
+        <td><%= link_to "Destroy", book, method: :delete, data: { confirm: "Are you sure?" } %></td>
+      </tr>
+    <% end %>
+  </tbody>
 </table>
 
 <br>
@@ -230,14 +232,14 @@ You can send an HTML string back to the browser by using the `:html` option to
 `render`:
 
 ```ruby
-render html: "<strong>Not Found</strong>".html_safe
+render html: helpers.tag.strong('Not Found')
 ```
 
 TIP: This is useful when you're rendering a small snippet of HTML code.
 However, you might want to consider moving it to a template file if the markup
 is complex.
 
-NOTE: When using `html:` option, HTML entities will be escaped if the string is not marked as HTML safe by using `html_safe` method.
+NOTE: When using `html:` option, HTML entities will be escaped if the string is not composed with `html_safe`-aware APIs.
 
 #### Rendering JSON
 
@@ -283,7 +285,7 @@ the response. Using `:plain` or `:html` might be more appropriate most of the
 time.
 
 NOTE: Unless overridden, your response returned from this render option will be
-`text/html`, as that is the default content type of Action Dispatch response.
+`text/plain`, as that is the default content type of Action Dispatch response.
 
 #### Options for `render`
 
@@ -1264,7 +1266,7 @@ You can also pass in arbitrary local variables to any partial you are rendering
 
 In this case, the partial will have access to a local variable `title` with the value "Products Page".
 
-TIP: Rails also makes a counter variable available within a partial called by the collection, named after the member of the collection followed by `_counter`. For example, if you're rendering `@products`, within the partial you can refer to `product_counter` to tell you how many times the partial has been rendered. This does not work in conjunction with the `as: :value` option.
+TIP: Rails also makes a counter variable available within a partial called by the collection, named after the title of the partial followed by `_counter`. For example, when rendering a collection `@products` the partial `_product.html.erb` can access the variable `product_counter` which indexes the number of times it has been rendered within the enclosing view.
 
 You can also specify a second partial to be rendered between instances of the main partial by using the `:spacer_template` option:
 
diff --git a/guides/source/plugins.md b/guides/source/plugins.md
index 0f0cde7634..15073af6be 100644
--- a/guides/source/plugins.md
+++ b/guides/source/plugins.md
@@ -237,7 +237,7 @@ Finished in 0.004812s, 831.2949 runs/s, 415.6475 assertions/s.
 
 This tells us that we don't have the necessary models (Hickwall and Wickwall) that we are trying to test.
 We can easily generate these models in our "dummy" Rails application by running the following commands from the
-test/dummy directory:
+`test/dummy` directory:
 
 ```bash
 $ cd test/dummy
@@ -359,7 +359,7 @@ When you run `bin/test`, you should see the tests all pass:
 
 ### Add an Instance Method
 
-This plugin will add a method named 'squawk' to any Active Record object that calls 'acts_as_yaffle'. The 'squawk'
+This plugin will add a method named 'squawk' to any Active Record object that calls `acts_as_yaffle`. The 'squawk'
 method will simply set the value of one of the fields in the database.
 
 To start out, write a failing test that shows the behavior you'd like:
@@ -392,7 +392,7 @@ end
 ```
 
 Run the test to make sure the last two tests fail with an error that contains "NoMethodError: undefined method `squawk'",
-then update 'acts_as_yaffle.rb' to look like this:
+then update `acts_as_yaffle.rb` to look like this:
 
 ```ruby
 # yaffle/lib/yaffle/acts_as_yaffle.rb
@@ -446,7 +446,7 @@ Publishing Your Gem
 -------------------
 
 Gem plugins currently in development can easily be shared from any Git repository. To share the Yaffle gem with others, simply
-commit the code to a Git repository (like GitHub) and add a line to the Gemfile of the application in question:
+commit the code to a Git repository (like GitHub) and add a line to the `Gemfile` of the application in question:
 
 ```ruby
 gem "yaffle", git: "https://github.com/rails/yaffle.git"
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index aa1476ecc0..5718b9ddfc 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -122,6 +122,7 @@ use ActiveRecord::Migration::CheckPending
 use ActionDispatch::Cookies
 use ActionDispatch::Session::CookieStore
 use ActionDispatch::Flash
+use ActionDispatch::ContentSecurityPolicy::Middleware
 use Rack::Head
 use Rack::ConditionalGet
 use Rack::ETag
@@ -249,7 +250,7 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 **`Rails::Rack::Logger`**
 
-* Notifies the logs that the request has began. After request is complete, flushes all the logs.
+* Notifies the logs that the request has begun. After the request is complete, flushes all the logs.
 
 **`ActionDispatch::ShowExceptions`**
 
@@ -289,7 +290,7 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 **`Rack::ConditionalGet`**
 
-* Adds support for "Conditional `GET`" so that server responds with nothing if page wasn't changed.
+* Adds support for "Conditional `GET`" so that server responds with nothing if the page wasn't changed.
 
 **`Rack::ETag`**
 
diff --git a/guides/source/security.md b/guides/source/security.md
index 2ac52155f8..eeb005b661 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -52,7 +52,7 @@ User.find(session[:user_id])
 
 NOTE: _The session ID is a 32-character random hex string._
 
-The session ID is generated using `SecureRandom.hex` which generates a random hex string using platform specific methods (such as OpenSSL, /dev/urandom or Win32) for generating cryptographically secure random numbers. Currently it is not feasible to brute-force Rails' session IDs.
+The session ID is generated using `SecureRandom.hex` which generates a random hex string using platform specific methods (such as OpenSSL, /dev/urandom or Win32 CryptoAPI) for generating cryptographically secure random numbers. Currently it is not feasible to brute-force Rails' session IDs.
 
 ### Session Hijacking
 
@@ -85,37 +85,117 @@ This will also be a good idea, if you modify the structure of an object and old
 
 * _Critical data should not be stored in session_. If the user clears their cookies or closes the browser, they will be lost. And with a client-side session storage, the user can read the data.
 
-### Session Storage
+### Encrypted Session Storage
 
 NOTE: _Rails provides several storage mechanisms for the session hashes. The most important is `ActionDispatch::Session::CookieStore`._
 
-Rails 2 introduced a new default session storage, CookieStore. CookieStore saves the session hash directly in a cookie on the client-side. The server retrieves the session hash from the cookie and eliminates the need for a session ID. That will greatly increase the speed of the application, but it is a controversial storage option and you have to think about the security implications of it:
+The `CookieStore` saves the session hash directly in a cookie on the
+client-side. The server retrieves the session hash from the cookie and
+eliminates the need for a session ID. That will greatly increase the
+speed of the application, but it is a controversial storage option and
+you have to think about the security implications and storage
+limitations of it:
+
+* Cookies imply a strict size limit of 4kB. This is fine as you should
+  not store large amounts of data in a session anyway, as described
+  before. Storing the current user's database id in a session is common
+  practice.
+
+* Session cookies do not invalidate themselves and can be maliciously
+  reused. It may be a good idea to have your application invalidate old
+  session cookies using a stored timestamp.
+
+The `CookieStore` uses the
+[encrypted](http://api.rubyonrails.org/classes/ActionDispatch/Cookies/ChainedCookieJars.html#method-i-encrypted)
+cookie jar to provide a secure, encrypted location to store session
+data. Cookie-based sessions thus provide both integrity as well as
+confidentiality to their contents. The encryption key, as well as the
+verification key used for
+[signed](http://api.rubyonrails.org/classes/ActionDispatch/Cookies/ChainedCookieJars.html#method-i-signed)
+cookies, is derived from the `secret_key_base` configuration value.
+
+As of Rails 5.2 encrypted cookies and sessions are protected using AES
+GCM encryption. This form of encryption is a type of Authenticated
+Encryption and couples authentication and encryption in single step
+while also producing shorter ciphertexts as compared to other
+algorithms previously used. The key for cookies encrypted with AES GCM
+are derived using a salt value defined by the
+`config.action_dispatch.authenticated_encrypted_cookie_salt`
+configuration value.
+
+Prior to this version, encrypted cookies were secured using AES in CBC
+mode with HMAC using SHA1 for authentication. The keys for this type of
+encryption and for HMAC verification were derived via the salts defined
+by `config.action_dispatch.encrypted_cookie_salt` and
+`config.action_dispatch.encrypted_signed_cookie_salt` respectively.
+
+Prior to Rails version 4 in both versions 2 and 3, session cookies were
+protected using only HMAC verification. As such, these session cookies
+only provided integrity to their content because the actual session data
+was stored in plaintext encoded as base64. This is how `signed` cookies
+work in the current version of Rails. These kinds of cookies are still
+useful for protecting the integrity of certain client-stored data and
+information.
+
+__Do not use a trivial secret for the `secret_key_base`, i.e. a word
+from a dictionary, or one which is shorter than 30 characters! Instead
+use `rails secret` to generate secret keys!__
+
+It is also important to use different salt values for encrypted and
+signed cookies. Using the same value for different salt configuration
+values may lead to the same derived key being used for different
+security features which in turn may weaken the strength of the key.
 
-* Cookies imply a strict size limit of 4kB. This is fine as you should not store large amounts of data in a session anyway, as described before. _Storing the current user's database id in a session is usually ok_.
+In test and development applications get a `secret_key_base` derived from the app name. Other environments must use a random key present in `config/credentials.yml.enc`, shown here in its decrypted state:
 
-* The client can see everything you store in a session, because it is stored in clear-text (actually Base64-encoded, so not encrypted). So, of course, _you don't want to store any secrets here_. To prevent session hash tampering, a digest is calculated from the session with a server-side secret (`secrets.secret_token`) and inserted into the end of the cookie.
+    secret_key_base: 492f...
 
-In Rails 4, encrypted cookies through AES in CBC mode with HMAC using SHA1 for
-verification was introduced. This prevents the user from accessing and tampering
-the content of the cookie. Thus the session becomes a more secure place to store
-data. The encryption is performed using a server-side `secret_key_base`.
-Two salts are used when deriving keys for encryption and verification. These
-salts are set via the `config.action_dispatch.encrypted_cookie_salt` and
-`config.action_dispatch.encrypted_signed_cookie_salt` configuration values.
+If you have received an application where the secret was exposed (e.g. an application whose source was shared), strongly consider changing the secret.
 
-Rails 5.2 uses AES-GCM for the encryption which couples authentication
-and encryption in one faster step and produces shorter ciphertexts.
+### Rotating Encrypted and Signed Cookies Configurations
 
-Encrypted cookies are automatically upgraded if the
-`config.action_dispatch.use_authenticated_cookie_encryption` is enabled.
+Rotation is ideal for changing cookie configurations and ensuring old cookies
+aren't immediately invalid. Your users then have a chance to visit your site,
+get their cookie read with an old configuration and have it rewritten with the
+new change. The rotation can then be removed once you're comfortable enough
+users have had their chance to get their cookies upgraded.
 
-_Do not use a trivial secret, i.e. a word from a dictionary, or one which is shorter than 30 characters! Instead use `rails secret` to generate secret keys!_
+It's possible to rotate the ciphers and digests used for encrypted and signed cookies.
 
-In test and development applications get a `secret_key_base` derived from the app name. Other environments must use a random key present in `config/credentials.yml.enc`, shown here in its decrypted state:
+For instance to change the digest used for signed cookies from SHA1 to SHA256,
+you would first assign the new configuration value:
 
-    secret_key_base: 492f...
+```ruby
+Rails.application.config.action_dispatch.signed_cookie_digest = "SHA256"
+```
 
-If you have received an application where the secret was exposed (e.g. an application whose source was shared), strongly consider changing the secret.
+Now add a rotation for the old SHA1 digest so existing cookies are
+seamlessly upgraded to the new SHA256 digest.
+
+```ruby
+Rails.application.config.action_dispatch.cookies_rotations.tap do |cookies|
+  cookies.rotate :signed, digest: "SHA1"
+end
+```
+
+Then any written signed cookies will be digested with SHA256. Old cookies
+that were written with SHA1 can still be read, and if accessed will be written
+with the new digest so they're upgraded and won't be invalid when you remove the
+rotation.
+
+Once users with SHA1 digested signed cookies should no longer have a chance to
+have their cookies rewritten, remove the rotation.
+
+While you can setup as many rotations as you'd like it's not common to have many
+rotations going at any one time.
+
+For more details on key rotation with encrypted and signed messages as
+well as the various options the `rotate` method accepts, please refer to
+the
+[MessageEncryptor API](http://api.rubyonrails.org/classes/ActiveSupport/MessageEncryptor.html)
+and
+[MessageVerifier API](http://api.rubyonrails.org/classes/ActiveSupport/MessageVerifier.html)
+documentation.
 
 ### Replay Attacks for CookieStore Sessions
 
@@ -456,7 +536,7 @@ Depending on your web application, there may be more ways to hijack the user's a
 
 INFO: _A CAPTCHA is a challenge-response test to determine that the response is not generated by a computer. It is often used to protect registration forms from attackers and comment forms from automatic spam bots by asking the user to type the letters of a distorted image. This is the positive CAPTCHA, but there is also the negative CAPTCHA. The idea of a negative CAPTCHA is not for a user to prove that they are human, but reveal that a robot is a robot._
 
-A popular positive CAPTCHA API is [reCAPTCHA](http://recaptcha.net/) which displays two distorted images of words from old books. It also adds an angled line, rather than a distorted background and high levels of warping on the text as earlier CAPTCHAs did, because the latter were broken. As a bonus, using reCAPTCHA helps to digitize old books. [ReCAPTCHA](https://github.com/ambethia/recaptcha/) is also a Rails plug-in with the same name as the API.
+A popular positive CAPTCHA API is [reCAPTCHA](https://developers.google.com/recaptcha/) which displays two distorted images of words from old books. It also adds an angled line, rather than a distorted background and high levels of warping on the text as earlier CAPTCHAs did, because the latter were broken. As a bonus, using reCAPTCHA helps to digitize old books. [ReCAPTCHA](https://github.com/ambethia/recaptcha/) is also a Rails plug-in with the same name as the API.
 
 You will get two keys from the API, a public and a private key, which you have to put into your Rails environment. After that you can use the recaptcha_tags method in the view, and the verify_recaptcha method in the controller. Verify_recaptcha will return false if the validation fails.
 The problem with CAPTCHAs is that they have a negative impact on the user experience. Additionally, some visually impaired users have found certain kinds of distorted CAPTCHAs difficult to read. Still, positive CAPTCHAs are one of the best methods to prevent all kinds of bots from submitting forms.
@@ -1029,7 +1109,7 @@ Rails generates a `config/credentials.yml.enc` to store third-party credentials
 within the repo. This is only viable because Rails encrypts the file with a master
 key that's generated into a version control ignored `config/master.key` — Rails
 will also look for that key in `ENV["RAILS_MASTER_KEY"]`. Rails also requires the
-the key to boot in production, so the credentials can be read.
+key to boot in production, so the credentials can be read.
 
 To edit stored credentials use `bin/rails credentials:edit`.
 
@@ -1049,7 +1129,7 @@ If you want an exception to be raised when some key is blank, use the bang
 version:
 
 ```ruby
-Rails.application.credentials.some_api_key! # => raises KeyError: key not found: :some_api_key
+Rails.application.credentials.some_api_key! # => raises KeyError: :some_api_key is blank
 ```
 
 Additional Resources
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 4ee3267261..f28c4c224a 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -319,6 +319,8 @@ specify to make your test failure messages clearer.
 | `assert_not_includes( collection, obj, [msg] )`                  | Ensures that `obj` is not in `collection`.|
 | `assert_in_delta( expected, actual, [delta], [msg] )`            | Ensures that the numbers `expected` and `actual` are within `delta` of each other.|
 | `assert_not_in_delta( expected, actual, [delta], [msg] )`        | Ensures that the numbers `expected` and `actual` are not within `delta` of each other.|
+| `assert_in_epsilon ( expected, actual, [epsilon], [msg] )`       | Ensures that the numbers `expected` and `actual` have a relative error less than `epsilon`.|
+| `assert_not_in_epsilon ( expected, actual, [epsilon], [msg] )`   | Ensures that the numbers `expected` and `actual` don't have a relative error less than `epsilon`.|
 | `assert_throws( symbol, [msg] ) { block }`                       | Ensures that the given block throws the symbol.|
 | `assert_raises( exception1, exception2, ... ) { block }`         | Ensures that the given block raises one of the given exceptions.|
 | `assert_instance_of( class, obj, [msg] )`                        | Ensures that `obj` is an instance of `class`.|
@@ -645,7 +647,7 @@ system tests should live.
 
 If you want to change the default settings you can change what the system
 tests are "driven by". Say you want to change the driver from Selenium to
-Poltergeist. First add the `poltergeist` gem to your Gemfile. Then in your
+Poltergeist. First add the `poltergeist` gem to your `Gemfile`. Then in your
 `application_system_test_case.rb` file do the following:
 
 ```ruby
@@ -671,6 +673,17 @@ class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
 end
 ```
 
+If you want to use a headless browser, you could use Headless Chrome or Headless Firefox by adding
+`headless_chrome` or `headless_firefox` in the `:using` argument.
+
+```ruby
+require "test_helper"
+
+class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :headless_chrome
+end
+```
+
 If your Capybara configuration requires more setup than provided by Rails, this
 additional configuration could be added into the `application_system_test_case.rb`
 file.
@@ -1513,7 +1526,7 @@ class BillingJobTest < ActiveJob::TestCase
 end
 ```
 
-This test is pretty simple and only asserts that the job get the work done
+This test is pretty simple and only asserts that the job got the work done
 as expected.
 
 By default, `ActiveJob::TestCase` will set the queue adapter to `:test` so that
diff --git a/guides/source/threading_and_code_execution.md b/guides/source/threading_and_code_execution.md
new file mode 100644
index 0000000000..3d3d31b97e
--- /dev/null
+++ b/guides/source/threading_and_code_execution.md
@@ -0,0 +1,324 @@
+**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
+
+Threading and Code Execution in Rails
+=====================================
+
+After reading this guide, you will know:
+
+* What code Rails will automatically execute concurrently
+* How to integrate manual concurrency with Rails internals
+* How to wrap all application code
+* How to affect application reloading
+
+--------------------------------------------------------------------------------
+
+Automatic Concurrency
+---------------------
+
+Rails automatically allows various operations to be performed at the same time.
+
+When using a threaded web server, such as the default Puma, multiple HTTP
+requests will be served simultaneously, with each request provided its own
+controller instance.
+
+Threaded Active Job adapters, including the built-in Async, will likewise
+execute several jobs at the same time. Action Cable channels are managed this
+way too.
+
+These mechanisms all involve multiple threads, each managing work for a unique
+instance of some object (controller, job, channel), while sharing the global
+process space (such as classes and their configurations, and global variables).
+As long as your code doesn't modify any of those shared things, it can mostly
+ignore that other threads exist.
+
+The rest of this guide describes the mechanisms Rails uses to make it "mostly
+ignorable", and how extensions and applications with special needs can use them.
+
+Executor
+--------
+
+The Rails Executor separates application code from framework code: any time the
+framework invokes code you've written in your application, it will be wrapped by
+the Executor.
+
+The Executor consists of two callbacks: `to_run` and `to_complete`. The Run
+callback is called before the application code, and the Complete callback is
+called after.
+
+### Default callbacks
+
+In a default Rails application, the Executor callbacks are used to:
+
+* track which threads are in safe positions for autoloading and reloading
+* enable and disable the Active Record query cache
+* return acquired Active Record connections to the pool
+* constrain internal cache lifetimes
+
+Prior to Rails 5.0, some of these were handled by separate Rack middleware
+classes (such as `ActiveRecord::ConnectionAdapters::ConnectionManagement`), or
+directly wrapping code with methods like
+`ActiveRecord::Base.connection_pool.with_connection`. The Executor replaces
+these with a single more abstract interface.
+
+### Wrapping application code
+
+If you're writing a library or component that will invoke application code, you
+should wrap it with a call to the executor:
+
+```ruby
+Rails.application.executor.wrap do
+  # call application code here
+end
+```
+
+TIP: If you repeatedly invoke application code from a long-running process, you
+may want to wrap using the Reloader instead.
+
+Each thread should be wrapped before it runs application code, so if your
+application manually delegates work to other threads, such as via `Thread.new`
+or Concurrent Ruby features that use thread pools, you should immediately wrap
+the block:
+
+```ruby
+Thread.new do
+  Rails.application.executor.wrap do
+    # your code here
+  end
+end
+```
+
+NOTE: Concurrent Ruby uses a `ThreadPoolExecutor`, which it sometimes configures
+with an `executor` option. Despite the name, it is unrelated.
+
+The Executor is safely re-entrant; if it is already active on the current
+thread, `wrap` is a no-op.
+
+If it's impractical to wrap the application code in a block (for
+example, the Rack API makes this problematic), you can also use the `run!` /
+`complete!` pair:
+
+```ruby
+Thread.new do
+  execution_context = Rails.application.executor.run!
+  # your code here
+ensure
+  execution_context.complete! if execution_context
+end
+```
+
+### Concurrency
+
+The Executor will put the current thread into `running` mode in the Load
+Interlock. This operation will block temporarily if another thread is currently
+either autoloading a constant or unloading/reloading the application.
+
+Reloader
+--------
+
+Like the Executor, the Reloader also wraps application code. If the Executor is
+not already active on the current thread, the Reloader will invoke it for you,
+so you only need to call one. This also guarantees that everything the Reloader
+does, including all its callback invocations, occurs wrapped inside the
+Executor.
+
+```ruby
+Rails.application.reloader.wrap do
+  # call application code here
+end
+```
+
+The Reloader is only suitable where a long-running framework-level process
+repeatedly calls into application code, such as for a web server or job queue.
+Rails automatically wraps web requests and Active Job workers, so you'll rarely
+need to invoke the Reloader for yourself. Always consider whether the Executor
+is a better fit for your use case.
+
+### Callbacks
+
+Before entering the wrapped block, the Reloader will check whether the running
+application needs to be reloaded -- for example, because a model's source file has
+been modified. If it determines a reload is required, it will wait until it's
+safe, and then do so, before continuing. When the application is configured to
+always reload regardless of whether any changes are detected, the reload is
+instead performed at the end of the block.
+
+The Reloader also provides `to_run` and `to_complete` callbacks; they are
+invoked at the same points as those of the Executor, but only when the current
+execution has initiated an application reload. When no reload is deemed
+necessary, the Reloader will invoke the wrapped block with no other callbacks.
+
+### Class Unload
+
+The most significant part of the reloading process is the Class Unload, where
+all autoloaded classes are removed, ready to be loaded again. This will occur
+immediately before either the Run or Complete callback, depending on the
+`reload_classes_only_on_change` setting.
+
+Often, additional reloading actions need to be performed either just before or
+just after the Class Unload, so the Reloader also provides `before_class_unload`
+and `after_class_unload` callbacks.
+
+### Concurrency
+
+Only long-running "top level" processes should invoke the Reloader, because if
+it determines a reload is needed, it will block until all other threads have
+completed any Executor invocations.
+
+If this were to occur in a "child" thread, with a waiting parent inside the
+Executor, it would cause an unavoidable deadlock: the reload must occur before
+the child thread is executed, but it cannot be safely performed while the parent
+thread is mid-execution. Child threads should use the Executor instead.
+
+Framework Behavior
+------------------
+
+The Rails framework components use these tools to manage their own concurrency
+needs too.
+
+`ActionDispatch::Executor` and `ActionDispatch::Reloader` are Rack middlewares
+that wraps the request with a supplied Executor or Reloader, respectively. They
+are automatically included in the default application stack. The Reloader will
+ensure any arriving HTTP request is served with a freshly-loaded copy of the
+application if any code changes have occurred.
+
+Active Job also wraps its job executions with the Reloader, loading the latest
+code to execute each job as it comes off the queue.
+
+Action Cable uses the Executor instead: because a Cable connection is linked to
+a specific instance of a class, it's not possible to reload for every arriving
+websocket message. Only the message handler is wrapped, though; a long-running
+Cable connection does not prevent a reload that's triggered by a new incoming
+request or job. Instead, Action Cable uses the Reloader's `before_class_unload`
+callback to disconnect all its connections. When the client automatically
+reconnects, it will be speaking to the new version of the code.
+
+The above are the entry points to the framework, so they are responsible for
+ensuring their respective threads are protected, and deciding whether a reload
+is necessary. Other components only need to use the Executor when they spawn
+additional threads.
+
+### Configuration
+
+The Reloader only checks for file changes when `cache_classes` is false and
+`reload_classes_only_on_change` is true (which is the default in the
+`development` environment).
+
+When `cache_classes` is true (in `production`, by default), the Reloader is only
+a pass-through to the Executor.
+
+The Executor always has important work to do, like database connection
+management. When `cache_classes` and `eager_load` are both true (`production`),
+no autoloading or class reloading will occur, so it does not need the Load
+Interlock. If either of those are false (`development`), then the Executor will
+use the Load Interlock to ensure constants are only loaded when it is safe.
+
+Load Interlock
+--------------
+
+The Load Interlock allows autoloading and reloading to be enabled in a
+multi-threaded runtime environment.
+
+When one thread is performing an autoload by evaluating the class definition
+from the appropriate file, it is important no other thread encounters a
+reference to the partially-defined constant.
+
+Similarly, it is only safe to perform an unload/reload when no application code
+is in mid-execution: after the reload, the `User` constant, for example, may
+point to a different class. Without this rule, a poorly-timed reload would mean
+`User.new.class == User`, or even `User == User`, could be false.
+
+Both of these constraints are addressed by the Load Interlock. It keeps track of
+which threads are currently running application code, loading a class, or
+unloading autoloaded constants.
+
+Only one thread may load or unload at a time, and to do either, it must wait
+until no other threads are running application code. If a thread is waiting to
+perform a load, it doesn't prevent other threads from loading (in fact, they'll
+cooperate, and each perform their queued load in turn, before all resuming
+running together).
+
+### `permit_concurrent_loads`
+
+The Executor automatically acquires a `running` lock for the duration of its
+block, and autoload knows when to upgrade to a `load` lock, and switch back to
+`running` again afterwards.
+
+Other blocking operations performed inside the Executor block (which includes
+all application code), however, can needlessly retain the `running` lock. If
+another thread encounters a constant it must autoload, this can cause a
+deadlock.
+
+For example, assuming `User` is not yet loaded, the following will deadlock:
+
+```ruby
+Rails.application.executor.wrap do
+  th = Thread.new do
+    Rails.application.executor.wrap do
+      User # inner thread waits here; it cannot load
+           # User while another thread is running
+    end
+  end
+
+  th.join # outer thread waits here, holding 'running' lock
+end
+```
+
+To prevent this deadlock, the outer thread can `permit_concurrent_loads`. By
+calling this method, the thread guarantees it will not dereference any
+possibly-autoloaded constant inside the supplied block. The safest way to meet
+that promise is to put it as close as possible to the blocking call:
+
+```ruby
+Rails.application.executor.wrap do
+  th = Thread.new do
+    Rails.application.executor.wrap do
+      User # inner thread can acquire the load lock,
+           # load User, and continue
+    end
+  end
+
+  ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
+    th.join # outer thread waits here, but has no lock
+  end
+end
+```
+
+Another example, using Concurrent Ruby:
+
+```ruby
+Rails.application.executor.wrap do
+  futures = 3.times.collect do |i|
+    Concurrent::Future.execute do
+      Rails.application.executor.wrap do
+        # do work here
+      end
+    end
+  end
+
+  values = ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
+    futures.collect(&:value)
+  end
+end
+```
+
+
+### ActionDispatch::DebugLocks
+
+If your application is deadlocking and you think the Load Interlock may be
+involved, you can temporarily add the ActionDispatch::DebugLocks middleware to
+`config/application.rb`:
+
+```ruby
+config.middleware.insert_before Rack::Sendfile,
+                                  ActionDispatch::DebugLocks
+```
+
+If you then restart the application and re-trigger the deadlock condition,
+`/rails/locks` will show a summary of all threads currently known to the
+interlock, which lock level they are holding or awaiting, and their current
+backtrace.
+
+Generally a deadlock will be caused by the interlock conflicting with some other
+external lock or blocking I/O call. Once you find it, you can wrap it with
+`permit_concurrent_loads`.
+
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index d932fc8d8f..eae73c3e1b 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -27,7 +27,7 @@ The process should go as follows:
 3. Fix tests and deprecated features.
 4. Move to the latest patch version of the next minor version.
 
-Repeat this process until you reach your target Rails version. Each time you move versions, you will need to change the Rails version number in the Gemfile (and possibly other gem versions) and run `bundle update`. Then run the Update task mentioned below to update configuration files, then run your tests.
+Repeat this process until you reach your target Rails version. Each time you move versions, you will need to change the Rails version number in the `Gemfile` (and possibly other gem versions) and run `bundle update`. Then run the Update task mentioned below to update configuration files, then run your tests.
 
 You can find a list of all released Rails versions [here](https://rubygems.org/gems/rails/versions).
 
@@ -45,7 +45,7 @@ TIP: Ruby 1.8.7 p248 and p249 have marshaling bugs that crash Rails. Ruby Enterp
 ### The Update Task
 
 Rails provides the `app:update` task (`rake rails:update` on 4.2 and earlier). After updating the Rails version
-in the Gemfile, run this task.
+in the `Gemfile`, run this task.
 This will help you with the creation of new files and changes of old files in an
 interactive session.
 
@@ -179,7 +179,7 @@ See [#19034](https://github.com/rails/rails/pull/19034) for more details.
 
 `assigns` and `assert_template` have been extracted to the `rails-controller-testing` gem. To
 continue using these methods in your controller tests, add `gem 'rails-controller-testing'` to
-your Gemfile.
+your `Gemfile`.
 
 If you are using Rspec for testing, please see the extra configuration required in the gem's
 documentation.
@@ -212,7 +212,7 @@ true.
 
 `ActiveModel::Serializers::Xml` has been extracted from Rails to the `activemodel-serializers-xml`
 gem. To continue using XML serialization in your application, add `gem 'activemodel-serializers-xml'`
-to your Gemfile.
+to your `Gemfile`.
 
 ### Removed Support for Legacy `mysql` Database Adapter
 
@@ -278,7 +278,7 @@ You can now just call the dependency once with a wildcard.
 
 ### `ActionView::Helpers::RecordTagHelper` moved to external gem (record_tag_helper)
 
-`content_tag_for` and `div_for` have been removed in favor of just using `content_tag`. To continue using the older methods, add the `record_tag_helper` gem to your Gemfile:
+`content_tag_for` and `div_for` have been removed in favor of just using `content_tag`. To continue using the older methods, add the `record_tag_helper` gem to your `Gemfile`:
 
 ```ruby
 gem 'record_tag_helper', '~> 1.0'
@@ -411,11 +411,11 @@ Upgrading from Rails 4.1 to Rails 4.2
 
 ### Web Console
 
-First, add `gem 'web-console', '~> 2.0'` to the `:development` group in your Gemfile and run `bundle install` (it won't have been included when you upgraded Rails). Once it's been installed, you can simply drop a reference to the console helper (i.e., `<%= console %>`) into any view you want to enable it for. A console will also be provided on any error page you view in your development environment.
+First, add `gem 'web-console', '~> 2.0'` to the `:development` group in your `Gemfile` and run `bundle install` (it won't have been included when you upgraded Rails). Once it's been installed, you can simply drop a reference to the console helper (i.e., `<%= console %>`) into any view you want to enable it for. A console will also be provided on any error page you view in your development environment.
 
 ### Responders
 
-`respond_with` and the class-level `respond_to` methods have been extracted to the `responders` gem. To use them, simply add `gem 'responders', '~> 2.0'` to your Gemfile. Calls to `respond_with` and `respond_to` (again, at the class level) will no longer work without having included the `responders` gem in your dependencies:
+`respond_with` and the class-level `respond_to` methods have been extracted to the `responders` gem. To use them, simply add `gem 'responders', '~> 2.0'` to your `Gemfile`. Calls to `respond_with` and `respond_to` (again, at the class level) will no longer work without having included the `responders` gem in your dependencies:
 
 ```ruby
 # app/controllers/users_controller.rb
@@ -559,7 +559,7 @@ Read the [gem's readme](https://github.com/rails/rails-html-sanitizer) for more
 The documentation for `PermitScrubber` and `TargetScrubber` explains how you
 can gain complete control over when and how elements should be stripped.
 
-If your application needs to use the old sanitizer implementation, include `rails-deprecated_sanitizer` in your Gemfile:
+If your application needs to use the old sanitizer implementation, include `rails-deprecated_sanitizer` in your `Gemfile`:
 
 ```ruby
 gem 'rails-deprecated_sanitizer'
@@ -617,7 +617,7 @@ migration DSL counterpart.
 
 The migration procedure is as follows:
 
-1. remove `gem "foreigner"` from the Gemfile.
+1. remove `gem "foreigner"` from the `Gemfile`.
 2. run `bundle install`.
 3. run `bin/rake db:schema:dump`.
 4. make sure that `db/schema.rb` contains every foreign key definition with
@@ -769,7 +769,7 @@ and has been removed from Rails.
 
 If your application currently depends on MultiJSON directly, you have a few options:
 
-1. Add 'multi_json' to your Gemfile. Note that this might cease to work in the future
+1. Add 'multi_json' to your `Gemfile`. Note that this might cease to work in the future
 
 2. Migrate away from MultiJSON by using `obj.to_json`, and `JSON.parse(str)` instead.
 
@@ -810,7 +810,7 @@ part of the rewrite, the following features have been removed from the encoder:
 
 If your application depends on one of these features, you can get them back by
 adding the [`activesupport-json_encoder`](https://github.com/rails/activesupport-json_encoder)
-gem to your Gemfile.
+gem to your `Gemfile`.
 
 #### JSON representation of Time objects
 
@@ -1135,8 +1135,8 @@ full support for the last few changes in the specification.
 
 ### Gemfile
 
-Rails 4.0 removed the `assets` group from Gemfile. You'd need to remove that
-line from your Gemfile when upgrading. You should also update your application
+Rails 4.0 removed the `assets` group from `Gemfile`. You'd need to remove that
+line from your `Gemfile` when upgrading. You should also update your application
 file (in `config/application.rb`):
 
 ```ruby
@@ -1147,7 +1147,7 @@ Bundler.require(*Rails.groups)
 
 ### vendor/plugins
 
-Rails 4.0 no longer supports loading plugins from `vendor/plugins`. You must replace any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
+Rails 4.0 no longer supports loading plugins from `vendor/plugins`. You must replace any plugins by extracting them to gems and adding them to your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
 
 ### Active Record
 
@@ -1214,7 +1214,7 @@ end
 
 ### Active Resource
 
-Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the [Active Resource gem](https://github.com/rails/activeresource) in your Gemfile.
+Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the [Active Resource gem](https://github.com/rails/activeresource) in your `Gemfile`.
 
 ### Active Model
 
@@ -1414,7 +1414,7 @@ config.active_record.mass_assignment_sanitizer = :strict
 
 ### vendor/plugins
 
-Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. While it's not strictly necessary as part of a Rails 3.2 upgrade, you can start replacing any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
+Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. While it's not strictly necessary as part of a Rails 3.2 upgrade, you can start replacing any plugins by extracting them to gems and adding them to your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
 
 ### Active Record
 
diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md
index 27cef2bd27..c3dff1772c 100644
--- a/guides/source/working_with_javascript_in_rails.md
+++ b/guides/source/working_with_javascript_in_rails.md
@@ -174,7 +174,7 @@ passing the `:local` option `form_with`.
 This will generate the following HTML:
 
 ```html
-<form action="/articles" method="post" data-remote="true">
+<form action="/articles" accept-charset="UTF-8" method="post" data-remote="true">
   ...
 </form>
 ```
@@ -188,15 +188,20 @@ bind to the `ajax:success` event. On failure, use `ajax:error`. Check it out:
 
 ```coffeescript
 $(document).ready ->
-  $("#new_article").on("ajax:success", (e, data, status, xhr) ->
+  $("#new_article").on("ajax:success", (event) ->
+    [data, status, xhr] = event.detail
     $("#new_article").append xhr.responseText
-  ).on "ajax:error", (e, xhr, status, error) ->
+  ).on "ajax:error", (event) ->
     $("#new_article").append "<p>ERROR</p>"
 ```
 
 Obviously, you'll want to be a bit more sophisticated than that, but it's a
 start.
 
+NOTE: As of Rails 5.1 and the new `rails-ujs`, the parameters `data, status, xhr`
+have been bundled into `event.detail`. For information about the previously used
+`jquery-ujs` in Rails 5 and earlier, read the [`jquery-ujs` wiki](https://github.com/rails/jquery-ujs/wiki/ajax).
+
 #### link_to
 
 [`link_to`](http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to)
@@ -225,7 +230,7 @@ and write some CoffeeScript like this:
 
 ```coffeescript
 $ ->
-  $("a[data-remote]").on "ajax:success", (e, data, status, xhr) ->
+  $("a[data-remote]").on "ajax:success", (event) ->
     alert "The article was deleted."
 ```
 
@@ -343,46 +348,13 @@ This generates a form with:
 <input data-disable-with="Saving..." type="submit">
 ```
 
-Dealing with Ajax events
-------------------------
-
-Here are the different events that are fired when you deal with elements
-that have a `data-remote` attribute:
-
-NOTE: All handlers bound to these events are always passed the event object as the
-first argument. The table below describes the extra parameters passed after the
-event argument. For example, if the extra parameters are listed as `xhr, settings`,
-then to access them, you would define your handler with `function(event, xhr, settings)`.
-
-| Event name          | Extra parameters | Fired                                                       |
-|---------------------|------------------|-------------------------------------------------------------|
-| `ajax:before`       |                  | Before the whole ajax business, aborts if stopped.          |
-| `ajax:beforeSend`   | xhr, options     | Before the request is sent, aborts if stopped.              |
-| `ajax:send`         | xhr              | When the request is sent.                                   |
-| `ajax:success`      | xhr, status, err | After completion, if the response was a success.            |
-| `ajax:error`        | xhr, status, err | After completion, if the response was an error.             |
-| `ajax:complete`     | xhr, status      | After the request has been completed, no matter the outcome.|
-| `ajax:aborted:file` | elements         | If there are non-blank file inputs, aborts if stopped.      |
-
-### Stoppable events
-
-If you stop `ajax:before` or `ajax:beforeSend` by returning false from the
-handler method, the Ajax request will never take place. The `ajax:before` event
-is also useful for manipulating form data before serialization. The
-`ajax:beforeSend` event is also useful for adding custom request headers.
-
-If you stop the `ajax:aborted:file` event, the default behavior of allowing the
-browser to submit the form via normal means (i.e. non-Ajax submission) will be
-canceled and the form will not be submitted at all. This is useful for
-implementing your own Ajax file upload workaround.
-
 ### Rails-ujs event handlers
 
 Rails 5.1 introduced rails-ujs and dropped jQuery as a dependency.
 As a result the Unobtrusive JavaScript (UJS) driver has been rewritten to operate without jQuery.
 These introductions cause small changes to `custom events` fired during the request:
 
-NOTE: Signature of calls to UJS’s event handlers has changed.
+NOTE: Signature of calls to UJS's event handlers has changed.
 Unlike the version with jQuery, all custom events return only one parameter: `event`.
 In this parameter, there is an additional attribute `detail` which contains an array of extra parameters.
 
@@ -405,6 +377,22 @@ document.body.addEventListener('ajax:success', function(event) {
 })
 ```
 
+NOTE: As of Rails 5.1 and the new `rails-ujs`, the parameters `data, status, xhr`
+have been bundled into `event.detail`. For information about the previously used
+`jquery-ujs` in Rails 5 and earlier, read the [`jquery-ujs` wiki](https://github.com/rails/jquery-ujs/wiki/ajax).
+
+### Stoppable events
+
+If you stop `ajax:before` or `ajax:beforeSend` by returning false from the
+handler method, the Ajax request will never take place. The `ajax:before` event
+can manipulate form data before serialization and the
+`ajax:beforeSend` event is useful for adding custom request headers.
+
+If you stop the `ajax:aborted:file` event, the default behavior of allowing the
+browser to submit the form via normal means (i.e. non-Ajax submission) will be
+canceled and the form will not be submitted at all. This is useful for
+implementing your own Ajax file upload workaround.
+
 Server-Side Concerns
 --------------------
 
@@ -504,7 +492,7 @@ replace the entire `<body>` of the page with the `<body>` of the response. It
 will then use PushState to change the URL to the correct one, preserving
 refresh semantics and giving you pretty URLs.
 
-The only thing you have to do to enable Turbolinks is have it in your Gemfile,
+The only thing you have to do to enable Turbolinks is have it in your `Gemfile`,
 and put `//= require turbolinks` in your JavaScript manifest, which is usually
 `app/assets/javascripts/application.js`.
 
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 5057059898..70c0f5c67b 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,28 @@
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Deprecate `after_bundle` callback in Rails plugin templates.
+
+    *Yuji Yaginuma*
+
+*   `rails new` and `rails plugin new` get `Active Storage` by default.
+     Add ability to skip `Active Storage` with `--skip-active-storage`
+     and do so automatically when `--skip-active-record` is used.
+
+    *bogdanvlviv*
+
+*   Gemfile for new apps: upgrade redis-rb from ~> 3.0 to 4.0.
+
+    *Jeremy Daer*
+
+*   Add `mini_magick` to default `Gemfile` as comment.
+
+    *Yoshiyuki Hirano*
+
 *   Derive `secret_key_base` from the app name in development and test environments.
 
     Spares away needless secret configs.
diff --git a/railties/lib/rails.rb b/railties/lib/rails.rb
index 04bb9ba94a..092105d502 100644
--- a/railties/lib/rails.rb
+++ b/railties/lib/rails.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "rails/ruby_version_check"
+require "rails/ruby_version_check"
 
 require "pathname"
 
@@ -11,8 +11,8 @@ require "active_support/core_ext/module/delegation"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/object/blank"
 
-require_relative "rails/application"
-require_relative "rails/version"
+require "rails/application"
+require "rails/version"
 
 require "active_support/railtie"
 require "action_dispatch/railtie"
@@ -50,7 +50,7 @@ module Rails
     def backtrace_cleaner
       @backtrace_cleaner ||= begin
         # Relies on Active Support, so we have to lazy load to postpone definition until Active Support has been loaded
-        require_relative "rails/backtrace_cleaner"
+        require "rails/backtrace_cleaner"
         Rails::BacktraceCleaner.new
       end
     end
diff --git a/railties/lib/rails/all.rb b/railties/lib/rails/all.rb
index e55b2e2433..f5dccd2381 100644
--- a/railties/lib/rails/all.rb
+++ b/railties/lib/rails/all.rb
@@ -4,12 +4,12 @@ require "rails"
 
 %w(
   active_record/railtie
+  active_storage/engine
   action_controller/railtie
   action_view/railtie
   action_mailer/railtie
   active_job/railtie
   action_cable/engine
-  active_storage/engine
   rails/test_unit/railtie
   sprockets/railtie
 ).each do |railtie|
diff --git a/railties/lib/rails/api/task.rb b/railties/lib/rails/api/task.rb
index 184f5b14f1..e7f0557584 100644
--- a/railties/lib/rails/api/task.rb
+++ b/railties/lib/rails/api/task.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "rdoc/task"
-require_relative "generator"
+require "rails/api/generator"
 
 module Rails
   module API
diff --git a/railties/lib/rails/app_loader.rb b/railties/lib/rails/app_loader.rb
index 3e9b3bd4bb..20eb75d95c 100644
--- a/railties/lib/rails/app_loader.rb
+++ b/railties/lib/rails/app_loader.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "pathname"
-require_relative "version"
+require "rails/version"
 
 module Rails
   module AppLoader # :nodoc:
@@ -56,7 +56,7 @@ EOS
             $stderr.puts(BUNDLER_WARNING)
             Object.const_set(:APP_PATH, File.expand_path("config/application", Dir.pwd))
             require File.expand_path("../boot", APP_PATH)
-            require_relative "commands"
+            require "rails/commands"
             break
           end
         end
diff --git a/railties/lib/rails/app_updater.rb b/railties/lib/rails/app_updater.rb
index c2436a69f9..a076d082d5 100644
--- a/railties/lib/rails/app_updater.rb
+++ b/railties/lib/rails/app_updater.rb
@@ -21,11 +21,12 @@ module Rails
       private
         def generator_options
           options = { api: !!Rails.application.config.api_only, update: true }
-          options[:skip_active_record] = !defined?(ActiveRecord::Railtie)
-          options[:skip_action_mailer] = !defined?(ActionMailer::Railtie)
-          options[:skip_action_cable]  = !defined?(ActionCable::Engine)
-          options[:skip_sprockets]     = !defined?(Sprockets::Railtie)
-          options[:skip_puma]          = !defined?(Puma)
+          options[:skip_active_record]  = !defined?(ActiveRecord::Railtie)
+          options[:skip_active_storage] = !defined?(ActiveStorage::Engine) || !defined?(ActiveRecord::Railtie)
+          options[:skip_action_mailer]  = !defined?(ActionMailer::Railtie)
+          options[:skip_action_cable]   = !defined?(ActionCable::Engine)
+          options[:skip_sprockets]      = !defined?(Sprockets::Railtie)
+          options[:skip_puma]           = !defined?(Puma)
           options
         end
     end
diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index abfec90b6d..293a736bfd 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -6,8 +6,9 @@ require "active_support/core_ext/object/blank"
 require "active_support/key_generator"
 require "active_support/message_verifier"
 require "active_support/encrypted_configuration"
-require_relative "engine"
-require_relative "secrets"
+require "active_support/deprecation"
+require "rails/engine"
+require "rails/secrets"
 
 module Rails
   # An Engine with the responsibility of coordinating the whole boot process.
@@ -173,8 +174,9 @@ module Rails
       # team. Details at https://github.com/rails/rails/pull/6952#issuecomment-7661220
       @caching_key_generator ||=
         if secret_key_base
-          ActiveSupport::CachingKeyGenerator.new \
+          ActiveSupport::CachingKeyGenerator.new(
             ActiveSupport::KeyGenerator.new(secret_key_base, iterations: 1000)
+          )
         else
           ActiveSupport::LegacyKeyGenerator.new(secrets.secret_token)
         end
@@ -259,8 +261,14 @@ module Rails
           "action_dispatch.encrypted_cookie_salt" => config.action_dispatch.encrypted_cookie_salt,
           "action_dispatch.encrypted_signed_cookie_salt" => config.action_dispatch.encrypted_signed_cookie_salt,
           "action_dispatch.authenticated_encrypted_cookie_salt" => config.action_dispatch.authenticated_encrypted_cookie_salt,
+          "action_dispatch.use_authenticated_cookie_encryption" => config.action_dispatch.use_authenticated_cookie_encryption,
+          "action_dispatch.encrypted_cookie_cipher" => config.action_dispatch.encrypted_cookie_cipher,
+          "action_dispatch.signed_cookie_digest" => config.action_dispatch.signed_cookie_digest,
           "action_dispatch.cookies_serializer" => config.action_dispatch.cookies_serializer,
-          "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest
+          "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest,
+          "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations,
+          "action_dispatch.content_security_policy" => config.content_security_policy,
+          "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only
         )
       end
     end
@@ -394,6 +402,12 @@ module Rails
         # Fallback to config.secret_token if secrets.secret_token isn't set
         secrets.secret_token ||= config.secret_token
 
+        if secrets.secret_token.present?
+          ActiveSupport::Deprecation.warn(
+            "`secrets.secret_token` is deprecated in favor of `secret_key_base` and will be removed in Rails 6.0."
+          )
+        end
+
         secrets
       end
     end
@@ -414,19 +428,52 @@ module Rails
       if Rails.env.test? || Rails.env.development?
         Digest::MD5.hexdigest self.class.name
       else
-        validate_secret_key_base \
+        validate_secret_key_base(
           ENV["SECRET_KEY_BASE"] || credentials.secret_key_base || secrets.secret_key_base
+        )
       end
     end
 
-    # Decrypts the credentials hash as kept in `config/credentials.yml.enc`. This file is encrypted with
-    # the Rails master key, which is either taken from ENV["RAILS_MASTER_KEY"] or from loading
-    # `config/master.key`.
+    # Decrypts the credentials hash as kept in +config/credentials.yml.enc+. This file is encrypted with
+    # the Rails master key, which is either taken from <tt>ENV["RAILS_MASTER_KEY"]</tt> or from loading
+    # +config/master.key+.
     def credentials
-      @credentials ||= ActiveSupport::EncryptedConfiguration.new \
-        config_path: Rails.root.join("config/credentials.yml.enc"),
-        key_path: Rails.root.join("config/master.key"),
-        env_key: "RAILS_MASTER_KEY"
+      @credentials ||= encrypted("config/credentials.yml.enc")
+    end
+
+    # Shorthand to decrypt any encrypted configurations or files.
+    #
+    # For any file added with <tt>bin/rails encrypted:edit</tt> call +read+ to decrypt
+    # the file with the master key.
+    # The master key is either stored in +config/master.key+ or <tt>ENV["RAILS_MASTER_KEY"]</tt>.
+    #
+    #   Rails.application.encrypted("config/mystery_man.txt.enc").read
+    #   # => "We've met before, haven't we?"
+    #
+    # It's also possible to interpret encrypted YAML files with +config+.
+    #
+    #   Rails.application.encrypted("config/credentials.yml.enc").config
+    #   # => { next_guys_line: "I don't think so. Where was it you think we met?" }
+    #
+    # Any top-level configs are also accessible directly on the return value:
+    #
+    #   Rails.application.encrypted("config/credentials.yml.enc").next_guys_line
+    #   # => "I don't think so. Where was it you think we met?"
+    #
+    # The files or configs can also be encrypted with a custom key. To decrypt with
+    # a key in the +ENV+, use:
+    #
+    #   Rails.application.encrypted("config/special_tokens.yml.enc", env_key: "SPECIAL_TOKENS")
+    #
+    # Or to decrypt with a file, that should be version control ignored, relative to +Rails.root+:
+    #
+    #   Rails.application.encrypted("config/special_tokens.yml.enc", key_path: "config/special_tokens.key")
+    def encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")
+      ActiveSupport::EncryptedConfiguration.new(
+        config_path: Rails.root.join(path),
+        key_path: Rails.root.join(key_path),
+        env_key: env_key
+      )
     end
 
     def to_app #:nodoc:
@@ -464,7 +511,7 @@ module Rails
     def run_tasks_blocks(app) #:nodoc:
       railties.each { |r| r.run_tasks_blocks(app) }
       super
-      require_relative "tasks"
+      require "rails/tasks"
       task :environment do
         ActiveSupport.on_load(:before_initialize) { config.eager_load = false }
 
diff --git a/railties/lib/rails/application/bootstrap.rb b/railties/lib/rails/application/bootstrap.rb
index c24d4573a9..e3c0759f95 100644
--- a/railties/lib/rails/application/bootstrap.rb
+++ b/railties/lib/rails/application/bootstrap.rb
@@ -4,7 +4,7 @@ require "fileutils"
 require "active_support/notifications"
 require "active_support/dependencies"
 require "active_support/descendants_tracker"
-require_relative "../secrets"
+require "rails/secrets"
 
 module Rails
   class Application
diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index b65289177f..cbc04f8a48 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -2,8 +2,8 @@
 
 require "active_support/core_ext/kernel/reporting"
 require "active_support/file_update_checker"
-require_relative "../engine/configuration"
-require_relative "../source_annotation_extractor"
+require "rails/engine/configuration"
+require "rails/source_annotation_extractor"
 
 module Rails
   class Application
@@ -16,44 +16,46 @@ module Rails
                     :ssl_options, :public_file_server,
                     :session_options, :time_zone, :reload_classes_only_on_change,
                     :beginning_of_week, :filter_redirect, :x, :enable_dependency_loading,
-                    :read_encrypted_secrets, :log_level
+                    :read_encrypted_secrets, :log_level, :content_security_policy_report_only
 
       attr_reader :encoding, :api_only
 
       def initialize(*)
         super
-        self.encoding                    = Encoding::UTF_8
-        @allow_concurrency               = nil
-        @consider_all_requests_local     = false
-        @filter_parameters               = []
-        @filter_redirect                 = []
-        @helpers_paths                   = []
-        @public_file_server              = ActiveSupport::OrderedOptions.new
-        @public_file_server.enabled      = true
-        @public_file_server.index_name   = "index"
-        @force_ssl                       = false
-        @ssl_options                     = {}
-        @session_store                   = nil
-        @time_zone                       = "UTC"
-        @beginning_of_week               = :monday
-        @log_level                       = :debug
-        @generators                      = app_generators
-        @cache_store                     = [ :file_store, "#{root}/tmp/cache/" ]
-        @railties_order                  = [:all]
-        @relative_url_root               = ENV["RAILS_RELATIVE_URL_ROOT"]
-        @reload_classes_only_on_change   = true
-        @file_watcher                    = ActiveSupport::FileUpdateChecker
-        @exceptions_app                  = nil
-        @autoflush_log                   = true
-        @log_formatter                   = ActiveSupport::Logger::SimpleFormatter.new
-        @eager_load                      = nil
-        @secret_token                    = nil
-        @secret_key_base                 = nil
-        @api_only                        = false
-        @debug_exception_response_format = nil
-        @x                               = Custom.new
-        @enable_dependency_loading       = false
-        @read_encrypted_secrets          = false
+        self.encoding                        = Encoding::UTF_8
+        @allow_concurrency                   = nil
+        @consider_all_requests_local         = false
+        @filter_parameters                   = []
+        @filter_redirect                     = []
+        @helpers_paths                       = []
+        @public_file_server                  = ActiveSupport::OrderedOptions.new
+        @public_file_server.enabled          = true
+        @public_file_server.index_name       = "index"
+        @force_ssl                           = false
+        @ssl_options                         = {}
+        @session_store                       = nil
+        @time_zone                           = "UTC"
+        @beginning_of_week                   = :monday
+        @log_level                           = :debug
+        @generators                          = app_generators
+        @cache_store                         = [ :file_store, "#{root}/tmp/cache/" ]
+        @railties_order                      = [:all]
+        @relative_url_root                   = ENV["RAILS_RELATIVE_URL_ROOT"]
+        @reload_classes_only_on_change       = true
+        @file_watcher                        = ActiveSupport::FileUpdateChecker
+        @exceptions_app                      = nil
+        @autoflush_log                       = true
+        @log_formatter                       = ActiveSupport::Logger::SimpleFormatter.new
+        @eager_load                          = nil
+        @secret_token                        = nil
+        @secret_key_base                     = nil
+        @api_only                            = false
+        @debug_exception_response_format     = nil
+        @x                                   = Custom.new
+        @enable_dependency_loading           = false
+        @read_encrypted_secrets              = false
+        @content_security_policy             = nil
+        @content_security_policy_report_only = false
       end
 
       def load_defaults(target_version)
@@ -71,7 +73,6 @@ module Rails
           end
 
           self.ssl_options = { hsts: { subdomains: true } }
-
         when "5.1"
           load_defaults "5.0"
 
@@ -82,7 +83,6 @@ module Rails
           if respond_to?(:action_view)
             action_view.form_with_generates_remote_forms = true
           end
-
         when "5.2"
           load_defaults "5.1"
 
@@ -106,6 +106,9 @@ module Rails
             action_controller.default_protect_from_forgery = true
           end
 
+          if respond_to?(:action_view)
+            action_view.form_with_generates_ids = true
+          end
         else
           raise "Unknown version #{target_version.to_s.inspect}"
         end
@@ -228,6 +231,10 @@ module Rails
         SourceAnnotationExtractor::Annotation
       end
 
+      def content_security_policy(&block)
+        @content_security_policy ||= ActionDispatch::ContentSecurityPolicy.new(&block)
+      end
+
       class Custom #:nodoc:
         def initialize
           @configurations = Hash.new
diff --git a/railties/lib/rails/application/default_middleware_stack.rb b/railties/lib/rails/application/default_middleware_stack.rb
index ea2273c1f2..0e79ba7da0 100644
--- a/railties/lib/rails/application/default_middleware_stack.rb
+++ b/railties/lib/rails/application/default_middleware_stack.rb
@@ -63,6 +63,10 @@ module Rails
             middleware.use ::ActionDispatch::Flash
           end
 
+          unless config.api_only
+            middleware.use ::ActionDispatch::ContentSecurityPolicy::Middleware
+          end
+
           middleware.use ::Rack::Head
           middleware.use ::Rack::ConditionalGet
           middleware.use ::Rack::ETag, "no-cache"
diff --git a/railties/lib/rails/cli.rb b/railties/lib/rails/cli.rb
index 50a2ed30cf..e56e604fdc 100644
--- a/railties/lib/rails/cli.rb
+++ b/railties/lib/rails/cli.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "app_loader"
+require "rails/app_loader"
 
 # If we are inside a Rails application this method performs an exec and thus
 # the rest of this script is not run.
 Rails::AppLoader.exec_app
 
-require_relative "ruby_version_check"
+require "rails/ruby_version_check"
 Signal.trap("INT") { puts; exit(1) }
 
-require_relative "command"
+require "rails/command"
 
 if ARGV.first == "plugin"
   ARGV.shift
diff --git a/railties/lib/rails/code_statistics.rb b/railties/lib/rails/code_statistics.rb
index 7ceb86198f..9c447c366f 100644
--- a/railties/lib/rails/code_statistics.rb
+++ b/railties/lib/rails/code_statistics.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "code_statistics_calculator"
+require "rails/code_statistics_calculator"
 require "active_support/core_ext/enumerable"
 
 class CodeStatistics #:nodoc:
diff --git a/railties/lib/rails/command/base.rb b/railties/lib/rails/command/base.rb
index 8df4f98d3e..fa462ef7e9 100644
--- a/railties/lib/rails/command/base.rb
+++ b/railties/lib/rails/command/base.rb
@@ -6,7 +6,7 @@ require "erb"
 require "active_support/core_ext/string/filters"
 require "active_support/core_ext/string/inflections"
 
-require_relative "actions"
+require "rails/command/actions"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/command/helpers/editor.rb b/railties/lib/rails/command/helpers/editor.rb
new file mode 100644
index 0000000000..6191d97672
--- /dev/null
+++ b/railties/lib/rails/command/helpers/editor.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require "active_support/encrypted_file"
+
+module Rails
+  module Command
+    module Helpers
+      module Editor
+        private
+          def ensure_editor_available(command:)
+            if ENV["EDITOR"].to_s.empty?
+              say "No $EDITOR to open file in. Assign one like this:"
+              say ""
+              say %(EDITOR="mate --wait" #{command})
+              say ""
+              say "For editors that fork and exit immediately, it's important to pass a wait flag,"
+              say "otherwise the credentials will be saved immediately with no chance to edit."
+
+              false
+            else
+              true
+            end
+          end
+
+          def catch_editing_exceptions
+            yield
+          rescue Interrupt
+            say "Aborted changing file: nothing saved."
+          rescue ActiveSupport::EncryptedFile::MissingKeyError => error
+            say error.message
+          end
+      end
+    end
+  end
+end
diff --git a/railties/lib/rails/commands.rb b/railties/lib/rails/commands.rb
index 1aea1e1a96..77961a0292 100644
--- a/railties/lib/rails/commands.rb
+++ b/railties/lib/rails/commands.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "command"
+require "rails/command"
 
 aliases = {
   "g"  => "generate",
diff --git a/railties/lib/rails/commands/application/application_command.rb b/railties/lib/rails/commands/application/application_command.rb
index 13d47a63bc..f77553b830 100644
--- a/railties/lib/rails/commands/application/application_command.rb
+++ b/railties/lib/rails/commands/application/application_command.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../generators"
-require_relative "../../generators/rails/app/app_generator"
+require "rails/generators"
+require "rails/generators/rails/app/app_generator"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/commands/console/console_command.rb b/railties/lib/rails/commands/console/console_command.rb
index 5dc695c240..e35faa5b01 100644
--- a/railties/lib/rails/commands/console/console_command.rb
+++ b/railties/lib/rails/commands/console/console_command.rb
@@ -3,7 +3,7 @@
 require "irb"
 require "irb/completion"
 
-require_relative "../../command/environment_argument"
+require "rails/command/environment_argument"
 
 module Rails
   class Console
diff --git a/railties/lib/rails/commands/credentials/credentials_command.rb b/railties/lib/rails/commands/credentials/credentials_command.rb
index 88fb032d84..8085f07c2b 100644
--- a/railties/lib/rails/commands/credentials/credentials_command.rb
+++ b/railties/lib/rails/commands/credentials/credentials_command.rb
@@ -1,10 +1,13 @@
 # frozen_string_literal: true
 
 require "active_support"
+require "rails/command/helpers/editor"
 
 module Rails
   module Command
     class CredentialsCommand < Rails::Command::Base # :nodoc:
+      include Helpers::Editor
+
       no_commands do
         def help
           say "Usage:\n  #{self.class.banner}"
@@ -16,43 +19,28 @@ module Rails
       def edit
         require_application_and_environment!
 
-        ensure_editor_available || (return)
+        ensure_editor_available(command: "bin/rails credentials:edit") || (return)
         ensure_master_key_has_been_added
         ensure_credentials_have_been_added
 
-        change_credentials_in_system_editor
+        catch_editing_exceptions do
+          change_credentials_in_system_editor
+        end
 
         say "New credentials encrypted and saved."
-      rescue Interrupt
-        say "Aborted changing credentials: nothing saved."
-      rescue ActiveSupport::EncryptedFile::MissingKeyError => error
-        say error.message
       end
 
       def show
         require_application_and_environment!
+
         say Rails.application.credentials.read.presence ||
           "No credentials have been added yet. Use bin/rails credentials:edit to change that."
       end
 
       private
-        def ensure_editor_available
-          if ENV["EDITOR"].to_s.empty?
-            say "No $EDITOR to open credentials in. Assign one like this:"
-            say ""
-            say %(EDITOR="mate --wait" bin/rails credentials:edit)
-            say ""
-            say "For editors that fork and exit immediately, it's important to pass a wait flag,"
-            say "otherwise the credentials will be saved immediately with no chance to edit."
-
-            false
-          else
-            true
-          end
-        end
-
         def ensure_master_key_has_been_added
           master_key_generator.add_master_key_file
+          master_key_generator.ignore_master_key_file
         end
 
         def ensure_credentials_have_been_added
@@ -67,15 +55,15 @@ module Rails
 
 
         def master_key_generator
-          require_relative "../../generators"
-          require_relative "../../generators/rails/master_key/master_key_generator"
+          require "rails/generators"
+          require "rails/generators/rails/master_key/master_key_generator"
 
           Rails::Generators::MasterKeyGenerator.new
         end
 
         def credentials_generator
-          require_relative "../../generators"
-          require_relative "../../generators/rails/credentials/credentials_generator"
+          require "rails/generators"
+          require "rails/generators/rails/credentials/credentials_generator"
 
           Rails::Generators::CredentialsGenerator.new
         end
diff --git a/railties/lib/rails/commands/dbconsole/dbconsole_command.rb b/railties/lib/rails/commands/dbconsole/dbconsole_command.rb
index 5234969743..8df548b5de 100644
--- a/railties/lib/rails/commands/dbconsole/dbconsole_command.rb
+++ b/railties/lib/rails/commands/dbconsole/dbconsole_command.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../command/environment_argument"
+require "rails/command/environment_argument"
 
 module Rails
   class DBConsole
diff --git a/railties/lib/rails/commands/destroy/destroy_command.rb b/railties/lib/rails/commands/destroy/destroy_command.rb
index 686193ddb9..dd432d28fd 100644
--- a/railties/lib/rails/commands/destroy/destroy_command.rb
+++ b/railties/lib/rails/commands/destroy/destroy_command.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../generators"
+require "rails/generators"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/commands/encrypted/encrypted_command.rb b/railties/lib/rails/commands/encrypted/encrypted_command.rb
new file mode 100644
index 0000000000..898094f1a4
--- /dev/null
+++ b/railties/lib/rails/commands/encrypted/encrypted_command.rb
@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+require "pathname"
+require "active_support"
+require "rails/command/helpers/editor"
+
+module Rails
+  module Command
+    class EncryptedCommand < Rails::Command::Base # :nodoc:
+      include Helpers::Editor
+
+      class_option :key, aliases: "-k", type: :string,
+        default: "config/master.key", desc: "The Rails.root relative path to the encryption key"
+
+      no_commands do
+        def help
+          say "Usage:\n  #{self.class.banner}"
+          say ""
+        end
+      end
+
+      def edit(file_path)
+        require_application_and_environment!
+
+        ensure_editor_available(command: "bin/rails encrypted:edit") || (return)
+        ensure_encryption_key_has_been_added(options[:key])
+        ensure_encrypted_file_has_been_added(file_path, options[:key])
+
+        catch_editing_exceptions do
+          change_encrypted_file_in_system_editor(file_path, options[:key])
+        end
+
+        say "File encrypted and saved."
+      rescue ActiveSupport::MessageEncryptor::InvalidMessage
+        say "Couldn't decrypt #{file_path}. Perhaps you passed the wrong key?"
+      end
+
+      def show(file_path)
+        require_application_and_environment!
+
+        say Rails.application.encrypted(file_path, key_path: options[:key]).read.presence ||
+          "File '#{file_path}' does not exist. Use bin/rails encrypted:edit #{file_path} to change that."
+      end
+
+      private
+        def ensure_encryption_key_has_been_added(key_path)
+          encryption_key_file_generator.add_key_file(key_path)
+          encryption_key_file_generator.ignore_key_file(key_path)
+        end
+
+        def ensure_encrypted_file_has_been_added(file_path, key_path)
+          encrypted_file_generator.add_encrypted_file_silently(file_path, key_path)
+        end
+
+        def change_encrypted_file_in_system_editor(file_path, key_path)
+          Rails.application.encrypted(file_path, key_path: key_path).change do |tmp_path|
+            system("#{ENV["EDITOR"]} #{tmp_path}")
+          end
+        end
+
+
+        def encryption_key_file_generator
+          require "rails/generators"
+          require "rails/generators/rails/encryption_key_file/encryption_key_file_generator"
+
+          Rails::Generators::EncryptionKeyFileGenerator.new
+        end
+
+        def encrypted_file_generator
+          require "rails/generators"
+          require "rails/generators/rails/encrypted_file/encrypted_file_generator"
+
+          Rails::Generators::EncryptedFileGenerator.new
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/commands/generate/generate_command.rb b/railties/lib/rails/commands/generate/generate_command.rb
index 73f627637d..93d7a0ce3a 100644
--- a/railties/lib/rails/commands/generate/generate_command.rb
+++ b/railties/lib/rails/commands/generate/generate_command.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../generators"
+require "rails/generators"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/commands/plugin/plugin_command.rb b/railties/lib/rails/commands/plugin/plugin_command.rb
index 5d3dfadf84..2b192abf9b 100644
--- a/railties/lib/rails/commands/plugin/plugin_command.rb
+++ b/railties/lib/rails/commands/plugin/plugin_command.rb
@@ -36,8 +36,8 @@ module Rails
 
       private
         def run_plugin_generator(plugin_args)
-          require_relative "../../generators"
-          require_relative "../../generators/rails/plugin/plugin_generator"
+          require "rails/generators"
+          require "rails/generators/rails/plugin/plugin_generator"
           Rails::Generators::PluginGenerator.start plugin_args
         end
     end
diff --git a/railties/lib/rails/commands/runner/runner_command.rb b/railties/lib/rails/commands/runner/runner_command.rb
index cd9462e08f..30fbf04982 100644
--- a/railties/lib/rails/commands/runner/runner_command.rb
+++ b/railties/lib/rails/commands/runner/runner_command.rb
@@ -32,13 +32,13 @@ module Rails
         ARGV.replace(command_argv)
 
         if code_or_file == "-"
-          eval($stdin.read, binding, "stdin")
+          eval($stdin.read, TOPLEVEL_BINDING, "stdin")
         elsif File.exist?(code_or_file)
           $0 = code_or_file
           Kernel.load code_or_file
         else
           begin
-            eval(code_or_file, binding, __FILE__, __LINE__)
+            eval(code_or_file, TOPLEVEL_BINDING, __FILE__, __LINE__)
           rescue SyntaxError, NameError => error
             $stderr.puts "Please specify a valid ruby command or the path of a script to run."
             $stderr.puts "Run '#{self.class.executable} -h' for help."
diff --git a/railties/lib/rails/commands/secrets/secrets_command.rb b/railties/lib/rails/commands/secrets/secrets_command.rb
index d93c4de74e..73a88767e2 100644
--- a/railties/lib/rails/commands/secrets/secrets_command.rb
+++ b/railties/lib/rails/commands/secrets/secrets_command.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "../../secrets"
+require "rails/secrets"
 
 module Rails
   module Command
@@ -15,7 +15,7 @@ module Rails
       end
 
       def setup
-        generator.start
+        deprecate_in_favor_of_credentials_and_exit
       end
 
       def edit
@@ -42,11 +42,10 @@ module Rails
       rescue Rails::Secrets::MissingKeyError => error
         say error.message
       rescue Errno::ENOENT => error
-        raise unless error.message =~ /secrets\.yml\.enc/
-
-        Rails::Secrets.read_template_for_editing do |tmp_path|
-          system("#{ENV["EDITOR"]} #{tmp_path}")
-          generator.skip_secrets_file { setup }
+        if error.message =~ /secrets\.yml\.enc/
+          deprecate_in_favor_of_credentials_and_exit
+        else
+          raise
         end
       end
 
@@ -55,11 +54,11 @@ module Rails
       end
 
       private
-        def generator
-          require_relative "../../generators"
-          require_relative "../../generators/rails/encrypted_secrets/encrypted_secrets_generator"
+        def deprecate_in_favor_of_credentials_and_exit
+          say "Encrypted secrets is deprecated in favor of credentials. Run:"
+          say "bin/rails credentials --help"
 
-          Rails::Generators::EncryptedSecretsGenerator
+          exit 1
         end
     end
   end
diff --git a/railties/lib/rails/commands/server/server_command.rb b/railties/lib/rails/commands/server/server_command.rb
index 785265d766..703ec59087 100644
--- a/railties/lib/rails/commands/server/server_command.rb
+++ b/railties/lib/rails/commands/server/server_command.rb
@@ -6,7 +6,7 @@ require "action_dispatch"
 require "rails"
 require "active_support/deprecation"
 require "active_support/core_ext/string/filters"
-require_relative "../../dev_caching"
+require "rails/dev_caching"
 
 module Rails
   class Server < ::Rack::Server
@@ -127,6 +127,7 @@ module Rails
       class_option "dev-caching", aliases: "-C", type: :boolean, default: nil,
         desc: "Specifies whether to perform caching in development."
       class_option "restart", type: :boolean, default: nil, hide: true
+      class_option "early_hints", type: :boolean, default: nil, desc: "Enables HTTP/2 early hints."
 
       def initialize(args = [], local_options = {}, config = {})
         @original_options = local_options
@@ -161,7 +162,8 @@ module Rails
             daemonize:             options[:daemon],
             pid:                   pid,
             caching:               options["dev-caching"],
-            restart_cmd:           restart_command
+            restart_cmd:           restart_command,
+            early_hints:           early_hints
           }
         end
       end
@@ -227,6 +229,10 @@ module Rails
           "bin/rails server #{@server} #{@original_options.join(" ")} --restart"
         end
 
+        def early_hints
+          options[:early_hints]
+        end
+
         def pid
           File.expand_path(options[:pid])
         end
diff --git a/railties/lib/rails/commands/test/test_command.rb b/railties/lib/rails/commands/test/test_command.rb
index a2216553ca..00ea9ac4a6 100644
--- a/railties/lib/rails/commands/test/test_command.rb
+++ b/railties/lib/rails/commands/test/test_command.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../command"
-require_relative "../../test_unit/runner"
-require_relative "../../test_unit/reporter"
+require "rails/command"
+require "rails/test_unit/runner"
+require "rails/test_unit/reporter"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/configuration.rb b/railties/lib/rails/configuration.rb
index 70815d114d..d3a54d9364 100644
--- a/railties/lib/rails/configuration.rb
+++ b/railties/lib/rails/configuration.rb
@@ -2,8 +2,8 @@
 
 require "active_support/ordered_options"
 require "active_support/core_ext/object"
-require_relative "paths"
-require_relative "rack"
+require "rails/paths"
+require "rails/rack"
 
 module Rails
   module Configuration
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index cc2030d37d..6a13a84108 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "railtie"
-require_relative "engine/railties"
+require "rails/railtie"
+require "rails/engine/railties"
 require "active_support/core_ext/module/delegation"
 require "pathname"
 require "thread"
@@ -439,8 +439,8 @@ module Rails
     # Load console and invoke the registered hooks.
     # Check <tt>Rails::Railtie.console</tt> for more info.
     def load_console(app = self)
-      require_relative "console/app"
-      require_relative "console/helpers"
+      require "rails/console/app"
+      require "rails/console/helpers"
       run_console_blocks(app)
       self
     end
@@ -463,7 +463,7 @@ module Rails
     # Load Rails generators and invoke the registered hooks.
     # Check <tt>Rails::Railtie.generators</tt> for more info.
     def load_generators(app = self)
-      require_relative "generators"
+      require "rails/generators"
       run_generators_blocks(app)
       Rails::Generators.configure!(app.config.generators)
       self
diff --git a/railties/lib/rails/engine/commands.rb b/railties/lib/rails/engine/commands.rb
index 3854907507..05218640c6 100644
--- a/railties/lib/rails/engine/commands.rb
+++ b/railties/lib/rails/engine/commands.rb
@@ -6,4 +6,4 @@ unless defined?(APP_PATH)
   end
 end
 
-require_relative "../commands"
+require "rails/commands"
diff --git a/railties/lib/rails/engine/configuration.rb b/railties/lib/rails/engine/configuration.rb
index 16ba7f9eb8..6bf0406b21 100644
--- a/railties/lib/rails/engine/configuration.rb
+++ b/railties/lib/rails/engine/configuration.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../railtie/configuration"
+require "rails/railtie/configuration"
 
 module Rails
   class Engine
diff --git a/railties/lib/rails/engine/updater.rb b/railties/lib/rails/engine/updater.rb
index 21a0fc5562..be7a47124a 100644
--- a/railties/lib/rails/engine/updater.rb
+++ b/railties/lib/rails/engine/updater.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../generators"
-require_relative "../generators/rails/plugin/plugin_generator"
+require "rails/generators"
+require "rails/generators/rails/plugin/plugin_generator"
 
 module Rails
   class Engine
diff --git a/railties/lib/rails/gem_version.rb b/railties/lib/rails/gem_version.rb
index 92b5e0392a..2cc861a1bd 100644
--- a/railties/lib/rails/gem_version.rb
+++ b/railties/lib/rails/gem_version.rb
@@ -10,7 +10,7 @@ module Rails
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index a630d55e59..6c9c109f17 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -4,7 +4,7 @@ activesupport_path = File.expand_path("../../../activesupport/lib", __dir__)
 $:.unshift(activesupport_path) if File.directory?(activesupport_path) && !$:.include?(activesupport_path)
 
 require "thor/group"
-require_relative "command"
+require "rails/command"
 
 require "active_support"
 require "active_support/core_ext/object/blank"
@@ -218,6 +218,7 @@ module Rails
         rails.delete("app")
         rails.delete("plugin")
         rails.delete("encrypted_secrets")
+        rails.delete("credentials")
 
         hidden_namespaces.each { |n| groups.delete(n.to_s) }
 
@@ -273,8 +274,9 @@ module Rails
         else
           options     = sorted_groups.flat_map(&:last)
           suggestions = options.sort_by { |suggested| levenshtein_distance(namespace.to_s, suggested) }.first(3)
+          suggestions.map! { |s| "'#{s}'" }
           msg =  "Could not find generator '#{namespace}'. ".dup
-          msg << "Maybe you meant #{ suggestions.map { |s| "'#{s}'" }.to_sentence(last_word_connector: " or ", locale: :en) }\n"
+          msg << "Maybe you meant #{ suggestions[0...-1].join(', ')} or #{suggestions[-1]}\n"
           msg << "Run `rails generate --help` for more options."
           puts msg
         end
diff --git a/railties/lib/rails/generators/actions.rb b/railties/lib/rails/generators/actions.rb
index 9800e5750a..3362bf629a 100644
--- a/railties/lib/rails/generators/actions.rb
+++ b/railties/lib/rails/generators/actions.rb
@@ -221,6 +221,7 @@ module Rails
       #   rake("db:migrate")
       #   rake("db:migrate", env: "production")
       #   rake("gems:install", sudo: true)
+      #   rake("gems:install", capture: true)
       def rake(command, options = {})
         execute_command :rake, command, options
       end
@@ -230,6 +231,7 @@ module Rails
       #   rails_command("db:migrate")
       #   rails_command("db:migrate", env: "production")
       #   rails_command("gems:install", sudo: true)
+      #   rails_command("gems:install", capture: true)
       def rails_command(command, options = {})
         execute_command :rails, command, options
       end
@@ -292,7 +294,11 @@ module Rails
           log executor, command
           env  = options[:env] || ENV["RAILS_ENV"] || "development"
           sudo = options[:sudo] && !Gem.win_platform? ? "sudo " : ""
-          in_root { run("#{sudo}#{extify(executor)} #{command} RAILS_ENV=#{env}", verbose: false) }
+          config = { verbose: false }
+
+          config.merge!(capture: options[:capture]) if options[:capture]
+
+          in_root { run("#{sudo}#{extify(executor)} #{command} RAILS_ENV=#{env}", config) }
         end
 
         # Add an extension to the given name based on the platform.
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index c8688fb7f3..b9ae24de59 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -3,10 +3,10 @@
 require "fileutils"
 require "digest/md5"
 require "active_support/core_ext/string/strip"
-require_relative "../version" unless defined?(Rails::VERSION)
+require "rails/version" unless defined?(Rails::VERSION)
 require "open-uri"
 require "uri"
-require_relative "../generators"
+require "rails/generators"
 require "active_support/core_ext/array/extract_options"
 
 module Rails
@@ -26,75 +26,78 @@ module Rails
       end
 
       def self.add_shared_options_for(name)
-        class_option :template,           type: :string, aliases: "-m",
-                                          desc: "Path to some #{name} template (can be a filesystem path or URL)"
+        class_option :template,            type: :string, aliases: "-m",
+                                           desc: "Path to some #{name} template (can be a filesystem path or URL)"
 
-        class_option :database,           type: :string, aliases: "-d", default: "sqlite3",
-                                          desc: "Preconfigure for selected database (options: #{DATABASES.join('/')})"
+        class_option :database,            type: :string, aliases: "-d", default: "sqlite3",
+                                           desc: "Preconfigure for selected database (options: #{DATABASES.join('/')})"
 
-        class_option :skip_yarn,          type: :boolean, default: false,
-                                          desc: "Don't use Yarn for managing JavaScript dependencies"
+        class_option :skip_yarn,           type: :boolean, default: false,
+                                           desc: "Don't use Yarn for managing JavaScript dependencies"
 
-        class_option :skip_gemfile,       type: :boolean, default: false,
-                                          desc: "Don't create a Gemfile"
+        class_option :skip_gemfile,        type: :boolean, default: false,
+                                           desc: "Don't create a Gemfile"
 
-        class_option :skip_git,           type: :boolean, aliases: "-G", default: false,
-                                          desc: "Skip .gitignore file"
+        class_option :skip_git,            type: :boolean, aliases: "-G", default: false,
+                                           desc: "Skip .gitignore file"
 
-        class_option :skip_keeps,         type: :boolean, default: false,
-                                          desc: "Skip source control .keep files"
+        class_option :skip_keeps,          type: :boolean, default: false,
+                                           desc: "Skip source control .keep files"
 
-        class_option :skip_action_mailer, type: :boolean, aliases: "-M",
-                                          default: false,
-                                          desc: "Skip Action Mailer files"
+        class_option :skip_action_mailer,  type: :boolean, aliases: "-M",
+                                           default: false,
+                                           desc: "Skip Action Mailer files"
 
-        class_option :skip_active_record, type: :boolean, aliases: "-O", default: false,
-                                          desc: "Skip Active Record files"
+        class_option :skip_active_record,  type: :boolean, aliases: "-O", default: false,
+                                           desc: "Skip Active Record files"
 
-        class_option :skip_puma,          type: :boolean, aliases: "-P", default: false,
-                                          desc: "Skip Puma related files"
+        class_option :skip_active_storage, type: :boolean, default: false,
+                                           desc: "Skip Active Storage files"
 
-        class_option :skip_action_cable,  type: :boolean, aliases: "-C", default: false,
-                                          desc: "Skip Action Cable files"
+        class_option :skip_puma,           type: :boolean, aliases: "-P", default: false,
+                                           desc: "Skip Puma related files"
 
-        class_option :skip_sprockets,     type: :boolean, aliases: "-S", default: false,
-                                          desc: "Skip Sprockets files"
+        class_option :skip_action_cable,   type: :boolean, aliases: "-C", default: false,
+                                           desc: "Skip Action Cable files"
 
-        class_option :skip_spring,        type: :boolean, default: false,
-                                          desc: "Don't install Spring application preloader"
+        class_option :skip_sprockets,      type: :boolean, aliases: "-S", default: false,
+                                           desc: "Skip Sprockets files"
 
-        class_option :skip_listen,        type: :boolean, default: false,
-                                          desc: "Don't generate configuration that depends on the listen gem"
+        class_option :skip_spring,         type: :boolean, default: false,
+                                           desc: "Don't install Spring application preloader"
 
-        class_option :skip_coffee,        type: :boolean, default: false,
-                                          desc: "Don't use CoffeeScript"
+        class_option :skip_listen,         type: :boolean, default: false,
+                                           desc: "Don't generate configuration that depends on the listen gem"
 
-        class_option :skip_javascript,    type: :boolean, aliases: "-J", default: false,
-                                          desc: "Skip JavaScript files"
+        class_option :skip_coffee,         type: :boolean, default: false,
+                                           desc: "Don't use CoffeeScript"
 
-        class_option :skip_turbolinks,    type: :boolean, default: false,
-                                          desc: "Skip turbolinks gem"
+        class_option :skip_javascript,     type: :boolean, aliases: "-J", default: false,
+                                           desc: "Skip JavaScript files"
 
-        class_option :skip_test,          type: :boolean, aliases: "-T", default: false,
-                                          desc: "Skip test files"
+        class_option :skip_turbolinks,     type: :boolean, default: false,
+                                           desc: "Skip turbolinks gem"
 
-        class_option :skip_system_test,   type: :boolean, default: false,
-                                          desc: "Skip system test files"
+        class_option :skip_test,           type: :boolean, aliases: "-T", default: false,
+                                           desc: "Skip test files"
 
-        class_option :dev,                type: :boolean, default: false,
-                                          desc: "Setup the #{name} with Gemfile pointing to your Rails checkout"
+        class_option :skip_system_test,    type: :boolean, default: false,
+                                           desc: "Skip system test files"
 
-        class_option :edge,               type: :boolean, default: false,
-                                          desc: "Setup the #{name} with Gemfile pointing to Rails repository"
+        class_option :dev,                 type: :boolean, default: false,
+                                           desc: "Setup the #{name} with Gemfile pointing to your Rails checkout"
 
-        class_option :rc,                 type: :string, default: nil,
-                                          desc: "Path to file containing extra configuration options for rails command"
+        class_option :edge,                type: :boolean, default: false,
+                                           desc: "Setup the #{name} with Gemfile pointing to Rails repository"
 
-        class_option :no_rc,              type: :boolean, default: false,
-                                          desc: "Skip loading of extra configuration options from .railsrc file"
+        class_option :rc,                  type: :string, default: nil,
+                                           desc: "Path to file containing extra configuration options for rails command"
 
-        class_option :help,               type: :boolean, aliases: "-h", group: :rails,
-                                          desc: "Show this help message and quit"
+        class_option :no_rc,               type: :boolean, default: false,
+                                           desc: "Skip loading of extra configuration options from .railsrc file"
+
+        class_option :help,                type: :boolean, aliases: "-h", group: :rails,
+                                           desc: "Show this help message and quit"
       end
 
       def initialize(*args)
@@ -189,15 +192,33 @@ module Rails
       def webserver_gemfile_entry # :doc:
         return [] if options[:skip_puma]
         comment = "Use Puma as the app server"
-        GemfileEntry.new("puma", "~> 3.7", comment)
+        GemfileEntry.new("puma", "~> 3.11", comment)
       end
 
       def include_all_railties? # :doc:
-        options.values_at(:skip_active_record, :skip_action_mailer, :skip_test, :skip_sprockets, :skip_action_cable).none?
+        [
+          options.values_at(
+            :skip_active_record,
+            :skip_action_mailer,
+            :skip_test,
+            :skip_sprockets,
+            :skip_action_cable
+          ),
+          skip_active_storage?
+        ].flatten.none?
       end
 
       def comment_if(value) # :doc:
-        options[value] ? "# " : ""
+        question = "#{value}?"
+
+        comment =
+          if respond_to?(question, true)
+            send(question)
+          else
+            options[value]
+          end
+
+        comment ? "# " : ""
       end
 
       def keeps? # :doc:
@@ -208,6 +229,10 @@ module Rails
         !options[:skip_active_record] && options[:database] == "sqlite3"
       end
 
+      def skip_active_storage? # :doc:
+        options[:skip_active_storage] || options[:skip_active_record]
+      end
+
       class GemfileEntry < Struct.new(:name, :version, :comment, :options, :commented_out)
         def initialize(name, version, comment, options = {}, commented_out = false)
           super
@@ -241,17 +266,14 @@ module Rails
       end
 
       def rails_gemfile_entry
-        dev_edge_common = [
-          GemfileEntry.github("arel", "rails/arel"),
-        ]
         if options.dev?
           [
             GemfileEntry.path("rails", Rails::Generators::RAILS_DEV_PATH)
-          ] + dev_edge_common
+          ]
         elsif options.edge?
           [
             GemfileEntry.github("rails", "rails/rails")
-          ] + dev_edge_common
+          ]
         else
           [GemfileEntry.version("rails",
                             rails_version_specifier,
@@ -275,7 +297,7 @@ module Rails
       def gem_for_database
         # %w( mysql postgresql sqlite3 oracle frontbase ibm_db sqlserver jdbcmysql jdbcsqlite3 jdbcpostgresql )
         case options[:database]
-        when "mysql"          then ["mysql2", [">= 0.3.18", "< 0.5"]]
+        when "mysql"          then ["mysql2", ["~> 0.4.4"]]
         when "postgresql"     then ["pg", ["~> 0.18"]]
         when "oracle"         then ["activerecord-oracle_enhanced-adapter", nil]
         when "frontbase"      then ["ruby-frontbase", nil]
@@ -369,7 +391,7 @@ module Rails
         return [] if options[:skip_action_cable]
         comment = "Use Redis adapter to run Action Cable in production"
         gems = []
-        gems << GemfileEntry.new("redis", "~> 3.0", comment, {}, true)
+        gems << GemfileEntry.new("redis", "~> 4.0", comment, {}, true)
         gems
       end
 
@@ -434,6 +456,16 @@ module Rails
         end
       end
 
+      def run_active_storage
+        unless skip_active_storage?
+          if bundle_install?
+            rails_command "active_storage:install", capture: options[:quiet]
+          else
+            log("Active Storage installation was skipped. Please run `bin/rails active_storage:install` to install Active Storage files.")
+          end
+        end
+      end
+
       def empty_directory_with_keep_file(destination, config = {})
         empty_directory(destination, config)
         keep_file(destination)
diff --git a/railties/lib/rails/generators/css/assets/assets_generator.rb b/railties/lib/rails/generators/css/assets/assets_generator.rb
index 5f7be769b2..f657d1e50f 100644
--- a/railties/lib/rails/generators/css/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/css/assets/assets_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../named_base"
+require "rails/generators/named_base"
 
 module Css # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb
index 5996cb1483..89c560f382 100644
--- a/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb
@@ -1,17 +1,17 @@
 # frozen_string_literal: true
 
-require_relative "../../named_base"
+require "rails/generators/named_base"
 
 module Css # :nodoc:
   module Generators # :nodoc:
     class ScaffoldGenerator < Rails::Generators::NamedBase # :nodoc:
+      source_root Rails::Generators::ScaffoldGenerator.source_root
+
       # In order to allow the Sass generators to pick up the default Rails CSS and
       # transform it, we leave it in a standard location for the CSS stylesheet
       # generators to handle. For the simple, default case, just copy it over.
       def copy_stylesheet
-        dir = Rails::Generators::ScaffoldGenerator.source_root
-        file = File.join(dir, "scaffold.css")
-        create_file "app/assets/stylesheets/scaffold.css", File.read(file)
+        copy_file "scaffold.css", "app/assets/stylesheets/scaffold.css"
       end
     end
   end
diff --git a/railties/lib/rails/generators/erb.rb b/railties/lib/rails/generators/erb.rb
index 2c20834611..ba20bcd32a 100644
--- a/railties/lib/rails/generators/erb.rb
+++ b/railties/lib/rails/generators/erb.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "named_base"
+require "rails/generators/named_base"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/controller/controller_generator.rb b/railties/lib/rails/generators/erb/controller/controller_generator.rb
index 1a6c84288b..8e13744b2a 100644
--- a/railties/lib/rails/generators/erb/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/erb/controller/controller_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../erb"
+require "rails/generators/erb"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/controller/templates/view.html.erb b/railties/lib/rails/generators/erb/controller/templates/view.html.erb.tt
index cd54d13d83..cd54d13d83 100644
--- a/railties/lib/rails/generators/erb/controller/templates/view.html.erb
+++ b/railties/lib/rails/generators/erb/controller/templates/view.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/mailer/mailer_generator.rb b/railties/lib/rails/generators/erb/mailer/mailer_generator.rb
index 5774d86c8e..e2ea66415f 100644
--- a/railties/lib/rails/generators/erb/mailer/mailer_generator.rb
+++ b/railties/lib/rails/generators/erb/mailer/mailer_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../erb"
+require "rails/generators/erb"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/mailer/templates/view.html.erb b/railties/lib/rails/generators/erb/mailer/templates/view.html.erb.tt
index b5045671b3..b5045671b3 100644
--- a/railties/lib/rails/generators/erb/mailer/templates/view.html.erb
+++ b/railties/lib/rails/generators/erb/mailer/templates/view.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/mailer/templates/view.text.erb b/railties/lib/rails/generators/erb/mailer/templates/view.text.erb.tt
index 342285df19..342285df19 100644
--- a/railties/lib/rails/generators/erb/mailer/templates/view.text.erb
+++ b/railties/lib/rails/generators/erb/mailer/templates/view.text.erb.tt
diff --git a/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb
index e80c6d4b7d..2fc04e4094 100644
--- a/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../erb"
-require_relative "../../resource_helpers"
+require "rails/generators/erb"
+require "rails/generators/resource_helpers"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb.tt
index 4f2e84f924..518cb1121e 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb.tt
@@ -1,4 +1,4 @@
-<%%= form_with(model: <%= singular_table_name %>, local: true) do |form| %>
+<%%= form_with(model: <%= model_resource_name %>, local: true) do |form| %>
   <%% if <%= singular_table_name %>.errors.any? %>
     <div id="error_explanation">
       <h2><%%= pluralize(<%= singular_table_name %>.errors.count, "error") %> prohibited this <%= singular_table_name %> from being saved:</h2>
@@ -15,15 +15,15 @@
   <div class="field">
 <% if attribute.password_digest? -%>
     <%%= form.label :password %>
-    <%%= form.password_field :password, id: :<%= field_id(:password) %> %>
+    <%%= form.password_field :password %>
   </div>
 
   <div class="field">
     <%%= form.label :password_confirmation %>
-    <%%= form.password_field :password_confirmation, id: :<%= field_id(:password_confirmation) %> %>
+    <%%= form.password_field :password_confirmation %>
 <% else -%>
     <%%= form.label :<%= attribute.column_name %> %>
-    <%%= form.<%= attribute.field_type %> :<%= attribute.column_name %>, id: :<%= field_id(attribute.column_name) %> %>
+    <%%= form.<%= attribute.field_type %> :<%= attribute.column_name %> %>
 <% end -%>
   </div>
 
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb.tt
index 81329473d9..81329473d9 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb.tt
index 5f4904fee1..e1ede7c713 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb.tt
@@ -18,9 +18,9 @@
 <% attributes.reject(&:password_digest?).each do |attribute| -%>
         <td><%%= <%= singular_table_name %>.<%= attribute.name %> %></td>
 <% end -%>
-        <td><%%= link_to 'Show', <%= singular_table_name %> %></td>
-        <td><%%= link_to 'Edit', edit_<%= singular_table_name %>_path(<%= singular_table_name %>) %></td>
-        <td><%%= link_to 'Destroy', <%= singular_table_name %>, method: :delete, data: { confirm: 'Are you sure?' } %></td>
+        <td><%%= link_to 'Show', <%= model_resource_name %> %></td>
+        <td><%%= link_to 'Edit', edit_<%= singular_route_name %>_path(<%= singular_table_name %>) %></td>
+        <td><%%= link_to 'Destroy', <%= model_resource_name %>, method: :delete, data: { confirm: 'Are you sure?' } %></td>
       </tr>
     <%% end %>
   </tbody>
@@ -28,4 +28,4 @@
 
 <br>
 
-<%%= link_to 'New <%= singular_table_name.titleize %>', new_<%= singular_table_name %>_path %>
+<%%= link_to 'New <%= singular_table_name.titleize %>', new_<%= singular_route_name %>_path %>
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb.tt
index 9b2b2f4875..9b2b2f4875 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb.tt
index 5e634153be..5e634153be 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb.tt
diff --git a/railties/lib/rails/generators/js/assets/assets_generator.rb b/railties/lib/rails/generators/js/assets/assets_generator.rb
index ea151aa04e..9d32c666dc 100644
--- a/railties/lib/rails/generators/js/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/js/assets/assets_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../named_base"
+require "rails/generators/named_base"
 
 module Js # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/migration.rb b/railties/lib/rails/generators/migration.rb
index 7162b8c0b4..1cbccfe461 100644
--- a/railties/lib/rails/generators/migration.rb
+++ b/railties/lib/rails/generators/migration.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/concern"
-require_relative "actions/create_migration"
+require "rails/generators/actions/create_migration"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/model_helpers.rb b/railties/lib/rails/generators/model_helpers.rb
index aa3564476a..50078404b3 100644
--- a/railties/lib/rails/generators/model_helpers.rb
+++ b/railties/lib/rails/generators/model_helpers.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "active_model"
+require "rails/generators/active_model"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/named_base.rb b/railties/lib/rails/generators/named_base.rb
index fe8447be23..98fcc95964 100644
--- a/railties/lib/rails/generators/named_base.rb
+++ b/railties/lib/rails/generators/named_base.rb
@@ -1,8 +1,7 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/module/introspection"
-require_relative "base"
-require_relative "generated_attribute"
+require "rails/generators/base"
+require "rails/generators/generated_attribute"
 
 module Rails
   module Generators
@@ -100,11 +99,11 @@ module Rails
         end
 
         def index_helper # :doc:
-          uncountable? ? "#{plural_table_name}_index" : plural_table_name
+          uncountable? ? "#{plural_route_name}_index" : plural_route_name
         end
 
         def show_helper # :doc:
-          "#{singular_table_name}_url(@#{singular_table_name})"
+          "#{singular_route_name}_url(@#{singular_table_name})"
         end
 
         def edit_helper # :doc:
@@ -112,11 +111,7 @@ module Rails
         end
 
         def new_helper # :doc:
-          "new_#{singular_table_name}_url"
-        end
-
-        def field_id(attribute_name)
-          [singular_table_name, attribute_name].join("_")
+          "new_#{singular_route_name}_url"
         end
 
         def singular_table_name # :doc:
@@ -152,6 +147,35 @@ module Rails
           end
         end
 
+        def redirect_resource_name # :doc:
+          model_resource_name(prefix: "@")
+        end
+
+        def model_resource_name(prefix: "") # :doc:
+          resource_name = "#{prefix}#{singular_table_name}"
+          if options[:model_name]
+            "[#{controller_class_path.map { |name| ":" + name }.join(", ")}, #{resource_name}]"
+          else
+            resource_name
+          end
+        end
+
+        def singular_route_name # :doc:
+          if options[:model_name]
+            "#{controller_class_path.join('_')}_#{singular_table_name}"
+          else
+            singular_table_name
+          end
+        end
+
+        def plural_route_name # :doc:
+          if options[:model_name]
+            "#{controller_class_path.join('_')}_#{plural_table_name}"
+          else
+            plural_table_name
+          end
+        end
+
         def assign_names!(name)
           @class_path = name.include?("/") ? name.split("/") : name.split("::")
           @class_path.map!(&:underscore)
@@ -193,7 +217,7 @@ module Rails
         #
         def self.check_class_collision(options = {}) # :doc:
           define_method :check_class_collision do
-            name = if respond_to?(:controller_class_name) # for ScaffoldBase
+            name = if respond_to?(:controller_class_name) # for ResourceHelpers
               controller_class_name
             else
               class_name
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index ac82ff6633..bf4570db90 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../app_base"
+require "rails/generators/app_base"
 
 module Rails
   module ActionMethods # :nodoc:
@@ -69,7 +69,7 @@ module Rails
 
     def version_control
       if !options[:skip_git] && !options[:pretend]
-        run "git init"
+        run "git init", capture: options[:quiet]
       end
     end
 
@@ -114,7 +114,7 @@ module Rails
         template "cable.yml" unless options[:skip_action_cable]
         template "puma.rb"   unless options[:skip_puma]
         template "spring.rb" if spring_install?
-        template "storage.yml"
+        template "storage.yml" unless skip_active_storage?
 
         directory "environments"
         directory "initializers"
@@ -128,6 +128,7 @@ module Rails
       active_storage_config_exist    = File.exist?("config/storage.yml")
       rack_cors_config_exist         = File.exist?("config/initializers/cors.rb")
       assets_config_exist            = File.exist?("config/initializers/assets.rb")
+      csp_config_exist               = File.exist?("config/initializers/content_security_policy.rb")
 
       config
 
@@ -139,7 +140,7 @@ module Rails
         template "config/cable.yml"
       end
 
-      if !active_storage_config_exist
+      if !skip_active_storage? && !active_storage_config_exist
         template "config/storage.yml"
       end
 
@@ -155,27 +156,27 @@ module Rails
         unless assets_config_exist
           remove_file "config/initializers/assets.rb"
         end
+
+        unless csp_config_exist
+          remove_file "config/initializers/content_security_policy.rb"
+        end
       end
     end
 
     def master_key
-      return if options[:pretend]
-
-      require_relative "../master_key/master_key_generator"
+      return if options[:pretend] || options[:dummy_app]
 
-      after_bundle do
-        Rails::Generators::MasterKeyGenerator.new.add_master_key_file
-      end
+      require "rails/generators/rails/master_key/master_key_generator"
+      master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet])
+      master_key_generator.add_master_key_file_silently
+      master_key_generator.ignore_master_key_file_silently
     end
 
     def credentials
-      return if options[:pretend]
-
-      require_relative "../credentials/credentials_generator"
+      return if options[:pretend] || options[:dummy_app]
 
-      after_bundle do
-        Rails::Generators::CredentialsGenerator.new.add_credentials_file_silently
-      end
+      require "rails/generators/rails/credentials/credentials_generator"
+      Rails::Generators::CredentialsGenerator.new([], quiet: options[:quiet]).add_credentials_file_silently
     end
 
     def database_yml
@@ -347,6 +348,14 @@ module Rails
         build(:public_directory)
       end
 
+      def create_tmp_files
+        build(:tmp)
+      end
+
+      def create_vendor_files
+        build(:vendor)
+      end
+
       def create_test_files
         build(:test) unless options[:skip_test]
       end
@@ -355,12 +364,8 @@ module Rails
         build(:system_test) if depends_on_system_test?
       end
 
-      def create_tmp_files
-        build(:tmp)
-      end
-
-      def create_vendor_files
-        build(:vendor)
+      def create_storage_files
+        build(:storage) unless skip_active_storage?
       end
 
       def delete_app_assets_if_api_option
@@ -432,6 +437,7 @@ module Rails
       def delete_non_api_initializers_if_api_option
         if options[:api]
           remove_file "config/initializers/cookies_serializer.rb"
+          remove_file "config/initializers/content_security_policy.rb"
         end
       end
 
@@ -457,6 +463,7 @@ module Rails
 
       public_task :apply_rails_template, :run_bundle
       public_task :run_webpack, :generate_spring_binstubs
+      public_task :run_active_storage
 
       def run_after_bundle_callbacks
         @after_bundle_callbacks.each(&:call)
@@ -509,10 +516,6 @@ module Rails
         end
       end
 
-      def app_secret
-        SecureRandom.hex(64)
-      end
-
       def mysql_socket
         @mysql_socket ||= [
           "/tmp/mysql.sock",                        # default
@@ -559,7 +562,7 @@ module Rails
 
         def handle_version_request!(argument)
           if ["--version", "-v"].include?(argument)
-            require_relative "../../../version"
+            require "rails/version"
             puts "Rails #{Rails::VERSION::STRING}"
             exit(0)
           end
diff --git a/railties/lib/rails/generators/rails/app/templates/Gemfile b/railties/lib/rails/generators/rails/app/templates/Gemfile.tt
index 7b7bebc957..e3ed3e7c11 100644
--- a/railties/lib/rails/generators/rails/app/templates/Gemfile
+++ b/railties/lib/rails/generators/rails/app/templates/Gemfile.tt
@@ -20,6 +20,11 @@ ruby <%= "'#{RUBY_VERSION}'" -%>
 
 # Use ActiveModel has_secure_password
 # gem 'bcrypt', '~> 3.1.7'
+<% unless skip_active_storage? -%>
+
+# Use ActiveStorage variant
+# gem 'mini_magick', '~> 4.8'
+<% end -%>
 
 # Use Capistrano for deployment
 # gem 'capistrano-rails', group: :development
@@ -36,11 +41,6 @@ gem 'bootsnap', '>= 1.1.0', require: false
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
-  <%- if depends_on_system_test? -%>
-  # Adds support for Capybara system testing and selenium driver
-  gem 'capybara', '~> 2.13'
-  gem 'selenium-webdriver'
-  <%- end -%>
 end
 
 group :development do
@@ -63,6 +63,16 @@ group :development do
 <% end -%>
 <% end -%>
 end
+
+<%- if depends_on_system_test? -%>
+group :test do
+  # Adds support for Capybara system testing and selenium driver
+  gem 'capybara', '~> 2.15'
+  gem 'selenium-webdriver'
+  # Easy installation and use of chromedriver to run system tests with Chrome
+  gem 'chromedriver-helper'
+end
+<%- end -%>
 <% end -%>
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
diff --git a/railties/lib/rails/generators/rails/app/templates/README.md b/railties/lib/rails/generators/rails/app/templates/README.md.tt
index 7db80e4ca1..7db80e4ca1 100644
--- a/railties/lib/rails/generators/rails/app/templates/README.md
+++ b/railties/lib/rails/generators/rails/app/templates/README.md.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/Rakefile b/railties/lib/rails/generators/rails/app/templates/Rakefile.tt
index e85f913914..e85f913914 100644
--- a/railties/lib/rails/generators/rails/app/templates/Rakefile
+++ b/railties/lib/rails/generators/rails/app/templates/Rakefile.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
index 62fd04f113..5183bcd256 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
@@ -12,7 +12,9 @@
 //
 <% unless options[:skip_javascript] -%>
 //= require rails-ujs
+<% unless skip_active_storage? -%>
 //= require activestorage
+<% end -%>
 <% unless options[:skip_turbolinks] -%>
 //= require turbolinks
 <% end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js.tt
index 739aa5f022..739aa5f022 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css b/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css.tt
index d05ea0f511..d05ea0f511 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb.tt
index d672697283..d672697283 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb.tt
index 0ff5442f47..0ff5442f47 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb b/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb.tt
index de6be7945c..de6be7945c 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb b/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb.tt
index a009ace51c..a009ace51c 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb b/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb.tt
index 286b2239d1..286b2239d1 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb b/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb.tt
index 10a4cba84d..10a4cba84d 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/bundle b/railties/lib/rails/generators/rails/app/templates/bin/bundle.tt
index a84f0afe47..a84f0afe47 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/bundle
+++ b/railties/lib/rails/generators/rails/app/templates/bin/bundle.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/rails b/railties/lib/rails/generators/rails/app/templates/bin/rails.tt
index 513a2e0183..513a2e0183 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/rails
+++ b/railties/lib/rails/generators/rails/app/templates/bin/rails.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/rake b/railties/lib/rails/generators/rails/app/templates/bin/rake.tt
index d14fc8395b..d14fc8395b 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/rake
+++ b/railties/lib/rails/generators/rails/app/templates/bin/rake.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/update.tt b/railties/lib/rails/generators/rails/app/templates/bin/update.tt
index d744bec32f..70cc71d83b 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/update.tt
+++ b/railties/lib/rails/generators/rails/app/templates/bin/update.tt
@@ -15,6 +15,11 @@ chdir APP_ROOT do
   puts '== Installing dependencies =='
   system! 'gem install bundler --conservative'
   system('bundle check') || system!('bundle install')
+<% unless options.skip_yarn? -%>
+
+  # Install JavaScript dependencies if using Yarn
+  # system('bin/yarn')
+<% end -%>
 <% unless options.skip_active_record? -%>
 
   puts "\n== Updating database =="
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/yarn b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
index c2f9b6768a..b4e4d95286 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/yarn
+++ b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
@@ -1,5 +1,5 @@
-VENDOR_PATH = File.expand_path('..', __dir__)
-Dir.chdir(VENDOR_PATH) do
+APP_ROOT = File.expand_path('..', __dir__)
+Dir.chdir(APP_ROOT) do
   begin
     exec "yarnpkg #{ARGV.join(' ')}"
   rescue Errno::ENOENT
diff --git a/railties/lib/rails/generators/rails/app/templates/config.ru b/railties/lib/rails/generators/rails/app/templates/config.ru.tt
index f7ba0b527b..f7ba0b527b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config.ru
+++ b/railties/lib/rails/generators/rails/app/templates/config.ru.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/application.rb b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
index dde09edb94..9e03e86771 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/application.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
@@ -8,10 +8,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
diff --git a/railties/lib/rails/generators/rails/app/templates/config/boot.rb b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
index b9e460cef3..b9e460cef3 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/boot.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/cable.yml b/railties/lib/rails/generators/rails/app/templates/config/cable.yml.tt
index 8e53156c71..8e53156c71 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/cable.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/cable.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml.tt
index 917b52e535..917b52e535 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml.tt
index d40117a27f..d40117a27f 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml.tt
index 563be77710..563be77710 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml.tt
index 2a67bdca25..2a67bdca25 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml.tt
index 70df04079d..70df04079d 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml.tt
index 371415e6a8..371415e6a8 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml.tt
index 04afaa0596..04afaa0596 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml.tt
index 6da0601b24..6da0601b24 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml.tt
index 145cfb7f74..145cfb7f74 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml.tt
index 9510568124..9510568124 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml.tt
index 049de65f22..049de65f22 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environment.rb b/railties/lib/rails/generators/rails/app/templates/config/environment.rb.tt
index 426333bb46..426333bb46 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environment.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/environment.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
index 98689cc30d..b383228dc0 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
@@ -26,9 +26,11 @@ Rails.application.configure do
 
     config.cache_store = :null_store
   end
+  <%- unless skip_active_storage? -%>
 
   # Store uploaded files on the local file system (see config/storage.yml for options)
   config.active_storage.service = :local
+  <%- end -%>
   <%- unless options.skip_action_mailer? -%>
 
   # Don't care if the mailer can't send.
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
index 2e0b555f6f..4c0f36db98 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
@@ -44,9 +44,11 @@ Rails.application.configure do
   # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
   # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX
 
+  <%- unless skip_active_storage? -%>
   # Store uploaded files on the local file system (see config/storage.yml for options)
   config.active_storage.service = :local
 
+  <%- end -%>
   <%- unless options[:skip_action_cable] -%>
   # Mount Action Cable outside main process or domain
   # config.action_cable.mount_path = nil
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
index a53978bc6e..ff4c89219a 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
@@ -28,8 +28,11 @@ Rails.application.configure do
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false
 
+  <%- unless skip_active_storage? -%>
   # Store uploaded files on the local file system in a temporary directory
   config.active_storage.service = :test
+
+  <%- end -%>
   <%- unless options.skip_action_mailer? -%>
   config.action_mailer.perform_caching = false
 
@@ -37,8 +40,8 @@ Rails.application.configure do
   # The :test delivery method accumulates sent emails in the
   # ActionMailer::Base.deliveries array.
   config.action_mailer.delivery_method = :test
-  <%- end -%>
 
+  <%- end -%>
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb.tt
index 89d2efab2b..89d2efab2b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb.tt
index 59385cdf37..59385cdf37 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
new file mode 100644
index 0000000000..656ded4069
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
@@ -0,0 +1,20 @@
+# Define an application-wide content security policy
+# For further information see the following documentation
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
+
+Rails.application.config.content_security_policy do |p|
+  p.default_src :self, :https
+  p.font_src    :self, :https, :data
+  p.img_src     :self, :https, :data
+  p.object_src  :none
+  p.script_src  :self, :https
+  p.style_src   :self, :https, :unsafe_inline
+
+  # Specify URI for violation reports
+  # p.report_uri "/csp-violation-report-endpoint"
+end
+
+# Report CSP violations to a specified URI
+# For further information see the following documentation:
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only
+# Rails.application.config.content_security_policy_report_only = true
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb.tt
index 5a6a32d371..5a6a32d371 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb.tt
index 3b1c1b5ed1..3b1c1b5ed1 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb.tt
index 4a994e1e7b..4a994e1e7b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb.tt
index ac033bf9dc..ac033bf9dc 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb.tt
index dc1899682b..dc1899682b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/puma.rb b/railties/lib/rails/generators/rails/app/templates/config/puma.rb.tt
index 1e19380dcb..a5eccf816b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/puma.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/puma.rb.tt
@@ -26,31 +26,9 @@ environment ENV.fetch("RAILS_ENV") { "development" }
 # Use the `preload_app!` method when specifying a `workers` number.
 # This directive tells Puma to first boot the application and load code
 # before forking the application. This takes advantage of Copy On Write
-# process behavior so workers use less memory. If you use this option
-# you need to make sure to reconnect any threads in the `on_worker_boot`
-# block.
+# process behavior so workers use less memory.
 #
 # preload_app!
 
-# If you are preloading your application and using Active Record, it's
-# recommended that you close any connections to the database before workers
-# are forked to prevent connection leakage.
-#
-# before_fork do
-#   ActiveRecord::Base.connection_pool.disconnect! if defined?(ActiveRecord)
-# end
-
-# The code in the `on_worker_boot` will be called if you are using
-# clustered mode by specifying a number of `workers`. After each worker
-# process is booted, this block will be run. If you are using the `preload_app!`
-# option, you will want to use this block to reconnect to any threads
-# or connections that may have been created at application boot, as Ruby
-# cannot share connections between processes.
-#
-# on_worker_boot do
-#   ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
-# end
-#
-
 # Allow puma to be restarted by `rails restart` command.
 plugin :tmp_restart
diff --git a/railties/lib/rails/generators/rails/app/templates/config/routes.rb b/railties/lib/rails/generators/rails/app/templates/config/routes.rb.tt
index 787824f888..787824f888 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/routes.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/routes.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/secrets.yml b/railties/lib/rails/generators/rails/app/templates/config/secrets.yml
deleted file mode 100644
index ea9d47396c..0000000000
--- a/railties/lib/rails/generators/rails/app/templates/config/secrets.yml
+++ /dev/null
@@ -1,32 +0,0 @@
-# Be sure to restart your server when you modify this file.
-
-# Your secret key is used for verifying the integrity of signed cookies.
-# If you change this key, all old signed cookies will become invalid!
-
-# Make sure the secret is at least 30 characters and all random,
-# no regular words or you'll be exposed to dictionary attacks.
-# You can use `rails secret` to generate a secure secret key.
-
-# Make sure the secrets in this file are kept private
-# if you're sharing your code publicly.
-
-# Shared secrets are available across all environments.
-
-# shared:
-#   api_key: a1B2c3D4e5F6
-
-# Environmental secrets are only available for that specific environment.
-
-development:
-  secret_key_base: <%= app_secret %>
-
-test:
-  secret_key_base: <%= app_secret %>
-
-# Do not keep production secrets in the unencrypted secrets file.
-# Instead, either read values from the environment.
-# Or, use `bin/rails secrets:setup` to configure encrypted secrets
-# and move the `production:` environment over there.
-
-production:
-  secret_key_base: <%%= ENV["SECRET_KEY_BASE"] %>
diff --git a/railties/lib/rails/generators/rails/app/templates/config/spring.rb b/railties/lib/rails/generators/rails/app/templates/config/spring.rb.tt
index 9fa7863f99..9fa7863f99 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/spring.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/spring.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/storage.yml b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
index 089ed4567a..1c0cde0b09 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/storage.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
@@ -6,11 +6,11 @@ local:
   service: Disk
   root: <%%= Rails.root.join("storage") %>
 
-# Use rails secrets:edit to set the AWS secrets (as shared:aws:access_key_id|secret_access_key)
+# Use rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
 # amazon:
 #   service: S3
-#   access_key_id: <%%= Rails.application.secrets.dig(:aws, :access_key_id) %>
-#   secret_access_key: <%%= Rails.application.secrets.dig(:aws, :secret_access_key) %>
+#   access_key_id: <%%= Rails.application.credentials.dig(:aws, :access_key_id) %>
+#   secret_access_key: <%%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
 #   region: us-east-1
 #   bucket: your_own_bucket
 
@@ -18,15 +18,15 @@ local:
 # google:
 #   service: GCS
 #   project: your_project
-#   keyfile: <%%= Rails.root.join("path/to/gcs.keyfile") %>
+#   credentials: <%%= Rails.root.join("path/to/gcs.keyfile") %>
 #   bucket: your_own_bucket
 
-# Use rails secrets:edit to set the Azure Storage secret (as shared:azure_storage:storage_access_key)
+# Use rails credentials:edit to set the Azure Storage secret (as azure_storage:storage_access_key)
 # microsoft:
 #   service: AzureStorage
 #   path: your_azure_storage_path
 #   storage_account_name: your_account_name
-#   storage_access_key: <%%= Rails.application.secrets.dig(:azure_storage, :storage_access_key) %>
+#   storage_access_key: <%%= Rails.application.credentials.dig(:azure_storage, :storage_access_key) %>
 #   container: your_container_name
 
 # mirror:
diff --git a/railties/lib/rails/generators/rails/app/templates/gitignore b/railties/lib/rails/generators/rails/app/templates/gitignore.tt
index 83a7b211aa..2cd8335aba 100644
--- a/railties/lib/rails/generators/rails/app/templates/gitignore
+++ b/railties/lib/rails/generators/rails/app/templates/gitignore.tt
@@ -21,14 +21,16 @@
 !/tmp/.keep
 <% end -%>
 
+<% unless skip_active_storage? -%>
 # Ignore uploaded files in development
 /storage/*
 
+<% end -%>
 <% unless options.skip_yarn? -%>
 /node_modules
 /yarn-error.log
-<% end -%>
 
+<% end -%>
 <% unless options.api? -%>
 /public/assets
 <% end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/package.json b/railties/lib/rails/generators/rails/app/templates/package.json.tt
index 46db57dcbe..46db57dcbe 100644
--- a/railties/lib/rails/generators/rails/app/templates/package.json
+++ b/railties/lib/rails/generators/rails/app/templates/package.json.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/ruby-version b/railties/lib/rails/generators/rails/app/templates/ruby-version.tt
index c444f33b0f..c444f33b0f 100644
--- a/railties/lib/rails/generators/rails/app/templates/ruby-version
+++ b/railties/lib/rails/generators/rails/app/templates/ruby-version.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb b/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb.tt
index d19212abd5..d19212abd5 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb
+++ b/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
index 6ad1f11781..52d68cc77c 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb
+++ b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
@@ -1,3 +1,4 @@
+ENV['RAILS_ENV'] ||= 'test'
 require_relative '../config/environment'
 require 'rails/test_help'
 
diff --git a/railties/lib/rails/generators/rails/assets/templates/stylesheet.css b/railties/lib/rails/generators/rails/assets/templates/stylesheet.css
index 7594abf268..afad32db02 100644
--- a/railties/lib/rails/generators/rails/assets/templates/stylesheet.css
+++ b/railties/lib/rails/generators/rails/assets/templates/stylesheet.css
@@ -1,4 +1,4 @@
-/* 
+/*
   Place all the styles related to the matching controller here.
   They will automatically be included in application.css.
 */
diff --git a/railties/lib/rails/generators/rails/controller/templates/controller.rb b/railties/lib/rails/generators/rails/controller/templates/controller.rb.tt
index 633e0b3177..633e0b3177 100644
--- a/railties/lib/rails/generators/rails/controller/templates/controller.rb
+++ b/railties/lib/rails/generators/rails/controller/templates/controller.rb.tt
diff --git a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
index ddcccd5ce5..01a5b502f9 100644
--- a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
+++ b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
@@ -1,20 +1,17 @@
 # frozen_string_literal: true
 
-require_relative "../../base"
-require_relative "../master_key/master_key_generator"
+require "rails/generators/base"
+require "rails/generators/rails/master_key/master_key_generator"
 require "active_support/encrypted_configuration"
 
 module Rails
   module Generators
     class CredentialsGenerator < Base
-      CONFIG_PATH = "config/credentials.yml.enc"
-      KEY_PATH    = "config/master.key"
-
       def add_credentials_file
-        unless File.exist?(CONFIG_PATH)
+        unless credentials.content_path.exist?
           template = credentials_template
 
-          say "Adding #{CONFIG_PATH} to store encrypted credentials."
+          say "Adding #{credentials.content_path} to store encrypted credentials."
           say ""
           say "The following content has been encrypted with the Rails master key:"
           say ""
@@ -29,15 +26,22 @@ module Rails
       end
 
       def add_credentials_file_silently(template = nil)
-        unless File.exist?(CONFIG_PATH)
-          setup = { config_path: CONFIG_PATH, key_path: KEY_PATH, env_key: "RAILS_MASTER_KEY" }
-          ActiveSupport::EncryptedConfiguration.new(setup).write(credentials_template)
+        unless credentials.content_path.exist?
+          credentials.write(credentials_template)
         end
       end
 
       private
+        def credentials
+          ActiveSupport::EncryptedConfiguration.new(
+            config_path: "config/credentials.yml.enc",
+            key_path: "config/master.key",
+            env_key: "RAILS_MASTER_KEY"
+          )
+        end
+
         def credentials_template
-          "# amazon:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n" +
+          "# aws:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n" +
           "# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.\n" +
           "secret_key_base: #{SecureRandom.hex(64)}"
         end
diff --git a/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
new file mode 100644
index 0000000000..ddce5f6fe2
--- /dev/null
+++ b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require "rails/generators/base"
+require "active_support/encrypted_file"
+
+module Rails
+  module Generators
+    class EncryptedFileGenerator < Base
+      def add_encrypted_file(file_path, key_path)
+        unless File.exist?(file_path)
+          say "Adding #{file_path} to store encrypted content."
+          say ""
+          say "The following content has been encrypted with the encryption key:"
+          say ""
+          say template, :on_green
+          say ""
+
+          add_encrypted_file_silently(file_path, key_path)
+
+          say "You can edit encrypted file with `bin/rails encrypted:edit #{file_path}`."
+          say ""
+        end
+      end
+
+      def add_encrypted_file_silently(file_path, key_path, template = encrypted_file_template)
+        unless File.exist?(file_path)
+          setup = { content_path: file_path, key_path: key_path, env_key: "RAILS_MASTER_KEY" }
+          ActiveSupport::EncryptedFile.new(setup).write(template)
+        end
+      end
+
+      private
+        def encrypted_file_template
+          "# aws:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n"
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb b/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb
deleted file mode 100644
index d054e8cad2..0000000000
--- a/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb
+++ /dev/null
@@ -1,72 +0,0 @@
-# frozen_string_literal: true
-
-require_relative "../../base"
-require_relative "../../../secrets"
-
-module Rails
-  module Generators
-    class EncryptedSecretsGenerator < Base
-      def add_secrets_key_file
-        unless File.exist?("config/secrets.yml.key") || File.exist?("config/secrets.yml.enc")
-          key = Rails::Secrets.generate_key
-
-          say "Adding config/secrets.yml.key to store the encryption key: #{key}"
-          say ""
-          say "Save this in a password manager your team can access."
-          say ""
-          say "If you lose the key, no one, including you, can access any encrypted secrets."
-
-          say ""
-          create_file "config/secrets.yml.key", key
-          say ""
-        end
-      end
-
-      def ignore_key_file
-        if File.exist?(".gitignore")
-          unless File.read(".gitignore").include?(key_ignore)
-            say "Ignoring config/secrets.yml.key so it won't end up in Git history:"
-            say ""
-            append_to_file ".gitignore", key_ignore
-            say ""
-          end
-        else
-          say "IMPORTANT: Don't commit config/secrets.yml.key. Add this to your ignore file:"
-          say key_ignore, :on_green
-          say ""
-        end
-      end
-
-      def add_encrypted_secrets_file
-        unless (defined?(@@skip_secrets_file) && @@skip_secrets_file) || File.exist?("config/secrets.yml.enc")
-          say "Adding config/secrets.yml.enc to store secrets that needs to be encrypted."
-          say ""
-          say "For now the file contains this but it's been encrypted with the generated key:"
-          say ""
-          say Secrets.template, :on_green
-          say ""
-
-          Secrets.write(Secrets.template)
-
-          say "You can edit encrypted secrets with `bin/rails secrets:edit`."
-          say ""
-        end
-
-        say "Add this to your config/environments/production.rb:"
-        say "config.read_encrypted_secrets = true"
-      end
-
-      def self.skip_secrets_file
-        @@skip_secrets_file = true
-        yield
-      ensure
-        @@skip_secrets_file = false
-      end
-
-      private
-        def key_ignore
-          [ "", "# Ignore encrypted secrets key file.", "config/secrets.yml.key", "" ].join("\n")
-        end
-    end
-  end
-end
diff --git a/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
new file mode 100644
index 0000000000..a396a9661f
--- /dev/null
+++ b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require "pathname"
+require "rails/generators/base"
+require "active_support/encrypted_file"
+
+module Rails
+  module Generators
+    class EncryptionKeyFileGenerator < Base
+      def add_key_file(key_path)
+        key_path = Pathname.new(key_path)
+
+        unless key_path.exist?
+          key = ActiveSupport::EncryptedFile.generate_key
+
+          log "Adding #{key_path} to store the encryption key: #{key}"
+          log ""
+          log "Save this in a password manager your team can access."
+          log ""
+          log "If you lose the key, no one, including you, can access anything encrypted with it."
+
+          log ""
+          add_key_file_silently(key_path, key)
+          log ""
+        end
+      end
+
+      def add_key_file_silently(key_path, key = nil)
+        create_file key_path, key || ActiveSupport::EncryptedFile.generate_key
+      end
+
+      def ignore_key_file(key_path, ignore: key_ignore(key_path))
+        if File.exist?(".gitignore")
+          unless File.read(".gitignore").include?(ignore)
+            log "Ignoring #{key_path} so it won't end up in Git history:"
+            log ""
+            append_to_file ".gitignore", ignore
+            log ""
+          end
+        else
+          log "IMPORTANT: Don't commit #{key_path}. Add this to your ignore file:"
+          log ignore, :on_green
+          log ""
+        end
+      end
+
+      def ignore_key_file_silently(key_path, ignore: key_ignore(key_path))
+        append_to_file ".gitignore", ignore if File.exist?(".gitignore")
+      end
+
+      private
+        def key_ignore(key_path)
+          [ "", "/#{key_path}", "" ].join("\n")
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/helper/templates/helper.rb b/railties/lib/rails/generators/rails/helper/templates/helper.rb.tt
index b4173151b4..b4173151b4 100644
--- a/railties/lib/rails/generators/rails/helper/templates/helper.rb
+++ b/railties/lib/rails/generators/rails/helper/templates/helper.rb.tt
diff --git a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
index e49d3b39e0..7f57340c11 100644
--- a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
+++ b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
@@ -1,7 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../base"
 require "pathname"
+require "rails/generators/base"
+require "rails/generators/rails/encryption_key_file/encryption_key_file_generator"
 require "active_support/encrypted_file"
 
 module Rails
@@ -13,34 +14,33 @@ module Rails
         unless MASTER_KEY_PATH.exist?
           key = ActiveSupport::EncryptedFile.generate_key
 
-          say "Adding #{MASTER_KEY_PATH} to store the master encryption key: #{key}"
-          say ""
-          say "Save this in a password manager your team can access."
-          say ""
-          say "If you lose the key, no one, including you, can access anything encrypted with it."
+          log "Adding #{MASTER_KEY_PATH} to store the master encryption key: #{key}"
+          log ""
+          log "Save this in a password manager your team can access."
+          log ""
+          log "If you lose the key, no one, including you, can access anything encrypted with it."
 
-          say ""
-          create_file MASTER_KEY_PATH, key
-          say ""
-
-          ignore_master_key_file
+          log ""
+          add_master_key_file_silently(key)
+          log ""
         end
       end
 
+      def add_master_key_file_silently(key = nil)
+        key_file_generator.add_key_file_silently(MASTER_KEY_PATH, key)
+      end
+
+      def ignore_master_key_file
+        key_file_generator.ignore_key_file(MASTER_KEY_PATH, ignore: key_ignore)
+      end
+
+      def ignore_master_key_file_silently
+        key_file_generator.ignore_key_file_silently(MASTER_KEY_PATH, ignore: key_ignore)
+      end
+
       private
-        def ignore_master_key_file
-          if File.exist?(".gitignore")
-            unless File.read(".gitignore").include?(key_ignore)
-              say "Ignoring #{MASTER_KEY_PATH} so it won't end up in Git history:"
-              say ""
-              append_to_file ".gitignore", key_ignore
-              say ""
-            end
-          else
-            say "IMPORTANT: Don't commit #{MASTER_KEY_PATH}. Add this to your ignore file:"
-            say key_ignore, :on_green
-            say ""
-          end
+        def key_file_generator
+          EncryptionKeyFileGenerator.new([], options)
         end
 
         def key_ignore
diff --git a/railties/lib/rails/generators/rails/model/model_generator.rb b/railties/lib/rails/generators/rails/model/model_generator.rb
index 1dca03e0bb..de4de2cae2 100644
--- a/railties/lib/rails/generators/rails/model/model_generator.rb
+++ b/railties/lib/rails/generators/rails/model/model_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../model_helpers"
+require "rails/generators/model_helpers"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
index eb941adf95..a83c911806 100644
--- a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/slice"
-require_relative "../app/app_generator"
+require "rails/generators/rails/app/app_generator"
 require "date"
 
 module Rails
@@ -88,17 +87,18 @@ task default: :test
     end
 
     PASSTHROUGH_OPTIONS = [
-      :skip_active_record, :skip_action_mailer, :skip_javascript, :skip_action_cable, :skip_sprockets, :database,
+      :skip_active_record, :skip_active_storage, :skip_action_mailer, :skip_javascript, :skip_action_cable, :skip_sprockets, :database,
       :javascript, :skip_yarn, :api, :quiet, :pretend, :skip
     ]
 
     def generate_test_dummy(force = false)
-      opts = (options || {}).slice(*PASSTHROUGH_OPTIONS)
+      opts = (options.dup || {}).keep_if { |k, _| PASSTHROUGH_OPTIONS.map(&:to_s).include?(k) }
       opts[:force] = force
       opts[:skip_bundle] = true
       opts[:skip_listen] = true
       opts[:skip_git] = true
       opts[:skip_turbolinks] = true
+      opts[:dummy_app] = true
 
       invoke Rails::Generators::AppGenerator,
         [ File.expand_path(dummy_path, destination_root) ], opts
@@ -167,7 +167,7 @@ task default: :test
 
       gemfile_in_app_path = File.join(rails_app_path, "Gemfile")
       if File.exist? gemfile_in_app_path
-        entry = "gem '#{name}', path: '#{relative_path}'"
+        entry = "\ngem '#{name}', path: '#{relative_path}'"
         append_file gemfile_in_app_path, entry
       end
     end
@@ -263,6 +263,10 @@ task default: :test
       public_task :apply_rails_template
 
       def run_after_bundle_callbacks
+        unless @after_bundle_callbacks.empty?
+          ActiveSupport::Deprecation.warn("`after_bundle` is deprecated and will be removed in the next version of Rails. ")
+        end
+
         @after_bundle_callbacks.each do |callback|
           callback.call
         end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec b/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec.tt
index 9a8c4bf098..9a8c4bf098 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec
+++ b/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/Gemfile b/railties/lib/rails/generators/rails/plugin/templates/Gemfile.tt
index 290259b4db..290259b4db 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/Gemfile
+++ b/railties/lib/rails/generators/rails/plugin/templates/Gemfile.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE b/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE.tt
index ff2fb3ba4e..ff2fb3ba4e 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE
+++ b/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/README.md b/railties/lib/rails/generators/rails/plugin/templates/README.md.tt
index 1632409bea..1632409bea 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/README.md
+++ b/railties/lib/rails/generators/rails/plugin/templates/README.md.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/Rakefile b/railties/lib/rails/generators/rails/plugin/templates/Rakefile.tt
index f3efe21cf1..f3efe21cf1 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/Rakefile
+++ b/railties/lib/rails/generators/rails/plugin/templates/Rakefile.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb b/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb.tt
index 154452bfe5..154452bfe5 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/gitignore b/railties/lib/rails/generators/rails/plugin/templates/gitignore.tt
index e15863d860..7a68da5c4b 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/gitignore
+++ b/railties/lib/rails/generators/rails/plugin/templates/gitignore.tt
@@ -11,5 +11,8 @@ pkg/
 <%= dummy_path %>/node_modules/
 <%= dummy_path %>/yarn-error.log
 <% end -%>
+<% unless skip_active_storage? -%>
+<%= dummy_path %>/storage/
+<% end -%>
 <%= dummy_path %>/tmp/
 <% end -%>
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb.tt
index 3285055eb7..3285055eb7 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
index 8938770fc4..8938770fc4 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
index 7bdf4ee5fb..7bdf4ee5fb 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb.tt
index b08f4ef9ae..b08f4ef9ae 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake b/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake.tt
index 88a2c4120f..88a2c4120f 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb b/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb.tt
index 47b56ae3df..06ffe2f1ed 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb.tt
@@ -8,10 +8,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb b/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb.tt
index c9aef85d40..c9aef85d40 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js b/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js.tt
index 03937cf8ff..03937cf8ff 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js b/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js.tt
index 2f23844f5e..2f23844f5e 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
index e54c6461cc..f3d80c87f5 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
@@ -10,4 +10,7 @@
 // Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
 // about supported directives.
 //
+<% unless skip_active_storage? -%>
+//= require activestorage
+<% end -%>
 //= require_tree .
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb b/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb.tt
index 694510edc0..694510edc0 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb b/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb.tt
index 1ee05d7871..1ee05d7871 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb b/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb.tt
index d19212abd5..d19212abd5 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb b/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb.tt
index 29e59d8407..29e59d8407 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb b/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb.tt
index 7fa9973931..755d19ef5d 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb.tt
@@ -1,3 +1,6 @@
+# Configure Rails Environment
+ENV["RAILS_ENV"] = "test"
+
 require_relative "<%= File.join('..', options[:dummy_path], 'config/environment') -%>"
 <% unless options[:skip_active_record] -%>
 ActiveRecord::Migrator.migrations_paths = [File.expand_path("../<%= options[:dummy_path] -%>/db/migrate", __dir__)]
diff --git a/railties/lib/rails/generators/rails/resource/USAGE b/railties/lib/rails/generators/rails/resource/USAGE
index e359cd574f..66d0ee546a 100644
--- a/railties/lib/rails/generators/rails/resource/USAGE
+++ b/railties/lib/rails/generators/rails/resource/USAGE
@@ -1,6 +1,6 @@
 Description:
     Stubs out a new resource including an empty model and controller suitable
-    for a restful, resource-oriented application. Pass the singular model name,
+    for a RESTful, resource-oriented application. Pass the singular model name,
     either CamelCased or under_scored, as the first argument, and an optional
     list of attribute pairs.
 
diff --git a/railties/lib/rails/generators/rails/resource/resource_generator.rb b/railties/lib/rails/generators/rails/resource/resource_generator.rb
index 74b1574863..3ba25ef0fe 100644
--- a/railties/lib/rails/generators/rails/resource/resource_generator.rb
+++ b/railties/lib/rails/generators/rails/resource/resource_generator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../resource_helpers"
-require_relative "../model/model_generator"
+require "rails/generators/resource_helpers"
+require "rails/generators/rails/model/model_generator"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb
index c0fb873d36..8beb7416c0 100644
--- a/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../resource/resource_generator"
+require "rails/generators/rails/resource/resource_generator"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb b/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb
index 601a4b3a6e..7030561a33 100644
--- a/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb
+++ b/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../resource_helpers"
+require "rails/generators/resource_helpers"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb b/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb.tt
index 400afec6dc..400afec6dc 100644
--- a/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb
+++ b/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb.tt
diff --git a/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb b/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb.tt
index 42b9e34274..05f1c2b2d3 100644
--- a/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb
+++ b/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb.tt
@@ -29,7 +29,7 @@ class <%= controller_class_name %>Controller < ApplicationController
     @<%= singular_table_name %> = <%= orm_class.build(class_name, "#{singular_table_name}_params") %>
 
     if @<%= orm_instance.save %>
-      redirect_to @<%= singular_table_name %>, notice: <%= "'#{human_name} was successfully created.'" %>
+      redirect_to <%= redirect_resource_name %>, notice: <%= "'#{human_name} was successfully created.'" %>
     else
       render :new
     end
@@ -38,7 +38,7 @@ class <%= controller_class_name %>Controller < ApplicationController
   # PATCH/PUT <%= route_url %>/1
   def update
     if @<%= orm_instance.update("#{singular_table_name}_params") %>
-      redirect_to @<%= singular_table_name %>, notice: <%= "'#{human_name} was successfully updated.'" %>
+      redirect_to <%= redirect_resource_name %>, notice: <%= "'#{human_name} was successfully updated.'" %>
     else
       render :edit
     end
diff --git a/railties/lib/rails/generators/rails/task/templates/task.rb b/railties/lib/rails/generators/rails/task/templates/task.rb.tt
index 1e3ed5f158..1e3ed5f158 100644
--- a/railties/lib/rails/generators/rails/task/templates/task.rb
+++ b/railties/lib/rails/generators/rails/task/templates/task.rb.tt
diff --git a/railties/lib/rails/generators/resource_helpers.rb b/railties/lib/rails/generators/resource_helpers.rb
index 8bd5110940..a146a8fda6 100644
--- a/railties/lib/rails/generators/resource_helpers.rb
+++ b/railties/lib/rails/generators/resource_helpers.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "active_model"
-require_relative "model_helpers"
+require "rails/generators/active_model"
+require "rails/generators/model_helpers"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/test_case.rb b/railties/lib/rails/generators/test_case.rb
index 9c06eed95a..5c71bf0be9 100644
--- a/railties/lib/rails/generators/test_case.rb
+++ b/railties/lib/rails/generators/test_case.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "../generators"
-require_relative "testing/behaviour"
-require_relative "testing/setup_and_teardown"
-require_relative "testing/assertions"
+require "rails/generators"
+require "rails/generators/testing/behaviour"
+require "rails/generators/testing/setup_and_teardown"
+require "rails/generators/testing/assertions"
 require "fileutils"
 
 module Rails
diff --git a/railties/lib/rails/generators/test_unit.rb b/railties/lib/rails/generators/test_unit.rb
index 1aa03ace99..1005ac557c 100644
--- a/railties/lib/rails/generators/test_unit.rb
+++ b/railties/lib/rails/generators/test_unit.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "named_base"
+require "rails/generators/named_base"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/controller/controller_generator.rb b/railties/lib/rails/generators/test_unit/controller/controller_generator.rb
index 3947b74205..1a9ac6bf2a 100644
--- a/railties/lib/rails/generators/test_unit/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/test_unit/controller/controller_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb b/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb.tt
index 4efa977a89..ff41fef9e9 100644
--- a/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/generator/generator_generator.rb b/railties/lib/rails/generators/test_unit/generator/generator_generator.rb
index 9f79e9eee1..19be4f2f51 100644
--- a/railties/lib/rails/generators/test_unit/generator/generator_generator.rb
+++ b/railties/lib/rails/generators/test_unit/generator/generator_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb b/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb.tt
index e6fb6c5ff4..a7f1fc4fba 100644
--- a/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb
+++ b/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 require '<%= generator_path %>'
 
diff --git a/railties/lib/rails/generators/test_unit/helper/helper_generator.rb b/railties/lib/rails/generators/test_unit/helper/helper_generator.rb
index 1c60c3573f..77308dcf7d 100644
--- a/railties/lib/rails/generators/test_unit/helper/helper_generator.rb
+++ b/railties/lib/rails/generators/test_unit/helper/helper_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/integration/integration_generator.rb b/railties/lib/rails/generators/test_unit/integration/integration_generator.rb
index c859ba5e4e..ae307c5cd9 100644
--- a/railties/lib/rails/generators/test_unit/integration/integration_generator.rb
+++ b/railties/lib/rails/generators/test_unit/integration/integration_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb b/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb.tt
index 65708b6c3b..118e0f1271 100644
--- a/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb
+++ b/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/job/job_generator.rb b/railties/lib/rails/generators/test_unit/job/job_generator.rb
index cbbcd1cd4e..a99ce914c0 100644
--- a/railties/lib/rails/generators/test_unit/job/job_generator.rb
+++ b/railties/lib/rails/generators/test_unit/job/job_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
@@ -8,7 +8,7 @@ module TestUnit # :nodoc:
       check_class_collision suffix: "JobTest"
 
       def create_test_file
-        template "unit_test.rb.erb", File.join("test/jobs", class_path, "#{file_name}_job_test.rb")
+        template "unit_test.rb", File.join("test/jobs", class_path, "#{file_name}_job_test.rb")
       end
     end
   end
diff --git a/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.erb b/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.tt
index f5351d0ec6..f5351d0ec6 100644
--- a/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.erb
+++ b/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.tt
diff --git a/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb b/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb
index 45f82158e9..610d47a729 100644
--- a/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb
+++ b/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb b/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb.tt
index 1ec3a2f360..a2f2d30de5 100644
--- a/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb b/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb.tt
index 9876210b6c..b063cbc47b 100644
--- a/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb
+++ b/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 <% module_namespacing do -%>
 # Preview all emails at http://localhost:3000/rails/mailers/<%= file_path %>_mailer
 class <%= class_name %>MailerPreview < ActionMailer::Preview
diff --git a/railties/lib/rails/generators/test_unit/model/model_generator.rb b/railties/lib/rails/generators/test_unit/model/model_generator.rb
index 2b1cc50c20..02d7502592 100644
--- a/railties/lib/rails/generators/test_unit/model/model_generator.rb
+++ b/railties/lib/rails/generators/test_unit/model/model_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml b/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml.tt
index 0681780c97..0681780c97 100644
--- a/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml
+++ b/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml.tt
diff --git a/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb b/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb.tt
index 5f1ffeb33b..c9bc7d5b90 100644
--- a/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb
+++ b/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb b/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb
index 10fe27b2c3..0657bc2389 100644
--- a/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb b/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb
index 2147b09568..30a861f09d 100644
--- a/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb
+++ b/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb
@@ -1,4 +1,2 @@
-# frozen_string_literal: true
-
 require 'active_support/testing/autorun'
 require 'active_support'
diff --git a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
index 23d5c63614..b6c13b41ae 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
-require_relative "../../resource_helpers"
+require "rails/generators/test_unit"
+require "rails/generators/resource_helpers"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb b/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb.tt
index 2ef93b8aea..f21861d8e6 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb b/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb.tt
index bcf9392bd1..195d60be20 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb b/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb.tt
index ba8bdc192e..f83f5a5c62 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require "application_system_test_case"
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/system/system_generator.rb b/railties/lib/rails/generators/test_unit/system/system_generator.rb
index d3acbfd738..08504d4124 100644
--- a/railties/lib/rails/generators/test_unit/system/system_generator.rb
+++ b/railties/lib/rails/generators/test_unit/system/system_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb b/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb.tt
index c05709aff8..d19212abd5 100644
--- a/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb
+++ b/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require "test_helper"
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
diff --git a/railties/lib/rails/generators/test_unit/system/templates/system_test.rb b/railties/lib/rails/generators/test_unit/system/templates/system_test.rb.tt
index cfac061cd1..b5ce2ba5c8 100644
--- a/railties/lib/rails/generators/test_unit/system/templates/system_test.rb
+++ b/railties/lib/rails/generators/test_unit/system/templates/system_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require "application_system_test_case"
 
 class <%= class_name.pluralize %>Test < ApplicationSystemTestCase
diff --git a/railties/lib/rails/generators/testing/behaviour.rb b/railties/lib/rails/generators/testing/behaviour.rb
index 97a09c1166..6ab88bd59f 100644
--- a/railties/lib/rails/generators/testing/behaviour.rb
+++ b/railties/lib/rails/generators/testing/behaviour.rb
@@ -6,7 +6,7 @@ require "active_support/core_ext/hash/reverse_merge"
 require "active_support/core_ext/kernel/reporting"
 require "active_support/testing/stream"
 require "active_support/concern"
-require_relative "../../generators"
+require "rails/generators"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/info_controller.rb b/railties/lib/rails/info_controller.rb
index 6535b5b6ad..b4f4a5922a 100644
--- a/railties/lib/rails/info_controller.rb
+++ b/railties/lib/rails/info_controller.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "application_controller"
+require "rails/application_controller"
 require "action_dispatch/routing/inspector"
 
 class Rails::InfoController < Rails::ApplicationController # :nodoc:
diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 6bd3161fdd..66636e5d6b 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "application_controller"
+require "rails/application_controller"
 
 class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugExceptions::RESCUES_TEMPLATE_PATH
diff --git a/railties/lib/rails/plugin/test.rb b/railties/lib/rails/plugin/test.rb
index 2426521e35..18b6fd1757 100644
--- a/railties/lib/rails/plugin/test.rb
+++ b/railties/lib/rails/plugin/test.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../test_unit/runner"
-require_relative "../test_unit/reporter"
+require "rails/test_unit/runner"
+require "rails/test_unit/reporter"
 
 Rails::TestUnitReporter.executable = "bin/test"
 
diff --git a/railties/lib/rails/railtie.rb b/railties/lib/rails/railtie.rb
index 42c4a82b1b..88dd932370 100644
--- a/railties/lib/rails/railtie.rb
+++ b/railties/lib/rails/railtie.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "initializable"
+require "rails/initializable"
 require "active_support/inflector"
 require "active_support/core_ext/module/introspection"
 require "active_support/core_ext/module/delegation"
diff --git a/railties/lib/rails/railtie/configuration.rb b/railties/lib/rails/railtie/configuration.rb
index d9997759f2..48853129bc 100644
--- a/railties/lib/rails/railtie/configuration.rb
+++ b/railties/lib/rails/railtie/configuration.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../configuration"
+require "rails/configuration"
 
 module Rails
   class Railtie
diff --git a/railties/lib/rails/secrets.rb b/railties/lib/rails/secrets.rb
index aea72b2d01..30e3478c9b 100644
--- a/railties/lib/rails/secrets.rb
+++ b/railties/lib/rails/secrets.rb
@@ -32,23 +32,10 @@ module Rails
         end
       end
 
-      def generate_key
-        SecureRandom.hex(OpenSSL::Cipher.new(@cipher).key_len)
-      end
-
       def key
         ENV["RAILS_MASTER_KEY"] || read_key_file || handle_missing_key
       end
 
-      def template
-        <<-end_of_template.strip_heredoc
-          # See `secrets.yml` for tips on generating suitable keys.
-          # production:
-          #   external_api_key: 1466aac22e6a869134be3d09b9e89232fc2c2289
-
-        end_of_template
-      end
-
       def encrypt(data)
         encryptor.encrypt_and_sign(data)
       end
@@ -70,10 +57,6 @@ module Rails
         writing(read, &block)
       end
 
-      def read_template_for_editing(&block)
-        writing(template, &block)
-      end
-
       private
         def handle_missing_key
           raise MissingKeyError
diff --git a/railties/lib/rails/tasks/annotations.rake b/railties/lib/rails/tasks/annotations.rake
index 931f81ac7e..93bc66e2db 100644
--- a/railties/lib/rails/tasks/annotations.rake
+++ b/railties/lib/rails/tasks/annotations.rake
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../source_annotation_extractor"
+require "rails/source_annotation_extractor"
 
 desc "Enumerate all annotations (use notes:optimize, :fixme, :todo for focus)"
 task :notes do
diff --git a/railties/lib/rails/tasks/dev.rake b/railties/lib/rails/tasks/dev.rake
index 90fd3ccd8b..5aea6f7dc5 100644
--- a/railties/lib/rails/tasks/dev.rake
+++ b/railties/lib/rails/tasks/dev.rake
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../dev_caching"
+require "rails/dev_caching"
 
 namespace :dev do
   desc "Toggle development mode caching on/off"
diff --git a/railties/lib/rails/tasks/engine.rake b/railties/lib/rails/tasks/engine.rake
index 3ce49a1641..8d77904210 100644
--- a/railties/lib/rails/tasks/engine.rake
+++ b/railties/lib/rails/tasks/engine.rake
@@ -8,7 +8,7 @@ task "load_app" do
     task update: [ "update:bin" ]
 
     namespace :update do
-      require_relative "../engine/updater"
+      require "rails/engine/updater"
       # desc "Adds new executables to the engine bin/ directory"
       task :bin do
         Rails::Engine::Updater.run(:create_bin_files)
@@ -53,7 +53,7 @@ namespace :db do
   desc "Rolls the schema back to the previous version (specify steps w/ STEP=n)."
   app_task "rollback"
 
-  desc "Create a db/schema.rb file that can be portably used against any DB supported by Active Record"
+  desc "Create a db/schema.rb file that can be portably used against any database supported by Active Record"
   app_task "schema:dump"
 
   desc "Load a schema.rb file into the database"
@@ -62,7 +62,7 @@ namespace :db do
   desc "Load the seed data from db/seeds.rb"
   app_task "seed"
 
-  desc "Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the db first)"
+  desc "Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the database first)"
   app_task "setup"
 
   desc "Dump the database structure to an SQL file"
@@ -70,6 +70,9 @@ namespace :db do
 
   desc "Retrieves the current schema version number"
   app_task "version"
+
+  # desc 'Load the test schema'
+  app_task "test:prepare"
 end
 
 def find_engine_path(path)
diff --git a/railties/lib/rails/tasks/framework.rake b/railties/lib/rails/tasks/framework.rake
index 8931aabcda..7dfcd14bd0 100644
--- a/railties/lib/rails/tasks/framework.rake
+++ b/railties/lib/rails/tasks/framework.rake
@@ -9,8 +9,8 @@ namespace :app do
     template = ENV["LOCATION"]
     raise "No LOCATION value given. Please set LOCATION either as path to a file or a URL" if template.blank?
     template = File.expand_path(template) if template !~ %r{\A[A-Za-z][A-Za-z0-9+\-\.]*://}
-    require_relative "../generators"
-    require_relative "../generators/rails/app/app_generator"
+    require "rails/generators"
+    require "rails/generators/rails/app/app_generator"
     generator = Rails::Generators::AppGenerator.new [Rails.root], {}, { destination_root: Rails.root }
     generator.apply template, verbose: false
   end
@@ -38,7 +38,7 @@ namespace :app do
   end
 
   namespace :update do
-    require_relative "../app_updater"
+    require "rails/app_updater"
 
     # desc "Update config/boot.rb from your current rails install"
     task :configs do
diff --git a/railties/lib/rails/tasks/statistics.rake b/railties/lib/rails/tasks/statistics.rake
index 0449a13586..594db91eec 100644
--- a/railties/lib/rails/tasks/statistics.rake
+++ b/railties/lib/rails/tasks/statistics.rake
@@ -26,6 +26,6 @@ end.select { |name, dir| File.directory?(dir) }
 
 desc "Report code statistics (KLOCs, etc) from the application or engine"
 task :stats do
-  require_relative "../code_statistics"
+  require "rails/code_statistics"
   CodeStatistics.new(*STATS_DIRECTORIES).to_s
 end
diff --git a/railties/lib/rails/test_help.rb b/railties/lib/rails/test_help.rb
index f755474488..732c5c1e1f 100644
--- a/railties/lib/rails/test_help.rb
+++ b/railties/lib/rails/test_help.rb
@@ -8,7 +8,7 @@ require "active_support/test_case"
 require "action_controller"
 require "action_controller/test_case"
 require "action_dispatch/testing/integration"
-require_relative "generators/test_case"
+require "rails/generators/test_case"
 
 require "active_support/testing/autorun"
 
diff --git a/railties/lib/rails/test_unit/railtie.rb b/railties/lib/rails/test_unit/railtie.rb
index 05f9a177d0..42b6daa3d1 100644
--- a/railties/lib/rails/test_unit/railtie.rb
+++ b/railties/lib/rails/test_unit/railtie.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "line_filtering"
+require "rails/test_unit/line_filtering"
 
 if defined?(Rake.application) && Rake.application.top_level_tasks.grep(/^(default$|test(:|$))/).any?
   ENV["RAILS_ENV"] ||= Rake.application.options.show_tasks ? "development" : "test"
diff --git a/railties/lib/rails/test_unit/runner.rb b/railties/lib/rails/test_unit/runner.rb
index 5c2f6451e2..de5744c662 100644
--- a/railties/lib/rails/test_unit/runner.rb
+++ b/railties/lib/rails/test_unit/runner.rb
@@ -13,7 +13,7 @@ module Rails
       class << self
         def attach_before_load_options(opts)
           opts.on("--warnings", "-w", "Run with Ruby warnings enabled") {}
-          opts.on("--environment", "-e", "Run tests in the ENV environment") {}
+          opts.on("-e", "--environment ENV", "Run tests in the ENV environment") {}
         end
 
         def parse_options(argv)
diff --git a/railties/lib/rails/test_unit/testing.rake b/railties/lib/rails/test_unit/testing.rake
index 18d699f806..32ac27a135 100644
--- a/railties/lib/rails/test_unit/testing.rake
+++ b/railties/lib/rails/test_unit/testing.rake
@@ -2,7 +2,7 @@
 
 gem "minitest"
 require "minitest"
-require_relative "runner"
+require "rails/test_unit/runner"
 
 task default: :test
 
diff --git a/railties/lib/rails/welcome_controller.rb b/railties/lib/rails/welcome_controller.rb
index 0cb43e0f31..5b84b57679 100644
--- a/railties/lib/rails/welcome_controller.rb
+++ b/railties/lib/rails/welcome_controller.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "application_controller"
+require "rails/application_controller"
 
 class Rails::WelcomeController < Rails::ApplicationController # :nodoc:
   layout false
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index c1a80eaeaf..edb6190ed0 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -487,6 +487,32 @@ module ApplicationTests
       assert_equal "some_value", Rails.application.message_verifier(:sensitive_value).verify(message)
     end
 
+    test "config.secret_token is deprecated" do
+      app_file "config/initializers/secret_token.rb", <<-RUBY
+        Rails.application.config.secret_token = "b3c631c314c0bbca50c1b2843150fe33"
+      RUBY
+
+      app "production"
+
+      assert_deprecated(/secret_token/) do
+        app.secrets
+      end
+    end
+
+    test "secrets.secret_token is deprecated" do
+      app_file "config/secrets.yml", <<-YAML
+        production:
+          secret_token: "b3c631c314c0bbca50c1b2843150fe33"
+      YAML
+
+      app "production"
+
+      assert_deprecated(/secret_token/) do
+        app.secrets
+      end
+    end
+
+
     test "raises when secret_key_base is blank" do
       app_file "config/initializers/secret_token.rb", <<-RUBY
         Rails.application.credentials.secret_key_base = nil
@@ -731,6 +757,68 @@ module ApplicationTests
       assert_match(/label/, last_response.body)
     end
 
+    test "form_with can be configured with form_with_generates_ids" do
+      app_file "config/initializers/form_builder.rb", <<-RUBY
+      Rails.configuration.action_view.form_with_generates_ids = false
+      RUBY
+
+      app_file "app/models/post.rb", <<-RUBY
+      class Post
+        include ActiveModel::Model
+        attr_accessor :name
+      end
+      RUBY
+
+      app_file "app/controllers/posts_controller.rb", <<-RUBY
+      class PostsController < ApplicationController
+        def index
+          render inline: "<%= begin; form_with(model: Post.new) {|f| f.text_field(:name)}; rescue => e; e.to_s; end %>"
+        end
+      end
+      RUBY
+
+      add_to_config <<-RUBY
+        routes.prepend do
+          resources :posts
+        end
+      RUBY
+
+      app "development"
+
+      get "/posts"
+
+      assert_no_match(/id=('|")post_name('|")/, last_response.body)
+    end
+
+    test "form_with outputs ids by default" do
+      app_file "app/models/post.rb", <<-RUBY
+      class Post
+        include ActiveModel::Model
+        attr_accessor :name
+      end
+      RUBY
+
+      app_file "app/controllers/posts_controller.rb", <<-RUBY
+      class PostsController < ApplicationController
+        def index
+          render inline: "<%= begin; form_with(model: Post.new) {|f| f.text_field(:name)}; rescue => e; e.to_s; end %>"
+        end
+      end
+      RUBY
+
+      add_to_config <<-RUBY
+        routes.prepend do
+          resources :posts
+        end
+      RUBY
+
+      app "development"
+
+      get "/posts"
+
+      assert_match(/id=('|")post_name('|")/, last_response.body)
+    end
+
     test "form_with can be configured with form_with_generates_remote_forms" do
       app_file "config/initializers/form_builder.rb", <<-RUBY
       Rails.configuration.action_view.form_with_generates_remote_forms = false
diff --git a/railties/test/application/content_security_policy_test.rb b/railties/test/application/content_security_policy_test.rb
new file mode 100644
index 0000000000..97f2957c33
--- /dev/null
+++ b/railties/test/application/content_security_policy_test.rb
@@ -0,0 +1,197 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "rack/test"
+
+module ApplicationTests
+  class ContentSecurityPolicyTest < ActiveSupport::TestCase
+    include ActiveSupport::Testing::Isolation
+    include Rack::Test::Methods
+
+    def setup
+      build_app
+    end
+
+    def teardown
+      teardown_app
+    end
+
+    test "default content security policy is empty" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_equal ";", last_response.headers["Content-Security-Policy"]
+    end
+
+    test "global content security policy in an initializer" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:;"
+    end
+
+    test "global report only content security policy in an initializer" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+
+        Rails.application.config.content_security_policy_report_only = true
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:;", report_only: true
+    end
+
+    test "override content security policy in a controller" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          content_security_policy do |p|
+            p.default_src "https://example.com"
+          end
+
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src https://example.com;"
+    end
+
+    test "override content security policy to report only in a controller" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          content_security_policy_report_only
+
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:;", report_only: true
+    end
+
+    test "global content security policy added to rack app" do
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+
+          app = ->(env) {
+            [200, { "Content-Type" => "text/html" }, ["<p>Hello, World!</p>"]]
+          }
+
+          root to: app
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:;"
+    end
+
+    private
+
+      def assert_policy(expected, report_only: false)
+        assert_equal 200, last_response.status
+
+        if report_only
+          expected_header = "Content-Security-Policy-Report-Only"
+          unexpected_header = "Content-Security-Policy"
+        else
+          expected_header = "Content-Security-Policy"
+          unexpected_header = "Content-Security-Policy-Report-Only"
+        end
+
+        assert_nil last_response.headers[unexpected_header]
+        assert_equal expected, last_response.headers[expected_header]
+      end
+  end
+end
diff --git a/railties/test/application/dbconsole_test.rb b/railties/test/application/dbconsole_test.rb
index ba04c81b4d..8eb293c179 100644
--- a/railties/test/application/dbconsole_test.rb
+++ b/railties/test/application/dbconsole_test.rb
@@ -19,21 +19,19 @@ module ApplicationTests
     end
 
     def test_use_value_defined_in_environment_file_in_database_yml
-      Dir.chdir(app_path) do
-        app_file "config/database.yml", <<-YAML
-          development:
-             database: <%= Rails.application.config.database %>
-             adapter: sqlite3
-             pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-             timeout: 5000
-        YAML
+      app_file "config/database.yml", <<-YAML
+        development:
+           database: <%= Rails.application.config.database %>
+           adapter: sqlite3
+           pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+           timeout: 5000
+      YAML
 
-        app_file "config/environments/development.rb", <<-RUBY
-          Rails.application.configure do
-            config.database = "db/development.sqlite3"
-          end
-        RUBY
-      end
+      app_file "config/environments/development.rb", <<-RUBY
+        Rails.application.configure do
+          config.database = "db/development.sqlite3"
+        end
+      RUBY
 
       master, slave = PTY.open
       spawn_dbconsole(slave)
@@ -43,22 +41,20 @@ module ApplicationTests
     end
 
     def test_respect_environment_option
-      Dir.chdir(app_path) do
-        app_file "config/database.yml", <<-YAML
-          default: &default
-            adapter: sqlite3
-            pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-            timeout: 5000
+      app_file "config/database.yml", <<-YAML
+        default: &default
+          adapter: sqlite3
+          pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+          timeout: 5000
 
-          development:
-            <<: *default
-            database: db/development.sqlite3
+        development:
+          <<: *default
+          database: db/development.sqlite3
 
-          production:
-            <<: *default
-            database: db/production.sqlite3
-        YAML
-      end
+        production:
+          <<: *default
+          database: db/production.sqlite3
+      YAML
 
       master, slave = PTY.open
       spawn_dbconsole(slave, "-e production")
diff --git a/railties/test/application/generators_test.rb b/railties/test/application/generators_test.rb
index 47c815d221..e5e557d204 100644
--- a/railties/test/application/generators_test.rb
+++ b/railties/test/application/generators_test.rb
@@ -188,10 +188,11 @@ module ApplicationTests
       Rails::Command.send(:remove_const, "APP_PATH")
     end
 
-    test "help does not show hidden namespaces" do
+    test "help does not show hidden namespaces and hidden commands" do
       FileUtils.cd(rails_root) do
         output = rails("generate", "--help")
         assert_no_match "active_record:migration", output
+        assert_no_match "credentials", output
 
         output = rails("destroy", "--help")
         assert_no_match "active_record:migration", output
diff --git a/railties/test/application/integration_test_case_test.rb b/railties/test/application/integration_test_case_test.rb
index 9edc907fce..c08761092b 100644
--- a/railties/test/application/integration_test_case_test.rb
+++ b/railties/test/application/integration_test_case_test.rb
@@ -1,10 +1,11 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
+require "env_helpers"
 
 module ApplicationTests
   class IntegrationTestCaseTest < ActiveSupport::TestCase
-    include ActiveSupport::Testing::Isolation
+    include ActiveSupport::Testing::Isolation, EnvHelpers
 
     setup do
       build_app
@@ -39,13 +40,14 @@ module ApplicationTests
         end
       RUBY
 
+      with_rails_env("test") { rails("db:migrate") }
       output = rails("test")
       assert_match(/0 failures, 0 errors/, output)
     end
   end
 
   class IntegrationTestDefaultApp < ActiveSupport::TestCase
-    include ActiveSupport::Testing::Isolation
+    include ActiveSupport::Testing::Isolation, EnvHelpers
 
     setup do
       build_app
@@ -66,6 +68,7 @@ module ApplicationTests
         end
       RUBY
 
+      with_rails_env("test") { rails("db:migrate") }
       output = rails("test")
       assert_match(/0 failures, 0 errors/, output)
     end
diff --git a/railties/test/application/loading_test.rb b/railties/test/application/loading_test.rb
index 11c886e991..de1e240fd3 100644
--- a/railties/test/application/loading_test.rb
+++ b/railties/test/application/loading_test.rb
@@ -300,7 +300,7 @@ class LoadingTest < ActiveSupport::TestCase
       end
     MIGRATION
 
-    Dir.chdir(app_path) { `rake db:migrate` }
+    rails("db:migrate")
     require "#{rails_root}/config/environment"
 
     get "/title"
@@ -314,7 +314,7 @@ class LoadingTest < ActiveSupport::TestCase
       end
     MIGRATION
 
-    Dir.chdir(app_path) { `rake db:migrate` }
+    rails("db:migrate")
 
     get "/body"
     assert_equal "BODY", last_response.body
diff --git a/railties/test/application/middleware/cookies_test.rb b/railties/test/application/middleware/cookies_test.rb
index 23f1ec3e35..ecb4ee3446 100644
--- a/railties/test/application/middleware/cookies_test.rb
+++ b/railties/test/application/middleware/cookies_test.rb
@@ -1,10 +1,12 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
+require "rack/test"
 
 module ApplicationTests
   class CookiesTest < ActiveSupport::TestCase
     include ActiveSupport::Testing::Isolation
+    include Rack::Test::Methods
 
     def new_app
       File.expand_path("#{app_path}/../new_app")
@@ -15,6 +17,10 @@ module ApplicationTests
       FileUtils.rm_rf("#{app_path}/config/environments")
     end
 
+    def app
+      Rails.application
+    end
+
     def teardown
       teardown_app
       FileUtils.rm_rf(new_app) if File.directory?(new_app)
@@ -44,5 +50,144 @@ module ApplicationTests
       require "#{app_path}/config/environment"
       assert_equal false, ActionDispatch::Cookies::CookieJar.always_write_cookie
     end
+
+    test "signed cookies with SHA512 digest and rotated out SHA256 and SHA1 digests" do
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          get  ':controller(/:action)'
+          post ':controller(/:action)'
+        end
+      RUBY
+
+      controller :foo, <<-RUBY
+        class FooController < ActionController::Base
+          protect_from_forgery with: :null_session
+
+          def write_raw_cookie_sha1
+            cookies[:signed_cookie] = TestVerifiers.sha1.generate("signed cookie")
+            head :ok
+          end
+
+          def write_raw_cookie_sha256
+            cookies[:signed_cookie] = TestVerifiers.sha256.generate("signed cookie")
+            head :ok
+          end
+
+          def read_signed
+            render plain: cookies.signed[:signed_cookie].inspect
+          end
+
+          def read_raw_cookie
+            render plain: cookies[:signed_cookie]
+          end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        sha1_secret   = Rails.application.key_generator.generate_key("sha1")
+        sha256_secret = Rails.application.key_generator.generate_key("sha256")
+
+        ::TestVerifiers = Class.new do
+          class_attribute :sha1, default: ActiveSupport::MessageVerifier.new(sha1_secret, digest: "SHA1")
+          class_attribute :sha256, default: ActiveSupport::MessageVerifier.new(sha256_secret, digest: "SHA256")
+        end
+
+        config.action_dispatch.signed_cookie_digest = "SHA512"
+        config.action_dispatch.signed_cookie_salt = "sha512 salt"
+
+        config.action_dispatch.cookies_rotations.tap do |cookies|
+          cookies.rotate :signed, sha1_secret,   digest: "SHA1"
+          cookies.rotate :signed, sha256_secret, digest: "SHA256"
+        end
+      RUBY
+
+      require "#{app_path}/config/environment"
+
+      verifier_sha512 = ActiveSupport::MessageVerifier.new(app.key_generator.generate_key("sha512 salt"), digest: :SHA512)
+
+      get "/foo/write_raw_cookie_sha1"
+      get "/foo/read_signed"
+      assert_equal "signed cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "signed cookie", verifier_sha512.verify(last_response.body)
+
+      get "/foo/write_raw_cookie_sha256"
+      get "/foo/read_signed"
+      assert_equal "signed cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "signed cookie", verifier_sha512.verify(last_response.body)
+    end
+
+    test "encrypted cookies rotating multiple encryption keys" do
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          get  ':controller(/:action)'
+          post ':controller(/:action)'
+        end
+      RUBY
+
+      controller :foo, <<-RUBY
+        class FooController < ActionController::Base
+          protect_from_forgery with: :null_session
+
+          def write_raw_cookie_one
+            cookies[:encrypted_cookie] = TestEncryptors.first_gcm.encrypt_and_sign("encrypted cookie")
+            head :ok
+          end
+
+          def write_raw_cookie_two
+            cookies[:encrypted_cookie] = TestEncryptors.second_gcm.encrypt_and_sign("encrypted cookie")
+            head :ok
+          end
+
+          def read_encrypted
+            render plain: cookies.encrypted[:encrypted_cookie].inspect
+          end
+
+          def read_raw_cookie
+            render plain: cookies[:encrypted_cookie]
+          end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        first_secret  = Rails.application.key_generator.generate_key("first", 32)
+        second_secret = Rails.application.key_generator.generate_key("second", 32)
+
+        ::TestEncryptors = Class.new do
+          class_attribute :first_gcm,  default: ActiveSupport::MessageEncryptor.new(first_secret, cipher: "aes-256-gcm")
+          class_attribute :second_gcm, default: ActiveSupport::MessageEncryptor.new(second_secret, cipher: "aes-256-gcm")
+        end
+
+        config.action_dispatch.use_authenticated_cookie_encryption = true
+        config.action_dispatch.encrypted_cookie_cipher = "aes-256-gcm"
+        config.action_dispatch.authenticated_encrypted_cookie_salt = "salt"
+
+        config.action_dispatch.cookies_rotations.tap do |cookies|
+          cookies.rotate :encrypted, first_secret
+          cookies.rotate :encrypted, second_secret
+        end
+      RUBY
+
+      require "#{app_path}/config/environment"
+
+      encryptor = ActiveSupport::MessageEncryptor.new(app.key_generator.generate_key("salt", 32), cipher: "aes-256-gcm")
+
+      get "/foo/write_raw_cookie_one"
+      get "/foo/read_encrypted"
+      assert_equal "encrypted cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "encrypted cookie", encryptor.decrypt_and_verify(last_response.body)
+
+      get "/foo/write_raw_cookie_sha256"
+      get "/foo/read_encrypted"
+      assert_equal "encrypted cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "encrypted cookie", encryptor.decrypt_and_verify(last_response.body)
+    end
   end
 end
diff --git a/railties/test/application/middleware/exceptions_test.rb b/railties/test/application/middleware/exceptions_test.rb
index 75afeec905..2d659ade8d 100644
--- a/railties/test/application/middleware/exceptions_test.rb
+++ b/railties/test/application/middleware/exceptions_test.rb
@@ -102,7 +102,7 @@ module ApplicationTests
       end
     end
 
-    test "routing to an nonexistent controller when action_dispatch.show_exceptions and consider_all_requests_local are set shows diagnostics" do
+    test "routing to a nonexistent controller when action_dispatch.show_exceptions and consider_all_requests_local are set shows diagnostics" do
       app_file "config/routes.rb", <<-RUBY
         Rails.application.routes.draw do
           resources :articles
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index 0a5a524692..470a5326c6 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -42,6 +42,7 @@ module ApplicationTests
         "ActionDispatch::Cookies",
         "ActionDispatch::Session::CookieStore",
         "ActionDispatch::Flash",
+        "ActionDispatch::ContentSecurityPolicy::Middleware",
         "Rack::Head",
         "Rack::ConditionalGet",
         "Rack::ETag"
diff --git a/railties/test/application/rake/dbs_test.rb b/railties/test/application/rake/dbs_test.rb
index 391676aa31..2082e9fa9f 100644
--- a/railties/test/application/rake/dbs_test.rb
+++ b/railties/test/application/rake/dbs_test.rb
@@ -26,12 +26,12 @@ module ApplicationTests
         FileUtils.rm_rf("#{app_path}/config/database.yml")
       end
 
-      def db_create_and_drop(expected_database)
+      def db_create_and_drop(expected_database, environment_loaded: true)
         Dir.chdir(app_path) do
           output = rails("db:create")
           assert_match(/Created database/, output)
           assert File.exist?(expected_database)
-          assert_equal expected_database, ActiveRecord::Base.connection_config[:database]
+          assert_equal expected_database, ActiveRecord::Base.connection_config[:database] if environment_loaded
           output = rails("db:drop")
           assert_match(/Dropped database/, output)
           assert !File.exist?(expected_database)
@@ -49,6 +49,22 @@ module ApplicationTests
         db_create_and_drop database_url_db_name
       end
 
+      test "db:create and db:drop respect environment setting" do
+        app_file "config/database.yml", <<-YAML
+          development:
+            database: <%= Rails.application.config.database %>
+            adapter: sqlite3
+        YAML
+
+        app_file "config/environments/development.rb", <<-RUBY
+          Rails.application.configure do
+            config.database = "db/development.sqlite3"
+          end
+        RUBY
+
+        db_create_and_drop "db/development.sqlite3", environment_loaded: false
+      end
+
       def with_database_existing
         Dir.chdir(app_path) do
           set_database_url
@@ -82,13 +98,25 @@ module ApplicationTests
         end
       end
 
-      test "db:drop failure because database does not exist" do
-        Dir.chdir(app_path) do
-          output = rails("db:drop:_unsafe", "--trace")
-          assert_match(/does not exist/, output)
+      test "db:create works when schema cache exists and database does not exist" do
+        use_postgresql
+
+        begin
+          rails %w(db:create db:migrate db:schema:cache:dump)
+
+          rails "db:drop"
+          rails "db:create"
+          assert_equal 0, $?.exitstatus
+        ensure
+          rails "db:drop" rescue nil
         end
       end
 
+      test "db:drop failure because database does not exist" do
+        output = rails("db:drop:_unsafe", "--trace")
+        assert_match(/does not exist/, output)
+      end
+
       test "db:drop failure because bad permissions" do
         with_database_existing do
           with_bad_permissions do
@@ -100,13 +128,11 @@ module ApplicationTests
       end
 
       def db_migrate_and_status(expected_database)
-        Dir.chdir(app_path) do
-          rails "generate", "model", "book", "title:string"
-          rails "db:migrate"
-          output = rails("db:migrate:status")
-          assert_match(%r{database:\s+\S*#{Regexp.escape(expected_database)}}, output)
-          assert_match(/up\s+\d{14}\s+Create books/, output)
-        end
+        rails "generate", "model", "book", "title:string"
+        rails "db:migrate"
+        output = rails("db:migrate:status")
+        assert_match(%r{database:\s+\S*#{Regexp.escape(expected_database)}}, output)
+        assert_match(/up\s+\d{14}\s+Create books/, output)
       end
 
       test "db:migrate and db:migrate:status without database_url" do
@@ -161,12 +187,11 @@ module ApplicationTests
 
       test "db:fixtures:load with namespaced fixture" do
         require "#{app_path}/config/environment"
-        Dir.chdir(app_path) do
-          rails "generate", "model", "admin::book", "title:string"
-          rails "db:migrate", "db:fixtures:load"
-          require "#{app_path}/app/models/admin/book"
-          assert_equal 2, Admin::Book.count
-        end
+
+        rails "generate", "model", "admin::book", "title:string"
+        rails "db:migrate", "db:fixtures:load"
+        require "#{app_path}/app/models/admin/book"
+        assert_equal 2, Admin::Book.count
       end
 
       def db_structure_dump_and_load(expected_database)
@@ -194,6 +219,14 @@ module ApplicationTests
         db_structure_dump_and_load database_url_db_name
       end
 
+      test "db:structure:dump and db:structure:load set ar_internal_metadata" do
+        require "#{app_path}/config/environment"
+        db_structure_dump_and_load ActiveRecord::Base.configurations[Rails.env]["database"]
+
+        assert_equal "test", rails("runner", "-e", "test", "puts ActiveRecord::InternalMetadata[:environment]").strip
+        assert_equal "development", rails("runner", "puts ActiveRecord::InternalMetadata[:environment]").strip
+      end
+
       test "db:structure:dump does not dump schema information when no migrations are used" do
         # create table without migrations
         rails "runner", "ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }"
@@ -205,56 +238,52 @@ module ApplicationTests
       end
 
       test "db:schema:load and db:structure:load do not purge the existing database" do
-        Dir.chdir(app_path) do
-          rails "runner", "ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }"
+        rails "runner", "ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }"
 
-          app_file "db/schema.rb", <<-RUBY
-            ActiveRecord::Schema.define(version: 20140423102712) do
-              create_table(:comments) {}
-            end
-          RUBY
+        app_file "db/schema.rb", <<-RUBY
+          ActiveRecord::Schema.define(version: 20140423102712) do
+            create_table(:comments) {}
+          end
+        RUBY
 
-          list_tables = lambda { rails("runner", "p ActiveRecord::Base.connection.tables").strip }
+        list_tables = lambda { rails("runner", "p ActiveRecord::Base.connection.tables").strip }
 
-          assert_equal '["posts"]', list_tables[]
-          rails "db:schema:load"
-          assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata"]', list_tables[]
+        assert_equal '["posts"]', list_tables[]
+        rails "db:schema:load"
+        assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata"]', list_tables[]
 
-          app_file "db/structure.sql", <<-SQL
-            CREATE TABLE "users" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255));
-          SQL
+        app_file "db/structure.sql", <<-SQL
+          CREATE TABLE "users" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255));
+        SQL
 
-          rails "db:structure:load"
-          assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata", "users"]', list_tables[]
-        end
+        rails "db:structure:load"
+        assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata", "users"]', list_tables[]
       end
 
       test "db:schema:load with inflections" do
-        Dir.chdir(app_path) do
-          app_file "config/initializers/inflection.rb", <<-RUBY
-            ActiveSupport::Inflector.inflections do |inflect|
-              inflect.irregular 'goose', 'geese'
-            end
-          RUBY
-          app_file "config/initializers/primary_key_table_name.rb", <<-RUBY
-            ActiveRecord::Base.primary_key_prefix_type = :table_name
-          RUBY
-          app_file "db/schema.rb", <<-RUBY
-            ActiveRecord::Schema.define(version: 20140423102712) do
-              create_table("goose".pluralize) do |t|
-                t.string :name
-              end
+        app_file "config/initializers/inflection.rb", <<-RUBY
+          ActiveSupport::Inflector.inflections do |inflect|
+            inflect.irregular 'goose', 'geese'
+          end
+        RUBY
+        app_file "config/initializers/primary_key_table_name.rb", <<-RUBY
+          ActiveRecord::Base.primary_key_prefix_type = :table_name
+        RUBY
+        app_file "db/schema.rb", <<-RUBY
+          ActiveRecord::Schema.define(version: 20140423102712) do
+            create_table("goose".pluralize) do |t|
+              t.string :name
             end
-          RUBY
+          end
+        RUBY
 
-          rails "db:schema:load"
+        rails "db:schema:load"
 
-          tables = rails("runner", "p ActiveRecord::Base.connection.tables").strip
-          assert_match(/"geese"/, tables)
+        tables = rails("runner", "p ActiveRecord::Base.connection.tables").strip
+        assert_match(/"geese"/, tables)
 
-          columns = rails("runner", "p ActiveRecord::Base.connection.columns('geese').map(&:name)").strip
-          assert_equal columns, '["gooseid", "name"]'
-        end
+        columns = rails("runner", "p ActiveRecord::Base.connection.columns('geese').map(&:name)").strip
+        assert_equal columns, '["gooseid", "name"]'
       end
 
       test "db:schema:load fails if schema.rb doesn't exist yet" do
@@ -300,15 +329,52 @@ module ApplicationTests
             puts ActiveRecord::Base.connection_config[:database]
           RUBY
 
-          Dir.chdir(app_path) do
-            database_path = rails("db:setup")
-            assert_equal "development.sqlite3", File.basename(database_path.strip)
-          end
+          database_path = rails("db:setup")
+          assert_equal "development.sqlite3", File.basename(database_path.strip)
         ensure
           ENV["RAILS_ENV"] = @old_rails_env
           ENV["RACK_ENV"] = @old_rack_env
         end
       end
+
+      test "db:setup sets ar_internal_metadata" do
+        app_file "db/schema.rb", ""
+        rails "db:setup"
+
+        test_environment = lambda { rails("runner", "-e", "test", "puts ActiveRecord::InternalMetadata[:environment]").strip }
+        development_environment = lambda { rails("runner", "puts ActiveRecord::InternalMetadata[:environment]").strip }
+
+        assert_equal "test", test_environment.call
+        assert_equal "development", development_environment.call
+
+        app_file "db/structure.sql", ""
+        app_file "config/initializers/enable_sql_schema_format.rb", <<-RUBY
+          Rails.application.config.active_record.schema_format = :sql
+        RUBY
+
+        rails "db:setup"
+
+        assert_equal "test", test_environment.call
+        assert_equal "development", development_environment.call
+      end
+
+      test "db:test:prepare sets test ar_internal_metadata" do
+        app_file "db/schema.rb", ""
+        rails "db:test:prepare"
+
+        test_environment = lambda { rails("runner", "-e", "test", "puts ActiveRecord::InternalMetadata[:environment]").strip }
+
+        assert_equal "test", test_environment.call
+
+        app_file "db/structure.sql", ""
+        app_file "config/initializers/enable_sql_schema_format.rb", <<-RUBY
+          Rails.application.config.active_record.schema_format = :sql
+        RUBY
+
+        rails "db:test:prepare"
+
+        assert_equal "test", test_environment.call
+      end
     end
   end
 end
diff --git a/railties/test/application/rake/migrations_test.rb b/railties/test/application/rake/migrations_test.rb
index b0d51eb22e..788f9160d6 100644
--- a/railties/test/application/rake/migrations_test.rb
+++ b/railties/test/application/rake/migrations_test.rb
@@ -15,69 +15,146 @@ module ApplicationTests
       end
 
       test "running migrations with given scope" do
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "model", "user", "username:string", "password:string"
 
-          app_file "db/migrate/01_a_migration.bukkits.rb", <<-MIGRATION
-            class AMigration < ActiveRecord::Migration::Current
-            end
-          MIGRATION
+        app_file "db/migrate/01_a_migration.bukkits.rb", <<-MIGRATION
+          class AMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = rails("db:migrate", "SCOPE=bukkits")
-          assert_no_match(/create_table\(:users\)/, output)
-          assert_no_match(/CreateUsers/, output)
-          assert_no_match(/add_column\(:users, :email, :string\)/, output)
+        output = rails("db:migrate", "SCOPE=bukkits")
+        assert_no_match(/create_table\(:users\)/, output)
+        assert_no_match(/CreateUsers/, output)
+        assert_no_match(/add_column\(:users, :email, :string\)/, output)
 
-          assert_match(/AMigration: migrated/, output)
+        assert_match(/AMigration: migrated/, output)
 
-          output = rails("db:migrate", "SCOPE=bukkits", "VERSION=0")
-          assert_no_match(/drop_table\(:users\)/, output)
-          assert_no_match(/CreateUsers/, output)
-          assert_no_match(/remove_column\(:users, :email\)/, output)
+        output = rails("db:migrate", "SCOPE=bukkits", "VERSION=0")
+        assert_no_match(/drop_table\(:users\)/, output)
+        assert_no_match(/CreateUsers/, output)
+        assert_no_match(/remove_column\(:users, :email\)/, output)
 
-          assert_match(/AMigration: reverted/, output)
-        end
+        assert_match(/AMigration: reverted/, output)
+      end
+
+      test "migrate with specified VERSION in different formats" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/03_three_migration.rb", <<-MIGRATION
+          class ThreeMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+        assert_match(/up\s+003\s+Three migration/, output)
+
+        rails "db:migrate", "VERSION=01_one_migration.rb"
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/down\s+002\s+Two migration/, output)
+        assert_match(/down\s+003\s+Three migration/, output)
+
+        rails "db:migrate", "VERSION=3"
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+        assert_match(/up\s+003\s+Three migration/, output)
+
+        rails "db:migrate", "VERSION=001"
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/down\s+002\s+Two migration/, output)
+        assert_match(/down\s+003\s+Three migration/, output)
       end
 
       test "migration with empty version" do
-        Dir.chdir(app_path) do
-          output = rails("db:migrate", "VERSION=", allow_failure: true)
-          assert_match(/Empty VERSION provided/, output)
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = rails("db:migrate:redo", "VERSION=", allow_failure: true)
-          assert_match(/Empty VERSION provided/, output)
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = rails("db:migrate:up", "VERSION=", allow_failure: true)
-          assert_match(/VERSION is required/, output)
+        rails("db:migrate", "VERSION=")
 
-          output = rails("db:migrate:up", allow_failure: true)
-          assert_match(/VERSION is required/, output)
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
 
-          output = rails("db:migrate:down", "VERSION=", allow_failure: true)
-          assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+        output = rails("db:migrate:redo", "VERSION=", allow_failure: true)
+        assert_match(/Empty VERSION provided/, output)
 
-          output = rails("db:migrate:down", allow_failure: true)
-          assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
-        end
+        output = rails("db:migrate:up", "VERSION=", allow_failure: true)
+        assert_match(/VERSION is required/, output)
+
+        output = rails("db:migrate:up", allow_failure: true)
+        assert_match(/VERSION is required/, output)
+
+        output = rails("db:migrate:down", "VERSION=", allow_failure: true)
+        assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+
+        output = rails("db:migrate:down", allow_failure: true)
+        assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
       end
 
-      test "model and migration generator with change syntax" do
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
-          rails "generate", "migration", "add_email_to_users", "email:string"
+      test "migration with 0 version" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = rails("db:migrate")
-          assert_match(/create_table\(:users\)/, output)
-          assert_match(/CreateUsers: migrated/, output)
-          assert_match(/add_column\(:users, :email, :string\)/, output)
-          assert_match(/AddEmailToUsers: migrated/, output)
-
-          output = rails("db:rollback", "STEP=2")
-          assert_match(/drop_table\(:users\)/, output)
-          assert_match(/CreateUsers: reverted/, output)
-          assert_match(/remove_column\(:users, :email, :string\)/, output)
-          assert_match(/AddEmailToUsers: reverted/, output)
-        end
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+
+        rails "db:migrate", "VERSION=0"
+
+        output = rails("db:migrate:status")
+        assert_match(/down\s+001\s+One migration/, output)
+        assert_match(/down\s+002\s+Two migration/, output)
+      end
+
+      test "model and migration generator with change syntax" do
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+
+        output = rails("db:migrate")
+        assert_match(/create_table\(:users\)/, output)
+        assert_match(/CreateUsers: migrated/, output)
+        assert_match(/add_column\(:users, :email, :string\)/, output)
+        assert_match(/AddEmailToUsers: migrated/, output)
+
+        output = rails("db:rollback", "STEP=2")
+        assert_match(/drop_table\(:users\)/, output)
+        assert_match(/CreateUsers: reverted/, output)
+        assert_match(/remove_column\(:users, :email, :string\)/, output)
+        assert_match(/AddEmailToUsers: reverted/, output)
       end
 
       test "migration status when schema migrations table is not present" do
@@ -86,93 +163,85 @@ module ApplicationTests
       end
 
       test "migration status" do
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
-          rails "generate", "migration", "add_email_to_users", "email:string"
-          rails "db:migrate"
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = rails("db:migrate:status")
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
 
-          rails "db:rollback", "STEP=1"
-          output = rails("db:migrate:status")
+        rails "db:rollback", "STEP=1"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/down\s+\d{14}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/down\s+\d{14}\s+Add email to users/, output)
       end
 
       test "migration status without timestamps" do
         add_to_config("config.active_record.timestamped_migrations = false")
 
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
-          rails "generate", "migration", "add_email_to_users", "email:string"
-          rails "db:migrate"
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = rails("db:migrate:status")
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/up\s+\d{3,}\s+Add email to users/, output)
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/up\s+\d{3,}\s+Add email to users/, output)
 
-          rails "db:rollback", "STEP=1"
-          output = rails("db:migrate:status")
+        rails "db:rollback", "STEP=1"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/down\s+\d{3,}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/down\s+\d{3,}\s+Add email to users/, output)
       end
 
       test "migration status after rollback and redo" do
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
-          rails "generate", "migration", "add_email_to_users", "email:string"
-          rails "db:migrate"
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = rails("db:migrate:status")
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
 
-          rails "db:rollback", "STEP=2"
-          output = rails("db:migrate:status")
+        rails "db:rollback", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/down\s+\d{14}\s+Create users/, output)
-          assert_match(/down\s+\d{14}\s+Add email to users/, output)
+        assert_match(/down\s+\d{14}\s+Create users/, output)
+        assert_match(/down\s+\d{14}\s+Add email to users/, output)
 
-          rails "db:migrate:redo"
-          output = rails("db:migrate:status")
+        rails "db:migrate:redo"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
       end
 
       test "migration status after rollback and forward" do
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
-          rails "generate", "migration", "add_email_to_users", "email:string"
-          rails "db:migrate"
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = rails("db:migrate:status")
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
 
-          rails "db:rollback", "STEP=2"
-          output = rails("db:migrate:status")
+        rails "db:rollback", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/down\s+\d{14}\s+Create users/, output)
-          assert_match(/down\s+\d{14}\s+Add email to users/, output)
+        assert_match(/down\s+\d{14}\s+Create users/, output)
+        assert_match(/down\s+\d{14}\s+Add email to users/, output)
 
-          rails "db:forward", "STEP=2"
-          output = rails("db:migrate:status")
+        rails "db:forward", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
       end
 
       test "raise error on any move when current migration does not exist" do
@@ -206,53 +275,117 @@ module ApplicationTests
         end
       end
 
+      test "raise error on any move when target migration does not exist" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+
+        output = rails("db:migrate", "VERSION=3", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/ActiveRecord::UnknownMigrationVersionError:/, output)
+        assert_match(/No migration with version number 3/, output)
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+      end
+
+      test "raise error on any move when VERSION has invalid format" do
+        output = rails("db:migrate", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=0.1.11", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1.1.11", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION='0 '", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1.", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1_", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1_name", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate:redo", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate:up", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate:down", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+      end
+
       test "migration status after rollback and redo without timestamps" do
         add_to_config("config.active_record.timestamped_migrations = false")
 
-        Dir.chdir(app_path) do
-          rails "generate", "model", "user", "username:string", "password:string"
-          rails "generate", "migration", "add_email_to_users", "email:string"
-          rails "db:migrate"
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = rails("db:migrate:status")
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/up\s+\d{3,}\s+Add email to users/, output)
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/up\s+\d{3,}\s+Add email to users/, output)
 
-          rails "db:rollback", "STEP=2"
-          output = rails("db:migrate:status")
+        rails "db:rollback", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/down\s+\d{3,}\s+Create users/, output)
-          assert_match(/down\s+\d{3,}\s+Add email to users/, output)
+        assert_match(/down\s+\d{3,}\s+Create users/, output)
+        assert_match(/down\s+\d{3,}\s+Add email to users/, output)
 
-          rails "db:migrate:redo"
-          output = rails("db:migrate:status")
+        rails "db:migrate:redo"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/up\s+\d{3,}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/up\s+\d{3,}\s+Add email to users/, output)
       end
 
       test "running migrations with not timestamp head migration files" do
-        Dir.chdir(app_path) do
+        app_file "db/migrate/1_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          app_file "db/migrate/1_one_migration.rb", <<-MIGRATION
-            class OneMigration < ActiveRecord::Migration::Current
-            end
-          MIGRATION
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
-            class TwoMigration < ActiveRecord::Migration::Current
-            end
-          MIGRATION
+        rails "db:migrate"
 
-          rails "db:migrate"
+        output = rails("db:migrate:status")
 
-          output = rails("db:migrate:status")
-
-          assert_match(/up\s+001\s+One migration/, output)
-          assert_match(/up\s+002\s+Two migration/, output)
-        end
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
       end
 
       test "schema generation when dump_schema_after_migration is set" do
diff --git a/railties/test/application/rake_test.rb b/railties/test/application/rake_test.rb
index f9b14f98cb..bf89098645 100644
--- a/railties/test/application/rake_test.rb
+++ b/railties/test/application/rake_test.rb
@@ -40,7 +40,7 @@ module ApplicationTests
       with_rails_env "test" do
         rails "generate", "model", "product", "name:string"
         rails "db:create", "db:migrate"
-        output = Dir.chdir(app_path) { rails("db:test:prepare", "test") }
+        output = rails("db:test:prepare", "test")
 
         refute_match(/ActiveRecord::ProtectedEnvironmentError/, output)
       end
@@ -101,6 +101,7 @@ module ApplicationTests
       add_to_config <<-RUBY
         rake_tasks do
           task do_nothing: :environment do
+            puts 'There is nothing'
           end
         end
       RUBY
@@ -113,10 +114,8 @@ module ApplicationTests
         raise 'should not be pre-required for rake even eager_load=true'
       RUBY
 
-      Dir.chdir(app_path) do
-        assert system("bin/rails do_nothing RAILS_ENV=production"),
-               "should not be pre-required for rake even eager_load=true"
-      end
+      output = rails("do_nothing", "RAILS_ENV=production")
+      assert_match "There is nothing", output
     end
 
     def test_code_statistics_sanity
@@ -133,13 +132,8 @@ module ApplicationTests
 
       output = rails("routes")
       assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-                           cart GET  /cart(.:format)                                                                   cart#show
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                               active_storage/disk#update
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                    active_storage/direct_uploads#create
+                         Prefix Verb URI Pattern     Controller#Action
+                           cart GET  /cart(.:format) cart#show
       MESSAGE
     end
 
@@ -172,20 +166,16 @@ module ApplicationTests
         end
       RUBY
 
-      output = rails("routes", "-g", "show", allow_failure: true)
+      output = rails("routes", "-g", "show")
       assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-                           cart GET  /cart(.:format)                                                                   cart#show
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
+                         Prefix Verb URI Pattern     Controller#Action
+                           cart GET  /cart(.:format) cart#show
       MESSAGE
 
       output = rails("routes", "-g", "POST")
       assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                    Controller#Action
-                                POST /cart(.:format)                                cart#create
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format) active_storage/direct_uploads#create
+                         Prefix Verb URI Pattern     Controller#Action
+                                POST /cart(.:format) cart#create
       MESSAGE
 
       output = rails("routes", "-g", "basketballs")
@@ -242,12 +232,11 @@ module ApplicationTests
       RUBY
 
       assert_equal <<-MESSAGE.strip_heredoc, rails("routes")
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                               active_storage/disk#update
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                    active_storage/direct_uploads#create
+        You don't have any routes defined!
+
+        Please add some routes in config/routes.rb.
+
+        For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html.
       MESSAGE
     end
 
@@ -261,13 +250,8 @@ module ApplicationTests
       output = Dir.chdir(app_path) { `bin/rake --rakefile Rakefile routes` }
 
       assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-                           cart GET  /cart(.:format)                                                                   cart#show
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                               active_storage/disk#update
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                    active_storage/direct_uploads#create
+                         Prefix Verb URI Pattern     Controller#Action
+                           cart GET  /cart(.:format) cart#show
       MESSAGE
     end
 
@@ -309,9 +293,8 @@ module ApplicationTests
 
     def test_scaffold_tests_pass_by_default
       rails "generate", "scaffold", "user", "username:string", "password:string"
-      output = Dir.chdir(app_path) do
-        `RAILS_ENV=test bin/rails db:migrate test`
-      end
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
 
       assert_match(/7 runs, 9 assertions, 0 failures, 0 errors/, output)
       assert_no_match(/Errors running/, output)
@@ -328,9 +311,8 @@ module ApplicationTests
       RUBY
 
       rails "generate", "scaffold", "user", "username:string", "password:string"
-      output = Dir.chdir(app_path) do
-        `RAILS_ENV=test bin/rails db:migrate test`
-      end
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
 
       assert_match(/5 runs, 7 assertions, 0 failures, 0 errors/, output)
       assert_no_match(/Errors running/, output)
@@ -340,9 +322,8 @@ module ApplicationTests
       rails "generate", "model", "Product"
       rails "generate", "model", "Cart"
       rails "generate", "scaffold", "LineItems", "product:references", "cart:belongs_to"
-      output = Dir.chdir(app_path) do
-        `RAILS_ENV=test bin/rails db:migrate test`
-      end
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
 
       assert_match(/7 runs, 9 assertions, 0 failures, 0 errors/, output)
       assert_no_match(/Errors running/, output)
@@ -352,9 +333,7 @@ module ApplicationTests
       add_to_config "config.active_record.schema_format = :sql"
       rails "generate", "scaffold", "user", "username:string"
       rails "db:migrate"
-      output = with_rails_env("test") do
-        rails "db:test:prepare", "--trace"
-      end
+      output = rails("db:test:prepare", "--trace")
       assert_match(/Execute db:test:load_structure/, output)
     end
 
@@ -387,14 +366,12 @@ module ApplicationTests
     end
 
     def test_copy_templates
-      Dir.chdir(app_path) do
-        rails "app:templates:copy"
-        %w(controller mailer scaffold).each do |dir|
-          assert File.exist?(File.join(app_path, "lib", "templates", "erb", dir))
-        end
-        %w(controller helper scaffold_controller assets).each do |dir|
-          assert File.exist?(File.join(app_path, "lib", "templates", "rails", dir))
-        end
+      rails "app:templates:copy"
+      %w(controller mailer scaffold).each do |dir|
+        assert File.exist?(File.join(app_path, "lib", "templates", "erb", dir))
+      end
+      %w(controller helper scaffold_controller assets).each do |dir|
+        assert File.exist?(File.join(app_path, "lib", "templates", "rails", dir))
       end
     end
 
diff --git a/railties/test/application/runner_test.rb b/railties/test/application/runner_test.rb
index 64c46c4b45..aa5d495c97 100644
--- a/railties/test/application/runner_test.rb
+++ b/railties/test/application/runner_test.rb
@@ -128,5 +128,17 @@ module ApplicationTests
         assert_match "production", rails("runner", "puts Rails.env")
       end
     end
+
+    def test_can_call_same_name_class_as_defined_in_thor
+      app_file "app/models/task.rb", <<-MODEL
+      class Task
+        def self.count
+          42
+        end
+      end
+      MODEL
+
+      assert_match "42", rails("runner", "puts Task.count")
+    end
   end
 end
diff --git a/railties/test/application/server_test.rb b/railties/test/application/server_test.rb
index 6db9a3b9e8..2238f4f63a 100644
--- a/railties/test/application/server_test.rb
+++ b/railties/test/application/server_test.rb
@@ -42,7 +42,7 @@ module ApplicationTests
         pid = Process.spawn("#{app_path}/bin/rails server -P tmp/dummy.pid", in: slave, out: slave, err: slave)
         assert_output("Listening", master)
 
-        Dir.chdir(app_path) { system("bin/rails restart") }
+        rails("restart")
 
         assert_output("Restarting", master)
         assert_output("Inherited", master)
diff --git a/railties/test/application/test_runner_test.rb b/railties/test/application/test_runner_test.rb
index e92a0466dd..a01325fdb8 100644
--- a/railties/test/application/test_runner_test.rb
+++ b/railties/test/application/test_runner_test.rb
@@ -569,6 +569,40 @@ module ApplicationTests
       assert_match "AccountTest#test_truth", output, "passing TEST= should run selected test"
     end
 
+    def test_running_with_ruby_gets_test_env_by_default
+      # Subshells inherit `ENV`, so we need to ensure `RAILS_ENV` is set to
+      # nil before we run the tests in the test app.
+      re, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], nil
+
+      file = create_test_for_env("test")
+      results = Dir.chdir(app_path) {
+        `ruby -Ilib:test #{file}`.each_line.map { |line| JSON.parse line }
+      }
+      assert_equal 1, results.length
+      failures = results.first["failures"]
+      flunk(failures.first) unless failures.empty?
+
+    ensure
+      ENV["RAILS_ENV"] = re
+    end
+
+    def test_running_with_ruby_can_set_env_via_cmdline
+      # Subshells inherit `ENV`, so we need to ensure `RAILS_ENV` is set to
+      # nil before we run the tests in the test app.
+      re, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], nil
+
+      file = create_test_for_env("development")
+      results = Dir.chdir(app_path) {
+        `RAILS_ENV=development ruby -Ilib:test #{file}`.each_line.map { |line| JSON.parse line }
+      }
+      assert_equal 1, results.length
+      failures = results.first["failures"]
+      flunk(failures.first) unless failures.empty?
+
+    ensure
+      ENV["RAILS_ENV"] = re
+    end
+
     def test_rake_passes_multiple_TESTOPTS_to_minitest
       create_test_file :models, "account"
       output = Dir.chdir(app_path) { `bin/rake test TESTOPTS='-v --seed=1234'` }
@@ -727,6 +761,45 @@ module ApplicationTests
         app_file "db/schema.rb", ""
       end
 
+      def create_test_for_env(env)
+        app_file "test/models/environment_test.rb", <<-RUBY
+          require 'test_helper'
+          class JSONReporter < Minitest::AbstractReporter
+            def record(result)
+              puts JSON.dump(klass: result.class.name,
+                             name: result.name,
+                             failures: result.failures,
+                             assertions: result.assertions,
+                             time: result.time)
+            end
+          end
+
+          def Minitest.plugin_json_reporter_init(opts)
+            Minitest.reporter.reporters.clear
+            Minitest.reporter.reporters << JSONReporter.new
+          end
+
+          Minitest.extensions << "rails"
+          Minitest.extensions << "json_reporter"
+
+          # Minitest uses RubyGems to find plugins, and since RubyGems
+          # doesn't know about the Rails installation we're pointing at,
+          # Minitest won't require the Rails minitest plugin when we run
+          # these integration tests.  So we have to manually require the
+          # Minitest plugin here.
+          require 'minitest/rails_plugin'
+
+          class EnvironmentTest < ActiveSupport::TestCase
+            def test_environment
+              test_db = ActiveRecord::Base.configurations[#{env.dump}]["database"]
+              db_file = ActiveRecord::Base.connection_config[:database]
+              assert_match(test_db, db_file)
+              assert_equal #{env.dump}, ENV["RAILS_ENV"]
+            end
+          end
+        RUBY
+      end
+
       def create_test_file(path = :unit, name = "test", pass: true)
         app_file "test/#{path}/#{name}_test.rb", <<-RUBY
           require 'test_helper'
diff --git a/railties/test/commands/console_test.rb b/railties/test/commands/console_test.rb
index 7eb26c355c..45ab8d87ff 100644
--- a/railties/test/commands/console_test.rb
+++ b/railties/test/commands/console_test.rb
@@ -172,21 +172,8 @@ class Rails::ConsoleTest < ActiveSupport::TestCase
     end
 
     def parse_arguments(args)
-      Rails::Command::ConsoleCommand.class_eval do
-        alias_method :old_perform, :perform
-        define_method(:perform) do
-          extract_environment_option_from_argument
-
-          options
-        end
-      end
-
-      Rails::Command.invoke(:console, args)
-    ensure
-      Rails::Command::ConsoleCommand.class_eval do
-        undef_method :perform
-        alias_method :perform, :old_perform
-        undef_method :old_perform
-      end
+      command = Rails::Command::ConsoleCommand.new([], args)
+      command.send(:extract_environment_option_from_argument)
+      command.options
     end
 end
diff --git a/railties/test/commands/credentials_test.rb b/railties/test/commands/credentials_test.rb
index fe52c306d2..f1bb1ef08a 100644
--- a/railties/test/commands/credentials_test.rb
+++ b/railties/test/commands/credentials_test.rb
@@ -12,6 +12,24 @@ class Rails::Command::CredentialsCommandTest < ActiveSupport::TestCase
 
   teardown { teardown_app }
 
+  test "edit without editor gives hint" do
+    run_edit_command(editor: "").tap do |output|
+      assert_match "No $EDITOR to open file in", output
+      assert_match "bin/rails credentials:edit", output
+    end
+  end
+
+  test "edit credentials" do
+    # Run twice to ensure credentials can be reread after first edit pass.
+    2.times do
+      assert_match(/access_key_id: 123/, run_edit_command)
+    end
+  end
+
+  test "show credentials" do
+    assert_match(/access_key_id: 123/, run_show_command)
+  end
+
   test "edit command does not add master key to gitignore when already exist" do
     run_edit_command
 
@@ -21,10 +39,22 @@ class Rails::Command::CredentialsCommandTest < ActiveSupport::TestCase
     end
   end
 
+  test "edit command does not overwrite by default if credentials already exists" do
+    run_edit_command(editor: "eval echo api_key: abc >")
+    assert_match(/api_key: abc/, run_show_command)
+
+    run_edit_command
+    assert_match(/api_key: abc/, run_show_command)
+  end
+
   private
     def run_edit_command(editor: "cat")
       switch_env("EDITOR", editor) do
         rails "credentials:edit"
       end
     end
+
+    def run_show_command
+      rails "credentials:show"
+    end
 end
diff --git a/railties/test/commands/encrypted_test.rb b/railties/test/commands/encrypted_test.rb
new file mode 100644
index 0000000000..0461493f2a
--- /dev/null
+++ b/railties/test/commands/encrypted_test.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "env_helpers"
+require "rails/command"
+require "rails/commands/encrypted/encrypted_command"
+
+class Rails::Command::EncryptedCommandTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation, EnvHelpers
+
+  setup :build_app
+  teardown :teardown_app
+
+  test "edit without editor gives hint" do
+    run_edit_command("config/tokens.yml.enc", editor: "").tap do |output|
+      assert_match "No $EDITOR to open file in", output
+      assert_match "bin/rails encrypted:edit", output
+    end
+  end
+
+  test "edit encrypted file" do
+    # Run twice to ensure file can be reread after first edit pass.
+    2.times do
+      assert_match(/access_key_id: 123/, run_edit_command("config/tokens.yml.enc"))
+    end
+  end
+
+  test "edit command does not add master key to gitignore when already exist" do
+    run_edit_command("config/tokens.yml.enc")
+
+    Dir.chdir(app_path) do
+      assert_match "/config/master.key", File.read(".gitignore")
+    end
+  end
+
+  test "edit encrypts file with custom key" do
+    run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
+
+    Dir.chdir(app_path) do
+      assert File.exist?("config/tokens.yml.enc")
+      assert File.exist?("config/tokens.key")
+
+      assert_match "/config/tokens.key", File.read(".gitignore")
+    end
+
+    assert_match(/access_key_id: 123/, run_edit_command("config/tokens.yml.enc", key: "config/tokens.key"))
+  end
+
+  test "show encrypted file with custom key" do
+    run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
+
+    assert_match(/access_key_id: 123/, run_show_command("config/tokens.yml.enc", key: "config/tokens.key"))
+  end
+
+  test "won't corrupt encrypted file when passed wrong key" do
+    run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
+
+    assert_match "passed the wrong key",
+      run_edit_command("config/tokens.yml.enc", allow_failure: true)
+
+    assert_match(/access_key_id: 123/, run_show_command("config/tokens.yml.enc", key: "config/tokens.key"))
+  end
+
+  private
+    def run_edit_command(file, key: nil, editor: "cat", **options)
+      switch_env("EDITOR", editor) do
+        rails "encrypted:edit", prepare_args(file, key), **options
+      end
+    end
+
+    def run_show_command(file, key: nil)
+      rails "encrypted:show", prepare_args(file, key)
+    end
+
+    def prepare_args(file, key)
+      args = [ file ]
+      args.push("--key", key) if key
+      args
+    end
+end
diff --git a/railties/test/commands/secrets_test.rb b/railties/test/commands/secrets_test.rb
index 66a81826e3..6b9f284a0c 100644
--- a/railties/test/commands/secrets_test.rb
+++ b/railties/test/commands/secrets_test.rb
@@ -8,21 +8,38 @@ require "rails/commands/secrets/secrets_command"
 class Rails::Command::SecretsCommandTest < ActiveSupport::TestCase
   include ActiveSupport::Testing::Isolation, EnvHelpers
 
-  def setup
-    build_app
+  setup :build_app
+  teardown :teardown_app
+
+  test "edit without editor gives hint" do
+    assert_match "No $EDITOR to open decrypted secrets in", run_edit_command(editor: "")
   end
 
-  def teardown
-    teardown_app
+  test "encrypted secrets are deprecated when using credentials" do
+    assert_match "Encrypted secrets is deprecated", run_setup_command
+    assert_equal 1, $?.exitstatus
+    assert_not File.exist?("config/secrets.yml.enc")
   end
 
-  test "edit without editor gives hint" do
-    assert_match "No $EDITOR to open decrypted secrets in", run_edit_command(editor: "")
+  test "encrypted secrets are deprecated when running edit without setup" do
+    assert_match "Encrypted secrets is deprecated", run_setup_command
+    assert_equal 1, $?.exitstatus
+    assert_not File.exist?("config/secrets.yml.enc")
+  end
+
+  test "encrypted secrets are deprecated for 5.1 config/secrets.yml apps" do
+    Dir.chdir(app_path) do
+      FileUtils.rm("config/credentials.yml.enc")
+      FileUtils.touch("config/secrets.yml")
+
+      assert_match "Encrypted secrets is deprecated", run_setup_command
+      assert_equal 1, $?.exitstatus
+      assert_not File.exist?("config/secrets.yml.enc")
+    end
   end
 
   test "edit secrets" do
-    # Runs setup before first edit.
-    assert_match(/Adding config\/secrets\.yml\.key to store the encryption key/, run_edit_command)
+    prevent_deprecation
 
     # Run twice to ensure encrypted secrets can be reread after first edit pass.
     2.times do
@@ -31,22 +48,30 @@ class Rails::Command::SecretsCommandTest < ActiveSupport::TestCase
   end
 
   test "show secrets" do
-    run_setup_command
+    prevent_deprecation
+
     assert_match(/external_api_key: 1466aac22e6a869134be3d09b9e89232fc2c2289/, run_show_command)
   end
 
   private
+    def prevent_deprecation
+      Dir.chdir(app_path) do
+        File.write("config/secrets.yml.key", "f731758c639da2604dfb6bf3d1025de8")
+        File.write("config/secrets.yml.enc", "sEB0mHxDbeP1/KdnMk00wyzPFACl9K6t0cZWn5/Mfx/YbTHvnI07vrneqHg9kaH3wOS7L6pIQteu1P077OtE4BSx/ZRc/sgQPHyWu/tXsrfHqnPNpayOF/XZqizE91JacSFItNMWpuPsp9ynbzz+7cGhoB1S4aPNIU6u0doMrzdngDbijsaAFJmsHIQh6t/QHoJx--8aMoE0PvUWmw1Iqz--ldFqnM/K0g9k17M8PKoN/Q==")
+      end
+    end
+
     def run_edit_command(editor: "cat")
       switch_env("EDITOR", editor) do
-        rails "secrets:edit"
+        rails "secrets:edit", allow_failure: true
       end
     end
 
     def run_show_command
-      rails "secrets:show"
+      rails "secrets:show", allow_failure: true
     end
 
     def run_setup_command
-      rails "secrets:setup"
+      rails "secrets:setup", allow_failure: true
     end
 end
diff --git a/railties/test/commands/server_test.rb b/railties/test/commands/server_test.rb
index 556c2289e7..33715ea75f 100644
--- a/railties/test/commands/server_test.rb
+++ b/railties/test/commands/server_test.rb
@@ -22,6 +22,18 @@ class Rails::ServerTest < ActiveSupport::TestCase
     assert_nil options[:server]
   end
 
+  def test_daemon_with_option
+    args = ["-d"]
+    options = parse_arguments(args)
+    assert_equal true, options[:daemonize]
+  end
+
+  def test_daemon_without_option
+    args = []
+    options = parse_arguments(args)
+    assert_equal false, options[:daemonize]
+  end
+
   def test_server_option_without_environment
     args = ["thin"]
     with_rack_env nil do
@@ -81,6 +93,18 @@ class Rails::ServerTest < ActiveSupport::TestCase
     assert_equal false, options[:caching]
   end
 
+  def test_early_hints_with_option
+    args = ["--early-hints"]
+    options = parse_arguments(args)
+    assert_equal true, options[:early_hints]
+  end
+
+  def test_early_hints_is_nil_by_default
+    args = []
+    options = parse_arguments(args)
+    assert_nil options[:early_hints]
+  end
+
   def test_log_stdout
     with_rack_env nil do
       with_rails_env nil do
diff --git a/railties/test/engine/test_test.rb b/railties/test/engine/test_test.rb
new file mode 100644
index 0000000000..18af85a0aa
--- /dev/null
+++ b/railties/test/engine/test_test.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class Rails::Engine::TestTest < ActiveSupport::TestCase
+  setup do
+    @destination_root = Dir.mktmpdir("bukkits")
+    Dir.chdir(@destination_root) { `bundle exec rails plugin new bukkits --mountable` }
+  end
+
+  teardown do
+    FileUtils.rm_rf(@destination_root)
+  end
+
+  test "automatically synchronize test schema" do
+    Dir.chdir(plugin_path) do
+      # In order to confirm that migration files are loaded, generate multiple migration files.
+      `bin/rails generate model user name:string;
+       bin/rails generate model todo name:string;
+       RAILS_ENV=development bin/rails db:migrate`
+
+      output = `bin/rails test test/models/bukkits/user_test.rb`
+      assert_includes(output, "0 runs, 0 assertions, 0 failures, 0 errors, 0 skips")
+    end
+  end
+
+  private
+    def plugin_path
+      "#{@destination_root}/bukkits"
+    end
+end
diff --git a/railties/test/fixtures/about_yml_plugins/bad_about_yml/about.yml b/railties/test/fixtures/about_yml_plugins/bad_about_yml/about.yml
deleted file mode 100644
index fe80872a16..0000000000
--- a/railties/test/fixtures/about_yml_plugins/bad_about_yml/about.yml
+++ /dev/null
@@ -1 +0,0 @@
-# an empty YAML file - any content in here seems to get parsed as a string
\ No newline at end of file
diff --git a/railties/test/fixtures/about_yml_plugins/bad_about_yml/init.rb b/railties/test/fixtures/about_yml_plugins/bad_about_yml/init.rb
deleted file mode 100644
index 1a82a2bdd4..0000000000
--- a/railties/test/fixtures/about_yml_plugins/bad_about_yml/init.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-# intentionally empty
diff --git a/railties/test/fixtures/about_yml_plugins/plugin_without_about_yml/init.rb b/railties/test/fixtures/about_yml_plugins/plugin_without_about_yml/init.rb
deleted file mode 100644
index 1a82a2bdd4..0000000000
--- a/railties/test/fixtures/about_yml_plugins/plugin_without_about_yml/init.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-# intentionally empty
diff --git a/railties/test/generators/actions_test.rb b/railties/test/generators/actions_test.rb
index 3ecfb4edd9..f421207025 100644
--- a/railties/test/generators/actions_test.rb
+++ b/railties/test/generators/actions_test.rb
@@ -308,6 +308,14 @@ class ActionsTest < Rails::Generators::TestCase
     end
   end
 
+  test "rake command with capture option should run rake command with capture" do
+    assert_called_with(generator, :run, ["rake log:clear RAILS_ENV=development", verbose: false, capture: true]) do
+      with_rails_env nil do
+        action :rake, "log:clear", capture: true
+      end
+    end
+  end
+
   test "rails command should run rails_command with default env" do
     assert_called_with(generator, :run, ["rails log:clear RAILS_ENV=development", verbose: false]) do
       with_rails_env nil do
@@ -346,6 +354,14 @@ class ActionsTest < Rails::Generators::TestCase
     end
   end
 
+  test "rails command with capture option should run rails_command with capture" do
+    assert_called_with(generator, :run, ["rails log:clear RAILS_ENV=development", verbose: false, capture: true]) do
+      with_rails_env nil do
+        action :rails_command, "log:clear", capture: true
+      end
+    end
+  end
+
   def test_capify_should_run_the_capify_command
     content = capture(:stderr) do
       assert_called_with(generator, :run, ["capify .", verbose: false]) do
diff --git a/railties/test/generators/api_app_generator_test.rb b/railties/test/generators/api_app_generator_test.rb
index 7791d472d8..4815cf6362 100644
--- a/railties/test/generators/api_app_generator_test.rb
+++ b/railties/test/generators/api_app_generator_test.rb
@@ -72,6 +72,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
 
     assert_no_file "config/initializers/cookies_serializer.rb"
     assert_no_file "config/initializers/assets.rb"
+    assert_no_file "config/initializers/content_security_policy.rb"
   end
 
   def test_app_update_does_not_generate_unnecessary_bin_files
@@ -149,6 +150,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
          bin/yarn
          config/initializers/assets.rb
          config/initializers/cookies_serializer.rb
+         config/initializers/content_security_policy.rb
          lib/assets
          test/helpers
          tmp/cache/assets
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index 904e2a5c84..96803db838 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -56,6 +56,7 @@ DEFAULT_APP_FILES = %w(
   config/initializers/assets.rb
   config/initializers/backtrace_silencers.rb
   config/initializers/cookies_serializer.rb
+  config/initializers/content_security_policy.rb
   config/initializers/filter_parameter_logging.rb
   config/initializers/inflections.rb
   config/initializers/mime_types.rb
@@ -75,6 +76,7 @@ DEFAULT_APP_FILES = %w(
   log
   package.json
   public
+  storage
   test/application_system_test_case.rb
   test/test_helper.rb
   test/fixtures
@@ -89,6 +91,7 @@ DEFAULT_APP_FILES = %w(
   tmp
   tmp/cache
   tmp/cache/assets
+  tmp/storage
 )
 
 class AppGeneratorTest < Rails::Generators::TestCase
@@ -296,6 +299,80 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_active_storage_mini_magick_gem
+    run_generator
+    assert_file "Gemfile", /^# gem 'mini_magick'/
+  end
+
+  def test_active_storage_install
+    command_check = -> command, _ do
+      @binstub_called ||= 0
+      case command
+      when "active_storage:install"
+        @binstub_called += 1
+        assert_equal 1, @binstub_called, "active_storage:install expected to be called once, but was called #{@binstub_called} times"
+      end
+    end
+
+    generator.stub :rails_command, command_check do
+      quietly { generator.invoke_all }
+    end
+  end
+
+  def test_app_update_does_not_generate_active_storage_contents_when_skip_active_storage_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-active-storage"]
+
+    FileUtils.cd(app_root) do
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_file "#{app_root}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{app_root}/config/storage.yml"
+
+    assert_file "#{app_root}/Gemfile" do |content|
+      assert_no_match(/gem 'mini_magick'/, content)
+    end
+  end
+
+  def test_app_update_does_not_generate_active_storage_contents_when_skip_active_record_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-active-record"]
+
+    FileUtils.cd(app_root) do
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_file "#{app_root}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{app_root}/config/storage.yml"
+
+    assert_file "#{app_root}/Gemfile" do |content|
+      assert_no_match(/gem 'mini_magick'/, content)
+    end
+  end
+
   def test_application_names_are_not_singularized
     run_generator [File.join(destination_root, "hats")]
     assert_file "hats/config/environment.rb", /Rails\.application\.initialize!/
@@ -327,7 +404,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
     if defined?(JRUBY_VERSION)
       assert_gem "activerecord-jdbcmysql-adapter"
     else
-      assert_gem "mysql2", "'>= 0.3.18', '< 0.5'"
+      assert_gem "mysql2", "'~> 0.4.4'"
     end
   end
 
@@ -381,7 +458,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
   def test_generator_defaults_to_puma_version
     run_generator [destination_root]
-    assert_gem "puma", "'~> 3.7'"
+    assert_gem "puma", "'~> 3.11'"
   end
 
   def test_generator_if_skip_puma_is_given
@@ -412,6 +489,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_file "Gemfile" do |content|
       assert_no_match(/capybara/, content)
       assert_no_match(/selenium-webdriver/, content)
+      assert_no_match(/chromedriver-helper/, content)
     end
 
     assert_no_directory("test")
@@ -422,6 +500,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_file "Gemfile" do |content|
       assert_no_match(/capybara/, content)
       assert_no_match(/selenium-webdriver/, content)
+      assert_no_match(/chromedriver-helper/, content)
     end
 
     assert_directory("test")
@@ -560,6 +639,11 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_no_match(/run  git init/, output)
   end
 
+  def test_quiet_option
+    output = run_generator [File.join(destination_root, "myapp"), "--quiet"]
+    assert_empty output
+  end
+
   def test_application_name_with_spaces
     path = File.join(destination_root, "foo bar")
 
@@ -659,6 +743,41 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_webpack_option
+    command_check = -> command, *_ do
+      @called ||= 0
+      if command == "webpacker:install"
+        @called += 1
+        assert_equal 1, @called, "webpacker:install expected to be called once, but was called #{@called} times."
+      end
+    end
+
+    generator([destination_root], webpack: "webpack").stub(:rails_command, command_check) do
+      quietly { generator.invoke_all }
+    end
+
+    assert_gem "webpacker"
+  end
+
+  def test_webpack_option_with_js_framework
+    command_check = -> command, *_ do
+      case command
+      when "webpacker:install"
+        @webpacker ||= 0
+        @webpacker += 1
+        assert_equal 1, @webpacker, "webpacker:install expected to be called once, but was called #{@webpacker} times."
+      when "webpacker:install:react"
+        @react ||= 0
+        @react += 1
+        assert_equal 1, @react, "webpacker:install:react expected to be called once, but was called #{@react} times."
+      end
+    end
+
+    generator([destination_root], webpack: "react").stub(:rails_command, command_check) do
+      quietly { generator.invoke_all }
+    end
+  end
+
   def test_generator_if_skip_turbolinks_is_given
     run_generator [destination_root, "--skip-turbolinks"]
 
@@ -735,9 +854,9 @@ class AppGeneratorTest < Rails::Generators::TestCase
       template
     end
 
-    sequence = ["git init", "install", "exec spring binstub --all", "echo ran after_bundle"]
+    sequence = ["git init", "install", "exec spring binstub --all", "active_storage:install", "echo ran after_bundle"]
     @sequence_step ||= 0
-    ensure_bundler_first = -> command do
+    ensure_bundler_first = -> command, options = nil do
       assert_equal sequence[@sequence_step], command, "commands should be called in sequence #{sequence}"
       @sequence_step += 1
     end
@@ -745,12 +864,22 @@ class AppGeneratorTest < Rails::Generators::TestCase
     generator([destination_root], template: path).stub(:open, check_open, template) do
       generator.stub(:bundle_command, ensure_bundler_first) do
         generator.stub(:run, ensure_bundler_first) do
-          quietly { generator.invoke_all }
+          generator.stub(:rails_command, ensure_bundler_first) do
+            quietly { generator.invoke_all }
+          end
         end
       end
     end
 
-    assert_equal 4, @sequence_step
+    assert_equal 5, @sequence_step
+  end
+
+  def test_gitignore
+    run_generator
+
+    assert_file ".gitignore" do |content|
+      assert_match(/config\/master\.key/, content)
+    end
   end
 
   def test_system_tests_directory_generated
diff --git a/railties/test/generators/argv_scrubber_test.rb b/railties/test/generators/argv_scrubber_test.rb
index 3f4c985a33..9ef61dc978 100644
--- a/railties/test/generators/argv_scrubber_test.rb
+++ b/railties/test/generators/argv_scrubber_test.rb
@@ -82,9 +82,8 @@ module Rails
         file.puts "--hello --world"
         file.flush
 
-        message = nil
         scrubber = Class.new(ARGVScrubber) {
-          define_method(:puts) { |msg| message = msg }
+          define_method(:puts) { |msg| }
         }.new ["new", "--rc=#{file.path}"]
         args = scrubber.prepare!
         assert_equal ["--hello", "--world"], args
diff --git a/railties/test/generators/encrypted_secrets_generator_test.rb b/railties/test/generators/encrypted_secrets_generator_test.rb
deleted file mode 100644
index eacb5166c0..0000000000
--- a/railties/test/generators/encrypted_secrets_generator_test.rb
+++ /dev/null
@@ -1,44 +0,0 @@
-# frozen_string_literal: true
-
-require "generators/generators_test_helper"
-require "rails/generators/rails/encrypted_secrets/encrypted_secrets_generator"
-
-class EncryptedSecretsGeneratorTest < Rails::Generators::TestCase
-  include GeneratorsTestHelper
-
-  def setup
-    super
-    cd destination_root
-  end
-
-  def test_generates_key_file_and_encrypted_secrets_file
-    run_generator
-
-    assert_file "config/secrets.yml.key", /\w+/
-
-    assert File.exist?("config/secrets.yml.enc")
-    assert_no_match(/# production:\n#   external_api_key: \w+/, IO.binread("config/secrets.yml.enc"))
-    assert_match(/# production:\n#   external_api_key: \w+/, Rails::Secrets.read)
-  end
-
-  def test_appends_to_gitignore
-    FileUtils.touch(".gitignore")
-
-    run_generator
-
-    assert_file ".gitignore", /config\/secrets.yml.key/, /(?!config\/secrets.yml.enc)/
-  end
-
-  def test_warns_when_ignore_is_missing
-    assert_match(/Add this to your ignore file/i, run_generator)
-  end
-
-  def test_doesnt_generate_a_new_key_file_if_already_opted_in_to_encrypted_secrets
-    FileUtils.mkdir("config")
-    File.open("config/secrets.yml.enc", "w") { |f| f.puts "already secrety" }
-
-    run_generator
-
-    assert_no_file "config/secrets.yml.key"
-  end
-end
diff --git a/railties/test/generators/generators_test_helper.rb b/railties/test/generators/generators_test_helper.rb
index cb5d8da7b1..ad2a55f496 100644
--- a/railties/test/generators/generators_test_helper.rb
+++ b/railties/test/generators/generators_test_helper.rb
@@ -43,9 +43,9 @@ module GeneratorsTestHelper
   end
 
   def copy_routes
-    routes = File.expand_path("../../lib/rails/generators/rails/app/templates/config/routes.rb", __dir__)
+    routes = File.expand_path("../../lib/rails/generators/rails/app/templates/config/routes.rb.tt", __dir__)
     destination = File.join(destination_root, "config")
     FileUtils.mkdir_p(destination)
-    FileUtils.cp routes, destination
+    FileUtils.cp routes, File.join(destination, "routes.rb")
   end
 end
diff --git a/railties/test/generators/named_base_test.rb b/railties/test/generators/named_base_test.rb
index 67f05926e3..4e61b660d7 100644
--- a/railties/test/generators/named_base_test.rb
+++ b/railties/test/generators/named_base_test.rb
@@ -33,6 +33,17 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "foos",       :plural_name
     assert_name g, "admin.foo",  :i18n_scope
     assert_name g, "admin_foos", :table_name
+    assert_name g, "admin/foos", :controller_name
+    assert_name g, %w(admin),     :controller_class_path
+    assert_name g, "Admin::Foos", :controller_class_name
+    assert_name g, "admin/foos",  :controller_file_path
+    assert_name g, "foos",        :controller_file_name
+    assert_name g, "admin.foos",  :controller_i18n_scope
+    assert_name g, "admin_foo",  :singular_route_name
+    assert_name g, "admin_foos", :plural_route_name
+    assert_name g, "@admin_foo", :redirect_resource_name
+    assert_name g, "admin_foo",  :model_resource_name
+    assert_name g, "admin_foos", :index_helper
   end
 
   def test_named_generator_attributes_as_ruby
@@ -47,6 +58,17 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "foos",       :plural_name
     assert_name g, "admin.foo",  :i18n_scope
     assert_name g, "admin_foos", :table_name
+    assert_name g, "Admin::Foos", :controller_name
+    assert_name g, %w(admin),     :controller_class_path
+    assert_name g, "Admin::Foos", :controller_class_name
+    assert_name g, "admin/foos",  :controller_file_path
+    assert_name g, "foos",        :controller_file_name
+    assert_name g, "admin.foos",  :controller_i18n_scope
+    assert_name g, "admin_foo",  :singular_route_name
+    assert_name g, "admin_foos", :plural_route_name
+    assert_name g, "@admin_foo", :redirect_resource_name
+    assert_name g, "admin_foo",  :model_resource_name
+    assert_name g, "admin_foos", :index_helper
   end
 
   def test_named_generator_attributes_without_pluralized
@@ -59,7 +81,7 @@ class NamedBaseTest < Rails::Generators::TestCase
     ActiveRecord::Base.pluralize_table_names = original_pluralize_table_names
   end
 
-  def test_scaffold_plural_names
+  def test_namespaced_scaffold_plural_names
     g = generator ["admin/foo"]
     assert_name g, "admin/foos",  :controller_name
     assert_name g, %w(admin),     :controller_class_path
@@ -69,7 +91,7 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "admin.foos",  :controller_i18n_scope
   end
 
-  def test_scaffold_plural_names_as_ruby
+  def test_namespaced_scaffold_plural_names_as_ruby
     g = generator ["Admin::Foo"]
     assert_name g, "Admin::Foos", :controller_name
     assert_name g, %w(admin),     :controller_class_path
@@ -131,6 +153,19 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "admin/foos",  :controller_file_path
     assert_name g, "foos",        :controller_file_name
     assert_name g, "admin.foos",  :controller_i18n_scope
+    assert_name g, "admin_user",  :singular_route_name
+    assert_name g, "admin_users", :plural_route_name
+    assert_name g, "[:admin, @user]", :redirect_resource_name
+    assert_name g, "[:admin, user]",  :model_resource_name
+    assert_name g, "admin_users", :index_helper
+  end
+
+  def test_scaffold_plural_names
+    g = generator ["User"]
+    assert_name g, "@user", :redirect_resource_name
+    assert_name g, "user",  :model_resource_name
+    assert_name g, "user",  :singular_route_name
+    assert_name g, "users", :plural_route_name
   end
 
   private
diff --git a/railties/test/generators/plugin_generator_test.rb b/railties/test/generators/plugin_generator_test.rb
index 38130ceb68..fc7584c175 100644
--- a/railties/test/generators/plugin_generator_test.rb
+++ b/railties/test/generators/plugin_generator_test.rb
@@ -240,8 +240,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     run_generator [destination_root, "--full", "--skip_active_record"]
     FileUtils.cd destination_root
     quietly { system "bundle install" }
-    # FIXME: Active Storage will provoke a test error without ActiveRecord (fix by allowing to skip active storage)
-    assert_match(/1 runs, 0 assertions, 0 failures, 1 errors/, `bundle exec rake test 2>&1`)
+    assert_match(/1 runs, 1 assertions, 0 failures, 0 errors/, `bundle exec rake test 2>&1`)
   end
 
   def test_ensure_that_migration_tasks_work_with_mountable_option
@@ -475,6 +474,8 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_no_file "test/dummy/Gemfile"
     assert_no_file "test/dummy/public/robots.txt"
     assert_no_file "test/dummy/README.md"
+    assert_no_file "test/dummy/config/master.key"
+    assert_no_file "test/dummy/config/credentials.yml.enc"
     assert_no_directory "test/dummy/lib/tasks"
     assert_no_directory "test/dummy/test"
     assert_no_directory "test/dummy/vendor"
@@ -514,10 +515,11 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     gemfile_path = "#{Rails.root}/Gemfile"
     Object.const_set("APP_PATH", Rails.root)
     FileUtils.touch gemfile_path
+    File.write(gemfile_path, "#foo")
 
     run_generator
 
-    assert_file gemfile_path, /gem 'bukkits', path: 'tmp\/bukkits'/
+    assert_file gemfile_path, /^gem 'bukkits', path: 'tmp\/bukkits'/
   ensure
     Object.send(:remove_const, "APP_PATH")
     FileUtils.rm gemfile_path
@@ -719,6 +721,38 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     Object.send(:remove_const, "ENGINE_ROOT")
   end
 
+  def test_after_bundle_callback
+    path = "http://example.org/rails_template"
+    template = %{ after_bundle { run "echo ran after_bundle" } }.dup
+    template.instance_eval "def read; self; end" # Make the string respond to read
+
+    check_open = -> *args do
+      assert_equal [ path, "Accept" => "application/x-thor-template" ], args
+      template
+    end
+
+    sequence = ["echo ran after_bundle"]
+    @sequence_step ||= 0
+    ensure_bundler_first = -> command do
+      assert_equal sequence[@sequence_step], command, "commands should be called in sequence #{sequence}"
+      @sequence_step += 1
+    end
+
+    content = nil
+    generator([destination_root], template: path).stub(:open, check_open, template) do
+      generator.stub(:bundle_command, ensure_bundler_first) do
+        generator.stub(:run, ensure_bundler_first) do
+          silence_stream($stdout) do
+            content = capture(:stderr) { generator.invoke_all }
+          end
+        end
+      end
+    end
+
+    assert_equal 1, @sequence_step
+    assert_match(/DEPRECATION WARNING: `after_bundle` is deprecated/, content)
+  end
+
   private
 
     def action(*args, &block)
diff --git a/railties/test/generators/scaffold_controller_generator_test.rb b/railties/test/generators/scaffold_controller_generator_test.rb
index 384524aba9..fd5aa817b4 100644
--- a/railties/test/generators/scaffold_controller_generator_test.rb
+++ b/railties/test/generators/scaffold_controller_generator_test.rb
@@ -174,6 +174,29 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
       assert_instance_method :index, content do |m|
         assert_match("@users = User.all", m)
       end
+
+      assert_instance_method :create, content do |m|
+        assert_match("redirect_to [:admin, @user]", m)
+      end
+
+      assert_instance_method :update, content do |m|
+        assert_match("redirect_to [:admin, @user]", m)
+      end
+    end
+
+    assert_file "app/views/admin/users/index.html.erb" do |content|
+      assert_match("'Show', [:admin, user]", content)
+      assert_match("'Edit', edit_admin_user_path(user)", content)
+      assert_match("'Destroy', [:admin, user]", content)
+      assert_match("'New User', new_admin_user_path", content)
+    end
+
+    assert_file "app/views/admin/users/new.html.erb" do |content|
+      assert_match("'Back', admin_users_path", content)
+    end
+
+    assert_file "app/views/admin/users/_form.html.erb" do |content|
+      assert_match("model: [:admin, user]", content)
     end
   end
 
@@ -184,6 +207,7 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
 
     Dir.chdir(engine_path) do
       quietly { `bin/rails g controller dashboard foo` }
+      quietly { `bin/rails db:migrate RAILS_ENV=test` }
       assert_match(/2 runs, 2 assertions, 0 failures, 0 errors/, `bin/rails test 2>&1`)
     end
   end
@@ -195,6 +219,7 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
 
     Dir.chdir(engine_path) do
       quietly { `bin/rails g controller dashboard foo` }
+      quietly { `bin/rails db:migrate RAILS_ENV=test` }
       assert_match(/2 runs, 2 assertions, 0 failures, 0 errors/, `bin/rails test 2>&1`)
     end
   end
diff --git a/railties/test/generators/scaffold_generator_test.rb b/railties/test/generators/scaffold_generator_test.rb
index 03322c1c59..29426cd99f 100644
--- a/railties/test/generators/scaffold_generator_test.rb
+++ b/railties/test/generators/scaffold_generator_test.rb
@@ -282,7 +282,14 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
                 /class Admin::RolesTest < ApplicationSystemTestCase/
 
     # Views
-    %w(index edit new show _form).each do |view|
+    assert_file "app/views/admin/roles/index.html.erb" do |content|
+      assert_match("'Show', admin_role", content)
+      assert_match("'Edit', edit_admin_role_path(admin_role)", content)
+      assert_match("'Destroy', admin_role", content)
+      assert_match("'New Admin Role', new_admin_role_path", content)
+    end
+
+    %w(edit new show _form).each do |view|
       assert_file "app/views/admin/roles/#{view}.html.erb"
     end
     assert_no_file "app/views/layouts/admin/roles.html.erb"
@@ -464,8 +471,8 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/views/accounts/_form.html.erb" do |content|
-      assert_match(/^\W{4}<%= form\.text_field :name, id: :account_name %>/, content)
-      assert_match(/^\W{4}<%= form\.text_field :currency_id, id: :account_currency_id %>/, content)
+      assert_match(/^\W{4}<%= form\.text_field :name %>/, content)
+      assert_match(/^\W{4}<%= form\.text_field :currency_id %>/, content)
     end
   end
 
@@ -488,8 +495,8 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/views/users/_form.html.erb" do |content|
-      assert_match(/<%= form\.password_field :password, id: :user_password %>/, content)
-      assert_match(/<%= form\.password_field :password_confirmation, id: :user_password_confirmation %>/, content)
+      assert_match(/<%= form\.password_field :password %>/, content)
+      assert_match(/<%= form\.password_field :password_confirmation %>/, content)
     end
 
     assert_file "app/views/users/index.html.erb" do |content|
diff --git a/railties/test/generators/shared_generator_tests.rb b/railties/test/generators/shared_generator_tests.rb
index 654d16de65..6b746f3fed 100644
--- a/railties/test/generators/shared_generator_tests.rb
+++ b/railties/test/generators/shared_generator_tests.rb
@@ -129,13 +129,26 @@ module SharedGeneratorTests
   end
 
   def test_default_frameworks_are_required_when_others_are_removed
-    run_generator [destination_root, "--skip-active-record", "--skip-action-mailer", "--skip-action-cable", "--skip-sprockets"]
-    assert_file "#{application_path}/config/application.rb", /require\s+["']rails["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']active_model\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']active_job\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']action_controller\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']action_view\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']active_storage\/engine["']/
+    run_generator [
+      destination_root,
+      "--skip-active-record",
+      "--skip-active-storage",
+      "--skip-action-mailer",
+      "--skip-action-cable",
+      "--skip-sprockets"
+    ]
+
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']rails["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']active_model\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']active_job\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']active_record\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']active_storage\/engine["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']action_controller\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']action_mailer\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']action_view\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']action_cable\/engine["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']sprockets\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']rails\/test_unit\/railtie["']/
   end
 
   def test_generator_without_skips
@@ -189,6 +202,96 @@ module SharedGeneratorTests
     end
   end
 
+  def test_generator_for_active_storage
+    run_generator
+
+    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+      assert_match(/^\/\/= require activestorage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/development.rb" do |content|
+      assert_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/production.rb" do |content|
+      assert_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/test.rb" do |content|
+      assert_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/storage.yml"
+    assert_directory "#{application_path}/storage"
+    assert_directory "#{application_path}/tmp/storage"
+
+    assert_file ".gitignore" do |content|
+      assert_match(/\/storage\//, content)
+    end
+  end
+
+  def test_generator_if_skip_active_storage_is_given
+    run_generator [destination_root, "--skip-active-storage"]
+
+    assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']active_storage\/engine["']/
+
+    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+      assert_no_match(/^\/\/= require activestorage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{application_path}/config/storage.yml"
+    assert_no_directory "#{application_path}/db/migrate"
+    assert_no_directory "#{application_path}/storage"
+    assert_no_directory "#{application_path}/tmp/storage"
+
+    assert_file ".gitignore" do |content|
+      assert_no_match(/\/storage\//, content)
+    end
+  end
+
+  def test_generator_does_not_generate_active_storage_contents_if_skip_active_record_is_given
+    run_generator [destination_root, "--skip-active-record"]
+
+    assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']active_storage\/engine["']/
+
+    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+      assert_no_match(/^\/\/= require activestorage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{application_path}/config/storage.yml"
+    assert_no_directory "#{application_path}/db/migrate"
+    assert_no_directory "#{application_path}/storage"
+    assert_no_directory "#{application_path}/tmp/storage"
+
+    assert_file ".gitignore" do |content|
+      assert_no_match(/\/storage\//, content)
+    end
+  end
+
   def test_generator_if_skip_action_mailer_is_given
     run_generator [destination_root, "--skip-action-mailer"]
     assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']action_mailer\/railtie["']/
diff --git a/railties/test/generators_test.rb b/railties/test/generators_test.rb
index 28e7617d7f..1735804664 100644
--- a/railties/test/generators_test.rb
+++ b/railties/test/generators_test.rb
@@ -36,6 +36,19 @@ class GeneratorsTest < Rails::Generators::TestCase
     assert_match "Maybe you meant 'migration'", output
   end
 
+  def test_generator_suggestions_except_en_locale
+    orig_available_locales = I18n.available_locales
+    orig_default_locale = I18n.default_locale
+    I18n.available_locales = :ja
+    I18n.default_locale = :ja
+    name = :tas
+    output = capture(:stdout) { Rails::Generators.invoke name }
+    assert_match "Maybe you meant 'task', 'job' or", output
+  ensure
+    I18n.available_locales = orig_available_locales
+    I18n.default_locale = orig_default_locale
+  end
+
   def test_generator_multiple_suggestions
     name = :tas
     output = capture(:stdout) { Rails::Generators.invoke name }
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index b7f214cb73..96c6f21395 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -153,6 +153,7 @@ module TestHelpers
 
     def teardown_app
       ENV["RAILS_ENV"] = @prev_rails_env if @prev_rails_env
+      FileUtils.rm_rf(tmp_path)
     end
 
     # Make a very basic app, without creating the whole directory structure.
@@ -235,7 +236,7 @@ module TestHelpers
 
     # Invoke a bin/rails command inside the app
     #
-    # allow_failures:: true to return normally if the command exits with
+    # allow_failure:: true to return normally if the command exits with
     #   a non-zero status. By default, this method will raise.
     # stderr:: true to pass STDERR output straight to the "real" STDERR.
     #   By default, the STDERR and STDOUT of the process will be
@@ -357,10 +358,12 @@ module TestHelpers
     end
 
     def app_file(path, contents, mode = "w")
-      FileUtils.mkdir_p File.dirname("#{app_path}/#{path}")
-      File.open("#{app_path}/#{path}", mode) do |f|
+      file_name = "#{app_path}/#{path}"
+      FileUtils.mkdir_p File.dirname(file_name)
+      File.open(file_name, mode) do |f|
         f.puts contents
       end
+      file_name
     end
 
     def remove_file(path)
@@ -380,6 +383,21 @@ module TestHelpers
 
       $:.reject! { |path| path =~ %r'/(#{to_remove.join('|')})/' }
     end
+
+    def use_postgresql
+      File.open("#{app_path}/config/database.yml", "w") do |f|
+        f.puts <<-YAML
+        default: &default
+          adapter: postgresql
+          pool: 5
+          database: railties_test
+        development:
+          <<: *default
+        test:
+          <<: *default
+        YAML
+      end
+    end
   end
 end
 
diff --git a/railties/test/rails_info_test.rb b/railties/test/rails_info_test.rb
index 227a739b71..43b60b9144 100644
--- a/railties/test/rails_info_test.rb
+++ b/railties/test/rails_info_test.rb
@@ -2,20 +2,7 @@
 
 require "abstract_unit"
 
-unless defined?(Rails) && defined?(Rails::Info)
-  module Rails
-    class Info; end
-  end
-end
-
-require "active_support/core_ext/kernel/reporting"
-
 class InfoTest < ActiveSupport::TestCase
-  def setup
-    Rails.send :remove_const, :Info
-    silence_warnings { load "rails/info.rb" }
-  end
-
   def test_property_with_block_swallows_exceptions_and_ignores_property
     assert_nothing_raised do
       Rails::Info.module_eval do
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index e6964b4b18..fc710feb63 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -32,6 +32,11 @@ module RailtiesTest
       require "#{app_path}/config/environment"
     end
 
+    def migrations
+      migration_root = File.expand_path(ActiveRecord::Migrator.migrations_paths.first, app_path)
+      ActiveRecord::Migrator.migrations(migration_root)
+    end
+
     test "serving sprocket's assets" do
       @plugin.write "app/assets/javascripts/engine.js.erb", "<%= :alert %>();"
       add_to_env_config "development", "config.assets.digest = false"
@@ -82,31 +87,32 @@ module RailtiesTest
         end
       RUBY
 
-      add_to_config "ActiveRecord::Base.timestamped_migrations = false"
-
       boot_rails
 
       Dir.chdir(app_path) do
+        # Install Active Storage migration file first so as not to affect test.
+        `bundle exec rake active_storage:install`
         output = `bundle exec rake bukkits:install:migrations`
 
-        assert File.exist?("#{app_path}/db/migrate/2_create_users.bukkits.rb")
-        assert File.exist?("#{app_path}/db/migrate/3_add_last_name_to_users.bukkits.rb")
-        assert_match(/Copied migration 2_create_users\.bukkits\.rb from bukkits/, output)
-        assert_match(/Copied migration 3_add_last_name_to_users\.bukkits\.rb from bukkits/, output)
-        assert_match(/NOTE: Migration 3_create_sessions\.rb from bukkits has been skipped/, output)
-        assert_equal 3, Dir["#{app_path}/db/migrate/*.rb"].length
+        ["CreateUsers", "AddLastNameToUsers", "CreateSessions"].each do |migration_name|
+          assert migrations.detect { |migration| migration.name == migration_name }
+        end
+        assert_match(/Copied migration \d+_create_users\.bukkits\.rb from bukkits/, output)
+        assert_match(/Copied migration \d+_add_last_name_to_users\.bukkits\.rb from bukkits/, output)
+        assert_match(/NOTE: Migration \d+_create_sessions\.rb from bukkits has been skipped/, output)
 
-        output = `bundle exec rake railties:install:migrations`.split("\n")
+        migrations_count = Dir["#{app_path}/db/migrate/*.rb"].length
 
-        assert_no_match(/2_create_users/, output.join("\n"))
+        assert_equal migrations.length, migrations_count
 
-        bukkits_migration_order = output.index(output.detect { |o| /NOTE: Migration 3_create_sessions\.rb from bukkits has been skipped/ =~ o })
-        assert_not_nil bukkits_migration_order, "Expected migration to be skipped"
-
-        migrations_count = Dir["#{app_path}/db/migrate/*.rb"].length
-        `bundle exec rake railties:install:migrations`
+        output = `bundle exec rake railties:install:migrations`.split("\n")
 
         assert_equal migrations_count, Dir["#{app_path}/db/migrate/*.rb"].length
+
+        assert_no_match(/\d+_create_users/, output.join("\n"))
+
+        bukkits_migration_order = output.index(output.detect { |o| /NOTE: Migration \d+_create_sessions\.rb from bukkits has been skipped/ =~ o })
+        assert_not_nil bukkits_migration_order, "Expected migration to be skipped"
       end
     end
 
@@ -171,10 +177,12 @@ module RailtiesTest
       boot_rails
 
       Dir.chdir(app_path) do
+        # Install Active Storage migration file first so as not to affect test.
+        `bundle exec rake active_storage:install`
         output = `bundle exec rake railties:install:migrations`.split("\n")
 
-        assert_match(/Copied migration \d+_create_users\.core_engine\.rb from core_engine/, output.second)
-        assert_match(/Copied migration \d+_create_keys\.api_engine\.rb from api_engine/, output.last)
+        assert_match(/Copied migration \d+_create_users\.core_engine\.rb from core_engine/, output.first)
+        assert_match(/Copied migration \d+_create_keys\.api_engine\.rb from api_engine/, output.second)
       end
     end
 
@@ -203,9 +211,12 @@ module RailtiesTest
 
       Dir.chdir(@plugin.path) do
         output = `bundle exec rake app:bukkits:install:migrations`
-        assert File.exist?("#{app_path}/db/migrate/0_add_first_name_to_users.bukkits.rb")
-        assert_match(/Copied migration 0_add_first_name_to_users\.bukkits\.rb from bukkits/, output)
-        assert_equal 1, Dir["#{app_path}/db/migrate/*.rb"].length
+
+        migration_with_engine_path = migrations.detect { |migration| migration.name == "AddFirstNameToUsers" }
+        assert migration_with_engine_path
+        assert_match(/\/db\/migrate\/\d+_add_first_name_to_users\.bukkits\.rb/, migration_with_engine_path.filename)
+        assert_match(/Copied migration \d+_add_first_name_to_users\.bukkits\.rb from bukkits/, output)
+        assert_equal migrations.length, Dir["#{app_path}/db/migrate/*.rb"].length
       end
     end
 
diff --git a/railties/test/secrets_test.rb b/railties/test/secrets_test.rb
index 888fee173a..06877bc76a 100644
--- a/railties/test/secrets_test.rb
+++ b/railties/test/secrets_test.rb
@@ -1,20 +1,13 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
-require "rails/generators"
-require "rails/generators/rails/encrypted_secrets/encrypted_secrets_generator"
 require "rails/secrets"
 
 class Rails::SecretsTest < ActiveSupport::TestCase
   include ActiveSupport::Testing::Isolation
 
-  def setup
-    build_app
-  end
-
-  def teardown
-    teardown_app
-  end
+  setup :build_app
+  teardown :teardown_app
 
   test "setting read to false skips parsing" do
     run_secrets_generator do
@@ -172,9 +165,8 @@ class Rails::SecretsTest < ActiveSupport::TestCase
   private
     def run_secrets_generator
       Dir.chdir(app_path) do
-        capture(:stdout) do
-          Rails::Generators::EncryptedSecretsGenerator.start
-        end
+        File.write("config/secrets.yml.key", "f731758c639da2604dfb6bf3d1025de8")
+        File.write("config/secrets.yml.enc", "sEB0mHxDbeP1/KdnMk00wyzPFACl9K6t0cZWn5/Mfx/YbTHvnI07vrneqHg9kaH3wOS7L6pIQteu1P077OtE4BSx/ZRc/sgQPHyWu/tXsrfHqnPNpayOF/XZqizE91JacSFItNMWpuPsp9ynbzz+7cGhoB1S4aPNIU6u0doMrzdngDbijsaAFJmsHIQh6t/QHoJx--8aMoE0PvUWmw1Iqz--ldFqnM/K0g9k17M8PKoN/Q==")
 
         add_to_config <<-RUBY
           config.read_encrypted_secrets = true
diff --git a/tasks/release.rb b/tasks/release.rb
index aa8ba44c1a..6ff06f3c4a 100644
--- a/tasks/release.rb
+++ b/tasks/release.rb
@@ -6,7 +6,6 @@ FRAMEWORK_NAMES = Hash.new { |h, k| k.split(/(?<=active|action)/).map(&:capitali
 root    = File.expand_path("..", __dir__)
 version = File.read("#{root}/RAILS_VERSION").strip
 tag     = "v#{version}"
-gem_version = Gem::Version.new(version)
 
 directory "pkg"
 
diff --git a/version.rb b/version.rb
index 92b5e0392a..2cc861a1bd 100644
--- a/version.rb
+++ b/version.rb
@@ -10,7 +10,7 @@ module Rails
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end