Merge branch 'master' into unlock-minitest

421 files changed, 3517 insertions, 2199 deletions

diff --git a/.rubocop.yml b/.rubocop.yml
index 0d1d0c36ce..8a0c55d5d4 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -18,27 +18,27 @@ Style/BracesAroundHashParameters:
   Enabled: true
 
 # Align `when` with `case`.
-Style/CaseIndentation:
+Layout/CaseIndentation:
   Enabled: true
 
 # Align comments with method definitions.
-Style/CommentIndentation:
+Layout/CommentIndentation:
   Enabled: true
 
 # No extra empty lines.
-Style/EmptyLines:
+Layout/EmptyLines:
   Enabled: true
 
 # In a regular class definition, no empty lines around the body.
-Style/EmptyLinesAroundClassBody:
+Layout/EmptyLinesAroundClassBody:
   Enabled: true
 
 # In a regular method definition, no empty lines around the body.
-Style/EmptyLinesAroundMethodBody:
+Layout/EmptyLinesAroundMethodBody:
   Enabled: true
 
 # In a regular module definition, no empty lines around the body.
-Style/EmptyLinesAroundModuleBody:
+Layout/EmptyLinesAroundModuleBody:
   Enabled: true
 
 # Use Ruby >= 1.9 syntax for hashes. Prefer { a: :b } over { :a => :b }.
@@ -47,30 +47,30 @@ Style/HashSyntax:
 
 # Method definitions after `private` or `protected` isolated calls need one
 # extra level of indentation.
-Style/IndentationConsistency:
+Layout/IndentationConsistency:
   Enabled: true
   EnforcedStyle: rails
 
 # Two spaces, no tabs (for indentation).
-Style/IndentationWidth:
+Layout/IndentationWidth:
   Enabled: true
 
-Style/SpaceAfterColon:
+Layout/SpaceAfterColon:
   Enabled: true
 
-Style/SpaceAfterComma:
+Layout/SpaceAfterComma:
   Enabled: true
 
-Style/SpaceAroundEqualsInParameterDefault:
+Layout/SpaceAroundEqualsInParameterDefault:
   Enabled: true
 
-Style/SpaceAroundKeyword:
+Layout/SpaceAroundKeyword:
   Enabled: true
 
-Style/SpaceAroundOperators:
+Layout/SpaceAroundOperators:
   Enabled: true
 
-Style/SpaceBeforeFirstArg:
+Layout/SpaceBeforeFirstArg:
     Enabled: true
 
 # Defining a method with parameters needs parentheses.
@@ -78,18 +78,18 @@ Style/MethodDefParentheses:
   Enabled: true
 
 # Use `foo {}` not `foo{}`.
-Style/SpaceBeforeBlockBraces:
+Layout/SpaceBeforeBlockBraces:
   Enabled: true
 
 # Use `foo { bar }` not `foo {bar}`.
-Style/SpaceInsideBlockBraces:
+Layout/SpaceInsideBlockBraces:
   Enabled: true
 
 # Use `{ a: 1 }` not `{a:1}`.
-Style/SpaceInsideHashLiteralBraces:
+Layout/SpaceInsideHashLiteralBraces:
   Enabled: true
 
-Style/SpaceInsideParens:
+Layout/SpaceInsideParens:
   Enabled: true
 
 # Check quotes usage according to lint rule below.
@@ -98,15 +98,15 @@ Style/StringLiterals:
   EnforcedStyle: double_quotes
 
 # Detect hard tabs, no hard tabs.
-Style/Tab:
+Layout/Tab:
   Enabled: true
 
 # Blank lines should not have any spaces.
-Style/TrailingBlankLines:
+Layout/TrailingBlankLines:
   Enabled: true
 
 # No trailing whitespace.
-Style/TrailingWhitespace:
+Layout/TrailingWhitespace:
   Enabled: true
 
 # Use quotes for string literals when they are enough.
diff --git a/.travis.yml b/.travis.yml
index 19fc899a8b..de708c509c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -98,17 +98,17 @@ matrix:
         - "GEM=ar:postgresql POSTGRES=9.2"
       addons:
         postgresql: "9.2"
-    - rvm: jruby-9.1.8.0
+    - rvm: jruby-9.1.10.0
       jdk: oraclejdk8
       env:
         - "GEM=ap"
-    - rvm: jruby-9.1.8.0
+    - rvm: jruby-9.1.10.0
       jdk: oraclejdk8
       env:
         - "GEM=am,amo,aj"
   allow_failures:
     - rvm: ruby-head
-    - rvm: jruby-9.1.8.0
+    - rvm: jruby-9.1.10.0
     - env: "GEM=ac:integration"
   fast_finish: true
 
diff --git a/Gemfile b/Gemfile
index dbfc76df82..a5ea858177 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,7 +16,7 @@ gem "rake", ">= 11.1"
 # be loaded after loading the test library.
 gem "mocha", "~> 0.14", require: false
 
-gem "capybara", "~> 2.13.0"
+gem "capybara", "~> 2.13"
 
 gem "rack-cache", "~> 1.2"
 gem "jquery-rails"
@@ -33,8 +33,8 @@ gem "bcrypt", "~> 3.1.11", require: false
 # sprockets.
 gem "uglifier", ">= 1.3.0", require: false
 
-# FIXME: Remove this fork after https://github.com/nex3/rb-inotify/pull/49 is fixed.
-gem "rb-inotify", github: "matthewd/rb-inotify", branch: "close-handling", require: false
+# FIXME: Pending rb-inotify 0.9.9 release
+gem "rb-inotify", github: "guard/rb-inotify", branch: "master", require: false
 
 # Explicitly avoid 1.x that doesn't support Ruby 2.4+
 gem "json", ">= 2.0.0"
@@ -90,7 +90,7 @@ group :cable do
 end
 
 # Add your own local bundler stuff.
-local_gemfile = File.dirname(__FILE__) + "/.Gemfile"
+local_gemfile = File.expand_path(".Gemfile", __dir__)
 instance_eval File.read local_gemfile if File.exist? local_gemfile
 
 group :test do
@@ -153,3 +153,7 @@ end
 gem "ibm_db" if ENV["IBM_DB"]
 gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
 gem "wdm", ">= 0.1.0", platforms: [:mingw, :mswin, :x64_mingw, :mswin64]
+
+platforms :ruby_25 do
+  gem "mathn"
+end
diff --git a/Gemfile.lock b/Gemfile.lock
index 71078c095f..4c2c3e8695 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -7,12 +7,12 @@ GIT
       pg (>= 0.17, < 0.20)
 
 GIT
-  remote: https://github.com/matthewd/rb-inotify.git
-  revision: 90553518d1fb79aedc98a3036c59bd2b6731ac40
-  branch: close-handling
+  remote: https://github.com/guard/rb-inotify.git
+  revision: 7e3c714a09ae2b38d2620835e794150d8857cd49
+  branch: master
   specs:
-    rb-inotify (0.9.7)
-      ffi (>= 0.5.0)
+    rb-inotify (0.9.9)
+      ffi (~> 1.0)
 
 GIT
   remote: https://github.com/matthewd/websocket-client-simple.git
@@ -25,7 +25,7 @@ GIT
 
 GIT
   remote: https://github.com/rails/arel.git
-  revision: 437aa3a4bb8ad4f3f4eba299dbb1112852f9c7ac
+  revision: 5db56a513286814991c27000af2c0243cc19d1e2
   specs:
     arel (8.0.0)
 
@@ -91,7 +91,7 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.5.0)
+    addressable (2.5.1)
       public_suffix (~> 2.0, >= 2.0.2)
     amq-protocol (2.1.0)
     ast (2.3.0)
@@ -125,7 +125,7 @@ GEM
     bunny (2.6.2)
       amq-protocol (>= 2.0.1)
     byebug (9.0.6)
-    capybara (2.13.0)
+    capybara (2.14.0)
       addressable
       mime-types (>= 1.16)
       nokogiri (>= 1.3.3)
@@ -148,10 +148,10 @@ GEM
     daemons (1.2.4)
     dalli (2.7.6)
     dante (0.2.0)
-    delayed_job (4.1.2)
-      activesupport (>= 3.0, < 5.1)
-    delayed_job_active_record (4.1.1)
-      activerecord (>= 3.0, < 5.1)
+    delayed_job (4.1.3)
+      activesupport (>= 3.0, < 5.2)
+    delayed_job_active_record (4.1.2)
+      activerecord (>= 3.0, < 5.2)
       delayed_job (>= 3.0, < 5)
     em-hiredis (0.3.1)
       eventmachine (~> 1.0)
@@ -207,8 +207,9 @@ GEM
       ruby_dep (~> 1.2)
     loofah (2.0.3)
       nokogiri (>= 1.5.9)
-    mail (2.6.4)
+    mail (2.6.5)
       mime-types (>= 1.16, < 4)
+    mathn (0.1.0)
     metaclass (0.0.4)
     method_source (0.8.2)
     mime-types (3.1)
@@ -227,16 +228,17 @@ GEM
     multi_json (1.12.1)
     multipart-post (2.0.0)
     mustache (1.0.3)
-    mysql2 (0.4.5)
-    mysql2 (0.4.5-x64-mingw32)
-    mysql2 (0.4.5-x86-mingw32)
+    mysql2 (0.4.6)
+    mysql2 (0.4.6-x64-mingw32)
+    mysql2 (0.4.6-x86-mingw32)
     nio4r (2.0.0)
-    nokogiri (1.7.0.1)
+    nokogiri (1.7.1)
       mini_portile2 (~> 2.1.0)
-    nokogiri (1.7.0.1-x64-mingw32)
+    nokogiri (1.7.1-x64-mingw32)
       mini_portile2 (~> 2.1.0)
-    nokogiri (1.7.0.1-x86-mingw32)
+    nokogiri (1.7.1-x86-mingw32)
       mini_portile2 (~> 2.1.0)
+    parallel (1.11.2)
     parser (2.4.0.0)
       ast (~> 2.2)
     path_expander (1.0.1)
@@ -255,10 +257,10 @@ GEM
       simple_uuid
     que (0.12.0)
     racc (1.4.14)
-    rack (2.0.1)
+    rack (2.0.3)
     rack-cache (1.6.1)
       rack (>= 0.4)
-    rack-protection (1.5.3)
+    rack-protection (2.0.0)
       rack
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -267,12 +269,13 @@ GEM
       nokogiri (~> 1.6)
     rails-html-sanitizer (1.0.3)
       loofah (~> 2.0)
-    rainbow (2.2.1)
+    rainbow (2.2.2)
+      rake
     rake (12.0.0)
     rb-fsevent (0.9.8)
     rdoc (5.1.0)
     redcarpet (3.2.3)
-    redis (3.3.2)
+    redis (3.3.3)
     redis-namespace (1.5.2)
       redis (~> 3.0, >= 3.0.4)
     resque (1.27.0)
@@ -286,7 +289,8 @@ GEM
       redis (~> 3.3)
       resque (~> 1.26)
       rufus-scheduler (~> 3.2)
-    rubocop (0.48.1)
+    rubocop (0.49.0)
+      parallel (~> 1.10)
       parser (>= 2.3.3.1, < 3.0)
       powerpack (~> 0.1)
       rainbow (>= 1.99.1, < 3.0)
@@ -313,11 +317,11 @@ GEM
     sequel (4.42.1)
     serverengine (1.5.11)
       sigdump (~> 0.2.2)
-    sidekiq (4.2.9)
+    sidekiq (5.0.0)
       concurrent-ruby (~> 1.0)
       connection_pool (~> 2.2, >= 2.2.0)
       rack-protection (>= 1.5.0)
-      redis (~> 3.2, >= 3.2.1)
+      redis (~> 3.3, >= 3.3.3)
     sigdump (0.2.4)
     simple_uuid (0.4.0)
     sinatra (1.0)
@@ -389,7 +393,7 @@ DEPENDENCIES
   blade
   blade-sauce_labs_plugin
   byebug
-  capybara (~> 2.13.0)
+  capybara (~> 2.13)
   coffee-rails
   dalli (>= 2.2.1)
   delayed_job
@@ -402,6 +406,7 @@ DEPENDENCIES
   kindlerb (~> 1.2.0)
   libxml-ruby
   listen (>= 3.0.5, < 3.2)
+  mathn
   minitest-bisect
   mocha (~> 0.14)
   mysql2 (>= 0.4.4)
@@ -439,4 +444,4 @@ DEPENDENCIES
   websocket-client-simple!
 
 BUNDLED WITH
-   1.14.6
+   1.15.0
diff --git a/Rakefile b/Rakefile
index 202eb5e6fc..ae269fbce7 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,6 +1,6 @@
 require "net/http"
 
-$:.unshift File.expand_path("..", __FILE__)
+$:.unshift __dir__
 require "tasks/release"
 require "railties/lib/rails/api/task"
 
diff --git a/actioncable/CHANGELOG.md b/actioncable/CHANGELOG.md
index f0502c06ff..2bf11da463 100644
--- a/actioncable/CHANGELOG.md
+++ b/actioncable/CHANGELOG.md
@@ -3,5 +3,6 @@
     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 e044f54b45..d14f20d75b 100644
--- a/actioncable/README.md
+++ b/actioncable/README.md
@@ -409,7 +409,7 @@ application. The recommended basic setup is as follows:
 
 ```ruby
 # cable/config.ru
-require ::File.expand_path('../../config/environment', __FILE__)
+require ::File.expand_path('../config/environment', __dir__)
 Rails.application.eager_load!
 
 run ActionCable.server
diff --git a/actioncable/Rakefile b/actioncable/Rakefile
index bda8c7b6c8..e21843bb44 100644
--- a/actioncable/Rakefile
+++ b/actioncable/Rakefile
@@ -3,15 +3,13 @@ require "pathname"
 require "open3"
 require "action_cable"
 
-dir = File.dirname(__FILE__)
-
 task default: :test
 
 task package: %w( assets:compile assets:verify )
 
 Rake::TestTask.new do |t|
   t.libs << "test"
-  t.test_files = Dir.glob("#{dir}/test/**/*_test.rb")
+  t.test_files = Dir.glob("#{__dir__}/test/**/*_test.rb")
   t.warning = true
   t.verbose = true
   t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
@@ -46,7 +44,7 @@ namespace :assets do
   desc "Verify compiled Action Cable assets"
   task :verify do
     file = "lib/assets/compiled/action_cable.js"
-    pathname = Pathname.new("#{dir}/#{file}")
+    pathname = Pathname.new("#{__dir__}/#{file}")
 
     print "[verify] #{file} exists "
     if pathname.exist?
@@ -64,8 +62,8 @@ namespace :assets do
       fail
     end
 
-    print "[verify] #{dir} can be required as a module "
-    stdout, stderr, status = Open3.capture3("node", "--print", "window = {}; require('#{dir}');")
+    print "[verify] #{__dir__} can be required as a module "
+    _, stderr, status = Open3.capture3("node", "--print", "window = {}; require('#{__dir__}');")
     if status.success?
       puts "[OK]"
     else
diff --git a/actioncable/actioncable.gemspec b/actioncable/actioncable.gemspec
index 6d95f022fa..05ffd655e8 100644
--- a/actioncable/actioncable.gemspec
+++ b/actioncable/actioncable.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/actioncable/lib/action_cable/channel/periodic_timers.rb b/actioncable/lib/action_cable/channel/periodic_timers.rb
index c9daa0bcd3..90c68cfe84 100644
--- a/actioncable/lib/action_cable/channel/periodic_timers.rb
+++ b/actioncable/lib/action_cable/channel/periodic_timers.rb
@@ -4,8 +4,7 @@ module ActionCable
       extend ActiveSupport::Concern
 
       included do
-        class_attribute :periodic_timers, instance_reader: false
-        self.periodic_timers = []
+        class_attribute :periodic_timers, instance_reader: false, default: []
 
         after_subscribe   :start_periodic_timers
         after_unsubscribe :stop_periodic_timers
diff --git a/actioncable/lib/action_cable/connection/identification.rb b/actioncable/lib/action_cable/connection/identification.rb
index c91a1d1fd7..ffab359429 100644
--- a/actioncable/lib/action_cable/connection/identification.rb
+++ b/actioncable/lib/action_cable/connection/identification.rb
@@ -6,8 +6,7 @@ module ActionCable
       extend ActiveSupport::Concern
 
       included do
-        class_attribute :identifiers
-        self.identifiers = Set.new
+        class_attribute :identifiers, default: Set.new
       end
 
       class_methods do
diff --git a/actioncable/lib/action_cable/remote_connections.rb b/actioncable/lib/action_cable/remote_connections.rb
index d2856bc6ae..e689fbf21b 100644
--- a/actioncable/lib/action_cable/remote_connections.rb
+++ b/actioncable/lib/action_cable/remote_connections.rb
@@ -45,7 +45,7 @@ module ActionCable
         end
 
         # Returns all the identifiers that were applied to this connection.
-        def identifiers
+        redefine_method :identifiers do
           server.connection_identifiers
         end
 
diff --git a/actioncable/lib/rails/generators/channel/channel_generator.rb b/actioncable/lib/rails/generators/channel/channel_generator.rb
index 984b78bc9c..80f512c94c 100644
--- a/actioncable/lib/rails/generators/channel/channel_generator.rb
+++ b/actioncable/lib/rails/generators/channel/channel_generator.rb
@@ -1,7 +1,7 @@
 module Rails
   module Generators
     class ChannelGenerator < NamedBase
-      source_root File.expand_path("../templates", __FILE__)
+      source_root File.expand_path("templates", __dir__)
 
       argument :actions, type: :array, default: [], banner: "method method"
 
diff --git a/actioncable/test/test_helper.rb b/actioncable/test/test_helper.rb
index a47032753b..5d246c2b76 100644
--- a/actioncable/test/test_helper.rb
+++ b/actioncable/test/test_helper.rb
@@ -11,7 +11,7 @@ rescue LoadError
 end
 
 # Require all the stubs and models
-Dir[File.dirname(__FILE__) + "/stubs/*.rb"].each { |file| require file }
+Dir[File.expand_path("stubs/*.rb", __dir__)].each { |file| require file }
 
 class ActionCable::TestCase < ActiveSupport::TestCase
   def wait_for_async
diff --git a/actionmailer/actionmailer.gemspec b/actionmailer/actionmailer.gemspec
index e75dae6cf9..5eadd01407 100644
--- a/actionmailer/actionmailer.gemspec
+++ b/actionmailer/actionmailer.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/actionmailer/lib/action_mailer.rb b/actionmailer/lib/action_mailer.rb
index 211190560a..8e59f033d0 100644
--- a/actionmailer/lib/action_mailer.rb
+++ b/actionmailer/lib/action_mailer.rb
@@ -25,6 +25,7 @@ require "abstract_controller"
 require "action_mailer/version"
 
 # Common Active Support usage in Action Mailer
+require "active_support"
 require "active_support/rails"
 require "active_support/core_ext/class"
 require "active_support/core_ext/module/attr_internal"
diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 6849f5c0f9..7133670b65 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -459,8 +459,7 @@ module ActionMailer
 
     helper ActionMailer::MailHelper
 
-    class_attribute :default_params
-    self.default_params = {
+    class_attribute :default_params, default: {
       mime_version: "1.0",
       charset:      "UTF-8",
       content_type: "text/plain",
diff --git a/actionmailer/lib/action_mailer/delivery_methods.rb b/actionmailer/lib/action_mailer/delivery_methods.rb
index bcc4ef03cf..afdc28aa2a 100644
--- a/actionmailer/lib/action_mailer/delivery_methods.rb
+++ b/actionmailer/lib/action_mailer/delivery_methods.rb
@@ -7,8 +7,6 @@ module ActionMailer
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :delivery_methods, :delivery_method
-
       # Do not make this inheritable, because we always want it to propagate
       cattr_accessor :raise_delivery_errors
       self.raise_delivery_errors = true
@@ -19,8 +17,8 @@ module ActionMailer
       cattr_accessor :deliver_later_queue_name
       self.deliver_later_queue_name = :mailers
 
-      self.delivery_methods = {}.freeze
-      self.delivery_method  = :smtp
+      class_attribute :delivery_methods, default: {}.freeze
+      class_attribute :delivery_method, default: :smtp
 
       add_delivery_method :smtp, Mail::SMTP,
         address:              "localhost",
diff --git a/actionmailer/lib/rails/generators/mailer/mailer_generator.rb b/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
index 99fe4544f1..bc21b07109 100644
--- a/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
+++ b/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
@@ -1,7 +1,7 @@
 module Rails
   module Generators
     class MailerGenerator < NamedBase
-      source_root File.expand_path("../templates", __FILE__)
+      source_root File.expand_path("templates", __dir__)
 
       argument :actions, type: :array, default: [], banner: "method method"
 
diff --git a/actionmailer/test/abstract_unit.rb b/actionmailer/test/abstract_unit.rb
index a646cbd581..dbfdb07e6e 100644
--- a/actionmailer/test/abstract_unit.rb
+++ b/actionmailer/test/abstract_unit.rb
@@ -9,7 +9,7 @@ end
 
 module Rails
   def self.root
-    File.expand_path("../", File.dirname(__FILE__))
+    File.expand_path("..", __dir__)
   end
 end
 
@@ -28,7 +28,7 @@ ActiveSupport::Deprecation.debug = true
 # Disable available locale checks to avoid warnings running the test suite.
 I18n.enforce_available_locales = false
 
-FIXTURE_LOAD_PATH = File.expand_path("fixtures", File.dirname(__FILE__))
+FIXTURE_LOAD_PATH = File.expand_path("fixtures", __dir__)
 ActionMailer::Base.view_paths = FIXTURE_LOAD_PATH
 
 class ActiveSupport::TestCase
diff --git a/actionmailer/test/caching_test.rb b/actionmailer/test/caching_test.rb
index cff49c8894..e76466439e 100644
--- a/actionmailer/test/caching_test.rb
+++ b/actionmailer/test/caching_test.rb
@@ -5,7 +5,7 @@ require "mailers/caching_mailer"
 
 CACHE_DIR = "test_cache"
 # Don't change '/../temp/' cavalierly or you might hose something you don't want hosed
-FILE_STORE_PATH = File.join(File.dirname(__FILE__), "/../temp/", CACHE_DIR)
+FILE_STORE_PATH = File.join(__dir__, "/../temp/", CACHE_DIR)
 
 class FragmentCachingMailer < ActionMailer::Base
   abstract!
@@ -21,10 +21,6 @@ class BaseCachingTest < ActiveSupport::TestCase
     @mailer.perform_caching = true
     @mailer.cache_store = @store
   end
-
-  def test_fragment_cache_key
-    assert_equal "views/what a key", @mailer.fragment_cache_key("what a key")
-  end
 end
 
 class FragmentCachingTest < BaseCachingTest
@@ -126,7 +122,7 @@ class FunctionalFragmentCachingTest < BaseCachingTest
 
     assert_match expected_body, email.body.encoded
     assert_match expected_body,
-      @store.read("views/caching/#{template_digest("caching_mailer/fragment_cache")}")
+      @store.read("views/caching_mailer/fragment_cache:#{template_digest("caching_mailer/fragment_cache")}/caching")
   end
 
   def test_fragment_caching_in_partials
@@ -135,7 +131,7 @@ class FunctionalFragmentCachingTest < BaseCachingTest
     assert_match(expected_body, email.body.encoded)
 
     assert_match(expected_body,
-      @store.read("views/caching/#{template_digest("caching_mailer/_partial")}"))
+      @store.read("views/caching_mailer/_partial:#{template_digest("caching_mailer/_partial")}/caching"))
   end
 
   def test_skip_fragment_cache_digesting
@@ -185,7 +181,7 @@ class FunctionalFragmentCachingTest < BaseCachingTest
     end
 
     assert_equal "caching_mailer", payload[:mailer]
-    assert_equal "views/caching/#{template_digest("caching_mailer/fragment_cache")}", payload[:key]
+    assert_equal [ :views, "caching_mailer/fragment_cache:#{template_digest("caching_mailer/fragment_cache")}", :caching ], payload[:key]
   ensure
     @mailer.enable_fragment_cache_logging = true
   end
diff --git a/actionmailer/test/log_subscriber_test.rb b/actionmailer/test/log_subscriber_test.rb
index d864c3acca..799c6144d7 100644
--- a/actionmailer/test/log_subscriber_test.rb
+++ b/actionmailer/test/log_subscriber_test.rb
@@ -26,7 +26,7 @@ class AMLogSubscriberTest < ActionMailer::TestCase
     wait
 
     assert_equal(1, @logger.logged(:info).size)
-    assert_match(/Sent mail to system@test.lindsaar.net/, @logger.logged(:info).first)
+    assert_match(/Sent mail to system@test\.lindsaar\.net/, @logger.logged(:info).first)
 
     assert_equal(2, @logger.logged(:debug).size)
     assert_match(/BaseMailer#welcome: processed outbound mail in [\d.]+ms/, @logger.logged(:debug).first)
@@ -36,7 +36,7 @@ class AMLogSubscriberTest < ActionMailer::TestCase
   end
 
   def test_receive_is_notified
-    fixture = File.read(File.dirname(__FILE__) + "/fixtures/raw_email")
+    fixture = File.read(File.expand_path("fixtures/raw_email", __dir__))
     TestMailer.receive(fixture)
     wait
     assert_equal(1, @logger.logged(:info).size)
diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 51cec82801..54937617df 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,4 +1,27 @@
-*  Add `action_controller_api` and `action_controller_base` load hooks to be called in `ActiveSupport.on_load`
+*   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
+    encrypted using AES in CBC HMAC mode will be seamlessly upgraded when
+    this new mode is enabled via the
+    `action_dispatch.use_authenticated_cookie_encryption` configuration value.
+
+    *Michael J Coyne*
+
+*   Change the cache key format for fragments to make it easier to debug key churn. The new format is:
+
+        views/template/action.html.erb:7a1156131a6928cb0026877f8b749ac9/projects/123
+              ^template path           ^template tree digest            ^class   ^id
+
+    *DHH*
+
+*   Add support for recyclable cache keys with fragment caching. This uses the new versioned entries in the
+    `ActiveSupport::Cache` stores and relies on the fact that Active Record has split `#cache_key` and `#cache_version`
+    to support it.
+
+    *DHH*
+
+*   Add `action_controller_api` and `action_controller_base` load hooks to be called in `ActiveSupport.on_load`
 
     `ActionController::Base` and `ActionController::API` have differing implementations. This means that
     the one umbrella hook `action_controller` is not able to address certain situations where a method
@@ -10,4 +33,5 @@
 
     *Julian Nadeau*
 
+
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionpack/CHANGELOG.md) for previous changes.
diff --git a/actionpack/Rakefile b/actionpack/Rakefile
index 31dd1865f9..69408c8aab 100644
--- a/actionpack/Rakefile
+++ b/actionpack/Rakefile
@@ -26,7 +26,7 @@ namespace :test do
 end
 
 task :lines do
-  load File.expand_path("..", File.dirname(__FILE__)) + "/tools/line_statistics"
+  load File.expand_path("..", __dir__) + "/tools/line_statistics"
   files = FileList["lib/**/*.rb"]
   CodeTools::LineStatistics.new(files).print_loc
 end
diff --git a/actionpack/actionpack.gemspec b/actionpack/actionpack.gemspec
index 2c24a54305..31803042dd 100644
--- a/actionpack/actionpack.gemspec
+++ b/actionpack/actionpack.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/actionpack/lib/abstract_controller/base.rb b/actionpack/lib/abstract_controller/base.rb
index e7cb6347a2..dc79820a82 100644
--- a/actionpack/lib/abstract_controller/base.rb
+++ b/actionpack/lib/abstract_controller/base.rb
@@ -14,8 +14,16 @@ module AbstractController
   # expected to provide their own +render+ method, since rendering means
   # different things depending on the context.
   class Base
+    ##
+    # Returns the body of the HTTP response sent by the controller.
     attr_internal :response_body
+
+    ##
+    # Returns the name of the action this controller is processing.
     attr_internal :action_name
+
+    ##
+    # Returns the formats that can be processed by the controller.
     attr_internal :formats
 
     include ActiveSupport::Configurable
diff --git a/actionpack/lib/abstract_controller/caching.rb b/actionpack/lib/abstract_controller/caching.rb
index 26e3f08bc1..30e3d4426c 100644
--- a/actionpack/lib/abstract_controller/caching.rb
+++ b/actionpack/lib/abstract_controller/caching.rb
@@ -37,8 +37,7 @@ module AbstractController
       config_accessor :enable_fragment_cache_logging
       self.enable_fragment_cache_logging = false
 
-      class_attribute :_view_cache_dependencies
-      self._view_cache_dependencies = []
+      class_attribute :_view_cache_dependencies, default: []
       helper_method :view_cache_dependencies if respond_to?(:helper_method)
     end
 
diff --git a/actionpack/lib/abstract_controller/caching/fragments.rb b/actionpack/lib/abstract_controller/caching/fragments.rb
index c85b4adba1..14e4a82523 100644
--- a/actionpack/lib/abstract_controller/caching/fragments.rb
+++ b/actionpack/lib/abstract_controller/caching/fragments.rb
@@ -25,7 +25,10 @@ module AbstractController
 
         self.fragment_cache_keys = []
 
-        helper_method :fragment_cache_key if respond_to?(:helper_method)
+        if respond_to?(:helper_method)
+          helper_method :fragment_cache_key
+          helper_method :combined_fragment_cache_key
+        end
       end
 
       module ClassMethods
@@ -62,17 +65,36 @@ module AbstractController
       # with the specified +key+ value. The key is expanded using
       # ActiveSupport::Cache.expand_cache_key.
       def fragment_cache_key(key)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          Calling fragment_cache_key directly is deprecated and will be removed in Rails 6.0.
+          All fragment accessors now use the combined_fragment_cache_key method that retains the key as an array,
+          such that the caching stores can interrogate the parts for cache versions used in
+          recyclable cache keys.
+        MSG
+
         head = self.class.fragment_cache_keys.map { |k| instance_exec(&k) }
         tail = key.is_a?(Hash) ? url_for(key).split("://").last : key
         ActiveSupport::Cache.expand_cache_key([*head, *tail], :views)
       end
 
+      # Given a key (as described in +expire_fragment+), returns
+      # a key array suitable for use in reading, writing, or expiring a
+      # cached fragment. All keys begin with <tt>:views</tt>,
+      # followed by ENV["RAILS_CACHE_ID"] or ENV["RAILS_APP_VERSION"] if set,
+      # followed by any controller-wide key prefix values, ending
+      # with the specified +key+ value.
+      def combined_fragment_cache_key(key)
+        head = self.class.fragment_cache_keys.map { |k| instance_exec(&k) }
+        tail = key.is_a?(Hash) ? url_for(key).split("://").last : key
+        [ :views, (ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]), *head, *tail ].compact
+      end
+
       # Writes +content+ to the location signified by
       # +key+ (see +expire_fragment+ for acceptable formats).
       def write_fragment(key, content, options = nil)
         return content unless cache_configured?
 
-        key = fragment_cache_key(key)
+        key = combined_fragment_cache_key(key)
         instrument_fragment_cache :write_fragment, key do
           content = content.to_str
           cache_store.write(key, content, options)
@@ -85,7 +107,7 @@ module AbstractController
       def read_fragment(key, options = nil)
         return unless cache_configured?
 
-        key = fragment_cache_key(key)
+        key = combined_fragment_cache_key(key)
         instrument_fragment_cache :read_fragment, key do
           result = cache_store.read(key, options)
           result.respond_to?(:html_safe) ? result.html_safe : result
@@ -96,7 +118,7 @@ module AbstractController
       # +key+ exists (see +expire_fragment+ for acceptable formats).
       def fragment_exist?(key, options = nil)
         return unless cache_configured?
-        key = fragment_cache_key(key)
+        key = combined_fragment_cache_key(key)
 
         instrument_fragment_cache :exist_fragment?, key do
           cache_store.exist?(key, options)
@@ -123,7 +145,7 @@ module AbstractController
       # method (or <tt>delete_matched</tt>, for Regexp keys).
       def expire_fragment(key, options = nil)
         return unless cache_configured?
-        key = fragment_cache_key(key) unless key.is_a?(Regexp)
+        key = combined_fragment_cache_key(key) unless key.is_a?(Regexp)
 
         instrument_fragment_cache :expire_fragment, key do
           if key.is_a?(Regexp)
@@ -135,8 +157,7 @@ module AbstractController
       end
 
       def instrument_fragment_cache(name, key) # :nodoc:
-        payload = instrument_payload(key)
-        ActiveSupport::Notifications.instrument("#{name}.#{instrument_name}", payload) { yield }
+        ActiveSupport::Notifications.instrument("#{name}.#{instrument_name}", instrument_payload(key)) { yield }
       end
     end
   end
diff --git a/actionpack/lib/abstract_controller/callbacks.rb b/actionpack/lib/abstract_controller/callbacks.rb
index ce4ecf17cc..ba7dec6083 100644
--- a/actionpack/lib/abstract_controller/callbacks.rb
+++ b/actionpack/lib/abstract_controller/callbacks.rb
@@ -1,4 +1,24 @@
 module AbstractController
+  # = Abstract Controller Callbacks
+  #
+  # Abstract Controller provides hooks during the life cycle of a controller action.
+  # Callbacks allow you to trigger logic during this cycle. Available callbacks are:
+  #
+  # * <tt>after_action</tt>
+  # * <tt>append_after_action</tt>
+  # * <tt>append_around_action</tt>
+  # * <tt>append_before_action</tt>
+  # * <tt>around_action</tt>
+  # * <tt>before_action</tt>
+  # * <tt>prepend_after_action</tt>
+  # * <tt>prepend_around_action</tt>
+  # * <tt>prepend_before_action</tt>
+  # * <tt>skip_after_action</tt>
+  # * <tt>skip_around_action</tt>
+  # * <tt>skip_before_action</tt>
+  #
+  # NOTE: Calling the same callback multiple times will overwrite previous callback definitions.
+  #
   module Callbacks
     extend ActiveSupport::Concern
 
diff --git a/actionpack/lib/abstract_controller/helpers.rb b/actionpack/lib/abstract_controller/helpers.rb
index ef3be7af83..2e50637c39 100644
--- a/actionpack/lib/abstract_controller/helpers.rb
+++ b/actionpack/lib/abstract_controller/helpers.rb
@@ -5,11 +5,8 @@ module AbstractController
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_helpers
-      self._helpers = Module.new
-
-      class_attribute :_helper_methods
-      self._helper_methods = Array.new
+      class_attribute :_helpers, default: Module.new
+      class_attribute :_helper_methods, default: Array.new
     end
 
     class MissingHelperError < LoadError
diff --git a/actionpack/lib/action_controller/log_subscriber.rb b/actionpack/lib/action_controller/log_subscriber.rb
index d29a5fe68f..d00fcbcd13 100644
--- a/actionpack/lib/action_controller/log_subscriber.rb
+++ b/actionpack/lib/action_controller/log_subscriber.rb
@@ -60,9 +60,9 @@ module ActionController
       class_eval <<-METHOD, __FILE__, __LINE__ + 1
         def #{method}(event)
           return unless logger.info? && ActionController::Base.enable_fragment_cache_logging
-          key_or_path = event.payload[:key] || event.payload[:path]
+          key         = ActiveSupport::Cache.expand_cache_key(event.payload[:key] || event.payload[:path])
           human_name  = #{method.to_s.humanize.inspect}
-          info("\#{human_name} \#{key_or_path} (\#{event.duration.round(1)}ms)")
+          info("\#{human_name} \#{key} (\#{event.duration.round(1)}ms)")
         end
       METHOD
     end
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 246644dcbd..96c708f45a 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -208,8 +208,7 @@ module ActionController
       @_request.reset_session
     end
 
-    class_attribute :middleware_stack
-    self.middleware_stack = ActionController::MiddlewareStack.new
+    class_attribute :middleware_stack, default: ActionController::MiddlewareStack.new
 
     def self.inherited(base) # :nodoc:
       base.middleware_stack = middleware_stack.dup
diff --git a/actionpack/lib/action_controller/metal/conditional_get.rb b/actionpack/lib/action_controller/metal/conditional_get.rb
index eb636fa3f6..0525252c7c 100644
--- a/actionpack/lib/action_controller/metal/conditional_get.rb
+++ b/actionpack/lib/action_controller/metal/conditional_get.rb
@@ -7,8 +7,7 @@ module ActionController
     include Head
 
     included do
-      class_attribute :etaggers
-      self.etaggers = []
+      class_attribute :etaggers, default: []
     end
 
     module ClassMethods
diff --git a/actionpack/lib/action_controller/metal/etag_with_template_digest.rb b/actionpack/lib/action_controller/metal/etag_with_template_digest.rb
index 798564db96..69c3979a0e 100644
--- a/actionpack/lib/action_controller/metal/etag_with_template_digest.rb
+++ b/actionpack/lib/action_controller/metal/etag_with_template_digest.rb
@@ -22,8 +22,7 @@ module ActionController
     include ActionController::ConditionalGet
 
     included do
-      class_attribute :etag_with_template_digest
-      self.etag_with_template_digest = true
+      class_attribute :etag_with_template_digest, default: true
 
       ActiveSupport.on_load :action_view, yield: true do
         etag do |options|
diff --git a/actionpack/lib/action_controller/metal/flash.rb b/actionpack/lib/action_controller/metal/flash.rb
index 347fbf0e74..24d1097ebe 100644
--- a/actionpack/lib/action_controller/metal/flash.rb
+++ b/actionpack/lib/action_controller/metal/flash.rb
@@ -3,8 +3,7 @@ module ActionController #:nodoc:
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_flash_types, instance_accessor: false
-      self._flash_types = []
+      class_attribute :_flash_types, instance_accessor: false, default: []
 
       delegate :flash, to: :request
       add_flash_types(:alert, :notice)
diff --git a/actionpack/lib/action_controller/metal/helpers.rb b/actionpack/lib/action_controller/metal/helpers.rb
index 476d081239..913a4b9a04 100644
--- a/actionpack/lib/action_controller/metal/helpers.rb
+++ b/actionpack/lib/action_controller/metal/helpers.rb
@@ -53,9 +53,8 @@ module ActionController
     include AbstractController::Helpers
 
     included do
-      class_attribute :helpers_path, :include_all_helpers
-      self.helpers_path ||= []
-      self.include_all_helpers = true
+      class_attribute :helpers_path, default: []
+      class_attribute :include_all_helpers, default: true
     end
 
     module ClassMethods
diff --git a/actionpack/lib/action_controller/metal/params_wrapper.rb b/actionpack/lib/action_controller/metal/params_wrapper.rb
index a89fc1678b..68881b8402 100644
--- a/actionpack/lib/action_controller/metal/params_wrapper.rb
+++ b/actionpack/lib/action_controller/metal/params_wrapper.rb
@@ -159,8 +159,7 @@ module ActionController
     end
 
     included do
-      class_attribute :_wrapper_options
-      self._wrapper_options = Options.from_hash(format: [])
+      class_attribute :_wrapper_options, default: Options.from_hash(format: [])
     end
 
     module ClassMethods
diff --git a/actionpack/lib/action_controller/metal/renderers.rb b/actionpack/lib/action_controller/metal/renderers.rb
index 733aca195d..23c21b0501 100644
--- a/actionpack/lib/action_controller/metal/renderers.rb
+++ b/actionpack/lib/action_controller/metal/renderers.rb
@@ -26,8 +26,7 @@ module ActionController
     RENDERERS = Set.new
 
     included do
-      class_attribute :_renderers
-      self._renderers = Set.new.freeze
+      class_attribute :_renderers, default: Set.new.freeze
     end
 
     # Used in <tt>ActionController::Base</tt>
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 7864f9decd..20330b5091 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -666,8 +666,8 @@ module ActionController
     # to key. If the key is not found, returns the default value. If the
     # optional code block is given and the key is not found, pass in the key
     # and return the result of block.
-    def delete(key)
-      convert_value_to_parameters(@parameters.delete(key))
+    def delete(key, &block)
+      convert_value_to_parameters(@parameters.delete(key, &block))
     end
 
     # Returns a new instance of <tt>ActionController::Parameters</tt> with only
diff --git a/actionpack/lib/action_dispatch/http/upload.rb b/actionpack/lib/action_dispatch/http/upload.rb
index 61ba052e45..225272d66e 100644
--- a/actionpack/lib/action_dispatch/http/upload.rb
+++ b/actionpack/lib/action_dispatch/http/upload.rb
@@ -27,14 +27,18 @@ module ActionDispatch
         @tempfile = hash[:tempfile]
         raise(ArgumentError, ":tempfile is required") unless @tempfile
 
-        @original_filename = hash[:filename]
-        if @original_filename
+        if hash[:filename]
+          @original_filename = hash[:filename].dup
+
           begin
             @original_filename.encode!(Encoding::UTF_8)
           rescue EncodingError
             @original_filename.force_encoding(Encoding::UTF_8)
           end
+        else
+          @original_filename = nil
         end
+
         @content_type      = hash[:type]
         @headers           = hash[:head]
       end
diff --git a/actionpack/lib/action_dispatch/journey/gtg/simulator.rb b/actionpack/lib/action_dispatch/journey/gtg/simulator.rb
index d692f6415c..62f052ced6 100644
--- a/actionpack/lib/action_dispatch/journey/gtg/simulator.rb
+++ b/actionpack/lib/action_dispatch/journey/gtg/simulator.rb
@@ -18,14 +18,6 @@ module ActionDispatch
           @tt = transition_table
         end
 
-        def simulate(string)
-          ms = memos(string) { return }
-          MatchData.new(ms)
-        end
-
-        alias :=~    :simulate
-        alias :match :simulate
-
         def memos(string)
           input = StringScanner.new(string)
           state = [0]
diff --git a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
index e1ac2c873e..45aff287b1 100644
--- a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
+++ b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
@@ -82,7 +82,7 @@ module ActionDispatch
         end
 
         def visualizer(paths, title = "FSM")
-          viz_dir   = File.join File.dirname(__FILE__), "..", "visualizer"
+          viz_dir   = File.join __dir__, "..", "visualizer"
           fsm_js    = File.read File.join(viz_dir, "fsm.js")
           fsm_css   = File.read File.join(viz_dir, "fsm.css")
           erb       = File.read File.join(viz_dir, "index.html.erb")
diff --git a/actionpack/lib/action_dispatch/journey/router/utils.rb b/actionpack/lib/action_dispatch/journey/router/utils.rb
index ffcd875b4d..6d400f3364 100644
--- a/actionpack/lib/action_dispatch/journey/router/utils.rb
+++ b/actionpack/lib/action_dispatch/journey/router/utils.rb
@@ -13,11 +13,13 @@ module ActionDispatch
         #   normalize_path("")      # => "/"
         #   normalize_path("/%ab")  # => "/%AB"
         def self.normalize_path(path)
+          encoding = path.encoding
           path = "/#{path}"
           path.squeeze!("/".freeze)
           path.sub!(%r{/+\Z}, "".freeze)
           path.gsub!(/(%[a-f0-9]{2})/) { $1.upcase }
           path = "/" if path == "".freeze
+          path.force_encoding(encoding)
           path
         end
 
@@ -59,11 +61,11 @@ module ActionDispatch
           end
 
           private
-            def escape(component, pattern) # :doc:
+            def escape(component, pattern)
               component.gsub(pattern) { |unsafe| percent_encode(unsafe) }.force_encoding(US_ASCII)
             end
 
-            def percent_encode(unsafe) # :doc:
+            def percent_encode(unsafe)
               safe = EMPTY.dup
               unsafe.each_byte { |b| safe << DEC2HEX[b] }
               safe
@@ -84,6 +86,10 @@ module ActionDispatch
           ENCODER.escape_fragment(fragment.to_s)
         end
 
+        # Replaces any escaped sequences with their unescaped representations.
+        #
+        #   uri = "/topics?title=Ruby%20on%20Rails"
+        #   unescape_uri(uri)  #=> "/topics?title=Ruby on Rails"
         def self.unescape_uri(uri)
           ENCODER.unescape_uri(uri)
         end
diff --git a/actionpack/lib/action_dispatch/middleware/cookies.rb b/actionpack/lib/action_dispatch/middleware/cookies.rb
index e565c03a8a..c0dda1bba5 100644
--- a/actionpack/lib/action_dispatch/middleware/cookies.rb
+++ b/actionpack/lib/action_dispatch/middleware/cookies.rb
@@ -43,6 +43,10 @@ module ActionDispatch
       get_header Cookies::ENCRYPTED_SIGNED_COOKIE_SALT
     end
 
+    def authenticated_encrypted_cookie_salt
+      get_header Cookies::AUTHENTICATED_ENCRYPTED_COOKIE_SALT
+    end
+
     def secret_token
       get_header Cookies::SECRET_TOKEN
     end
@@ -149,6 +153,7 @@ module ActionDispatch
     SIGNED_COOKIE_SALT = "action_dispatch.signed_cookie_salt".freeze
     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
     SECRET_TOKEN = "action_dispatch.secret_token".freeze
     SECRET_KEY_BASE = "action_dispatch.secret_key_base".freeze
     COOKIES_SERIALIZER = "action_dispatch.cookies_serializer".freeze
@@ -207,6 +212,9 @@ module ActionDispatch
       # If +secrets.secret_key_base+ and +secrets.secret_token+ (deprecated) are both set,
       # legacy cookies signed with the old key generator will be transparently upgraded.
       #
+      # If +config.action_dispatch.encrypted_cookie_salt+ and +config.action_dispatch.encrypted_signed_cookie_salt+
+      # are both set, legacy cookies encrypted with HMAC AES-256-CBC will be transparently upgraded.
+      #
       # This jar requires that you set a suitable secret for the verification on your app's +secrets.secret_key_base+.
       #
       # Example:
@@ -219,6 +227,8 @@ module ActionDispatch
         @encrypted ||=
           if upgrade_legacy_signed_cookies?
             UpgradeLegacyEncryptedCookieJar.new(self)
+          elsif upgrade_legacy_hmac_aes_cbc_cookies?
+            UpgradeLegacyHmacAesCbcCookieJar.new(self)
           else
             EncryptedCookieJar.new(self)
           end
@@ -240,6 +250,13 @@ module ActionDispatch
         def upgrade_legacy_signed_cookies?
           request.secret_token.present? && request.secret_key_base.present?
         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?
+        end
     end
 
     # Passing the ActiveSupport::MessageEncryptor::NullSerializer downstream
@@ -576,9 +593,11 @@ module ActionDispatch
             "Read the upgrade documentation to learn more about this new config option."
         end
 
-        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 || "")
-        @encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
+        cipher = "aes-256-gcm"
+        key_len = ActiveSupport::MessageEncryptor.key_len(cipher)
+        secret = key_generator.generate_key(request.authenticated_encrypted_cookie_salt || "")[0, key_len]
+
+        @encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
       end
 
       private
@@ -603,6 +622,32 @@ module ActionDispatch
       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 || "")
+
+        @legacy_encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, 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)
+        end
+    end
+
     def initialize(app)
       @app = app
     end
diff --git a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
index 1c720c5a8e..336a775880 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
@@ -10,7 +10,7 @@ module ActionDispatch
   # This middleware is responsible for logging exceptions and
   # showing a debugging page in case the request is local.
   class DebugExceptions
-    RESCUES_TEMPLATE_PATH = File.expand_path("../templates", __FILE__)
+    RESCUES_TEMPLATE_PATH = File.expand_path("templates", __dir__)
 
     class DebugView < ActionView::Base
       def debug_params(params)
diff --git a/actionpack/lib/action_dispatch/railtie.rb b/actionpack/lib/action_dispatch/railtie.rb
index 16a18a7f25..7662e164b8 100644
--- a/actionpack/lib/action_dispatch/railtie.rb
+++ b/actionpack/lib/action_dispatch/railtie.rb
@@ -16,6 +16,7 @@ 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.use_authenticated_cookie_encryption = false
     config.action_dispatch.perform_deep_munge = true
 
     config.action_dispatch.default_headers = {
@@ -36,6 +37,8 @@ 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/request/session.rb b/actionpack/lib/action_dispatch/request/session.rb
index 74ba6466cf..3547a8604f 100644
--- a/actionpack/lib/action_dispatch/request/session.rb
+++ b/actionpack/lib/action_dispatch/request/session.rb
@@ -101,11 +101,13 @@ module ActionDispatch
 
       # Returns keys of the session as Array.
       def keys
+        load_for_read!
         @delegate.keys
       end
 
       # Returns values of the session as Array.
       def values
+        load_for_read!
         @delegate.values
       end
 
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb
index 187ba2cc5f..f03f0d4299 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb
@@ -2,7 +2,12 @@ module ActionDispatch
   module SystemTesting
     module TestHelpers
       module SetupAndTeardown # :nodoc:
-        DEFAULT_HOST = "127.0.0.1"
+        DEFAULT_HOST = "http://127.0.0.1"
+
+        def host!(host)
+          super
+          Capybara.app_host = host
+        end
 
         def before_setup
           host! DEFAULT_HOST
diff --git a/actionpack/test/abstract_unit.rb b/actionpack/test/abstract_unit.rb
index 4185ce1a1f..bd118b46be 100644
--- a/actionpack/test/abstract_unit.rb
+++ b/actionpack/test/abstract_unit.rb
@@ -1,6 +1,6 @@
-$:.unshift(File.dirname(__FILE__) + "/lib")
-$:.unshift(File.dirname(__FILE__) + "/fixtures/helpers")
-$:.unshift(File.dirname(__FILE__) + "/fixtures/alternate_helpers")
+$:.unshift File.expand_path("lib", __dir__)
+$:.unshift File.expand_path("fixtures/helpers", __dir__)
+$:.unshift File.expand_path("fixtures/alternate_helpers", __dir__)
 
 require "active_support/core_ext/kernel/reporting"
 
@@ -56,7 +56,7 @@ ActiveSupport::Deprecation.debug = true
 # Disable available locale checks to avoid warnings running the test suite.
 I18n.enforce_available_locales = false
 
-FIXTURE_LOAD_PATH = File.join(File.dirname(__FILE__), "fixtures")
+FIXTURE_LOAD_PATH = File.join(__dir__, "fixtures")
 
 SharedTestRoutes = ActionDispatch::Routing::RouteSet.new
 
@@ -156,7 +156,7 @@ class ActionDispatch::IntegrationTest < ActiveSupport::TestCase
   end
 
   def with_autoload_path(path)
-    path = File.join(File.dirname(__FILE__), "fixtures", path)
+    path = File.join(__dir__, "fixtures", path)
     if ActiveSupport::Dependencies.autoload_paths.include?(path)
       yield
     else
diff --git a/actionpack/test/controller/action_pack_assertions_test.rb b/actionpack/test/controller/action_pack_assertions_test.rb
index 9ab152fc5c..73aab5848b 100644
--- a/actionpack/test/controller/action_pack_assertions_test.rb
+++ b/actionpack/test/controller/action_pack_assertions_test.rb
@@ -83,7 +83,7 @@ class ActionPackAssertionsController < ActionController::Base
   end
 
   def render_file_absolute_path
-    render file: File.expand_path("../../../README.rdoc", __FILE__)
+    render file: File.expand_path("../../README.rdoc", __dir__)
   end
 
   def render_file_relative_path
diff --git a/actionpack/test/controller/api/data_streaming_test.rb b/actionpack/test/controller/api/data_streaming_test.rb
index f15b78d102..e6419b9adf 100644
--- a/actionpack/test/controller/api/data_streaming_test.rb
+++ b/actionpack/test/controller/api/data_streaming_test.rb
@@ -1,7 +1,7 @@
 require "abstract_unit"
 
 module TestApiFileUtils
-  def file_path() File.expand_path(__FILE__) end
+  def file_path() __FILE__ end
   def file_data() @data ||= File.open(file_path, "rb") { |f| f.read } end
 end
 
diff --git a/actionpack/test/controller/caching_test.rb b/actionpack/test/controller/caching_test.rb
index fa8d9dc09a..c86dcafee5 100644
--- a/actionpack/test/controller/caching_test.rb
+++ b/actionpack/test/controller/caching_test.rb
@@ -4,7 +4,7 @@ require "lib/controller/fake_models"
 
 CACHE_DIR = "test_cache"
 # Don't change '/../temp/' cavalierly or you might hose something you don't want hosed
-FILE_STORE_PATH = File.join(File.dirname(__FILE__), "/../temp/", CACHE_DIR)
+FILE_STORE_PATH = File.join(__dir__, "../temp/", CACHE_DIR)
 
 class FragmentCachingMetalTestController < ActionController::Metal
   abstract!
@@ -26,10 +26,6 @@ class FragmentCachingMetalTest < ActionController::TestCase
     @controller.request = @request
     @controller.response = @response
   end
-
-  def test_fragment_cache_key
-    assert_equal "views/what a key", @controller.fragment_cache_key("what a key")
-  end
 end
 
 class CachingController < ActionController::Base
@@ -43,6 +39,8 @@ class FragmentCachingTestController < CachingController
 end
 
 class FragmentCachingTest < ActionController::TestCase
+  ModelWithKeyAndVersion = Struct.new(:cache_key, :cache_version)
+
   def setup
     super
     @store = ActiveSupport::Cache::MemoryStore.new
@@ -53,12 +51,25 @@ class FragmentCachingTest < ActionController::TestCase
     @controller.params = @params
     @controller.request = @request
     @controller.response = @response
+
+    @m1v1 = ModelWithKeyAndVersion.new("model/1", "1")
+    @m1v2 = ModelWithKeyAndVersion.new("model/1", "2")
+    @m2v1 = ModelWithKeyAndVersion.new("model/2", "1")
+    @m2v2 = ModelWithKeyAndVersion.new("model/2", "2")
   end
 
   def test_fragment_cache_key
-    assert_equal "views/what a key", @controller.fragment_cache_key("what a key")
-    assert_equal "views/test.host/fragment_caching_test/some_action",
-                  @controller.fragment_cache_key(controller: "fragment_caching_test", action: "some_action")
+    assert_deprecated do
+      assert_equal "views/what a key", @controller.fragment_cache_key("what a key")
+      assert_equal "views/test.host/fragment_caching_test/some_action",
+        @controller.fragment_cache_key(controller: "fragment_caching_test", action: "some_action")
+    end
+  end
+
+  def test_combined_fragment_cache_key
+    assert_equal [ :views, "what a key" ], @controller.combined_fragment_cache_key("what a key")
+    assert_equal [ :views, "test.host/fragment_caching_test/some_action" ],
+      @controller.combined_fragment_cache_key(controller: "fragment_caching_test", action: "some_action")
   end
 
   def test_read_fragment_with_caching_enabled
@@ -72,6 +83,12 @@ class FragmentCachingTest < ActionController::TestCase
     assert_nil @controller.read_fragment("name")
   end
 
+  def test_read_fragment_with_versioned_model
+    @controller.write_fragment([ "stuff", @m1v1 ], "hello")
+    assert_equal "hello", @controller.read_fragment([ "stuff", @m1v1 ])
+    assert_nil @controller.read_fragment([ "stuff", @m1v2 ])
+  end
+
   def test_fragment_exist_with_caching_enabled
     @store.write("views/name", "value")
     assert @controller.fragment_exist?("name")
@@ -198,7 +215,7 @@ CACHED
     assert_equal expected_body, @response.body
 
     assert_equal "This bit's fragment cached",
-      @store.read("views/test.host/functional_caching/fragment_cached/#{template_digest("functional_caching/fragment_cached")}")
+      @store.read("views/functional_caching/fragment_cached:#{template_digest("functional_caching/fragment_cached")}/fragment")
   end
 
   def test_fragment_caching_in_partials
@@ -207,7 +224,7 @@ CACHED
     assert_match(/Old fragment caching in a partial/, @response.body)
 
     assert_match("Old fragment caching in a partial",
-      @store.read("views/test.host/functional_caching/html_fragment_cached_with_partial/#{template_digest("functional_caching/_partial")}"))
+      @store.read("views/functional_caching/_partial:#{template_digest("functional_caching/_partial")}/test.host/functional_caching/html_fragment_cached_with_partial"))
   end
 
   def test_skipping_fragment_cache_digesting
@@ -237,7 +254,7 @@ CACHED
     assert_match(/Some inline content/, @response.body)
     assert_match(/Some cached content/, @response.body)
     assert_match("Some cached content",
-      @store.read("views/test.host/functional_caching/inline_fragment_cached/#{template_digest("functional_caching/inline_fragment_cached")}"))
+      @store.read("views/functional_caching/inline_fragment_cached:#{template_digest("functional_caching/inline_fragment_cached")}/test.host/functional_caching/inline_fragment_cached"))
   end
 
   def test_fragment_cache_instrumentation
@@ -264,7 +281,7 @@ CACHED
     assert_equal expected_body, @response.body
 
     assert_equal "<p>ERB</p>",
-      @store.read("views/test.host/functional_caching/formatted_fragment_cached/#{template_digest("functional_caching/formatted_fragment_cached")}")
+      @store.read("views/functional_caching/formatted_fragment_cached:#{template_digest("functional_caching/formatted_fragment_cached")}/fragment")
   end
 
   def test_xml_formatted_fragment_caching
@@ -275,7 +292,7 @@ CACHED
     assert_equal expected_body, @response.body
 
     assert_equal "  <p>Builder</p>\n",
-      @store.read("views/test.host/functional_caching/formatted_fragment_cached/#{template_digest("functional_caching/formatted_fragment_cached")}")
+      @store.read("views/functional_caching/formatted_fragment_cached:#{template_digest("functional_caching/formatted_fragment_cached")}/fragment")
   end
 
   def test_fragment_caching_with_variant
@@ -286,7 +303,7 @@ CACHED
     assert_equal expected_body, @response.body
 
     assert_equal "<p>PHONE</p>",
-      @store.read("views/test.host/functional_caching/formatted_fragment_cached_with_variant/#{template_digest("functional_caching/formatted_fragment_cached_with_variant")}")
+      @store.read("views/functional_caching/formatted_fragment_cached_with_variant:#{template_digest("functional_caching/formatted_fragment_cached_with_variant")}/fragment")
   end
 
   private
@@ -412,7 +429,7 @@ class CollectionCacheTest < ActionController::TestCase
   def test_collection_fetches_cached_views
     get :index
     assert_equal 1, @controller.partial_rendered_times
-    assert_customer_cached "david/1", "david, 1"
+    assert_match "david, 1", ActionView::PartialRenderer.collection_cache.read("views/customers/_customer:7c228ab609f0baf0b1f2367469210937/david/1")
 
     get :index
     assert_equal 1, @controller.partial_rendered_times
@@ -444,14 +461,8 @@ class CollectionCacheTest < ActionController::TestCase
 
   def test_caching_with_callable_cache_key
     get :index_with_callable_cache_key
-    assert_customer_cached "cached_david", "david, 1"
+    assert_match "david, 1", ActionView::PartialRenderer.collection_cache.read("views/customers/_customer:7c228ab609f0baf0b1f2367469210937/cached_david")
   end
-
-  private
-    def assert_customer_cached(key, content)
-      assert_match content,
-        ActionView::PartialRenderer.collection_cache.read("views/#{key}/7c228ab609f0baf0b1f2367469210937")
-    end
 end
 
 class FragmentCacheKeyTestController < CachingController
@@ -470,11 +481,21 @@ class FragmentCacheKeyTest < ActionController::TestCase
     @controller.cache_store = @store
   end
 
-  def test_fragment_cache_key
+  def test_combined_fragment_cache_key
     @controller.account_id = "123"
-    assert_equal "views/v1/123/what a key", @controller.fragment_cache_key("what a key")
+    assert_equal [ :views, "v1", "123", "what a key" ], @controller.combined_fragment_cache_key("what a key")
 
     @controller.account_id = nil
-    assert_equal "views/v1//what a key", @controller.fragment_cache_key("what a key")
+    assert_equal [ :views, "v1", "what a key" ], @controller.combined_fragment_cache_key("what a key")
+  end
+
+  def test_combined_fragment_cache_key_with_envs
+    ENV["RAILS_APP_VERSION"] = "55"
+    assert_equal [ :views, "55", "v1", "what a key" ], @controller.combined_fragment_cache_key("what a key")
+
+    ENV["RAILS_CACHE_ID"] = "66"
+    assert_equal [ :views, "66", "v1", "what a key" ], @controller.combined_fragment_cache_key("what a key")
+  ensure
+    ENV["RAILS_CACHE_ID"] = ENV["RAILS_APP_VERSION"] = nil
   end
 end
diff --git a/actionpack/test/controller/helper_test.rb b/actionpack/test/controller/helper_test.rb
index 4c6a772062..03dbd63614 100644
--- a/actionpack/test/controller/helper_test.rb
+++ b/actionpack/test/controller/helper_test.rb
@@ -1,6 +1,6 @@
 require "abstract_unit"
 
-ActionController::Base.helpers_path = File.expand_path("../../fixtures/helpers", __FILE__)
+ActionController::Base.helpers_path = File.expand_path("../fixtures/helpers", __dir__)
 
 module Fun
   class GamesController < ActionController::Base
@@ -48,7 +48,7 @@ end
 
 class HelpersPathsController < ActionController::Base
   paths = ["helpers2_pack", "helpers1_pack"].map do |path|
-    File.join(File.expand_path("../../fixtures", __FILE__), path)
+    File.join(File.expand_path("../fixtures", __dir__), path)
   end
   $:.unshift(*paths)
 
@@ -61,7 +61,7 @@ class HelpersPathsController < ActionController::Base
 end
 
 class HelpersTypoController < ActionController::Base
-  path = File.expand_path("../../fixtures/helpers_typo", __FILE__)
+  path = File.expand_path("../fixtures/helpers_typo", __dir__)
   $:.unshift(path)
   self.helpers_path = path
 end
@@ -178,7 +178,7 @@ class HelperTest < ActiveSupport::TestCase
   end
 
   def test_all_helpers_with_alternate_helper_dir
-    @controller_class.helpers_path = File.expand_path("../../fixtures/alternate_helpers", __FILE__)
+    @controller_class.helpers_path = File.expand_path("../fixtures/alternate_helpers", __dir__)
 
     # Reload helpers
     @controller_class._helpers = Module.new
diff --git a/actionpack/test/controller/integration_test.rb b/actionpack/test/controller/integration_test.rb
index 57f58fd835..72163ccd5e 100644
--- a/actionpack/test/controller/integration_test.rb
+++ b/actionpack/test/controller/integration_test.rb
@@ -1091,7 +1091,7 @@ class IntegrationFileUploadTest < ActionDispatch::IntegrationTest
   end
 
   def self.fixture_path
-    File.dirname(__FILE__) + "/../fixtures/multipart"
+    File.expand_path("../fixtures/multipart", __dir__)
   end
 
   routes.draw do
diff --git a/actionpack/test/controller/live_stream_test.rb b/actionpack/test/controller/live_stream_test.rb
index 581081dd07..bfb47b90d5 100644
--- a/actionpack/test/controller/live_stream_test.rb
+++ b/actionpack/test/controller/live_stream_test.rb
@@ -152,7 +152,7 @@ module ActionController
       end
 
       def write_sleep_autoload
-        path = File.join(File.dirname(__FILE__), "../fixtures")
+        path = File.expand_path("../fixtures", __dir__)
         ActiveSupport::Dependencies.autoload_paths << path
 
         response.headers["Content-Type"] = "text/event-stream"
diff --git a/actionpack/test/controller/mime/accept_format_test.rb b/actionpack/test/controller/mime/accept_format_test.rb
index a22fa39051..d1c4dbfef7 100644
--- a/actionpack/test/controller/mime/accept_format_test.rb
+++ b/actionpack/test/controller/mime/accept_format_test.rb
@@ -29,7 +29,7 @@ class StarStarMimeControllerTest < ActionController::TestCase
 end
 
 class AbstractPostController < ActionController::Base
-  self.view_paths = File.dirname(__FILE__) + "/../../fixtures/post_test/"
+  self.view_paths = File.expand_path("../../fixtures/post_test", __dir__)
 end
 
 # For testing layouts which are set automatically
diff --git a/actionpack/test/controller/new_base/render_file_test.rb b/actionpack/test/controller/new_base/render_file_test.rb
index 6d651e0104..4491dd96ed 100644
--- a/actionpack/test/controller/new_base/render_file_test.rb
+++ b/actionpack/test/controller/new_base/render_file_test.rb
@@ -2,15 +2,15 @@ require "abstract_unit"
 
 module RenderFile
   class BasicController < ActionController::Base
-    self.view_paths = File.dirname(__FILE__)
+    self.view_paths = __dir__
 
     def index
-      render file: File.join(File.dirname(__FILE__), *%w[.. .. fixtures test hello_world])
+      render file: File.expand_path("../../fixtures/test/hello_world", __dir__)
     end
 
     def with_instance_variables
       @secret = "in the sauce"
-      render file: File.join(File.dirname(__FILE__), "../../fixtures/test/render_file_with_ivar")
+      render file: File.expand_path("../../fixtures/test/render_file_with_ivar", __dir__)
     end
 
     def relative_path
@@ -25,11 +25,11 @@ module RenderFile
 
     def pathname
       @secret = "in the sauce"
-      render file: Pathname.new(File.dirname(__FILE__)).join(*%w[.. .. fixtures test dot.directory render_file_with_ivar])
+      render file: Pathname.new(__dir__).join(*%w[.. .. fixtures test dot.directory render_file_with_ivar])
     end
 
     def with_locals
-      path = File.join(File.dirname(__FILE__), "../../fixtures/test/render_file_with_locals")
+      path = File.expand_path("../../fixtures/test/render_file_with_locals", __dir__)
       render file: path, locals: { secret: "in the sauce" }
     end
   end
diff --git a/actionpack/test/controller/new_base/render_implicit_action_test.rb b/actionpack/test/controller/new_base/render_implicit_action_test.rb
index 796283466a..c5fc8e15e1 100644
--- a/actionpack/test/controller/new_base/render_implicit_action_test.rb
+++ b/actionpack/test/controller/new_base/render_implicit_action_test.rb
@@ -6,7 +6,7 @@ module RenderImplicitAction
       "render_implicit_action/simple/hello_world.html.erb"     => "Hello world!",
       "render_implicit_action/simple/hyphen-ated.html.erb"     => "Hello hyphen-ated!",
       "render_implicit_action/simple/not_implemented.html.erb" => "Not Implemented"
-    ), ActionView::FileSystemResolver.new(File.expand_path("../../../controller", __FILE__))]
+    ), ActionView::FileSystemResolver.new(File.expand_path("../../controller", __dir__))]
 
     def hello_world() end
   end
diff --git a/actionpack/test/controller/parameters/mutators_test.rb b/actionpack/test/controller/parameters/mutators_test.rb
index e61bbdbe13..2c36f488c6 100644
--- a/actionpack/test/controller/parameters/mutators_test.rb
+++ b/actionpack/test/controller/parameters/mutators_test.rb
@@ -25,6 +25,27 @@ class ParametersMutatorsTest < ActiveSupport::TestCase
     assert_not @params.delete(:person).permitted?
   end
 
+  test "delete returns the value when the key is present" do
+    assert_equal "32", @params[:person].delete(:age)
+  end
+
+  test "delete removes the entry when the key present" do
+    @params[:person].delete(:age)
+    assert_not @params[:person].key?(:age)
+  end
+
+  test "delete returns nil when the key is not present" do
+    assert_equal nil, @params[:person].delete(:first_name)
+  end
+
+  test "delete returns the value of the given block when the key is not present" do
+    assert_equal "David", @params[:person].delete(:first_name) { "David" }
+  end
+
+  test "delete yields the key to the given block when the key is not present" do
+    assert_equal "first_name: David", @params[:person].delete(:first_name) { |k| "#{k}: David" }
+  end
+
   test "delete_if retains permitted status" do
     @params.permit!
     assert @params.delete_if { |k| k == "person" }.permitted?
diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index 3a0a0a8bde..17d834d55f 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -257,7 +257,7 @@ end
 module TemplateModificationHelper
   private
     def modify_template(name)
-      path = File.expand_path("../../fixtures/#{name}.erb", __FILE__)
+      path = File.expand_path("../fixtures/#{name}.erb", __dir__)
       original = File.read(path)
       File.write(path, "#{original} Modified!")
       ActionView::LookupContext::DetailsKey.clear
@@ -287,9 +287,9 @@ class ExpiresInRenderTest < ActionController::TestCase
 
   def test_dynamic_render_with_file
     # This is extremely bad, but should be possible to do.
-    assert File.exist?(File.join(File.dirname(__FILE__), "../../test/abstract_unit.rb"))
+    assert File.exist?(File.expand_path("../../test/abstract_unit.rb", __dir__))
     response = get :dynamic_render_with_file, params: { id: '../\\../test/abstract_unit.rb' }
-    assert_equal File.read(File.join(File.dirname(__FILE__), "../../test/abstract_unit.rb")),
+    assert_equal File.read(File.expand_path("../../test/abstract_unit.rb", __dir__)),
       response.body
   end
 
@@ -306,16 +306,16 @@ class ExpiresInRenderTest < ActionController::TestCase
   end
 
   def test_dynamic_render
-    assert File.exist?(File.join(File.dirname(__FILE__), "../../test/abstract_unit.rb"))
+    assert File.exist?(File.expand_path("../../test/abstract_unit.rb", __dir__))
     assert_raises ActionView::MissingTemplate do
       get :dynamic_render, params: { id: '../\\../test/abstract_unit.rb' }
     end
   end
 
   def test_permitted_dynamic_render_file_hash
-    assert File.exist?(File.join(File.dirname(__FILE__), "../../test/abstract_unit.rb"))
+    assert File.exist?(File.expand_path("../../test/abstract_unit.rb", __dir__))
     response = get :dynamic_render_permit, params: { id: { file: '../\\../test/abstract_unit.rb' } }
-    assert_equal File.read(File.join(File.dirname(__FILE__), "../../test/abstract_unit.rb")),
+    assert_equal File.read(File.expand_path("../../test/abstract_unit.rb", __dir__)),
       response.body
   end
 
diff --git a/actionpack/test/controller/send_file_test.rb b/actionpack/test/controller/send_file_test.rb
index 9e6b975fe2..e265c6c49c 100644
--- a/actionpack/test/controller/send_file_test.rb
+++ b/actionpack/test/controller/send_file_test.rb
@@ -2,7 +2,7 @@ require "abstract_unit"
 
 module TestFileUtils
   def file_name() File.basename(__FILE__) end
-  def file_path() File.expand_path(__FILE__) end
+  def file_path() __FILE__ end
   def file_data() @data ||= File.open(file_path, "rb") { |f| f.read } end
 end
 
diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index 3a4307b64b..677e2ddded 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -122,7 +122,7 @@ XML
     end
 
     def test_send_file
-      send_file(File.expand_path(__FILE__))
+      send_file(__FILE__)
     end
 
     def redirect_to_same_controller
@@ -780,7 +780,7 @@ XML
     end
   end
 
-  FILES_DIR = File.dirname(__FILE__) + "/../fixtures/multipart"
+  FILES_DIR = File.expand_path("../fixtures/multipart", __dir__)
 
   READ_BINARY = "rb:binary"
   READ_PLAIN = "r:binary"
@@ -855,7 +855,7 @@ XML
   end
 
   def test_fixture_file_upload_ignores_fixture_path_given_full_path
-    TestCaseTest.stub :fixture_path, File.dirname(__FILE__) do
+    TestCaseTest.stub :fixture_path, __dir__ do
       uploaded_file = fixture_file_upload("#{FILES_DIR}/ruby_on_rails.jpg", "image/jpg")
       assert_equal File.open("#{FILES_DIR}/ruby_on_rails.jpg", READ_PLAIN).read, uploaded_file.read
     end
diff --git a/actionpack/test/dispatch/cookies_test.rb b/actionpack/test/dispatch/cookies_test.rb
index 664faa31bb..e5646de82e 100644
--- a/actionpack/test/dispatch/cookies_test.rb
+++ b/actionpack/test/dispatch/cookies_test.rb
@@ -288,8 +288,7 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.key_generator"] = ActiveSupport::KeyGenerator.new(SALT, iterations: 2)
 
     @request.env["action_dispatch.signed_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
+      @request.env["action_dispatch.authenticated_encrypted_cookie_salt"] = SALT
 
     @request.host = "www.nextangle.com"
   end
@@ -531,9 +530,7 @@ class CookiesTest < ActionController::TestCase
     get :set_encrypted_cookie
     cookies = @controller.send :cookies
     assert_not_equal "bar", cookies[:foo]
-    assert_raise TypeError do
-      cookies.signed[:foo]
-    end
+    assert_nil cookies.signed[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
   end
 
@@ -542,9 +539,7 @@ class CookiesTest < ActionController::TestCase
     get :set_encrypted_cookie
     cookies = @controller.send :cookies
     assert_not_equal "bar", cookies[:foo]
-    assert_raises TypeError do
-      cookies.signed[:foo]
-    end
+    assert_nil cookies.signed[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
   end
 
@@ -553,9 +548,7 @@ class CookiesTest < ActionController::TestCase
     get :set_encrypted_cookie
     cookies = @controller.send :cookies
     assert_not_equal "bar", cookies[:foo]
-    assert_raises ::JSON::ParserError do
-      cookies.signed[:foo]
-    end
+    assert_nil cookies.signed[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
   end
 
@@ -564,9 +557,7 @@ class CookiesTest < ActionController::TestCase
     get :set_wrapped_encrypted_cookie
     cookies = @controller.send :cookies
     assert_not_equal "wrapped: bar", cookies[:foo]
-    assert_raises ::JSON::ParserError do
-      cookies.signed[:foo]
-    end
+    assert_nil cookies.signed[:foo]
     assert_equal "wrapped: bar", cookies.encrypted[:foo]
   end
 
@@ -577,38 +568,16 @@ class CookiesTest < ActionController::TestCase
     assert_equal "bar was dumped and loaded", cookies.encrypted[:foo]
   end
 
-  def test_encrypted_cookie_using_custom_digest
-    @request.env["action_dispatch.cookies_digest"] = "SHA256"
-    get :set_encrypted_cookie
-    cookies = @controller.send :cookies
-    assert_not_equal "bar", cookies[:foo]
-    assert_equal "bar", cookies.encrypted[:foo]
-
-    sign_secret = @request.env["action_dispatch.key_generator"].generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-
-    sha1_verifier   = ActiveSupport::MessageVerifier.new(sign_secret, serializer: ActiveSupport::MessageEncryptor::NullSerializer, digest: "SHA1")
-    sha256_verifier = ActiveSupport::MessageVerifier.new(sign_secret, serializer: ActiveSupport::MessageEncryptor::NullSerializer, digest: "SHA256")
-
-    assert_raises(ActiveSupport::MessageVerifier::InvalidSignature) do
-      sha1_verifier.verify(cookies[:foo])
-    end
-
-    assert_nothing_raised do
-      sha256_verifier.verify(cookies[:foo])
-    end
-  end
-
   def test_encrypted_cookie_using_hybrid_serializer_can_migrate_marshal_dumped_value_to_json
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
-    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)
-    sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
+    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)
 
-    marshal_value = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: Marshal).encrypt_and_sign("bar")
-    @request.headers["Cookie"] = "foo=#{marshal_value}"
+    marshal_value = encryptor.encrypt_and_sign("bar")
+    @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape marshal_value}"
 
     get :get_encrypted_cookie
 
@@ -616,40 +585,28 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON)
-    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+    json_encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    assert_not_nil @response.cookies["foo"]
+    assert_equal "bar", json_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_encrypted_cookie_using_hybrid_serializer_can_read_from_json_dumped_value
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
-    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)
-    sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
-    json_value = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON).encrypt_and_sign("bar")
-    @request.headers["Cookie"] = "foo=#{json_value}"
-
-    get :get_encrypted_cookie
+    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)
 
-    cookies = @controller.send :cookies
-    assert_not_equal "bar", cookies[:foo]
-    assert_equal "bar", cookies.encrypted[:foo]
-
-    assert_nil @response.cookies["foo"]
-  end
-
-  def test_compat_encrypted_cookie_using_64_byte_key
-    # Cookie generated with 64 bytes secret
-    message = ["566d4e75536d686e633246564e6b493062557079626c566d51574d30515430394c53315665564a694e4563786555744f57537454576b396a5a31566a626e52525054303d2d2d34663234333330623130623261306163363562316266323335396164666364613564643134623131"].pack("H*")
-    @request.headers["Cookie"] = "foo=#{message}"
+    json_value = encryptor.encrypt_and_sign("bar")
+    @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape json_value}"
 
     get :get_encrypted_cookie
 
     cookies = @controller.send :cookies
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
+
     assert_nil @response.cookies["foo"]
   end
 
@@ -813,10 +770,10 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    key_generator = @request.env["action_dispatch.key_generator"]
-    secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
-    sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret)
+    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)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
@@ -842,8 +799,6 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :json
     @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", serializer: JSON).generate("bar")
 
@@ -852,10 +807,10 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    key_generator = @request.env["action_dispatch.key_generator"]
-    secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
-    sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON)
+    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)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
@@ -881,8 +836,6 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @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", serializer: JSON).generate("bar")
 
@@ -891,10 +844,10 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    key_generator = @request.env["action_dispatch.key_generator"]
-    secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
-    sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON)
+    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)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
@@ -920,8 +873,6 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @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")
 
@@ -930,10 +881,10 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    key_generator = @request.env["action_dispatch.key_generator"]
-    secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
-    sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON)
+    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)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
@@ -959,6 +910,89 @@ 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"
+
+    @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)
+    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")
+
+    @request.headers["Cookie"] = "foo=#{marshal_value}"
+
+    get :get_encrypted_cookie
+
+    cookies = @controller.send :cookies
+    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)
+
+    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)
+    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")
+
+    @request.headers["Cookie"] = "foo=#{marshal_value}"
+
+    get :get_encrypted_cookie
+
+    cookies = @controller.send :cookies
+    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)
+
+    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
+
+    # Cookie generated with 64 bytes secret
+    message = ["566d4e75536d686e633246564e6b493062557079626c566d51574d30515430394c53315665564a694e4563786555744f57537454576b396a5a31566a626e52525054303d2d2d34663234333330623130623261306163363562316266323335396164666364613564643134623131"].pack("H*")
+    @request.headers["Cookie"] = "foo=#{message}"
+
+    get :get_encrypted_cookie
+
+    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)
+
+    assert_equal "bar", 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/request/multipart_params_parsing_test.rb b/actionpack/test/dispatch/request/multipart_params_parsing_test.rb
index 01c5ff1429..e7e8c82974 100644
--- a/actionpack/test/dispatch/request/multipart_params_parsing_test.rb
+++ b/actionpack/test/dispatch/request/multipart_params_parsing_test.rb
@@ -21,7 +21,7 @@ class MultipartParamsParsingTest < ActionDispatch::IntegrationTest
     end
   end
 
-  FIXTURE_PATH = File.dirname(__FILE__) + "/../../fixtures/multipart"
+  FIXTURE_PATH = File.expand_path("../../fixtures/multipart", __dir__)
 
   def teardown
     TestController.last_request_parameters = nil
diff --git a/actionpack/test/dispatch/request/session_test.rb b/actionpack/test/dispatch/request/session_test.rb
index 311b80ea0a..228135c547 100644
--- a/actionpack/test/dispatch/request/session_test.rb
+++ b/actionpack/test/dispatch/request/session_test.rb
@@ -54,6 +54,11 @@ module ActionDispatch
         assert_equal %w[rails adequate], s.keys
       end
 
+      def test_keys_with_deferred_loading
+        s = Session.create(store_with_data, req, {})
+        assert_equal %w[sample_key], s.keys
+      end
+
       def test_values
         s = Session.create(store, req, {})
         s["rails"] = "ftw"
@@ -61,6 +66,11 @@ module ActionDispatch
         assert_equal %w[ftw awesome], s.values
       end
 
+      def test_values_with_deferred_loading
+        s = Session.create(store_with_data, req, {})
+        assert_equal %w[sample_value], s.values
+      end
+
       def test_clear
         s = Session.create(store, req, {})
         s["rails"] = "ftw"
@@ -113,6 +123,14 @@ module ActionDispatch
             def delete_session(env, id, options); 123; end
           }.new
         end
+
+        def store_with_data
+          Class.new {
+            def load_session(env); [1, { "sample_key" => "sample_value" }]; end
+            def session_exists?(env); true; end
+            def delete_session(env, id, options); 123; end
+          }.new
+        end
     end
 
     class SessionIntegrationTest < ActionDispatch::IntegrationTest
diff --git a/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb b/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
index 1169bf0cdb..6721a388c1 100644
--- a/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
+++ b/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
@@ -107,7 +107,7 @@ class UrlEncodedParamsParsingTest < ActionDispatch::IntegrationTest
     query = [
       "customers[boston][first][name]=David",
       "something_else=blah",
-      "logo=#{File.expand_path(__FILE__)}"
+      "logo=#{__FILE__}"
     ].join("&")
     expected = {
       "customers" => {
@@ -118,7 +118,7 @@ class UrlEncodedParamsParsingTest < ActionDispatch::IntegrationTest
         }
       },
       "something_else" => "blah",
-      "logo" => File.expand_path(__FILE__),
+      "logo" => __FILE__,
     }
     assert_parses expected, query
   end
diff --git a/actionpack/test/dispatch/request_test.rb b/actionpack/test/dispatch/request_test.rb
index 2f9228a62d..28cbde028d 100644
--- a/actionpack/test/dispatch/request_test.rb
+++ b/actionpack/test/dispatch/request_test.rb
@@ -110,8 +110,8 @@ class RequestIP < BaseRequestTest
       request.remote_ip
     }
     assert_match(/IP spoofing attack/, e.message)
-    assert_match(/HTTP_X_FORWARDED_FOR="1.1.1.1"/, e.message)
-    assert_match(/HTTP_CLIENT_IP="2.2.2.2"/, e.message)
+    assert_match(/HTTP_X_FORWARDED_FOR="1\.1\.1\.1"/, e.message)
+    assert_match(/HTTP_CLIENT_IP="2\.2\.2\.2"/, e.message)
   end
 
   test "remote ip with spoof detection disabled" do
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index d64917e0d3..32cd78e492 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -4419,7 +4419,7 @@ class TestInvalidUrls < ActionDispatch::IntegrationTest
     end
   end
 
-  test "invalid UTF-8 encoding returns a 400 Bad Request" do
+  test "invalid UTF-8 encoding is treated as ASCII 8BIT encode" do
     with_routing do |set|
       set.draw do
         get "/bar/:id", to: redirect("/foo/show/%{id}")
@@ -4435,19 +4435,19 @@ class TestInvalidUrls < ActionDispatch::IntegrationTest
       end
 
       get "/%E2%EF%BF%BD%A6"
-      assert_response :bad_request
+      assert_response :not_found
 
       get "/foo/%E2%EF%BF%BD%A6"
-      assert_response :bad_request
+      assert_response :not_found
 
       get "/foo/show/%E2%EF%BF%BD%A6"
-      assert_response :bad_request
+      assert_response :ok
 
       get "/bar/%E2%EF%BF%BD%A6"
-      assert_response :bad_request
+      assert_response :redirect
 
       get "/foobar/%E2%EF%BF%BD%A6"
-      assert_response :bad_request
+      assert_response :ok
     end
   end
 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 33d98f924f..8f90e45f5f 100644
--- a/actionpack/test/dispatch/system_testing/system_test_case_test.rb
+++ b/actionpack/test/dispatch/system_testing/system_test_case_test.rb
@@ -19,3 +19,15 @@ class SetDriverToSeleniumTest < DrivenBySeleniumWithChrome
     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
+  end
+
+  test "overrides host" do
+    host! "http://example.com"
+
+    assert_equal "http://example.com", Capybara.app_host
+  end
+end
diff --git a/actionpack/test/dispatch/uploaded_file_test.rb b/actionpack/test/dispatch/uploaded_file_test.rb
index 51680216e4..0074d2a314 100644
--- a/actionpack/test/dispatch/uploaded_file_test.rb
+++ b/actionpack/test/dispatch/uploaded_file_test.rb
@@ -13,6 +13,12 @@ module ActionDispatch
       assert_equal "foo", uf.original_filename
     end
 
+    def test_filename_is_different_object
+      file_str = "foo"
+      uf = Http::UploadedFile.new(filename: file_str, tempfile: Object.new)
+      assert_not_equal file_str.object_id , uf.original_filename.object_id
+    end
+
     def test_filename_should_be_in_utf_8
       uf = Http::UploadedFile.new(filename: "foo", tempfile: Object.new)
       assert_equal "UTF-8", uf.original_filename.encoding.to_s
diff --git a/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.html.erb b/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.html.erb
index 9b88fa1f5a..dfcd423978 100644
--- a/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.html.erb
+++ b/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.html.erb
@@ -1,3 +1,3 @@
 <body>
-<%= cache do %><p>ERB</p><% end %>
+<%= cache("fragment") do %><p>ERB</p><% end %>
 </body>
diff --git a/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.xml.builder b/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.xml.builder
index efdcc28e0f..6599579740 100644
--- a/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.xml.builder
+++ b/actionpack/test/fixtures/functional_caching/formatted_fragment_cached.xml.builder
@@ -1,5 +1,5 @@
 xml.body do
-  cache do
+  cache("fragment") do
     xml.p "Builder"
   end
 end
diff --git a/actionpack/test/fixtures/functional_caching/formatted_fragment_cached_with_variant.html+phone.erb b/actionpack/test/fixtures/functional_caching/formatted_fragment_cached_with_variant.html+phone.erb
index e523b74ae3..abf7017ce6 100644
--- a/actionpack/test/fixtures/functional_caching/formatted_fragment_cached_with_variant.html+phone.erb
+++ b/actionpack/test/fixtures/functional_caching/formatted_fragment_cached_with_variant.html+phone.erb
@@ -1,3 +1,3 @@
 <body>
-<%= cache do %><p>PHONE</p><% end %>
+<%= cache("fragment") do %><p>PHONE</p><% end %>
 </body>
diff --git a/actionpack/test/fixtures/functional_caching/fragment_cached.html.erb b/actionpack/test/fixtures/functional_caching/fragment_cached.html.erb
index fa5e6bd318..1148d83ad7 100644
--- a/actionpack/test/fixtures/functional_caching/fragment_cached.html.erb
+++ b/actionpack/test/fixtures/functional_caching/fragment_cached.html.erb
@@ -1,3 +1,3 @@
 Hello
-<%= cache do %>This bit's fragment cached<% end %>
+<%= cache "fragment" do %>This bit's fragment cached<% end %>
 <%= 'Ciao' %>
diff --git a/actionpack/test/journey/gtg/transition_table_test.rb b/actionpack/test/journey/gtg/transition_table_test.rb
index c7315c0338..889640fdd7 100644
--- a/actionpack/test/journey/gtg/transition_table_test.rb
+++ b/actionpack/test/journey/gtg/transition_table_test.rb
@@ -35,25 +35,25 @@ module ActionDispatch
 
         def test_simulate_gt
           sim = simulator_for ["/foo", "/bar"]
-          assert_match sim, "/foo"
+          assert_match_route sim, "/foo"
         end
 
         def test_simulate_gt_regexp
           sim = simulator_for [":foo"]
-          assert_match sim, "foo"
+          assert_match_route sim, "foo"
         end
 
         def test_simulate_gt_regexp_mix
           sim = simulator_for ["/get", "/:method/foo"]
-          assert_match sim, "/get"
-          assert_match sim, "/get/foo"
+          assert_match_route sim, "/get"
+          assert_match_route sim, "/get/foo"
         end
 
         def test_simulate_optional
           sim = simulator_for ["/foo(/bar)"]
-          assert_match sim, "/foo"
-          assert_match sim, "/foo/bar"
-          assert_no_match sim, "/foo/"
+          assert_match_route sim, "/foo"
+          assert_match_route sim, "/foo/bar"
+          assert_no_match_route sim, "/foo/"
         end
 
         def test_match_data
@@ -65,11 +65,11 @@ module ActionDispatch
 
           sim = GTG::Simulator.new tt
 
-          match = sim.match "/get"
-          assert_equal [paths.first], match.memos
+          memos = sim.memos "/get"
+          assert_equal [paths.first], memos
 
-          match = sim.match "/get/foo"
-          assert_equal [paths.last], match.memos
+          memos = sim.memos "/get/foo"
+          assert_equal [paths.last], memos
         end
 
         def test_match_data_ambiguous
@@ -86,8 +86,8 @@ module ActionDispatch
           builder = GTG::Builder.new ast
           sim     = GTG::Simulator.new builder.transition_table
 
-          match = sim.match "/articles/new"
-          assert_equal [paths[1], paths[3]], match.memos
+          memos = sim.memos "/articles/new"
+          assert_equal [paths[1], paths[3]], memos
         end
 
         private
@@ -109,6 +109,14 @@ module ActionDispatch
           def simulator_for(paths)
             GTG::Simulator.new tt(paths)
           end
+
+          def assert_match_route(simulator, path)
+            assert simulator.memos(path), "Simulator should match #{path}."
+          end
+
+          def assert_no_match_route(simulator, path)
+            assert_not simulator.memos(path) { nil }, "Simulator should not match #{path}."
+          end
       end
     end
   end
diff --git a/actionpack/test/journey/router/utils_test.rb b/actionpack/test/journey/router/utils_test.rb
index b77bf6628a..74277a4325 100644
--- a/actionpack/test/journey/router/utils_test.rb
+++ b/actionpack/test/journey/router/utils_test.rb
@@ -31,6 +31,11 @@ module ActionDispatch
         def test_normalize_path_uppercase
           assert_equal "/foo%AAbar%AAbaz", Utils.normalize_path("/foo%aabar%aabaz")
         end
+
+        def test_normalize_path_maintains_string_encoding
+          path = "/foo%AAbar%AAbaz".b
+          assert_equal Encoding::ASCII_8BIT, Utils.normalize_path(path).encoding
+        end
       end
     end
   end
diff --git a/actionpack/test/lib/controller/fake_models.rb b/actionpack/test/lib/controller/fake_models.rb
index b768553e7a..ff37d85ed8 100644
--- a/actionpack/test/lib/controller/fake_models.rb
+++ b/actionpack/test/lib/controller/fake_models.rb
@@ -26,6 +26,10 @@ Customer = Struct.new(:name, :id) do
   def persisted?
     id.present?
   end
+
+  def cache_key
+    "#{name}/#{id}"
+  end
 end
 
 Post = Struct.new(:title, :author_name, :body, :secret, :persisted, :written_on, :cost) do
diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index c514e757c8..122c42c5bd 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1 +1,11 @@
+*   Add `:json` type to `auto_discovery_link_tag` to support [JSON Feeds](https://jsonfeed.org/version/1)
+
+    *Mike Gunderloy*
+
+*   Update `distance_of_time_in_words` helper to display better error messages
+    for bad input.
+
+    *Jay Hayes*
+
+
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionview/CHANGELOG.md) for previous changes.
diff --git a/actionview/Rakefile b/actionview/Rakefile
index de588ad25c..0fc38e8db4 100644
--- a/actionview/Rakefile
+++ b/actionview/Rakefile
@@ -2,8 +2,6 @@ require "rake/testtask"
 require "fileutils"
 require "open3"
 
-dir = File.dirname(__FILE__)
-
 desc "Default Task"
 task default: :test
 
@@ -95,7 +93,7 @@ namespace :assets do
   desc "Verify compiled Action View assets"
   task :verify do
     file = "lib/assets/compiled/rails-ujs.js"
-    pathname = Pathname.new("#{dir}/#{file}")
+    pathname = Pathname.new("#{__dir__}/#{file}")
 
     print "[verify] #{file} exists "
     if pathname.exist?
@@ -113,13 +111,13 @@ namespace :assets do
       fail
     end
 
-    print "[verify] #{dir} can be required as a module "
+    print "[verify] #{__dir__} can be required as a module "
     js = <<-JS
       window = { Event: class {} }
       class Element {}
-      require('#{dir}')
+      require('#{__dir__}')
     JS
-    stdout, stderr, status = Open3.capture3("node", "--print", js)
+    _, stderr, status = Open3.capture3("node", "--print", js)
     if status.success?
       puts "[OK]"
     else
@@ -130,7 +128,7 @@ namespace :assets do
 end
 
 task :lines do
-  load File.expand_path("..", File.dirname(__FILE__)) + "/tools/line_statistics"
+  load File.join(File.expand_path("..", __dir__), "/tools/line_statistics")
   files = FileList["lib/**/*.rb"]
   CodeTools::LineStatistics.new(files).print_loc
 end
diff --git a/actionview/actionview.gemspec b/actionview/actionview.gemspec
index cfaa5007a1..41221dd04e 100644
--- a/actionview/actionview.gemspec
+++ b/actionview/actionview.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/actionview/app/assets/javascripts/README.md b/actionview/app/assets/javascripts/README.md
index 92f3e8a3b3..0819d5da5f 100644
--- a/actionview/app/assets/javascripts/README.md
+++ b/actionview/app/assets/javascripts/README.md
@@ -36,10 +36,20 @@ Require `rails-ujs` into your application.js manifest.
 //= require rails-ujs
 ```
 
+Usage with yarn
+------------
+
+When using with Webpacker gem or your preferred JavaScript bundler. Just add the following to your main JS file and compile.
+
+```javascript
+import Rails from 'rails-ujs';
+Rails.start()
+```
+
 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.
+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).
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
index 26df7b9a3f..a653d3af3d 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
@@ -14,7 +14,7 @@ AcceptHeaders =
 Rails.ajax = (options) ->
   options = prepareOptions(options)
   xhr = createXHR options, ->
-    response = processResponse(xhr.response, xhr.getResponseHeader('Content-Type'))
+    response = processResponse(xhr.response ? xhr.responseText, xhr.getResponseHeader('Content-Type'))
     if xhr.status // 100 == 2
       options.success?(response, xhr.statusText, xhr)
     else
diff --git a/actionview/lib/action_view.rb b/actionview/lib/action_view.rb
index ca586f1d52..99c5b831b5 100644
--- a/actionview/lib/action_view.rb
+++ b/actionview/lib/action_view.rb
@@ -92,5 +92,5 @@ end
 require "active_support/core_ext/string/output_safety"
 
 ActiveSupport.on_load(:i18n) do
-  I18n.load_path << "#{File.dirname(__FILE__)}/action_view/locale/en.yml"
+  I18n.load_path << File.expand_path("action_view/locale/en.yml", __dir__)
 end
diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index 750f96f29e..c21fe782c6 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -122,9 +122,9 @@ module ActionView
       end
 
       # Returns a link tag that browsers and feed readers can use to auto-detect
-      # an RSS or Atom feed. The +type+ can either be <tt>:rss</tt> (default) or
-      # <tt>:atom</tt>. Control the link options in url_for format using the
-      # +url_options+. You can modify the LINK tag itself in +tag_options+.
+      # an RSS, Atom, or JSON feed. The +type+ can be <tt>:rss</tt> (default),
+      # <tt>:atom</tt>, or <tt>:json</tt>. Control the link options in url_for format
+      # using the +url_options+. You can modify the LINK tag itself in +tag_options+.
       #
       # ==== Options
       #
@@ -138,6 +138,8 @@ module ActionView
       #   # => <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/action" />
       #   auto_discovery_link_tag(:atom)
       #   # => <link rel="alternate" type="application/atom+xml" title="ATOM" href="http://www.currenthost.com/controller/action" />
+      #   auto_discovery_link_tag(:json)
+      #   # => <link rel="alternate" type="application/json" title="JSON" href="http://www.currenthost.com/controller/action" />
       #   auto_discovery_link_tag(:rss, {action: "feed"})
       #   # => <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/feed" />
       #   auto_discovery_link_tag(:rss, {action: "feed"}, {title: "My RSS"})
@@ -147,8 +149,8 @@ module ActionView
       #   auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {title: "Example RSS"})
       #   # => <link rel="alternate" type="application/rss+xml" title="Example RSS" href="http://www.example.com/feed.rss" />
       def auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {})
-        if !(type == :rss || type == :atom) && tag_options[:type].blank?
-          raise ArgumentError.new("You should pass :type tag_option key explicitly, because you have passed #{type} type other than :rss or :atom.")
+        if !(type == :rss || type == :atom || type == :json) && tag_options[:type].blank?
+          raise ArgumentError.new("You should pass :type tag_option key explicitly, because you have passed #{type} type other than :rss, :atom, or :json.")
         end
 
         tag(
diff --git a/actionview/lib/action_view/helpers/cache_helper.rb b/actionview/lib/action_view/helpers/cache_helper.rb
index 15ab7e304f..c3aecadcd6 100644
--- a/actionview/lib/action_view/helpers/cache_helper.rb
+++ b/actionview/lib/action_view/helpers/cache_helper.rb
@@ -8,10 +8,9 @@ module ActionView
       # fragments, and so on. This method takes a block that contains
       # the content you wish to cache.
       #
-      # The best way to use this is by doing key-based cache expiration
-      # on top of a cache store like Memcached that'll automatically
-      # kick out old entries. For more on key-based expiration, see:
-      # http://signalvnoise.com/posts/3113-how-key-based-cache-expiration-works
+      # The best way to use this is by doing recyclable key-based cache expiration
+      # on top of a cache store like Memcached or Redis that'll automatically
+      # kick out old entries.
       #
       # When using this method, you list the cache dependency as the name of the cache, like so:
       #
@@ -23,10 +22,14 @@ module ActionView
       # This approach will assume that when a new topic is added, you'll touch
       # the project. The cache key generated from this call will be something like:
       #
-      #   views/projects/123-20120806214154/7a1156131a6928cb0026877f8b749ac9
-      #         ^class   ^id ^updated_at    ^template tree digest
+      #   views/template/action.html.erb:7a1156131a6928cb0026877f8b749ac9/projects/123
+      #         ^template path           ^template tree digest            ^class   ^id
       #
-      # The cache is thus automatically bumped whenever the project updated_at is touched.
+      # This cache key is stable, but it's combined with a cache version derived from the project
+      # record. When the project updated_at is touched, the #cache_version changes, even
+      # if the key stays stable. This means that unlike a traditional key-based cache expiration
+      # approach, you won't be generating cache trash, unused keys, simply because the dependent
+      # record is updated.
       #
       # If your template cache depends on multiple sources (try to avoid this to keep things simple),
       # you can name all these dependencies as part of an array:
@@ -217,10 +220,15 @@ module ActionView
 
       def fragment_name_with_digest(name, virtual_path)
         virtual_path ||= @virtual_path
+
         if virtual_path
           name = controller.url_for(name).split("://").last if name.is_a?(Hash)
-          digest = Digestor.digest name: virtual_path, finder: lookup_context, dependencies: view_cache_dependencies
-          [ name, digest ]
+
+          if digest = Digestor.digest(name: virtual_path, finder: lookup_context, dependencies: view_cache_dependencies).presence
+            [ "#{virtual_path}:#{digest}", name ]
+          else
+            [ virtual_path, name ]
+          end
         else
           name
         end
diff --git a/actionview/lib/action_view/helpers/date_helper.rb b/actionview/lib/action_view/helpers/date_helper.rb
index 09dc6ef6bd..3f43465aa4 100644
--- a/actionview/lib/action_view/helpers/date_helper.rb
+++ b/actionview/lib/action_view/helpers/date_helper.rb
@@ -95,8 +95,8 @@ module ActionView
           scope: :'datetime.distance_in_words'
         }.merge!(options)
 
-        from_time = from_time.to_time if from_time.respond_to?(:to_time)
-        to_time = to_time.to_time if to_time.respond_to?(:to_time)
+        from_time = normalize_distance_of_time_argument_to_time(from_time)
+        to_time = normalize_distance_of_time_argument_to_time(to_time)
         from_time, to_time = to_time, from_time if from_time > to_time
         distance_in_minutes = ((to_time - from_time) / 60.0).round
         distance_in_seconds = (to_time - from_time).round
@@ -130,22 +130,18 @@ module ActionView
             # 60 days up to 365 days
           when 86400...525600   then locale.t :x_months,       count: (distance_in_minutes.to_f / 43200.0).round
             else
-            if from_time.acts_like?(:time) && to_time.acts_like?(:time)
-              fyear = from_time.year
-              fyear += 1 if from_time.month >= 3
-              tyear = to_time.year
-              tyear -= 1 if to_time.month < 3
-              leap_years = (fyear > tyear) ? 0 : (fyear..tyear).count { |x| Date.leap?(x) }
-              minute_offset_for_leap_year = leap_years * 1440
-              # Discount the leap year days when calculating year distance.
-              # e.g. if there are 20 leap year days between 2 dates having the same day
-              # and month then the based on 365 days calculation
-              # the distance in years will come out to over 80 years when in written
-              # English it would read better as about 80 years.
-              minutes_with_offset = distance_in_minutes - minute_offset_for_leap_year
-            else
-              minutes_with_offset = distance_in_minutes
-            end
+            from_year = from_time.year
+            from_year += 1 if from_time.month >= 3
+            to_year = to_time.year
+            to_year -= 1 if to_time.month < 3
+            leap_years = (from_year > to_year) ? 0 : (from_year..to_year).count { |x| Date.leap?(x) }
+            minute_offset_for_leap_year = leap_years * 1440
+            # Discount the leap year days when calculating year distance.
+            # e.g. if there are 20 leap year days between 2 dates having the same day
+            # and month then the based on 365 days calculation
+            # the distance in years will come out to over 80 years when in written
+            # English it would read better as about 80 years.
+            minutes_with_offset = distance_in_minutes - minute_offset_for_leap_year
             remainder                   = (minutes_with_offset % MINUTES_IN_YEAR)
             distance_in_years           = (minutes_with_offset.div MINUTES_IN_YEAR)
             if remainder < MINUTES_IN_QUARTER_YEAR
@@ -687,6 +683,18 @@ module ActionView
 
         content_tag("time".freeze, content, options.reverse_merge(datetime: datetime), &block)
       end
+
+      private
+
+        def normalize_distance_of_time_argument_to_time(value)
+          if value.is_a?(Numeric)
+            Time.at(value)
+          elsif value.respond_to?(:to_time)
+            value.to_time
+          else
+            raise ArgumentError, "#{value.inspect} can't be converted to a Time value"
+          end
+        end
     end
 
     class DateTimeSelector #:nodoc:
diff --git a/actionview/lib/action_view/helpers/form_helper.rb b/actionview/lib/action_view/helpers/form_helper.rb
index 3eafe0028e..672269b811 100644
--- a/actionview/lib/action_view/helpers/form_helper.rb
+++ b/actionview/lib/action_view/helpers/form_helper.rb
@@ -1606,14 +1606,15 @@ module ActionView
       include ModelNaming
 
       # The methods which wrap a form helper call.
-      class_attribute :field_helpers
-      self.field_helpers = [:fields_for, :fields, :label, :text_field, :password_field,
-                            :hidden_field, :file_field, :text_area, :check_box,
-                            :radio_button, :color_field, :search_field,
-                            :telephone_field, :phone_field, :date_field,
-                            :time_field, :datetime_field, :datetime_local_field,
-                            :month_field, :week_field, :url_field, :email_field,
-                            :number_field, :range_field]
+      class_attribute :field_helpers, default: [
+        :fields_for, :fields, :label, :text_field, :password_field,
+        :hidden_field, :file_field, :text_area, :check_box,
+        :radio_button, :color_field, :search_field,
+        :telephone_field, :phone_field, :date_field,
+        :time_field, :datetime_field, :datetime_local_field,
+        :month_field, :week_field, :url_field, :email_field,
+        :number_field, :range_field
+      ]
 
       attr_accessor :object_name, :object, :options
 
diff --git a/actionview/lib/action_view/helpers/tags/base.rb b/actionview/lib/action_view/helpers/tags/base.rb
index 0895533a60..aa420c4b66 100644
--- a/actionview/lib/action_view/helpers/tags/base.rb
+++ b/actionview/lib/action_view/helpers/tags/base.rb
@@ -149,7 +149,7 @@ module ActionView
             end
 
             value = options.fetch(:selected) { value(object) }
-            select = content_tag("select", add_options(option_tags, options, value), html_options)
+            select = content_tag("select", add_options(option_tags, options, value), html_options.except!("skip_default_ids", "allow_method_names_outside_object"))
 
             if html_options["multiple"] && options.fetch(:include_hidden, true)
               tag("input", disabled: html_options["disabled"], name: html_options["name"], type: "hidden", value: "") + select
diff --git a/actionview/lib/action_view/helpers/tags/select.rb b/actionview/lib/action_view/helpers/tags/select.rb
index 667c7e945a..9ff7e54e4f 100644
--- a/actionview/lib/action_view/helpers/tags/select.rb
+++ b/actionview/lib/action_view/helpers/tags/select.rb
@@ -33,7 +33,7 @@ module ActionView
           #   [nil, []]
           #   { nil => [] }
           def grouped_choices?
-            !@choices.empty? && @choices.first.respond_to?(:last) && Array === @choices.first.last
+            !@choices.blank? && @choices.first.respond_to?(:last) && Array === @choices.first.last
           end
       end
     end
diff --git a/actionview/lib/action_view/layouts.rb b/actionview/lib/action_view/layouts.rb
index 81feb90486..ab8409e8d0 100644
--- a/actionview/lib/action_view/layouts.rb
+++ b/actionview/lib/action_view/layouts.rb
@@ -204,9 +204,9 @@ module ActionView
     include ActionView::Rendering
 
     included do
-      class_attribute :_layout, :_layout_conditions, instance_accessor: false
-      self._layout = nil
-      self._layout_conditions = {}
+      class_attribute :_layout, instance_accessor: false
+      class_attribute :_layout_conditions, instance_accessor: false, default: {}
+
       _write_layout_method
     end
 
diff --git a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
index 1fbe209200..847256ac78 100644
--- a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
@@ -38,7 +38,7 @@ module ActionView
       end
 
       def expanded_cache_key(key)
-        key = @view.fragment_cache_key(@view.cache_fragment_name(key, virtual_path: @template.virtual_path))
+        key = @view.combined_fragment_cache_key(@view.cache_fragment_name(key, virtual_path: @template.virtual_path))
         key.frozen? ? key.dup : key # #read_multi & #write may require mutability, Dalli 2.6.0.
       end
 
diff --git a/actionview/lib/action_view/template/handlers/builder.rb b/actionview/lib/action_view/template/handlers/builder.rb
index e99b921cb7..67ad78133d 100644
--- a/actionview/lib/action_view/template/handlers/builder.rb
+++ b/actionview/lib/action_view/template/handlers/builder.rb
@@ -1,9 +1,7 @@
 module ActionView
   module Template::Handlers
     class Builder
-      # Default format used by Builder.
-      class_attribute :default_format
-      self.default_format = :xml
+      class_attribute :default_format, default: :xml
 
       def call(template)
         require_engine
@@ -14,7 +12,6 @@ module ActionView
       end
 
       private
-
         def require_engine # :doc:
           @required ||= begin
             require "builder"
diff --git a/actionview/lib/action_view/template/handlers/erb.rb b/actionview/lib/action_view/template/handlers/erb.rb
index 58c7fd1a88..48c2e22a89 100644
--- a/actionview/lib/action_view/template/handlers/erb.rb
+++ b/actionview/lib/action_view/template/handlers/erb.rb
@@ -9,16 +9,13 @@ module ActionView
 
         # Specify trim mode for the ERB compiler. Defaults to '-'.
         # See ERB documentation for suitable values.
-        class_attribute :erb_trim_mode
-        self.erb_trim_mode = "-"
+        class_attribute :erb_trim_mode, default: "-"
 
         # Default implementation used.
-        class_attribute :erb_implementation
-        self.erb_implementation = Erubi
+        class_attribute :erb_implementation, default: Erubi
 
         # Do not escape templates of these mime types.
-        class_attribute :escape_whitelist
-        self.escape_whitelist = ["text/plain"]
+        class_attribute :escape_whitelist, default: ["text/plain"]
 
         ENCODING_TAG = Regexp.new("\\A(<%#{ENCODING_FLAG}-?%>)[ \\t]*")
 
diff --git a/actionview/lib/action_view/view_paths.rb b/actionview/lib/action_view/view_paths.rb
index f0fe6831fa..938f0fc17f 100644
--- a/actionview/lib/action_view/view_paths.rb
+++ b/actionview/lib/action_view/view_paths.rb
@@ -3,9 +3,7 @@ module ActionView
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_view_paths
-      self._view_paths = ActionView::PathSet.new
-      _view_paths.freeze
+      class_attribute :_view_paths, default: ActionView::PathSet.new.freeze
     end
 
     delegate :template_exists?, :any_templates?, :view_paths, :formats, :formats=,
diff --git a/actionview/test/abstract_unit.rb b/actionview/test/abstract_unit.rb
index dde66a7ba0..a7d706c5e1 100644
--- a/actionview/test/abstract_unit.rb
+++ b/actionview/test/abstract_unit.rb
@@ -1,8 +1,8 @@
-$:.unshift(File.dirname(__FILE__) + "/lib")
-$:.unshift(File.dirname(__FILE__) + "/fixtures/helpers")
-$:.unshift(File.dirname(__FILE__) + "/fixtures/alternate_helpers")
+$:.unshift File.expand_path("lib", __dir__)
+$:.unshift File.expand_path("fixtures/helpers", __dir__)
+$:.unshift File.expand_path("fixtures/alternate_helpers", __dir__)
 
-ENV["TMPDIR"] = File.join(File.dirname(__FILE__), "tmp")
+ENV["TMPDIR"] = File.expand_path("tmp", __dir__)
 
 require "active_support/core_ext/kernel/reporting"
 
@@ -47,7 +47,7 @@ I18n.backend.store_translations "da", {}
 I18n.backend.store_translations "pt-BR", {}
 ORIGINAL_LOCALES = I18n.available_locales.map(&:to_s).sort
 
-FIXTURE_LOAD_PATH = File.join(File.dirname(__FILE__), "fixtures")
+FIXTURE_LOAD_PATH = File.expand_path("fixtures", __dir__)
 
 module RenderERBUtils
   def view
@@ -133,7 +133,7 @@ class BasicController
   def config
     @config ||= ActiveSupport::InheritableOptions.new(ActionController::Base.config).tap do |config|
       # VIEW TODO: View tests should not require a controller
-      public_dir = File.expand_path("../fixtures/public", __FILE__)
+      public_dir = File.expand_path("fixtures/public", __dir__)
       config.assets_dir = public_dir
       config.javascripts_dir = "#{public_dir}/javascripts"
       config.stylesheets_dir = "#{public_dir}/stylesheets"
@@ -196,7 +196,7 @@ class ActionDispatch::IntegrationTest < ActiveSupport::TestCase
   end
 
   def with_autoload_path(path)
-    path = File.join(File.dirname(__FILE__), "fixtures", path)
+    path = File.join(File.expand_path("fixtures", __dir__), path)
     if ActiveSupport::Dependencies.autoload_paths.include?(path)
       yield
     else
diff --git a/actionview/test/actionpack/abstract/abstract_controller_test.rb b/actionview/test/actionpack/abstract/abstract_controller_test.rb
index a2cd3deb58..8f65a61493 100644
--- a/actionview/test/actionpack/abstract/abstract_controller_test.rb
+++ b/actionview/test/actionpack/abstract/abstract_controller_test.rb
@@ -42,7 +42,7 @@ module AbstractController
         super
       end
 
-      append_view_path File.expand_path(File.join(File.dirname(__FILE__), "views"))
+      append_view_path File.expand_path("views", __dir__)
     end
 
     class Me2 < RenderingController
@@ -152,7 +152,7 @@ module AbstractController
     class OverridingLocalPrefixes < AbstractController::Base
       include AbstractController::Rendering
       include ActionView::Rendering
-      append_view_path File.expand_path(File.join(File.dirname(__FILE__), "views"))
+      append_view_path File.expand_path("views", __dir__)
 
       def index
         render
diff --git a/actionview/test/actionpack/abstract/helper_test.rb b/actionview/test/actionpack/abstract/helper_test.rb
index 83237518d7..13922e4485 100644
--- a/actionview/test/actionpack/abstract/helper_test.rb
+++ b/actionview/test/actionpack/abstract/helper_test.rb
@@ -1,6 +1,6 @@
 require "abstract_unit"
 
-ActionController::Base.helpers_path = File.expand_path("../../../fixtures/helpers", __FILE__)
+ActionController::Base.helpers_path = File.expand_path("../../fixtures/helpers", __dir__)
 
 module AbstractController
   module Testing
@@ -51,7 +51,7 @@ module AbstractController
     class AbstractInvalidHelpers < AbstractHelpers
       include ActionController::Helpers
 
-      path = File.expand_path("../../../fixtures/helpers_missing", __FILE__)
+      path = File.expand_path("../../fixtures/helpers_missing", __dir__)
       $:.unshift(path)
       self.helpers_path = path
     end
diff --git a/actionview/test/actionpack/controller/capture_test.rb b/actionview/test/actionpack/controller/capture_test.rb
index f0ae609845..cc3a23c60c 100644
--- a/actionview/test/actionpack/controller/capture_test.rb
+++ b/actionview/test/actionpack/controller/capture_test.rb
@@ -2,7 +2,7 @@ require "abstract_unit"
 require "active_support/logger"
 
 class CaptureController < ActionController::Base
-  self.view_paths = [ File.dirname(__FILE__) + "/../../fixtures/actionpack" ]
+  self.view_paths = [ File.expand_path("../../fixtures/actionpack", __dir__) ]
 
   def self.controller_name; "test"; end
   def self.controller_path; "test"; end
diff --git a/actionview/test/actionpack/controller/layout_test.rb b/actionview/test/actionpack/controller/layout_test.rb
index b79835ff34..b3e0329f57 100644
--- a/actionview/test/actionpack/controller/layout_test.rb
+++ b/actionview/test/actionpack/controller/layout_test.rb
@@ -5,7 +5,7 @@ require "active_support/core_ext/array/extract_options"
 # method has access to the view_paths array when looking for a layout to automatically assign.
 old_load_paths = ActionController::Base.view_paths
 
-ActionController::Base.view_paths = [ File.dirname(__FILE__) + "/../../fixtures/actionpack/layout_tests/" ]
+ActionController::Base.view_paths = [ File.expand_path("../../fixtures/actionpack/layout_tests", __dir__) ]
 
 class LayoutTest < ActionController::Base
   def self.controller_path; "views" end
@@ -96,7 +96,7 @@ class StreamingLayoutController < LayoutTest
 end
 
 class AbsolutePathLayoutController < LayoutTest
-  layout File.expand_path(File.expand_path(__FILE__) + "/../../../fixtures/actionpack/layout_tests/layouts/layout_test")
+  layout File.expand_path("../../fixtures/actionpack/layout_tests/layouts/layout_test", __dir__)
 end
 
 class HasOwnLayoutController < LayoutTest
@@ -117,7 +117,7 @@ end
 
 class PrependsViewPathController < LayoutTest
   def hello
-    prepend_view_path File.dirname(__FILE__) + "/../../fixtures/actionpack/layout_tests/alt/"
+    prepend_view_path File.expand_path("../../fixtures/actionpack/layout_tests/alt", __dir__)
     render layout: "alt"
   end
 end
diff --git a/actionview/test/actionpack/controller/render_test.rb b/actionview/test/actionpack/controller/render_test.rb
index 51ec8899b1..6528169312 100644
--- a/actionview/test/actionpack/controller/render_test.rb
+++ b/actionview/test/actionpack/controller/render_test.rb
@@ -56,7 +56,7 @@ class TestController < ApplicationController
   end
 
   def hello_world_file
-    render file: File.expand_path("../../../fixtures/actionpack/hello", __FILE__), formats: [:html]
+    render file: File.expand_path("../../fixtures/actionpack/hello", __dir__), formats: [:html]
   end
 
   # :ported:
@@ -125,7 +125,7 @@ class TestController < ApplicationController
   # :ported:
   def render_file_with_instance_variables
     @secret = "in the sauce"
-    path = File.join(File.dirname(__FILE__), "../../fixtures/test/render_file_with_ivar")
+    path = File.expand_path("../../fixtures/test/render_file_with_ivar", __dir__)
     render file: path
   end
 
@@ -142,21 +142,21 @@ class TestController < ApplicationController
 
   def render_file_using_pathname
     @secret = "in the sauce"
-    render file: Pathname.new(File.dirname(__FILE__)).join("..", "..", "fixtures", "test", "dot.directory", "render_file_with_ivar")
+    render file: Pathname.new(__dir__).join("..", "..", "fixtures", "test", "dot.directory", "render_file_with_ivar")
   end
 
   def render_file_from_template
     @secret = "in the sauce"
-    @path = File.expand_path(File.join(File.dirname(__FILE__), "../../fixtures/test/render_file_with_ivar"))
+    @path = File.expand_path("../../fixtures/test/render_file_with_ivar", __dir__)
   end
 
   def render_file_with_locals
-    path = File.join(File.dirname(__FILE__), "../../fixtures/test/render_file_with_locals")
+    path = File.expand_path("../../fixtures/test/render_file_with_locals", __dir__)
     render file: path, locals: { secret: "in the sauce" }
   end
 
   def render_file_as_string_with_locals
-    path = File.expand_path(File.join(File.dirname(__FILE__), "../../fixtures/test/render_file_with_locals"))
+    path = File.expand_path("../../fixtures/test/render_file_with_locals", __dir__)
     render file: path, locals: { secret: "in the sauce" }
   end
 
diff --git a/actionview/test/active_record_unit.rb b/actionview/test/active_record_unit.rb
index 7f94b7ebb4..901c0e2b3e 100644
--- a/actionview/test/active_record_unit.rb
+++ b/actionview/test/active_record_unit.rb
@@ -13,7 +13,7 @@ end
 # Try to grab AR
 unless defined?(ActiveRecord) && defined?(FixtureSet)
   begin
-    PATH_TO_AR = "#{File.dirname(__FILE__)}/../../activerecord/lib"
+    PATH_TO_AR = File.expand_path("../../activerecord/lib", __dir__)
     raise LoadError, "#{PATH_TO_AR} doesn't exist" unless File.directory?(PATH_TO_AR)
     $LOAD_PATH.unshift PATH_TO_AR
     require "active_record"
@@ -58,13 +58,13 @@ class ActiveRecordTestConnector
 
       # Load actionpack sqlite3 tables
       def load_schema
-        File.read(File.dirname(__FILE__) + "/fixtures/db_definitions/sqlite.sql").split(";").each do |sql|
+        File.read(File.expand_path("fixtures/db_definitions/sqlite.sql", __dir__)).split(";").each do |sql|
           ActiveRecord::Base.connection.execute(sql) unless sql.blank?
         end
       end
 
       def require_fixture_models
-        Dir.glob(File.dirname(__FILE__) + "/fixtures/*.rb").each { |f| require f }
+        Dir.glob(File.expand_path("fixtures/*.rb", __dir__)).each { |f| require f }
       end
   end
 end
diff --git a/actionview/test/activerecord/controller_runtime_test.rb b/actionview/test/activerecord/controller_runtime_test.rb
index 590559f592..1cec5072c0 100644
--- a/actionview/test/activerecord/controller_runtime_test.rb
+++ b/actionview/test/activerecord/controller_runtime_test.rb
@@ -67,7 +67,7 @@ class ControllerRuntimeLogSubscriberTest < ActionController::TestCase
     wait
 
     assert_equal 2, @logger.logged(:info).size
-    assert_match(/\(Views: [\d.]+ms \| ActiveRecord: 0.0ms\)/, @logger.logged(:info)[1])
+    assert_match(/\(Views: [\d.]+ms \| ActiveRecord: 0\.0ms\)/, @logger.logged(:info)[1])
   end
 
   def test_log_with_active_record_when_post
diff --git a/actionview/test/activerecord/relation_cache_test.rb b/actionview/test/activerecord/relation_cache_test.rb
index 43f7242ee9..fbab512c41 100644
--- a/actionview/test/activerecord/relation_cache_test.rb
+++ b/actionview/test/activerecord/relation_cache_test.rb
@@ -10,7 +10,7 @@ class RelationCacheTest < ActionView::TestCase
 
   def test_cache_relation_other
     cache(Project.all) { concat("Hello World") }
-    assert_equal "Hello World", controller.cache_store.read("views/projects-#{Project.count}/")
+    assert_equal "Hello World", controller.cache_store.read("views/path/projects-#{Project.count}")
   end
 
   def view_cache_dependencies; end
diff --git a/actionview/test/fixtures/comments/empty.html+grid.erb b/actionview/test/fixtures/comments/empty.html+grid.erb
new file mode 100644
index 0000000000..dc3fa32a81
--- /dev/null
+++ b/actionview/test/fixtures/comments/empty.html+grid.erb
@@ -0,0 +1 @@
+<h1>No Comment</h1>
diff --git a/actionview/test/fixtures/test/_partial_with_variants.html+grid.erb b/actionview/test/fixtures/test/_partial_with_variants.html+grid.erb
new file mode 100644
index 0000000000..225363c8c3
--- /dev/null
+++ b/actionview/test/fixtures/test/_partial_with_variants.html+grid.erb
@@ -0,0 +1 @@
+<h1>Partial with variants</h1>
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 07a6452cc1..6093a4e660 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -53,6 +53,7 @@ class AssetTagHelperTest < ActionView::TestCase
     %(auto_discovery_link_tag) => %(<link href="http://www.example.com" rel="alternate" title="RSS" type="application/rss+xml" />),
     %(auto_discovery_link_tag(:rss)) => %(<link href="http://www.example.com" rel="alternate" title="RSS" type="application/rss+xml" />),
     %(auto_discovery_link_tag(:atom)) => %(<link href="http://www.example.com" rel="alternate" title="ATOM" type="application/atom+xml" />),
+    %(auto_discovery_link_tag(:json)) => %(<link href="http://www.example.com" rel="alternate" title="JSON" type="application/json" />),
     %(auto_discovery_link_tag(:rss, :action => "feed")) => %(<link href="http://www.example.com" rel="alternate" title="RSS" type="application/rss+xml" />),
     %(auto_discovery_link_tag(:rss, "http://localhost/feed")) => %(<link href="http://localhost/feed" rel="alternate" title="RSS" type="application/rss+xml" />),
     %(auto_discovery_link_tag(:rss, "//localhost/feed")) => %(<link href="//localhost/feed" rel="alternate" title="RSS" type="application/rss+xml" />),
@@ -709,13 +710,13 @@ class AssetTagHelperNonVhostTest < ActionView::TestCase
 
   def test_should_wildcard_asset_host
     @controller.config.asset_host = "http://a%d.example.com"
-    assert_match(%r(http://a[0123].example.com), compute_asset_host("foo"))
+    assert_match(%r(http://a[0123]\.example\.com), compute_asset_host("foo"))
   end
 
   def test_should_wildcard_asset_host_between_zero_and_four
     @controller.config.asset_host = "http://a%d.example.com"
-    assert_match(%r(http://a[0123].example.com/collaboration/hieraki/images/xml.png), image_path("xml.png"))
-    assert_match(%r(http://a[0123].example.com/collaboration/hieraki/images/xml.png), image_url("xml.png"))
+    assert_match(%r(http://a[0123]\.example\.com/collaboration/hieraki/images/xml\.png), image_path("xml.png"))
+    assert_match(%r(http://a[0123]\.example\.com/collaboration/hieraki/images/xml\.png), image_url("xml.png"))
   end
 
   def test_asset_host_without_protocol_should_be_protocol_relative
diff --git a/actionview/test/template/atom_feed_helper_test.rb b/actionview/test/template/atom_feed_helper_test.rb
index 1245a1a966..7304b769a4 100644
--- a/actionview/test/template/atom_feed_helper_test.rb
+++ b/actionview/test/template/atom_feed_helper_test.rb
@@ -301,8 +301,8 @@ class AtomFeedTest < ActionController::TestCase
     with_restful_routing(:scrolls) do
       get :index, params: { id: "feed_with_atomPub_namespace" }
       assert_match %r{xml:lang="en-US"}, @response.body
-      assert_match %r{xmlns="http://www.w3.org/2005/Atom"}, @response.body
-      assert_match %r{xmlns:app="http://www.w3.org/2007/app"}, @response.body
+      assert_match %r{xmlns="http://www\.w3\.org/2005/Atom"}, @response.body
+      assert_match %r{xmlns:app="http://www\.w3\.org/2007/app"}, @response.body
     end
   end
 
@@ -319,7 +319,7 @@ class AtomFeedTest < ActionController::TestCase
     with_restful_routing(:scrolls) do
       get :index, params: { id: "feed_with_xml_processing_instructions" }
       assert_match %r{<\?xml-stylesheet [^\?]*type="text/css"}, @response.body
-      assert_match %r{<\?xml-stylesheet [^\?]*href="t.css"}, @response.body
+      assert_match %r{<\?xml-stylesheet [^\?]*href="t\.css"}, @response.body
     end
   end
 
@@ -334,7 +334,7 @@ class AtomFeedTest < ActionController::TestCase
   def test_feed_xhtml
     with_restful_routing(:scrolls) do
       get :index, params: { id:  "feed_with_xhtml_content" }
-      assert_match %r{xmlns="http://www.w3.org/1999/xhtml"}, @response.body
+      assert_match %r{xmlns="http://www\.w3\.org/1999/xhtml"}, @response.body
       assert_select "summary", text: /Something Boring/
       assert_select "summary", text: /after 2/
     end
diff --git a/actionview/test/template/date_helper_test.rb b/actionview/test/template/date_helper_test.rb
index d257147e1f..a259752d6a 100644
--- a/actionview/test/template/date_helper_test.rb
+++ b/actionview/test/template/date_helper_test.rb
@@ -128,6 +128,16 @@ class DateHelperTest < ActionView::TestCase
     assert_distance_of_time_in_words(from)
   end
 
+  def test_distance_in_words_with_nil_input
+    assert_raises(ArgumentError) { distance_of_time_in_words(nil) }
+    assert_raises(ArgumentError) { distance_of_time_in_words(0, nil) }
+  end
+
+  def test_distance_in_words_with_mixed_argument_types
+    assert_equal "1 minute", distance_of_time_in_words(0, Time.at(60))
+    assert_equal "10 minutes", distance_of_time_in_words(Time.at(600), 0)
+  end
+
   def test_distance_in_words_with_mathn_required
     # test we avoid Integer#/ (redefined by mathn)
     silence_warnings { require "mathn" }
diff --git a/actionview/test/template/digestor_test.rb b/actionview/test/template/digestor_test.rb
index e225c3de09..de04f3f25d 100644
--- a/actionview/test/template/digestor_test.rb
+++ b/actionview/test/template/digestor_test.rb
@@ -14,7 +14,7 @@ class FixtureTemplate
 end
 
 class FixtureFinder < ActionView::LookupContext
-  FIXTURES_DIR = "#{File.dirname(__FILE__)}/../fixtures/digestor"
+  FIXTURES_DIR = File.expand_path("../fixtures/digestor", __dir__)
 
   def initialize(details = {})
     super(ActionView::PathSet.new(["digestor", "digestor/api"]), details, [])
diff --git a/actionview/test/template/form_helper/form_with_test.rb b/actionview/test/template/form_helper/form_with_test.rb
index a09dd468dd..bff0643fb0 100644
--- a/actionview/test/template/form_helper/form_with_test.rb
+++ b/actionview/test/template/form_helper/form_with_test.rb
@@ -302,6 +302,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       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")
       concat f.button("Create post")
       concat f.button {
@@ -315,6 +316,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       "<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>"
diff --git a/actionview/test/template/form_options_helper_test.rb b/actionview/test/template/form_options_helper_test.rb
index 258dcdb806..3247f20ba7 100644
--- a/actionview/test/template/form_options_helper_test.rb
+++ b/actionview/test/template/form_options_helper_test.rb
@@ -6,6 +6,15 @@ class Map < Hash
   end
 end
 
+class CustomEnumerable
+  include Enumerable
+
+  def each
+    yield "one"
+    yield "two"
+  end
+end
+
 class FormOptionsHelperTest < ActionView::TestCase
   tests ActionView::Helpers::FormOptionsHelper
 
@@ -904,6 +913,14 @@ class FormOptionsHelperTest < ActionView::TestCase
     )
   end
 
+  def test_select_with_enumerable
+    @post = Post.new
+    assert_dom_equal(
+      "<select id=\"post_category\" name=\"post[category]\"><option value=\"one\">one</option>\n<option value=\"two\">two</option></select>",
+      select("post", "category", CustomEnumerable.new)
+    )
+  end
+
   def test_collection_select
     @post = Post.new
     @post.author_name = "Babe"
diff --git a/actionview/test/template/log_subscriber_test.rb b/actionview/test/template/log_subscriber_test.rb
index 7f358add7e..584666d54b 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -39,7 +39,7 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
 
   def set_view_cache_dependencies
     def @view.view_cache_dependencies; []; end
-    def @view.fragment_cache_key(*); "ahoy `controller` dependency"; end
+    def @view.combined_fragment_cache_key(*); "ahoy `controller` dependency"; end
   end
 
   def test_render_file_template
diff --git a/actionview/test/template/render_test.rb b/actionview/test/template/render_test.rb
index 412948719c..9999607067 100644
--- a/actionview/test/template/render_test.rb
+++ b/actionview/test/template/render_test.rb
@@ -10,8 +10,8 @@ module RenderTestCases
     @view = Class.new(ActionView::Base) do
       def view_cache_dependencies; end
 
-      def fragment_cache_key(key)
-        ActiveSupport::Cache.expand_cache_key(key, :views)
+      def combined_fragment_cache_key(key)
+        [ :views, key ]
       end
     end.new(paths, @assigns)
 
@@ -27,7 +27,7 @@ module RenderTestCases
 
   def test_render_without_options
     e = assert_raises(ArgumentError) { @view.render() }
-    assert_match(/You invoked render but did not give any of (.+) option./, e.message)
+    assert_match(/You invoked render but did not give any of (.+) option\./, e.message)
   end
 
   def test_render_file
@@ -83,6 +83,10 @@ module RenderTestCases
     assert_equal "<h1>Kein Kommentar</h1>", @view.render(template: "comments/empty", locale: [:de])
   end
 
+  def test_render_template_with_variants
+    assert_equal "<h1>No Comment</h1>\n", @view.render(template: "comments/empty", variants: :grid)
+  end
+
   def test_render_file_with_handlers
     assert_equal "<h1>No Comment</h1>\n", @view.render(file: "comments/empty", handlers: [:builder])
     assert_equal "<h1>No Comment</h1>\n", @view.render(file: "comments/empty", handlers: :builder)
@@ -134,7 +138,7 @@ module RenderTestCases
   end
 
   def test_render_file_with_full_path
-    template_path = File.join(File.dirname(__FILE__), "../fixtures/test/hello_world")
+    template_path = File.expand_path("../fixtures/test/hello_world", __dir__)
     assert_equal "Hello world!", @view.render(file: template_path)
   end
 
@@ -156,7 +160,7 @@ module RenderTestCases
   end
 
   def test_render_outside_path
-    assert File.exist?(File.join(File.dirname(__FILE__), "../../test/abstract_unit.rb"))
+    assert File.exist?(File.expand_path("../../test/abstract_unit.rb", __dir__))
     assert_raises ActionView::MissingTemplate do
       @view.render(template: "../\\../test/abstract_unit.rb")
     end
@@ -170,6 +174,10 @@ module RenderTestCases
     assert_equal "partial html", @view.render(partial: "test/partial")
   end
 
+  def test_render_partial_with_variants
+    assert_equal "<h1>Partial with variants</h1>\n", @view.render(partial: "test/partial_with_variants", variants: :grid)
+  end
+
   def test_render_partial_with_selected_format
     assert_equal "partial html", @view.render(partial: "test/partial", formats: :html)
     assert_equal "partial js", @view.render(partial: "test/partial", formats: [:js])
@@ -253,7 +261,7 @@ module RenderTestCases
   def test_render_sub_template_with_errors
     e = assert_raises(ActionView::Template::Error) { @view.render(template: "test/sub_template_raise") }
     assert_match %r!method.*doesnt_exist!, e.message
-    assert_match %r{Trace of template inclusion: .*test/sub_template_raise.html.erb}, e.sub_template_message
+    assert_match %r{Trace of template inclusion: .*test/sub_template_raise\.html\.erb}, e.sub_template_message
     assert_equal "1", e.line_number
     assert_equal File.expand_path("#{FIXTURE_LOAD_PATH}/test/_raise.html.erb"), e.file_name
   end
@@ -710,6 +718,6 @@ class CachedCollectionViewRenderTest < ActiveSupport::TestCase
   private
     def cache_key(*names, virtual_path)
       digest = ActionView::Digestor.digest name: virtual_path, finder: @view.lookup_context, dependencies: []
-      @view.fragment_cache_key([ *names, digest ])
+      @view.combined_fragment_cache_key([ "#{virtual_path}:#{digest}", *names ])
     end
 end
diff --git a/actionview/test/template/resolver_patterns_test.rb b/actionview/test/template/resolver_patterns_test.rb
index 43e3f21076..8e21f4b828 100644
--- a/actionview/test/template/resolver_patterns_test.rb
+++ b/actionview/test/template/resolver_patterns_test.rb
@@ -2,7 +2,7 @@ require "abstract_unit"
 
 class ResolverPatternsTest < ActiveSupport::TestCase
   def setup
-    path = File.expand_path("../../fixtures/", __FILE__)
+    path = File.expand_path("../fixtures", __dir__)
     pattern = ":prefix/{:formats/,}:action{.:formats,}{+:variants,}{.:handlers,}"
     @resolver = ActionView::FileSystemResolver.new(path, pattern)
   end
diff --git a/actionview/test/template/url_helper_test.rb b/actionview/test/template/url_helper_test.rb
index 6adfa95dd1..58d903b1c8 100644
--- a/actionview/test/template/url_helper_test.rb
+++ b/actionview/test/template/url_helper_test.rb
@@ -615,8 +615,8 @@ class UrlHelperTest < ActiveSupport::TestCase
 
   def test_mail_to_with_special_characters
     assert_dom_equal(
-      %{<a href="mailto:%23%21%24%25%26%27%2A%2B-%2F%3D%3F%5E_%60%7B%7D%7C%7E@example.org">#!$%&amp;&#39;*+-/=?^_`{}|~@example.org</a>},
-      mail_to("#!$%&'*+-/=?^_`{}|~@example.org")
+      %{<a href="mailto:%23%21%24%25%26%27%2A%2B-%2F%3D%3F%5E_%60%7B%7D%7C@example.org">#!$%&amp;&#39;*+-/=?^_`{}|@example.org</a>},
+      mail_to("#!$%&'*+-/=?^_`{}|@example.org")
     )
   end
 
diff --git a/actionview/test/ujs/config.ru b/actionview/test/ujs/config.ru
index 48b7a4b53a..213a41127a 100644
--- a/actionview/test/ujs/config.ru
+++ b/actionview/test/ujs/config.ru
@@ -1,4 +1,4 @@
-$LOAD_PATH.unshift File.expand_path("..", __FILE__)
+$LOAD_PATH.unshift __dir__
 require "server"
 
 run UJS::Server
diff --git a/activejob/CHANGELOG.md b/activejob/CHANGELOG.md
index ddfb926e02..77dfdefc05 100644
--- a/activejob/CHANGELOG.md
+++ b/activejob/CHANGELOG.md
@@ -4,4 +4,5 @@
 
     *Steven Bull*
 
+
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activejob/CHANGELOG.md) for previous changes.
diff --git a/activejob/Rakefile b/activejob/Rakefile
index 41ff76135e..dd03ab0b8f 100644
--- a/activejob/Rakefile
+++ b/activejob/Rakefile
@@ -1,8 +1,7 @@
 require "rake/testtask"
 
 #TODO: add qu back to the list after it support Rails 5.1
-#TODO: add delayed_job back to the list after it support Rails 5.1
-ACTIVEJOB_ADAPTERS = %w(async inline que queue_classic resque sidekiq sneakers sucker_punch backburner test)
+ACTIVEJOB_ADAPTERS = %w(async inline delayed_job que queue_classic resque sidekiq sneakers sucker_punch backburner test)
 ACTIVEJOB_ADAPTERS.delete("queue_classic") if defined?(JRUBY_VERSION)
 
 task default: :test
@@ -44,9 +43,8 @@ namespace :test do
 
     namespace :isolated do
       task adapter => "test:env:#{adapter}" do
-        dir = File.dirname(__FILE__)
-        Dir.glob("#{dir}/test/cases/**/*_test.rb").all? do |file|
-          sh(Gem.ruby, "-w", "-I#{dir}/lib", "-I#{dir}/test", file)
+        Dir.glob("#{__dir__}/test/cases/**/*_test.rb").all? do |file|
+          sh(Gem.ruby, "-w", "-I#{__dir__}/lib", "-I#{__dir__}/test", file)
         end || raise("Failures")
       end
     end
diff --git a/activejob/activejob.gemspec b/activejob/activejob.gemspec
index 2547e91262..2f2b94a4c4 100644
--- a/activejob/activejob.gemspec
+++ b/activejob/activejob.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/activejob/lib/active_job/callbacks.rb b/activejob/lib/active_job/callbacks.rb
index d5b17de8b5..9aebc880a5 100644
--- a/activejob/lib/active_job/callbacks.rb
+++ b/activejob/lib/active_job/callbacks.rb
@@ -4,7 +4,7 @@ module ActiveJob
   # = Active Job Callbacks
   #
   # Active Job provides hooks during the life cycle of a job. Callbacks allow you
-  # to trigger logic during the life cycle of a job. Available callbacks are:
+  # to trigger logic during this cycle. Available callbacks are:
   #
   # * <tt>before_enqueue</tt>
   # * <tt>around_enqueue</tt>
@@ -13,6 +13,8 @@ module ActiveJob
   # * <tt>around_perform</tt>
   # * <tt>after_perform</tt>
   #
+  # NOTE: Calling the same callback multiple times will overwrite previous callback definitions.
+  #
   module Callbacks
     extend  ActiveSupport::Concern
     include ActiveSupport::Callbacks
diff --git a/activejob/lib/active_job/queue_adapter.rb b/activejob/lib/active_job/queue_adapter.rb
index 9dae80ffc2..b22d8b8347 100644
--- a/activejob/lib/active_job/queue_adapter.rb
+++ b/activejob/lib/active_job/queue_adapter.rb
@@ -7,6 +7,7 @@ module ActiveJob
     extend ActiveSupport::Concern
 
     included do
+      class_attribute :_queue_adapter_name, instance_accessor: false, instance_predicate: false
       class_attribute :_queue_adapter, instance_accessor: false, instance_predicate: false
       self.queue_adapter = :async
     end
@@ -19,11 +20,15 @@ module ActiveJob
         _queue_adapter
       end
 
+      def queue_adapter_name
+        _queue_adapter_name
+      end
+
       # Specify the backend queue provider. The default queue adapter
       # is the +:async+ queue. See QueueAdapters for more
       # information.
       def queue_adapter=(name_or_adapter_or_class)
-        self._queue_adapter = interpret_adapter(name_or_adapter_or_class)
+        interpret_adapter(name_or_adapter_or_class)
       end
 
       private
@@ -31,16 +36,24 @@ module ActiveJob
         def interpret_adapter(name_or_adapter_or_class)
           case name_or_adapter_or_class
           when Symbol, String
-            ActiveJob::QueueAdapters.lookup(name_or_adapter_or_class).new
+            assign_adapter(name_or_adapter_or_class.to_s,
+                           ActiveJob::QueueAdapters.lookup(name_or_adapter_or_class).new)
           else
             if queue_adapter?(name_or_adapter_or_class)
-              name_or_adapter_or_class
+              adapter_name = "#{name_or_adapter_or_class.class.name.demodulize.remove('Adapter').underscore}"
+              assign_adapter(adapter_name,
+                             name_or_adapter_or_class)
             else
               raise ArgumentError
             end
           end
         end
 
+        def assign_adapter(adapter_name, queue_adapter)
+          self._queue_adapter_name = adapter_name
+          self._queue_adapter = queue_adapter
+        end
+
         QUEUE_ADAPTER_METHODS = [:enqueue, :enqueue_at].freeze
 
         def queue_adapter?(object)
diff --git a/activejob/lib/active_job/queue_name.rb b/activejob/lib/active_job/queue_name.rb
index 352cf62424..d83113af60 100644
--- a/activejob/lib/active_job/queue_name.rb
+++ b/activejob/lib/active_job/queue_name.rb
@@ -32,11 +32,8 @@ module ActiveJob
     end
 
     included do
-      class_attribute :queue_name, instance_accessor: false
-      class_attribute :queue_name_delimiter, instance_accessor: false
-
-      self.queue_name = default_queue_name
-      self.queue_name_delimiter = "_" # set default delimiter to '_'
+      class_attribute :queue_name, instance_accessor: false, default: default_queue_name
+      class_attribute :queue_name_delimiter, instance_accessor: false, default: "_"
     end
 
     # Returns the name of the queue the job will be run on.
diff --git a/activejob/lib/active_job/queue_priority.rb b/activejob/lib/active_job/queue_priority.rb
index b02202fcc8..db8d9178a4 100644
--- a/activejob/lib/active_job/queue_priority.rb
+++ b/activejob/lib/active_job/queue_priority.rb
@@ -27,9 +27,7 @@ module ActiveJob
     end
 
     included do
-      class_attribute :priority, instance_accessor: false
-
-      self.priority = default_priority
+      class_attribute :priority, instance_accessor: false, default: default_priority
     end
 
     # Returns the priority that the job will be created with
diff --git a/activejob/lib/rails/generators/job/job_generator.rb b/activejob/lib/rails/generators/job/job_generator.rb
index 50476a2e50..474f181f65 100644
--- a/activejob/lib/rails/generators/job/job_generator.rb
+++ b/activejob/lib/rails/generators/job/job_generator.rb
@@ -12,7 +12,7 @@ module Rails # :nodoc:
       hook_for :test_framework
 
       def self.default_generator_root
-        File.dirname(__FILE__)
+        __dir__
       end
 
       def create_job_file
diff --git a/activejob/test/adapters/delayed_job.rb b/activejob/test/adapters/delayed_job.rb
index 5f0ee2418c..98e41c0c36 100644
--- a/activejob/test/adapters/delayed_job.rb
+++ b/activejob/test/adapters/delayed_job.rb
@@ -1,6 +1,6 @@
 ActiveJob::Base.queue_adapter = :delayed_job
 
-$LOAD_PATH << File.dirname(__FILE__) + "/../support/delayed_job"
+$LOAD_PATH << File.expand_path("../support/delayed_job", __dir__)
 
 Delayed::Worker.delay_jobs = false
 Delayed::Worker.backend    = :test
diff --git a/activejob/test/cases/queue_adapter_test.rb b/activejob/test/cases/queue_adapter_test.rb
index 9611b0909b..8368107bdf 100644
--- a/activejob/test/cases/queue_adapter_test.rb
+++ b/activejob/test/cases/queue_adapter_test.rb
@@ -25,14 +25,19 @@ class QueueAdapterTest < ActiveJob::TestCase
     base_queue_adapter = ActiveJob::Base.queue_adapter
 
     child_job_one = Class.new(ActiveJob::Base)
+    assert_equal child_job_one.queue_adapter_name, ActiveJob::Base.queue_adapter_name
+
     child_job_one.queue_adapter = :stub_one
 
     assert_not_equal ActiveJob::Base.queue_adapter, child_job_one.queue_adapter
+    assert_equal "stub_one", child_job_one.queue_adapter_name
     assert_kind_of ActiveJob::QueueAdapters::StubOneAdapter, child_job_one.queue_adapter
 
     child_job_two = Class.new(ActiveJob::Base)
     child_job_two.queue_adapter = :stub_two
 
+    assert_equal "stub_two", child_job_two.queue_adapter_name
+
     assert_kind_of ActiveJob::QueueAdapters::StubTwoAdapter, child_job_two.queue_adapter
     assert_kind_of ActiveJob::QueueAdapters::StubOneAdapter, child_job_one.queue_adapter, "child_job_one's queue adapter should remain unchanged"
     assert_equal base_queue_adapter, ActiveJob::Base.queue_adapter, "ActiveJob::Base's queue adapter should remain unchanged"
diff --git a/activejob/test/support/integration/dummy_app_template.rb b/activejob/test/support/integration/dummy_app_template.rb
index 29a5691f30..14fe3c9adc 100644
--- a/activejob/test/support/integration/dummy_app_template.rb
+++ b/activejob/test/support/integration/dummy_app_template.rb
@@ -5,7 +5,7 @@ end
 rails_command("db:migrate")
 
 initializer "activejob.rb", <<-CODE
-require "#{File.expand_path("../jobs_manager.rb",  __FILE__)}"
+require "#{File.expand_path("jobs_manager.rb",  __dir__)}"
 JobsManager.current_manager.setup
 CODE
 
diff --git a/activejob/test/support/integration/helper.rb b/activejob/test/support/integration/helper.rb
index 626b932cce..545b62752e 100644
--- a/activejob/test/support/integration/helper.rb
+++ b/activejob/test/support/integration/helper.rb
@@ -7,7 +7,7 @@ require "rails/generators/rails/app/app_generator"
 
 require "tmpdir"
 dummy_app_path     = Dir.mktmpdir + "/dummy"
-dummy_app_template = File.expand_path("../dummy_app_template.rb",  __FILE__)
+dummy_app_template = File.expand_path("dummy_app_template.rb",  __dir__)
 args = Rails::Generators::ARGVScrubber.new(["new", dummy_app_path, "--skip-gemfile", "--skip-bundle",
   "--skip-git", "--skip-spring", "-d", "sqlite3", "--skip-javascript", "--force", "--quiet",
   "--template", dummy_app_template]).prepare!
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index cdba0cee12..7483704212 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,30 +1,35 @@
+*   Fix regression in numericality validator when comparing Decimal and Float input 
+    values with more scale than the schema.
+
+    *Bradley Priest*
+
 *   Fix methods `#keys`, `#values` in `ActiveModel::Errors`.
 
     Change `#keys` to only return the keys that don't have empty messages.
 
     Change `#values` to only return the not empty values.
 
-     Example:
-
-         # Before
-         person = Person.new
-         person.errors.keys     # => []
-         person.errors.values   # => []
-         person.errors.messages # => {}
-         person.errors[:name]   # => []
-         person.errors.messages # => {:name => []}
-         person.errors.keys     # => [:name]
-         person.errors.values   # => [[]]
-
-         # After
-         person = Person.new
-         person.errors.keys     # => []
-         person.errors.values   # => []
-         person.errors.messages # => {}
-         person.errors[:name]   # => []
-         person.errors.messages # => {:name => []}
-         person.errors.keys     # => []
-         person.errors.values   # => []
+    Example:
+
+        # Before
+        person = Person.new
+        person.errors.keys     # => []
+        person.errors.values   # => []
+        person.errors.messages # => {}
+        person.errors[:name]   # => []
+        person.errors.messages # => {:name => []}
+        person.errors.keys     # => [:name]
+        person.errors.values   # => [[]]
+
+        # After
+        person = Person.new
+        person.errors.keys     # => []
+        person.errors.values   # => []
+        person.errors.messages # => {}
+        person.errors[:name]   # => []
+        person.errors.messages # => {:name => []}
+        person.errors.keys     # => []
+        person.errors.values   # => []
 
     *bogdanvlviv*
 
diff --git a/activemodel/Rakefile b/activemodel/Rakefile
index c7f97a4258..d60f6d9997 100644
--- a/activemodel/Rakefile
+++ b/activemodel/Rakefile
@@ -1,14 +1,12 @@
 require "rake/testtask"
 
-dir = File.dirname(__FILE__)
-
 task default: :test
 
 task :package
 
 Rake::TestTask.new do |t|
   t.libs << "test"
-  t.test_files = Dir.glob("#{dir}/test/cases/**/*_test.rb")
+  t.test_files = Dir.glob("#{__dir__}/test/cases/**/*_test.rb")
   t.warning = true
   t.verbose = true
   t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
@@ -16,8 +14,8 @@ end
 
 namespace :test do
   task :isolated do
-    Dir.glob("#{dir}/test/**/*_test.rb").all? do |file|
-      sh(Gem.ruby, "-w", "-I#{dir}/lib", "-I#{dir}/test", file)
+    Dir.glob("#{__dir__}/test/**/*_test.rb").all? do |file|
+      sh(Gem.ruby, "-w", "-I#{__dir__}/lib", "-I#{__dir__}/test", file)
     end || raise("Failures")
   end
 end
diff --git a/activemodel/activemodel.gemspec b/activemodel/activemodel.gemspec
index fd715f6ba9..43f1e09c77 100644
--- a/activemodel/activemodel.gemspec
+++ b/activemodel/activemodel.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index 2389c858d5..a2892e9ea9 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -68,5 +68,5 @@ module ActiveModel
 end
 
 ActiveSupport.on_load(:i18n) do
-  I18n.load_path << File.dirname(__FILE__) + "/active_model/locale/en.yml"
+  I18n.load_path << File.expand_path("active_model/locale/en.yml", __dir__)
 end
diff --git a/activemodel/lib/active_model/attribute_methods.rb b/activemodel/lib/active_model/attribute_methods.rb
index b5c0b43b61..b3b39bf7ae 100644
--- a/activemodel/lib/active_model/attribute_methods.rb
+++ b/activemodel/lib/active_model/attribute_methods.rb
@@ -68,9 +68,8 @@ module ActiveModel
     CALL_COMPILABLE_REGEXP = /\A[a-zA-Z_]\w*[!?]?\z/
 
     included do
-      class_attribute :attribute_aliases, :attribute_method_matchers, instance_writer: false
-      self.attribute_aliases = {}
-      self.attribute_method_matchers = [ClassMethods::AttributeMethodMatcher.new]
+      class_attribute :attribute_aliases, instance_writer: false, default: {}
+      class_attribute :attribute_method_matchers, instance_writer: false, default: [ ClassMethods::AttributeMethodMatcher.new ]
     end
 
     module ClassMethods
diff --git a/activemodel/lib/active_model/callbacks.rb b/activemodel/lib/active_model/callbacks.rb
index eac2761433..835e6f7716 100644
--- a/activemodel/lib/active_model/callbacks.rb
+++ b/activemodel/lib/active_model/callbacks.rb
@@ -56,6 +56,9 @@ module ActiveModel
   #
   # Would only create the +after_create+ and +before_create+ callback methods in
   # your class.
+  #
+  # NOTE: Calling the same callback multiple times will overwrite previous callback definitions.
+  #
   module Callbacks
     def self.extended(base) #:nodoc:
       base.class_eval do
diff --git a/activemodel/lib/active_model/serializers/json.rb b/activemodel/lib/active_model/serializers/json.rb
index a9d92eb92a..205b84ddb4 100644
--- a/activemodel/lib/active_model/serializers/json.rb
+++ b/activemodel/lib/active_model/serializers/json.rb
@@ -10,8 +10,7 @@ module ActiveModel
       included do
         extend ActiveModel::Naming
 
-        class_attribute :include_root_in_json, instance_writer: false
-        self.include_root_in_json = false
+        class_attribute :include_root_in_json, instance_writer: false, default: false
       end
 
       # Returns a hash representing the model. Some configuration can be
diff --git a/activemodel/lib/active_model/validations.rb b/activemodel/lib/active_model/validations.rb
index d460068830..ae1d69f685 100644
--- a/activemodel/lib/active_model/validations.rb
+++ b/activemodel/lib/active_model/validations.rb
@@ -49,8 +49,7 @@ module ActiveModel
       private :validation_context=
       define_callbacks :validate, scope: :name
 
-      class_attribute :_validators, instance_writer: false
-      self._validators = Hash.new { |h, k| h[k] = [] }
+      class_attribute :_validators, instance_writer: false, default: Hash.new { |h, k| h[k] = [] }
     end
 
     module ClassMethods
@@ -147,6 +146,9 @@ module ActiveModel
       #   or <tt>unless: Proc.new { |user| user.signup_step <= 2 }</tt>). The
       #   method, proc or string should return or evaluate to a +true+ or +false+
       #   value.
+      #
+      # NOTE: Calling +validate+ multiple times on the same method will overwrite previous definitions.
+      #
       def validate(*args, &block)
         options = args.extract_options!
 
@@ -432,4 +434,4 @@ module ActiveModel
   end
 end
 
-Dir[File.dirname(__FILE__) + "/validations/*.rb"].each { |file| require file }
+Dir[File.expand_path("validations/*.rb", __dir__)].each { |file| require file }
diff --git a/activemodel/lib/active_model/validations/numericality.rb b/activemodel/lib/active_model/validations/numericality.rb
index b82c85ddf4..fb053a4c4e 100644
--- a/activemodel/lib/active_model/validations/numericality.rb
+++ b/activemodel/lib/active_model/validations/numericality.rb
@@ -36,7 +36,9 @@ module ActiveModel
           return
         end
 
-        unless raw_value.is_a?(Numeric)
+        if raw_value.is_a?(Numeric)
+          value = raw_value
+        else
           value = parse_raw_value_as_a_number(raw_value)
         end
 
diff --git a/activemodel/lib/active_model/validations/validates.rb b/activemodel/lib/active_model/validations/validates.rb
index 0ce5935f3a..a8b958e974 100644
--- a/activemodel/lib/active_model/validations/validates.rb
+++ b/activemodel/lib/active_model/validations/validates.rb
@@ -18,7 +18,6 @@ module ActiveModel
       #   validates :first_name, length: { maximum: 30 }
       #   validates :age, numericality: true
       #   validates :username, presence: true
-      #   validates :username, uniqueness: true
       #
       # The power of the +validates+ method comes when using custom validators
       # and default validators in one call for a given attribute.
@@ -34,7 +33,7 @@ module ActiveModel
       #     include ActiveModel::Validations
       #     attr_accessor :name, :email
       #
-      #     validates :name, presence: true, uniqueness: true, length: { maximum: 100 }
+      #     validates :name, presence: true, length: { maximum: 100 }
       #     validates :email, presence: true, email: true
       #   end
       #
@@ -94,7 +93,7 @@ module ActiveModel
       # Example:
       #
       #   validates :password, presence: true, confirmation: true, if: :password_required?
-      #   validates :token, uniqueness: true, strict: TokenGenerationException
+      #   validates :token, length: 24, strict: TokenLengthException
       #
       #
       # Finally, the options +:if+, +:unless+, +:on+, +:allow_blank+, +:allow_nil+, +:strict+
diff --git a/activemodel/lib/active_model/validator.rb b/activemodel/lib/active_model/validator.rb
index 98234e9b6b..6c11981e1d 100644
--- a/activemodel/lib/active_model/validator.rb
+++ b/activemodel/lib/active_model/validator.rb
@@ -82,7 +82,7 @@ module ActiveModel
   #   end
   #
   # It can be useful to access the class that is using that validator when there are prerequisites such
-  # as an +attr_accessor+ being present. This class is accessible via +options[:class]+ in the constructor.
+  # as an +attr_accessor+ being present. This class is accessible via <tt>options[:class]</tt> in the constructor.
   # To setup your validator override the constructor.
   #
   #   class MyValidator < ActiveModel::Validator
@@ -97,7 +97,7 @@ module ActiveModel
     # Returns the kind of the validator.
     #
     #   PresenceValidator.kind   # => :presence
-    #   UniquenessValidator.kind # => :uniqueness
+    #   AcceptanceValidator.kind # => :acceptance
     def self.kind
       @kind ||= name.split("::").last.underscore.chomp("_validator").to_sym unless anonymous?
     end
@@ -109,8 +109,8 @@ module ActiveModel
 
     # Returns the kind for this validator.
     #
-    #   PresenceValidator.new.kind   # => :presence
-    #   UniquenessValidator.new.kind # => :uniqueness
+    #   PresenceValidator.new(attributes: [:username]).kind # => :presence
+    #   AcceptanceValidator.new(attributes: [:terms]).kind  # => :acceptance
     def kind
       self.class.kind
     end
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index a229b4eaa2..1f8163db12 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,4 +1,37 @@
-*   Quote database name in db:create grant statement (when database_user does not have access to create the database).
+*   Deprecate passing arguments and block at the same time to `count` and `sum` in `ActiveRecord::Calculations`.
+
+    *Ryuta Kamizono*
+
+*   Loading model schema from database is now thread-safe.
+
+    Fixes #28589.
+
+    *Vikrant Chaudhary*, *David Abdemoulaie*
+
+*   Add `ActiveRecord::Base#cache_version` to support recyclable cache keys via the new versioned entries
+    in `ActiveSupport::Cache`. This also means that `ActiveRecord::Base#cache_key` will now return a stable key
+    that does not include a timestamp any more.
+
+    NOTE: This feature is turned off by default, and `#cache_key` will still return cache keys with timestamps
+    until you set `ActiveRecord::Base.cache_versioning = true`. That's the setting for all new apps on Rails 5.2+
+
+    *DHH*
+
+*   Respect `SchemaDumper.ignore_tables` in rake tasks for databases structure dump
+
+    *Rusty Geldmacher*, *Guillermo Iguaran*
+
+*   Add type caster to `RuntimeReflection#alias_name`
+
+    Fixes #28959.
+
+    *Jon Moss*
+
+*   Deprecate `supports_statement_cache?`.
+
+    *Ryuta Kamizono*
+
+*   Quote database name in `db:create` grant statement (when database user does not have access to create the database).
 
     *Rune Philosof*
 
diff --git a/activerecord/Rakefile b/activerecord/Rakefile
index 7be3d851f1..2d0d5bd657 100644
--- a/activerecord/Rakefile
+++ b/activerecord/Rakefile
@@ -1,7 +1,7 @@
 require "rake/testtask"
 
-require File.expand_path(File.dirname(__FILE__)) + "/test/config"
-require File.expand_path(File.dirname(__FILE__)) + "/test/support/config"
+require File.expand_path("test/config", __dir__)
+require File.expand_path("test/support/config", __dir__)
 
 def run_without_aborting(*tasks)
   errors = []
@@ -134,7 +134,7 @@ task drop_postgresql_databases: "db:postgresql:drop"
 task rebuild_postgresql_databases: "db:postgresql:rebuild"
 
 task :lines do
-  load File.expand_path("..", File.dirname(__FILE__)) + "/tools/line_statistics"
+  load File.expand_path("../tools/line_statistics", __dir__)
   files = FileList["lib/active_record/**/*.rb"]
   CodeTools::LineStatistics.new(files).print_loc
 end
diff --git a/activerecord/activerecord.gemspec b/activerecord/activerecord.gemspec
index 0b37e9076c..450ec0bba9 100644
--- a/activerecord/activerecord.gemspec
+++ b/activerecord/activerecord.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 96b8545dfc..29f49c6195 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -177,5 +177,5 @@ ActiveSupport.on_load(:active_record) do
 end
 
 ActiveSupport.on_load(:i18n) do
-  I18n.load_path << File.dirname(__FILE__) + "/active_record/locale/en.yml"
+  I18n.load_path << File.expand_path("active_record/locale/en.yml", __dir__)
 end
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index e52c2004f3..7c37132d3a 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1276,7 +1276,7 @@ module ActiveRecord
         # Scope examples:
         #   has_many :comments, -> { where(author_id: 1) }
         #   has_many :employees, -> { joins(:address) }
-        #   has_many :posts, ->(post) { where("max_post_length > ?", post.length) }
+        #   has_many :posts, ->(blog) { where("max_post_length > ?", blog.max_post_length) }
         #
         # === Extensions
         #
@@ -1443,7 +1443,7 @@ module ActiveRecord
         # Scope examples:
         #   has_one :author, -> { where(comment_id: 1) }
         #   has_one :employer, -> { joins(:company) }
-        #   has_one :dob, ->(dob) { where("Date.new(2000, 01, 01) > ?", dob) }
+        #   has_one :latest_post, ->(blog) { where("created_at > ?", blog.enabled_at) }
         #
         # === Options
         #
@@ -1573,7 +1573,7 @@ module ActiveRecord
         # Scope examples:
         #   belongs_to :firm, -> { where(id: 2) }
         #   belongs_to :user, -> { joins(:friends) }
-        #   belongs_to :level, ->(level) { where("game_level > ?", level.current) }
+        #   belongs_to :level, ->(game) { where("game_level > ?", game.current_level) }
         #
         # === Options
         #
@@ -1769,9 +1769,8 @@ module ActiveRecord
         #
         # Scope examples:
         #   has_and_belongs_to_many :projects, -> { includes(:milestones, :manager) }
-        #   has_and_belongs_to_many :categories, ->(category) {
-        #     where("default_category = ?", category.name)
-        #   }
+        #   has_and_belongs_to_many :categories, ->(post) {
+        #     where("default_category = ?", post.default_category)
         #
         # === Extensions
         #
diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index 1cb2b2d7c6..6b13e6936f 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -152,14 +152,6 @@ module ActiveRecord
         reset
       end
 
-      def interpolate(sql, record = nil)
-        if sql.respond_to?(:to_proc)
-          owner.instance_exec(record, &sql)
-        else
-          sql
-        end
-      end
-
       # We can't dump @reflection since it contains the scope proc
       def marshal_dump
         ivars = (instance_variables - [:@reflection]).map { |name| [name, instance_variable_get(name)] }
diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index a2432e389a..0e61dbfb00 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -22,7 +22,7 @@ module ActiveRecord
       end
 
       def default(&block)
-        writer(instance_exec(&block)) if reader.nil?
+        writer(owner.instance_exec(&block)) if reader.nil?
       end
 
       def reset
diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index 8995b1e352..643226267c 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -106,12 +106,7 @@ module ActiveRecord
 
       def join_constraints(outer_joins, join_type)
         joins = join_root.children.flat_map { |child|
-
-          if join_type == Arel::Nodes::OuterJoin
-            make_left_outer_joins join_root, child
-          else
-            make_inner_joins join_root, child
-          end
+          make_join_constraints(join_root, child, join_type)
         }
 
         joins.concat outer_joins.flat_map { |oj|
@@ -175,27 +170,15 @@ module ActiveRecord
         end
 
         def make_outer_joins(parent, child)
-          tables    = table_aliases_for(parent, child)
-          join_type = Arel::Nodes::OuterJoin
-          info      = make_constraints parent, child, tables, join_type
-
-          [info] + child.children.flat_map { |c| make_outer_joins(child, c) }
-        end
-
-        def make_left_outer_joins(parent, child)
-          tables    = child.tables
           join_type = Arel::Nodes::OuterJoin
-          info      = make_constraints parent, child, tables, join_type
-
-          [info] + child.children.flat_map { |c| make_left_outer_joins(child, c) }
+          make_join_constraints(parent, child, join_type, true)
         end
 
-        def make_inner_joins(parent, child)
-          tables    = child.tables
-          join_type = Arel::Nodes::InnerJoin
-          info      = make_constraints parent, child, tables, join_type
+        def make_join_constraints(parent, child, join_type, aliasing = false)
+          tables = aliasing ? table_aliases_for(parent, child) : child.tables
+          info   = make_constraints(parent, child, tables, join_type)
 
-          [info] + child.children.flat_map { |c| make_inner_joins(child, c) }
+          [info] + child.children.flat_map { |c| make_join_constraints(child, c, join_type, aliasing) }
         end
 
         def table_aliases_for(parent, node)
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_part.rb b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
index 61cec5403a..80c9fde5d1 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_part.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
@@ -22,10 +22,6 @@ module ActiveRecord
           @children = children
         end
 
-        def name
-          reflection.name
-        end
-
         def match?(other)
           self.class == other.class
         end
diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb
index 9d44a02021..d53d3f777b 100644
--- a/activerecord/lib/active_record/associations/preloader/through_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/through_association.rb
@@ -16,15 +16,13 @@ module ActiveRecord
                             through_scope)
 
           through_records = owners.map do |owner|
-            association = owner.association through_reflection.name
-
-            center = target_records_from_association(association)
+            center = owner.association(through_reflection.name).target
             [owner, Array(center)]
           end
 
           reset_association owners, through_reflection.name
 
-          middle_records = through_records.flat_map { |(_, rec)| rec }
+          middle_records = through_records.flat_map(&:last)
 
           preloaders = preloader.preload(middle_records,
                                          source_reflection.name,
@@ -43,9 +41,7 @@ module ActiveRecord
 
             records_by_owner[lhs] = pl_to_middle.flat_map do |pl, middles|
               rhs_records = middles.flat_map { |r|
-                association = r.association source_reflection.name
-
-                target_records_from_association(association)
+                r.association(source_reflection.name).target
               }.compact
 
               # Respect the order on `reflection_scope` if it exists, else use the natural order.
@@ -98,10 +94,6 @@ module ActiveRecord
 
             scope
           end
-
-          def target_records_from_association(association)
-            association.loaded? ? association.target : association.reader
-          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/attribute_decorators.rb b/activerecord/lib/active_record/attribute_decorators.rb
index c39e9ce4c5..5bc8527745 100644
--- a/activerecord/lib/active_record/attribute_decorators.rb
+++ b/activerecord/lib/active_record/attribute_decorators.rb
@@ -3,8 +3,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :attribute_type_decorations, instance_accessor: false # :internal:
-      self.attribute_type_decorations = TypeDecorator.new
+      class_attribute :attribute_type_decorations, instance_accessor: false, default: TypeDecorator.new # :internal:
     end
 
     module ClassMethods # :nodoc:
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index ebe06566cc..83c61fad19 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -62,7 +62,6 @@ module ActiveRecord
           super(attribute_names)
           @attribute_methods_generated = true
         end
-        true
       end
 
       def undefine_attribute_methods # :nodoc:
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index bd5003d63a..76987fb8f4 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -14,8 +14,7 @@ module ActiveRecord
           raise "You cannot include Dirty after Timestamp"
         end
 
-        class_attribute :partial_writes, instance_writer: false
-        self.partial_writes = true
+        class_attribute :partial_writes, instance_writer: false, default: true
 
         after_create { changes_internally_applied }
         after_update { changes_internally_applied }
diff --git a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
index 321d039ed4..4a8d231503 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -57,11 +57,8 @@ module ActiveRecord
         mattr_accessor :time_zone_aware_attributes, instance_writer: false
         self.time_zone_aware_attributes = false
 
-        class_attribute :skip_time_zone_conversion_for_attributes, instance_writer: false
-        self.skip_time_zone_conversion_for_attributes = []
-
-        class_attribute :time_zone_aware_types, instance_writer: false
-        self.time_zone_aware_types = [:datetime, :time]
+        class_attribute :skip_time_zone_conversion_for_attributes, instance_writer: false, default: []
+        class_attribute :time_zone_aware_types, instance_writer: false, default: [ :datetime, :time ]
       end
 
       module ClassMethods
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activerecord/lib/active_record/attribute_set.rb
index 66b278219a..01f9d815d5 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activerecord/lib/active_record/attribute_set.rb
@@ -64,7 +64,7 @@ module ActiveRecord
     end
 
     def deep_dup
-      dup.tap do |copy|
+      self.class.allocate.tap do |copy|
         copy.instance_variable_set(:@attributes, attributes.deep_dup)
       end
     end
diff --git a/activerecord/lib/active_record/attributes.rb b/activerecord/lib/active_record/attributes.rb
index 75f5ba3a96..475b9beec4 100644
--- a/activerecord/lib/active_record/attributes.rb
+++ b/activerecord/lib/active_record/attributes.rb
@@ -6,8 +6,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :attributes_to_define_after_schema_loads, instance_accessor: false # :internal:
-      self.attributes_to_define_after_schema_loads = {}
+      class_attribute :attributes_to_define_after_schema_loads, instance_accessor: false, default: {} # :internal:
     end
 
     module ClassMethods
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 607c54e481..829a4f6e86 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -216,13 +216,7 @@ module ActiveRecord
               method = :validate_single_association
             end
 
-            define_non_cyclic_method(validation_method) do
-              send(method, reflection)
-              # TODO: remove the following line as soon as the return value of
-              # callbacks is ignored, that is, returning `false` does not
-              # display a deprecation warning or halts the callback chain.
-              true
-            end
+            define_non_cyclic_method(validation_method) { send(method, reflection) }
             validate validation_method
             after_validation :_ensure_no_duplicate_errors
           end
@@ -369,7 +363,6 @@ module ActiveRecord
       # association whether or not the parent was a new record before saving.
       def before_save_collection_association
         @new_record_before_save = new_record?
-        true
       end
 
       def after_save_collection_association
@@ -389,7 +382,7 @@ module ActiveRecord
           autosave = reflection.options[:autosave]
 
           # reconstruct the scope now that we know the owner's id
-          association.reset_scope if association.respond_to?(:reset_scope)
+          association.reset_scope
 
           if records = associated_records_to_validate_or_save(association, @new_record_before_save, autosave)
             if autosave
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index 1e1de1863a..8b937b6703 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -20,7 +20,7 @@ module ActiveRecord
           subquery_alias = "subquery_for_cache_key"
           subquery_column = "#{subquery_alias}.#{timestamp_column}"
           subquery = query.arel.as(subquery_alias)
-          arel = Arel::SelectManager.new(query.engine).project(select_values % subquery_column).from(subquery)
+          arel = Arel::SelectManager.new(subquery).project(select_values % subquery_column)
         else
           query = collection.unscope(:order)
           query.select_values = [select_values % column]
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 769f488469..c6811a4802 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -137,9 +137,10 @@ module ActiveRecord
 
       # Returns +true+ when the connection adapter supports prepared statement
       # caching, otherwise returns +false+
-      def supports_statement_cache?
-        false
+      def supports_statement_cache? # :nodoc:
+        true
       end
+      deprecate :supports_statement_cache?
 
       # Runs the given block in a database transaction, and returns the result
       # of the block.
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index f0c0fbab6c..61233dcc51 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -10,8 +10,15 @@ module ActiveRecord
         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 \
-            "Using #quoted_id is deprecated and will be removed in Rails 5.2."
+            "Defining #quoted_id is deprecated and will be ignored in Rails 5.2. (defined on #{klass}#{at})"
           return value.quoted_id
         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 46d7f84efd..a30fbe0e05 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -146,7 +146,7 @@ module ActiveRecord
         end
 
         def polymorphic_options
-          as_options(polymorphic)
+          as_options(polymorphic).merge(null: options[:null])
         end
 
         def index_options
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 13629dee7f..16a398f631 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1280,9 +1280,10 @@ module ActiveRecord
         end
 
         def foreign_key_name(table_name, options)
-          identifier = "#{table_name}_#{options.fetch(:column)}_fk"
-          hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
           options.fetch(:name) do
+            identifier = "#{table_name}_#{options.fetch(:column)}_fk"
+            hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
+
             "fk_rails_#{hashed_identifier}"
           end
         end
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 c742799aab..9cb7c46df5 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -29,8 +29,7 @@ module ActiveRecord
       # to your application.rb file:
       #
       #   ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans = false
-      class_attribute :emulate_booleans
-      self.emulate_booleans = true
+      class_attribute :emulate_booleans, default: true
 
       NATIVE_DATABASE_TYPES = {
         primary_key: "bigint auto_increment PRIMARY KEY",
@@ -76,12 +75,6 @@ module ActiveRecord
         true
       end
 
-      # Returns true, since this connection adapter supports prepared statement
-      # caching.
-      def supports_statement_cache?
-        true
-      end
-
       def supports_index_sort_order?
         !mariadb? && version >= "8.0.1"
       end
@@ -720,16 +713,14 @@ module ActiveRecord
         # MySQL is too stupid to create a temporary table for use subquery, so we have
         # to give it some prompting in the form of a subsubquery. Ugh!
         def subquery_for(key, select)
-          subsubselect = select.clone
-          subsubselect.projections = [key]
+          subselect = select.clone
+          subselect.projections = [key]
 
           # Materialize subquery by adding distinct
           # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
-          subsubselect.distinct unless select.limit || select.offset || select.orders.any?
+          subselect.distinct unless select.limit || select.offset || select.orders.any?
 
-          subselect = Arel::SelectManager.new(select.engine)
-          subselect.project Arel.sql(key.name)
-          subselect.from subsubselect.as("__active_record_temp")
+          Arel::SelectManager.new(subselect.as("__active_record_temp")).project(Arel.sql(key.name))
         end
 
         def supports_rename_index?
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 5b483ad4ab..55566f1e34 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -186,17 +186,17 @@ module ActiveRecord
 
         # Returns the current database encoding format.
         def encoding
-          select_value("SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname LIKE '#{current_database}'", "SCHEMA")
+          select_value("SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname = current_database()", "SCHEMA")
         end
 
         # Returns the current database collation.
         def collation
-          select_value("SELECT datcollate FROM pg_database WHERE datname LIKE '#{current_database}'", "SCHEMA")
+          select_value("SELECT datcollate FROM pg_database WHERE datname = current_database()", "SCHEMA")
         end
 
         # Returns the current database ctype.
         def ctype
-          select_value("SELECT datctype FROM pg_database WHERE datname LIKE '#{current_database}'", "SCHEMA")
+          select_value("SELECT datctype FROM pg_database WHERE datname = current_database()", "SCHEMA")
         end
 
         # Returns an array of schema names.
@@ -377,14 +377,15 @@ module ActiveRecord
           clear_cache!
           execute "ALTER TABLE #{quote_table_name(table_name)} RENAME TO #{quote_table_name(new_name)}"
           pk, seq = pk_and_sequence_for(new_name)
-          if seq && seq.identifier == "#{table_name}_#{pk}_seq"
-            new_seq = "#{new_name}_#{pk}_seq"
+          if pk
             idx = "#{table_name}_pkey"
             new_idx = "#{new_name}_pkey"
-            execute "ALTER TABLE #{seq.quoted} RENAME TO #{quote_table_name(new_seq)}"
             execute "ALTER INDEX #{quote_table_name(idx)} RENAME TO #{quote_table_name(new_idx)}"
+            if seq && seq.identifier == "#{table_name}_#{pk}_seq"
+              new_seq = "#{new_name}_#{pk}_seq"
+              execute "ALTER TABLE #{seq.quoted} RENAME TO #{quote_table_name(new_seq)}"
+            end
           end
-
           rename_table_indexes(table_name, new_name)
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 033d81916e..f74f966fd9 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -121,12 +121,6 @@ module ActiveRecord
       include PostgreSQL::DatabaseStatements
       include PostgreSQL::ColumnDumper
 
-      # Returns true, since this connection adapter supports prepared statement
-      # caching.
-      def supports_statement_cache?
-        true
-      end
-
       def supports_index_sort_order?
         true
       end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index e2c05ccc4e..7233325d5a 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -105,12 +105,6 @@ module ActiveRecord
         sqlite_version >= "3.8.0"
       end
 
-      # Returns true, since this connection adapter supports prepared statement
-      # caching.
-      def supports_statement_cache?
-        true
-      end
-
       def requires_reloading?
         true
       end
diff --git a/activerecord/lib/active_record/connection_handling.rb b/activerecord/lib/active_record/connection_handling.rb
index 2ede92feff..b8fbb489b6 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -1,6 +1,6 @@
 module ActiveRecord
   module ConnectionHandling
-    RAILS_ENV   = -> { (Rails.env if defined?(Rails.env)) || ENV["RAILS_ENV"] || ENV["RACK_ENV"] }
+    RAILS_ENV   = -> { (Rails.env if defined?(Rails.env)) || ENV["RAILS_ENV"].presence || ENV["RACK_ENV"].presence }
     DEFAULT_ENV = -> { RAILS_ENV.call || "default_env" }
 
     # Establishes the connection to the database. Accepts a hash as input where
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index 0ab03b2ab3..12ef58a941 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -95,8 +95,7 @@ module ActiveRecord
 
   module Enum
     def self.extended(base) # :nodoc:
-      base.class_attribute(:defined_enums, instance_writer: false)
-      base.defined_enums = {}
+      base.class_attribute(:defined_enums, instance_writer: false, default: {})
     end
 
     def inherited(base) # :nodoc:
@@ -154,11 +153,12 @@ module ActiveRecord
       definitions.each do |name, values|
         # statuses = { }
         enum_values = ActiveSupport::HashWithIndifferentAccess.new
-        name        = name.to_sym
+        name = name.to_s
 
         # def self.statuses() statuses end
-        detect_enum_conflict!(name, name.to_s.pluralize, true)
-        klass.singleton_class.send(:define_method, name.to_s.pluralize) { enum_values }
+        detect_enum_conflict!(name, name.pluralize, true)
+        singleton_class.send(:define_method, name.pluralize) { enum_values }
+        defined_enums[name] = enum_values
 
         detect_enum_conflict!(name, name)
         detect_enum_conflict!(name, "#{name}=")
@@ -170,7 +170,7 @@ module ActiveRecord
 
         _enum_methods_module.module_eval do
           pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
-          pairs.each do |value, i|
+          pairs.each do |label, value|
             if enum_prefix == true
               prefix = "#{name}_"
             elsif enum_prefix
@@ -182,23 +182,23 @@ module ActiveRecord
               suffix = "_#{enum_suffix}"
             end
 
-            value_method_name = "#{prefix}#{value}#{suffix}"
-            enum_values[value] = i
+            value_method_name = "#{prefix}#{label}#{suffix}"
+            enum_values[label] = value
+            label = label.to_s
 
-            # def active?() status == 0 end
+            # def active?() status == "active" end
             klass.send(:detect_enum_conflict!, name, "#{value_method_name}?")
-            define_method("#{value_method_name}?") { self[attr] == value.to_s }
+            define_method("#{value_method_name}?") { self[attr] == label }
 
-            # def active!() update! status: :active end
+            # def active!() update!(status: 0) end
             klass.send(:detect_enum_conflict!, name, "#{value_method_name}!")
             define_method("#{value_method_name}!") { update!(attr => value) }
 
-            # scope :active, -> { where status: 0 }
+            # scope :active, -> { where(status: 0) }
             klass.send(:detect_enum_conflict!, name, value_method_name, true)
             klass.scope value_method_name, -> { where(attr => value) }
           end
         end
-        defined_enums[name.to_s] = enum_values
       end
     end
 
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index c19216702c..bad6542be2 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -878,20 +878,12 @@ module ActiveRecord
 
     included do
       class_attribute :fixture_path, instance_writer: false
-      class_attribute :fixture_table_names
-      class_attribute :fixture_class_names
-      class_attribute :use_transactional_tests
-      class_attribute :use_instantiated_fixtures # true, false, or :no_instances
-      class_attribute :pre_loaded_fixtures
-      class_attribute :config
-
-      self.fixture_table_names = []
-      self.use_instantiated_fixtures = false
-      self.pre_loaded_fixtures = false
-      self.config = ActiveRecord::Base
-
-      self.fixture_class_names = {}
-      self.use_transactional_tests = true
+      class_attribute :fixture_table_names, default: []
+      class_attribute :fixture_class_names, default: {}
+      class_attribute :use_transactional_tests, default: true
+      class_attribute :use_instantiated_fixtures, default: false # true, false, or :no_instances
+      class_attribute :pre_loaded_fixtures, default: false
+      class_attribute :config, default: ActiveRecord::Base
     end
 
     module ClassMethods
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb
index fbdaeaae51..5776807507 100644
--- a/activerecord/lib/active_record/inheritance.rb
+++ b/activerecord/lib/active_record/inheritance.rb
@@ -38,8 +38,7 @@ module ActiveRecord
     included do
       # Determines whether to store the full constant name including namespace when using STI.
       # This is true, by default.
-      class_attribute :store_full_sti_class, instance_writer: false
-      self.store_full_sti_class = true
+      class_attribute :store_full_sti_class, instance_writer: false, default: true
     end
 
     module ClassMethods
@@ -217,7 +216,7 @@ module ActiveRecord
         def subclass_from_attributes(attrs)
           attrs = attrs.to_h if attrs.respond_to?(:permitted?)
           if attrs.is_a?(Hash)
-            subclass_name = attrs.with_indifferent_access[inheritance_column]
+            subclass_name = attrs[inheritance_column] || attrs[inheritance_column.to_sym]
 
             if subclass_name.present?
               find_sti_class(subclass_name)
diff --git a/activerecord/lib/active_record/integration.rb b/activerecord/lib/active_record/integration.rb
index 8e71b60b29..cf954852bc 100644
--- a/activerecord/lib/active_record/integration.rb
+++ b/activerecord/lib/active_record/integration.rb
@@ -7,12 +7,19 @@ module ActiveRecord
     included do
       ##
       # :singleton-method:
-      # Indicates the format used to generate the timestamp in the cache key.
-      # Accepts any of the symbols in <tt>Time::DATE_FORMATS</tt>.
+      # Indicates the format used to generate the timestamp in the cache key, if
+      # versioning is off. Accepts any of the symbols in <tt>Time::DATE_FORMATS</tt>.
       #
       # This is +:usec+, by default.
-      class_attribute :cache_timestamp_format, instance_writer: false
-      self.cache_timestamp_format = :usec
+      class_attribute :cache_timestamp_format, instance_writer: false, default: :usec
+
+      ##
+      # :singleton-method:
+      # Indicates whether to use a stable #cache_key method that is accompanied
+      # by a changing version in the #cache_version method.
+      #
+      # This is +false+, by default until Rails 6.0.
+      class_attribute :cache_versioning, instance_writer: false, default: false
     end
 
     # Returns a +String+, which Action Pack uses for constructing a URL to this
@@ -42,35 +49,65 @@ module ActiveRecord
       id && id.to_s # Be sure to stringify the id for routes
     end
 
-    # Returns a cache key that can be used to identify this record.
+    # Returns a stable cache key that can be used to identify this record.
     #
     #   Product.new.cache_key     # => "products/new"
-    #   Product.find(5).cache_key # => "products/5" (updated_at not available)
-    #   Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)
+    #   Product.find(5).cache_key # => "products/5"
     #
-    # You can also pass a list of named timestamps, and the newest in the list will be
-    # used to generate the key:
+    # If ActiveRecord::Base.cache_versioning is turned off, as it was in Rails 5.1 and earlier,
+    # the cache key will also include a version.
     #
-    #   Person.find(5).cache_key(:updated_at, :last_reviewed_at)
+    #   Product.cache_versioning = false
+    #   Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)
     def cache_key(*timestamp_names)
       if new_record?
         "#{model_name.cache_key}/new"
       else
-        timestamp = if timestamp_names.any?
-          max_updated_column_timestamp(timestamp_names)
+        if cache_version && timestamp_names.none?
+          "#{model_name.cache_key}/#{id}"
         else
-          max_updated_column_timestamp
-        end
+          timestamp = if timestamp_names.any?
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              Specifying a timestamp name for #cache_key has been deprecated in favor of
+              the explicit #cache_version method that can be overwritten.
+            MSG
 
-        if timestamp
-          timestamp = timestamp.utc.to_s(cache_timestamp_format)
-          "#{model_name.cache_key}/#{id}-#{timestamp}"
-        else
-          "#{model_name.cache_key}/#{id}"
+            max_updated_column_timestamp(timestamp_names)
+          else
+            max_updated_column_timestamp
+          end
+
+          if timestamp
+            timestamp = timestamp.utc.to_s(cache_timestamp_format)
+            "#{model_name.cache_key}/#{id}-#{timestamp}"
+          else
+            "#{model_name.cache_key}/#{id}"
+          end
         end
       end
     end
 
+    # Returns a cache version that can be used together with the cache key to form
+    # a recyclable caching scheme. By default, the #updated_at column is used for the
+    # cache_version, but this method can be overwritten to return something else.
+    #
+    # Note, this method will return nil if ActiveRecord::Base.cache_versioning is set to
+    # +false+ (which it is by default until Rails 6.0).
+    def cache_version
+      if cache_versioning && timestamp = try(:updated_at)
+        timestamp.utc.to_s(:usec)
+      end
+    end
+
+    # Returns a cache key along with the version.
+    def cache_key_with_version
+      if version = cache_version
+        "#{cache_key}-#{version}"
+      else
+        cache_key
+      end
+    end
+
     module ClassMethods
       # Defines your model's +to_param+ method to generate "pretty" URLs
       # using +method_name+, which can be any attribute or method that
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index 78ce9f8291..3c7110369b 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -51,8 +51,7 @@ module ActiveRecord
       extend ActiveSupport::Concern
 
       included do
-        class_attribute :lock_optimistically, instance_writer: false
-        self.lock_optimistically = true
+        class_attribute :lock_optimistically, instance_writer: false, default: true
       end
 
       def locking_enabled? #:nodoc:
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 54216caaaf..1179a60e9b 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -1,3 +1,5 @@
+require "monitor"
+
 module ActiveRecord
   module ModelSchema
     extend ActiveSupport::Concern
@@ -128,30 +130,19 @@ module ActiveRecord
     included do
       mattr_accessor :primary_key_prefix_type, instance_writer: false
 
-      class_attribute :table_name_prefix, instance_writer: false
-      self.table_name_prefix = ""
-
-      class_attribute :table_name_suffix, instance_writer: false
-      self.table_name_suffix = ""
-
-      class_attribute :schema_migrations_table_name, instance_accessor: false
-      self.schema_migrations_table_name = "schema_migrations"
-
-      class_attribute :internal_metadata_table_name, instance_accessor: false
-      self.internal_metadata_table_name = "ar_internal_metadata"
-
-      class_attribute :protected_environments, instance_accessor: false
-      self.protected_environments = ["production"]
-
-      class_attribute :pluralize_table_names, instance_writer: false
-      self.pluralize_table_names = true
-
-      class_attribute :ignored_columns, instance_accessor: false
-      self.ignored_columns = [].freeze
+      class_attribute :table_name_prefix, instance_writer: false, default: ""
+      class_attribute :table_name_suffix, instance_writer: false, default: ""
+      class_attribute :schema_migrations_table_name, instance_accessor: false, default: "schema_migrations"
+      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"
 
       delegate :type_for_attribute, to: :class
+
+      initialize_load_schema_monitor
     end
 
     # Derives the join table name for +first_table+ and +second_table+. The
@@ -377,7 +368,7 @@ module ActiveRecord
       # default values when instantiating the Active Record object for this table.
       def column_defaults
         load_schema
-        _default_attributes.to_hash
+        @column_defaults ||= _default_attributes.to_hash
       end
 
       def _default_attributes # :nodoc:
@@ -435,15 +426,27 @@ module ActiveRecord
         initialize_find_by_cache
       end
 
+      protected
+
+        def initialize_load_schema_monitor
+          @load_schema_monitor = Monitor.new
+        end
+
       private
 
+        def inherited(child_class)
+          super
+          child_class.initialize_load_schema_monitor
+        end
+
         def schema_loaded?
-          defined?(@columns_hash) && @columns_hash
+          defined?(@schema_loaded) && @schema_loaded
         end
 
         def load_schema
-          unless schema_loaded?
-            load_schema!
+          return if schema_loaded?
+          @load_schema_monitor.synchronize do
+            load_schema! unless defined?(@columns_hash) && @columns_hash
           end
         end
 
@@ -457,6 +460,8 @@ module ActiveRecord
               user_provided_default: false
             )
           end
+
+          @schema_loaded = true
         end
 
         def reload_schema_from_cache
@@ -466,10 +471,12 @@ module ActiveRecord
           @attribute_types = nil
           @content_columns = nil
           @default_attributes = nil
+          @column_defaults = nil
           @inheritance_column = nil unless defined?(@explicit_inheritance_column) && @explicit_inheritance_column
           @attributes_builder = nil
           @columns = nil
           @columns_hash = nil
+          @schema_loaded = false
           @attribute_names = nil
           @yaml_encoder = nil
           direct_descendants.each do |descendant|
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 01ecd79b8f..917bc76993 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -10,8 +10,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :nested_attributes_options, instance_writer: false
-      self.nested_attributes_options = {}
+      class_attribute :nested_attributes_options, instance_writer: false, default: {}
     end
 
     # = Active Record Nested Attributes
@@ -458,7 +457,7 @@ module ActiveRecord
         end
 
         unless attributes_collection.is_a?(Hash) || attributes_collection.is_a?(Array)
-          raise ArgumentError, "Hash or Array expected, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
+          raise ArgumentError, "Hash or Array expected for attribute `#{association_name}`, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
         end
 
         check_record_limit!(options[:limit], attributes_collection)
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index f3e2df8786..711099e9e1 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -93,7 +93,7 @@ db_namespace = namespace :db do
 
     # desc 'Runs the "up" for a given migration VERSION.'
     task up: [:environment, :load_config] do
-      raise "VERSION is required" if ENV["VERSION"] && ENV["VERSION"].empty?
+      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)
@@ -102,7 +102,7 @@ db_namespace = namespace :db do
 
     # desc 'Runs the "down" for a given migration VERSION.'
     task down: [:environment, :load_config] do
-      raise "VERSION is required - To go down one migration, use db:rollback" if ENV["VERSION"] && ENV["VERSION"].empty?
+      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)
       db_namespace["_dump"].invoke
diff --git a/activerecord/lib/active_record/readonly_attributes.rb b/activerecord/lib/active_record/readonly_attributes.rb
index 6274996ab8..af6473d250 100644
--- a/activerecord/lib/active_record/readonly_attributes.rb
+++ b/activerecord/lib/active_record/readonly_attributes.rb
@@ -3,8 +3,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_attr_readonly, instance_accessor: false
-      self._attr_readonly = []
+      class_attribute :_attr_readonly, instance_accessor: false, default: []
     end
 
     module ClassMethods
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 24ca8b0be4..d6154c9a38 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -8,10 +8,8 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_reflections, instance_writer: false
-      class_attribute :aggregate_reflections, instance_writer: false
-      self._reflections = {}
-      self.aggregate_reflections = {}
+      class_attribute :_reflections, instance_writer: false, default: {}
+      class_attribute :aggregate_reflections, instance_writer: false, default: {}
     end
 
     def self.create(macro, name, scope, options, ar)
@@ -199,7 +197,7 @@ module ActiveRecord
       def klass_join_scope(table, predicate_builder) # :nodoc:
         if klass.current_scope
           klass.current_scope.clone.tap { |scope|
-            scope.joins_values = []
+            scope.joins_values = scope.left_outer_joins_values = [].freeze
           }
         else
           relation = ActiveRecord::Relation.create(
@@ -212,7 +210,7 @@ module ActiveRecord
       end
 
       def constraints
-        chain.map(&:scopes).flatten
+        chain.flat_map(&:scopes)
       end
 
       def counter_cache_column
@@ -1105,7 +1103,7 @@ module ActiveRecord
       end
 
       def alias_name
-        Arel::Table.new(table_name)
+        Arel::Table.new(table_name, type_caster: klass.type_caster)
       end
 
       def all_includes; yield; end
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 5775eda5a5..7a8f9abb36 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -2,7 +2,7 @@ module ActiveRecord
   # = Active Record \Relation
   class Relation
     MULTI_VALUE_METHODS  = [:includes, :eager_load, :preload, :select, :group,
-                            :order, :joins, :left_joins, :left_outer_joins, :references,
+                            :order, :joins, :left_outer_joins, :references,
                             :extending, :unscope]
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering,
@@ -18,6 +18,7 @@ module ActiveRecord
     attr_reader :table, :klass, :loaded, :predicate_builder
     alias :model :klass
     alias :loaded? :loaded
+    alias :locked? :locked
 
     def initialize(klass, table, predicate_builder, values = {})
       @klass  = klass
@@ -269,8 +270,7 @@ module ActiveRecord
     # Returns true if there are no records.
     def empty?
       return @records.empty? if loaded?
-
-      limit_value == 0 || !exists?
+      !exists?
     end
 
     # Returns true if there are no records.
@@ -404,9 +404,9 @@ module ActiveRecord
     #
     # Note: Updating a large number of records will run an
     # UPDATE query for each record, which may cause a performance
-    # issue. So if it is not needed to run callbacks for each update, it is
-    # preferred to use #update_all for updating all records using
-    # a single query.
+    # 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]) }
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index 76031515fd..13a2c3f511 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -30,14 +30,14 @@ module ActiveRecord
     #   end
     #
     # ==== Options
-    # * <tt>:batch_size</tt> - Specifies the size of the batch. Default to 1000.
+    # * <tt>:batch_size</tt> - Specifies the size of the batch. Defaults to 1000.
     # * <tt>:start</tt> - Specifies the primary key value to start from, inclusive of the value.
     # * <tt>:finish</tt> - Specifies the primary key value to end at, inclusive of the value.
     # * <tt>:error_on_ignore</tt> - Overrides the application config to specify if an error should be raised when
-    #                               an order is present in the relation.
+    #   an order is present in the relation.
     #
     # Limits are honored, and if present there is no requirement for the batch
-    # size, it can be less than, equal, or greater than the limit.
+    # size: it can be less than, equal to, or greater than the limit.
     #
     # The options +start+ and +finish+ are especially useful if you want
     # multiple workers dealing with the same processing queue. You can make
@@ -89,14 +89,14 @@ module ActiveRecord
     # To be yielded each record one by one, use #find_each instead.
     #
     # ==== Options
-    # * <tt>:batch_size</tt> - Specifies the size of the batch. Default to 1000.
+    # * <tt>:batch_size</tt> - Specifies the size of the batch. Defaults to 1000.
     # * <tt>:start</tt> - Specifies the primary key value to start from, inclusive of the value.
     # * <tt>:finish</tt> - Specifies the primary key value to end at, inclusive of the value.
     # * <tt>:error_on_ignore</tt> - Overrides the application config to specify if an error should be raised when
-    #                               an order is present in the relation.
+    #   an order is present in the relation.
     #
     # Limits are honored, and if present there is no requirement for the batch
-    # size, it can be less than, equal, or greater than the limit.
+    # size: it can be less than, equal to, or greater than the limit.
     #
     # The options +start+ and +finish+ are especially useful if you want
     # multiple workers dealing with the same processing queue. You can make
@@ -140,9 +140,9 @@ module ActiveRecord
     # If you do not provide a block to #in_batches, it will return a
     # BatchEnumerator which is enumerable.
     #
-    #   Person.in_batches.with_index do |relation, batch_index|
+    #   Person.in_batches.each_with_index do |relation, batch_index|
     #     puts "Processing relation ##{batch_index}"
-    #     relation.each { |relation| relation.delete_all }
+    #     relation.delete_all
     #   end
     #
     # Examples of calling methods on the returned BatchEnumerator object:
@@ -152,12 +152,12 @@ module ActiveRecord
     #   Person.in_batches.each_record(&:party_all_night!)
     #
     # ==== Options
-    # * <tt>:of</tt> - Specifies the size of the batch. Default to 1000.
-    # * <tt>:load</tt> - Specifies if the relation should be loaded. Default to false.
+    # * <tt>:of</tt> - Specifies the size of the batch. Defaults to 1000.
+    # * <tt>:load</tt> - Specifies if the relation should be loaded. Defaults to false.
     # * <tt>:start</tt> - Specifies the primary key value to start from, inclusive of the value.
     # * <tt>:finish</tt> - Specifies the primary key value to end at, inclusive of the value.
     # * <tt>:error_on_ignore</tt> - Overrides the application config to specify if an error should be raised when
-    #                               an order is present in the relation.
+    #   an order is present in the relation.
     #
     # Limits are honored, and if present there is no requirement for the batch
     # size, it can be less than, equal, or greater than the limit.
@@ -186,7 +186,7 @@ module ActiveRecord
     #
     # NOTE: It's not possible to set the order. That is automatically set to
     # ascending on the primary key ("id ASC") to make the batch ordering
-    # consistent. Therefore the primary key must be orderable, e.g an integer
+    # consistent. Therefore the primary key must be orderable, e.g. an integer
     # or a string.
     #
     # NOTE: By its nature, batch processing is subject to race conditions if
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 9cabd1af13..c562f214c9 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -37,7 +37,16 @@ module ActiveRecord
     # Note: not all valid {Relation#select}[rdoc-ref:QueryMethods#select] expressions are valid #count expressions. The specifics differ
     # between databases. In invalid cases, an error from the database is thrown.
     def count(column_name = nil)
-      return super() if block_given?
+      if block_given?
+        unless column_name.nil?
+          ActiveSupport::Deprecation.warn \
+            "When `count' is called with a block, it ignores other arguments. " \
+            "This behavior is now deprecated and will result in an ArgumentError in Rails 5.3."
+        end
+
+        return super()
+      end
+
       calculate(:count, column_name)
     end
 
@@ -73,7 +82,16 @@ module ActiveRecord
     #
     #   Person.sum(:age) # => 4562
     def sum(column_name = nil)
-      return super() if block_given?
+      if block_given?
+        unless column_name.nil?
+          ActiveSupport::Deprecation.warn \
+            "When `sum' is called with a block, it ignores other arguments. " \
+            "This behavior is now deprecated and will result in an ArgumentError in Rails 5.3."
+        end
+
+        return super()
+      end
+
       calculate(:sum, column_name)
     end
 
@@ -368,9 +386,8 @@ module ActiveRecord
         relation.select_values = [aliased_column]
         subquery = relation.arel.as(subquery_alias)
 
-        sm = Arel::SelectManager.new relation.engine
         select_value = operation_over_aggregate_column(column_alias, "count", distinct)
-        sm.project(select_value).from(subquery)
+        Arel::SelectManager.new(subquery).project(select_value)
       end
   end
 end
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 257ae04ff4..4f739a0415 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -46,6 +46,8 @@ module ActiveRecord
     delegate :table_name, :quoted_table_name, :primary_key, :quoted_primary_key,
              :connection, :columns_hash, to: :klass
 
+    delegate :ast, :locked, to: :arel
+
     module ClassSpecificRelation # :nodoc:
       extend ActiveSupport::Concern
 
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index a1459c87c6..1d661fa8ed 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -307,9 +307,11 @@ module ActiveRecord
         MSG
       end
 
-      return false if !conditions
+      return false if !conditions || limit_value == 0
+
+      relation = self unless eager_loading?
+      relation ||= apply_join_dependency(self, construct_join_dependency(eager_loading: false))
 
-      relation = apply_join_dependency(self, construct_join_dependency(eager_loading: false))
       return false if ActiveRecord::NullRelation === relation
 
       relation = construct_relation_for_exists(relation, conditions)
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index 183fe91c05..a6309e0b5c 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -1,12 +1,3 @@
-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 "active_record/relation/predicate_builder/association_query_value"
-require "active_record/relation/predicate_builder/polymorphic_array_value"
-
 module ActiveRecord
   class PredicateBuilder # :nodoc:
     delegate :resolve_column_aliases, to: :table
@@ -178,3 +169,12 @@ module ActiveRecord
       end
   end
 end
+
+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 "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/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 1178dec706..79e65baae5 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -248,7 +248,7 @@ module ActiveRecord
         return super()
       end
 
-      raise ArgumentError, "Call this with at least one field" if fields.empty?
+      raise ArgumentError, "Call `select' with at least one field" if fields.empty?
       spawn._select!(*fields)
     end
 
@@ -1100,14 +1100,16 @@ module ActiveRecord
       end
 
       VALID_DIRECTIONS = [:asc, :desc, :ASC, :DESC,
-                          "asc", "desc", "ASC", "DESC"] # :nodoc:
+                          "asc", "desc", "ASC", "DESC"].to_set # :nodoc:
 
       def validate_order_args(args)
         args.each do |arg|
           next unless arg.is_a?(Hash)
           arg.each do |_key, value|
-            raise ArgumentError, "Direction \"#{value}\" is invalid. Valid " \
-                                 "directions are: #{VALID_DIRECTIONS.inspect}" unless VALID_DIRECTIONS.include?(value)
+            unless VALID_DIRECTIONS.include?(value)
+              raise ArgumentError,
+                "Direction \"#{value}\" is invalid. Valid directions are: #{VALID_DIRECTIONS.to_a.inspect}"
+            end
           end
         end
       end
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 94d63765c9..24b81aabc8 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -11,8 +11,8 @@ module ActiveRecord
     ##
     # :singleton-method:
     # A list of tables which should not be dumped to the schema.
-    # Acceptable values are strings as well as regexp.
-    # This setting is only used if ActiveRecord::Base.schema_format == :ruby
+    # Acceptable values are strings as well as regexp if ActiveRecord::Base.schema_format == :ruby.
+    # Only strings are accepted if ActiveRecord::Base.schema_format == :sql.
     cattr_accessor :ignore_tables
     @@ignore_tables = []
 
diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index 2daa48859a..ba5cc29ac1 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -5,11 +5,8 @@ module ActiveRecord
 
       included do
         # Stores the default scope for the class.
-        class_attribute :default_scopes, instance_writer: false, instance_predicate: false
-        class_attribute :default_scope_override, instance_writer: false, instance_predicate: false
-
-        self.default_scopes = []
-        self.default_scope_override = nil
+        class_attribute :default_scopes, instance_writer: false, instance_predicate: false, default: []
+        class_attribute :default_scope_override, instance_writer: false, instance_predicate: false, default: nil
       end
 
       module ClassMethods
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index 27cdf8cb7e..029156189d 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -156,17 +156,17 @@ module ActiveRecord
 
           if body.respond_to?(:to_proc)
             singleton_class.send(:define_method, name) do |*args|
-              scope = all.scoping { instance_exec(*args, &body) }
+              scope = all
+              scope = scope.scoping { instance_exec(*args, &body) || scope }
               scope = scope.extending(extension) if extension
-
-              scope || all
+              scope
             end
           else
             singleton_class.send(:define_method, name) do |*args|
-              scope = all.scoping { body.call(*args) }
+              scope = all
+              scope = scope.scoping { body.call(*args) || scope }
               scope = scope.extending(extension) if extension
-
-              scope || all
+              scope
             end
           end
         end
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 45110a79cd..ba686fc562 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -71,9 +71,9 @@ module ActiveRecord
         @tasks[pattern] = task
       end
 
-      register_task(/mysql/,        ActiveRecord::Tasks::MySQLDatabaseTasks)
-      register_task(/postgresql/,   ActiveRecord::Tasks::PostgreSQLDatabaseTasks)
-      register_task(/sqlite/,       ActiveRecord::Tasks::SQLiteDatabaseTasks)
+      register_task(/mysql/,        "ActiveRecord::Tasks::MySQLDatabaseTasks")
+      register_task(/postgresql/,   "ActiveRecord::Tasks::PostgreSQLDatabaseTasks")
+      register_task(/sqlite/,       "ActiveRecord::Tasks::SQLiteDatabaseTasks")
 
       def db_dir
         @db_dir ||= Rails.application.config.paths["db"].first
@@ -288,11 +288,11 @@ module ActiveRecord
       private
 
         def class_for_adapter(adapter)
-          key = @tasks.keys.detect { |pattern| adapter[pattern] }
-          unless key
+          _key, task = @tasks.each_pair.detect { |pattern, _task| adapter[pattern] }
+          unless task
             raise DatabaseNotSupported, "Rake tasks not supported by '#{adapter}' adapter"
           end
-          @tasks[key]
+          task.is_a?(String) ? task.constantize : task
         end
 
         def each_current_configuration(environment)
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index c05f0a8fbb..541165b3d1 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -60,6 +60,12 @@ module ActiveRecord
         args.concat(["--routines"])
         args.concat(["--skip-comments"])
         args.concat(Array(extra_flags)) if extra_flags
+
+        ignore_tables = ActiveRecord::SchemaDumper.ignore_tables
+        if ignore_tables.any?
+          args += ignore_tables.map { |table| "--ignore-table=#{configuration['database']}.#{table}" }
+        end
+
         args.concat(["#{configuration['database']}"])
 
         run_cmd("mysqldump", args, "dumping")
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index f1af90c1e8..7f1a768d8b 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -66,6 +66,12 @@ module ActiveRecord
             "--schema=#{part.strip}"
           end
         end
+
+        ignore_tables = ActiveRecord::SchemaDumper.ignore_tables
+        if ignore_tables.any?
+          args += ignore_tables.flat_map { |table| ["-T", table] }
+        end
+
         args << configuration["database"]
         run_cmd("pg_dump", args, "dumping")
         remove_sql_header_comments(filename)
diff --git a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
index 1f756c2979..7043d2f0c8 100644
--- a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
@@ -36,9 +36,18 @@ module ActiveRecord
       end
 
       def structure_dump(filename, extra_flags)
-        dbfile = configuration["database"]
-        flags = extra_flags.join(" ") if extra_flags
-        `sqlite3 #{flags} #{dbfile} .schema > #{filename}`
+        args = []
+        args.concat(Array(extra_flags)) if extra_flags
+        args << configuration["database"]
+
+        ignore_tables = ActiveRecord::SchemaDumper.ignore_tables
+        if ignore_tables.any?
+          condition = ignore_tables.map { |table| connection.quote_table_name(table) }.join(", ")
+          args << "SELECT sql FROM sqlite_master WHERE tbl_name NOT IN (#{condition}) ORDER BY tbl_name, type DESC, name"
+        else
+          args << ".schema"
+        end
+        run_cmd("sqlite3", args, filename)
       end
 
       def structure_load(filename, extra_flags)
@@ -56,6 +65,17 @@ module ActiveRecord
         def root
           @root
         end
+
+        def run_cmd(cmd, args, out)
+          fail run_cmd_error(cmd, args) unless Kernel.system(cmd, *args, out: out)
+        end
+
+        def run_cmd_error(cmd, args)
+          msg = "failed to execute:\n"
+          msg << "#{cmd} #{args.join(' ')}\n\n"
+          msg << "Please check the output above for any errors and make sure that `#{cmd}` is installed in your PATH and has proper permissions.\n\n"
+          msg
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/timestamp.rb b/activerecord/lib/active_record/timestamp.rb
index 09d8d1cdd4..55f3a194a9 100644
--- a/activerecord/lib/active_record/timestamp.rb
+++ b/activerecord/lib/active_record/timestamp.rb
@@ -43,8 +43,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :record_timestamps
-      self.record_timestamps = true
+      class_attribute :record_timestamps, default: true
     end
 
     def initialize_dup(other) # :nodoc:
diff --git a/activerecord/lib/rails/generators/active_record.rb b/activerecord/lib/rails/generators/active_record.rb
index 68fca44e3b..a79b8eafea 100644
--- a/activerecord/lib/rails/generators/active_record.rb
+++ b/activerecord/lib/rails/generators/active_record.rb
@@ -10,7 +10,7 @@ module ActiveRecord
 
       # Set the current directory as base for the inherited generators.
       def self.base_root
-        File.dirname(__FILE__)
+        __dir__
       end
     end
   end
diff --git a/activerecord/test/cases/adapter_test.rb b/activerecord/test/cases/adapter_test.rb
index 601d575c0e..a1fb6427f9 100644
--- a/activerecord/test/cases/adapter_test.rb
+++ b/activerecord/test/cases/adapter_test.rb
@@ -220,7 +220,7 @@ module ActiveRecord
       def test_select_all_with_legacy_binds
         post = Post.create!(title: "foo", body: "bar")
         expected = @connection.select_all("SELECT * FROM posts WHERE id = #{post.id}")
-        result = @connection.select_all("SELECT * FROM posts WHERE id = #{Arel::Nodes::BindParam.new.to_sql}", nil, [[nil, post.id]])
+        result = @connection.select_all("SELECT * FROM posts WHERE id = #{bind_param.to_sql}", nil, [[nil, post.id]])
         assert_equal expected.to_hash, result.to_hash
       end
     end
diff --git a/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb b/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb
index 8826ad7fd1..e4a6ed5482 100644
--- a/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb
@@ -48,7 +48,7 @@ class Mysql2CharsetCollationTest < ActiveRecord::Mysql2TestCase
 
   test "schema dump includes collation" do
     output = dump_table_schema("charset_collations")
-    assert_match %r{t.string\s+"string_ascii_bin",\s+collation: "ascii_bin"$}, output
-    assert_match %r{t.text\s+"text_ucs2_unicode_ci",\s+collation: "ucs2_unicode_ci"$}, output
+    assert_match %r{t\.string\s+"string_ascii_bin",\s+collation: "ascii_bin"$}, output
+    assert_match %r{t\.text\s+"text_ucs2_unicode_ci",\s+collation: "ucs2_unicode_ci"$}, output
   end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/json_test.rb b/activerecord/test/cases/adapters/mysql2/json_test.rb
index 6954006003..d311ffb703 100644
--- a/activerecord/test/cases/adapters/mysql2/json_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/json_test.rb
@@ -1,17 +1,11 @@
 require "cases/helper"
-require "support/schema_dumping_helper"
+require "cases/json_shared_test_cases"
 
 if ActiveRecord::Base.connection.supports_json?
   class Mysql2JSONTest < ActiveRecord::Mysql2TestCase
-    include SchemaDumpingHelper
+    include JSONSharedTestCases
     self.use_transactional_tests = false
 
-    class JsonDataType < ActiveRecord::Base
-      self.table_name = "json_data_type"
-
-      store_accessor :settings, :resolution
-    end
-
     def setup
       @connection = ActiveRecord::Base.connection
       begin
@@ -27,169 +21,9 @@ if ActiveRecord::Base.connection.supports_json?
       JsonDataType.reset_column_information
     end
 
-    def test_column
-      column = JsonDataType.columns_hash["payload"]
-      assert_equal :json, column.type
-      assert_equal "json", column.sql_type
-
-      type = JsonDataType.type_for_attribute("payload")
-      assert_not type.binary?
-    end
-
-    def test_change_table_supports_json
-      @connection.change_table("json_data_type") do |t|
-        t.json "users"
+    private
+      def column_type
+        :json
       end
-      JsonDataType.reset_column_information
-      column = JsonDataType.columns_hash["users"]
-      assert_equal :json, column.type
-    end
-
-    def test_schema_dumping
-      output = dump_table_schema("json_data_type")
-      assert_match(/t\.json\s+"settings"/, output)
-    end
-
-    def test_cast_value_on_write
-      x = JsonDataType.new payload: { "string" => "foo", :symbol => :bar }
-      assert_equal({ "string" => "foo", :symbol => :bar }, x.payload_before_type_cast)
-      assert_equal({ "string" => "foo", "symbol" => "bar" }, x.payload)
-      x.save
-      assert_equal({ "string" => "foo", "symbol" => "bar" }, x.reload.payload)
-    end
-
-    def test_type_cast_json
-      type = JsonDataType.type_for_attribute("payload")
-
-      data = "{\"a_key\":\"a_value\"}"
-      hash = type.deserialize(data)
-      assert_equal({ "a_key" => "a_value" }, hash)
-      assert_equal({ "a_key" => "a_value" }, type.deserialize(data))
-
-      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_rewrite
-      @connection.execute "insert into json_data_type (payload) VALUES ('{\"k\":\"v\"}')"
-      x = JsonDataType.first
-      x.payload = { '"a\'' => "b" }
-      assert x.save!
-    end
-
-    def test_select
-      @connection.execute "insert into json_data_type (payload) VALUES ('{\"k\":\"v\"}')"
-      x = JsonDataType.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]}')|
-      x = JsonDataType.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)"
-      x = JsonDataType.first
-      assert_nil(x.payload)
-    end
-
-    def test_select_array_json_value
-      @connection.execute %q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|
-      x = JsonDataType.first
-      assert_equal(["v0", { "k1" => "v1" }], x.payload)
-    end
-
-    def test_select_nil_json_after_create
-      json = JsonDataType.create(payload: nil)
-      x = JsonDataType.where(payload: nil).first
-      assert_equal(json, x)
-    end
-
-    def test_select_nil_json_after_update
-      json = JsonDataType.create(payload: "foo")
-      x = JsonDataType.where(payload: nil).first
-      assert_nil(x)
-
-      json.update_attributes payload: nil
-      x = JsonDataType.where(payload: nil).first
-      assert_equal(json.reload, x)
-    end
-
-    def test_rewrite_array_json_value
-      @connection.execute %q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|
-      x = JsonDataType.first
-      x.payload = ["v1", { "k2" => "v2" }, "v3"]
-      assert x.save!
-    end
-
-    def test_with_store_accessors
-      x = JsonDataType.new(resolution: "320×480")
-      assert_equal "320×480", x.resolution
-
-      x.save!
-      x = JsonDataType.first
-      assert_equal "320×480", x.resolution
-
-      x.resolution = "640×1136"
-      x.save!
-
-      x = JsonDataType.first
-      assert_equal "640×1136", x.resolution
-    end
-
-    def test_duplication_with_store_accessors
-      x = JsonDataType.new(resolution: "320×480")
-      assert_equal "320×480", x.resolution
-
-      y = x.dup
-      assert_equal "320×480", y.resolution
-    end
-
-    def test_yaml_round_trip_with_store_accessors
-      x = JsonDataType.new(resolution: "320×480")
-      assert_equal "320×480", x.resolution
-
-      y = YAML.load(YAML.dump(x))
-      assert_equal "320×480", y.resolution
-    end
-
-    def test_changes_in_place
-      json = JsonDataType.new
-      assert_not json.changed?
-
-      json.payload = { "one" => "two" }
-      assert json.changed?
-      assert json.payload_changed?
-
-      json.save!
-      assert_not json.changed?
-
-      json.payload["three"] = "four"
-      assert json.payload_changed?
-
-      json.save!
-      json.reload
-
-      assert_equal({ "one" => "two", "three" => "four" }, json.payload)
-      assert_not json.changed?
-    end
-
-    def test_assigning_string_literal
-      json = JsonDataType.create(payload: "foo")
-      assert_equal "foo", json.payload
-    end
-
-    def test_assigning_number
-      json = JsonDataType.create(payload: 1.234)
-      assert_equal 1.234, json.payload
-    end
-
-    def test_assigning_boolean
-      json = JsonDataType.create(payload: true)
-      assert_equal true, json.payload
-    end
   end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
index a0823be143..71dcfaa241 100644
--- a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
@@ -58,9 +58,9 @@ class Mysql2UnsignedTypeTest < ActiveRecord::Mysql2TestCase
 
   test "schema dump includes unsigned option" do
     schema = dump_table_schema "unsigned_types"
-    assert_match %r{t.integer\s+"unsigned_integer",\s+unsigned: true$}, schema
-    assert_match %r{t.bigint\s+"unsigned_bigint",\s+unsigned: true$}, schema
-    assert_match %r{t.float\s+"unsigned_float",\s+limit: 24,\s+unsigned: true$}, schema
-    assert_match %r{t.decimal\s+"unsigned_decimal",\s+precision: 10,\s+scale: 2,\s+unsigned: true$}, schema
+    assert_match %r{t\.integer\s+"unsigned_integer",\s+unsigned: true$}, schema
+    assert_match %r{t\.bigint\s+"unsigned_bigint",\s+unsigned: true$}, schema
+    assert_match %r{t\.float\s+"unsigned_float",\s+limit: 24,\s+unsigned: true$}, schema
+    assert_match %r{t\.decimal\s+"unsigned_decimal",\s+precision: 10,\s+scale: 2,\s+unsigned: true$}, schema
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/bytea_test.rb b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
index 99175e8091..539c90f0bc 100644
--- a/activerecord/test/cases/adapters/postgresql/bytea_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
@@ -96,7 +96,7 @@ class PostgresqlByteaTest < ActiveRecord::PostgreSQLTestCase
   end
 
   def test_write_binary
-    data = File.read(File.join(File.dirname(__FILE__), "..", "..", "..", "assets", "example.log"))
+    data = File.read(File.join(__dir__, "..", "..", "..", "assets", "example.log"))
     assert(data.size > 1)
     record = ByteaDataType.create(payload: data)
     assert_not record.new_record?
diff --git a/activerecord/test/cases/adapters/postgresql/collation_test.rb b/activerecord/test/cases/adapters/postgresql/collation_test.rb
index b39e298a5d..a603221d8f 100644
--- a/activerecord/test/cases/adapters/postgresql/collation_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/collation_test.rb
@@ -47,7 +47,7 @@ class PostgresqlCollationTest < ActiveRecord::PostgreSQLTestCase
 
   test "schema dump includes collation" do
     output = dump_table_schema("postgresql_collations")
-    assert_match %r{t.string\s+"string_c",\s+collation: "C"$}, output
-    assert_match %r{t.text\s+"text_posix",\s+collation: "POSIX"$}, output
+    assert_match %r{t\.string\s+"string_c",\s+collation: "C"$}, output
+    assert_match %r{t\.text\s+"text_posix",\s+collation: "POSIX"$}, output
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index c52d9e37cc..32afe331fa 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -31,15 +31,21 @@ module ActiveRecord
     end
 
     def test_encoding
-      assert_not_nil @connection.encoding
+      assert_queries(1) do
+        assert_not_nil @connection.encoding
+      end
     end
 
     def test_collation
-      assert_not_nil @connection.collation
+      assert_queries(1) do
+        assert_not_nil @connection.collation
+      end
     end
 
     def test_ctype
-      assert_not_nil @connection.ctype
+      assert_queries(1) do
+        assert_not_nil @connection.ctype
+      end
     end
 
     def test_default_client_min_messages
@@ -127,8 +133,8 @@ module ActiveRecord
 
     if ActiveRecord::Base.connection.prepared_statements
       def test_statement_key_is_logged
-        bind = Relation::QueryAttribute.new(nil, 1, Type::Value.new)
-        @connection.exec_query("SELECT $1::integer", "SQL", [bind], prepare: true)
+        binds = [bind_attribute(nil, 1)]
+        @connection.exec_query("SELECT $1::integer", "SQL", binds, prepare: true)
         name = @subscriber.payloads.last[:statement_name]
         assert name
         res = @connection.exec_query("EXPLAIN (FORMAT JSON) EXECUTE #{name}(1)")
diff --git a/activerecord/test/cases/adapters/postgresql/explain_test.rb b/activerecord/test/cases/adapters/postgresql/explain_test.rb
index 7493bce4fb..d79fbccf47 100644
--- a/activerecord/test/cases/adapters/postgresql/explain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/explain_test.rb
@@ -7,14 +7,14 @@ class PostgreSQLExplainTest < ActiveRecord::PostgreSQLTestCase
 
   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
+    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."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
     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 "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
     assert_match %(EXPLAIN for: SELECT "audit_logs".* FROM "audit_logs" WHERE "audit_logs"."developer_id" = 1), explain
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/json_test.rb b/activerecord/test/cases/adapters/postgresql/json_test.rb
index d4e627001c..4eeb563781 100644
--- a/activerecord/test/cases/adapters/postgresql/json_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/json_test.rb
@@ -1,14 +1,8 @@
 require "cases/helper"
-require "support/schema_dumping_helper"
+require "cases/json_shared_test_cases"
 
 module PostgresqlJSONSharedTestCases
-  include SchemaDumpingHelper
-
-  class JsonDataType < ActiveRecord::Base
-    self.table_name = "json_data_type"
-
-    store_accessor :settings, :resolution
-  end
+  include JSONSharedTestCases
 
   def setup
     @connection = ActiveRecord::Base.connection
@@ -28,16 +22,6 @@ module PostgresqlJSONSharedTestCases
     JsonDataType.reset_column_information
   end
 
-  def test_column
-    column = JsonDataType.columns_hash["payload"]
-    assert_equal column_type, column.type
-    assert_equal column_type.to_s, column.sql_type
-    assert_not column.array?
-
-    type = JsonDataType.type_for_attribute("payload")
-    assert_not type.binary?
-  end
-
   def test_default
     @connection.add_column "json_data_type", "permissions", column_type, default: { "users": "read", "posts": ["read", "write"] }
     JsonDataType.reset_column_information
@@ -48,34 +32,6 @@ module PostgresqlJSONSharedTestCases
     JsonDataType.reset_column_information
   end
 
-  def test_change_table_supports_json
-    @connection.transaction do
-      @connection.change_table("json_data_type") do |t|
-        t.public_send column_type, "users", default: "{}" # t.json 'users', default: '{}'
-      end
-      JsonDataType.reset_column_information
-      column = JsonDataType.columns_hash["users"]
-      assert_equal column_type, column.type
-
-      raise ActiveRecord::Rollback # reset the schema change
-    end
-  ensure
-    JsonDataType.reset_column_information
-  end
-
-  def test_schema_dumping
-    output = dump_table_schema("json_data_type")
-    assert_match(/t\.#{column_type.to_s}\s+"payload",\s+default: {}/, output)
-  end
-
-  def test_cast_value_on_write
-    x = JsonDataType.new payload: { "string" => "foo", :symbol => :bar }
-    assert_equal({ "string" => "foo", :symbol => :bar }, x.payload_before_type_cast)
-    assert_equal({ "string" => "foo", "symbol" => "bar" }, x.payload)
-    x.save
-    assert_equal({ "string" => "foo", "symbol" => "bar" }, x.reload.payload)
-  end
-
   def test_deserialize_with_array
     x = JsonDataType.new(objects: ["foo" => "bar"])
     assert_equal ["foo" => "bar"], x.objects
@@ -84,140 +40,6 @@ module PostgresqlJSONSharedTestCases
     x.reload
     assert_equal ["foo" => "bar"], x.objects
   end
-
-  def test_type_cast_json
-    type = JsonDataType.type_for_attribute("payload")
-
-    data = "{\"a_key\":\"a_value\"}"
-    hash = type.deserialize(data)
-    assert_equal({ "a_key" => "a_value" }, hash)
-    assert_equal({ "a_key" => "a_value" }, type.deserialize(data))
-
-    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_rewrite
-    @connection.execute "insert into json_data_type (payload) VALUES ('{\"k\":\"v\"}')"
-    x = JsonDataType.first
-    x.payload = { '"a\'' => "b" }
-    assert x.save!
-  end
-
-  def test_select
-    @connection.execute "insert into json_data_type (payload) VALUES ('{\"k\":\"v\"}')"
-    x = JsonDataType.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]}')|
-    x = JsonDataType.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)"
-    x = JsonDataType.first
-    assert_nil(x.payload)
-  end
-
-  def test_select_nil_json_after_create
-    json = JsonDataType.create(payload: nil)
-    x = JsonDataType.where(payload: nil).first
-    assert_equal(json, x)
-  end
-
-  def test_select_nil_json_after_update
-    json = JsonDataType.create(payload: "foo")
-    x = JsonDataType.where(payload: nil).first
-    assert_nil(x)
-
-    json.update_attributes payload: nil
-    x = JsonDataType.where(payload: nil).first
-    assert_equal(json.reload, x)
-  end
-
-  def test_select_array_json_value
-    @connection.execute %q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|
-    x = JsonDataType.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"}]')|
-    x = JsonDataType.first
-    x.payload = ["v1", { "k2" => "v2" }, "v3"]
-    assert x.save!
-  end
-
-  def test_with_store_accessors
-    x = JsonDataType.new(resolution: "320×480")
-    assert_equal "320×480", x.resolution
-
-    x.save!
-    x = JsonDataType.first
-    assert_equal "320×480", x.resolution
-
-    x.resolution = "640×1136"
-    x.save!
-
-    x = JsonDataType.first
-    assert_equal "640×1136", x.resolution
-  end
-
-  def test_duplication_with_store_accessors
-    x = JsonDataType.new(resolution: "320×480")
-    assert_equal "320×480", x.resolution
-
-    y = x.dup
-    assert_equal "320×480", y.resolution
-  end
-
-  def test_yaml_round_trip_with_store_accessors
-    x = JsonDataType.new(resolution: "320×480")
-    assert_equal "320×480", x.resolution
-
-    y = YAML.load(YAML.dump(x))
-    assert_equal "320×480", y.resolution
-  end
-
-  def test_changes_in_place
-    json = JsonDataType.new
-    assert_not json.changed?
-
-    json.payload = { "one" => "two" }
-    assert json.changed?
-    assert json.payload_changed?
-
-    json.save!
-    assert_not json.changed?
-
-    json.payload["three"] = "four"
-    assert json.payload_changed?
-
-    json.save!
-    json.reload
-
-    assert_equal({ "one" => "two", "three" => "four" }, json.payload)
-    assert_not json.changed?
-  end
-
-  def test_assigning_string_literal
-    json = JsonDataType.create(payload: "foo")
-    assert_equal "foo", json.payload
-  end
-
-  def test_assigning_number
-    json = JsonDataType.create(payload: 1.234)
-    assert_equal 1.234, json.payload
-  end
-
-  def test_assigning_boolean
-    json = JsonDataType.create(payload: true)
-    assert_equal true, json.payload
-  end
 end
 
 class PostgresqlJSONTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index 003e6e62e7..bfc763e1ef 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -202,8 +202,8 @@ module ActiveRecord
             string = @connection.quote("foo")
             @connection.exec_query("INSERT INTO ex (id, data) VALUES (1, #{string})")
 
-            bind = Relation::QueryAttribute.new("id", 1, Type::Value.new)
-            result = @connection.exec_query("SELECT id, data FROM ex WHERE id = $1", nil, [bind])
+            binds = [bind_attribute("id", 1)]
+            result = @connection.exec_query("SELECT id, data FROM ex WHERE id = $1", nil, binds)
 
             assert_equal 1, result.rows.length
             assert_equal 2, result.columns.length
@@ -217,8 +217,8 @@ module ActiveRecord
             string = @connection.quote("foo")
             @connection.exec_query("INSERT INTO ex (id, data) VALUES (1, #{string})")
 
-            bind = Relation::QueryAttribute.new("id", "1-fuu", Type::Integer.new)
-            result = @connection.exec_query("SELECT id, data FROM ex WHERE id = $1", nil, [bind])
+            binds = [bind_attribute("id", "1-fuu", Type::Integer.new)]
+            result = @connection.exec_query("SELECT id, data FROM ex WHERE id = $1", nil, binds)
 
             assert_equal 1, result.rows.length
             assert_equal 2, result.columns.length
@@ -346,7 +346,7 @@ module ActiveRecord
           @connection.select_all "SELECT NULL::anyelement"
           @connection.select_all "SELECT NULL::anyelement"
         }
-        assert_match(/\Aunknown OID \d+: failed to recognize type of 'anyelement'. It will be treated as String.\n\z/, warning)
+        assert_match(/\Aunknown OID \d+: failed to recognize type of 'anyelement'\. It will be treated as String\.\n\z/, warning)
       ensure
         reset_connection
       end
diff --git a/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb b/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb
index f6a07da85f..f86a76e08a 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb
@@ -68,24 +68,13 @@ class SchemaAuthorizationTest < ActiveRecord::PostgreSQLTestCase
         USERS.each do |u|
           @connection.clear_cache!
           set_session_auth u
-          assert_equal u, @connection.select_value("SELECT name FROM #{TABLE_NAME} WHERE id = $1", "SQL", [bind_param(1)])
+          assert_equal u, @connection.select_value("SELECT name FROM #{TABLE_NAME} WHERE id = $1", "SQL", [bind_attribute("id", 1)])
           set_session_auth
         end
       end
     end
   end
 
-  def test_schema_uniqueness
-    assert_nothing_raised do
-      set_session_auth
-      USERS.each do |u|
-        set_session_auth u
-        assert_equal u, @connection.select_value("SELECT name FROM #{TABLE_NAME} WHERE id = 1")
-        set_session_auth
-      end
-    end
-  end
-
   def test_sequence_schema_caching
     assert_nothing_raised do
       USERS.each do |u|
@@ -112,8 +101,4 @@ class SchemaAuthorizationTest < ActiveRecord::PostgreSQLTestCase
     def set_session_auth(auth = nil)
       @connection.session_auth = auth || "default"
     end
-
-    def bind_param(value)
-      ActiveRecord::Relation::QueryAttribute.new(nil, value, ActiveRecord::Type::Value.new)
-    end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index 75e30e4fe9..f6b957476b 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -169,17 +169,17 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
 
   def test_raise_wrapped_exception_on_bad_prepare
     assert_raises(ActiveRecord::StatementInvalid) do
-      @connection.exec_query "select * from developers where id = ?", "sql", [bind_param(1)]
+      @connection.exec_query "select * from developers where id = ?", "sql", [bind_attribute("id", 1)]
     end
   end
 
   if ActiveRecord::Base.connection.prepared_statements
     def test_schema_change_with_prepared_stmt
       altered = false
-      @connection.exec_query "select * from developers where id = $1", "sql", [bind_param(1)]
+      @connection.exec_query "select * from developers where id = $1", "sql", [bind_attribute("id", 1)]
       @connection.exec_query "alter table developers add column zomg int", "sql", []
       altered = true
-      @connection.exec_query "select * from developers where id = $1", "sql", [bind_param(1)]
+      @connection.exec_query "select * from developers where id = $1", "sql", [bind_attribute("id", 1)]
     ensure
       # We are not using DROP COLUMN IF EXISTS because that syntax is only
       # supported by pg 9.X
@@ -467,10 +467,6 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
       assert_equal this_index_column, this_index.columns[0]
       assert_equal this_index_name, this_index.name
     end
-
-    def bind_param(value)
-      ActiveRecord::Relation::QueryAttribute.new(nil, value, ActiveRecord::Type::Value.new)
-    end
 end
 
 class SchemaForeignKeyTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/sqlite3/collation_test.rb b/activerecord/test/cases/adapters/sqlite3/collation_test.rb
index 28e8f12c18..dd88ed3656 100644
--- a/activerecord/test/cases/adapters/sqlite3/collation_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/collation_test.rb
@@ -47,7 +47,7 @@ class SQLite3CollationTest < ActiveRecord::SQLite3TestCase
 
   test "schema dump includes collation" do
     output = dump_table_schema("collation_table_sqlite3")
-    assert_match %r{t.string\s+"string_nocase",\s+collation: "NOCASE"$}, output
-    assert_match %r{t.text\s+"text_rtrim",\s+collation: "RTRIM"$}, output
+    assert_match %r{t\.string\s+"string_nocase",\s+collation: "NOCASE"$}, output
+    assert_match %r{t\.text\s+"text_rtrim",\s+collation: "RTRIM"$}, output
   end
 end
diff --git a/activerecord/test/cases/adapters/sqlite3/explain_test.rb b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
index 128acb79cf..29d97ae78c 100644
--- a/activerecord/test/cases/adapters/sqlite3/explain_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
@@ -7,13 +7,13 @@ class SQLite3ExplainTest < ActiveRecord::SQLite3TestCase
 
   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 %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
     assert_match(/(SEARCH )?TABLE developers 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 %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 %(EXPLAIN for: SELECT "audit_logs".* FROM "audit_logs" WHERE "audit_logs"."developer_id" = 1), explain
     assert_match(/(SCAN )?TABLE audit_logs/, explain)
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index 2179d1294c..9a812e325e 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -66,11 +66,11 @@ module ActiveRecord
 
       def test_exec_insert
         with_example_table do
-          vals = [Relation::QueryAttribute.new("number", 10, Type::Value.new)]
-          @conn.exec_insert("insert into ex (number) VALUES (?)", "SQL", vals)
+          binds = [bind_attribute("number", 10)]
+          @conn.exec_insert("insert into ex (number) VALUES (?)", "SQL", binds)
 
           result = @conn.exec_query(
-            "select number from ex where number = ?", "SQL", vals)
+            "select number from ex where number = ?", "SQL", binds)
 
           assert_equal 1, result.rows.length
           assert_equal 10, result.rows.first.first
@@ -134,7 +134,7 @@ module ActiveRecord
         with_example_table "id int, data string" do
           @conn.exec_query('INSERT INTO ex (id, data) VALUES (1, "foo")')
           result = @conn.exec_query(
-            "SELECT id, data FROM ex WHERE id = ?", nil, [Relation::QueryAttribute.new(nil, 1, Type::Value.new)])
+            "SELECT id, data FROM ex WHERE id = ?", nil, [bind_attribute("id", 1)])
 
           assert_equal 1, result.rows.length
           assert_equal 2, result.columns.length
@@ -148,7 +148,7 @@ module ActiveRecord
           @conn.exec_query('INSERT INTO ex (id, data) VALUES (1, "foo")')
 
           result = @conn.exec_query(
-            "SELECT id, data FROM ex WHERE id = ?", nil, [Relation::QueryAttribute.new("id", "1-fuu", Type::Integer.new)])
+            "SELECT id, data FROM ex WHERE id = ?", nil, [bind_attribute("id", "1-fuu", Type::Integer.new)])
 
           assert_equal 1, result.rows.length
           assert_equal 2, result.columns.length
diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 5b08ba1358..c8b26232b6 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -136,6 +136,24 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     assert_equal david, ship.developer
   end
 
+  def test_default_with_lambda
+    model = Class.new(ActiveRecord::Base) do
+      self.table_name = "ships"
+      def self.name; "Temp"; end
+      belongs_to :developer, default: -> { default_developer }
+
+      def default_developer
+        Developer.first
+      end
+    end
+
+    ship = model.create!
+    assert_equal developers(:david), ship.developer
+
+    ship = model.create!(developer: developers(:jamis))
+    assert_equal developers(:jamis), ship.developer
+  end
+
   def test_default_scope_on_relations_is_not_cached
     counter = 0
 
diff --git a/activerecord/test/cases/associations/callbacks_test.rb b/activerecord/test/cases/associations/callbacks_test.rb
index 5fd2411f6f..f9d1e44595 100644
--- a/activerecord/test/cases/associations/callbacks_test.rb
+++ b/activerecord/test/cases/associations/callbacks_test.rb
@@ -7,7 +7,7 @@ require "models/computer"
 require "models/company"
 
 class AssociationCallbacksTest < ActiveRecord::TestCase
-  fixtures :posts, :authors, :projects, :developers
+  fixtures :posts, :authors, :author_addresses, :projects, :developers
 
   def setup
     @david = authors(:david)
@@ -128,7 +128,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     assert ar.developers_log.empty?
     alice = Developer.new(name: "alice")
     ar.developers_with_callbacks << alice
-    assert_equal"after_adding#{alice.id}", ar.developers_log.last
+    assert_equal "after_adding#{alice.id}", ar.developers_log.last
 
     bob = ar.developers_with_callbacks.create(name: "bob")
     assert_equal "after_adding#{bob.id}", ar.developers_log.last
diff --git a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
index ddb5c7a4aa..3638c87968 100644
--- a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
+++ b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
@@ -12,7 +12,7 @@ require "models/vertex"
 require "models/edge"
 
 class CascadedEagerLoadingTest < ActiveRecord::TestCase
-  fixtures :authors, :mixins, :companies, :posts, :topics, :accounts, :comments,
+  fixtures :authors, :author_addresses, :mixins, :companies, :posts, :topics, :accounts, :comments,
            :categorizations, :people, :categories, :edges, :vertices
 
   def test_eager_association_loading_with_cascaded_two_levels
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 11f4aae5b3..4271a09c9b 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1094,12 +1094,6 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal authors(:david), assert_no_queries { posts[0].author }
 
     posts = assert_queries(2) do
-      Post.all.merge!(select: "distinct posts.*", includes: :author, joins: [:comments], where: "comments.body like 'Thank you%'", order: "posts.id").to_a
-    end
-    assert_equal [posts(:welcome)], posts
-    assert_equal authors(:david), assert_no_queries { posts[0].author }
-
-    posts = assert_queries(2) do
       Post.all.merge!(includes: :author, joins: { taggings: :tag }, where: "tags.name = 'General'", order: "posts.id").to_a
     end
     assert_equal posts(:welcome, :thinking), posts
@@ -1363,6 +1357,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_nothing_raised do
       authors(:david).essays.includes(:writer).any?
       authors(:david).essays.includes(:writer).exists?
+      authors(:david).essays.includes(:owner).where("name IS NOT NULL").exists?
     end
   end
 
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 8060790594..4bf1b5bcd5 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
@@ -954,7 +954,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     assert_not_nil Developer._reflections["shared_computers"]
     # Checking the fixture for named association is important here, because it's the only way
     # we've been able to reproduce this bug
-    assert_not_nil File.read(File.expand_path("../../../fixtures/developers.yml", __FILE__)).index("shared_computers")
+    assert_not_nil File.read(File.expand_path("../../fixtures/developers.yml", __dir__)).index("shared_computers")
     assert_equal developers(:david).shared_computers.first, computers(:laptop)
   end
 
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 6ba738ed6c..4ce1257faa 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -40,7 +40,7 @@ require "models/zine"
 require "models/interest"
 
 class HasManyAssociationsTestForReorderWithJoinDependency < ActiveRecord::TestCase
-  fixtures :authors, :posts, :comments
+  fixtures :authors, :author_addresses, :posts, :comments
 
   def test_should_generate_valid_sql
     author = authors(:david)
@@ -51,7 +51,7 @@ class HasManyAssociationsTestForReorderWithJoinDependency < ActiveRecord::TestCa
 end
 
 class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
-  fixtures :authors, :essays, :subscribers, :subscriptions, :people
+  fixtures :authors, :author_addresses, :essays, :subscribers, :subscriptions, :people
 
   def test_custom_primary_key_on_new_record_should_fetch_with_query
     subscriber = Subscriber.new(nick: "webster132")
@@ -100,7 +100,7 @@ end
 
 class HasManyAssociationsTest < ActiveRecord::TestCase
   fixtures :accounts, :categories, :companies, :developers, :projects,
-           :developers_projects, :topics, :authors, :comments,
+           :developers_projects, :topics, :authors, :author_addresses, :comments,
            :posts, :readers, :taggings, :cars, :jobs, :tags,
            :categorizations, :zines, :interests
 
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 ea52fb5a67..9156f6d57a 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -64,10 +64,6 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
                  club1.members.sort_by(&:id)
   end
 
-  def make_model(name)
-    Class.new(ActiveRecord::Base) { define_singleton_method(:name) { name } }
-  end
-
   def test_ordered_has_many_through
     person_prime = Class.new(ActiveRecord::Base) do
       def self.name; "Person"; end
@@ -152,20 +148,6 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert after_destroy_called, "after destroy should be called"
   end
 
-  def make_no_pk_hm_t
-    lesson = make_model "Lesson"
-    student = make_model "Student"
-
-    lesson_student = make_model "LessonStudent"
-    lesson_student.table_name = "lessons_students"
-
-    lesson_student.belongs_to :lesson, anonymous_class: lesson
-    lesson_student.belongs_to :student, anonymous_class: student
-    lesson.has_many :lesson_students, anonymous_class: lesson_student
-    lesson.has_many :students, through: :lesson_students, anonymous_class: student
-    [lesson, lesson_student, student]
-  end
-
   def test_pk_is_not_required_for_join
     post  = Post.includes(:scategories).first
     post2 = Post.includes(:categories).first
@@ -1252,4 +1234,23 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       )
     end
   end
+
+  private
+    def make_model(name)
+      Class.new(ActiveRecord::Base) { define_singleton_method(:name) { name } }
+    end
+
+    def make_no_pk_hm_t
+      lesson = make_model "Lesson"
+      student = make_model "Student"
+
+      lesson_student = make_model "LessonStudent"
+      lesson_student.table_name = "lessons_students"
+
+      lesson_student.belongs_to :lesson, anonymous_class: lesson
+      lesson_student.belongs_to :student, anonymous_class: student
+      lesson.has_many :lesson_students, anonymous_class: lesson_student
+      lesson.has_many :students, through: :lesson_students, anonymous_class: student
+      [lesson, lesson_student, student]
+    end
 end
diff --git a/activerecord/test/cases/associations/has_one_through_associations_test.rb b/activerecord/test/cases/associations/has_one_through_associations_test.rb
index 38a729d2d4..28b883586d 100644
--- a/activerecord/test/cases/associations/has_one_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_through_associations_test.rb
@@ -23,7 +23,7 @@ require "models/customer_carrier"
 
 class HasOneThroughAssociationsTest < ActiveRecord::TestCase
   fixtures :member_types, :members, :clubs, :memberships, :sponsors, :organizations, :minivans,
-           :dashboards, :speedometers, :authors, :posts, :comments, :categories, :essays, :owners
+           :dashboards, :speedometers, :authors, :author_addresses, :posts, :comments, :categories, :essays, :owners
 
   def setup
     @member = members(:groucho)
diff --git a/activerecord/test/cases/associations/inner_join_association_test.rb b/activerecord/test/cases/associations/inner_join_association_test.rb
index 7414869c8f..ddf5bc6f0b 100644
--- a/activerecord/test/cases/associations/inner_join_association_test.rb
+++ b/activerecord/test/cases/associations/inner_join_association_test.rb
@@ -10,7 +10,7 @@ require "models/tagging"
 require "models/tag"
 
 class InnerJoinAssociationTest < ActiveRecord::TestCase
-  fixtures :authors, :essays, :posts, :comments, :categories, :categories_posts, :categorizations,
+  fixtures :authors, :author_addresses, :essays, :posts, :comments, :categories, :categories_posts, :categorizations,
            :taggings, :tags
 
   def test_construct_finder_sql_applies_aliases_tables_on_association_conditions
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index 287b3e9ebc..467cc73ecd 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -651,20 +651,6 @@ class InversePolymorphicBelongsToTests < ActiveRecord::TestCase
     assert_equal face.description, new_man.polymorphic_face.description, "Description of face should be the same after changes to replaced-parent-owned instance"
   end
 
-  def test_child_instance_should_be_shared_with_replaced_via_method_parent
-    face = faces(:confused)
-    new_man = Man.new
-
-    assert_not_nil face.polymorphic_man
-    face.polymorphic_man = new_man
-
-    assert_equal face.description, new_man.polymorphic_face.description, "Description of face should be the same before changes to parent instance"
-    face.description = "Bongo"
-    assert_equal face.description, new_man.polymorphic_face.description, "Description of face should be the same after changes to parent instance"
-    new_man.polymorphic_face.description = "Mungo"
-    assert_equal face.description, new_man.polymorphic_face.description, "Description of face should be the same after changes to replaced-parent-owned instance"
-  end
-
   def test_inversed_instance_should_not_be_reloaded_after_stale_state_changed
     new_man = Man.new
     face = Face.new
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index a4345f3857..c078cef064 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -19,7 +19,7 @@ require "models/car"
 class AssociationsJoinModelTest < ActiveRecord::TestCase
   self.use_transactional_tests = false unless supports_savepoints?
 
-  fixtures :posts, :authors, :categories, :categorizations, :comments, :tags, :taggings, :author_favorites, :vertices, :items, :books,
+  fixtures :posts, :authors, :author_addresses, :categories, :categorizations, :comments, :tags, :taggings, :author_favorites, :vertices, :items, :books,
     # Reload edges table from fixtures as otherwise repeated test was failing
     :edges
 
diff --git a/activerecord/test/cases/associations/left_outer_join_association_test.rb b/activerecord/test/cases/associations/left_outer_join_association_test.rb
index 42dbbad1c8..6d3757f467 100644
--- a/activerecord/test/cases/associations/left_outer_join_association_test.rb
+++ b/activerecord/test/cases/associations/left_outer_join_association_test.rb
@@ -7,7 +7,7 @@ require "models/categorization"
 require "models/person"
 
 class LeftOuterJoinAssociationTest < ActiveRecord::TestCase
-  fixtures :authors, :essays, :posts, :comments, :categorizations, :people
+  fixtures :authors, :author_addresses, :essays, :posts, :comments, :categorizations, :people
 
   def test_construct_finder_sql_applies_aliases_tables_on_association_conditions
     result = Author.left_outer_joins(:thinking_posts, :welcome_posts).to_a
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index dc26f6a383..67ff7355b3 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -24,7 +24,7 @@ require "models/membership"
 require "models/essay"
 
 class NestedThroughAssociationsTest < ActiveRecord::TestCase
-  fixtures :authors, :books, :posts, :subscriptions, :subscribers, :tags, :taggings,
+  fixtures :authors, :author_addresses, :books, :posts, :subscriptions, :subscribers, :tags, :taggings,
            :people, :readers, :references, :jobs, :ratings, :comments, :members, :member_details,
            :member_types, :sponsors, :clubs, :organizations, :categories, :categories_posts,
            :categorizations, :memberships, :essays
diff --git a/activerecord/test/cases/associations_test.rb b/activerecord/test/cases/associations_test.rb
index 26056f6f63..4ab690bfc6 100644
--- a/activerecord/test/cases/associations_test.rb
+++ b/activerecord/test/cases/associations_test.rb
@@ -22,7 +22,7 @@ require "models/interest"
 
 class AssociationsTest < ActiveRecord::TestCase
   fixtures :accounts, :companies, :developers, :projects, :developers_projects,
-           :computers, :people, :readers, :authors, :author_favorites
+           :computers, :people, :readers, :authors, :author_addresses, :author_favorites
 
   def test_eager_loading_should_not_change_count_of_children
     liquid = Liquid.create(name: "salty")
@@ -111,7 +111,7 @@ class AssociationsTest < ActiveRecord::TestCase
 end
 
 class AssociationProxyTest < ActiveRecord::TestCase
-  fixtures :authors, :posts, :categorizations, :categories, :developers, :projects, :developers_projects
+  fixtures :authors, :author_addresses, :posts, :categorizations, :categories, :developers, :projects, :developers_projects
 
   def test_push_does_not_load_target
     david = authors(:david)
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 8efbc41da9..15c253890b 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -64,7 +64,7 @@ class LintTest < ActiveRecord::TestCase
 end
 
 class BasicsTest < ActiveRecord::TestCase
-  fixtures :topics, :companies, :developers, :projects, :computers, :accounts, :minimalistics, "warehouse-things", :authors, :categorizations, :categories, :posts
+  fixtures :topics, :companies, :developers, :projects, :computers, :accounts, :minimalistics, "warehouse-things", :authors, :author_addresses, :categorizations, :categories, :posts
 
   def test_column_names_are_escaped
     conn      = ActiveRecord::Base.connection
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index 1a54c02fac..fbc3fbb44f 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -143,7 +143,7 @@ class EachTest < ActiveRecord::TestCase
 
   def test_find_in_batches_should_quote_batch_order
     c = Post.connection
-    assert_sql(/ORDER BY #{c.quote_table_name('posts')}.#{c.quote_column_name('id')}/) do
+    assert_sql(/ORDER BY #{c.quote_table_name('posts')}\.#{c.quote_column_name('id')}/) do
       Post.find_in_batches(batch_size: 1) do |batch|
         assert_kind_of Array, batch
         assert_kind_of Post, batch.first
@@ -408,7 +408,7 @@ class EachTest < ActiveRecord::TestCase
 
   def test_in_batches_should_quote_batch_order
     c = Post.connection
-    assert_sql(/ORDER BY #{c.quote_table_name('posts')}.#{c.quote_column_name('id')}/) do
+    assert_sql(/ORDER BY #{c.quote_table_name('posts')}\.#{c.quote_column_name('id')}/) do
       Post.in_batches(of: 1) do |relation|
         assert_kind_of ActiveRecord::Relation, relation
         assert_kind_of Post, relation.first
diff --git a/activerecord/test/cases/bind_parameter_test.rb b/activerecord/test/cases/bind_parameter_test.rb
index a0f83df80b..5af44c27eb 100644
--- a/activerecord/test/cases/bind_parameter_test.rb
+++ b/activerecord/test/cases/bind_parameter_test.rb
@@ -3,11 +3,10 @@ require "models/topic"
 require "models/author"
 require "models/post"
 
-if ActiveRecord::Base.connection.supports_statement_cache? &&
-   ActiveRecord::Base.connection.prepared_statements
+if ActiveRecord::Base.connection.prepared_statements
   module ActiveRecord
     class BindParameterTest < ActiveRecord::TestCase
-      fixtures :topics, :authors, :posts
+      fixtures :topics, :authors, :author_addresses, :posts
 
       class LogListener
         attr_accessor :calls
@@ -40,9 +39,8 @@ if ActiveRecord::Base.connection.supports_statement_cache? &&
       end
 
       def test_binds_are_logged
-        sub   = Arel::Nodes::BindParam.new
-        binds = [Relation::QueryAttribute.new("id", 1, Type::Value.new)]
-        sql   = "select * from topics where id = #{sub.to_sql}"
+        binds = [bind_attribute("id", 1)]
+        sql   = "select * from topics where id = #{bind_param.to_sql}"
 
         @connection.exec_query(sql, "SQL", binds)
 
@@ -57,7 +55,7 @@ if ActiveRecord::Base.connection.supports_statement_cache? &&
       end
 
       def test_logs_binds_after_type_cast
-        binds = [Relation::QueryAttribute.new("id", "10", Type::Integer.new)]
+        binds = [bind_attribute("id", "10", Type::Integer.new)]
         assert_logs_binds(binds)
       end
 
@@ -66,6 +64,10 @@ if ActiveRecord::Base.connection.supports_statement_cache? &&
         assert_logs_binds(binds)
       end
 
+      def test_deprecate_supports_statement_cache
+        assert_deprecated { ActiveRecord::Base.connection.supports_statement_cache? }
+      end
+
       private
         def assert_logs_binds(binds)
           payload = {
diff --git a/activerecord/test/cases/cache_key_test.rb b/activerecord/test/cases/cache_key_test.rb
index 2c6a38ec35..7b8264e6e8 100644
--- a/activerecord/test/cases/cache_key_test.rb
+++ b/activerecord/test/cases/cache_key_test.rb
@@ -4,15 +4,23 @@ module ActiveRecord
   class CacheKeyTest < ActiveRecord::TestCase
     self.use_transactional_tests = false
 
-    class CacheMe < ActiveRecord::Base; end
+    class CacheMe < ActiveRecord::Base
+      self.cache_versioning = false
+    end
+
+    class CacheMeWithVersion < ActiveRecord::Base
+      self.cache_versioning = true
+    end
 
     setup do
       @connection = ActiveRecord::Base.connection
-      @connection.create_table(:cache_mes) { |t| t.timestamps }
+      @connection.create_table(:cache_mes, force: true) { |t| t.timestamps }
+      @connection.create_table(:cache_me_with_versions, force: true) { |t| t.timestamps }
     end
 
     teardown do
       @connection.drop_table :cache_mes, if_exists: true
+      @connection.drop_table :cache_me_with_versions, if_exists: true
     end
 
     test "cache_key format is not too precise" do
@@ -21,5 +29,23 @@ module ActiveRecord
 
       assert_equal key, record.reload.cache_key
     end
+
+    test "cache_key has no version when versioning is on" do
+      record = CacheMeWithVersion.create
+      assert_equal "active_record/cache_key_test/cache_me_with_versions/#{record.id}", record.cache_key
+    end
+
+    test "cache_version is only there when versioning is on" do
+      assert CacheMeWithVersion.create.cache_version.present?
+      assert_not CacheMe.create.cache_version.present?
+    end
+
+    test "cache_key_with_version always has both key and version" do
+      r1 = CacheMeWithVersion.create
+      assert_equal "active_record/cache_key_test/cache_me_with_versions/#{r1.id}-#{r1.updated_at.to_s(:usec)}", r1.cache_key_with_version
+
+      r2 = CacheMe.create
+      assert_equal "active_record/cache_key_test/cache_mes/#{r2.id}-#{r2.updated_at.to_s(:usec)}", r2.cache_key_with_version
+    end
   end
 end
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 3214d778d4..93f8ab18c2 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -809,4 +809,16 @@ class CalculationsTest < ActiveRecord::TestCase
   def test_group_by_attribute_with_custom_type
     assert_equal({ "proposed" => 2, "published" => 2 }, Book.group(:status).count)
   end
+
+  def test_deprecate_count_with_block_and_column_name
+    assert_deprecated do
+      assert_equal 6, Account.count(:firm_id) { true }
+    end
+  end
+
+  def test_deprecate_sum_with_block_and_column_name
+    assert_deprecated do
+      assert_equal 6, Account.sum(:firm_id) { 1 }
+    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 681399c8bb..2a71f08d90 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -9,6 +9,17 @@ module ActiveRecord
         @pool = @handler.establish_connection(ActiveRecord::Base.configurations["arunit"])
       end
 
+      def test_default_env_fall_back_to_default_env_when_rails_env_or_rack_env_is_empty_string
+        original_rails_env = ENV["RAILS_ENV"]
+        original_rack_env  = ENV["RACK_ENV"]
+        ENV["RAILS_ENV"]   = ENV["RACK_ENV"] = ""
+
+        assert_equal "default_env", ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
+      ensure
+        ENV["RAILS_ENV"] = original_rails_env
+        ENV["RACK_ENV"]  = original_rack_env
+      end
+
       def test_establish_connection_uses_spec_name
         config = { "readonly" => { "adapter" => "sqlite3" } }
         resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(config)
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index b7641fcf32..db3da53487 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -1,8 +1,9 @@
 require "cases/helper"
+require "models/author"
 require "models/book"
 
 class EnumTest < ActiveRecord::TestCase
-  fixtures :books
+  fixtures :books, :authors
 
   setup do
     @book = books(:awdr)
@@ -37,6 +38,8 @@ class EnumTest < ActiveRecord::TestCase
     assert_equal @book, Book.author_visibility_visible.first
     assert_equal @book, Book.illustrator_visibility_visible.first
     assert_equal @book, Book.medium_to_read.first
+    assert_equal books(:ddd), Book.forgotten.first
+    assert_equal books(:rfr), authors(:david).unpublished_books.first
   end
 
   test "find via where with values" do
diff --git a/activerecord/test/cases/explain_test.rb b/activerecord/test/cases/explain_test.rb
index 86fe90ae51..4f6bd9327c 100644
--- a/activerecord/test/cases/explain_test.rb
+++ b/activerecord/test/cases/explain_test.rb
@@ -47,7 +47,7 @@ if ActiveRecord::Base.connection.supports_explain?
 
     def test_exec_explain_with_binds
       sqls    = %w(foo bar)
-      binds   = [[bind_param("wadus", 1)], [bind_param("chaflan", 2)]]
+      binds   = [[bind_attribute("wadus", 1)], [bind_attribute("chaflan", 2)]]
       queries = sqls.zip(binds)
 
       stub_explain_for_query_plans(["query plan foo\n", "query plan bar\n"]) do
@@ -79,9 +79,5 @@ if ActiveRecord::Base.connection.supports_explain?
           yield
         end
       end
-
-      def bind_param(name, value)
-        ActiveRecord::Relation::QueryAttribute.new(name, value, ActiveRecord::Type::Value.new)
-      end
   end
 end
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index a7b6333010..4837a169fa 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -743,7 +743,6 @@ class FinderTest < ActiveRecord::TestCase
     assert Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: false).find(1)
     assert_raise(ActiveRecord::RecordNotFound) { Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: true).find(1) }
     assert_raise(ActiveRecord::RecordNotFound) { Topic.where(author_name: "David", title: "HHC", replies_count: 1, approved: false).find(1) }
-    assert_raise(ActiveRecord::RecordNotFound) { Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: true).find(1) }
   end
 
   def test_condition_interpolation
diff --git a/activerecord/test/cases/fixtures_test.rb b/activerecord/test/cases/fixtures_test.rb
index 4137a1e955..a0a6d3c7ef 100644
--- a/activerecord/test/cases/fixtures_test.rb
+++ b/activerecord/test/cases/fixtures_test.rb
@@ -784,7 +784,7 @@ end
 
 class FasterFixturesTest < ActiveRecord::TestCase
   self.use_transactional_tests = false
-  fixtures :categories, :authors
+  fixtures :categories, :authors, :author_addresses
 
   def load_extra_fixture(name)
     fixture = create_fixtures(name).first
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index e570e9ac1d..b4bbdc6dad 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -316,7 +316,7 @@ class InheritanceTest < ActiveRecord::TestCase
   end
 
   def test_new_with_autoload_paths
-    path = File.expand_path("../../models/autoloadable", __FILE__)
+    path = File.expand_path("../models/autoloadable", __dir__)
     ActiveSupport::Dependencies.autoload_paths << path
 
     firm = Company.new(type: "ExtraFirm")
@@ -417,7 +417,7 @@ class InheritanceTest < ActiveRecord::TestCase
 
   def test_eager_load_belongs_to_primary_key_quoting
     con = Account.connection
-    assert_sql(/#{con.quote_table_name('companies')}.#{con.quote_column_name('id')} = 1/) do
+    assert_sql(/#{con.quote_table_name('companies')}\.#{con.quote_column_name('id')} = 1/) do
       Account.all.merge!(includes: :firm).find(1)
     end
   end
diff --git a/activerecord/test/cases/integration_test.rb b/activerecord/test/cases/integration_test.rb
index 0678bb714f..9104976126 100644
--- a/activerecord/test/cases/integration_test.rb
+++ b/activerecord/test/cases/integration_test.rb
@@ -168,13 +168,65 @@ class IntegrationTest < ActiveRecord::TestCase
   end
 
   def test_named_timestamps_for_cache_key
-    owner = owners(:blackbeard)
-    assert_equal "owners/#{owner.id}-#{owner.happy_at.utc.to_s(:usec)}", owner.cache_key(:updated_at, :happy_at)
+    assert_deprecated do
+      owner = owners(:blackbeard)
+      assert_equal "owners/#{owner.id}-#{owner.happy_at.utc.to_s(:usec)}", owner.cache_key(:updated_at, :happy_at)
+    end
   end
 
   def test_cache_key_when_named_timestamp_is_nil
-    owner = owners(:blackbeard)
-    owner.happy_at = nil
-    assert_equal "owners/#{owner.id}", owner.cache_key(:happy_at)
+    assert_deprecated do
+      owner = owners(:blackbeard)
+      owner.happy_at = nil
+      assert_equal "owners/#{owner.id}", owner.cache_key(:happy_at)
+    end
+  end
+
+  def test_cache_key_is_stable_with_versioning_on
+    Developer.cache_versioning = true
+
+    developer = Developer.first
+    first_key = developer.cache_key
+
+    developer.touch
+    second_key = developer.cache_key
+
+    assert_equal first_key, second_key
+  ensure
+    Developer.cache_versioning = false
+  end
+
+  def test_cache_version_changes_with_versioning_on
+    Developer.cache_versioning = true
+
+    developer     = Developer.first
+    first_version = developer.cache_version
+
+    travel 10.seconds do
+      developer.touch
+    end
+
+    second_version = developer.cache_version
+
+    assert_not_equal first_version, second_version
+  ensure
+    Developer.cache_versioning = false
+  end
+
+  def test_cache_key_retains_version_when_custom_timestamp_is_used
+    Developer.cache_versioning = true
+
+    developer = Developer.first
+    first_key = developer.cache_key_with_version
+
+    travel 10.seconds do
+      developer.touch
+    end
+
+    second_key = developer.cache_key_with_version
+
+    assert_not_equal first_key, second_key
+  ensure
+    Developer.cache_versioning = false
   end
 end
diff --git a/activerecord/test/cases/json_serialization_test.rb b/activerecord/test/cases/json_serialization_test.rb
index 5a1d066aef..9b4b61b16e 100644
--- a/activerecord/test/cases/json_serialization_test.rb
+++ b/activerecord/test/cases/json_serialization_test.rb
@@ -168,7 +168,7 @@ class JsonSerializationTest < ActiveRecord::TestCase
 end
 
 class DatabaseConnectedJsonEncodingTest < ActiveRecord::TestCase
-  fixtures :authors, :posts, :comments, :tags, :taggings
+  fixtures :authors, :author_addresses, :posts, :comments, :tags, :taggings
 
   include JsonSerializationHelpers
 
diff --git a/activerecord/test/cases/json_shared_test_cases.rb b/activerecord/test/cases/json_shared_test_cases.rb
new file mode 100644
index 0000000000..d190b027bf
--- /dev/null
+++ b/activerecord/test/cases/json_shared_test_cases.rb
@@ -0,0 +1,177 @@
+require "support/schema_dumping_helper"
+
+module JSONSharedTestCases
+  include SchemaDumpingHelper
+
+  class JsonDataType < ActiveRecord::Base
+    self.table_name = "json_data_type"
+
+    store_accessor :settings, :resolution
+  end
+
+  def test_column
+    column = JsonDataType.columns_hash["payload"]
+    assert_equal column_type, column.type
+    assert_equal column_type.to_s, column.sql_type
+
+    type = JsonDataType.type_for_attribute("payload")
+    assert_not type.binary?
+  end
+
+  def test_change_table_supports_json
+    @connection.change_table("json_data_type") do |t|
+      t.public_send column_type, "users"
+    end
+    JsonDataType.reset_column_information
+    column = JsonDataType.columns_hash["users"]
+    assert_equal column_type, column.type
+    assert_equal column_type.to_s, column.sql_type
+  end
+
+  def test_schema_dumping
+    output = dump_table_schema("json_data_type")
+    assert_match(/t\.#{column_type}\s+"settings"/, output)
+  end
+
+  def test_cast_value_on_write
+    x = JsonDataType.new(payload: { "string" => "foo", :symbol => :bar })
+    assert_equal({ "string" => "foo", :symbol => :bar }, x.payload_before_type_cast)
+    assert_equal({ "string" => "foo", "symbol" => "bar" }, x.payload)
+    x.save!
+    assert_equal({ "string" => "foo", "symbol" => "bar" }, x.reload.payload)
+  end
+
+  def test_type_cast_json
+    type = JsonDataType.type_for_attribute("payload")
+
+    data = '{"a_key":"a_value"}'
+    hash = type.deserialize(data)
+    assert_equal({ "a_key" => "a_value" }, hash)
+    assert_equal({ "a_key" => "a_value" }, type.deserialize(data))
+
+    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_rewrite
+    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k":"v"}')|)
+    x = JsonDataType.first
+    x.payload = { '"a\'' => "b" }
+    assert x.save!
+  end
+
+  def test_select
+    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k":"v"}')|)
+    x = JsonDataType.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]}')|)
+    x = JsonDataType.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)")
+    x = JsonDataType.first
+    assert_nil(x.payload)
+  end
+
+  def test_select_nil_json_after_create
+    json = JsonDataType.create!(payload: nil)
+    x = JsonDataType.where(payload: nil).first
+    assert_equal(json, x)
+  end
+
+  def test_select_nil_json_after_update
+    json = JsonDataType.create!(payload: "foo")
+    x = JsonDataType.where(payload: nil).first
+    assert_nil(x)
+
+    json.update_attributes(payload: nil)
+    x = JsonDataType.where(payload: nil).first
+    assert_equal(json.reload, x)
+  end
+
+  def test_select_array_json_value
+    @connection.execute(%q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|)
+    x = JsonDataType.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"}]')|)
+    x = JsonDataType.first
+    x.payload = ["v1", { "k2" => "v2" }, "v3"]
+    assert x.save!
+  end
+
+  def test_with_store_accessors
+    x = JsonDataType.new(resolution: "320×480")
+    assert_equal "320×480", x.resolution
+
+    x.save!
+    x = JsonDataType.first
+    assert_equal "320×480", x.resolution
+
+    x.resolution = "640×1136"
+    x.save!
+
+    x = JsonDataType.first
+    assert_equal "640×1136", x.resolution
+  end
+
+  def test_duplication_with_store_accessors
+    x = JsonDataType.new(resolution: "320×480")
+    assert_equal "320×480", x.resolution
+
+    y = x.dup
+    assert_equal "320×480", y.resolution
+  end
+
+  def test_yaml_round_trip_with_store_accessors
+    x = JsonDataType.new(resolution: "320×480")
+    assert_equal "320×480", x.resolution
+
+    y = YAML.load(YAML.dump(x))
+    assert_equal "320×480", y.resolution
+  end
+
+  def test_changes_in_place
+    json = JsonDataType.new
+    assert_not json.changed?
+
+    json.payload = { "one" => "two" }
+    assert json.changed?
+    assert json.payload_changed?
+
+    json.save!
+    assert_not json.changed?
+
+    json.payload["three"] = "four"
+    assert json.payload_changed?
+
+    json.save!
+    json.reload
+
+    assert_equal({ "one" => "two", "three" => "four" }, json.payload)
+    assert_not json.changed?
+  end
+
+  def test_assigning_string_literal
+    json = JsonDataType.create!(payload: "foo")
+    assert_equal "foo", json.payload
+  end
+
+  def test_assigning_number
+    json = JsonDataType.create!(payload: 1.234)
+    assert_equal 1.234, json.payload
+  end
+
+  def test_assigning_boolean
+    json = JsonDataType.create!(payload: true)
+    assert_equal true, json.payload
+  end
+end
diff --git a/activerecord/test/cases/log_subscriber_test.rb b/activerecord/test/cases/log_subscriber_test.rb
index 90ad970e16..b80257962c 100644
--- a/activerecord/test/cases/log_subscriber_test.rb
+++ b/activerecord/test/cases/log_subscriber_test.rb
@@ -21,6 +21,7 @@ class LogSubscriberTest < ActiveRecord::TestCase
       TRANSACTION: REGEXP_CYAN,
       OTHER: REGEXP_MAGENTA
   }
+  Event = Struct.new(:duration, :payload)
 
   class TestDebugLogSubscriber < ActiveRecord::LogSubscriber
     attr_reader :debugs
@@ -55,25 +56,22 @@ class LogSubscriberTest < ActiveRecord::TestCase
   end
 
   def test_schema_statements_are_ignored
-    event = Struct.new(:duration, :payload)
-
     logger = TestDebugLogSubscriber.new
     assert_equal 0, logger.debugs.length
 
-    logger.sql(event.new(0, sql: "hi mom!"))
+    logger.sql(Event.new(0.9, sql: "hi mom!"))
     assert_equal 1, logger.debugs.length
 
-    logger.sql(event.new(0, sql: "hi mom!", name: "foo"))
+    logger.sql(Event.new(0.9, sql: "hi mom!", name: "foo"))
     assert_equal 2, logger.debugs.length
 
-    logger.sql(event.new(0, sql: "hi mom!", name: "SCHEMA"))
+    logger.sql(Event.new(0.9, sql: "hi mom!", name: "SCHEMA"))
     assert_equal 2, logger.debugs.length
   end
 
   def test_sql_statements_are_not_squeezed
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
-    logger.sql(event.new(0, sql: "ruby   rails"))
+    logger.sql(Event.new(0.9, sql: "ruby   rails"))
     assert_match(/ruby   rails/, logger.debugs.first)
   end
 
@@ -86,56 +84,51 @@ class LogSubscriberTest < ActiveRecord::TestCase
   end
 
   def test_basic_query_logging_coloration
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
     logger.colorize_logging = true
     SQL_COLORINGS.each do |verb, color_regex|
-      logger.sql(event.new(0, sql: verb.to_s))
+      logger.sql(Event.new(0.9, sql: verb.to_s))
       assert_match(/#{REGEXP_BOLD}#{color_regex}#{verb}#{REGEXP_CLEAR}/i, logger.debugs.last)
     end
   end
 
   def test_basic_payload_name_logging_coloration_generic_sql
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
     logger.colorize_logging = true
     SQL_COLORINGS.each do |verb, _|
-      logger.sql(event.new(0, sql: verb.to_s))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0.0ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: verb.to_s))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0\.9ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
 
-      logger.sql(event.new(0, sql: verb.to_s, name: "SQL"))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA}SQL \(0.0ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: verb.to_s, name: "SQL"))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA}SQL \(0\.9ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
     end
   end
 
   def test_basic_payload_name_logging_coloration_named_sql
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
     logger.colorize_logging = true
     SQL_COLORINGS.each do |verb, _|
-      logger.sql(event.new(0, sql: verb.to_s, name: "Model Load"))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_CYAN}Model Load \(0.0ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: verb.to_s, name: "Model Load"))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_CYAN}Model Load \(0\.9ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
 
-      logger.sql(event.new(0, sql: verb.to_s, name: "Model Exists"))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_CYAN}Model Exists \(0.0ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: verb.to_s, name: "Model Exists"))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_CYAN}Model Exists \(0\.9ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
 
-      logger.sql(event.new(0, sql: verb.to_s, name: "ANY SPECIFIC NAME"))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_CYAN}ANY SPECIFIC NAME \(0.0ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: verb.to_s, name: "ANY SPECIFIC NAME"))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_CYAN}ANY SPECIFIC NAME \(0\.9ms\)#{REGEXP_CLEAR}/i, logger.debugs.last)
     end
   end
 
   def test_query_logging_coloration_with_nested_select
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
     logger.colorize_logging = true
     SQL_COLORINGS.slice(:SELECT, :INSERT, :UPDATE, :DELETE).each do |verb, color_regex|
-      logger.sql(event.new(0, sql: "#{verb} WHERE ID IN SELECT"))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0.0ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{color_regex}#{verb} WHERE ID IN SELECT#{REGEXP_CLEAR}/i, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: "#{verb} WHERE ID IN SELECT"))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0\.9ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{color_regex}#{verb} WHERE ID IN SELECT#{REGEXP_CLEAR}/i, logger.debugs.last)
     end
   end
 
   def test_query_logging_coloration_with_multi_line_nested_select
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
     logger.colorize_logging = true
     SQL_COLORINGS.slice(:SELECT, :INSERT, :UPDATE, :DELETE).each do |verb, color_regex|
@@ -145,13 +138,12 @@ class LogSubscriberTest < ActiveRecord::TestCase
           SELECT ID FROM THINGS
         )
       EOS
-      logger.sql(event.new(0, sql: sql))
-      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0.0ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{color_regex}.*#{verb}.*#{REGEXP_CLEAR}/mi, logger.debugs.last)
+      logger.sql(Event.new(0.9, sql: sql))
+      assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0\.9ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{color_regex}.*#{verb}.*#{REGEXP_CLEAR}/mi, logger.debugs.last)
     end
   end
 
   def test_query_logging_coloration_with_lock
-    event = Struct.new(:duration, :payload)
     logger = TestDebugLogSubscriber.new
     logger.colorize_logging = true
     sql = <<-EOS
@@ -159,14 +151,14 @@ class LogSubscriberTest < ActiveRecord::TestCase
         (SELECT * FROM mytable FOR UPDATE) ss
       WHERE col1 = 5;
     EOS
-    logger.sql(event.new(0, sql: sql))
-    assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0.0ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{SQL_COLORINGS[:LOCK]}.*FOR UPDATE.*#{REGEXP_CLEAR}/mi, logger.debugs.last)
+    logger.sql(Event.new(0.9, sql: sql))
+    assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0\.9ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{SQL_COLORINGS[:LOCK]}.*FOR UPDATE.*#{REGEXP_CLEAR}/mi, logger.debugs.last)
 
     sql = <<-EOS
       LOCK TABLE films IN SHARE MODE;
     EOS
-    logger.sql(event.new(0, sql: sql))
-    assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0.0ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{SQL_COLORINGS[:LOCK]}.*LOCK TABLE.*#{REGEXP_CLEAR}/mi, logger.debugs.last)
+    logger.sql(Event.new(0.9, sql: sql))
+    assert_match(/#{REGEXP_BOLD}#{REGEXP_MAGENTA} \(0\.9ms\)#{REGEXP_CLEAR}  #{REGEXP_BOLD}#{SQL_COLORINGS[:LOCK]}.*LOCK TABLE.*#{REGEXP_CLEAR}/mi, logger.debugs.last)
   end
 
   def test_exists_query_logging
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 802a969cb7..007926f1b9 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -211,11 +211,6 @@ module ActiveRecord
         assert_equal [:remove_index, [:table, { name: "new_index" }]], remove
       end
 
-      def test_invert_add_index_with_no_options
-        remove = @recorder.inverse_of :add_index, [:table, [:one, :two]]
-        assert_equal [:remove_index, [:table, { column: [:one, :two] }]], 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/references_statements_test.rb b/activerecord/test/cases/migration/references_statements_test.rb
index 06c44c8c52..e9eb9968cb 100644
--- a/activerecord/test/cases/migration/references_statements_test.rb
+++ b/activerecord/test/cases/migration/references_statements_test.rb
@@ -50,6 +50,14 @@ module ActiveRecord
         assert column_exists?(table_name, :taggable_type, :string, default: "Photo")
       end
 
+      def test_creates_reference_type_column_with_not_null
+        connection.create_table table_name, force: true do |t|
+          t.references :taggable, null: false, polymorphic: true
+        end
+        assert column_exists?(table_name, :taggable_id, :integer, null: false)
+        assert column_exists?(table_name, :taggable_type, :string, null: false)
+      end
+
       def test_does_not_share_options_with_reference_type_column
         add_reference table_name, :taggable, type: :integer, limit: 2, polymorphic: true
         assert column_exists?(table_name, :taggable_id, :integer, limit: 2)
diff --git a/activerecord/test/cases/migration/rename_table_test.rb b/activerecord/test/cases/migration/rename_table_test.rb
index 7bcabd0cc6..5da3ad33a3 100644
--- a/activerecord/test/cases/migration/rename_table_test.rb
+++ b/activerecord/test/cases/migration/rename_table_test.rb
@@ -79,10 +79,33 @@ module ActiveRecord
           assert_equal ConnectionAdapters::PostgreSQL::Name.new("public", "octopi_#{pk}_seq"), seq
         end
 
+        def test_renaming_table_renames_primary_key
+          connection.create_table :cats, id: :uuid, default: "uuid_generate_v4()"
+          rename_table :cats, :felines
+
+          assert connection.table_exists? :felines
+          refute connection.table_exists? :cats
+
+          primary_key_name = connection.select_values(<<-SQL.strip_heredoc, "SCHEMA")[0]
+            SELECT c.relname
+              FROM pg_class c
+              JOIN pg_index i
+                ON c.oid = i.indexrelid
+             WHERE i.indisprimary
+               AND i.indrelid = 'felines'::regclass
+          SQL
+
+          assert_equal "felines_pkey", primary_key_name
+        ensure
+          connection.drop_table :cats, if_exists: true
+          connection.drop_table :felines, if_exists: true
+        end
+
         def test_renaming_table_doesnt_attempt_to_rename_non_existent_sequences
           connection.create_table :cats, id: :uuid, default: "uuid_generate_v4()"
           assert_nothing_raised { rename_table :cats, :felines }
           assert connection.table_exists? :felines
+          refute connection.table_exists? :cats
         ensure
           connection.drop_table :cats, if_exists: true
           connection.drop_table :felines, if_exists: true
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index da7875187a..57f94950f9 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -402,33 +402,6 @@ class MigrationTest < ActiveRecord::TestCase
     ActiveRecord::Migrator.up(migrations_path)
   end
 
-  def test_migration_sets_internal_metadata_even_when_fully_migrated
-    current_env     = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
-    migrations_path = MIGRATIONS_ROOT + "/valid"
-    old_path        = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
-
-    ActiveRecord::Migrator.up(migrations_path)
-    assert_equal current_env, ActiveRecord::InternalMetadata[:environment]
-
-    original_rails_env  = ENV["RAILS_ENV"]
-    original_rack_env   = ENV["RACK_ENV"]
-    ENV["RAILS_ENV"]    = ENV["RACK_ENV"] = "foofoo"
-    new_env = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
-
-    refute_equal current_env, new_env
-
-    sleep 1 # mysql by default does not store fractional seconds in the database
-
-    ActiveRecord::Migrator.up(migrations_path)
-    assert_equal new_env, ActiveRecord::InternalMetadata[:environment]
-  ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
-    ENV["RAILS_ENV"] = original_rails_env
-    ENV["RACK_ENV"]  = original_rack_env
-    ActiveRecord::Migrator.up(migrations_path)
-  end
-
   def test_internal_metadata_stores_environment_when_other_data_exists
     ActiveRecord::InternalMetadata.delete_all
     ActiveRecord::InternalMetadata[:foo] = "bar"
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index b87419d203..5a62cbd3a6 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -752,7 +752,7 @@ module NestedAttributesOnACollectionAssociationTests
     exception = assert_raise ArgumentError do
       @pirate.send(association_setter, "foo")
     end
-    assert_equal 'Hash or Array expected, got String ("foo")', exception.message
+    assert_equal %{Hash or Array expected for attribute `#{@association_name}`, got String ("foo")}, exception.message
   end
 
   def test_should_work_with_update_as_well
diff --git a/activerecord/test/cases/quoting_test.rb b/activerecord/test/cases/quoting_test.rb
index f260d043e4..0819776fbf 100644
--- a/activerecord/test/cases/quoting_test.rb
+++ b/activerecord/test/cases/quoting_test.rb
@@ -81,8 +81,21 @@ module ActiveRecord
         end
       end
 
+      class QuotedOne
+        def quoted_id
+          1
+        end
+      end
+      class SubQuotedOne < QuotedOne
+      end
       def test_quote_with_quoted_id
-        assert_deprecated { assert_equal 1, @quoter.quote(Struct.new(:quoted_id).new(1)) }
+        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
diff --git a/activerecord/test/cases/readonly_test.rb b/activerecord/test/cases/readonly_test.rb
index a93061b516..24b678310d 100644
--- a/activerecord/test/cases/readonly_test.rb
+++ b/activerecord/test/cases/readonly_test.rb
@@ -10,7 +10,7 @@ require "models/person"
 require "models/ship"
 
 class ReadOnlyTest < ActiveRecord::TestCase
-  fixtures :authors, :posts, :comments, :developers, :projects, :developers_projects, :people, :readers
+  fixtures :authors, :author_addresses, :posts, :comments, :developers, :projects, :developers_projects, :people, :readers
 
   def test_cant_save_readonly_record
     dev = Developer.find(1)
diff --git a/activerecord/test/cases/relation/delegation_test.rb b/activerecord/test/cases/relation/delegation_test.rb
index 8cb7b82015..cb6e4d76d3 100644
--- a/activerecord/test/cases/relation/delegation_test.rb
+++ b/activerecord/test/cases/relation/delegation_test.rb
@@ -3,29 +3,7 @@ require "models/post"
 require "models/comment"
 
 module ActiveRecord
-  class DelegationTest < ActiveRecord::TestCase
-    fixtures :posts
-
-    def call_method(target, method)
-      method_arity = target.to_a.method(method).arity
-
-      if method_arity.zero?
-        target.public_send(method)
-      elsif method_arity < 0
-        if method == :shuffle!
-          target.public_send(method)
-        else
-          target.public_send(method, 1)
-        end
-       elsif method_arity == 1
-         target.public_send(method, 1)
-      else
-        raise NotImplementedError
-      end
-    end
-  end
-
-  module DelegationWhitelistBlacklistTests
+  module DelegationWhitelistTests
     ARRAY_DELEGATES = [
       :+, :-, :|, :&, :[], :shuffle,
       :all?, :collect, :compact, :detect, :each, :each_cons, :each_with_index,
@@ -43,16 +21,18 @@ module ActiveRecord
     end
   end
 
-  class DelegationAssociationTest < DelegationTest
-    include DelegationWhitelistBlacklistTests
+  class DelegationAssociationTest < ActiveRecord::TestCase
+    include DelegationWhitelistTests
+
+    fixtures :posts
 
     def target
       Post.first.comments
     end
   end
 
-  class DelegationRelationTest < DelegationTest
-    include DelegationWhitelistBlacklistTests
+  class DelegationRelationTest < ActiveRecord::TestCase
+    include DelegationWhitelistTests
 
     fixtures :comments
 
diff --git a/activerecord/test/cases/relation/merging_test.rb b/activerecord/test/cases/relation/merging_test.rb
index 67d76de798..c3b39a9295 100644
--- a/activerecord/test/cases/relation/merging_test.rb
+++ b/activerecord/test/cases/relation/merging_test.rb
@@ -8,7 +8,7 @@ require "models/project"
 require "models/rating"
 
 class RelationMergingTest < ActiveRecord::TestCase
-  fixtures :developers, :comments, :authors, :posts
+  fixtures :developers, :comments, :authors, :author_addresses, :posts
 
   def test_relation_merging
     devs = Developer.where("salary >= 80000").merge(Developer.limit(2)).merge(Developer.order("id ASC").where("id < 3"))
@@ -56,7 +56,7 @@ class RelationMergingTest < ActiveRecord::TestCase
 
   def test_relation_merging_with_locks
     devs = Developer.lock.where("salary >= 80000").order("id DESC").merge(Developer.limit(2))
-    assert devs.locked.present?
+    assert devs.locked?
   end
 
   def test_relation_merging_with_preload
@@ -114,7 +114,7 @@ class RelationMergingTest < ActiveRecord::TestCase
 end
 
 class MergingDifferentRelationsTest < ActiveRecord::TestCase
-  fixtures :posts, :authors, :developers
+  fixtures :posts, :authors, :author_addresses, :developers
 
   test "merging where relations" do
     hello_by_bob = Post.where(body: "hello").joins(:author).
diff --git a/activerecord/test/cases/relation/mutation_test.rb b/activerecord/test/cases/relation/mutation_test.rb
index 11ef0d8743..dea787c07f 100644
--- a/activerecord/test/cases/relation/mutation_test.rb
+++ b/activerecord/test/cases/relation/mutation_test.rb
@@ -36,7 +36,7 @@ module ActiveRecord
       @relation ||= Relation.new FakeKlass.new("posts"), Post.arel_table, Post.predicate_builder
     end
 
-    (Relation::MULTI_VALUE_METHODS - [:references, :extending, :order, :unscope, :select, :left_joins]).each do |method|
+    (Relation::MULTI_VALUE_METHODS - [:references, :extending, :order, :unscope, :select]).each do |method|
       test "##{method}!" do
         assert relation.public_send("#{method}!", :foo).equal?(relation)
         assert_equal [:foo], relation.public_send("#{method}_values")
diff --git a/activerecord/test/cases/relation/where_chain_test.rb b/activerecord/test/cases/relation/where_chain_test.rb
index a96d1ae5b5..86e150ed79 100644
--- a/activerecord/test/cases/relation/where_chain_test.rb
+++ b/activerecord/test/cases/relation/where_chain_test.rb
@@ -25,7 +25,7 @@ module ActiveRecord
     end
 
     def test_association_not_eq
-      expected = Arel::Nodes::Grouping.new(Comment.arel_table[@name].not_eq(Arel::Nodes::BindParam.new))
+      expected = Arel::Nodes::Grouping.new(Comment.arel_table[@name].not_eq(bind_param))
       relation = Post.joins(:comments).where.not(comments: { title: "hello" })
       assert_equal(expected.to_sql, relation.where_clause.ast.to_sql)
     end
diff --git a/activerecord/test/cases/relation/where_clause_test.rb b/activerecord/test/cases/relation/where_clause_test.rb
index d8e4c304f0..f8eb0dee91 100644
--- a/activerecord/test/cases/relation/where_clause_test.rb
+++ b/activerecord/test/cases/relation/where_clause_test.rb
@@ -47,15 +47,15 @@ class ActiveRecord::Relation
     test "merge removes bind parameters matching overlapping equality clauses" do
       a = WhereClause.new(
         [table["id"].eq(bind_param), table["name"].eq(bind_param)],
-        [attribute("id", 1), attribute("name", "Sean")],
+        [bind_attribute("id", 1), bind_attribute("name", "Sean")],
       )
       b = WhereClause.new(
         [table["name"].eq(bind_param)],
-        [attribute("name", "Jim")]
+        [bind_attribute("name", "Jim")]
       )
       expected = WhereClause.new(
         [table["id"].eq(bind_param), table["name"].eq(bind_param)],
-        [attribute("id", 1), attribute("name", "Jim")],
+        [bind_attribute("id", 1), bind_attribute("name", "Jim")],
       )
 
       assert_equal expected, a.merge(b)
@@ -103,10 +103,10 @@ class ActiveRecord::Relation
         table["name"].eq(bind_param),
         table["age"].gteq(bind_param),
       ], [
-        attribute("name", "Sean"),
-        attribute("age", 30),
+        bind_attribute("name", "Sean"),
+        bind_attribute("age", 30),
       ])
-      expected = WhereClause.new([table["age"].gteq(bind_param)], [attribute("age", 30)])
+      expected = WhereClause.new([table["age"].gteq(bind_param)], [bind_attribute("age", 30)])
 
       assert_equal expected, where_clause.except("id", "name")
     end
@@ -146,8 +146,8 @@ class ActiveRecord::Relation
     end
 
     test "or joins the two clauses using OR" do
-      where_clause = WhereClause.new([table["id"].eq(bind_param)], [attribute("id", 1)])
-      other_clause = WhereClause.new([table["name"].eq(bind_param)], [attribute("name", "Sean")])
+      where_clause = WhereClause.new([table["id"].eq(bind_param)], [bind_attribute("id", 1)])
+      other_clause = WhereClause.new([table["name"].eq(bind_param)], [bind_attribute("name", "Sean")])
       expected_ast =
         Arel::Nodes::Grouping.new(
           Arel::Nodes::Or.new(table["id"].eq(bind_param), table["name"].eq(bind_param))
@@ -159,7 +159,7 @@ class ActiveRecord::Relation
     end
 
     test "or returns an empty where clause when either side is empty" do
-      where_clause = WhereClause.new([table["id"].eq(bind_param)], [attribute("id", 1)])
+      where_clause = WhereClause.new([table["id"].eq(bind_param)], [bind_attribute("id", 1)])
 
       assert_equal WhereClause.empty, where_clause.or(WhereClause.empty)
       assert_equal WhereClause.empty, WhereClause.empty.or(where_clause)
@@ -170,13 +170,5 @@ class ActiveRecord::Relation
       def table
         Arel::Table.new("table")
       end
-
-      def bind_param
-        Arel::Nodes::BindParam.new
-      end
-
-      def attribute(name, value)
-        ActiveRecord::Attribute.with_cast_value(name, value, ActiveRecord::Type::Value.new)
-      end
   end
 end
diff --git a/activerecord/test/cases/relation/where_test.rb b/activerecord/test/cases/relation/where_test.rb
index 9a333e0d5a..cbc466d6b8 100644
--- a/activerecord/test/cases/relation/where_test.rb
+++ b/activerecord/test/cases/relation/where_test.rb
@@ -15,7 +15,7 @@ require "models/vertex"
 
 module ActiveRecord
   class WhereTest < ActiveRecord::TestCase
-    fixtures :posts, :edges, :authors, :binaries, :essays, :cars, :treasures, :price_estimates
+    fixtures :posts, :edges, :authors, :author_addresses, :binaries, :essays, :cars, :treasures, :price_estimates
 
     def test_where_copies_bind_params
       author = authors(:david)
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 1241bb54a4..5fb32270b7 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -6,7 +6,7 @@ require "models/rating"
 
 module ActiveRecord
   class RelationTest < ActiveRecord::TestCase
-    fixtures :posts, :comments, :authors
+    fixtures :posts, :comments, :authors, :author_addresses
 
     FakeKlass = Struct.new(:table_name, :name) do
       extend ActiveRecord::Delegation::DelegateCache
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index d32db0558f..81173945a3 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -22,7 +22,7 @@ require "models/categorization"
 require "models/edge"
 
 class RelationTest < ActiveRecord::TestCase
-  fixtures :authors, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :posts, :comments,
+  fixtures :authors, :author_addresses, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :posts, :comments,
     :tags, :taggings, :cars, :minivans
 
   class TopicWithCallbacks < ActiveRecord::Base
@@ -1981,24 +1981,28 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_unscope_removes_binds
-    left = Post.where(id: Arel::Nodes::BindParam.new)
-    column = Post.columns_hash["id"]
-    left.bind_values += [[column, 20]]
+    left = Post.where(id: 20)
+
+    binds = [bind_attribute("id", 20, Post.type_for_attribute("id"))]
+    assert_equal binds, left.bound_attributes
 
     relation = left.unscope(where: :id)
-    assert_equal [], relation.bind_values
+    assert_equal [], relation.bound_attributes
   end
 
-  def test_merging_removes_rhs_bind_parameters
+  def test_merging_removes_rhs_binds
     left = Post.where(id: 20)
     right = Post.where(id: [1, 2, 3, 4])
 
+    binds = [bind_attribute("id", 20, Post.type_for_attribute("id"))]
+    assert_equal binds, left.bound_attributes
+
     merged = left.merge(right)
-    assert_equal [], merged.bind_values
+    assert_equal [], merged.bound_attributes
   end
 
-  def test_merging_keeps_lhs_bind_parameters
-    binds = [ActiveRecord::Relation::QueryAttribute.new("id", 20, Post.type_for_attribute("id"))]
+  def test_merging_keeps_lhs_binds
+    binds = [bind_attribute("id", 20, Post.type_for_attribute("id"))]
 
     right  = Post.where(id: 20)
     left   = Post.where(id: 10)
@@ -2007,15 +2011,6 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal binds, merged.bound_attributes
   end
 
-  def test_merging_reorders_bind_params
-    post  = Post.first
-    right = Post.where(id: post.id)
-    left  = Post.where(title: post.title)
-
-    merged = left.merge(right)
-    assert_equal post, merged.first
-  end
-
   def test_relation_join_method
     assert_equal "Thank you for the welcome,Thank you again for the welcome", Post.first.comments.join(",")
   end
diff --git a/activerecord/test/cases/reload_models_test.rb b/activerecord/test/cases/reload_models_test.rb
index dffb55ba81..38a8d84107 100644
--- a/activerecord/test/cases/reload_models_test.rb
+++ b/activerecord/test/cases/reload_models_test.rb
@@ -15,7 +15,7 @@ class ReloadModelsTest < ActiveRecord::TestCase
     # development environment. Note that meanwhile the class Pet is not
     # reloaded, simulating a class that is present in a plugin.
     Object.class_eval { remove_const :Owner }
-    Kernel.load(File.expand_path(File.join(File.dirname(__FILE__), "../models/owner.rb")))
+    Kernel.load(File.expand_path("../models/owner.rb", __dir__))
 
     pet = Pet.find_by_name("parrot")
     pet.owner = Owner.find_by_name("ashley")
diff --git a/activerecord/test/cases/scoping/relation_scoping_test.rb b/activerecord/test/cases/scoping/relation_scoping_test.rb
index a1ae57fdbb..8535be8402 100644
--- a/activerecord/test/cases/scoping/relation_scoping_test.rb
+++ b/activerecord/test/cases/scoping/relation_scoping_test.rb
@@ -10,7 +10,7 @@ require "models/person"
 require "models/reference"
 
 class RelationScopingTest < ActiveRecord::TestCase
-  fixtures :authors, :developers, :projects, :comments, :posts, :developers_projects
+  fixtures :authors, :author_addresses, :developers, :projects, :comments, :posts, :developers_projects
 
   setup do
     developers(:david)
@@ -229,16 +229,23 @@ class RelationScopingTest < ActiveRecord::TestCase
     end
   end
 
-  def test_circular_joins_with_current_scope_does_not_crash
+  def test_circular_joins_with_scoping_does_not_crash
     posts = Post.joins(comments: :post).scoping do
-      Post.current_scope.first(10)
+      Post.first(10)
     end
     assert_equal posts, Post.joins(comments: :post).first(10)
   end
+
+  def test_circular_left_joins_with_scoping_does_not_crash
+    posts = Post.left_joins(comments: :post).scoping do
+      Post.first(10)
+    end
+    assert_equal posts, Post.left_joins(comments: :post).first(10)
+  end
 end
 
 class NestedRelationScopingTest < ActiveRecord::TestCase
-  fixtures :authors, :developers, :projects, :comments, :posts
+  fixtures :authors, :author_addresses, :developers, :projects, :comments, :posts
 
   def test_merge_options
     Developer.where("salary = 80000").scoping do
diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index 673392b4c4..e1bdaab5cf 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -349,4 +349,32 @@ class SerializedAttributeTest < ActiveRecord::TestCase
     topic.foo
     refute topic.changed?
   end
+
+  def test_serialized_attribute_works_under_concurrent_initial_access
+    model = Topic.dup
+
+    topic = model.last
+    topic.update group: "1"
+
+    model.serialize :group, JSON
+    model.reset_column_information
+
+    # This isn't strictly necessary for the test, but a little bit of
+    # knowledge of internals allows us to make failures far more likely.
+    model.define_singleton_method(:define_attribute) do |*args|
+      Thread.pass
+      super(*args)
+    end
+
+    threads = 4.times.map do
+      Thread.new do
+        topic.reload.group
+      end
+    end
+
+    # All the threads should retrieve the value knowing it is JSON, and
+    # thus decode it. If this fails, some threads will instead see the
+    # raw string ("1"), or raise an exception.
+    assert_equal [1] * threads.size, threads.map(&:value)
+  end
 end
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index b4983624ba..c47c97e9d9 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -368,7 +368,8 @@ module ActiveRecord
     def test_migrate_raise_error_on_empty_version
       version = ENV["VERSION"]
       ENV["VERSION"] = ""
-      assert_raise(RuntimeError, "Empty VERSION provided") { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_equal "Empty VERSION provided", e.message
     ensure
       ENV["VERSION"] = version
     end
diff --git a/activerecord/test/cases/tasks/mysql_rake_test.rb b/activerecord/test/cases/tasks/mysql_rake_test.rb
index b85d303a91..c22d974536 100644
--- a/activerecord/test/cases/tasks/mysql_rake_test.rb
+++ b/activerecord/test/cases/tasks/mysql_rake_test.rb
@@ -305,6 +305,15 @@ if current_adapter?(:Mysql2Adapter)
         end
       end
 
+      def test_structure_dump_with_ignore_tables
+        filename = "awesome-file.sql"
+        ActiveRecord::SchemaDumper.expects(:ignore_tables).returns(["foo", "bar"])
+
+        Kernel.expects(:system).with("mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "--ignore-table=test-db.foo", "--ignore-table=test-db.bar", "test-db").returns(true)
+
+        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+      end
+
       def test_warn_when_external_structure_dump_command_execution_fails
         filename = "awesome-file.sql"
         Kernel.expects(:system)
diff --git a/activerecord/test/cases/tasks/postgresql_rake_test.rb b/activerecord/test/cases/tasks/postgresql_rake_test.rb
index 512388af6b..a2e968aedf 100644
--- a/activerecord/test/cases/tasks/postgresql_rake_test.rb
+++ b/activerecord/test/cases/tasks/postgresql_rake_test.rb
@@ -259,6 +259,14 @@ if current_adapter?(:PostgreSQLAdapter)
         end
       end
 
+      def test_structure_dump_with_ignore_tables
+        ActiveRecord::SchemaDumper.expects(:ignore_tables).returns(["foo", "bar"])
+
+        Kernel.expects(:system).with("pg_dump", "-s", "-x", "-O", "-f", @filename, "-T", "foo", "-T", "bar", "my-app-db").returns(true)
+
+        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+      end
+
       def test_structure_dump_with_schema_search_path
         @configuration["schema_search_path"] = "foo,bar"
 
diff --git a/activerecord/test/cases/tasks/sqlite_rake_test.rb b/activerecord/test/cases/tasks/sqlite_rake_test.rb
index 0d917f3f6c..ccb3834fee 100644
--- a/activerecord/test/cases/tasks/sqlite_rake_test.rb
+++ b/activerecord/test/cases/tasks/sqlite_rake_test.rb
@@ -180,6 +180,9 @@ if current_adapter?(:SQLite3Adapter)
           "adapter"  => "sqlite3",
           "database" => @database
         }
+
+        `sqlite3 #{@database} 'CREATE TABLE bar(id INTEGER)'`
+        `sqlite3 #{@database} 'CREATE TABLE foo(id INTEGER)'`
       end
 
       def test_structure_dump
@@ -189,6 +192,23 @@ if current_adapter?(:SQLite3Adapter)
         ActiveRecord::Tasks::DatabaseTasks.structure_dump @configuration, filename, "/rails/root"
         assert File.exist?(dbfile)
         assert File.exist?(filename)
+        assert_match(/CREATE TABLE foo/, File.read(filename))
+        assert_match(/CREATE TABLE bar/, File.read(filename))
+      ensure
+        FileUtils.rm_f(filename)
+        FileUtils.rm_f(dbfile)
+      end
+
+      def test_structure_dump_with_ignore_tables
+        dbfile   = @database
+        filename = "awesome-file.sql"
+        ActiveRecord::SchemaDumper.expects(:ignore_tables).returns(["foo"])
+
+        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename, "/rails/root")
+        assert File.exist?(dbfile)
+        assert File.exist?(filename)
+        assert_match(/bar/, File.read(filename))
+        assert_no_match(/foo/, File.read(filename))
       ensure
         FileUtils.rm_f(filename)
         FileUtils.rm_f(dbfile)
diff --git a/activerecord/test/cases/test_case.rb b/activerecord/test/cases/test_case.rb
index 31b11c19f7..9f594fef85 100644
--- a/activerecord/test/cases/test_case.rb
+++ b/activerecord/test/cases/test_case.rb
@@ -75,6 +75,14 @@ module ActiveRecord
       model.reset_column_information
       model.column_names.include?(column_name.to_s)
     end
+
+    def bind_param
+      Arel::Nodes::BindParam.new
+    end
+
+    def bind_attribute(name, value, type = ActiveRecord::Type.default_value)
+      ActiveRecord::Relation::QueryAttribute.new(name, value, type)
+    end
   end
 
   class PostgreSQLTestCase < TestCase
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index 111495c481..5c6d78b574 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -10,7 +10,7 @@ require "models/movie"
 
 class TransactionTest < ActiveRecord::TestCase
   self.use_transactional_tests = false
-  fixtures :topics, :developers, :authors, :posts
+  fixtures :topics, :developers, :authors, :author_addresses, :posts
 
   def setup
     @first, @second = Topic.find(1, 2).sort_by(&:id)
diff --git a/activerecord/test/cases/validations_test.rb b/activerecord/test/cases/validations_test.rb
index 5d9aa99497..a305aa295a 100644
--- a/activerecord/test/cases/validations_test.rb
+++ b/activerecord/test/cases/validations_test.rb
@@ -167,6 +167,20 @@ class ValidationsTest < ActiveRecord::TestCase
     assert topic.valid?
   end
 
+  def test_numericality_validation_checks_against_raw_value
+    klass = Class.new(Topic) do
+      def self.model_name
+        ActiveModel::Name.new(self, nil, "Topic")
+      end
+      attribute :wibble, :decimal, scale: 2, precision: 9
+      validates_numericality_of :wibble, greater_than_or_equal_to: BigDecimal.new("97.18")
+    end
+
+    assert_not klass.new(wibble: "97.179").valid?
+    assert_not klass.new(wibble: 97.179).valid?
+    assert_not klass.new(wibble: BigDecimal.new("97.179")).valid?
+  end
+
   def test_acceptance_validator_doesnt_require_db_connection
     klass = Class.new(ActiveRecord::Base) do
       self.table_name = "posts"
diff --git a/activerecord/test/cases/yaml_serialization_test.rb b/activerecord/test/cases/yaml_serialization_test.rb
index 1571b31329..bfc13d683d 100644
--- a/activerecord/test/cases/yaml_serialization_test.rb
+++ b/activerecord/test/cases/yaml_serialization_test.rb
@@ -5,7 +5,7 @@ require "models/post"
 require "models/author"
 
 class YamlSerializationTest < ActiveRecord::TestCase
-  fixtures :topics, :authors, :posts
+  fixtures :topics, :authors, :author_addresses, :posts
 
   def test_to_yaml_with_time_with_zone_should_not_raise_exception
     with_timezone_config aware_attributes: true, zone: "Pacific Time (US & Canada)" do
@@ -123,8 +123,8 @@ class YamlSerializationTest < ActiveRecord::TestCase
 
     def yaml_fixture(file_name)
       path = File.expand_path(
-        "../../support/yaml_compatibility_fixtures/#{file_name}.yml",
-        __FILE__
+        "../support/yaml_compatibility_fixtures/#{file_name}.yml",
+        __dir__
       )
       File.read(path)
     end
diff --git a/activerecord/test/config.rb b/activerecord/test/config.rb
index 6e2e8b2145..a65e6ff776 100644
--- a/activerecord/test/config.rb
+++ b/activerecord/test/config.rb
@@ -1,4 +1,4 @@
-TEST_ROOT       = File.expand_path(File.dirname(__FILE__))
+TEST_ROOT       = __dir__
 ASSETS_ROOT     = TEST_ROOT + "/assets"
 FIXTURES_ROOT   = TEST_ROOT + "/fixtures"
 MIGRATIONS_ROOT = TEST_ROOT + "/migrations"
diff --git a/activerecord/test/fixtures/books.yml b/activerecord/test/fixtures/books.yml
index b3625ee72e..699623a6f9 100644
--- a/activerecord/test/fixtures/books.yml
+++ b/activerecord/test/fixtures/books.yml
@@ -25,6 +25,7 @@ ddd:
   name: "Domain-Driven Design"
   format: "hardcover"
   status: 2
+  read_status: "forgotten"
 
 tlg:
   author_id: 1
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index fab613afd1..2d9cba77e0 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -106,6 +106,7 @@ class Author < ActiveRecord::Base
   has_many :tags_with_primary_key, through: :posts
 
   has_many :books
+  has_many :unpublished_books, -> { where(status: [:proposed, :written]) }, class_name: "Book"
   has_many :subscriptions,        through: :books
   has_many :subscribers, -> { order("subscribers.nick") }, through: :subscriptions
   has_many :distinct_subscribers, -> { select("DISTINCT subscribers.*").order("subscribers.nick") }, through: :subscriptions, source: :subscriber
diff --git a/activerecord/test/models/book.rb b/activerecord/test/models/book.rb
index 17bf3fbcb4..6466e1b341 100644
--- a/activerecord/test/models/book.rb
+++ b/activerecord/test/models/book.rb
@@ -1,5 +1,5 @@
 class Book < ActiveRecord::Base
-  has_many :authors
+  belongs_to :author
 
   has_many :citations, foreign_key: "book1_id"
   has_many :references, -> { distinct }, through: :citations, source: :reference_of
@@ -8,7 +8,7 @@ class Book < ActiveRecord::Base
   has_many :subscribers, through: :subscriptions
 
   enum status: [:proposed, :written, :published]
-  enum read_status: { unread: 0, reading: 2, read: 3 }
+  enum read_status: { unread: 0, reading: 2, read: 3, forgotten: nil }
   enum nullable_status: [:single, :married]
   enum language: [:english, :spanish, :french], _prefix: :in
   enum author_visibility: [:visible, :invisible], _prefix: true
diff --git a/activerecord/test/models/category.rb b/activerecord/test/models/category.rb
index e8654dca01..4b2840c653 100644
--- a/activerecord/test/models/category.rb
+++ b/activerecord/test/models/category.rb
@@ -29,6 +29,15 @@ class Category < ActiveRecord::Base
   has_many :authors_with_select, -> { select "authors.*, categorizations.post_id" }, through: :categorizations, source: :author
 
   scope :general, -> { where(name: "General") }
+
+  # Should be delegated `ast` and `locked` to `arel`.
+  def self.ast
+    raise
+  end
+
+  def self.locked
+    raise
+  end
 end
 
 class SpecialCategory < Category
diff --git a/activerecord/test/models/topic.rb b/activerecord/test/models/topic.rb
index 0420e2d15c..d9381ac9cf 100644
--- a/activerecord/test/models/topic.rb
+++ b/activerecord/test/models/topic.rb
@@ -14,7 +14,7 @@ class Topic < ActiveRecord::Base
   scope :replied, -> { where "replies_count > 0" }
 
   scope "approved_as_string", -> { where(approved: true) }
-  scope :anonymous_extension, -> { all } do
+  scope :anonymous_extension, -> {} do
     def one
       1
     end
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index a4fc1e34eb..bb578d81dc 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,51 @@
+*   Add default option to class_attribute. Before:
+
+      class_attribute :settings
+      self.settings = {}
+
+    Now:
+
+      class_attribute :settings, default: {}
+
+    *DHH*
+
+*   `#singularize` and `#pluralize` now respect uncountables for the specified locale.
+
+    *Eilis Hamilton*
+
+*   Add ActiveSupport::CurrentAttributes to provide a thread-isolated attributes singleton.
+    Primary use case is keeping all the per-request attributes easily available to the whole system.
+    
+    *DHH*
+
+*   Fix implicit coercion calculations with scalars and durations
+
+    Previously calculations where the scalar is first would be converted to a duration
+    of seconds but this causes issues with dates being converted to times, e.g:
+
+        Time.zone = "Beijing"           # => Asia/Shanghai
+        date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
+        2 * 1.day                       # => 172800 seconds
+        date + 2 * 1.day                # => Mon, 22 May 2017 00:00:00 CST +08:00
+
+    Now the `ActiveSupport::Duration::Scalar` calculation methods will try to maintain
+    the part structure of the duration where possible, e.g:
+
+        Time.zone = "Beijing"           # => Asia/Shanghai
+        date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
+        2 * 1.day                       # => 2 days
+        date + 2 * 1.day                # => Mon, 22 May 2017
+
+    Fixes #29160, #28970.
+
+    *Andrew White*
+
+*   Add support for versioned cache entries. This enables the cache stores to recycle cache keys, greatly saving
+    on storage in cases with frequent churn. Works together with the separation of `#cache_key` and `#cache_version`
+    in Active Record and its use in Action Pack's fragment caching.
+
+    *DHH*
+
 *   Pass gem name and deprecation horizon to deprecation notifications.
 
     *Willem van Bergen*
@@ -18,4 +66,5 @@
 
     *Josh Pencheon*
 
+
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activesupport/CHANGELOG.md) for previous changes.
diff --git a/activesupport/activesupport.gemspec b/activesupport/activesupport.gemspec
index 08370cba85..ed277c81ef 100644
--- a/activesupport/activesupport.gemspec
+++ b/activesupport/activesupport.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/activesupport/bin/generate_tables b/activesupport/bin/generate_tables
index aa36a01b5b..6f62593f14 100755
--- a/activesupport/bin/generate_tables
+++ b/activesupport/bin/generate_tables
@@ -1,7 +1,7 @@
 #!/usr/bin/env ruby
 
 begin
-  $:.unshift(File.expand_path(File.dirname(__FILE__) + "/../lib"))
+  $:.unshift(File.expand_path("../lib", __dir__))
   require "active_support"
 rescue IOError
 end
diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index 03e3ce821a..a667fbb54a 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -32,6 +32,7 @@ module ActiveSupport
   extend ActiveSupport::Autoload
 
   autoload :Concern
+  autoload :CurrentAttributes
   autoload :Dependencies
   autoload :DescendantsTracker
   autoload :ExecutionWrapper
diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 4d8c2046e8..a1093a2e23 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -88,10 +88,11 @@ module ActiveSupport
       private
         def retrieve_cache_key(key)
           case
-          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) 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
           end.to_s
         end
 
@@ -219,6 +220,10 @@ module ActiveSupport
       #   cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 5.minutes)
       #   cache.write(key, value, expires_in: 1.minute) # Set a lower value for one entry
       #
+      # Setting <tt>:version</tt> verifies the cache stored under <tt>name</tt>
+      # is of the same version. nil is returned on mismatches despite contents.
+      # This feature is used to support recyclable cache keys.
+      #
       # Setting <tt>:race_condition_ttl</tt> is very useful in situations where
       # a cache entry is used very frequently and is under heavy load. If a
       # cache expires and due to heavy load several different processes will try
@@ -287,6 +292,7 @@ module ActiveSupport
           instrument(:read, name, options) do |payload|
             cached_entry = read_entry(key, options) unless options[:force]
             entry = handle_expired_entry(cached_entry, key, options)
+            entry = nil if entry && entry.mismatched?(normalize_version(name, options))
             payload[:super_operation] = :fetch if payload
             payload[:hit] = !!entry if payload
           end
@@ -303,21 +309,30 @@ module ActiveSupport
         end
       end
 
-      # Fetches data from the cache, using the given key. If there is data in
+      # Reads data from the cache, using the given key. If there is data in
       # the cache with the given key, then that data is returned. Otherwise,
       # +nil+ is returned.
       #
+      # Note, if data was written with the <tt>:expires_in<tt> or <tt>:version</tt> options,
+      # both of these conditions are applied before the data is returned.
+      #
       # Options are passed to the underlying cache implementation.
       def read(name, options = nil)
         options = merged_options(options)
-        key = normalize_key(name, options)
+        key     = normalize_key(name, options)
+        version = normalize_version(name, options)
+
         instrument(:read, name, options) do |payload|
           entry = read_entry(key, options)
+
           if entry
             if entry.expired?
               delete_entry(key, options)
               payload[:hit] = false if payload
               nil
+            elsif entry.mismatched?(version)
+              payload[:hit] = false if payload
+              nil
             else
               payload[:hit] = true if payload
               entry.value
@@ -341,11 +356,15 @@ module ActiveSupport
 
         results = {}
         names.each do |name|
-          key = normalize_key(name, options)
-          entry = read_entry(key, options)
+          key     = normalize_key(name, options)
+          version = normalize_version(name, options)
+          entry   = read_entry(key, options)
+
           if entry
             if entry.expired?
               delete_entry(key, options)
+            elsif entry.mismatched?(version)
+              # Skip mismatched versions
             else
               results[name] = entry.value
             end
@@ -396,7 +415,7 @@ module ActiveSupport
         options = merged_options(options)
 
         instrument(:write, name, options) do
-          entry = Entry.new(value, options)
+          entry = Entry.new(value, options.merge(version: normalize_version(name, options)))
           write_entry(normalize_key(name, options), entry, options)
         end
       end
@@ -420,7 +439,7 @@ module ActiveSupport
 
         instrument(:exist?, name) do
           entry = read_entry(normalize_key(name, options), options)
-          (entry && !entry.expired?) || false
+          (entry && !entry.expired? && !entry.mismatched?(normalize_version(name, options))) || false
         end
       end
 
@@ -517,6 +536,16 @@ 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
+        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.
@@ -537,14 +566,16 @@ module ActiveSupport
           key.to_param
         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
+        def normalize_version(key, options = nil)
+          (options && options[:version].try(:to_param)) || expanded_version(key)
+        end
+
+        def expanded_version(key)
+          case
+          when key.respond_to?(:cache_version) then key.cache_version.to_param
+          when key.is_a?(Array)                then key.map { |element| expanded_version(element) }.compact.to_param
+          when key.respond_to?(:to_a)          then expanded_version(key.to_a)
+          end
         end
 
         def instrument(operation, key, options = nil)
@@ -591,13 +622,16 @@ module ActiveSupport
         end
     end
 
-    # This class is used to represent cache entries. Cache entries have a value and an optional
-    # expiration time. The expiration time is used to support the :race_condition_ttl option
-    # on the cache.
+    # This class is used to represent cache entries. Cache entries have a value, an optional
+    # expiration time, and an optional version. The expiration time is used to support the :race_condition_ttl option
+    # on the cache. The version is used to support the :version option on the cache for rejecting
+    # mismatches.
     #
     # Since cache entries in most instances will be serialized, the internals of this class are highly optimized
     # using short instance variable names that are lazily defined.
     class Entry # :nodoc:
+      attr_reader :version
+
       DEFAULT_COMPRESS_LIMIT = 16.kilobytes
 
       # Creates a new cache entry for the specified value. Options supported are
@@ -610,6 +644,7 @@ module ActiveSupport
           @value = value
         end
 
+        @version    = options[:version]
         @created_at = Time.now.to_f
         @expires_in = options[:expires_in]
         @expires_in = @expires_in.to_f if @expires_in
@@ -619,6 +654,10 @@ module ActiveSupport
         compressed? ? uncompress(@value) : @value
       end
 
+      def mismatched?(version)
+        @version && version && @version != version
+      end
+
       # Checks if the entry is expired. The +expires_in+ parameter can override
       # the value set when the entry was created.
       def expired?
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index e09cee3335..06fa9f67ad 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -97,12 +97,18 @@ module ActiveSupport
         options = merged_options(options)
 
         keys_to_names = Hash[names.map { |name| [normalize_key(name, options), name] }]
+
         raw_values = @data.get_multi(keys_to_names.keys)
         values = {}
+
         raw_values.each do |key, value|
           entry = deserialize_entry(value)
-          values[keys_to_names[key]] = entry.value unless entry.expired?
+
+          unless entry.expired? || entry.mismatched?(normalize_version(keys_to_names[key], options))
+            values[keys_to_names[key]] = entry.value
+          end
         end
+
         values
       end
 
diff --git a/activesupport/lib/active_support/cache/strategy/local_cache.rb b/activesupport/lib/active_support/cache/strategy/local_cache.rb
index 672eb2bb80..91875a56f5 100644
--- a/activesupport/lib/active_support/cache/strategy/local_cache.rb
+++ b/activesupport/lib/active_support/cache/strategy/local_cache.rb
@@ -115,7 +115,12 @@ module ActiveSupport
           end
 
           def write_entry(key, entry, options)
-            local_cache.write_entry(key, entry, options) if local_cache
+            if options[:unless_exist]
+              local_cache.delete_entry(key, options) if local_cache
+            else
+              local_cache.write_entry(key, entry, options) if local_cache
+            end
+
             super
           end
 
diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index d771cab68b..ddfa91a342 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -62,8 +62,7 @@ module ActiveSupport
 
     included do
       extend ActiveSupport::DescendantsTracker
-      class_attribute :__callbacks, instance_writer: false
-      self.__callbacks ||= {}
+      class_attribute :__callbacks, instance_writer: false, default: {}
     end
 
     CALLBACK_FILTER_TYPES = [:before, :after, :around]
diff --git a/activesupport/lib/active_support/core_ext.rb b/activesupport/lib/active_support/core_ext.rb
index f397f658f3..42e0acf66a 100644
--- a/activesupport/lib/active_support/core_ext.rb
+++ b/activesupport/lib/active_support/core_ext.rb
@@ -1,3 +1,3 @@
-(Dir["#{File.dirname(__FILE__)}/core_ext/*.rb"]).each do |path|
+Dir.glob(File.expand_path("core_ext/*.rb", __dir__)).each do |path|
   require path
 end
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index ba422f9071..8caddcd5c3 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -68,11 +68,16 @@ class Class
   #   object.setting = false  # => NoMethodError
   #
   # To opt out of both instance methods, pass <tt>instance_accessor: false</tt>.
+  #
+  # To set a default value for the attribute, pass <tt>default:</tt>, like so:
+  #
+  #   class_attribute :settings, default: {}
   def class_attribute(*attrs)
     options = attrs.extract_options!
-    instance_reader = options.fetch(:instance_accessor, true) && options.fetch(:instance_reader, true)
-    instance_writer = options.fetch(:instance_accessor, true) && options.fetch(:instance_writer, true)
+    instance_reader    = options.fetch(:instance_accessor, true) && options.fetch(:instance_reader, true)
+    instance_writer    = options.fetch(:instance_accessor, true) && options.fetch(:instance_writer, true)
     instance_predicate = options.fetch(:instance_predicate, true)
+    default_value      = options.fetch(:default, nil)
 
     attrs.each do |name|
       remove_possible_singleton_method(name)
@@ -123,6 +128,10 @@ class Class
         remove_possible_method "#{name}="
         attr_writer name
       end
+
+      unless default_value.nil?
+        self.send("#{name}=", default_value)
+      end
     end
   end
 end
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 eb8b8b2c65..870391aeaa 100644
--- a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
@@ -1,4 +1,5 @@
 require "active_support/core_ext/date_and_time/compatibility"
+require "active_support/core_ext/module/remove_method"
 
 class DateTime
   include DateAndTime::Compatibility
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index 85ab739095..13f3894e6c 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -219,48 +219,43 @@ class Module
   # When building decorators, a common pattern may emerge:
   #
   #   class Partition
-  #     def initialize(first_event)
-  #       @events = [ first_event ]
+  #     def initialize(event)
+  #       @event = event
   #     end
   #
-  #     def people
-  #       if @events.first.detail.people.any?
-  #         @events.collect { |e| Array(e.detail.people) }.flatten.uniq
-  #       else
-  #         @events.collect(&:creator).uniq
-  #       end
+  #     def person
+  #       @event.detail.person || @event.creator
   #     end
   #
   #     private
   #       def respond_to_missing?(name, include_private = false)
-  #         @events.respond_to?(name, include_private)
+  #         @event.respond_to?(name, include_private)
   #       end
   #
   #       def method_missing(method, *args, &block)
-  #         @events.send(method, *args, &block)
+  #         @event.send(method, *args, &block)
   #       end
   #   end
   #
-  # With `Module#delegate_missing_to`, the above is condensed to:
+  # With <tt>Module#delegate_missing_to</tt>, the above is condensed to:
   #
   #   class Partition
-  #     delegate_missing_to :@events
+  #     delegate_missing_to :@event
   #
-  #     def initialize(first_event)
-  #       @events = [ first_event ]
+  #     def initialize(event)
+  #       @event = event
   #     end
   #
-  #     def people
-  #       if @events.first.detail.people.any?
-  #         @events.collect { |e| Array(e.detail.people) }.flatten.uniq
-  #       else
-  #         @events.collect(&:creator).uniq
-  #       end
+  #     def person
+  #       @event.detail.person || @event.creator
   #     end
   #   end
   #
-  # The target can be anything callable within the object. E.g. instance
-  # variables, methods, constants and the likes.
+  # The target can be anything callable within the object, e.g. instance
+  # variables, methods, constants, etc.
+  #
+  # The delegated method must be public on the target, otherwise it will
+  # raise +NoMethodError+.
   def delegate_missing_to(target)
     target = target.to_s
     target = "self.#{target}" if DELEGATION_RESERVED_METHOD_NAMES.include?(target)
diff --git a/activesupport/lib/active_support/current_attributes.rb b/activesupport/lib/active_support/current_attributes.rb
new file mode 100644
index 0000000000..872b0663c7
--- /dev/null
+++ b/activesupport/lib/active_support/current_attributes.rb
@@ -0,0 +1,193 @@
+module ActiveSupport
+  # Abstract super class that provides a thread-isolated attributes singleton, which resets automatically
+  # before and after each request. This allows you to keep all the per-request attributes easily
+  # available to the whole system.
+  #
+  # The following full app-like example demonstrates how to use a Current class to
+  # facilitate easy access to the global, per-request attributes without passing them deeply
+  # around everywhere:
+  #
+  #   # app/models/current.rb
+  #   class Current < ActiveSupport::CurrentAttributes
+  #     attribute :account, :user
+  #     attribute :request_id, :user_agent, :ip_address
+  #
+  #     resets { Time.zone = nil }
+  #
+  #     def user=(user)
+  #       super
+  #       self.account = user.account
+  #       Time.zone    = user.time_zone
+  #     end
+  #   end
+  #
+  #   # app/controllers/concerns/authentication.rb
+  #   module Authentication
+  #     extend ActiveSupport::Concern
+  #
+  #     included do
+  #       before_action :authenticate
+  #     end
+  #
+  #     private
+  #       def authenticate
+  #         if authenticated_user = User.find_by(id: cookies.signed[:user_id])
+  #           Current.user = authenticated_user
+  #         else
+  #           redirect_to new_session_url
+  #         end
+  #       end
+  #   end
+  #
+  #   # app/controllers/concerns/set_current_request_details.rb
+  #   module SetCurrentRequestDetails
+  #     extend ActiveSupport::Concern
+  #
+  #     included do
+  #       before_action do
+  #         Current.request_id = request.uuid
+  #         Current.user_agent = request.user_agent
+  #         Current.ip_address = request.ip
+  #       end
+  #     end
+  #   end
+  #
+  #   class ApplicationController < ActionController::Base
+  #     include Authentication
+  #     include SetCurrentRequestDetails
+  #   end
+  #
+  #   class MessagesController < ApplicationController
+  #     def create
+  #       Current.account.messages.create(message_params)
+  #     end
+  #   end
+  #
+  #   class Message < ApplicationRecord
+  #     belongs_to :creator, default: -> { Current.user }
+  #     after_create { |message| Event.create(record: message) }
+  #   end
+  #
+  #   class Event < ApplicationRecord
+  #     before_create do
+  #       self.request_id = Current.request_id
+  #       self.user_agent = Current.user_agent
+  #       self.ip_address = Current.ip_address
+  #     end
+  #   end
+  #
+  # A word of caution: It's easy to overdo a global singleton like Current and tangle your model as a result.
+  # Current should only be used for a few, top-level globals, like account, user, and request details.
+  # The attributes stuck in Current should be used by more or less all actions on all requests. If you start
+  # sticking controller-specific attributes in there, you're going to create a mess.
+  class CurrentAttributes
+    include ActiveSupport::Callbacks
+    define_callbacks :reset
+
+    class << self
+      # Returns singleton instance for this class in this thread. If none exists, one is created.
+      def instance
+        current_instances[name] ||= new
+      end
+
+      # Declares one or more attributes that will be given both class and instance accessor methods.
+      def attribute(*names)
+        generated_attribute_methods.module_eval do
+          names.each do |name|
+            define_method(name) do
+              attributes[name.to_sym]
+            end
+
+            define_method("#{name}=") do |attribute|
+              attributes[name.to_sym] = attribute
+            end
+          end
+        end
+
+        names.each do |name|
+          define_singleton_method(name) do
+            instance.public_send(name)
+          end
+
+          define_singleton_method("#{name}=") do |attribute|
+            instance.public_send("#{name}=", attribute)
+          end
+        end
+      end
+
+      # Calls this block after #reset is called on the instance. Used for resetting external collaborators, like Time.zone.
+      def resets(&block)
+        set_callback :reset, :after, &block
+      end
+
+      delegate :set, :reset, to: :instance
+
+      def reset_all # :nodoc:
+        current_instances.each_value(&:reset)
+      end
+
+      def clear_all # :nodoc:
+        reset_all
+        current_instances.clear
+      end
+
+      private
+        def generated_attribute_methods
+          @generated_attribute_methods ||= Module.new.tap { |mod| include mod }
+        end
+
+        def current_instances
+          Thread.current[:current_attributes_instances] ||= {}
+        end
+
+        def method_missing(name, *args, &block)
+          # Caches the method definition as a singleton method of the receiver.
+          #
+          # By letting #delegate handle it, we avoid an enclosure that'll capture args.
+          singleton_class.delegate name, to: :instance
+
+          send(name, *args, &block)
+        end
+    end
+
+    attr_accessor :attributes
+
+    def initialize
+      @attributes = {}
+    end
+
+    # Expose one or more attributes within a block. Old values are returned after the block concludes.
+    # Example demonstrating the common use of needing to set Current attributes outside the request-cycle:
+    #
+    #   class Chat::PublicationJob < ApplicationJob
+    #     def perform(attributes, room_number, creator)
+    #       Current.set(person: creator) do
+    #         Chat::Publisher.publish(attributes: attributes, room_number: room_number)
+    #       end
+    #     end
+    #   end
+    def set(set_attributes)
+      old_attributes = compute_attributes(set_attributes.keys)
+      assign_attributes(set_attributes)
+      yield
+    ensure
+      assign_attributes(old_attributes)
+    end
+
+    # Reset all attributes. Should be called before and after actions, when used as a per-request singleton.
+    def reset
+      run_callbacks :reset do
+        self.attributes = {}
+      end
+    end
+
+    private
+      def assign_attributes(new_attributes)
+        new_attributes.each { |key, value| public_send("#{key}=", value) }
+      end
+
+      def compute_attributes(keys)
+        keys.collect { |key| [ key, public_send(key) ] }.to_h
+      end
+  end
+end
diff --git a/activesupport/lib/active_support/deprecation/reporting.rb b/activesupport/lib/active_support/deprecation/reporting.rb
index 851d8eeda1..140bdccbb3 100644
--- a/activesupport/lib/active_support/deprecation/reporting.rb
+++ b/activesupport/lib/active_support/deprecation/reporting.rb
@@ -102,7 +102,7 @@ module ActiveSupport
           end
         end
 
-        RAILS_GEM_ROOT = File.expand_path("../../../../..", __FILE__) + "/"
+        RAILS_GEM_ROOT = File.expand_path("../../../..", __dir__)
 
         def ignored_callstack(path)
           path.start_with?(RAILS_GEM_ROOT) || path.start_with?(RbConfig::CONFIG["rubylibdir"])
diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
index d4424ed792..39deb2313f 100644
--- a/activesupport/lib/active_support/duration.rb
+++ b/activesupport/lib/active_support/duration.rb
@@ -37,27 +37,56 @@ module ActiveSupport
       end
 
       def +(other)
-        calculate(:+, other)
+        if Duration === other
+          seconds   = value + other.parts[:seconds]
+          new_parts = other.parts.merge(seconds: seconds)
+          new_value = value + other.value
+
+          Duration.new(new_value, new_parts)
+        else
+          calculate(:+, other)
+        end
       end
 
       def -(other)
-        calculate(:-, other)
+        if Duration === other
+          seconds   = value - other.parts[:seconds]
+          new_parts = other.parts.map { |part, other_value| [part, -other_value] }.to_h
+          new_parts = new_parts.merge(seconds: seconds)
+          new_value = value - other.value
+
+          Duration.new(new_value, new_parts)
+        else
+          calculate(:-, other)
+        end
       end
 
       def *(other)
-        calculate(:*, other)
+        if Duration === other
+          new_parts = other.parts.map { |part, other_value| [part, value * other_value] }.to_h
+          new_value = value * other.value
+
+          Duration.new(new_value, new_parts)
+        else
+          calculate(:*, other)
+        end
       end
 
       def /(other)
-        calculate(:/, other)
+        if Duration === other
+          new_parts = other.parts.map { |part, other_value| [part, value / other_value] }.to_h
+          new_value = new_parts.inject(0) { |total, (part, value)| total + value * Duration::PARTS_IN_SECONDS[part] }
+
+          Duration.new(new_value, new_parts)
+        else
+          calculate(:/, other)
+        end
       end
 
       private
         def calculate(op, other)
           if Scalar === other
             Scalar.new(value.public_send(op, other.value))
-          elsif Duration === other
-            Duration.seconds(value).public_send(op, other)
           elsif Numeric === other
             Scalar.new(value.public_send(op, other))
           else
diff --git a/activesupport/lib/active_support/i18n.rb b/activesupport/lib/active_support/i18n.rb
index f0408f429c..1a1f1a1257 100644
--- a/activesupport/lib/active_support/i18n.rb
+++ b/activesupport/lib/active_support/i18n.rb
@@ -10,4 +10,4 @@ end
 require "active_support/lazy_load_hooks"
 
 ActiveSupport.run_load_hooks(:i18n)
-I18n.load_path << "#{File.dirname(__FILE__)}/locale/en.yml"
+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 b749913ee9..51fe6f3418 100644
--- a/activesupport/lib/active_support/i18n_railtie.rb
+++ b/activesupport/lib/active_support/i18n_railtie.rb
@@ -42,7 +42,7 @@ module I18n
         case setting
         when :railties_load_path
           reloadable_paths = value
-          app.config.i18n.load_path.unshift(*value.map(&:existent).flatten)
+          app.config.i18n.load_path.unshift(*value.flat_map(&:existent))
         when :load_path
           I18n.load_path += value
         else
@@ -58,7 +58,7 @@ module I18n
       directories = watched_dirs_with_extensions(reloadable_paths)
       reloader = app.config.file_watcher.new(I18n.load_path.dup, directories) do
         I18n.load_path.keep_if { |p| File.exist?(p) }
-        I18n.load_path |= reloadable_paths.map(&:existent).flatten
+        I18n.load_path |= reloadable_paths.flat_map(&:existent)
 
         I18n.reload!
       end
@@ -66,10 +66,6 @@ module I18n
       app.reloaders << reloader
       app.reloader.to_run do
         reloader.execute_if_updated { require_unload_lock! }
-        # TODO: remove the following line as soon as the return value of
-        # callbacks is ignored, that is, returning `false` does not
-        # display a deprecation warning or halts the callback chain.
-        true
       end
       reloader.execute
 
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 1b089a7538..ff1a0cb8c7 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -28,7 +28,7 @@ module ActiveSupport
     #   pluralize('CamelOctopus')     # => "CamelOctopi"
     #   pluralize('ley', :es)         # => "leyes"
     def pluralize(word, locale = :en)
-      apply_inflections(word, inflections(locale).plurals)
+      apply_inflections(word, inflections(locale).plurals, locale)
     end
 
     # The reverse of #pluralize, returns the singular form of a word in a
@@ -45,7 +45,7 @@ module ActiveSupport
     #   singularize('CamelOctopi')      # => "CamelOctopus"
     #   singularize('leyes', :es)       # => "ley"
     def singularize(word, locale = :en)
-      apply_inflections(word, inflections(locale).singulars)
+      apply_inflections(word, inflections(locale).singulars, locale)
     end
 
     # Converts strings to UpperCamelCase.
@@ -387,12 +387,15 @@ module ActiveSupport
 
       # Applies inflection rules for +singularize+ and +pluralize+.
       #
-      #  apply_inflections('post', inflections.plurals)    # => "posts"
-      #  apply_inflections('posts', inflections.singulars) # => "post"
-      def apply_inflections(word, rules)
+      # If passed an optional +locale+ parameter, the uncountables will be
+      # found for that locale.
+      #
+      #  apply_inflections('post', inflections.plurals, :en)    # => "posts"
+      #  apply_inflections('posts', inflections.singulars, :en) # => "post"
+      def apply_inflections(word, rules, locale = :en)
         result = word.to_s.dup
 
-        if word.empty? || inflections.uncountables.uncountable?(result)
+        if word.empty? || inflections(locale).uncountables.uncountable?(result)
           result
         else
           rules.each { |(rule, replacement)| break if result.sub!(rule, replacement) }
diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb
index 24053b4fe5..726e1464ad 100644
--- a/activesupport/lib/active_support/message_encryptor.rb
+++ b/activesupport/lib/active_support/message_encryptor.rb
@@ -115,7 +115,7 @@ module ActiveSupport
         # Currently the OpenSSL bindings do not raise an error if auth_tag is
         # truncated, which would allow an attacker to easily forge it. See
         # https://github.com/ruby/openssl/issues/63
-        raise InvalidMessage if aead_mode? && auth_tag.bytes.length != 16
+        raise InvalidMessage if aead_mode? && (auth_tag.nil? || auth_tag.bytes.length != 16)
 
         cipher.decrypt
         cipher.key = @secret
diff --git a/activesupport/lib/active_support/multibyte/unicode.rb b/activesupport/lib/active_support/multibyte/unicode.rb
index 0912912aba..8223e45e5a 100644
--- a/activesupport/lib/active_support/multibyte/unicode.rb
+++ b/activesupport/lib/active_support/multibyte/unicode.rb
@@ -357,7 +357,7 @@ module ActiveSupport
 
         # Returns the directory in which the data files are stored.
         def self.dirname
-          File.dirname(__FILE__) + "/../values/"
+          File.expand_path("../values", __dir__)
         end
 
         # Returns the filename for the data file for this version.
diff --git a/activesupport/lib/active_support/number_helper.rb b/activesupport/lib/active_support/number_helper.rb
index 880340ca86..9cb2821cb6 100644
--- a/activesupport/lib/active_support/number_helper.rb
+++ b/activesupport/lib/active_support/number_helper.rb
@@ -4,6 +4,7 @@ module ActiveSupport
 
     eager_autoload do
       autoload :NumberConverter
+      autoload :RoundingHelper
       autoload :NumberToRoundedConverter
       autoload :NumberToDelimitedConverter
       autoload :NumberToHumanConverter
diff --git a/activesupport/lib/active_support/number_helper/number_to_human_converter.rb b/activesupport/lib/active_support/number_helper/number_to_human_converter.rb
index 56185ddf4b..040343b5dd 100644
--- a/activesupport/lib/active_support/number_helper/number_to_human_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_human_converter.rb
@@ -9,6 +9,7 @@ module ActiveSupport
       self.validate_float = true
 
       def convert # :nodoc:
+        @number = RoundingHelper.new(options).round(number)
         @number = Float(number)
 
         # for backwards compatibility with those that didn't add strip_insignificant_zeros to their locale files
@@ -20,10 +21,7 @@ module ActiveSupport
         exponent = calculate_exponent(units)
         @number = number / (10**exponent)
 
-        until (rounded_number = NumberToRoundedConverter.convert(number, options)) != NumberToRoundedConverter.convert(1000, options)
-          @number = number / 1000.0
-          exponent += 3
-        end
+        rounded_number = NumberToRoundedConverter.convert(number, options)
         unit = determine_unit(units, exponent)
         format.gsub("%n".freeze, rounded_number).gsub("%u".freeze, unit).strip
       end
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 1f013990ea..c32d85a45f 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
@@ -5,26 +5,14 @@ module ActiveSupport
       self.validate_float = true
 
       def convert
-        precision = options.delete :precision
+        helper = RoundingHelper.new(options)
+        rounded_number = helper.round(number)
 
-        if precision
-          case number
-          when Float, String
-            @number = BigDecimal(number.to_s)
-          when Rational
-            @number = BigDecimal(number, digit_count(number.to_i) + precision)
-          else
-            @number = number.to_d
-          end
-
-          if options.delete(:significant) && precision > 0
-            digits, rounded_number = digits_and_rounded_number(precision)
+        if precision = options[:precision]
+          if options[:significant] && precision > 0
+            digits = helper.digit_count(rounded_number)
             precision -= digits
             precision = 0 if precision < 0 # don't let it be negative
-          else
-            rounded_number = number.round(precision)
-            rounded_number = rounded_number.to_i if precision == 0 && rounded_number.finite?
-            rounded_number = rounded_number.abs if rounded_number.zero? # prevent showing negative zeros
           end
 
           formatted_string =
@@ -38,7 +26,7 @@ module ActiveSupport
               "%00.#{precision}f" % rounded_number
             end
         else
-          formatted_string = number
+          formatted_string = rounded_number
         end
 
         delimited_number = NumberToDelimitedConverter.convert(formatted_string, options)
@@ -79,14 +67,6 @@ module ActiveSupport
             number
           end
         end
-
-        def absolute_number(number)
-          number.respond_to?(:abs) ? number.abs : number.to_d.abs
-        end
-
-        def zero?
-          number.respond_to?(:zero?) ? number.zero? : number.to_d.zero?
-        end
     end
   end
 end
diff --git a/activesupport/lib/active_support/number_helper/rounding_helper.rb b/activesupport/lib/active_support/number_helper/rounding_helper.rb
new file mode 100644
index 0000000000..d9644df17d
--- /dev/null
+++ b/activesupport/lib/active_support/number_helper/rounding_helper.rb
@@ -0,0 +1,64 @@
+module ActiveSupport
+  module NumberHelper
+    class RoundingHelper # :nodoc:
+      attr_reader :options
+
+      def initialize(options)
+        @options = options
+      end
+
+      def round(number)
+        return number unless precision
+        number = convert_to_decimal(number)
+        if significant && precision > 0
+          round_significant(number)
+        else
+          round_without_significant(number)
+        end
+      end
+
+      def digit_count(number)
+        return 1 if number.zero?
+        (Math.log10(absolute_number(number)) + 1).floor
+      end
+
+      private
+        def round_without_significant(number)
+          number = number.round(precision)
+          number = number.to_i if precision == 0 && number.finite?
+          number = number.abs if number.zero? # prevent showing negative zeros
+          number
+        end
+
+        def round_significant(number)
+          return 0 if number.zero?
+          digits = digit_count(number)
+          multiplier = 10**(digits - precision)
+          (number / BigDecimal.new(multiplier.to_f.to_s)).round * multiplier
+        end
+
+        def convert_to_decimal(number)
+          case number
+          when Float, String
+            number = BigDecimal(number.to_s)
+          when Rational
+            number = BigDecimal(number, digit_count(number.to_i) + precision)
+          else
+            number = number.to_d
+          end
+        end
+
+        def precision
+          options[:precision]
+        end
+
+        def significant
+          options[:significant]
+        end
+
+        def absolute_number(number)
+          number.respond_to?(:abs) ? number.abs : number.to_d.abs
+        end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index b875875afe..1b4ecf4d72 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -7,6 +7,12 @@ module ActiveSupport
 
     config.eager_load_namespaces << ActiveSupport
 
+    initializer "active_support.reset_all_current_attributes_instances" do |app|
+      app.reloader.before_class_unload { ActiveSupport::CurrentAttributes.clear_all }
+      app.executor.to_run              { ActiveSupport::CurrentAttributes.reset_all }
+      app.executor.to_complete         { ActiveSupport::CurrentAttributes.reset_all }
+    end
+
     initializer "active_support.deprecation_behavior" do |app|
       if deprecation = app.config.active_support.deprecation
         ActiveSupport::Deprecation.behavior = deprecation
diff --git a/activesupport/lib/active_support/reloader.rb b/activesupport/lib/active_support/reloader.rb
index 121c621751..9558146201 100644
--- a/activesupport/lib/active_support/reloader.rb
+++ b/activesupport/lib/active_support/reloader.rb
@@ -69,11 +69,8 @@ module ActiveSupport
       end
     end
 
-    class_attribute :executor
-    class_attribute :check
-
-    self.executor = Executor
-    self.check = lambda { false }
+    class_attribute :executor, default: Executor
+    class_attribute :check, default: lambda { false }
 
     def self.check! # :nodoc:
       @should_reload ||= check.call
diff --git a/activesupport/lib/active_support/rescuable.rb b/activesupport/lib/active_support/rescuable.rb
index ee6592fb5a..826832ba7d 100644
--- a/activesupport/lib/active_support/rescuable.rb
+++ b/activesupport/lib/active_support/rescuable.rb
@@ -8,8 +8,7 @@ module ActiveSupport
     extend Concern
 
     included do
-      class_attribute :rescue_handlers
-      self.rescue_handlers = []
+      class_attribute :rescue_handlers, default: []
     end
 
     module ClassMethods
@@ -84,12 +83,18 @@ module ActiveSupport
       #     end
       #
       # Returns the exception if it was handled and +nil+ if it was not.
-      def rescue_with_handler(exception, object: self)
+      def rescue_with_handler(exception, object: self, visited_exceptions: [])
+        visited_exceptions << exception
+
         if handler = handler_for_rescue(exception, object: object)
           handler.call exception
           exception
         elsif exception
-          rescue_with_handler(exception.cause, object: object)
+          if visited_exceptions.include?(exception.cause)
+            nil
+          else
+            rescue_with_handler(exception.cause, object: object, visited_exceptions: visited_exceptions)
+          end
         end
       end
 
diff --git a/activesupport/test/caching_test.rb b/activesupport/test/caching_test.rb
index c67ffe69b8..f53b98c73e 100644
--- a/activesupport/test/caching_test.rb
+++ b/activesupport/test/caching_test.rb
@@ -579,6 +579,93 @@ module CacheStoreBehavior
   end
 end
 
+module CacheStoreVersionBehavior
+  ModelWithKeyAndVersion = Struct.new(:cache_key, :cache_version)
+
+  def test_fetch_with_right_version_should_hit
+    @cache.fetch("foo", version: 1) { "bar" }
+    assert_equal "bar", @cache.read("foo", version: 1)
+  end
+
+  def test_fetch_with_wrong_version_should_miss
+    @cache.fetch("foo", version: 1) { "bar" }
+    assert_nil @cache.read("foo", version: 2)
+  end
+
+  def test_read_with_right_version_should_hit
+    @cache.write("foo", "bar", version: 1)
+    assert_equal "bar", @cache.read("foo", version: 1)
+  end
+
+  def test_read_with_wrong_version_should_miss
+    @cache.write("foo", "bar", version: 1)
+    assert_nil @cache.read("foo", version: 2)
+  end
+
+  def test_exist_with_right_version_should_be_true
+    @cache.write("foo", "bar", version: 1)
+    assert @cache.exist?("foo", version: 1)
+  end
+
+  def test_exist_with_wrong_version_should_be_false
+    @cache.write("foo", "bar", version: 1)
+    assert !@cache.exist?("foo", version: 2)
+  end
+
+  def test_reading_and_writing_with_model_supporting_cache_version
+    m1v1 = ModelWithKeyAndVersion.new("model/1", 1)
+    m1v2 = ModelWithKeyAndVersion.new("model/1", 2)
+
+    @cache.write(m1v1, "bar")
+    assert_equal "bar", @cache.read(m1v1)
+    assert_nil @cache.read(m1v2)
+  end
+
+  def test_reading_and_writing_with_model_supporting_cache_version_using_nested_key
+    m1v1 = ModelWithKeyAndVersion.new("model/1", 1)
+    m1v2 = ModelWithKeyAndVersion.new("model/1", 2)
+
+    @cache.write([ "something", m1v1 ], "bar")
+    assert_equal "bar", @cache.read([ "something", m1v1 ])
+    assert_nil @cache.read([ "something", m1v2 ])
+  end
+
+  def test_fetching_with_model_supporting_cache_version
+    m1v1 = ModelWithKeyAndVersion.new("model/1", 1)
+    m1v2 = ModelWithKeyAndVersion.new("model/1", 2)
+
+    @cache.fetch(m1v1) { "bar" }
+    assert_equal "bar", @cache.fetch(m1v1) { "bu" }
+    assert_equal "bu", @cache.fetch(m1v2) { "bu" }
+  end
+
+  def test_exist_with_model_supporting_cache_version
+    m1v1 = ModelWithKeyAndVersion.new("model/1", 1)
+    m1v2 = ModelWithKeyAndVersion.new("model/1", 2)
+
+    @cache.write(m1v1, "bar")
+    assert     @cache.exist?(m1v1)
+    assert_not @cache.fetch(m1v2)
+  end
+
+  def test_fetch_multi_with_model_supporting_cache_version
+    m1v1 = ModelWithKeyAndVersion.new("model/1", 1)
+    m2v1 = ModelWithKeyAndVersion.new("model/2", 1)
+    m2v2 = ModelWithKeyAndVersion.new("model/2", 2)
+
+    first_fetch_values  = @cache.fetch_multi(m1v1, m2v1) { |m| m.cache_key }
+    second_fetch_values = @cache.fetch_multi(m1v1, m2v2) { |m| m.cache_key + " 2nd" }
+
+    assert_equal({ m1v1 => "model/1", m2v1 => "model/2" }, first_fetch_values)
+    assert_equal({ m1v1 => "model/1", m2v2 => "model/2 2nd" }, second_fetch_values)
+  end
+
+  def test_version_is_normalized
+    @cache.write("foo", "bar", version: 1)
+    assert_equal "bar", @cache.read("foo", version: "1")
+  end
+end
+
 # https://rails.lighthouseapp.com/projects/8994/tickets/6225-memcachestore-cant-deal-with-umlauts-and-special-characters
 # The error is caused by character encodings that can't be compared with ASCII-8BIT regular expressions and by special
 # characters like the umlaut in UTF-8.
@@ -708,6 +795,14 @@ module LocalCacheBehavior
     end
   end
 
+  def test_local_cache_of_write_with_unless_exist
+    @cache.with_local_cache do
+      @cache.write("foo", "bar")
+      @cache.write("foo", "baz", unless_exist: true)
+      assert_equal @peek.read("foo"), @cache.read("foo")
+    end
+  end
+
   def test_local_cache_of_delete
     @cache.with_local_cache do
       @cache.write("foo", "bar")
@@ -814,6 +909,7 @@ class FileStoreTest < ActiveSupport::TestCase
   end
 
   include CacheStoreBehavior
+  include CacheStoreVersionBehavior
   include LocalCacheBehavior
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
@@ -923,6 +1019,7 @@ class MemoryStoreTest < ActiveSupport::TestCase
   end
 
   include CacheStoreBehavior
+  include CacheStoreVersionBehavior
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
 
@@ -1044,6 +1141,7 @@ class MemCacheStoreTest < ActiveSupport::TestCase
   end
 
   include CacheStoreBehavior
+  include CacheStoreVersionBehavior
   include LocalCacheBehavior
   include CacheIncrementDecrementBehavior
   include EncodedKeyCacheBehavior
diff --git a/activesupport/test/core_ext/class/attribute_test.rb b/activesupport/test/core_ext/class/attribute_test.rb
index 5a9ec78cc1..f16043c612 100644
--- a/activesupport/test/core_ext/class/attribute_test.rb
+++ b/activesupport/test/core_ext/class/attribute_test.rb
@@ -3,7 +3,11 @@ require "active_support/core_ext/class/attribute"
 
 class ClassAttributeTest < ActiveSupport::TestCase
   def setup
-    @klass = Class.new { class_attribute :setting }
+    @klass = Class.new do
+      class_attribute :setting
+      class_attribute :timeout, default: 5
+    end
+
     @sub = Class.new(@klass)
   end
 
@@ -12,6 +16,10 @@ class ClassAttributeTest < ActiveSupport::TestCase
     assert_nil @sub.setting
   end
 
+  test "custom default" do
+    assert_equal 5, @klass.timeout
+  end
+
   test "inheritable" do
     @klass.setting = 1
     assert_equal 1, @sub.setting
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
index 1648a9b270..3108f24f21 100644
--- a/activesupport/test/core_ext/duration_test.rb
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -337,6 +337,13 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal "no implicit conversion of String into ActiveSupport::Duration::Scalar", exception.message
   end
 
+  def test_scalar_plus_parts
+    scalar = ActiveSupport::Duration::Scalar.new(10)
+
+    assert_equal({ days: 1, seconds: 10 }, (scalar + 1.day).parts)
+    assert_equal({ days: -1, seconds: 10 }, (scalar + -1.day).parts)
+  end
+
   def test_scalar_minus
     scalar = ActiveSupport::Duration::Scalar.new(10)
 
@@ -349,6 +356,9 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal 5, scalar - 5.seconds
     assert_instance_of ActiveSupport::Duration, scalar - 5.seconds
 
+    assert_equal({ days: -1, seconds: 10 }, (scalar - 1.day).parts)
+    assert_equal({ days: 1, seconds: 10 }, (scalar - -1.day).parts)
+
     exception = assert_raises(TypeError) do
       scalar - "foo"
     end
@@ -356,6 +366,13 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal "no implicit conversion of String into ActiveSupport::Duration::Scalar", exception.message
   end
 
+  def test_scalar_minus_parts
+    scalar = ActiveSupport::Duration::Scalar.new(10)
+
+    assert_equal({ days: -1, seconds: 10 }, (scalar - 1.day).parts)
+    assert_equal({ days: 1, seconds: 10 }, (scalar - -1.day).parts)
+  end
+
   def test_scalar_multiply
     scalar = ActiveSupport::Duration::Scalar.new(5)
 
@@ -375,6 +392,14 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal "no implicit conversion of String into ActiveSupport::Duration::Scalar", exception.message
   end
 
+  def test_scalar_multiply_parts
+    scalar = ActiveSupport::Duration::Scalar.new(1)
+    assert_equal({ days: 2 }, (scalar * 2.days).parts)
+    assert_equal(172800, (scalar * 2.days).value)
+    assert_equal({ days: -2 }, (scalar * -2.days).parts)
+    assert_equal(-172800, (scalar * -2.days).value)
+  end
+
   def test_scalar_divide
     scalar = ActiveSupport::Duration::Scalar.new(10)
 
@@ -394,6 +419,15 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal "no implicit conversion of String into ActiveSupport::Duration::Scalar", exception.message
   end
 
+  def test_scalar_divide_parts
+    scalar = ActiveSupport::Duration::Scalar.new(10)
+
+    assert_equal({ days: 2 }, (scalar / 5.days).parts)
+    assert_equal(172800, (scalar / 5.days).value)
+    assert_equal({ days: -2 }, (scalar / -5.days).parts)
+    assert_equal(-172800, (scalar / -5.days).value)
+  end
+
   def test_twelve_months_equals_one_year
     assert_equal 12.months, 1.year
   end
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index 085fd6592d..a4d4444d69 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -348,15 +348,15 @@ class ModuleTest < ActiveSupport::TestCase
     assert has_block.hello?
   end
 
-  def test_delegate_to_missing_with_method
+  def test_delegate_missing_to_with_method
     assert_equal "David", DecoratedTester.new(@david).name
   end
 
-  def test_delegate_to_missing_with_reserved_methods
+  def test_delegate_missing_to_with_reserved_methods
     assert_equal "David", DecoratedReserved.new(@david).name
   end
 
-  def test_delegate_to_missing_does_not_delegate_to_private_methods
+  def test_delegate_missing_to_does_not_delegate_to_private_methods
     e = assert_raises(NoMethodError) do
       DecoratedReserved.new(@david).private_name
     end
@@ -364,7 +364,7 @@ class ModuleTest < ActiveSupport::TestCase
     assert_match(/undefined method `private_name' for/, e.message)
   end
 
-  def test_delegate_to_missing_does_not_delegate_to_fake_methods
+  def test_delegate_missing_to_does_not_delegate_to_fake_methods
     e = assert_raises(NoMethodError) do
       DecoratedReserved.new(@david).my_fake_method
     end
@@ -372,7 +372,7 @@ class ModuleTest < ActiveSupport::TestCase
     assert_match(/undefined method `my_fake_method' for/, e.message)
   end
 
-  def test_delegate_to_missing_affects_respond_to
+  def test_delegate_missing_to_affects_respond_to
     assert DecoratedTester.new(@david).respond_to?(:name)
     assert_not DecoratedTester.new(@david).respond_to?(:private_name)
     assert_not DecoratedTester.new(@david).respond_to?(:my_fake_method)
@@ -382,7 +382,7 @@ class ModuleTest < ActiveSupport::TestCase
     assert_not DecoratedTester.new(@david).respond_to?(:my_fake_method, true)
   end
 
-  def test_delegate_to_missing_respects_superclass_missing
+  def test_delegate_missing_to_respects_superclass_missing
     assert_equal 42, DecoratedTester.new(@david).extra_missing
 
     assert_respond_to DecoratedTester.new(@david), :extra_missing
diff --git a/activesupport/test/current_attributes_test.rb b/activesupport/test/current_attributes_test.rb
new file mode 100644
index 0000000000..67ef6ef619
--- /dev/null
+++ b/activesupport/test/current_attributes_test.rb
@@ -0,0 +1,96 @@
+require "abstract_unit"
+
+class CurrentAttributesTest < ActiveSupport::TestCase
+  Person = Struct.new(:name, :time_zone)
+
+  class Current < ActiveSupport::CurrentAttributes
+    attribute :world, :account, :person, :request
+    delegate :time_zone, to: :person
+
+    resets { Time.zone = "UTC" }
+
+    def account=(account)
+      super
+      self.person = "#{account}'s person"
+    end
+
+    def person=(person)
+      super
+      Time.zone = person.try(:time_zone)
+    end
+
+    def request
+      "#{super} something"
+    end
+
+    def intro
+      "#{person.name}, in #{time_zone}"
+    end
+  end
+
+  setup { Current.reset }
+
+  test "read and write attribute" do
+    Current.world = "world/1"
+    assert_equal "world/1", Current.world
+  end
+
+  test "read overwritten attribute method" do
+    Current.request = "request/1"
+    assert_equal "request/1 something", Current.request
+  end
+
+  test "set attribute via overwritten method" do
+    Current.account = "account/1"
+    assert_equal "account/1", Current.account
+    assert_equal "account/1's person", Current.person
+  end
+
+  test "set auxiliary class via overwritten method" do
+    Current.person = Person.new("David", "Central Time (US & Canada)")
+    assert_equal "Central Time (US & Canada)", Time.zone.name
+  end
+
+  test "resets auxiliary class via callback" do
+    Current.person = Person.new("David", "Central Time (US & Canada)")
+    assert_equal "Central Time (US & Canada)", Time.zone.name
+
+    Current.reset
+    assert_equal "UTC", Time.zone.name
+  end
+
+  test "set attribute only via scope" do
+    Current.world = "world/1"
+
+    Current.set(world: "world/2") do
+      assert_equal "world/2", Current.world
+    end
+
+    assert_equal "world/1", Current.world
+  end
+
+  test "set multiple attributes" do
+    Current.world = "world/1"
+    Current.account = "account/1"
+
+    Current.set(world: "world/2", account: "account/2") do
+      assert_equal "world/2", Current.world
+      assert_equal "account/2", Current.account
+    end
+
+    assert_equal "world/1", Current.world
+    assert_equal "account/1", Current.account
+  end
+
+  test "delegation" do
+    Current.person = Person.new("David", "Central Time (US & Canada)")
+    assert_equal "Central Time (US & Canada)", Current.time_zone
+    assert_equal "Central Time (US & Canada)", Current.instance.time_zone
+  end
+
+  test "all methods forward to the instance" do
+    Current.person = Person.new("David", "Central Time (US & Canada)")
+    assert_equal "David, in Central Time (US & Canada)", Current.intro
+    assert_equal "David, in Central Time (US & Canada)", Current.instance.intro
+  end
+end
diff --git a/activesupport/test/dependencies_test.rb b/activesupport/test/dependencies_test.rb
index e38d4e83e5..1ea36418ff 100644
--- a/activesupport/test/dependencies_test.rb
+++ b/activesupport/test/dependencies_test.rb
@@ -104,7 +104,7 @@ class DependenciesTest < ActiveSupport::TestCase
     with_loading "dependencies" do
       old_warnings, ActiveSupport::Dependencies.warnings_on_first_load = ActiveSupport::Dependencies.warnings_on_first_load, true
       filename = "check_warnings"
-      expanded = File.expand_path("#{File.dirname(__FILE__)}/dependencies/#{filename}")
+      expanded = File.expand_path("dependencies/#{filename}", __dir__)
       $check_warnings_load_count = 0
 
       assert_not ActiveSupport::Dependencies.loaded.include?(expanded)
@@ -293,7 +293,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_doesnt_break_normal_require
-    path = File.expand_path("../autoloading_fixtures/load_path", __FILE__)
+    path = File.expand_path("autoloading_fixtures/load_path", __dir__)
     original_path = $:.dup
     $:.push(path)
     with_autoloading_fixtures do
@@ -312,7 +312,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_doesnt_break_normal_require_nested
-    path = File.expand_path("../autoloading_fixtures/load_path", __FILE__)
+    path = File.expand_path("autoloading_fixtures/load_path", __dir__)
     original_path = $:.dup
     $:.push(path)
 
@@ -332,7 +332,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_require_returns_true_when_file_not_yet_required
-    path = File.expand_path("../autoloading_fixtures/load_path", __FILE__)
+    path = File.expand_path("autoloading_fixtures/load_path", __dir__)
     original_path = $:.dup
     $:.push(path)
 
@@ -345,7 +345,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_require_returns_true_when_file_not_yet_required_even_when_no_new_constants_added
-    path = File.expand_path("../autoloading_fixtures/load_path", __FILE__)
+    path = File.expand_path("autoloading_fixtures/load_path", __dir__)
     original_path = $:.dup
     $:.push(path)
 
@@ -359,7 +359,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_require_returns_false_when_file_already_required
-    path = File.expand_path("../autoloading_fixtures/load_path", __FILE__)
+    path = File.expand_path("autoloading_fixtures/load_path", __dir__)
     original_path = $:.dup
     $:.push(path)
 
@@ -379,7 +379,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_load_returns_true_when_file_found
-    path = File.expand_path("../autoloading_fixtures/load_path", __FILE__)
+    path = File.expand_path("autoloading_fixtures/load_path", __dir__)
     original_path = $:.dup
     $:.push(path)
 
@@ -438,7 +438,7 @@ class DependenciesTest < ActiveSupport::TestCase
 
   def test_loadable_constants_for_path_should_handle_relative_paths
     fake_root = "dependencies"
-    relative_root = File.dirname(__FILE__) + "/dependencies"
+    relative_root = File.expand_path("dependencies", __dir__)
     ["", "/"].each do |suffix|
       with_loading fake_root + suffix do
         assert_equal ["A::B"], ActiveSupport::Dependencies.loadable_constants_for_path(relative_root + "/a/b")
@@ -463,7 +463,7 @@ class DependenciesTest < ActiveSupport::TestCase
   end
 
   def test_loadable_constants_with_load_path_without_trailing_slash
-    path = File.dirname(__FILE__) + "/autoloading_fixtures/class_folder/inline_class.rb"
+    path = File.expand_path("autoloading_fixtures/class_folder/inline_class.rb", __dir__)
     with_loading "autoloading_fixtures/class/" do
       assert_equal [], ActiveSupport::Dependencies.loadable_constants_for_path(path)
     end
@@ -991,7 +991,7 @@ class DependenciesTest < ActiveSupport::TestCase
   def test_remove_constant_does_not_trigger_loading_autoloads
     constant = "ShouldNotBeAutoloaded"
     Object.class_eval do
-      autoload constant, File.expand_path("../autoloading_fixtures/should_not_be_required", __FILE__)
+      autoload constant, File.expand_path("autoloading_fixtures/should_not_be_required", __dir__)
     end
 
     assert_nil ActiveSupport::Dependencies.remove_constant(constant), "Kernel#autoload has been triggered by remove_constant"
diff --git a/activesupport/test/dependencies_test_helpers.rb b/activesupport/test/dependencies_test_helpers.rb
index 9bc63ed89e..451195a143 100644
--- a/activesupport/test/dependencies_test_helpers.rb
+++ b/activesupport/test/dependencies_test_helpers.rb
@@ -1,7 +1,7 @@
 module DependenciesTestHelpers
   def with_loading(*from)
     old_mechanism, ActiveSupport::Dependencies.mechanism = ActiveSupport::Dependencies.mechanism, :load
-    this_dir = File.dirname(__FILE__)
+    this_dir = __dir__
     parent_dir = File.dirname(this_dir)
     path_copy = $LOAD_PATH.dup
     $LOAD_PATH.unshift(parent_dir) unless $LOAD_PATH.include?(parent_dir)
diff --git a/activesupport/test/inflector_test.rb b/activesupport/test/inflector_test.rb
index 14bc10513b..ef956eda90 100644
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -420,6 +420,8 @@ class InflectorTest < ActiveSupport::TestCase
       inflect.singular(/es$/, "")
 
       inflect.irregular("el", "los")
+
+      inflect.uncountable("agua")
     end
 
     assert_equal("hijos", "hijo".pluralize(:es))
@@ -432,12 +434,17 @@ class InflectorTest < ActiveSupport::TestCase
     assert_equal("los", "el".pluralize(:es))
     assert_equal("els", "el".pluralize)
 
+    assert_equal("agua", "agua".pluralize(:es))
+    assert_equal("aguas", "agua".pluralize)
+
     ActiveSupport::Inflector.inflections(:es) { |inflect| inflect.clear }
 
     assert ActiveSupport::Inflector.inflections(:es).plurals.empty?
     assert ActiveSupport::Inflector.inflections(:es).singulars.empty?
+    assert ActiveSupport::Inflector.inflections(:es).uncountables.empty?
     assert !ActiveSupport::Inflector.inflections.plurals.empty?
     assert !ActiveSupport::Inflector.inflections.singulars.empty?
+    assert !ActiveSupport::Inflector.inflections.uncountables.empty?
   end
 
   def test_clear_all
diff --git a/activesupport/test/message_encryptor_test.rb b/activesupport/test/message_encryptor_test.rb
index 56a436f751..4c3515b5e1 100644
--- a/activesupport/test/message_encryptor_test.rb
+++ b/activesupport/test/message_encryptor_test.rb
@@ -86,20 +86,32 @@ class MessageEncryptorTest < ActiveSupport::TestCase
     assert_equal @data, encryptor.decrypt_and_verify(message)
   end
 
+  def test_aead_mode_with_hmac_cbc_cipher_text
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+
+    assert_aead_not_decrypted(encryptor, "eHdGeExnZEwvMSt3U3dKaFl1WFo0TjVvYzA0eGpjbm5WSkt5MXlsNzhpZ0ZnbWhBWFlQZTRwaXE1bVJCS2oxMDZhYVp2dVN3V0lNZUlWQ3c2eVhQbnhnVjFmeVVubmhRKzF3WnZyWHVNMDg9LS1HSisyakJVSFlPb05ISzRMaXRzcFdBPT0=--831a1d54a3cda8a0658dc668a03dedcbce13b5ca")
+  end
+
   def test_messing_with_aead_values_causes_failures
     encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
     text, iv, auth_tag = encryptor.encrypt_and_sign(@data).split("--")
-    assert_not_decrypted([iv, text, auth_tag] * "--")
-    assert_not_decrypted([munge(text), iv, auth_tag] * "--")
-    assert_not_decrypted([text, munge(iv), auth_tag] * "--")
-    assert_not_decrypted([text, iv, munge(auth_tag)] * "--")
-    assert_not_decrypted([munge(text), munge(iv), munge(auth_tag)] * "--")
-    assert_not_decrypted([text, iv] * "--")
-    assert_not_decrypted([text, iv, auth_tag[0..-2]] * "--")
+    assert_aead_not_decrypted(encryptor, [iv, text, auth_tag] * "--")
+    assert_aead_not_decrypted(encryptor, [munge(text), iv, auth_tag] * "--")
+    assert_aead_not_decrypted(encryptor, [text, munge(iv), auth_tag] * "--")
+    assert_aead_not_decrypted(encryptor, [text, iv, munge(auth_tag)] * "--")
+    assert_aead_not_decrypted(encryptor, [munge(text), munge(iv), munge(auth_tag)] * "--")
+    assert_aead_not_decrypted(encryptor, [text, iv] * "--")
+    assert_aead_not_decrypted(encryptor, [text, iv, auth_tag[0..-2]] * "--")
   end
 
   private
 
+    def assert_aead_not_decrypted(encryptor, value)
+      assert_raise(ActiveSupport::MessageEncryptor::InvalidMessage) do
+        encryptor.decrypt_and_verify(value)
+      end
+    end
+
     def assert_not_decrypted(value)
       assert_raise(ActiveSupport::MessageEncryptor::InvalidMessage) do
         @encryptor.decrypt_and_verify(@verifier.generate(value))
diff --git a/activesupport/test/number_helper_test.rb b/activesupport/test/number_helper_test.rb
index dc0c34d4e2..4caf1428ea 100644
--- a/activesupport/test/number_helper_test.rb
+++ b/activesupport/test/number_helper_test.rb
@@ -321,12 +321,18 @@ module ActiveSupport
           gangster = { hundred: "hundred bucks", million: "thousand quids" }
           assert_equal "1 hundred bucks", number_helper.number_to_human(100, units: gangster)
           assert_equal "25 hundred bucks", number_helper.number_to_human(2500, units: gangster)
+          assert_equal "1000 hundred bucks", number_helper.number_to_human(100_000, units: gangster)
+          assert_equal "1 thousand quids", number_helper.number_to_human(999_999, units: gangster)
+          assert_equal "1 thousand quids", number_helper.number_to_human(1_000_000, units: gangster)
           assert_equal "25 thousand quids", number_helper.number_to_human(25000000, units: gangster)
           assert_equal "12300 thousand quids", number_helper.number_to_human(12345000000, units: gangster)
 
           #Spaces are stripped from the resulting string
           assert_equal "4", number_helper.number_to_human(4, units: { unit: "", ten: "tens " })
           assert_equal "4.5  tens", number_helper.number_to_human(45, units: { unit: "", ten: " tens   " })
+
+          #Uses only the provided units and does not try to use larger ones
+          assert_equal "1000 kilometers", number_helper.number_to_human(1_000_000, units: { unit: "meter", thousand: "kilometers" })
         end
       end
 
diff --git a/activesupport/test/rescuable_test.rb b/activesupport/test/rescuable_test.rb
index f7eb047d44..3bdd1651e7 100644
--- a/activesupport/test/rescuable_test.rb
+++ b/activesupport/test/rescuable_test.rb
@@ -43,7 +43,9 @@ class Stargate
   def dispatch(method)
     send(method)
   rescue Exception => e
-    rescue_with_handler(e)
+    unless rescue_with_handler(e)
+      @result = "unhandled"
+    end
   end
 
   def attack
@@ -58,6 +60,26 @@ class Stargate
     raise MadRonon.new("dex")
   end
 
+  def crash
+    raise "unhandled RuntimeError"
+  end
+
+  def looped_crash
+    ex1 = StandardError.new("error 1")
+    ex2 = StandardError.new("error 2")
+    begin
+      begin
+        raise ex1
+      rescue
+        # sets the cause on ex2 to be ex1
+        raise ex2
+      end
+    rescue
+      # sets the cause on ex1 to be ex2
+      raise ex1
+    end
+  end
+
   def fall_back_to_cause
     # This exception is the cause and has a handler.
     ronanize
@@ -139,4 +161,14 @@ class RescuableTest < ActiveSupport::TestCase
     @stargate.dispatch :fall_back_to_cause
     assert_equal "dex", @stargate.result
   end
+
+  def test_unhandled_exceptions
+    @stargate.dispatch(:crash)
+    assert_equal "unhandled", @stargate.result
+  end
+
+  def test_rescue_handles_loops_in_exception_cause_chain
+    @stargate.dispatch :looped_crash
+    assert_equal "unhandled", @stargate.result
+  end
 end
diff --git a/activesupport/test/test_case_test.rb b/activesupport/test/test_case_test.rb
index af7fc44d66..40dfbe2542 100644
--- a/activesupport/test/test_case_test.rb
+++ b/activesupport/test/test_case_test.rb
@@ -237,9 +237,6 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   end
 end
 
-class AlsoDoingNothingTest < ActiveSupport::TestCase
-end
-
 # Setup and teardown callbacks.
 class SetupAndTeardownTest < ActiveSupport::TestCase
   setup :reset_callback_record, :foo
diff --git a/activesupport/test/testing/file_fixtures_test.rb b/activesupport/test/testing/file_fixtures_test.rb
index e44fe58ce9..9f28252c31 100644
--- a/activesupport/test/testing/file_fixtures_test.rb
+++ b/activesupport/test/testing/file_fixtures_test.rb
@@ -3,12 +3,12 @@ require "abstract_unit"
 require "pathname"
 
 class FileFixturesTest < ActiveSupport::TestCase
-  self.file_fixture_path = File.expand_path("../../file_fixtures", __FILE__)
+  self.file_fixture_path = File.expand_path("../file_fixtures", __dir__)
 
   test "#file_fixture returns Pathname to file fixture" do
     path = file_fixture("sample.txt")
     assert_kind_of Pathname, path
-    assert_match %r{.*/test/file_fixtures/sample.txt$}, path.to_s
+    assert_match %r{.*/test/file_fixtures/sample\.txt$}, path.to_s
   end
 
   test "raises an exception when the fixture file does not exist" do
@@ -20,11 +20,11 @@ class FileFixturesTest < ActiveSupport::TestCase
 end
 
 class FileFixturesPathnameDirectoryTest < ActiveSupport::TestCase
-  self.file_fixture_path = Pathname.new(File.expand_path("../../file_fixtures", __FILE__))
+  self.file_fixture_path = Pathname.new(File.expand_path("../file_fixtures", __dir__))
 
   test "#file_fixture_path returns Pathname to file fixture" do
     path = file_fixture("sample.txt")
     assert_kind_of Pathname, path
-    assert_match %r{.*/test/file_fixtures/sample.txt$}, path.to_s
+    assert_match %r{.*/test/file_fixtures/sample\.txt$}, path.to_s
   end
 end
diff --git a/activesupport/test/time_travel_test.rb b/activesupport/test/time_travel_test.rb
index e0d3fb0cf5..9d354f14f4 100644
--- a/activesupport/test/time_travel_test.rb
+++ b/activesupport/test/time_travel_test.rb
@@ -99,7 +99,7 @@ class TimeTravelTest < ActiveSupport::TestCase
             #noop
           end
         end
-        assert_match(/Calling `travel_to` with a block, when we have previously already made a call to `travel_to`, can lead to confusing time stubbing./, e.message)
+        assert_match(/Calling `travel_to` with a block, when we have previously already made a call to `travel_to`, can lead to confusing time stubbing\./, e.message)
       end
     end
   end
diff --git a/activesupport/test/xml_mini/jdom_engine_test.rb b/activesupport/test/xml_mini/jdom_engine_test.rb
index e783cea67c..fc35ac113b 100644
--- a/activesupport/test/xml_mini/jdom_engine_test.rb
+++ b/activesupport/test/xml_mini/jdom_engine_test.rb
@@ -2,7 +2,7 @@ require_relative "xml_mini_engine_test"
 
 XMLMiniEngineTest.run_with_platform("java") do
   class JDOMEngineTest < XMLMiniEngineTest
-    FILES_DIR = File.dirname(__FILE__) + "/../fixtures/xml"
+    FILES_DIR = File.expand_path("../fixtures/xml", __dir__)
 
     def test_not_allowed_to_expand_entities_to_files
       attack_xml = <<-EOT
diff --git a/guides/bug_report_templates/action_controller_gem.rb b/guides/bug_report_templates/action_controller_gem.rb
index 46fabca3e8..8b7aa893fd 100644
--- a/guides/bug_report_templates/action_controller_gem.rb
+++ b/guides/bug_report_templates/action_controller_gem.rb
@@ -8,14 +8,14 @@ end
 gemfile(true) do
   source "https://rubygems.org"
   # Activate the gem you are reporting the issue against.
-  gem "rails", "5.1.0.rc1"
+  gem "rails", "5.1.0"
 end
 
 require "rack/test"
 require "action_controller/railtie"
 
 class TestApp < Rails::Application
-  config.root = File.dirname(__FILE__)
+  config.root = __dir__
   config.session_store :cookie_store, key: "cookie_store_key"
   secrets.secret_token    = "secret_token"
   secrets.secret_key_base = "secret_key_base"
diff --git a/guides/bug_report_templates/action_controller_master.rb b/guides/bug_report_templates/action_controller_master.rb
index 7644f6fe4a..3dd66c95ec 100644
--- a/guides/bug_report_templates/action_controller_master.rb
+++ b/guides/bug_report_templates/action_controller_master.rb
@@ -14,7 +14,7 @@ end
 require "action_controller/railtie"
 
 class TestApp < Rails::Application
-  config.root = File.dirname(__FILE__)
+  config.root = __dir__
   secrets.secret_token    = "secret_token"
   secrets.secret_key_base = "secret_key_base"
 
diff --git a/guides/bug_report_templates/active_job_gem.rb b/guides/bug_report_templates/active_job_gem.rb
index 71fe356ea0..252b270a0c 100644
--- a/guides/bug_report_templates/active_job_gem.rb
+++ b/guides/bug_report_templates/active_job_gem.rb
@@ -8,7 +8,7 @@ end
 gemfile(true) do
   source "https://rubygems.org"
   # Activate the gem you are reporting the issue against.
-  gem "activejob", "5.1.0.rc1"
+  gem "activejob", "5.1.0"
 end
 
 require "minitest/autorun"
diff --git a/guides/bug_report_templates/active_record_gem.rb b/guides/bug_report_templates/active_record_gem.rb
index a685c257ea..61d4e8d395 100644
--- a/guides/bug_report_templates/active_record_gem.rb
+++ b/guides/bug_report_templates/active_record_gem.rb
@@ -8,7 +8,7 @@ end
 gemfile(true) do
   source "https://rubygems.org"
   # Activate the gem you are reporting the issue against.
-  gem "activerecord", "5.1.0.rc1"
+  gem "activerecord", "5.1.0"
   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 b4e822dfe0..0c398e334a 100644
--- a/guides/bug_report_templates/active_record_migrations_gem.rb
+++ b/guides/bug_report_templates/active_record_migrations_gem.rb
@@ -8,7 +8,7 @@ end
 gemfile(true) do
   source "https://rubygems.org"
   # Activate the gem you are reporting the issue against.
-  gem "activerecord", "5.1.0.rc1"
+  gem "activerecord", "5.1.0"
   gem "sqlite3"
 end
 
diff --git a/guides/bug_report_templates/generic_gem.rb b/guides/bug_report_templates/generic_gem.rb
index e1b705bea4..4dcd04ea27 100644
--- a/guides/bug_report_templates/generic_gem.rb
+++ b/guides/bug_report_templates/generic_gem.rb
@@ -8,7 +8,7 @@ end
 gemfile(true) do
   source "https://rubygems.org"
   # Activate the gem you are reporting the issue against.
-  gem "activesupport", "5.1.0.rc1"
+  gem "activesupport", "5.1.0"
 end
 
 require "active_support/core_ext/object/blank"
diff --git a/guides/rails_guides/generator.rb b/guides/rails_guides/generator.rb
index 28164a3cb4..35f014747c 100644
--- a/guides/rails_guides/generator.rb
+++ b/guides/rails_guides/generator.rb
@@ -73,7 +73,7 @@ module RailsGuides
 
         @output_dir  = "#{@guides_dir}/output"
         @output_dir += "/kindle"       if @kindle
-        @source_dir += "/#{@language}" if @language
+        @output_dir += "/#{@language}" if @language
       end
 
       def create_output_dir_if_needed
diff --git a/guides/rails_guides/helpers.rb b/guides/rails_guides/helpers.rb
index 6f4b0b492c..520aa7f7cc 100644
--- a/guides/rails_guides/helpers.rb
+++ b/guides/rails_guides/helpers.rb
@@ -15,7 +15,7 @@ module RailsGuides
     end
 
     def documents_by_section
-      @documents_by_section ||= YAML.load_file(File.expand_path("../../source/#{@lang ? @lang + '/' : ''}documents.yaml", __FILE__))
+      @documents_by_section ||= YAML.load_file(File.expand_path("../source/#{@language ? @language + '/' : ''}documents.yaml", __dir__))
     end
 
     def documents_flat
diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb
index 9d43c10be6..7ac3d417a4 100644
--- a/guides/rails_guides/markdown/renderer.rb
+++ b/guides/rails_guides/markdown/renderer.rb
@@ -93,7 +93,7 @@ HTML
         def github_file_url(file_path)
           tree = version || edge
 
-          root = file_path[%r{(.+)/}, 1]
+          root = file_path[%r{(\w+)/}, 1]
           path = \
             case root
             when "abstract_controller", "action_controller", "action_dispatch"
diff --git a/guides/source/5_1_release_notes.md b/guides/source/5_1_release_notes.md
index 0f6167f1ee..fa92b9e5f8 100644
--- a/guides/source/5_1_release_notes.md
+++ b/guides/source/5_1_release_notes.md
@@ -87,7 +87,7 @@ screenshots.
 [Pull Request](https://github.com/rails/rails/pull/28038)
 
 Rails now allows management of application secrets in a secure way,
-building on top of the [sekrets](https://github.com/ahoward/sekrets) gem.
+inspired by the [sekrets](https://github.com/ahoward/sekrets) gem.
 
 Run `bin/rails secrets:setup` to setup a new encrypted secrets file. This will
 also generate a master key, which must be stored outside of the repository. The
@@ -328,9 +328,6 @@ Please refer to the [Changelog][action-cable] for detailed changes.
     with multiple applications.
     ([Pull Request](https://github.com/rails/rails/pull/27425))
 
-*   Permit same-origin connections by default.
-    ([commit](https://github.com/rails/rails/commit/dae404473409fcab0e07976aec626df670e52282))
-
 *   Add `ActiveSupport::Notifications` hook for broadcasting data.
     ([Pull Request](https://github.com/rails/rails/pull/24988))
 
@@ -341,7 +338,7 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 ### Removals
 
-*   Removed support to non-keyword arguments in `#process`, `#get`, `#post`,
+*   Removed support for non-keyword arguments in `#process`, `#get`, `#post`,
     `#patch`, `#put`, `#delete`, and `#head` for the `ActionDispatch::IntegrationTest`
     and `ActionController::TestCase` classes.
     ([Commit](https://github.com/rails/rails/commit/98b8309569a326910a723f521911e54994b112fb),
@@ -356,9 +353,6 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 ### Deprecations
 
-*   Deprecated `:controller` and `:action` path parameters.
-    ([Pull Request](https://github.com/rails/rails/pull/23980))
-
 *   Deprecated `config.action_controller.raise_on_unfiltered_parameters`.
     It doesn't have any effect in Rails 5.1.
     ([Commit](https://github.com/rails/rails/commit/c6640fb62b10db26004a998d2ece98baede509e5))
@@ -416,10 +410,6 @@ Please refer to the [Changelog][action-mailer] for detailed changes.
 
 ### Notable changes
 
-*   Exception handling: use `rescue_from` to handle exceptions raised by
-    mailer actions, by message delivery, and by deferred delivery jobs.
-    ([commit](https://github.com/rails/rails/commit/e35b98e6f5c54330245645f2ed40d56c74538902))
-
 *   Allowed setting custom content type when attachments are included
     and body is set inline.
     ([Pull Request](https://github.com/rails/rails/pull/27227))
@@ -442,8 +432,73 @@ Please refer to the [Changelog][active-record] for detailed changes.
 
 ### Removals
 
+*   Removed support for passing arguments and block at the same time to
+    `ActiveRecord::QueryMethods#select`.
+    ([Commit](https://github.com/rails/rails/commit/4fc3366d9d99a0eb19e45ad2bf38534efbf8c8ce))
+
+*   Removed deprecated `activerecord.errors.messages.restrict_dependent_destroy.one` and
+    `activerecord.errors.messages.restrict_dependent_destroy.many` i18n scopes.
+    ([Commit](https://github.com/rails/rails/commit/00e3973a311))
+
+*   Removed deprecated force reload argument in singular and collection association readers.
+    ([Commit](https://github.com/rails/rails/commit/09cac8c67af))
+
+*   Removed deprecated support for passing a column to `#quote`.
+    ([Commit](https://github.com/rails/rails/commit/e646bad5b7c))
+
+*   Removed deprecated `name` arguments from `#tables`.
+    ([Commit](https://github.com/rails/rails/commit/d5be101dd02214468a27b6839ffe338cfe8ef5f3))
+
+*   Removed deprecated behavior of `#tables` and `#table_exists?` to return tables and views
+    to return only tables and not views.
+    ([Commit](https://github.com/rails/rails/commit/5973a984c369a63720c2ac18b71012b8347479a8))
+
+*   Removed deprecated `original_exception` argument in `ActiveRecord::StatementInvalid#initialize`
+    and `ActiveRecord::StatementInvalid#original_exception`.
+    ([Commit](https://github.com/rails/rails/commit/bc6c5df4699d3f6b4a61dd12328f9e0f1bd6cf46))
+
+*   Removed deprecated support of passing a class as a value in a query.
+    ([Commit](https://github.com/rails/rails/commit/b4664864c972463c7437ad983832d2582186e886))
+
+*   Removed deprecated support to query using commas on LIMIT.
+    ([Commit](https://github.com/rails/rails/commit/fc3e67964753fb5166ccbd2030d7382e1976f393))
+
+*   Removed deprecated `conditions` parameter from `#destroy_all`.
+    ([Commit](https://github.com/rails/rails/commit/d31a6d1384cd740c8518d0bf695b550d2a3a4e9b))
+
+*   Removed deprecated `conditions` parameter from `#delete_all`.
+    ([Commit](https://github.com/rails/rails/pull/27503/commits/e7381d289e4f8751dcec9553dcb4d32153bd922b))
+
+*   Removed deprecated method `#load_schema_for` in favor of `#load_schema`.
+    ([Commit](https://github.com/rails/rails/commit/419e06b56c3b0229f0c72d3e4cdf59d34d8e5545))
+
+*   Removed deprecated `#raise_in_transactional_callbacks` configuration.
+    ([Commit](https://github.com/rails/rails/commit/8029f779b8a1dd9848fee0b7967c2e0849bf6e07))
+
+*   Removed deprecated `#use_transactional_fixtures` configuration.
+    ([Commit](https://github.com/rails/rails/commit/3955218dc163f61c932ee80af525e7cd440514b3))
+
 ### Deprecations
 
+*   Deprecated `error_on_ignored_order_or_limit` flag in favor of
+    `error_on_ignored_order`.
+    ([Commit](https://github.com/rails/rails/commit/451437c6f57e66cc7586ec966e530493927098c7))
+
+*   Deprecated `sanitize_conditions` in favor of `sanitize_sql`.
+    ([Pull Request](https://github.com/rails/rails/pull/25999))
+
+*   Deprecated `supports_migrations?` on connection adapters.
+    ([Pull Request](https://github.com/rails/rails/pull/28172))
+
+*   Deprecated `Migrator.schema_migrations_table_name`, use `SchemaMigration.table_name` instead.
+    ([Pull Request](https://github.com/rails/rails/pull/28351))
+
+*   Deprecated using `#quoted_id` in quoting and type casting.
+    ([Pull Request](https://github.com/rails/rails/pull/27962))
+
+*   Deprecated passing `default` argument to `#index_name_exists?`.
+    ([Pull Request](https://github.com/rails/rails/pull/26930))
+
 ### Notable changes
 
 *   Change Default Primary Keys to BIGINT.
@@ -473,6 +528,13 @@ Please refer to the [Changelog][active-record] for detailed changes.
 *   Add `ActiveRecord::Base.connection_pool.stat`.
     ([Pull Request](https://github.com/rails/rails/pull/26988))
 
+*   Inheriting directly from `ActiveRecord::Migration` raises an error.
+    Specify the Rails version for which the migration was written for.
+    ([Commit](https://github.com/rails/rails/commit/249f71a22ab21c03915da5606a063d321f04d4d3))
+
+*   An error is raised when `through` association has ambiguous reflection name.
+    ([Commit](https://github.com/rails/rails/commit/0944182ad7ed70d99b078b22426cbf844edd3f61))
+
 Active Model
 ------------
 
@@ -537,9 +599,9 @@ Please refer to the [Changelog][active-support] for detailed changes.
 
 *   The top level `HashWithIndifferentAccess` class has been softly deprecated
     in favor of the `ActiveSupport::HashWithIndifferentAccess` one.
-    ([Pull request](https://github.com/rails/rails/pull/28157))
+    ([Pull Request](https://github.com/rails/rails/pull/28157))
 
-*   Deprecate passing string to `:if` and `:unless` conditional options on `set_callback` and `skip_callback`.
+*   Deprecated passing string to `:if` and `:unless` conditional options on `set_callback` and `skip_callback`.
     ([Commit](https://github.com/rails/rails/commit/0952552)
 
 ### Notable changes
diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index 5d987264f5..22537f960c 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -715,6 +715,9 @@ end
 
 Now, the `LoginsController`'s `new` and `create` actions will work as before without requiring the user to be logged in. The `:only` option is used to skip this filter only for these actions, and there is also an `:except` option which works the other way. These options can be used when adding filters too, so you can add a filter which only runs for selected actions in the first place.
 
+NOTE: Calling the same filter multiple times with different options will not work,
+since the last filter definition will overwrite the previous ones.
+
 ### After Filters and Around Filters
 
 In addition to "before" filters, you can also run filters after an action has been executed, or both before and after.
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index 65146ee7da..7751ac00df 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -781,7 +781,8 @@ config.action_mailer.smtp_settings = {
   enable_starttls_auto: true  }
 ```
 Note: As of July 15, 2014, Google increased [its security measures](https://support.google.com/accounts/answer/6010255) and now blocks attempts from apps it deems less secure.
-You can change your gmail settings [here](https://www.google.com/settings/security/lesssecureapps) to allow the attempts or
+You can change your Gmail settings [here](https://www.google.com/settings/security/lesssecureapps) to allow the attempts. If your Gmail account has 2-factor authentication enabled,
+then you will need to set an [app password](https://myaccount.google.com/apppasswords) and use that instead of your regular password. Alternatively, you can
 use another ESP to send email by replacing 'smtp.gmail.com' above with the address of your provider.
 
 Mailer Testing
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index c835adeab6..10412128cc 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -419,7 +419,7 @@ image_tag("rails.png") # => <img src="http://assets.example.com/images/rails.png
 
 #### auto_discovery_link_tag
 
-Returns a link tag that browsers and feed readers can use to auto-detect an RSS or Atom feed.
+Returns a link tag that browsers and feed readers can use to auto-detect an RSS, Atom, or JSON feed.
 
 ```ruby
 auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", { title: "RSS Feed" }) # =>
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index b58ca61848..443be77934 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -310,6 +310,12 @@ UserMailer.welcome(@user).deliver_now
 UserMailer.welcome(@user).deliver_later
 ```
 
+NOTE: Using the asynchronous queue from a Rake task (for example, to
+send an email using `.deliver_later`) will generally not work because Rake will
+likely end, causing the in-process thread pool to be deleted, before any/all
+of the `.deliver_later` emails are processed. To avoid this problem, use
+`.deliver_now` or run a persistent queue in development.
+
 
 Internationalization
 --------------------
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 26d01d4ede..aea7515974 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -118,7 +118,7 @@ You can also use this method to query for multiple objects. Call the `find` meth
 
 ```ruby
 # Find the clients with primary keys 1 and 10.
-client = Client.find([1, 10]) # Or even Client.find(1, 10)
+clients = Client.find([1, 10]) # Or even Client.find(1, 10)
 # => [#<Client id: 1, first_name: "Lifo">, #<Client id: 10, first_name: "Ryan">]
 ```
 
@@ -150,7 +150,7 @@ The `take` method returns `nil` if no record is found and no exception will be r
 You can pass in a numerical argument to the `take` method to return up to that number of results. For example
 
 ```ruby
-client = Client.take(2)
+clients = Client.take(2)
 # => [
 #   #<Client id: 1, first_name: "Lifo">,
 #   #<Client id: 220, first_name: "Sara">
@@ -189,7 +189,7 @@ If your [default scope](active_record_querying.html#applying-a-default-scope) co
 You can pass in a numerical argument to the `first` method to return up to that number of results. For example
 
 ```ruby
-client = Client.first(3)
+clients = Client.first(3)
 # => [
 #   #<Client id: 1, first_name: "Lifo">,
 #   #<Client id: 2, first_name: "Fifo">,
@@ -240,7 +240,7 @@ If your [default scope](active_record_querying.html#applying-a-default-scope) co
 You can pass in a numerical argument to the `last` method to return up to that number of results. For example
 
 ```ruby
-client = Client.last(3)
+clients = Client.last(3)
 # => [
 #   #<Client id: 219, first_name: "James">,
 #   #<Client id: 220, first_name: "Sara">,
@@ -557,6 +557,19 @@ In other words, this query can be generated by calling `where` with no argument,
 SELECT * FROM clients WHERE (clients.locked != 1)
 ```
 
+### OR Conditions
+
+`OR` condition between two relations can be build by calling `or` on the first relation
+and passing the second one as an argument.
+
+```ruby
+Client.where(locked: true).or(Client.where(orders_count: [1,3,5]))
+```
+
+```sql
+SELECT * FROM clients WHERE (clients.locked = 1 OR clients.orders_count IN (1,3,5))
+```
+
 Ordering
 --------
 
diff --git a/guides/source/api_app.md b/guides/source/api_app.md
index f373d313cc..64200ec242 100644
--- a/guides/source/api_app.md
+++ b/guides/source/api_app.md
@@ -206,16 +206,17 @@ An API application comes with the following middleware by default:
 - `ActiveSupport::Cache::Strategy::LocalCache::Middleware`
 - `Rack::Runtime`
 - `ActionDispatch::RequestId`
+- `ActionDispatch::RemoteIp`
 - `Rails::Rack::Logger`
 - `ActionDispatch::ShowExceptions`
 - `ActionDispatch::DebugExceptions`
-- `ActionDispatch::RemoteIp`
 - `ActionDispatch::Reloader`
 - `ActionDispatch::Callbacks`
 - `ActiveRecord::Migration::CheckPending`
 - `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.
@@ -360,7 +361,7 @@ middleware set, you can remove it with:
 config.middleware.delete ::Rack::Sendfile
 ```
 
-Keep in mind that removing these middleware will remove support for certain
+Keep in mind that removing these middlewares will remove support for certain
 features in Action Controller.
 
 Choosing Controller Modules
@@ -385,8 +386,9 @@ controller modules by default:
   hooks defined by Action Controller (see [the instrumentation
   guide](active_support_instrumentation.html#action-controller) for
 more information regarding this).
-- `ActionController::ParamsWrapper`: Wraps the parameters hash into a nested hash, 
+- `ActionController::ParamsWrapper`: Wraps the parameters hash into a nested hash,
   so that you don't have to specify root elements sending POST requests for instance.
+- `ActionController::Head`: Support for returning a response with no content, only headers
 
 Other plugins may add additional modules. You can get a list of all modules
 included into `ActionController::API` in the rails console:
@@ -394,12 +396,12 @@ included into `ActionController::API` in the rails console:
 ```bash
 $ bin/rails c
 >> ActionController::API.ancestors - ActionController::Metal.ancestors
-=> [ActionController::API, 
-    ActiveRecord::Railties::ControllerRuntime, 
-    ActionDispatch::Routing::RouteSet::MountedHelpers, 
-    ActionController::ParamsWrapper, 
-    ... , 
-    AbstractController::Rendering, 
+=> [ActionController::API,
+    ActiveRecord::Railties::ControllerRuntime,
+    ActionDispatch::Routing::RouteSet::MountedHelpers,
+    ActionController::ParamsWrapper,
+    ... ,
+    AbstractController::Rendering,
     ActionView::ViewPaths]
 ```
 
diff --git a/guides/source/api_documentation_guidelines.md b/guides/source/api_documentation_guidelines.md
index 3c61754982..c3c7367304 100644
--- a/guides/source/api_documentation_guidelines.md
+++ b/guides/source/api_documentation_guidelines.md
@@ -281,7 +281,7 @@ Methods created with `(module|class)_eval(STRING)` have a comment by their side
 
 ```ruby
 for severity in Severity.constants
-  class_eval <<-EOT, __FILE__, __LINE__
+  class_eval <<-EOT, __FILE__, __LINE__ + 1
     def #{severity.downcase}(message = nil, progname = nil, &block)  # def debug(message = nil, progname = nil, &block)
       add(#{severity}, message, progname, &block)                    #   add(DEBUG, message, progname, &block)
     end                                                              # end
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 5794bfa666..5c7d1f5365 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -599,7 +599,7 @@ class CreateBooks < ActiveRecord::Migration[5.0]
       t.string   :book_number
       t.integer  :author_id
     end
-    
+
     add_index :books, :author_id
     add_foreign_key :books, :authors
   end
@@ -1417,7 +1417,7 @@ If either of these saves fails due to validation errors, then the assignment sta
 
 If the parent object (the one declaring the `has_one` association) is unsaved (that is, `new_record?` returns `true`) then the child objects are not saved. They will automatically when the parent object is saved.
 
-If you want to assign an object to a `has_one` association without saving the object, use the `association.build` method.
+If you want to assign an object to a `has_one` association without saving the object, use the `build_association` method.
 
 ### `has_many` Association Reference
 
@@ -1559,7 +1559,7 @@ The `collection.size` method returns the number of objects in the collection.
 The `collection.find` method finds objects within the collection. It uses the same syntax and options as `ActiveRecord::Base.find`.
 
 ```ruby
-@available_books = @author.books.find(1)
+@available_book = @author.books.find(1)
 ```
 
 ##### `collection.where(...)`
diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md
index 61657023e7..05743ee4ce 100644
--- a/guides/source/autoloading_and_reloading_constants.md
+++ b/guides/source/autoloading_and_reloading_constants.md
@@ -983,20 +983,19 @@ WHERE "polygons"."type" IN ("Rectangle")
 That is not a bug, the query includes all *known* descendants of `Rectangle`.
 
 A way to ensure this works correctly regardless of the order of execution is to
-load the leaves of the tree by hand at the bottom of the file that defines the
-root class:
+manually load the direct subclasses at the bottom of the file that defines each
+intermediate class:
 
 ```ruby
-# app/models/polygon.rb
-class Polygon < ApplicationRecord
+# app/models/rectangle.rb
+class Rectangle < Polygon
 end
-require_dependency ‘square’
+require_dependency 'square'
 ```
 
-Only the leaves that are **at least grandchildren** need to be loaded this
-way. Direct subclasses do not need to be preloaded. If the hierarchy is
-deeper, intermediate classes will be autoloaded recursively from the bottom
-because their constant will appear in the class definitions as superclass.
+This needs to happen for every intermediate (non-root and non-leaf) class. The
+root class does not scope the query by type, and therefore does not necessarily
+have to know all its descendants.
 
 ### Autoloading and `require`
 
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index bf9456a482..1234e1f192 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -456,10 +456,14 @@ to `'http authentication'`.
 Defaults to `'signed cookie'`.
 
 * `config.action_dispatch.encrypted_cookie_salt` sets the encrypted cookies salt
-value. Defaults to `'encrypted cookie'`.
+  value. Defaults to `'encrypted cookie'`.
 
 * `config.action_dispatch.encrypted_signed_cookie_salt` sets the signed
-encrypted cookies salt value. Defaults to `'signed encrypted cookie'`.
+  encrypted cookies salt value. Defaults to `'signed encrypted cookie'`.
+
+* `config.action_dispatch.authenticated_encrypted_cookie_salt` sets the
+  authenticated encrypted cookie salt. Defaults to `'authenticated encrypted
+  cookie'`.
 
 * `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)
@@ -493,8 +497,6 @@ encrypted cookies salt value. Defaults to `'signed encrypted cookie'`.
 
 * `ActionDispatch::Callbacks.before` takes a block of code to run before the request.
 
-* `ActionDispatch::Callbacks.to_prepare` takes a block to run after `ActionDispatch::Callbacks.before`, but before the request. Runs for every request in `development` mode, but only once for `production` or environments with `cache_classes` set to `true`.
-
 * `ActionDispatch::Callbacks.after` takes a block of code to run after the request.
 
 ### Configuring Action View
@@ -1188,7 +1190,7 @@ Below is a comprehensive list of all the initializers found in Rails in the orde
 
 * `finisher_hook`: Provides a hook for after the initialization of process of the application is complete, as well as running all the `config.after_initialize` blocks for the application, railties and engines.
 
-* `set_routes_reloader_hook`: Configures Action Dispatch to reload the routes file using `ActionDispatch::Callbacks.to_prepare`.
+* `set_routes_reloader_hook`: Configures Action Dispatch to reload the routes file using `ActiveSupport::Callbacks.to_run`.
 
 * `disable_dependency_loading`: Disables the automatic dependency loading if the `config.eager_load` is set to `true`.
 
diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md
index 39f4272b3c..2f2962a3e6 100644
--- a/guides/source/contributing_to_ruby_on_rails.md
+++ b/guides/source/contributing_to_ruby_on_rails.md
@@ -141,14 +141,15 @@ NOTE: To help our CI servers you should add [ci skip] to your documentation comm
 Translating Rails Guides
 ------------------------
 
-We are happy to have people volunteer to translate the Rails guides into their own language.
-If you want to translate the Rails guides in your own language, follows these steps:
+We are happy to have people volunteer to translate the Rails guides. Just follow these steps:
 
-* Fork the project (rails/rails).
+* Fork https://github.com/rails/rails.
 * Add a source folder for your own language, for example: *guides/source/it-IT* for Italian.
 * Copy the contents of *guides/source* into your own language directory and translate them.
 * Do NOT translate the HTML files, as they are automatically generated.
 
+Note that translations are not submitted to the Rails repository. As detailed above, your work happens in a fork. This is so because in practice documentation maintenance via patches is only sustainable in English.
+
 To generate the guides in HTML format cd into the *guides* directory then run (eg. for it-IT):
 
 ```bash
diff --git a/guides/source/documents.yaml b/guides/source/documents.yaml
index 5fccdcccec..2afef57fc2 100644
--- a/guides/source/documents.yaml
+++ b/guides/source/documents.yaml
@@ -197,7 +197,6 @@
       name: Ruby on Rails 5.1 Release Notes
       url: 5_1_release_notes.html
       description: Release notes for Rails 5.1.
-      work_in_progress: true
     -
       name: Ruby on Rails 5.0 Release Notes
       url: 5_0_release_notes.html
diff --git a/guides/source/generators.md b/guides/source/generators.md
index a554e08204..d4ed2355d4 100644
--- a/guides/source/generators.md
+++ b/guides/source/generators.md
@@ -96,7 +96,7 @@ This is the generator just created:
 
 ```ruby
 class InitializerGenerator < Rails::Generators::NamedBase
-  source_root File.expand_path("../templates", __FILE__)
+  source_root File.expand_path("templates", __dir__)
 end
 ```
 
@@ -122,7 +122,7 @@ And now let's change the generator to copy this template when invoked:
 
 ```ruby
 class InitializerGenerator < Rails::Generators::NamedBase
-  source_root File.expand_path("../templates", __FILE__)
+  source_root File.expand_path("templates", __dir__)
 
   def copy_initializer_file
     copy_file "initializer.rb", "config/initializers/#{file_name}.rb"
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index f3ae5a5b28..5553f08456 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -20,16 +20,7 @@ Guide Assumptions
 
 This guide is designed for beginners who want to get started with a Rails
 application from scratch. It does not assume that you have any prior experience
-with Rails. However, to get the most out of it, you need to have some
-prerequisites installed:
-
-* The [Ruby](https://www.ruby-lang.org/en/downloads) language version 2.2.2 or newer.
-* Right version of [Development Kit](http://rubyinstaller.org/downloads/), if you
-  are using Windows.
-* The [RubyGems](https://rubygems.org) packaging system, which is installed with
-  Ruby by default. To learn more about RubyGems, please read the
-  [RubyGems Guides](http://guides.rubygems.org).
-* A working installation of the [SQLite3 Database](https://www.sqlite.org).
+with Rails.
 
 Rails is a web application framework running on the Ruby programming language.
 If you have no prior experience with Ruby, you will find a very steep learning
@@ -86,6 +77,9 @@ your prompt will look something like `c:\source_code>`
 
 ### Installing Rails
 
+Before you install Rails, you should check to make sure that your system has the
+proper prerequisites installed. These include Ruby and SQLite3.
+
 Open up a command line prompt. On macOS open Terminal.app, on Windows choose
 "Run" from your Start menu and type 'cmd.exe'. Any commands prefaced with a
 dollar sign `$` should be run in the command line. Verify that you have a
@@ -96,12 +90,19 @@ $ ruby -v
 ruby 2.3.1p112
 ```
 
+Rails requires Ruby version 2.2.2 or later. If the version number returned is
+less than that number, you'll need to install a fresh copy of Ruby.
+
 TIP: A number of tools exist to help you quickly install Ruby and Ruby
 on Rails on your system. Windows users can use [Rails Installer](http://railsinstaller.org),
 while macOS users can use [Tokaido](https://github.com/tokaido/tokaidoapp).
 For more installation methods for most Operating Systems take a look at
 [ruby-lang.org](https://www.ruby-lang.org/en/documentation/installation/).
 
+If you are working on Windows, you should also install the
+[Ruby Installer Development Kit](http://rubyinstaller.org/downloads/).
+
+You will also need an installation of the SQLite3 database.
 Many popular UNIX-like OSes ship with an acceptable version of SQLite3.
 On Windows, if you installed Rails through Rails Installer, you
 already have SQLite installed. Others can find installation instructions
@@ -127,7 +128,7 @@ run the following:
 $ rails --version
 ```
 
-If it says something like "Rails 5.1.0", you are ready to continue.
+If it says something like "Rails 5.1.1", you are ready to continue.
 
 ### Creating the Blog Application
 
@@ -1195,7 +1196,7 @@ it look as follows:
 This time we point the form to the `update` action, which is not defined yet
 but will be very soon.
 
-Passing the article object to the method, will automagically create url for submitting the edited article form. 
+Passing the article object to the method, will automagically create url for submitting the edited article form.
 This option tells Rails that we want this form to be submitted
 via the `PATCH` HTTP method which is the HTTP method you're expected to use to
 **update** resources according to the REST protocol.
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 48bb3147f3..caa3d21d23 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -768,7 +768,7 @@ WARNING: The asset tag helpers do _not_ verify the existence of the assets at th
 
 #### Linking to Feeds with the `auto_discovery_link_tag`
 
-The `auto_discovery_link_tag` helper builds HTML that most browsers and feed readers can use to detect the presence of RSS or Atom feeds. It takes the type of the link (`:rss` or `:atom`), a hash of options that are passed through to url_for, and a hash of options for the tag:
+The `auto_discovery_link_tag` helper builds HTML that most browsers and feed readers can use to detect the presence of RSS, Atom, or JSON feeds. It takes the type of the link (`:rss`, `:atom`, or `:json`), a hash of options that are passed through to url_for, and a hash of options for the tag:
 
 ```erb
 <%= auto_discovery_link_tag(:rss, {action: "feed"},
diff --git a/guides/source/nested_model_forms.md b/guides/source/nested_model_forms.md
deleted file mode 100644
index 71efa4b0d0..0000000000
--- a/guides/source/nested_model_forms.md
+++ /dev/null
@@ -1,230 +0,0 @@
-**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
-
-Rails Nested Model Forms
-========================
-
-Creating a form for a model _and_ its associations can become quite tedious. Therefore Rails provides helpers to assist in dealing with the complexities of generating these forms _and_ the required CRUD operations to create, update, and destroy associations.
-
-After reading this guide, you will know:
-
-* do stuff.
-
---------------------------------------------------------------------------------
-
-NOTE: This guide assumes the user knows how to use the [Rails form helpers](form_helpers.html) in general. Also, it's **not** an API reference. For a complete reference please visit [the Rails API documentation](http://api.rubyonrails.org/).
-
-
-Model setup
------------
-
-To be able to use the nested model functionality in your forms, the model will need to support some basic operations.
-
-First of all, it needs to define a writer method for the attribute that corresponds to the association you are building a nested model form for. The `fields_for` form helper will look for this method to decide whether or not a nested model form should be built.
-
-If the associated object is an array, a form builder will be yielded for each object, else only a single form builder will be yielded.
-
-Consider a Person model with an associated Address. When asked to yield a nested FormBuilder for the `:address` attribute, the `fields_for` form helper will look for a method on the Person instance named `address_attributes=`.
-
-### ActiveRecord::Base model
-
-For an ActiveRecord::Base model and association this writer method is commonly defined with the `accepts_nested_attributes_for` class method:
-
-#### has_one
-
-```ruby
-class Person < ApplicationRecord
-  has_one :address
-  accepts_nested_attributes_for :address
-end
-```
-
-#### belongs_to
-
-```ruby
-class Person < ApplicationRecord
-  belongs_to :firm
-  accepts_nested_attributes_for :firm
-end
-```
-
-#### has_many / has_and_belongs_to_many
-
-```ruby
-class Person < ApplicationRecord
-  has_many :projects
-  accepts_nested_attributes_for :projects
-end
-```
-
-NOTE: For greater detail on associations see [Active Record Associations](association_basics.html).
-For a complete reference on associations please visit the API documentation for [ActiveRecord::Associations::ClassMethods](http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html).
-
-### Custom model
-
-As you might have inflected from this explanation, you _don't_ necessarily need an ActiveRecord::Base model to use this functionality. The following examples are sufficient to enable the nested model form behavior:
-
-#### Single associated object
-
-```ruby
-class Person
-  def address
-    Address.new
-  end
-
-  def address_attributes=(attributes)
-    # ...
-  end
-end
-```
-
-#### Association collection
-
-```ruby
-class Person
-  def projects
-    [Project.new, Project.new]
-  end
-
-  def projects_attributes=(attributes)
-    # ...
-  end
-end
-```
-
-NOTE: See (TODO) in the advanced section for more information on how to deal with the CRUD operations in your custom model.
-
-Views
------
-
-### Controller code
-
-A nested model form will _only_ be built if the associated object(s) exist. This means that for a new model instance you would probably want to build the associated object(s) first.
-
-Consider the following typical RESTful controller which will prepare a new Person instance and its `address` and `projects` associations before rendering the `new` template:
-
-```ruby
-class PeopleController < ApplicationController
-  def new
-    @person = Person.new
-    @person.build_address
-    2.times { @person.projects.build }
-  end
-
-  def create
-    @person = Person.new(params[:person])
-    if @person.save
-      # ...
-    end
-  end
-end
-```
-
-NOTE: Obviously the instantiation of the associated object(s) can become tedious and not DRY, so you might want to move that into the model itself. ActiveRecord::Base provides an `after_initialize` callback which is a good way to refactor this.
-
-### Form code
-
-Now that you have a model instance, with the appropriate methods and associated object(s), you can start building the nested model form.
-
-#### Standard form
-
-Start out with a regular RESTful form:
-
-```erb
-<%= form_for @person do |f| %>
-  <%= f.text_field :name %>
-<% end %>
-```
-
-This will generate the following html:
-
-```html
-<form action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-</form>
-```
-
-#### Nested form for a single associated object
-
-Now add a nested form for the `address` association:
-
-```erb
-<%= form_for @person do |f| %>
-  <%= f.text_field :name %>
-
-  <%= f.fields_for :address do |af| %>
-    <%= af.text_field :street %>
-  <% end %>
-<% end %>
-```
-
-This generates:
-
-```html
-<form action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-
-  <input id="person_address_attributes_street" name="person[address_attributes][street]" type="text" />
-</form>
-```
-
-Notice that `fields_for` recognized the `address` as an association for which a nested model form should be built by the way it has namespaced the `name` attribute.
-
-When this form is posted the Rails parameter parser will construct a hash like the following:
-
-```ruby
-{
-  "person" => {
-    "name" => "Eloy Duran",
-    "address_attributes" => {
-      "street" => "Nieuwe Prinsengracht"
-    }
-  }
-}
-```
-
-That's it. The controller will simply pass this hash on to the model from the `create` action. The model will then handle building the `address` association for you and automatically save it when the parent (`person`) is saved.
-
-#### Nested form for a collection of associated objects
-
-The form code for an association collection is pretty similar to that of a single associated object:
-
-```erb
-<%= form_for @person do |f| %>
-  <%= f.text_field :name %>
-
-  <%= f.fields_for :projects do |pf| %>
-    <%= pf.text_field :name %>
-  <% end %>
-<% end %>
-```
-
-Which generates:
-
-```html
-<form action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-
-  <input id="person_projects_attributes_0_name" name="person[projects_attributes][0][name]" type="text" />
-  <input id="person_projects_attributes_1_name" name="person[projects_attributes][1][name]" type="text" />
-</form>
-```
-
-As you can see it has generated 2 `project name` inputs, one for each new `project` that was built in the controller's `new` action. Only this time the `name` attribute of the input contains a digit as an extra namespace. This will be parsed by the Rails parameter parser as:
-
-```ruby
-{
-  "person" => {
-    "name" => "Eloy Duran",
-    "projects_attributes" => {
-      "0" => { "name" => "Project 1" },
-      "1" => { "name" => "Project 2" }
-    }
-  }
-}
-```
-
-You can basically see the `projects_attributes` hash as an array of attribute hashes, one for each model instance.
-
-NOTE: The reason that `fields_for` constructed a hash instead of an array is that it won't work for any form nested deeper than one level deep.
-
-TIP: You _can_ however pass an array to the writer method generated by `accepts_nested_attributes_for` if you're using plain Ruby or some other API access. See (TODO) for more info and example.
diff --git a/guides/source/profiling.md b/guides/source/profiling.md
deleted file mode 100644
index ce093f78ba..0000000000
--- a/guides/source/profiling.md
+++ /dev/null
@@ -1,16 +0,0 @@
-*DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
-
-A Guide to Profiling Rails Applications
-=======================================
-
-This guide covers built-in mechanisms in Rails for profiling your application.
-
-After reading this guide, you will know:
-
-* Rails profiling terminology.
-* How to write benchmark tests for your application.
-* Other benchmarking approaches and plugins.
-
---------------------------------------------------------------------------------
-
-
diff --git a/guides/source/rails_application_templates.md b/guides/source/rails_application_templates.md
index 3e99ee7021..e087834a2f 100644
--- a/guides/source/rails_application_templates.md
+++ b/guides/source/rails_application_templates.md
@@ -277,6 +277,6 @@ relative paths to your template's location.
 
 ```ruby
 def source_paths
-  [File.expand_path(File.dirname(__FILE__))]
+  [__dir__]
 end
 ```
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index f25b185fb5..cef8450ee4 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -110,11 +110,12 @@ use ActiveSupport::Cache::Strategy::LocalCache::Middleware
 use Rack::Runtime
 use Rack::MethodOverride
 use ActionDispatch::RequestId
+use ActionDispatch::RemoteIp
+use Sprockets::Rails::QuietAssets
 use Rails::Rack::Logger
 use ActionDispatch::ShowExceptions
 use WebConsole::Middleware
 use ActionDispatch::DebugExceptions
-use ActionDispatch::RemoteIp
 use ActionDispatch::Reloader
 use ActionDispatch::Callbacks
 use ActiveRecord::Migration::CheckPending
@@ -124,7 +125,7 @@ use ActionDispatch::Flash
 use Rack::Head
 use Rack::ConditionalGet
 use Rack::ETag
-run Rails.application.routes
+run MyApp.application.routes
 ```
 
 The default middlewares shown here (and some others) are each summarized in the [Internal Middlewares](#internal-middleware-stack) section, below.
@@ -238,6 +239,14 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 * Makes a unique `X-Request-Id` header available to the response and enables the `ActionDispatch::Request#request_id` method.
 
+**`ActionDispatch::RemoteIp`**
+
+* Checks for IP spoofing attacks.
+
+**`Sprockets::Rails::QuietAssets`**
+
+* Suppresses logger output for asset requests.
+
 **`Rails::Rack::Logger`**
 
 * Notifies the logs that the request has began. After request is complete, flushes all the logs.
@@ -250,10 +259,6 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 * Responsible for logging exceptions and showing a debugging page in case the request is local.
 
-**`ActionDispatch::RemoteIp`**
-
-* Checks for IP spoofing attacks.
-
 **`ActionDispatch::Reloader`**
 
 * Provides prepare and cleanup callbacks, intended to assist with code reloading during development.
diff --git a/guides/source/security.md b/guides/source/security.md
index c305350243..f69a0c72b0 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -95,16 +95,23 @@ Rails 2 introduced a new default session storage, CookieStore. CookieStore saves
 
 * 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.
 
-However, since Rails 4, the default store is EncryptedCookieStore. With
-EncryptedCookieStore the session is encrypted before being stored in a cookie.
-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
-done using a server-side secret key `secrets.secret_key_base` stored in
-`config/secrets.yml`.
+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 `secrets.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.
 
-That means the security of this storage depends on this secret (and on the digest algorithm, which defaults to SHA1, for compatibility). So _don't use a trivial secret, i.e. a word from a dictionary, or one which is shorter than 30 characters, use `rails secret` instead_.
+Rails 5.2 uses AES-GCM for the encryption which couples authentication
+and encryption in one faster step and produces shorter ciphertexts.
 
-`secrets.secret_key_base` is used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get `secrets.secret_key_base` initialized to a random key present in `config/secrets.yml`, e.g.:
+Encrypted cookies are automatically upgraded if the
+`config.action_dispatch.use_authenticated_cookie_encryption` is enabled.
+
+_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!_
+
+Applications get `secrets.secret_key_base` initialized to a random key present in `config/secrets.yml`, e.g.:
 
     development:
       secret_key_base: a75d...
@@ -356,7 +363,7 @@ send_file('/var/www/uploads/' + params[:filename])
 Simply pass a file name like "../../../etc/passwd" to download the server's login information. A simple solution against this, is to _check that the requested file is in the expected directory_:
 
 ```ruby
-basename = File.expand_path(File.join(File.dirname(__FILE__), '../../files'))
+basename = File.expand_path('../../files', __dir__)
 filename = File.expand_path(File.join(basename, @file.public_filename))
 raise if basename !=
      File.expand_path(File.join(File.dirname(filename), '../../../'))
@@ -796,7 +803,7 @@ In December 2006, 34,000 actual user names and passwords were stolen in a [MySpa
 
 INFO: _CSS Injection is actually JavaScript injection, because some browsers (IE, some versions of Safari and others) allow JavaScript in CSS. Think twice about allowing custom CSS in your web application._
 
-CSS Injection is explained best by the well-known [MySpace Samy worm](http://namb.la/popular/tech.html). This worm automatically sent a friend request to Samy (the attacker) simply by visiting his profile. Within several hours he had over 1 million friend requests, which created so much traffic that MySpace went offline. The following is a technical explanation of that worm.
+CSS Injection is explained best by the well-known [MySpace Samy worm](https://samy.pl/popular/tech.html). This worm automatically sent a friend request to Samy (the attacker) simply by visiting his profile. Within several hours he had over 1 million friend requests, which created so much traffic that MySpace went offline. The following is a technical explanation of that worm.
 
 MySpace blocked many tags, but allowed CSS. So the worm's author put JavaScript into CSS like this:
 
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 7741834153..1db48ed56c 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -350,7 +350,9 @@ Rails adds some custom assertions of its own to the `minitest` framework:
 | --------------------------------------------------------------------------------- | ------- |
 | [`assert_difference(expressions, difference = 1, message = nil) {...}`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_difference) | Test numeric difference between the return value of an expression as a result of what is evaluated in the yielded block.|
 | [`assert_no_difference(expressions, message = nil, &block)`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_no_difference) | Asserts that the numeric result of evaluating an expression is not changed before and after invoking the passed in block.|
-| [`assert_nothing_raised { block }`](http://api.rubyonrails.org/classes/ActiveSupport/TestCase.html#method-i-assert_nothing_raised) | Ensures that the given block doesn't raise any exceptions.|
+| [`assert_changes(expressions, message = nil, from:, to:, &block) {...}`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_changes) | Test that the result of evaluating an expression is changed after invoking the passed in block.|
+| [`assert_no_changes(expressions, message = nil, &block)`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_no_changes) | Test the result of evaluating an expression is not changed after invoking the passed in block.|
+| [`assert_nothing_raised { block }`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_nothing_raised) | Ensures that the given block doesn't raise any exceptions.|
 | [`assert_recognizes(expected_options, path, extras={}, message=nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/RoutingAssertions.html#method-i-assert_recognizes) | Asserts that the routing of the given path was handled correctly and that the parsed options (given in the expected_options hash) match path. Basically, it asserts that Rails recognizes the route given by expected_options.|
 | [`assert_generates(expected_path, options, defaults={}, extras = {}, message=nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/RoutingAssertions.html#method-i-assert_generates) | Asserts that the provided options can be used to generate the provided path. This is the inverse of assert_recognizes. The extras parameter is used to tell the request the names and values of additional request parameters that would be in a query string. The message parameter allows you to specify a custom error message for assertion failures.|
 | [`assert_response(type, message = nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/ResponseAssertions.html#method-i-assert_response) | Asserts that the response comes with a specific status code. You can specify `:success` to indicate 200-299, `:redirect` to indicate 300-399, `:missing` to indicate 404, or `:error` to match the 500-599 range. You can also pass an explicit status number or its symbolic equivalent. For more information, see [full list of status codes](http://rubydoc.info/github/rack/rack/master/Rack/Utils#HTTP_STATUS_CODES-constant) and how their [mapping](http://rubydoc.info/github/rack/rack/master/Rack/Utils#SYMBOL_TO_STATUS_CODE-constant) works.|
@@ -610,9 +612,9 @@ For creating Rails system tests, you use the `test/system` directory in your
 application. Rails provides a generator to create a system test skeleton for you.
 
 ```bash
-$ bin/rails generate system_test users_create
+$ bin/rails generate system_test users
       invoke test_unit
-      create test/system/users_creates_test.rb
+      create test/system/users_test.rb
 ```
 
 Here's what a freshly-generated system test looks like:
@@ -620,11 +622,11 @@ Here's what a freshly-generated system test looks like:
 ```ruby
 require "application_system_test_case"
 
-class UsersCreatesTest < ApplicationSystemTestCase
+class UsersTest < ApplicationSystemTestCase
   # test "visiting the index" do
-  #   visit users_creates_url
+  #   visit users_url
   #
-  #   assert_selector "h1", text: "UsersCreate"
+  #   assert_selector "h1", text: "Users"
   # end
 end
 ```
@@ -658,8 +660,8 @@ end
 
 The driver name is a required argument for `driven_by`. The optional arguments
 that can be passed to `driven_by` are `:using` for the browser (this will only
-be used for non-headless drivers like Selenium), and `:screen_size` to change
-the size of the screen for screenshots.
+be used by Selenium), and `:screen_size` to change the size of the screen for
+screenshots.
 
 ```ruby
 require "test_helper"
@@ -1406,7 +1408,7 @@ In order to test that your mailer is working as expected, you can use unit tests
 
 For the purposes of unit testing a mailer, fixtures are used to provide an example of how the output _should_ look. Because these are example emails, and not Active Record data like the other fixtures, they are kept in their own subdirectory apart from the other fixtures. The name of the directory within `test/fixtures` directly corresponds to the name of the mailer. So, for a mailer named `UserMailer`, the fixtures should reside in `test/fixtures/user_mailer` directory.
 
-When you generated your mailer, the generator creates stub fixtures for each of the mailers actions. If you didn't use the generator, you'll have to create those files yourself.
+If you generated your mailer, the generator does not create stub fixtures for the mailers actions. You'll have to create those files yourself as described above.
 
 #### The Basic Test Case
 
@@ -1482,7 +1484,7 @@ class UserControllerTest < ActionDispatch::IntegrationTest
 
     assert_equal "You have been invited by me@example.com", invite_email.subject
     assert_equal 'friend@example.com', invite_email.to[0]
-    assert_match(/Hi friend@example.com/, invite_email.body.to_s)
+    assert_match(/Hi friend@example\.com/, invite_email.body.to_s)
   end
 end
 ```
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index ff747a95a0..93864db141 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -83,7 +83,7 @@ Also, if you have pretty old YAML documents containing dumps of such objects,
 you may need to load and dump them again to make sure that they reference
 the right constant, and that loading them won't break in the future.
 
-### `config.secrets` now loaded with all keys as symbols
+### `application.secrets` now loaded with all keys as symbols
 
 If your application stores nested configuration in `config/secrets.yml`, all keys
 are now loaded as symbols, so access using strings should be changed.
@@ -91,13 +91,13 @@ are now loaded as symbols, so access using strings should be changed.
 From:
 
 ```ruby
-Rails.appplication.config.secrets[:smtp_settings]["address"]
+Rails.application.secrets[:smtp_settings]["address"]
 ```
 
 To:
 
 ```ruby
-Rails.application.config.secrets[:smtp_settings][:address]
+Rails.application.secrets[:smtp_settings][:address]
 ```
 
 Upgrading from Rails 4.2 to Rails 5.0
diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md
index 2a6a87c232..290f2a509b 100644
--- a/guides/source/working_with_javascript_in_rails.md
+++ b/guides/source/working_with_javascript_in_rails.md
@@ -141,6 +141,8 @@ follow this pattern.
 Built-in Helpers
 ----------------------
 
+### Remote elements
+
 Rails provides a bunch of view helper methods written in Ruby to assist you
 in generating HTML. Sometimes, you want to add a little Ajax to those elements,
 and Rails has got your back in those cases.
@@ -153,14 +155,18 @@ Unless you have disabled the Asset Pipeline,
 provides the JavaScript half, and the regular Ruby view helpers add appropriate
 tags to your DOM.
 
-### form_for
+You can read below about the different events that are fired dealing with
+remote elements inside your application.
+
+#### form_with
 
-[`form_for`](http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_for)
-is a helper that assists with writing forms. `form_for` takes a `:remote`
-option. It works like this:
+[`form_with`](http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_with)
+is a helper that assists with writing forms. By default, `form_with` assumes that
+your form will be using Ajax. You can opt out of this behavior by
+passing the `:local` option `form_with`.
 
 ```erb
-<%= form_for(@article, remote: true) do |f| %>
+<%= form_with(model: @article) do |f| %>
   ...
 <% end %>
 ```
@@ -168,7 +174,7 @@ option. It works like this:
 This will generate the following HTML:
 
 ```html
-<form accept-charset="UTF-8" action="/articles" class="new_article" data-remote="true" id="new_article" method="post">
+<form action="/articles" method="post" data-remote="true">
   ...
 </form>
 ```
@@ -189,32 +195,9 @@ $(document).ready ->
 ```
 
 Obviously, you'll want to be a bit more sophisticated than that, but it's a
-start. You can see more about the events [in the jquery-ujs wiki](https://github.com/rails/jquery-ujs/wiki/ajax).
-
-### form_tag
-
-[`form_tag`](http://api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html#method-i-form_tag)
-is very similar to `form_for`. It has a `:remote` option that you can use like
-this:
-
-```erb
-<%= form_tag('/articles', remote: true) do %>
-  ...
-<% end %>
-```
-
-This will generate the following HTML:
-
-```html
-<form accept-charset="UTF-8" action="/articles" data-remote="true" method="post">
-  ...
-</form>
-```
-
-Everything else is the same as `form_for`. See its documentation for full
-details.
+start.
 
-### link_to
+#### link_to
 
 [`link_to`](http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to)
 is a helper that assists with generating links. It has a `:remote` option you
@@ -230,7 +213,7 @@ which generates
 <a href="/articles/1" data-remote="true">an article</a>
 ```
 
-You can bind to the same Ajax events as `form_for`. Here's an example. Let's
+You can bind to the same Ajax events as `form_with`. Here's an example. Let's
 assume that we have a list of articles that can be deleted with just one
 click. We would generate some HTML like this:
 
@@ -246,7 +229,7 @@ $ ->
     alert "The article was deleted."
 ```
 
-### button_to
+#### button_to
 
 [`button_to`](http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-button_to) is a helper that helps you create buttons. It has a `:remote` option that you can call like this:
 
@@ -262,7 +245,136 @@ this generates
 </form>
 ```
 
-Since it's just a `<form>`, all of the information on `form_for` also applies.
+Since it's just a `<form>`, all of the information on `form_with` also applies.
+
+### Customize remote elements
+
+It is possible to customize the behavior of elements with a `data-remote`
+attribute without writing a line of JavaScript. You can specify extra `data-`
+attributes to accomplish this.
+
+#### `data-method`
+
+Activating hyperlinks always results in an HTTP GET request. However, if your
+application is [RESTful](http://en.wikipedia.org/wiki/Representational_State_Transfer),
+some links are in fact actions that change data on the server, and must be
+performed with non-GET requests. This attribute allows marking up such links
+with an explicit method such as "post", "put" or "delete".
+
+The way it works is that, when the link is activated, it constructs a hidden form
+in the document with the "action" attribute corresponding to "href" value of the
+link, and the method corresponding to `data-method` value, and submits that form.
+
+NOTE: Because submitting forms with HTTP methods other than GET and POST isn't
+widely supported across browsers, all other HTTP methods are actually sent over
+POST with the intended method indicated in the `_method` parameter. Rails
+automatically detects and compensates for this.
+
+#### `data-url` and `data-params`
+
+Certain elements of your page aren't actually referring to any URL, but you may want
+them to trigger Ajax calls. Specifying the `data-url` attribute along with
+the `data-remote` one will trigger an Ajax call to the given URL. You can also
+specify extra parameters through the `data-params` attribute.
+
+This can be useful to trigger an action on check-boxes for instance:
+
+```html
+<input type="checkbox" data-remote="true"
+    data-url="/update" data-params="id=10" data-method="put">
+```
+
+#### `data-type`
+
+It is also possible to define the Ajax `dataType` explicitly while performing
+requests for `data-remote` elements, by way of the `data-type` attribute.
+
+### Confirmations
+
+You can ask for an extra confirmation of the user by adding a `data-confirm`
+attribute on links and forms. The user will be presented a JavaScript `confirm()`
+dialog containing the attribute's text. If the user chooses to cancel, the action
+doesn't take place.
+
+Adding this attribute on links will trigger the dialog on click, and adding it
+on forms will trigger it on submit. For example:
+
+```erb
+<%= link_to "Dangerous zone", dangerous_zone_path,
+  data: { confirm: 'Are you sure?' } %>
+```
+
+This generates:
+
+```html
+<a href="..." data-confirm="Are you sure?">Dangerous zone</a>
+```
+
+The attribute is also allowed on form submit buttons. This allows you to customize
+the warning message depending on the button which was activated. In this case,
+you should **not** have `data-confirm` on the form itself.
+
+The default confirmation uses a JavaScript confirm dialog, but you can customize
+this by listening to the `confirm` event, which is fired just before the confirmation
+window appears to the user. To cancel this default confirmation, have the confirm
+handler to return `false`.
+
+### Automatic disabling
+
+It is also possible to automatically disable an input while the form is submitting
+by using the `data-disable-with` attribute. This is to prevent accidental
+double-clicks from the user, which could result in duplicate HTTP requests that
+the backend may not detect as such. The value of the attribute is the text that will
+become the new value of the button in its disabled state.
+
+This also works for links with `data-method` attribute.
+
+For example:
+
+```erb
+<%= form_with(model: @article.new) do |f| %>
+  <%= f.submit data: { "disable-with": "Saving..." } %>
+<%= end %>
+```
+
+This generates a form with:
+
+```html
+<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.
 
 Server-Side Concerns
 --------------------
@@ -297,7 +409,7 @@ The index view (`app/views/users/index.html.erb`) contains:
 
 <br>
 
-<%= form_for(@user, remote: true) do |f| %>
+<%= form_with(model: @user) do |f| %>
   <%= f.label :name %><br>
   <%= f.text_field :name %>
   <%= f.submit %>
diff --git a/rails.gemspec b/rails.gemspec
index 2d5be58c17..91316f089f 100644
--- a/rails.gemspec
+++ b/rails.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 5463b05b60..d93c532c7e 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,8 +1,17 @@
+*   Allow irb options to be passed from `rails console` command.
+
+    Fixes #28988.
+
+    *Yuji Yaginuma*
+
+*   Added a shared section to config/database.yml that will be loaded for all environments.
+
+    *Pierre Schambacher*
+
 *   Namespace error pages' CSS selectors to stop the styles from bleeding into other pages
-    when using Turbolinks. 
-    
+    when using Turbolinks.
+
     *Jan Krutisch*
 
-    
 
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/railties/CHANGELOG.md) for previous changes.
diff --git a/railties/Rakefile b/railties/Rakefile
index 680ed03f75..d6284b7dc5 100644
--- a/railties/Rakefile
+++ b/railties/Rakefile
@@ -16,10 +16,10 @@ namespace :test do
       dash_i = [
         "test",
         "lib",
-        "#{File.dirname(__FILE__)}/../activesupport/lib",
-        "#{File.dirname(__FILE__)}/../actionpack/lib",
-        "#{File.dirname(__FILE__)}/../actionview/lib",
-        "#{File.dirname(__FILE__)}/../activemodel/lib"
+        "#{__dir__}/../activesupport/lib",
+        "#{__dir__}/../actionpack/lib",
+        "#{__dir__}/../actionview/lib",
+        "#{__dir__}/../activemodel/lib"
       ]
       ruby "-w", "-I#{dash_i.join ':'}", file
     end
@@ -27,7 +27,7 @@ namespace :test do
 end
 
 Rake::TestTask.new("test:regular") do |t|
-  t.libs << "test" << "#{File.dirname(__FILE__)}/../activesupport/lib"
+  t.libs << "test" << "#{__dir__}/../activesupport/lib"
   t.pattern = "test/**/*_test.rb"
   t.warning = false
   t.verbose = true
diff --git a/railties/exe/rails b/railties/exe/rails
index 7e791c1f99..a5635c2297 100755
--- a/railties/exe/rails
+++ b/railties/exe/rails
@@ -1,9 +1,9 @@
 #!/usr/bin/env ruby
 
-git_path = File.expand_path("../../../.git", __FILE__)
+git_path = File.expand_path("../../.git", __dir__)
 
 if File.exist?(git_path)
-  railties_path = File.expand_path("../../lib", __FILE__)
+  railties_path = File.expand_path("../lib", __dir__)
   $:.unshift(railties_path)
 end
 require "rails/cli"
diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index f8a923141d..39ca2db8e1 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -260,6 +260,7 @@ module Rails
           "action_dispatch.signed_cookie_salt" => config.action_dispatch.signed_cookie_salt,
           "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.cookies_serializer" => config.action_dispatch.cookies_serializer,
           "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest
         )
diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index 7c49fabba5..4ffde6198a 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -77,9 +77,21 @@ module Rails
             assets.unknown_asset_fallback = false
           end
 
+          if respond_to?(:action_view)
+            action_view.form_with_generates_remote_forms = true
+          end
+
         when "5.2"
           load_defaults "5.1"
 
+          if respond_to?(:active_record)
+            active_record.cache_versioning = true
+          end
+
+          if respond_to?(:action_dispatch)
+            action_dispatch.use_authenticated_cookie_encryption = true
+          end
+
         else
           raise "Unknown version #{target_version.to_s.inspect}"
         end
@@ -133,7 +145,14 @@ module Rails
         config = if yaml && yaml.exist?
           require "yaml"
           require "erb"
-          YAML.load(ERB.new(yaml.read).result) || {}
+          loaded_yaml = YAML.load(ERB.new(yaml.read).result) || {}
+          shared = loaded_yaml.delete("shared")
+          if shared
+            loaded_yaml.each do |_k, values|
+              values.reverse_merge!(shared)
+            end
+          end
+          Hash.new(shared).merge(loaded_yaml)
         elsif ENV["DATABASE_URL"]
           # Value from ENV['DATABASE_URL'] is set to default database connection
           # by Active Record.
diff --git a/railties/lib/rails/application_controller.rb b/railties/lib/rails/application_controller.rb
index a98e51fd28..f7d112900a 100644
--- a/railties/lib/rails/application_controller.rb
+++ b/railties/lib/rails/application_controller.rb
@@ -1,5 +1,5 @@
 class Rails::ApplicationController < ActionController::Base # :nodoc:
-  self.view_paths = File.expand_path("../templates", __FILE__)
+  self.view_paths = File.expand_path("templates", __dir__)
   layout "application"
 
   private
diff --git a/railties/lib/rails/command.rb b/railties/lib/rails/command.rb
index 0d4e6dc5a1..ee020b58f9 100644
--- a/railties/lib/rails/command.rb
+++ b/railties/lib/rails/command.rb
@@ -23,7 +23,7 @@ module Rails
       end
 
       def environment # :nodoc:
-        ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "development"
+        ENV["RAILS_ENV"].presence || ENV["RACK_ENV"].presence || "development"
       end
 
       # Receives a namespace, arguments and the behavior to invoke the command.
diff --git a/railties/lib/rails/command/actions.rb b/railties/lib/rails/command/actions.rb
index 8fda1c87c6..a00e58997c 100644
--- a/railties/lib/rails/command/actions.rb
+++ b/railties/lib/rails/command/actions.rb
@@ -5,7 +5,7 @@ module Rails
       # This allows us to run `rails server` from other directories, but still get
       # the main config.ru and properly set the tmp directory.
       def set_application_directory!
-        Dir.chdir(File.expand_path("../../", APP_PATH)) unless File.exist?(File.expand_path("config.ru"))
+        Dir.chdir(File.expand_path("../..", APP_PATH)) unless File.exist?(File.expand_path("config.ru"))
       end
 
       def require_application_and_environment!
diff --git a/railties/lib/rails/commands/console/console_command.rb b/railties/lib/rails/commands/console/console_command.rb
index 62e3aa19df..ec58540923 100644
--- a/railties/lib/rails/commands/console/console_command.rb
+++ b/railties/lib/rails/commands/console/console_command.rb
@@ -73,14 +73,26 @@ module Rails
       class_option :environment, aliases: "-e", type: :string,
         desc: "Specifies the environment to run this console under (test/development/production)."
 
+      def initialize(args = [], local_options = {}, config = {})
+        console_options = []
+
+        # For the same behavior as OptionParser, leave only options after "--" in ARGV.
+        termination = local_options.find_index("--")
+        if termination
+          console_options = local_options[termination + 1..-1]
+          local_options = local_options[0...termination]
+        end
+
+        ARGV.replace(console_options)
+        super(args, local_options, config)
+      end
+
       def perform
         extract_environment_option_from_argument
 
         # RAILS_ENV needs to be set before config/application is required.
         ENV["RAILS_ENV"] = options[:environment]
 
-        ARGV.clear # Clear ARGV so IRB doesn't freak.
-
         require_application_and_environment!
         Rails::Console.start(Rails.application, options)
       end
diff --git a/railties/lib/rails/commands/help/USAGE b/railties/lib/rails/commands/help/USAGE
index c5f8ab72bb..8eb98319d2 100644
--- a/railties/lib/rails/commands/help/USAGE
+++ b/railties/lib/rails/commands/help/USAGE
@@ -1,13 +1,14 @@
 The most common rails commands are:
- generate    Generate new code (short-cut alias: "g")
- console     Start the Rails console (short-cut alias: "c")
- server      Start the Rails server (short-cut alias: "s")
- test        Run tests (short-cut alias: "t")
- dbconsole   Start a console for the database specified in config/database.yml
-             (short-cut alias: "db")
+ generate     Generate new code (short-cut alias: "g")
+ console      Start the Rails console (short-cut alias: "c")
+ server       Start the Rails server (short-cut alias: "s")
+ test         Run tests except system tests (short-cut alias: "t")
+ test:system  Run system tests
+ dbconsole    Start a console for the database specified in config/database.yml
+              (short-cut alias: "db")
 <% unless engine? %>
- new         Create a new Rails application. "rails new my_app" creates a
-             new application called MyApp in "./my_app"
+ new          Create a new Rails application. "rails new my_app" creates a
+              new application called MyApp in "./my_app"
 <% end %>
 
 All commands can be run with -h (or --help) for more information.
diff --git a/railties/lib/rails/commands/secrets/secrets_command.rb b/railties/lib/rails/commands/secrets/secrets_command.rb
index 03a640bd65..651411d444 100644
--- a/railties/lib/rails/commands/secrets/secrets_command.rb
+++ b/railties/lib/rails/commands/secrets/secrets_command.rb
@@ -13,10 +13,7 @@ module Rails
       end
 
       def setup
-        require "rails/generators"
-        require "rails/generators/rails/encrypted_secrets/encrypted_secrets_generator"
-
-        Rails::Generators::EncryptedSecretsGenerator.start
+        generator.start
       end
 
       def edit
@@ -34,7 +31,6 @@ module Rails
         require_application_and_environment!
 
         Rails::Secrets.read_for_editing do |tmp_path|
-          say "Waiting for secrets file to be saved. Abort with Ctrl-C."
           system("\$EDITOR #{tmp_path}")
         end
 
@@ -43,7 +39,22 @@ module Rails
         say "Aborted changing encrypted secrets: nothing saved."
       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("\$EDITOR #{tmp_path}")
+          generator.skip_secrets_file { setup }
+        end
       end
+
+      private
+        def generator
+          require "rails/generators"
+          require "rails/generators/rails/encrypted_secrets/encrypted_secrets_generator"
+
+          Rails::Generators::EncryptedSecretsGenerator
+        end
     end
   end
 end
diff --git a/railties/lib/rails/commands/server/server_command.rb b/railties/lib/rails/commands/server/server_command.rb
index 278fe63c51..ebb4ae795a 100644
--- a/railties/lib/rails/commands/server/server_command.rb
+++ b/railties/lib/rails/commands/server/server_command.rb
@@ -95,10 +95,11 @@ module Rails
 
   module Command
     class ServerCommand < Base # :nodoc:
+      DEFAULT_PORT = 3000
       DEFAULT_PID_PATH = "tmp/pids/server.pid".freeze
 
       class_option :port, aliases: "-p", type: :numeric,
-        desc: "Runs Rails on the specified port.", banner: :port, default: 3000
+        desc: "Runs Rails on the specified port - defaults to 3000.", banner: :port
       class_option :binding, aliases: "-b", type: :string,
         desc: "Binds Rails to the specified IP - defaults to 'localhost' in development and '0.0.0.0' in other environments'.",
         banner: :IP
@@ -154,9 +155,16 @@ module Rails
         def user_supplied_options
           @user_supplied_options ||= begin
             # Convert incoming options array to a hash of flags
-            #   ["-p", "3001", "-c", "foo"] # => {"-p" => true, "-c" => true}
+            #   ["-p3001", "-C", "--binding", "127.0.0.1"] # => {"-p"=>true, "-C"=>true, "--binding"=>true}
             user_flag = {}
-            @original_options.each_with_index { |command, i| user_flag[command] = true if i.even? }
+            @original_options.each do |command|
+              if command.to_s.start_with?("--")
+                option = command.split("=")[0]
+                user_flag[option] = true
+              elsif command =~ /\A(-.)/
+                user_flag[Regexp.last_match[0]] = true
+              end
+            end
 
             # Collect all options that the user has explicitly defined so we can
             # differentiate them from defaults
@@ -184,7 +192,7 @@ module Rails
         end
 
         def port
-          ENV.fetch("PORT", options[:port]).to_i
+          options[:port] || ENV.fetch("PORT", DEFAULT_PORT).to_i
         end
 
         def host
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index dc0b158bd4..2732485c5a 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -40,7 +40,7 @@ module Rails
   #
   #   class MyEngine < Rails::Engine
   #     # Add a load path for this specific Engine
-  #     config.autoload_paths << File.expand_path("../lib/some/path", __FILE__)
+  #     config.autoload_paths << File.expand_path("lib/some/path", __dir__)
   #
   #     initializer "my_engine.add_middleware" do |app|
   #       app.middleware.use MyEngine::Middleware
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index 8ec805370b..8f15f3a594 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -1,4 +1,4 @@
-activesupport_path = File.expand_path("../../../../activesupport/lib", __FILE__)
+activesupport_path = File.expand_path("../../../activesupport/lib", __dir__)
 $:.unshift(activesupport_path) if File.directory?(activesupport_path) && !$:.include?(activesupport_path)
 
 require "thor/group"
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index c715e5ac9f..e8b104a0b2 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -13,7 +13,6 @@ module Rails
       DATABASES = %w( mysql postgresql sqlite3 oracle frontbase ibm_db sqlserver )
       JDBC_DATABASES = %w( jdbcmysql jdbcsqlite3 jdbcpostgresql jdbc )
       DATABASES.concat(JDBC_DATABASES)
-      WEBPACKS = %w( react vue angular )
 
       attr_accessor :rails_template
       add_shebang_option!
@@ -31,9 +30,6 @@ module Rails
         class_option :database,           type: :string, aliases: "-d", default: "sqlite3",
                                           desc: "Preconfigure for selected database (options: #{DATABASES.join('/')})"
 
-        class_option :webpack,            type: :string, default: nil,
-                                          desc: "Preconfigure for app-like JavaScript with Webpack (options: #{WEBPACKS.join('/')})"
-
         class_option :skip_yarn,          type: :boolean, default: false,
                                           desc: "Don't use Yarn for managing JavaScript dependencies"
 
diff --git a/railties/lib/rails/generators/base.rb b/railties/lib/rails/generators/base.rb
index a650c52626..e7f51dba99 100644
--- a/railties/lib/rails/generators/base.rb
+++ b/railties/lib/rails/generators/base.rb
@@ -215,7 +215,7 @@ module Rails
       # Returns the base root for a common set of generators. This is used to dynamically
       # guess the default source root.
       def self.base_root
-        File.dirname(__FILE__)
+        __dir__
       end
 
       # Cache source root and add lib/generators/base/generator/templates to
diff --git a/railties/lib/rails/generators/css/assets/assets_generator.rb b/railties/lib/rails/generators/css/assets/assets_generator.rb
index 20baf31a34..af7b5cf609 100644
--- a/railties/lib/rails/generators/css/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/css/assets/assets_generator.rb
@@ -3,7 +3,7 @@ require "rails/generators/named_base"
 module Css # :nodoc:
   module Generators # :nodoc:
     class AssetsGenerator < Rails::Generators::NamedBase # :nodoc:
-      source_root File.expand_path("../templates", __FILE__)
+      source_root File.expand_path("templates", __dir__)
 
       def copy_stylesheet
         copy_file "stylesheet.css", File.join("app/assets/stylesheets", class_path, "#{file_name}.css")
diff --git a/railties/lib/rails/generators/js/assets/assets_generator.rb b/railties/lib/rails/generators/js/assets/assets_generator.rb
index 64d706ec91..52a71b58cd 100644
--- a/railties/lib/rails/generators/js/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/js/assets/assets_generator.rb
@@ -3,7 +3,7 @@ require "rails/generators/named_base"
 module Js # :nodoc:
   module Generators # :nodoc:
     class AssetsGenerator < Rails::Generators::NamedBase # :nodoc:
-      source_root File.expand_path("../templates", __FILE__)
+      source_root File.expand_path("templates", __dir__)
 
       def copy_javascript
         copy_file "javascript.js", File.join("app/assets/javascripts", class_path, "#{file_name}.js")
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index f4717bb35b..45b9e7bdff 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -67,6 +67,10 @@ module Rails
       end
     end
 
+    def package_json
+      template "package.json"
+    end
+
     def app
       directory "app"
 
@@ -117,7 +121,6 @@ module Rails
       action_cable_config_exist = File.exist?("config/cable.yml")
       rack_cors_config_exist = File.exist?("config/initializers/cors.rb")
       assets_config_exist = File.exist?("config/initializers/assets.rb")
-      new_framework_defaults_5_1_exist = File.exist?("config/initializers/new_framework_defaults_5_1.rb")
 
       config
 
@@ -141,12 +144,6 @@ module Rails
         unless assets_config_exist
           remove_file "config/initializers/assets.rb"
         end
-
-        # Sprockets owns the only new default for 5.1:
-        # In API-only Applications, we don't want the file.
-        unless new_framework_defaults_5_1_exist
-          remove_file "config/initializers/new_framework_defaults_5_1.rb"
-        end
       end
     end
 
@@ -198,20 +195,18 @@ module Rails
 
     def vendor
       empty_directory_with_keep_file "vendor"
-
-      unless options[:skip_yarn]
-        template "package.json"
-      end
     end
   end
 
   module Generators
     # We need to store the RAILS_DEV_PATH in a constant, otherwise the path
     # can change in Ruby 1.8.7 when we FileUtils.cd.
-    RAILS_DEV_PATH = File.expand_path("../../../../../..", File.dirname(__FILE__))
+    RAILS_DEV_PATH = File.expand_path("../../../../../..", __dir__)
     RESERVED_NAMES = %w[application destroy plugin runner test]
 
     class AppGenerator < AppBase # :nodoc:
+      WEBPACKS = %w( react vue angular elm )
+
       add_shared_options_for "application"
 
       # Add bin/rails options
@@ -224,6 +219,9 @@ module Rails
       class_option :skip_bundle, type: :boolean, aliases: "-B", default: false,
                                  desc: "Don't run bundle install"
 
+      class_option :webpack, type: :string, default: nil,
+                             desc: "Preconfigure for app-like JavaScript with Webpack (options: #{WEBPACKS.join('/')})"
+
       def initialize(*args)
         super
 
@@ -248,6 +246,7 @@ module Rails
         build(:gitignore)   unless options[:skip_git]
         build(:gemfile)     unless options[:skip_gemfile]
         build(:version_control)
+        build(:package_json) unless options[:skip_yarn]
       end
 
       def create_app_files
@@ -317,10 +316,6 @@ module Rails
 
       def create_vendor_files
         build(:vendor)
-
-        if options[:skip_yarn]
-          remove_file "package.json"
-        end
       end
 
       def delete_app_assets_if_api_option
@@ -404,7 +399,7 @@ module Rails
 
       def delete_new_framework_defaults
         unless options[:update]
-          remove_file "config/initializers/new_framework_defaults_5_1.rb"
+          remove_file "config/initializers/new_framework_defaults_5_2.rb"
         end
       end
 
diff --git a/railties/lib/rails/generators/rails/app/templates/Gemfile b/railties/lib/rails/generators/rails/app/templates/Gemfile
index 06f0dd6d6d..747d2e6253 100644
--- a/railties/lib/rails/generators/rails/app/templates/Gemfile
+++ b/railties/lib/rails/generators/rails/app/templates/Gemfile
@@ -1,9 +1,5 @@
 source 'https://rubygems.org'
-
-git_source(:github) do |repo_name|
-  repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?("/")
-  "https://github.com/#{repo_name}.git"
-end
+git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
 <% gemfile_entries.each do |gem| -%>
 <% if gem.comment -%>
@@ -34,7 +30,7 @@ group :development, :test do
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
   <%- if depends_on_system_test? -%>
   # Adds support for Capybara system testing and selenium driver
-  gem 'capybara', '~> 2.13.0'
+  gem 'capybara', '~> 2.13'
   gem 'selenium-webdriver'
   <%- end -%>
 end
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/bundle b/railties/lib/rails/generators/rails/app/templates/bin/bundle
index 1123dcf501..a84f0afe47 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/bundle
+++ b/railties/lib/rails/generators/rails/app/templates/bin/bundle
@@ -1,2 +1,2 @@
-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/railties/lib/rails/generators/rails/app/templates/bin/setup.tt b/railties/lib/rails/generators/rails/app/templates/bin/setup.tt
index 52b3de5ee5..560cc64a3f 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/setup.tt
+++ b/railties/lib/rails/generators/rails/app/templates/bin/setup.tt
@@ -3,7 +3,7 @@ require 'fileutils'
 include FileUtils
 
 # path to your application root.
-APP_ROOT = Pathname.new File.expand_path('../../', __FILE__)
+APP_ROOT = Pathname.new File.expand_path('..', __dir__)
 
 def system!(*args)
   system(*args) || abort("\n== Command #{args} failed ==")
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 d385b363c6..0aedf0d6e2 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/update.tt
+++ b/railties/lib/rails/generators/rails/app/templates/bin/update.tt
@@ -3,7 +3,7 @@ require 'fileutils'
 include FileUtils
 
 # path to your application root.
-APP_ROOT = Pathname.new File.expand_path('../../', __FILE__)
+APP_ROOT = Pathname.new File.expand_path('..', __dir__)
 
 def system!(*args)
   system(*args) || abort("\n== Command #{args} failed ==")
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_1.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_1.rb.tt
deleted file mode 100644
index a0c7f44b60..0000000000
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_1.rb.tt
+++ /dev/null
@@ -1,16 +0,0 @@
-# Be sure to restart your server when you modify this file.
-#
-# This file contains migration options to ease your Rails 5.1 upgrade.
-#
-# Once upgraded flip defaults one by one to migrate to the new default.
-#
-# Read the Guide for Upgrading Ruby on Rails for more info on each option.
-
-# Make `form_with` generate non-remote forms.
-Rails.application.config.action_view.form_with_generates_remote_forms = false
-<%- unless options[:skip_sprockets] -%>
-
-# Unknown asset fallback will return the path passed in when the given
-# asset is not present in the asset pipeline.
-# Rails.application.config.assets.unknown_asset_fallback = false
-<%- end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt
new file mode 100644
index 0000000000..900baa607a
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt
@@ -0,0 +1,15 @@
+# Be sure to restart your server when you modify this file.
+#
+# This file contains migration options to ease your Rails 5.2 upgrade.
+#
+# Once upgraded flip defaults one by one to migrate to the new default.
+#
+# Read the Guide for Upgrading Ruby on Rails for more info on each option.
+
+# Make Active Record use stable #cache_key alongside new #cache_version method.
+# This is needed for recyclable cache keys.
+# Rails.application.config.active_record.cache_versioning = true
+
+# Use AES 256 GCM authenticated encryption for encrypted cookies.
+# Existing cookies will be converted on read then written with the new scheme.
+# Rails.application.config.action_dispatch.use_authenticated_cookie_encryption = true
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
index 2f92168eef..7568af5b5e 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
@@ -1,4 +1,4 @@
-require File.expand_path('../../config/environment', __FILE__)
+require File.expand_path('../config/environment', __dir__)
 require 'rails/test_help'
 
 class ActiveSupport::TestCase
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
index 8b29213610..1da2fbc1a5 100644
--- a/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb
+++ b/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb
@@ -36,25 +36,29 @@ module Rails
       end
 
       def add_encrypted_secrets_file
-        unless File.exist?("config/secrets.yml.enc")
+        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 ""
 
-          template "config/secrets.yml.enc" do |prefill|
-            say ""
-            say "For now the file contains this but it's been encrypted with the generated key:"
-            say ""
-            say prefill, :on_green
-            say ""
-
-            Secrets.encrypt(prefill)
-          end
+          Secrets.write(Secrets.template)
 
           say "You can edit encrypted secrets with `bin/rails secrets:edit`."
-
-          say "Add this to your config/environments/production.rb:"
-          say "config.read_encrypted_secrets = true"
+          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
diff --git a/railties/lib/rails/generators/rails/encrypted_secrets/templates/config/secrets.yml.enc b/railties/lib/rails/generators/rails/encrypted_secrets/templates/config/secrets.yml.enc
deleted file mode 100644
index 70426a66a5..0000000000
--- a/railties/lib/rails/generators/rails/encrypted_secrets/templates/config/secrets.yml.enc
+++ /dev/null
@@ -1,3 +0,0 @@
-# See `secrets.yml` for tips on generating suitable keys.
-# production:
-#  external_api_key: 1466aac22e6a869134be3d09b9e89232fc2c2289…
diff --git a/railties/lib/rails/generators/rails/generator/templates/%file_name%_generator.rb.tt b/railties/lib/rails/generators/rails/generator/templates/%file_name%_generator.rb.tt
index d0575772bc..178d5c3f9f 100644
--- a/railties/lib/rails/generators/rails/generator/templates/%file_name%_generator.rb.tt
+++ b/railties/lib/rails/generators/rails/generator/templates/%file_name%_generator.rb.tt
@@ -1,3 +1,3 @@
 class <%= class_name %>Generator < Rails::Generators::NamedBase
-  source_root File.expand_path('../templates', __FILE__)
+  source_root File.expand_path('templates', __dir__)
 end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec b/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec
index d84d1aabdb..9a8c4bf098 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec
+++ b/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec
@@ -1,4 +1,4 @@
-$:.push File.expand_path("../lib", __FILE__)
+$:.push File.expand_path("lib", __dir__)
 
 # Maintain your gem's version:
 require "<%= namespaced_name %>/version"
diff --git a/railties/lib/rails/generators/rails/plugin/templates/Rakefile b/railties/lib/rails/generators/rails/plugin/templates/Rakefile
index 383d2fb2d1..3581dd401a 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/Rakefile
+++ b/railties/lib/rails/generators/rails/plugin/templates/Rakefile
@@ -15,7 +15,7 @@ RDoc::Task.new(:rdoc) do |rdoc|
 end
 
 <% if engine? && !options[:skip_active_record] && with_dummy_app? -%>
-APP_RAKEFILE = File.expand_path("../<%= dummy_path -%>/Rakefile", __FILE__)
+APP_RAKEFILE = File.expand_path("<%= dummy_path -%>/Rakefile", __dir__)
 load 'rails/tasks/engine.rake'
 <% end %>
 
diff --git a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
index c03d9953d4..ffa277e334 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
@@ -1,12 +1,12 @@
 # This command will automatically be run when you run "rails" with Rails gems
 # installed from the root of your application.
 
-ENGINE_ROOT = File.expand_path('../..', __FILE__)
-ENGINE_PATH = File.expand_path('../../lib/<%= namespaced_name -%>/engine', __FILE__)
-APP_PATH = File.expand_path('../../<%= dummy_path -%>/config/application', __FILE__)
+ENGINE_ROOT = File.expand_path('..', __dir__)
+ENGINE_PATH = File.expand_path('../lib/<%= namespaced_name -%>/engine', __dir__)
+APP_PATH = File.expand_path('../<%= dummy_path -%>/config/application', __dir__)
 
 # Set up gems listed in the Gemfile.
-ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 require 'bundler/setup' if File.exist?(ENV['BUNDLE_GEMFILE'])
 
 require 'rails/all'
diff --git a/railties/lib/rails/generators/rails/plugin/templates/bin/test.tt b/railties/lib/rails/generators/rails/plugin/templates/bin/test.tt
index 8385e6a8a2..8e7d321626 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/bin/test.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/bin/test.tt
@@ -1,4 +1,4 @@
-$: << File.expand_path(File.expand_path("../../test", __FILE__))
+$: << File.expand_path("../test", __dir__)
 
 require "bundler/setup"
 require "rails/plugin/test"
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
index e84e403018..32e8202e1c 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
@@ -1,8 +1,8 @@
-require File.expand_path("../../<%= options[:dummy_path] -%>/config/environment.rb", __FILE__)
+require File.expand_path("../<%= options[:dummy_path] -%>/config/environment.rb", __dir__)
 <% unless options[:skip_active_record] -%>
-ActiveRecord::Migrator.migrations_paths = [File.expand_path("../../<%= options[:dummy_path] -%>/db/migrate", __FILE__)]
+ActiveRecord::Migrator.migrations_paths = [File.expand_path("../<%= options[:dummy_path] -%>/db/migrate", __dir__)]
 <% if options[:mountable] -%>
-ActiveRecord::Migrator.migrations_paths << File.expand_path('../../db/migrate', __FILE__)
+ActiveRecord::Migrator.migrations_paths << File.expand_path('../db/migrate', __dir__)
 <% end -%>
 <% end -%>
 require "rails/test_help"
@@ -17,7 +17,7 @@ Rails::TestUnitReporter.executable = 'bin/test'
 
 # Load fixtures from the engine
 if ActiveSupport::TestCase.respond_to?(:fixture_path=)
-  ActiveSupport::TestCase.fixture_path = File.expand_path("../fixtures", __FILE__)
+  ActiveSupport::TestCase.fixture_path = File.expand_path("fixtures", __dir__)
   ActionDispatch::IntegrationTest.fixture_path = ActiveSupport::TestCase.fixture_path
   ActiveSupport::TestCase.file_fixture_path = ActiveSupport::TestCase.fixture_path + "/files"
   ActiveSupport::TestCase.fixtures :all
diff --git a/railties/lib/rails/generators/test_case.rb b/railties/lib/rails/generators/test_case.rb
index 3eec929aeb..575af80303 100644
--- a/railties/lib/rails/generators/test_case.rb
+++ b/railties/lib/rails/generators/test_case.rb
@@ -14,7 +14,7 @@ module Rails
     #
     #   class AppGeneratorTest < Rails::Generators::TestCase
     #     tests AppGenerator
-    #     destination File.expand_path("../tmp", File.dirname(__FILE__))
+    #     destination File.expand_path("../tmp", __dir__)
     #   end
     #
     # If you want to ensure your destination root is clean before running each test,
@@ -22,7 +22,7 @@ module Rails
     #
     #   class AppGeneratorTest < Rails::Generators::TestCase
     #     tests AppGenerator
-    #     destination File.expand_path("../tmp", File.dirname(__FILE__))
+    #     destination File.expand_path("../tmp", __dir__)
     #     setup :prepare_destination
     #   end
     class TestCase < ActiveSupport::TestCase
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 aec415a4e5..0514957d9c 100644
--- a/railties/lib/rails/generators/test_unit/system/system_generator.rb
+++ b/railties/lib/rails/generators/test_unit/system/system_generator.rb
@@ -10,7 +10,7 @@ module TestUnit # :nodoc:
           template "application_system_test_case.rb", File.join("test", "application_system_test_case.rb")
         end
 
-        template "system_test.rb", File.join("test/system", "#{file_name.pluralize}_test.rb")
+        template "system_test.rb", File.join("test/system", class_path, "#{file_name.pluralize}_test.rb")
       end
     end
   end
diff --git a/railties/lib/rails/generators/testing/behaviour.rb b/railties/lib/rails/generators/testing/behaviour.rb
index 64d641d096..ce0e42e60d 100644
--- a/railties/lib/rails/generators/testing/behaviour.rb
+++ b/railties/lib/rails/generators/testing/behaviour.rb
@@ -14,12 +14,12 @@ module Rails
         include ActiveSupport::Testing::Stream
 
         included do
-          class_attribute :destination_root, :current_path, :generator_class, :default_arguments
-
           # Generators frequently change the current path using +FileUtils.cd+.
           # So we need to store the path at file load and revert back to it after each test.
-          self.current_path = File.expand_path(Dir.pwd)
-          self.default_arguments = []
+          class_attribute :current_path, default: File.expand_path(Dir.pwd)
+          class_attribute :default_arguments, default: []
+          class_attribute :destination_root
+          class_attribute :generator_class
         end
 
         module ClassMethods
@@ -40,7 +40,7 @@ module Rails
 
           # Sets the destination of generator files:
           #
-          #   destination File.expand_path("../tmp", File.dirname(__FILE__))
+          #   destination File.expand_path("../tmp", __dir__)
           def destination(path)
             self.destination_root = path
           end
@@ -51,7 +51,7 @@ module Rails
         #
         #   class AppGeneratorTest < Rails::Generators::TestCase
         #     tests AppGenerator
-        #     destination File.expand_path("../tmp", File.dirname(__FILE__))
+        #     destination File.expand_path("../tmp", __dir__)
         #     setup :prepare_destination
         #
         #     test "database.yml is not created when skipping Active Record" do
diff --git a/railties/lib/rails/secrets.rb b/railties/lib/rails/secrets.rb
index 8b644f212c..20c20cb9f1 100644
--- a/railties/lib/rails/secrets.rb
+++ b/railties/lib/rails/secrets.rb
@@ -1,5 +1,6 @@
 require "yaml"
 require "active_support/message_encryptor"
+require "active_support/core_ext/string/strip"
 
 module Rails
   # Greatly inspired by Ara T. Howard's magnificent sekrets gem. 😘
@@ -37,6 +38,15 @@ module Rails
         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
@@ -54,15 +64,12 @@ module Rails
         FileUtils.mv("#{path}.tmp", path)
       end
 
-      def read_for_editing
-        tmp_path = File.join(Dir.tmpdir, File.basename(path))
-        IO.binwrite(tmp_path, read)
-
-        yield tmp_path
+      def read_for_editing(&block)
+        writing(read, &block)
+      end
 
-        write(IO.binread(tmp_path))
-      ensure
-        FileUtils.rm(tmp_path) if File.exist?(tmp_path)
+      def read_template_for_editing(&block)
+        writing(template, &block)
       end
 
       private
@@ -92,6 +99,17 @@ module Rails
           end
         end
 
+        def writing(contents)
+          tmp_path = File.join(Dir.tmpdir, File.basename(path))
+          File.write(tmp_path, contents)
+
+          yield tmp_path
+
+          write(File.read(tmp_path))
+        ensure
+          FileUtils.rm(tmp_path) if File.exist?(tmp_path)
+        end
+
         def encryptor
           @encryptor ||= ActiveSupport::MessageEncryptor.new([ key ].pack("H*"), cipher: @cipher)
         end
diff --git a/railties/lib/rails/tasks/framework.rake b/railties/lib/rails/tasks/framework.rake
index 32a6b109bc..80720a42ff 100644
--- a/railties/lib/rails/tasks/framework.rake
+++ b/railties/lib/rails/tasks/framework.rake
@@ -16,7 +16,7 @@ namespace :app do
   namespace :templates do
     # desc "Copy all the templates from rails to the application directory for customization. Already existing local copies will be overwritten"
     task :copy do
-      generators_lib = File.expand_path("../../generators", __FILE__)
+      generators_lib = File.expand_path("../generators", __dir__)
       project_templates = "#{Rails.root}/lib/templates"
 
       default_templates = { "erb"   => %w{controller mailer scaffold},
diff --git a/railties/lib/rails/test_help.rb b/railties/lib/rails/test_help.rb
index 0f9bf98737..81537d813e 100644
--- a/railties/lib/rails/test_help.rb
+++ b/railties/lib/rails/test_help.rb
@@ -12,7 +12,12 @@ require "rails/generators/test_case"
 require "active_support/testing/autorun"
 
 if defined?(ActiveRecord::Base)
-  ActiveRecord::Migration.maintain_test_schema!
+  begin
+    ActiveRecord::Migration.maintain_test_schema!
+  rescue ActiveRecord::PendingMigrationError => e
+    puts e.to_s.strip
+    exit 1
+  end
 
   module ActiveSupport
     class TestCase
diff --git a/railties/lib/rails/test_unit/minitest_plugin.rb b/railties/lib/rails/test_unit/minitest_plugin.rb
index 8decdb0f4f..7a852d1109 100644
--- a/railties/lib/rails/test_unit/minitest_plugin.rb
+++ b/railties/lib/rails/test_unit/minitest_plugin.rb
@@ -6,7 +6,7 @@ require "shellwords"
 module Minitest
   class SuppressedSummaryReporter < SummaryReporter
     # Disable extra failure output after a run if output is inline.
-    def aggregated_results
+    def aggregated_results(*)
       super unless options[:output_inline]
     end
   end
diff --git a/railties/lib/rails/test_unit/railtie.rb b/railties/lib/rails/test_unit/railtie.rb
index 9cc3f73a9c..443e743421 100644
--- a/railties/lib/rails/test_unit/railtie.rb
+++ b/railties/lib/rails/test_unit/railtie.rb
@@ -1,7 +1,7 @@
 require "rails/test_unit/line_filtering"
 
 if defined?(Rake.application) && Rake.application.top_level_tasks.grep(/^(default$|test(:|$))/).any?
-  ENV["RAILS_ENV"] ||= "test"
+  ENV["RAILS_ENV"] ||= Rake.application.options.show_tasks ? "development" : "test"
 end
 
 module Rails
diff --git a/railties/lib/rails/test_unit/reporter.rb b/railties/lib/rails/test_unit/reporter.rb
index fe11664d5e..1cc27f7b6c 100644
--- a/railties/lib/rails/test_unit/reporter.rb
+++ b/railties/lib/rails/test_unit/reporter.rb
@@ -3,8 +3,7 @@ require "minitest"
 
 module Rails
   class TestUnitReporter < Minitest::StatisticsReporter
-    class_attribute :executable
-    self.executable = "bin/rails test"
+    class_attribute :executable, default: "bin/rails test"
 
     def record(result)
       super
diff --git a/railties/lib/rails/test_unit/testing.rake b/railties/lib/rails/test_unit/testing.rake
index ef19bd7626..33408081f1 100644
--- a/railties/lib/rails/test_unit/testing.rake
+++ b/railties/lib/rails/test_unit/testing.rake
@@ -48,6 +48,7 @@ namespace :test do
     Minitest.rake_run(["test/controllers", "test/mailers", "test/functional"])
   end
 
+  desc "Run system tests only"
   task system: "test:prepare" do
     $: << "test"
     Minitest.rake_run(["test/system"])
diff --git a/railties/railties.gemspec b/railties/railties.gemspec
index 76de2b4639..2df303750c 100644
--- a/railties/railties.gemspec
+++ b/railties/railties.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/railties/test/abstract_unit.rb b/railties/test/abstract_unit.rb
index e4b2d0457d..2d4c7a0f0b 100644
--- a/railties/test/abstract_unit.rb
+++ b/railties/test/abstract_unit.rb
@@ -12,7 +12,7 @@ require "rails/all"
 
 module TestApp
   class Application < Rails::Application
-    config.root = File.dirname(__FILE__)
+    config.root = __dir__
     secrets.secret_key_base = "b3c631c314c0bbca50c1b2843150fe33"
   end
 end
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 07c6afed7f..06767167a9 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -1407,6 +1407,40 @@ module ApplicationTests
       assert_match "config/database", err.message
     end
 
+    test "loads database.yml using shared keys" do
+      app_file "config/database.yml", <<-YAML
+        shared:
+          username: bobby
+          adapter: sqlite3
+
+        development:
+          database: 'dev_db'
+      YAML
+
+      app "development"
+
+      ar_config = Rails.application.config.database_configuration
+      assert_equal "sqlite3", ar_config["development"]["adapter"]
+      assert_equal "bobby",   ar_config["development"]["username"]
+      assert_equal "dev_db",  ar_config["development"]["database"]
+    end
+
+    test "loads database.yml using shared keys for undefined environments" do
+      app_file "config/database.yml", <<-YAML
+        shared:
+          username: bobby
+          adapter: sqlite3
+          database: 'dev_db'
+      YAML
+
+      app "development"
+
+      ar_config = Rails.application.config.database_configuration
+      assert_equal "sqlite3", ar_config["development"]["adapter"]
+      assert_equal "bobby",   ar_config["development"]["username"]
+      assert_equal "dev_db",  ar_config["development"]["database"]
+    end
+
     test "config.action_mailer.show_previews defaults to true in development" do
       app "development"
 
diff --git a/railties/test/application/console_test.rb b/railties/test/application/console_test.rb
index 72f340df34..057d473870 100644
--- a/railties/test/application/console_test.rb
+++ b/railties/test/application/console_test.rb
@@ -136,9 +136,9 @@ class FullStackConsoleTest < ActiveSupport::TestCase
     assert_output "> "
   end
 
-  def spawn_console
+  def spawn_console(options)
     Process.spawn(
-      "#{app_path}/bin/rails console --sandbox",
+      "#{app_path}/bin/rails console #{options}",
       in: @slave, out: @slave, err: @slave
     )
 
@@ -146,18 +146,26 @@ class FullStackConsoleTest < ActiveSupport::TestCase
   end
 
   def test_sandbox
-    spawn_console
+    spawn_console("--sandbox")
 
     write_prompt "Post.count", "=> 0"
     write_prompt "Post.create"
     write_prompt "Post.count", "=> 1"
     @master.puts "quit"
 
-    spawn_console
+    spawn_console("--sandbox")
 
     write_prompt "Post.count", "=> 0"
     write_prompt "Post.transaction { Post.create; raise }"
     write_prompt "Post.count", "=> 0"
     @master.puts "quit"
   end
+
+  def test_environment_option_and_irb_option
+    spawn_console("test -- --verbose")
+
+    write_prompt "a = 1", "a = 1"
+    write_prompt "puts Rails.env", "puts Rails.env\r\ntest"
+    @master.puts "quit"
+  end
 end
diff --git a/railties/test/application/current_attributes_integration_test.rb b/railties/test/application/current_attributes_integration_test.rb
new file mode 100644
index 0000000000..5653ec0be1
--- /dev/null
+++ b/railties/test/application/current_attributes_integration_test.rb
@@ -0,0 +1,84 @@
+require "isolation/abstract_unit"
+require "rack/test"
+
+class CurrentAttributesIntegrationTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation
+  include Rack::Test::Methods
+
+  setup do
+    build_app
+
+    app_file "app/models/current.rb", <<-RUBY
+      class Current < ActiveSupport::CurrentAttributes
+        attribute :customer
+
+        resets { Time.zone = "UTC" }
+
+        def customer=(customer)
+          super
+          Time.zone = customer.try(:time_zone)
+        end
+      end
+    RUBY
+
+    app_file "app/models/customer.rb", <<-RUBY
+      class Customer < Struct.new(:name)
+        def time_zone
+          "Copenhagen"
+        end
+      end
+    RUBY
+
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+        get "/customers/:action", controller: :customers
+      end
+    RUBY
+
+    app_file "app/controllers/customers_controller.rb", <<-RUBY
+      class CustomersController < ApplicationController
+        def set_current_customer
+          Current.customer = Customer.new("david")
+          render :index
+        end
+
+        def set_no_customer
+          render :index
+        end
+      end
+    RUBY
+
+    app_file "app/views/customers/index.html.erb", <<-RUBY
+      <%= Current.customer.try(:name) || 'noone' %>,<%= Time.zone.name %>
+    RUBY
+
+    require "#{app_path}/config/environment"
+  end
+
+  teardown :teardown_app
+
+  test "current customer is assigned and cleared" do
+    get "/customers/set_current_customer"
+    assert_equal 200, last_response.status
+    assert_match(/david,Copenhagen/, last_response.body)
+
+    get "/customers/set_no_customer"
+    assert_equal 200, last_response.status
+    assert_match(/noone,UTC/, last_response.body)
+  end
+
+  test "resets after execution" do
+    assert_nil Current.customer
+    assert_equal "UTC", Time.zone.name
+
+    Rails.application.executor.wrap do
+      Current.customer = Customer.new("david")
+
+      assert_equal "david", Current.customer.name
+      assert_equal "Copenhagen", Time.zone.name
+    end
+
+    assert_nil Current.customer
+    assert_equal "UTC", Time.zone.name
+  end
+end
diff --git a/railties/test/application/middleware/session_test.rb b/railties/test/application/middleware/session_test.rb
index 959a629ede..a14ea589ed 100644
--- a/railties/test/application/middleware/session_test.rb
+++ b/railties/test/application/middleware/session_test.rb
@@ -162,6 +162,11 @@ module ApplicationTests
         end
       RUBY
 
+      add_to_config <<-RUBY
+        # Enable AEAD cookies
+        config.action_dispatch.use_authenticated_cookie_encryption = true
+      RUBY
+
       require "#{app_path}/config/environment"
 
       get "/foo/write_session"
@@ -171,9 +176,9 @@ module ApplicationTests
       get "/foo/read_encrypted_cookie"
       assert_equal "1", last_response.body
 
-      secret = app.key_generator.generate_key("encrypted cookie")
-      sign_secret = app.key_generator.generate_key("signed encrypted cookie")
-      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret)
+      cipher = "aes-256-gcm"
+      secret = app.key_generator.generate_key("authenticated encrypted cookie")
+      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len(cipher)], cipher: cipher)
 
       get "/foo/read_raw_cookie"
       assert_equal 1, encryptor.decrypt_and_verify(last_response.body)["foo"]
@@ -209,6 +214,9 @@ module ApplicationTests
 
       add_to_config <<-RUBY
         secrets.secret_token = "3b7cd727ee24e8444053437c36cc66c4"
+
+        # Enable AEAD cookies
+        config.action_dispatch.use_authenticated_cookie_encryption = true
       RUBY
 
       require "#{app_path}/config/environment"
@@ -220,9 +228,9 @@ module ApplicationTests
       get "/foo/read_encrypted_cookie"
       assert_equal "1", last_response.body
 
-      secret = app.key_generator.generate_key("encrypted cookie")
-      sign_secret = app.key_generator.generate_key("signed encrypted cookie")
-      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret)
+      cipher = "aes-256-gcm"
+      secret = app.key_generator.generate_key("authenticated encrypted cookie")
+      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len(cipher)], cipher: cipher)
 
       get "/foo/read_raw_cookie"
       assert_equal 1, encryptor.decrypt_and_verify(last_response.body)["foo"]
@@ -264,6 +272,73 @@ module ApplicationTests
 
       add_to_config <<-RUBY
         secrets.secret_token = "3b7cd727ee24e8444053437c36cc66c4"
+
+        # Enable AEAD cookies
+        config.action_dispatch.use_authenticated_cookie_encryption = true
+      RUBY
+
+      require "#{app_path}/config/environment"
+
+      get "/foo/write_raw_session"
+      get "/foo/read_session"
+      assert_equal "1", last_response.body
+
+      get "/foo/write_session"
+      get "/foo/read_session"
+      assert_equal "2", last_response.body
+
+      get "/foo/read_encrypted_cookie"
+      assert_equal "2", last_response.body
+
+      cipher = "aes-256-gcm"
+      secret = app.key_generator.generate_key("authenticated encrypted cookie")
+      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len(cipher)], cipher: cipher)
+
+      get "/foo/read_raw_cookie"
+      assert_equal 2, encryptor.decrypt_and_verify(last_response.body)["foo"]
+    end
+
+    test "session upgrading from AES-CBC-HMAC encryption to AES-GCM encryption" do
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          get ':controller(/:action)'
+        end
+      RUBY
+
+      controller :foo, <<-RUBY
+        class FooController < ActionController::Base
+          def write_raw_session
+            # AES-256-CBC with SHA1 HMAC
+            # {"session_id"=>"1965d95720fffc123941bdfb7d2e6870", "foo"=>1}
+            cookies[:_myapp_session] = "TlgrdS85aUpDd1R2cDlPWlR6K0FJeGExckwySjZ2Z0pkR3d2QnRObGxZT25aalJWYWVvbFVLcHF4d0VQVDdSaFF2QjFPbG9MVjJzeWp3YjcyRUlKUUU2ZlR4bXlSNG9ZUkJPRUtld0E3dVU9LS0xNDZXbGpRZ3NjdW43N2haUEZJSUNRPT0=--3639b5ce54c09495cfeaae928cd5634e0c4b2e96"
+            head :ok
+          end
+
+          def write_session
+            session[:foo] = session[:foo] + 1
+            head :ok
+          end
+
+          def read_session
+            render plain: session[:foo]
+          end
+
+          def read_encrypted_cookie
+            render plain: cookies.encrypted[:_myapp_session]['foo']
+          end
+
+          def read_raw_cookie
+            render plain: cookies[:_myapp_session]
+          end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        # Use a static key
+        secrets.secret_key_base = "known key base"
+
+        # Enable AEAD cookies
+        config.action_dispatch.use_authenticated_cookie_encryption = true
       RUBY
 
       require "#{app_path}/config/environment"
@@ -279,9 +354,9 @@ module ApplicationTests
       get "/foo/read_encrypted_cookie"
       assert_equal "2", last_response.body
 
-      secret = app.key_generator.generate_key("encrypted cookie")
-      sign_secret = app.key_generator.generate_key("signed encrypted cookie")
-      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret)
+      cipher = "aes-256-gcm"
+      secret = app.key_generator.generate_key("authenticated encrypted cookie")
+      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len(cipher)], cipher: cipher)
 
       get "/foo/read_raw_cookie"
       assert_equal 2, encryptor.decrypt_and_verify(last_response.body)["foo"]
diff --git a/railties/test/application/per_request_digest_cache_test.rb b/railties/test/application/per_request_digest_cache_test.rb
index 6c003e9bcc..6e6996a6ba 100644
--- a/railties/test/application/per_request_digest_cache_test.rb
+++ b/railties/test/application/per_request_digest_cache_test.rb
@@ -18,6 +18,10 @@ class PerRequestDigestCacheTest < ActiveSupport::TestCase
       class Customer < Struct.new(:name, :id)
         extend ActiveModel::Naming
         include ActiveModel::Conversion
+
+        def cache_key
+          [ name, id ].join("/")
+        end
       end
     RUBY
 
diff --git a/railties/test/application/rake/migrations_test.rb b/railties/test/application/rake/migrations_test.rb
index 2c9770e147..51dfe2ef98 100644
--- a/railties/test/application/rake/migrations_test.rb
+++ b/railties/test/application/rake/migrations_test.rb
@@ -48,8 +48,14 @@ module ApplicationTests
           output = `bin/rails db:migrate:up VERSION= 2>&1`
           assert_match(/VERSION is required/, output)
 
+          output = `bin/rails db:migrate:up 2>&1`
+          assert_match(/VERSION is required/, output)
+
           output = `bin/rails db:migrate:down VERSION= 2>&1`
           assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+
+          output = `bin/rails db:migrate:down 2>&1`
+          assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
         end
       end
 
diff --git a/railties/test/application/test_runner_test.rb b/railties/test/application/test_runner_test.rb
index 23b259b503..8e0712fca2 100644
--- a/railties/test/application/test_runner_test.rb
+++ b/railties/test/application/test_runner_test.rb
@@ -469,7 +469,7 @@ module ApplicationTests
     def test_run_app_without_rails_loaded
       # Simulate a real Rails app boot.
       app_file "config/boot.rb", <<-RUBY
-        ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
+        ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 
         require 'bundler/setup' # Set up gems listed in the Gemfile.
       RUBY
diff --git a/railties/test/code_statistics_calculator_test.rb b/railties/test/code_statistics_calculator_test.rb
index 1bd4225f34..25a8a40d27 100644
--- a/railties/test/code_statistics_calculator_test.rb
+++ b/railties/test/code_statistics_calculator_test.rb
@@ -317,7 +317,7 @@ class Animal
 
   private
     def temp_file(name, content)
-      dir = File.expand_path "../fixtures/tmp", __FILE__
+      dir = File.expand_path "fixtures/tmp", __dir__
       path = "#{dir}/#{name}"
 
       FileUtils.mkdir_p dir
diff --git a/railties/test/code_statistics_test.rb b/railties/test/code_statistics_test.rb
index 965b6eeb79..e6e3943117 100644
--- a/railties/test/code_statistics_test.rb
+++ b/railties/test/code_statistics_test.rb
@@ -3,7 +3,7 @@ require "rails/code_statistics"
 
 class CodeStatisticsTest < ActiveSupport::TestCase
   def setup
-    @tmp_path = File.expand_path(File.join(File.dirname(__FILE__), "fixtures", "tmp"))
+    @tmp_path = File.expand_path("fixtures/tmp", __dir__)
     @dir_js   = File.join(@tmp_path, "lib.js")
     FileUtils.mkdir_p(@dir_js)
   end
diff --git a/railties/test/commands/secrets_test.rb b/railties/test/commands/secrets_test.rb
index 00b0343397..fb8fd2325e 100644
--- a/railties/test/commands/secrets_test.rb
+++ b/railties/test/commands/secrets_test.rb
@@ -18,7 +18,8 @@ class Rails::Command::SecretsCommandTest < ActiveSupport::TestCase
   end
 
   test "edit secrets" do
-    run_setup_command
+    # Runs setup before first edit.
+    assert_match(/Adding config\/secrets\.yml\.key to store the encryption key/, run_edit_command)
 
     # Run twice to ensure encrypted secrets can be reread after first edit pass.
     2.times do
@@ -30,8 +31,4 @@ class Rails::Command::SecretsCommandTest < ActiveSupport::TestCase
     def run_edit_command(editor: "cat")
       Dir.chdir(app_path) { `EDITOR="#{editor}" bin/rails secrets:edit` }
     end
-
-    def run_setup_command
-      Dir.chdir(app_path) { `bin/rails secrets:setup` }
-    end
 end
diff --git a/railties/test/commands/server_test.rb b/railties/test/commands/server_test.rb
index 2d1f071969..722323efdc 100644
--- a/railties/test/commands/server_test.rb
+++ b/railties/test/commands/server_test.rb
@@ -140,6 +140,18 @@ class Rails::ServerTest < ActiveSupport::TestCase
   end
 
   def test_argument_precedence_over_environment_variable
+    switch_env "PORT", "1234" do
+      args = ["-p", "5678"]
+      options = parse_arguments(args)
+      assert_equal 5678, options[:Port]
+    end
+
+    switch_env "PORT", "1234" do
+      args = ["-p", "3000"]
+      options = parse_arguments(args)
+      assert_equal 3000, options[:Port]
+    end
+
     switch_env "HOST", "1.2.3.4" do
       args = ["-b", "127.0.0.1"]
       options = parse_arguments(args)
@@ -153,6 +165,12 @@ class Rails::ServerTest < ActiveSupport::TestCase
 
     server_options = parse_arguments(["--port", 3001])
     assert_equal [:Port], server_options[:user_supplied_options]
+
+    server_options = parse_arguments(["-p3001", "-C", "--binding", "127.0.0.1"])
+    assert_equal [:Port, :Host, :caching], server_options[:user_supplied_options]
+
+    server_options = parse_arguments(["--port=3001"])
+    assert_equal [:Port], server_options[:user_supplied_options]
   end
 
   def test_default_options
diff --git a/railties/test/fixtures/lib/generators/usage_template/usage_template_generator.rb b/railties/test/fixtures/lib/generators/usage_template/usage_template_generator.rb
index 21b0ff6c28..701515440a 100644
--- a/railties/test/fixtures/lib/generators/usage_template/usage_template_generator.rb
+++ b/railties/test/fixtures/lib/generators/usage_template/usage_template_generator.rb
@@ -1,5 +1,5 @@
 require "rails/generators"
 
 class UsageTemplateGenerator < Rails::Generators::Base
-  source_root File.expand_path("templates", File.dirname(__FILE__))
+  source_root File.expand_path("templates", __dir__)
 end
diff --git a/railties/test/generators/api_app_generator_test.rb b/railties/test/generators/api_app_generator_test.rb
index 2edb39c8e8..a19e0f0dd8 100644
--- a/railties/test/generators/api_app_generator_test.rb
+++ b/railties/test/generators/api_app_generator_test.rb
@@ -70,7 +70,6 @@ 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/new_framework_defaults_5_1.rb"
   end
 
   def test_app_update_does_not_generate_unnecessary_bin_files
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index 8a51beb380..31a5efb1b7 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -157,7 +157,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
   end
 
   def test_new_application_doesnt_need_defaults
-    assert_no_file "config/initializers/new_framework_defaults_5_1.rb"
+    assert_no_file "config/initializers/new_framework_defaults_5_2.rb"
   end
 
   def test_new_application_load_defaults
@@ -203,14 +203,14 @@ class AppGeneratorTest < Rails::Generators::TestCase
     app_root = File.join(destination_root, "myapp")
     run_generator [app_root]
 
-    assert_no_file "#{app_root}/config/initializers/new_framework_defaults_5_1.rb"
+    assert_no_file "#{app_root}/config/initializers/new_framework_defaults_5_2.rb"
 
     stub_rails_application(app_root) do
       generator = Rails::Generators::AppGenerator.new ["rails"], { update: true }, destination_root: app_root, shell: @shell
       generator.send(:app_const)
       quietly { generator.send(:update_config_files) }
 
-      assert_file "#{app_root}/config/initializers/new_framework_defaults_5_1.rb"
+      assert_file "#{app_root}/config/initializers/new_framework_defaults_5_2.rb"
     end
   end
 
@@ -412,13 +412,6 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
-  def test_generator_if_skip_yarn_is_given
-    run_generator [destination_root, "--skip-yarn"]
-
-    assert_no_file "package.json"
-    assert_no_file "bin/yarn"
-  end
-
   def test_generator_if_skip_action_cable_is_given
     run_generator [destination_root, "--skip-action-cable"]
     assert_file "config/application.rb", /#\s+require\s+["']action_cable\/engine["']/
@@ -524,6 +517,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
   def test_generator_for_yarn_skipped
     run_generator([destination_root, "--skip-yarn"])
     assert_no_file "package.json"
+    assert_no_file "bin/yarn"
 
     assert_file "config/initializers/assets.rb" do |content|
       assert_no_match(/node_modules/, content)
@@ -569,9 +563,9 @@ class AppGeneratorTest < Rails::Generators::TestCase
     run_generator
     assert_file "config/environments/development.rb" do |content|
       if RbConfig::CONFIG["host_os"] =~ /darwin|linux/
-        assert_match(/^\s*config.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
+        assert_match(/^\s*config\.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
       else
-        assert_match(/^\s*# config.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
+        assert_match(/^\s*# config\.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
       end
     end
   end
@@ -639,7 +633,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
     assert_file "Gemfile" do |content|
       assert_match(/gem 'web-console',\s+github: 'rails\/web-console'/, content)
-      assert_no_match(/\Agem 'web-console', '>= 3.3.0'\z/, content)
+      assert_no_match(/\Agem 'web-console', '>= 3\.3\.0'\z/, content)
     end
   end
 
@@ -648,7 +642,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
     assert_file "Gemfile" do |content|
       assert_match(/gem 'web-console',\s+github: 'rails\/web-console'/, content)
-      assert_no_match(/\Agem 'web-console', '>= 3.3.0'\z/, content)
+      assert_no_match(/\Agem 'web-console', '>= 3\.3\.0'\z/, content)
     end
   end
 
@@ -787,7 +781,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
   def test_psych_gem
     run_generator
-    gem_regex = /gem 'psych',\s+'~> 2.0',\s+platforms: :rbx/
+    gem_regex = /gem 'psych',\s+'~> 2\.0',\s+platforms: :rbx/
 
     assert_file "Gemfile" do |content|
       if defined?(Rubinius)
@@ -870,7 +864,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
       assert_gem "spring-watcher-listen"
 
       assert_file "config/environments/development.rb" do |content|
-        assert_match(/^\s*config.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
+        assert_match(/^\s*config\.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
       end
     end
 
@@ -880,7 +874,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
       end
 
       assert_file "config/environments/development.rb" do |content|
-        assert_match(/^\s*# config.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
+        assert_match(/^\s*# config\.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
       end
     end
 
diff --git a/railties/test/generators/channel_generator_test.rb b/railties/test/generators/channel_generator_test.rb
index a1d54200ba..af68a9c49f 100644
--- a/railties/test/generators/channel_generator_test.rb
+++ b/railties/test/generators/channel_generator_test.rb
@@ -25,7 +25,7 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/assets/javascripts/channels/chat.js" do |channel|
-      assert_match(/App.chat = App.cable.subscriptions.create\("ChatChannel/, channel)
+      assert_match(/App\.chat = App\.cable\.subscriptions\.create\("ChatChannel/, channel)
     end
   end
 
@@ -39,7 +39,7 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/assets/javascripts/channels/chat.js" do |channel|
-      assert_match(/App.chat = App.cable.subscriptions.create\("ChatChannel/, channel)
+      assert_match(/App\.chat = App\.cable\.subscriptions\.create\("ChatChannel/, channel)
       assert_match(/,\n\n  speak/, channel)
       assert_match(/,\n\n  mute: function\(\) \{\n    return this\.perform\('mute'\);\n  \}\n\}\);/, channel)
     end
diff --git a/railties/test/generators/create_migration_test.rb b/railties/test/generators/create_migration_test.rb
index ddd40e4d02..c7b0237f02 100644
--- a/railties/test/generators/create_migration_test.rb
+++ b/railties/test/generators/create_migration_test.rb
@@ -46,7 +46,7 @@ class CreateMigrationTest < Rails::Generators::TestCase
   def test_invoke
     create_migration
 
-    assert_match(/create  db\/migrate\/1_create_articles.rb\n/, invoke!)
+    assert_match(/create  db\/migrate\/1_create_articles\.rb\n/, invoke!)
     assert_file @migration.destination
   end
 
@@ -67,7 +67,7 @@ class CreateMigrationTest < Rails::Generators::TestCase
     migration_exists!
     create_migration
 
-    assert_match(/identical  db\/migrate\/1_create_articles.rb\n/, invoke!)
+    assert_match(/identical  db\/migrate\/1_create_articles\.rb\n/, invoke!)
     assert @migration.identical?
   end
 
@@ -84,8 +84,8 @@ class CreateMigrationTest < Rails::Generators::TestCase
     create_migration(dest, force: true) { "different content" }
 
     stdout = invoke!
-    assert_match(/remove  db\/migrate\/1_migration.rb\n/, stdout)
-    assert_match(/create  db\/migrate\/2_migration.rb\n/, stdout)
+    assert_match(/remove  db\/migrate\/1_migration\.rb\n/, stdout)
+    assert_match(/create  db\/migrate\/2_migration\.rb\n/, stdout)
     assert_file @migration.destination
     assert_no_file @existing_migration.destination
   end
@@ -97,8 +97,8 @@ class CreateMigrationTest < Rails::Generators::TestCase
     end
 
     stdout = invoke!
-    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, stdout)
-    assert_match(/create  db\/migrate\/2_create_articles.rb\n/, stdout)
+    assert_match(/remove  db\/migrate\/1_create_articles\.rb\n/, stdout)
+    assert_match(/create  db\/migrate\/2_create_articles\.rb\n/, stdout)
     assert_no_file @migration.destination
   end
 
@@ -106,7 +106,7 @@ class CreateMigrationTest < Rails::Generators::TestCase
     migration_exists!
     create_migration(default_destination_path, {}, skip: true) { "different content" }
 
-    assert_match(/skip  db\/migrate\/2_create_articles.rb\n/, invoke!)
+    assert_match(/skip  db\/migrate\/2_create_articles\.rb\n/, invoke!)
     assert_no_file @migration.destination
   end
 
@@ -114,7 +114,7 @@ class CreateMigrationTest < Rails::Generators::TestCase
     migration_exists!
     create_migration
 
-    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, revoke!)
+    assert_match(/remove  db\/migrate\/1_create_articles\.rb\n/, revoke!)
     assert_no_file @existing_migration.destination
   end
 
@@ -122,13 +122,13 @@ class CreateMigrationTest < Rails::Generators::TestCase
     migration_exists!
     create_migration(default_destination_path, {}, pretend: true)
 
-    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, revoke!)
+    assert_match(/remove  db\/migrate\/1_create_articles\.rb\n/, revoke!)
     assert_file @existing_migration.destination
   end
 
   def test_revoke_when_no_exists
     create_migration
 
-    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, revoke!)
+    assert_match(/remove  db\/migrate\/1_create_articles\.rb\n/, revoke!)
   end
 end
diff --git a/railties/test/generators/generators_test_helper.rb b/railties/test/generators/generators_test_helper.rb
index 2cdddc8713..5fb331e197 100644
--- a/railties/test/generators/generators_test_helper.rb
+++ b/railties/test/generators/generators_test_helper.rb
@@ -9,7 +9,7 @@ module Rails
   class << self
     remove_possible_method :root
     def root
-      @root ||= Pathname.new(File.expand_path("../../fixtures", __FILE__))
+      @root ||= Pathname.new(File.expand_path("../fixtures", __dir__))
     end
   end
 end
@@ -41,7 +41,7 @@ module GeneratorsTestHelper
   end
 
   def copy_routes
-    routes = File.expand_path("../../../lib/rails/generators/rails/app/templates/config/routes.rb", __FILE__)
+    routes = File.expand_path("../../lib/rails/generators/rails/app/templates/config/routes.rb", __dir__)
     destination = File.join(destination_root, "config")
     FileUtils.mkdir_p(destination)
     FileUtils.cp routes, destination
diff --git a/railties/test/generators/mailer_generator_test.rb b/railties/test/generators/mailer_generator_test.rb
index 7d69d7470d..2ff03ea65e 100644
--- a/railties/test/generators/mailer_generator_test.rb
+++ b/railties/test/generators/mailer_generator_test.rb
@@ -9,13 +9,13 @@ class MailerGeneratorTest < Rails::Generators::TestCase
     run_generator
     assert_file "app/mailers/notifier_mailer.rb" do |mailer|
       assert_match(/class NotifierMailer < ApplicationMailer/, mailer)
-      assert_no_match(/default from: "from@example.com"/, mailer)
+      assert_no_match(/default from: "from@example\.com"/, mailer)
       assert_no_match(/layout :mailer_notifier/, mailer)
     end
 
     assert_file "app/mailers/application_mailer.rb" do |mailer|
       assert_match(/class ApplicationMailer < ActionMailer::Base/, mailer)
-      assert_match(/default from: 'from@example.com'/, mailer)
+      assert_match(/default from: 'from@example\.com'/, mailer)
       assert_match(/layout 'mailer'/, mailer)
     end
   end
@@ -48,11 +48,11 @@ class MailerGeneratorTest < Rails::Generators::TestCase
       assert_match(/class NotifierMailerPreview < ActionMailer::Preview/, preview)
       assert_match(/\# Preview this email at http:\/\/localhost\:3000\/rails\/mailers\/notifier_mailer\/foo/, preview)
       assert_instance_method :foo, preview do |foo|
-        assert_match(/NotifierMailer.foo/, foo)
+        assert_match(/NotifierMailer\.foo/, foo)
       end
       assert_match(/\# Preview this email at http:\/\/localhost\:3000\/rails\/mailers\/notifier_mailer\/bar/, preview)
       assert_instance_method :bar, preview do |bar|
-        assert_match(/NotifierMailer.bar/, bar)
+        assert_match(/NotifierMailer\.bar/, bar)
       end
     end
   end
@@ -137,12 +137,12 @@ class MailerGeneratorTest < Rails::Generators::TestCase
 
     assert_file "app/mailers/notifier_mailer.rb" do |mailer|
       assert_instance_method :foo, mailer do |foo|
-        assert_match(/mail to: "to@example.org"/, foo)
+        assert_match(/mail to: "to@example\.org"/, foo)
         assert_match(/@greeting = "Hi"/, foo)
       end
 
       assert_instance_method :bar, mailer do |bar|
-        assert_match(/mail to: "to@example.org"/, bar)
+        assert_match(/mail to: "to@example\.org"/, bar)
         assert_match(/@greeting = "Hi"/, bar)
       end
     end
diff --git a/railties/test/generators/migration_generator_test.rb b/railties/test/generators/migration_generator_test.rb
index f46278cefe..6fe6e4ca07 100644
--- a/railties/test/generators/migration_generator_test.rb
+++ b/railties/test/generators/migration_generator_test.rb
@@ -204,8 +204,8 @@ class MigrationGeneratorTest < Rails::Generators::TestCase
     assert_migration "db/migrate/#{migration}.rb" do |content|
       assert_method :change, content do |change|
         assert_match(/create_join_table :artists, :musics/, change)
-        assert_match(/# t.index \[:artist_id, :music_id\]/, change)
-        assert_match(/  t.index \[:music_id, :artist_id\], unique: true/, change)
+        assert_match(/# t\.index \[:artist_id, :music_id\]/, change)
+        assert_match(/  t\.index \[:music_id, :artist_id\], unique: true/, change)
       end
     end
   end
@@ -265,8 +265,8 @@ class MigrationGeneratorTest < Rails::Generators::TestCase
       assert_migration "db/migrate/#{migration}.rb" do |content|
         assert_method :change, content do |change|
           assert_match(/create_join_table :artist, :music/, change)
-          assert_match(/# t.index \[:artist_id, :music_id\]/, change)
-          assert_match(/  t.index \[:music_id, :artist_id\], unique: true/, change)
+          assert_match(/# t\.index \[:artist_id, :music_id\]/, change)
+          assert_match(/  t\.index \[:music_id, :artist_id\], unique: true/, change)
         end
       end
     end
diff --git a/railties/test/generators/model_generator_test.rb b/railties/test/generators/model_generator_test.rb
index 99490af3a9..f41969fc46 100644
--- a/railties/test/generators/model_generator_test.rb
+++ b/railties/test/generators/model_generator_test.rb
@@ -10,7 +10,7 @@ class ModelGeneratorTest < Rails::Generators::TestCase
     run_generator
     assert_file "app/models/application_record.rb" do |record|
       assert_match(/class ApplicationRecord < ActiveRecord::Base/, record)
-      assert_match(/self.abstract_class = true/, record)
+      assert_match(/self\.abstract_class = true/, record)
     end
   end
 
@@ -253,7 +253,7 @@ class ModelGeneratorTest < Rails::Generators::TestCase
 
   def test_migration_with_timestamps
     run_generator
-    assert_migration "db/migrate/create_accounts.rb", /t.timestamps/
+    assert_migration "db/migrate/create_accounts.rb", /t\.timestamps/
   end
 
   def test_migration_timestamps_are_skipped
@@ -261,7 +261,7 @@ class ModelGeneratorTest < Rails::Generators::TestCase
 
     assert_migration "db/migrate/create_accounts.rb" do |m|
       assert_method :change, m do |up|
-        assert_no_match(/t.timestamps/, up)
+        assert_no_match(/t\.timestamps/, up)
       end
     end
   end
@@ -269,19 +269,19 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_migration_is_skipped_with_skip_option
     run_generator
     output = run_generator ["Account", "--skip"]
-    assert_match %r{skip\s+db/migrate/\d+_create_accounts.rb}, output
+    assert_match %r{skip\s+db/migrate/\d+_create_accounts\.rb}, output
   end
 
   def test_migration_is_ignored_as_identical_with_skip_option
     run_generator ["Account"]
     output = run_generator ["Account", "--skip"]
-    assert_match %r{identical\s+db/migrate/\d+_create_accounts.rb}, output
+    assert_match %r{identical\s+db/migrate/\d+_create_accounts\.rb}, output
   end
 
   def test_migration_is_skipped_on_skip_behavior
     run_generator
     output = run_generator ["Account"], behavior: :skip
-    assert_match %r{skip\s+db/migrate/\d+_create_accounts.rb}, output
+    assert_match %r{skip\s+db/migrate/\d+_create_accounts\.rb}, output
   end
 
   def test_migration_error_is_not_shown_on_revoke
diff --git a/railties/test/generators/plugin_generator_test.rb b/railties/test/generators/plugin_generator_test.rb
index afb37b6a99..af16a2641a 100644
--- a/railties/test/generators/plugin_generator_test.rb
+++ b/railties/test/generators/plugin_generator_test.rb
@@ -48,7 +48,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     run_generator [File.join(destination_root, "hyphenated-name")]
     assert_no_file "hyphenated-name/lib/hyphenated-name.rb"
     assert_no_file "hyphenated-name/lib/hyphenated_name.rb"
-    assert_file "hyphenated-name/lib/hyphenated/name.rb", /module Hyphenated\n  module Name\n    # Your code goes here...\n  end\nend/
+    assert_file "hyphenated-name/lib/hyphenated/name.rb", /module Hyphenated\n  module Name\n    # Your code goes here\.\.\.\n  end\nend/
   end
 
   def test_correct_file_in_lib_folder_of_camelcase_plugin_name
@@ -152,7 +152,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     run_generator [destination_root, "--skip-active-record"]
 
     assert_file "bukkits.gemspec" do |contents|
-      assert_no_match(/s.add_development_dependency "sqlite3"/, contents)
+      assert_no_match(/s\.add_development_dependency "sqlite3"/, contents)
     end
   end
 
@@ -294,7 +294,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "hyphenated-name/config/routes.rb",              /Rails.application.routes.draw do/
     assert_file "hyphenated-name/lib/hyphenated/name/engine.rb", /module Hyphenated\n  module Name\n    class Engine < ::Rails::Engine\n    end\n  end\nend/
     assert_file "hyphenated-name/lib/hyphenated/name.rb",        /require "hyphenated\/name\/engine"/
-    assert_file "hyphenated-name/bin/rails",                     /\.\.\/\.\.\/lib\/hyphenated\/name\/engine/
+    assert_file "hyphenated-name/bin/rails",                     /\.\.\/lib\/hyphenated\/name\/engine/
   end
 
   def test_creating_engine_with_hyphenated_and_underscored_name_in_full_mode
@@ -308,14 +308,14 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "my_hyphenated-name/app/helpers"
     assert_file "my_hyphenated-name/app/mailers"
     assert_file "my_hyphenated-name/bin/rails"
-    assert_file "my_hyphenated-name/config/routes.rb",              /Rails.application.routes.draw do/
+    assert_file "my_hyphenated-name/config/routes.rb",              /Rails\.application\.routes\.draw do/
     assert_file "my_hyphenated-name/lib/my_hyphenated/name/engine.rb", /module MyHyphenated\n  module Name\n    class Engine < ::Rails::Engine\n    end\n  end\nend/
     assert_file "my_hyphenated-name/lib/my_hyphenated/name.rb",        /require "my_hyphenated\/name\/engine"/
-    assert_file "my_hyphenated-name/bin/rails",                     /\.\.\/\.\.\/lib\/my_hyphenated\/name\/engine/
+    assert_file "my_hyphenated-name/bin/rails",                     /\.\.\/lib\/my_hyphenated\/name\/engine/
   end
 
   def test_being_quiet_while_creating_dummy_application
-    assert_no_match(/create\s+config\/application.rb/, run_generator)
+    assert_no_match(/create\s+config\/application\.rb/, run_generator)
   end
 
   def test_create_mountable_application_with_mountable_option
@@ -323,13 +323,13 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "app/assets/javascripts/bukkits"
     assert_file "app/assets/stylesheets/bukkits"
     assert_file "app/assets/images/bukkits"
-    assert_file "config/routes.rb", /Bukkits::Engine.routes.draw do/
+    assert_file "config/routes.rb", /Bukkits::Engine\.routes\.draw do/
     assert_file "lib/bukkits/engine.rb", /isolate_namespace Bukkits/
     assert_file "test/dummy/config/routes.rb", /mount Bukkits::Engine => "\/bukkits"/
     assert_file "app/controllers/bukkits/application_controller.rb", /module Bukkits\n  class ApplicationController < ActionController::Base/
     assert_file "app/models/bukkits/application_record.rb", /module Bukkits\n  class ApplicationRecord < ActiveRecord::Base/
     assert_file "app/jobs/bukkits/application_job.rb", /module Bukkits\n  class ApplicationJob < ActiveJob::Base/
-    assert_file "app/mailers/bukkits/application_mailer.rb", /module Bukkits\n  class ApplicationMailer < ActionMailer::Base\n    default from: 'from@example.com'\n    layout 'mailer'\n/
+    assert_file "app/mailers/bukkits/application_mailer.rb", /module Bukkits\n  class ApplicationMailer < ActionMailer::Base\n    default from: 'from@example\.com'\n    layout 'mailer'\n/
     assert_file "app/helpers/bukkits/application_helper.rb", /module Bukkits\n  module ApplicationHelper/
     assert_file "app/views/layouts/bukkits/application.html.erb" do |contents|
       assert_match "<title>Bukkits</title>", contents
@@ -350,15 +350,15 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "hyphenated-name/app/assets/javascripts/hyphenated/name"
     assert_file "hyphenated-name/app/assets/stylesheets/hyphenated/name"
     assert_file "hyphenated-name/app/assets/images/hyphenated/name"
-    assert_file "hyphenated-name/config/routes.rb",                                          /Hyphenated::Name::Engine.routes.draw do/
-    assert_file "hyphenated-name/lib/hyphenated/name/version.rb",                            /module Hyphenated\n  module Name\n    VERSION = '0.1.0'\n  end\nend/
+    assert_file "hyphenated-name/config/routes.rb",                                          /Hyphenated::Name::Engine\.routes\.draw do/
+    assert_file "hyphenated-name/lib/hyphenated/name/version.rb",                            /module Hyphenated\n  module Name\n    VERSION = '0\.1\.0'\n  end\nend/
     assert_file "hyphenated-name/lib/hyphenated/name/engine.rb",                             /module Hyphenated\n  module Name\n    class Engine < ::Rails::Engine\n      isolate_namespace Hyphenated::Name\n    end\n  end\nend/
     assert_file "hyphenated-name/lib/hyphenated/name.rb",                                    /require "hyphenated\/name\/engine"/
     assert_file "hyphenated-name/test/dummy/config/routes.rb",                               /mount Hyphenated::Name::Engine => "\/hyphenated-name"/
     assert_file "hyphenated-name/app/controllers/hyphenated/name/application_controller.rb", /module Hyphenated\n  module Name\n    class ApplicationController < ActionController::Base\n      protect_from_forgery with: :exception\n    end\n  end\nend\n/
     assert_file "hyphenated-name/app/models/hyphenated/name/application_record.rb",          /module Hyphenated\n  module Name\n    class ApplicationRecord < ActiveRecord::Base\n      self\.abstract_class = true\n    end\n  end\nend/
     assert_file "hyphenated-name/app/jobs/hyphenated/name/application_job.rb",               /module Hyphenated\n  module Name\n    class ApplicationJob < ActiveJob::Base/
-    assert_file "hyphenated-name/app/mailers/hyphenated/name/application_mailer.rb",         /module Hyphenated\n  module Name\n    class ApplicationMailer < ActionMailer::Base\n      default from: 'from@example.com'\n      layout 'mailer'\n    end\n  end\nend/
+    assert_file "hyphenated-name/app/mailers/hyphenated/name/application_mailer.rb",         /module Hyphenated\n  module Name\n    class ApplicationMailer < ActionMailer::Base\n      default from: 'from@example\.com'\n      layout 'mailer'\n    end\n  end\nend/
     assert_file "hyphenated-name/app/helpers/hyphenated/name/application_helper.rb",         /module Hyphenated\n  module Name\n    module ApplicationHelper\n    end\n  end\nend/
     assert_file "hyphenated-name/app/views/layouts/hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>Hyphenated name</title>", contents
@@ -372,15 +372,15 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "my_hyphenated-name/app/assets/javascripts/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/assets/stylesheets/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/assets/images/my_hyphenated/name"
-    assert_file "my_hyphenated-name/config/routes.rb",                                             /MyHyphenated::Name::Engine.routes.draw do/
-    assert_file "my_hyphenated-name/lib/my_hyphenated/name/version.rb",                            /module MyHyphenated\n  module Name\n    VERSION = '0.1.0'\n  end\nend/
+    assert_file "my_hyphenated-name/config/routes.rb",                                             /MyHyphenated::Name::Engine\.routes\.draw do/
+    assert_file "my_hyphenated-name/lib/my_hyphenated/name/version.rb",                            /module MyHyphenated\n  module Name\n    VERSION = '0\.1\.0'\n  end\nend/
     assert_file "my_hyphenated-name/lib/my_hyphenated/name/engine.rb",                             /module MyHyphenated\n  module Name\n    class Engine < ::Rails::Engine\n      isolate_namespace MyHyphenated::Name\n    end\n  end\nend/
     assert_file "my_hyphenated-name/lib/my_hyphenated/name.rb",                                    /require "my_hyphenated\/name\/engine"/
     assert_file "my_hyphenated-name/test/dummy/config/routes.rb",                                  /mount MyHyphenated::Name::Engine => "\/my_hyphenated-name"/
     assert_file "my_hyphenated-name/app/controllers/my_hyphenated/name/application_controller.rb", /module MyHyphenated\n  module Name\n    class ApplicationController < ActionController::Base\n      protect_from_forgery with: :exception\n    end\n  end\nend\n/
     assert_file "my_hyphenated-name/app/models/my_hyphenated/name/application_record.rb",          /module MyHyphenated\n  module Name\n    class ApplicationRecord < ActiveRecord::Base\n      self\.abstract_class = true\n    end\n  end\nend/
     assert_file "my_hyphenated-name/app/jobs/my_hyphenated/name/application_job.rb",               /module MyHyphenated\n  module Name\n    class ApplicationJob < ActiveJob::Base/
-    assert_file "my_hyphenated-name/app/mailers/my_hyphenated/name/application_mailer.rb",         /module MyHyphenated\n  module Name\n    class ApplicationMailer < ActionMailer::Base\n      default from: 'from@example.com'\n      layout 'mailer'\n    end\n  end\nend/
+    assert_file "my_hyphenated-name/app/mailers/my_hyphenated/name/application_mailer.rb",         /module MyHyphenated\n  module Name\n    class ApplicationMailer < ActionMailer::Base\n      default from: 'from@example\.com'\n      layout 'mailer'\n    end\n  end\nend/
     assert_file "my_hyphenated-name/app/helpers/my_hyphenated/name/application_helper.rb",         /module MyHyphenated\n  module Name\n    module ApplicationHelper\n    end\n  end\nend/
     assert_file "my_hyphenated-name/app/views/layouts/my_hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>My hyphenated name</title>", contents
@@ -394,15 +394,15 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "deep-hyphenated-name/app/assets/javascripts/deep/hyphenated/name"
     assert_file "deep-hyphenated-name/app/assets/stylesheets/deep/hyphenated/name"
     assert_file "deep-hyphenated-name/app/assets/images/deep/hyphenated/name"
-    assert_file "deep-hyphenated-name/config/routes.rb",                                               /Deep::Hyphenated::Name::Engine.routes.draw do/
-    assert_file "deep-hyphenated-name/lib/deep/hyphenated/name/version.rb",                            /module Deep\n  module Hyphenated\n    module Name\n      VERSION = '0.1.0'\n    end\n  end\nend/
+    assert_file "deep-hyphenated-name/config/routes.rb",                                               /Deep::Hyphenated::Name::Engine\.routes\.draw do/
+    assert_file "deep-hyphenated-name/lib/deep/hyphenated/name/version.rb",                            /module Deep\n  module Hyphenated\n    module Name\n      VERSION = '0\.1\.0'\n    end\n  end\nend/
     assert_file "deep-hyphenated-name/lib/deep/hyphenated/name/engine.rb",                             /module Deep\n  module Hyphenated\n    module Name\n      class Engine < ::Rails::Engine\n        isolate_namespace Deep::Hyphenated::Name\n      end\n    end\n  end\nend/
     assert_file "deep-hyphenated-name/lib/deep/hyphenated/name.rb",                                    /require "deep\/hyphenated\/name\/engine"/
     assert_file "deep-hyphenated-name/test/dummy/config/routes.rb",                                    /mount Deep::Hyphenated::Name::Engine => "\/deep-hyphenated-name"/
     assert_file "deep-hyphenated-name/app/controllers/deep/hyphenated/name/application_controller.rb", /module Deep\n  module Hyphenated\n    module Name\n      class ApplicationController < ActionController::Base\n        protect_from_forgery with: :exception\n      end\n    end\n  end\nend\n/
     assert_file "deep-hyphenated-name/app/models/deep/hyphenated/name/application_record.rb",          /module Deep\n  module Hyphenated\n    module Name\n      class ApplicationRecord < ActiveRecord::Base\n        self\.abstract_class = true\n      end\n    end\n  end\nend/
     assert_file "deep-hyphenated-name/app/jobs/deep/hyphenated/name/application_job.rb",               /module Deep\n  module Hyphenated\n    module Name\n      class ApplicationJob < ActiveJob::Base/
-    assert_file "deep-hyphenated-name/app/mailers/deep/hyphenated/name/application_mailer.rb",         /module Deep\n  module Hyphenated\n    module Name\n      class ApplicationMailer < ActionMailer::Base\n        default from: 'from@example.com'\n        layout 'mailer'\n      end\n    end\n  end\nend/
+    assert_file "deep-hyphenated-name/app/mailers/deep/hyphenated/name/application_mailer.rb",         /module Deep\n  module Hyphenated\n    module Name\n      class ApplicationMailer < ActionMailer::Base\n        default from: 'from@example\.com'\n        layout 'mailer'\n      end\n    end\n  end\nend/
     assert_file "deep-hyphenated-name/app/helpers/deep/hyphenated/name/application_helper.rb",         /module Deep\n  module Hyphenated\n    module Name\n      module ApplicationHelper\n      end\n    end\n  end\nend/
     assert_file "deep-hyphenated-name/app/views/layouts/deep/hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>Deep hyphenated name</title>", contents
@@ -413,16 +413,16 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_creating_gemspec
     run_generator
-    assert_file "bukkits.gemspec", /s.name\s+= "bukkits"/
-    assert_file "bukkits.gemspec", /s.files = Dir\["\{app,config,db,lib\}\/\*\*\/\*", "MIT-LICENSE", "Rakefile", "README\.md"\]/
-    assert_file "bukkits.gemspec", /s.version\s+ = Bukkits::VERSION/
+    assert_file "bukkits.gemspec", /s\.name\s+= "bukkits"/
+    assert_file "bukkits.gemspec", /s\.files = Dir\["\{app,config,db,lib\}\/\*\*\/\*", "MIT-LICENSE", "Rakefile", "README\.md"\]/
+    assert_file "bukkits.gemspec", /s\.version\s+ = Bukkits::VERSION/
   end
 
   def test_usage_of_engine_commands
     run_generator [destination_root, "--full"]
-    assert_file "bin/rails", /ENGINE_PATH = File.expand_path\('..\/..\/lib\/bukkits\/engine', __FILE__\)/
-    assert_file "bin/rails", /ENGINE_ROOT = File.expand_path\('..\/..', __FILE__\)/
-    assert_file "bin/rails", %r|APP_PATH = File.expand_path\('../../test/dummy/config/application', __FILE__\)|
+    assert_file "bin/rails", /ENGINE_PATH = File\.expand_path\('\.\.\/lib\/bukkits\/engine', __dir__\)/
+    assert_file "bin/rails", /ENGINE_ROOT = File\.expand_path\('\.\.', __dir__\)/
+    assert_file "bin/rails", %r|APP_PATH = File\.expand_path\('\.\./test/dummy/config/application', __dir__\)|
     assert_file "bin/rails", /require 'rails\/all'/
     assert_file "bin/rails", /require 'rails\/engine\/commands'/
   end
@@ -469,7 +469,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     run_generator
 
     assert_file "test/dummy/config/environments/development.rb" do |contents|
-      assert_match(/^\s*# config.file_watcher = ActiveSupport::EventedFileUpdateChecker/, contents)
+      assert_match(/^\s*# config\.file_watcher = ActiveSupport::EventedFileUpdateChecker/, contents)
     end
   end
 
@@ -687,7 +687,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "#{destination_root}/app/models/bukkits/application_record.rb" do |record|
       assert_match(/module Bukkits/, record)
       assert_match(/class ApplicationRecord < ActiveRecord::Base/, record)
-      assert_match(/self.abstract_class = true/, record)
+      assert_match(/self\.abstract_class = true/, record)
     end
   end
 
@@ -741,7 +741,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     quietly { Rails::Engine::Updater.run(:create_bin_files) }
 
     assert_file "#{destination_root}/bin/rails" do |content|
-      assert_match(%r|APP_PATH = File\.expand_path\('\.\./\.\./test/dummy/config/application', __FILE__\)|, content)
+      assert_match(%r|APP_PATH = File\.expand_path\('\.\./test/dummy/config/application', __dir__\)|, content)
     end
   ensure
     Object.send(:remove_const, "ENGINE_ROOT")
diff --git a/railties/test/generators/shared_generator_tests.rb b/railties/test/generators/shared_generator_tests.rb
index cc9d3629e9..5e75879964 100644
--- a/railties/test/generators/shared_generator_tests.rb
+++ b/railties/test/generators/shared_generator_tests.rb
@@ -45,14 +45,14 @@ module SharedGeneratorTests
     reserved_words = %w[application destroy plugin runner test]
     reserved_words.each do |reserved|
       content = capture(:stderr) { run_generator [File.join(destination_root, reserved)] }
-      assert_match(/Invalid \w+ name #{reserved}. Please give a name which does not match one of the reserved rails words: application, destroy, plugin, runner, test\n/, content)
+      assert_match(/Invalid \w+ name #{reserved}\. Please give a name which does not match one of the reserved rails words: application, destroy, plugin, runner, test\n/, content)
     end
   end
 
   def test_name_raises_an_error_if_name_already_used_constant
     %w{ String Hash Class Module Set Symbol }.each do |ruby_class|
       content = capture(:stderr) { run_generator [File.join(destination_root, ruby_class)] }
-      assert_match(/Invalid \w+ name #{ruby_class}, constant #{ruby_class} is already in use. Please choose another \w+ name.\n/, content)
+      assert_match(/Invalid \w+ name #{ruby_class}, constant #{ruby_class} is already in use\. Please choose another \w+ name\.\n/, content)
     end
   end
 
diff --git a/railties/test/generators/system_test_generator_test.rb b/railties/test/generators/system_test_generator_test.rb
index e8e561ec49..4622360244 100644
--- a/railties/test/generators/system_test_generator_test.rb
+++ b/railties/test/generators/system_test_generator_test.rb
@@ -9,4 +9,9 @@ class SystemTestGeneratorTest < Rails::Generators::TestCase
     run_generator
     assert_file "test/system/users_test.rb", /class UsersTest < ApplicationSystemTestCase/
   end
+
+  def test_namespaced_system_test_skeleton_is_created
+    run_generator %w(admin/user)
+    assert_file "test/system/admin/users_test.rb", /class Admin::UsersTest < ApplicationSystemTestCase/
+  end
 end
diff --git a/railties/test/generators/test_runner_in_engine_test.rb b/railties/test/generators/test_runner_in_engine_test.rb
index 4b5fb3ba3f..680dc2608e 100644
--- a/railties/test/generators/test_runner_in_engine_test.rb
+++ b/railties/test/generators/test_runner_in_engine_test.rb
@@ -17,7 +17,7 @@ class TestRunnerInEngineTest < ActiveSupport::TestCase
     create_test_file "post", pass: false
 
     output = run_test_command("test/post_test.rb")
-    expect = %r{Running:\n\nPostTest\nF\n\nFailure:\nPostTest#test_truth \[[^\]]+test/post_test.rb:6\]:\nwups!\n\nbin/rails test test/post_test.rb:4}
+    expect = %r{Running:\n\nPostTest\nF\n\nFailure:\nPostTest#test_truth \[[^\]]+test/post_test\.rb:6\]:\nwups!\n\nbin/rails test test/post_test\.rb:4}
     assert_match expect, output
   end
 
diff --git a/railties/test/generators_test.rb b/railties/test/generators_test.rb
index c3c16b6f86..b784446535 100644
--- a/railties/test/generators_test.rb
+++ b/railties/test/generators_test.rb
@@ -233,7 +233,7 @@ class GeneratorsTest < Rails::Generators::TestCase
   end
 
   def test_usage_with_embedded_ruby
-    require File.expand_path("fixtures/lib/generators/usage_template/usage_template_generator", File.dirname(__FILE__))
+    require File.expand_path("fixtures/lib/generators/usage_template/usage_template_generator", __dir__)
     output = capture(:stdout) { Rails::Generators.invoke :usage_template, ["--help"] }
     assert_match(/:: 2 ::/, output)
   end
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 2e742a005e..7496b5f84a 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -14,7 +14,7 @@ require "active_support/testing/autorun"
 require "active_support/testing/stream"
 require "active_support/test_case"
 
-RAILS_FRAMEWORK_ROOT = File.expand_path("#{File.dirname(__FILE__)}/../../..")
+RAILS_FRAMEWORK_ROOT = File.expand_path("../../..", __dir__)
 
 # These files do not require any others and are needed
 # to run the tests
diff --git a/railties/test/rails_info_test.rb b/railties/test/rails_info_test.rb
index 9f4c5bb025..383adcc55d 100644
--- a/railties/test/rails_info_test.rb
+++ b/railties/test/rails_info_test.rb
@@ -39,7 +39,7 @@ class InfoTest < ActiveSupport::TestCase
 
   def test_rails_version
     assert_property "Rails version",
-      File.read(File.realpath("../../../RAILS_VERSION", __FILE__)).chomp
+      File.read(File.realpath("../../RAILS_VERSION", __dir__)).chomp
   end
 
   def test_html_includes_middleware
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index 52d691b73b..e382a7a873 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -89,16 +89,16 @@ module RailtiesTest
 
         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_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
 
         output = `bundle exec rake railties:install:migrations`.split("\n")
 
         assert_no_match(/2_create_users/, output.join("\n"))
 
-        bukkits_migration_order = output.index(output.detect { |o| /NOTE: Migration 3_create_sessions.rb from bukkits has been skipped/ =~ o })
+        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
@@ -135,8 +135,8 @@ module RailtiesTest
       Dir.chdir(app_path) do
         output = `bundle exec rake railties:install:migrations`.split("\n")
 
-        assert_match(/Copied migration \d+_create_users.bukkits.rb from bukkits/, output.first)
-        assert_match(/Copied migration \d+_create_blogs.blog_engine.rb from blog_engine/, output.last)
+        assert_match(/Copied migration \d+_create_users\.bukkits\.rb from bukkits/, output.first)
+        assert_match(/Copied migration \d+_create_blogs\.blog_engine\.rb from blog_engine/, output.last)
       end
     end
 
@@ -171,8 +171,8 @@ module RailtiesTest
       Dir.chdir(app_path) do
         output = `bundle exec rake railties:install:migrations`.split("\n")
 
-        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.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.last)
       end
     end
 
@@ -202,7 +202,7 @@ 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_match(/Copied migration 0_add_first_name_to_users\.bukkits\.rb from bukkits/, output)
         assert_equal 1, Dir["#{app_path}/db/migrate/*.rb"].length
       end
     end
diff --git a/railties/test/test_unit/reporter_test.rb b/railties/test/test_unit/reporter_test.rb
index e22c939981..98201394cd 100644
--- a/railties/test/test_unit/reporter_test.rb
+++ b/railties/test/test_unit/reporter_test.rb
@@ -16,7 +16,7 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     @reporter.record(failed_test)
     @reporter.report
 
-    assert_match %r{^bin/rails test .*test/test_unit/reporter_test.rb:\d+$}, @output.string
+    assert_match %r{^bin/rails test .*test/test_unit/reporter_test\.rb:\d+$}, @output.string
     assert_rerun_snippet_count 1
   end
 
@@ -52,7 +52,7 @@ class TestUnitReporterTest < ActiveSupport::TestCase
       @reporter.record(failed_test)
       @reporter.report
 
-      assert_match %r{^bin/test .*test/test_unit/reporter_test.rb:\d+$}, @output.string
+      assert_match %r{^bin/test .*test/test_unit/reporter_test\.rb:\d+$}, @output.string
     ensure
       Rails::TestUnitReporter.executable = original_executable
     end
@@ -62,7 +62,7 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     @reporter.record(failed_test)
     @reporter.report
 
-    expect = %r{\AF\n\nFailure:\nTestUnitReporterTest::ExampleTest#woot \[[^\]]+\]:\nboo\n\nbin/rails test test/test_unit/reporter_test.rb:\d+\n\n\z}
+    expect = %r{\AF\n\nFailure:\nTestUnitReporterTest::ExampleTest#woot \[[^\]]+\]:\nboo\n\nbin/rails test test/test_unit/reporter_test\.rb:\d+\n\n\z}
     assert_match expect, @output.string
   end
 
@@ -70,7 +70,7 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     @reporter.record(errored_test)
     @reporter.report
 
-    expect = %r{\AE\n\nError:\nTestUnitReporterTest::ExampleTest#woot:\nArgumentError: wups\n    No backtrace\n\nbin/rails test .*test/test_unit/reporter_test.rb:\d+\n\n\z}
+    expect = %r{\AE\n\nError:\nTestUnitReporterTest::ExampleTest#woot:\nArgumentError: wups\n    No backtrace\n\nbin/rails test .*test/test_unit/reporter_test\.rb:\d+\n\n\z}
     assert_match expect, @output.string
   end
 
@@ -79,7 +79,7 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     verbose.record(skipped_test)
     verbose.report
 
-    expect = %r{\ATestUnitReporterTest::ExampleTest#woot = 10\.00 s = S\n\n\nSkipped:\nTestUnitReporterTest::ExampleTest#woot \[[^\]]+\]:\nskipchurches, misstemples\n\nbin/rails test test/test_unit/reporter_test.rb:\d+\n\n\z}
+    expect = %r{\ATestUnitReporterTest::ExampleTest#woot = 10\.00 s = S\n\n\nSkipped:\nTestUnitReporterTest::ExampleTest#woot \[[^\]]+\]:\nskipchurches, misstemples\n\nbin/rails test test/test_unit/reporter_test\.rb:\d+\n\n\z}
     assert_match expect, @output.string
   end
 
diff --git a/tasks/release.rb b/tasks/release.rb
index b021535245..038fdc584a 100644
--- a/tasks/release.rb
+++ b/tasks/release.rb
@@ -1,7 +1,7 @@
 FRAMEWORKS = %w( activesupport activemodel activerecord actionview actionpack activejob actionmailer actioncable railties )
 FRAMEWORK_NAMES = Hash.new { |h, k| k.split(/(?<=active|action)/).map(&:capitalize).join(" ") }
 
-root    = File.expand_path("../../", __FILE__)
+root    = File.expand_path("..", __dir__)
 version = File.read("#{root}/RAILS_VERSION").strip
 tag     = "v#{version}"
 gem_version = Gem::Version.new(version)
diff --git a/tools/test.rb b/tools/test.rb
index 71349a5974..1a1eca8f95 100644
--- a/tools/test.rb
+++ b/tools/test.rb
@@ -7,11 +7,12 @@ require "rails/test_unit/minitest_plugin"
 require "rails/test_unit/line_filtering"
 require "active_support/test_case"
 
-module Rails
+class << Rails
   # Necessary to get rerun-snippts working.
-  def self.root
+  def root
     @root ||= Pathname.new(COMPONENT_ROOT)
   end
+  alias __root root
 end
 
 ActiveSupport::TestCase.extend Rails::LineFiltering