Merge branch 'master' into update_default_hsts_max_age

45 files changed, 207 insertions, 142 deletions

diff --git a/railties/lib/minitest/rails_plugin.rb b/railties/lib/minitest/rails_plugin.rb
index 6901b0bbc8..7193abbc33 100644
--- a/railties/lib/minitest/rails_plugin.rb
+++ b/railties/lib/minitest/rails_plugin.rb
@@ -43,10 +43,15 @@ module Minitest
       Minitest.backtrace_filter = ::Rails.backtrace_cleaner if ::Rails.respond_to?(:backtrace_cleaner)
     end
 
+    # Suppress summary reports when outputting inline rerun snippets.
+    if reporter.reporters.reject! { |reporter| reporter.kind_of?(SummaryReporter) }
+      reporter << SuppressedSummaryReporter.new(options[:io], options)
+    end
+
     # Replace progress reporter for colors.
-    reporter.reporters.delete_if { |reporter| reporter.kind_of?(SummaryReporter) || reporter.kind_of?(ProgressReporter) }
-    reporter << SuppressedSummaryReporter.new(options[:io], options)
-    reporter << ::Rails::TestUnitReporter.new(options[:io], options)
+    if reporter.reporters.reject! { |reporter| reporter.kind_of?(ProgressReporter) }
+      reporter << ::Rails::TestUnitReporter.new(options[:io], options)
+    end
   end
 
   # Backwardscompatibility with Rails 5.0 generated plugin test scripts
diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index a200a1005c..a9dee10981 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -268,7 +268,8 @@ module Rails
           "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest,
           "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations,
           "action_dispatch.content_security_policy" => config.content_security_policy,
-          "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only
+          "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only,
+          "action_dispatch.content_security_policy_nonce_generator" => config.content_security_policy_nonce_generator
         )
       end
     end
diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index f02aef94e0..b42ffe50d8 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -17,47 +17,49 @@ module Rails
                     :session_options, :time_zone, :reload_classes_only_on_change,
                     :beginning_of_week, :filter_redirect, :x, :enable_dependency_loading,
                     :read_encrypted_secrets, :log_level, :content_security_policy_report_only,
-                    :require_master_key
+                    :content_security_policy_nonce_generator, :require_master_key
 
-      attr_reader :encoding, :api_only
+      attr_reader :encoding, :api_only, :loaded_config_version
 
       def initialize(*)
         super
-        self.encoding                        = Encoding::UTF_8
-        @allow_concurrency                   = nil
-        @consider_all_requests_local         = false
-        @filter_parameters                   = []
-        @filter_redirect                     = []
-        @helpers_paths                       = []
-        @public_file_server                  = ActiveSupport::OrderedOptions.new
-        @public_file_server.enabled          = true
-        @public_file_server.index_name       = "index"
-        @force_ssl                           = false
-        @ssl_options                         = {}
-        @session_store                       = nil
-        @time_zone                           = "UTC"
-        @beginning_of_week                   = :monday
-        @log_level                           = :debug
-        @generators                          = app_generators
-        @cache_store                         = [ :file_store, "#{root}/tmp/cache/" ]
-        @railties_order                      = [:all]
-        @relative_url_root                   = ENV["RAILS_RELATIVE_URL_ROOT"]
-        @reload_classes_only_on_change       = true
-        @file_watcher                        = ActiveSupport::FileUpdateChecker
-        @exceptions_app                      = nil
-        @autoflush_log                       = true
-        @log_formatter                       = ActiveSupport::Logger::SimpleFormatter.new
-        @eager_load                          = nil
-        @secret_token                        = nil
-        @secret_key_base                     = nil
-        @api_only                            = false
-        @debug_exception_response_format     = nil
-        @x                                   = Custom.new
-        @enable_dependency_loading           = false
-        @read_encrypted_secrets              = false
-        @content_security_policy             = nil
-        @content_security_policy_report_only = false
-        @require_master_key                  = false
+        self.encoding                            = Encoding::UTF_8
+        @allow_concurrency                       = nil
+        @consider_all_requests_local             = false
+        @filter_parameters                       = []
+        @filter_redirect                         = []
+        @helpers_paths                           = []
+        @public_file_server                      = ActiveSupport::OrderedOptions.new
+        @public_file_server.enabled              = true
+        @public_file_server.index_name           = "index"
+        @force_ssl                               = false
+        @ssl_options                             = {}
+        @session_store                           = nil
+        @time_zone                               = "UTC"
+        @beginning_of_week                       = :monday
+        @log_level                               = :debug
+        @generators                              = app_generators
+        @cache_store                             = [ :file_store, "#{root}/tmp/cache/" ]
+        @railties_order                          = [:all]
+        @relative_url_root                       = ENV["RAILS_RELATIVE_URL_ROOT"]
+        @reload_classes_only_on_change           = true
+        @file_watcher                            = ActiveSupport::FileUpdateChecker
+        @exceptions_app                          = nil
+        @autoflush_log                           = true
+        @log_formatter                           = ActiveSupport::Logger::SimpleFormatter.new
+        @eager_load                              = nil
+        @secret_token                            = nil
+        @secret_key_base                         = nil
+        @api_only                                = false
+        @debug_exception_response_format         = nil
+        @x                                       = Custom.new
+        @enable_dependency_loading               = false
+        @read_encrypted_secrets                  = false
+        @content_security_policy                 = nil
+        @content_security_policy_report_only     = false
+        @content_security_policy_nonce_generator = nil
+        @require_master_key                      = false
+        @loaded_config_version                   = nil
       end
 
       def load_defaults(target_version)
@@ -112,9 +114,14 @@ module Rails
           if respond_to?(:action_view)
             action_view.form_with_generates_ids = true
           end
+        when "6.0"
+          load_defaults "5.2"
+
         else
           raise "Unknown version #{target_version.to_s.inspect}"
         end
+
+        @loaded_config_version = target_version
       end
 
       def encoding=(value)
@@ -235,7 +242,11 @@ module Rails
       end
 
       def content_security_policy(&block)
-        @content_security_policy ||= ActionDispatch::ContentSecurityPolicy.new(&block)
+        if block_given?
+          @content_security_policy = ActionDispatch::ContentSecurityPolicy.new(&block)
+        else
+          @content_security_policy
+        end
       end
 
       class Custom #:nodoc:
diff --git a/railties/lib/rails/application/default_middleware_stack.rb b/railties/lib/rails/application/default_middleware_stack.rb
index 0e79ba7da0..433a7ab41f 100644
--- a/railties/lib/rails/application/default_middleware_stack.rb
+++ b/railties/lib/rails/application/default_middleware_stack.rb
@@ -70,6 +70,8 @@ module Rails
           middleware.use ::Rack::Head
           middleware.use ::Rack::ConditionalGet
           middleware.use ::Rack::ETag, "no-cache"
+
+          middleware.use ::Rack::TempfileReaper unless config.api_only
         end
       end
 
diff --git a/railties/lib/rails/command.rb b/railties/lib/rails/command.rb
index 812e846837..078e9f937f 100644
--- a/railties/lib/rails/command.rb
+++ b/railties/lib/rails/command.rb
@@ -4,7 +4,6 @@ require "active_support"
 require "active_support/dependencies/autoload"
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/object/blank"
-require "active_support/core_ext/hash/transform_values"
 
 require "thor"
 
diff --git a/railties/lib/rails/commands/credentials/credentials_command.rb b/railties/lib/rails/commands/credentials/credentials_command.rb
index 385d3976da..fa54c0362a 100644
--- a/railties/lib/rails/commands/credentials/credentials_command.rb
+++ b/railties/lib/rails/commands/credentials/credentials_command.rb
@@ -20,7 +20,7 @@ module Rails
         require_application_and_environment!
 
         ensure_editor_available(command: "bin/rails credentials:edit") || (return)
-        ensure_master_key_has_been_added
+        ensure_master_key_has_been_added if Rails.application.credentials.key.nil?
         ensure_credentials_have_been_added
 
         catch_editing_exceptions do
diff --git a/railties/lib/rails/commands/encrypted/encrypted_command.rb b/railties/lib/rails/commands/encrypted/encrypted_command.rb
index 912c453f09..3bc8f76ce4 100644
--- a/railties/lib/rails/commands/encrypted/encrypted_command.rb
+++ b/railties/lib/rails/commands/encrypted/encrypted_command.rb
@@ -21,9 +21,10 @@ module Rails
 
       def edit(file_path)
         require_application_and_environment!
+        encrypted = Rails.application.encrypted(file_path, key_path: options[:key])
 
         ensure_editor_available(command: "bin/rails encrypted:edit") || (return)
-        ensure_encryption_key_has_been_added(options[:key])
+        ensure_encryption_key_has_been_added(options[:key]) if encrypted.key.nil?
         ensure_encrypted_file_has_been_added(file_path, options[:key])
 
         catch_editing_exceptions do
diff --git a/railties/lib/rails/gem_version.rb b/railties/lib/rails/gem_version.rb
index 2cc861a1bd..54bfbdd516 100644
--- a/railties/lib/rails/gem_version.rb
+++ b/railties/lib/rails/gem_version.rb
@@ -7,10 +7,10 @@ module Rails
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index 6c9c109f17..6a7175c02b 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -218,6 +218,9 @@ module Rails
         rails.delete("app")
         rails.delete("plugin")
         rails.delete("encrypted_secrets")
+        rails.delete("encrypted_file")
+        rails.delete("encryption_key_file")
+        rails.delete("master_key")
         rails.delete("credentials")
 
         hidden_namespaces.each { |n| groups.delete(n.to_s) }
diff --git a/railties/lib/rails/generators/actions.rb b/railties/lib/rails/generators/actions.rb
index 3362bf629a..d85bbfb03e 100644
--- a/railties/lib/rails/generators/actions.rb
+++ b/railties/lib/rails/generators/actions.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/string/strip"
+
 module Rails
   module Generators
     module Actions
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index e152a95fd3..e1889979d7 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -2,7 +2,6 @@
 
 require "fileutils"
 require "digest/md5"
-require "active_support/core_ext/string/strip"
 require "rails/version" unless defined?(Rails::VERSION)
 require "open-uri"
 require "uri"
@@ -315,11 +314,13 @@ module Rails
 
       def convert_database_option_for_jruby
         if defined?(JRUBY_VERSION)
-          case options[:database]
-          when "postgresql" then options[:database].replace "jdbcpostgresql"
-          when "mysql"      then options[:database].replace "jdbcmysql"
-          when "sqlite3"    then options[:database].replace "jdbcsqlite3"
+          opt = options.dup
+          case opt[:database]
+          when "postgresql" then opt[:database] = "jdbcpostgresql"
+          when "mysql"      then opt[:database] = "jdbcmysql"
+          when "sqlite3"    then opt[:database] = "jdbcsqlite3"
           end
+          self.options = opt.freeze
         end
       end
 
diff --git a/railties/lib/rails/generators/generated_attribute.rb b/railties/lib/rails/generators/generated_attribute.rb
index 2728459968..f7fd30a5fb 100644
--- a/railties/lib/rails/generators/generated_attribute.rb
+++ b/railties/lib/rails/generators/generated_attribute.rb
@@ -75,7 +75,7 @@ module Rails
                         when :date                 then :date_select
                         when :text                 then :text_area
                         when :boolean              then :check_box
-          else
+                        else
                           :text_field
         end
       end
@@ -91,7 +91,7 @@ module Rails
                      when :text                        then "MyText"
                      when :boolean                     then false
                      when :references, :belongs_to     then nil
-          else
+                     else
                        ""
         end
       end
diff --git a/railties/lib/rails/generators/named_base.rb b/railties/lib/rails/generators/named_base.rb
index 98fcc95964..d6732f8ff1 100644
--- a/railties/lib/rails/generators/named_base.rb
+++ b/railties/lib/rails/generators/named_base.rb
@@ -31,12 +31,8 @@ module Rails
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :file_name
-
       private
+        attr_reader :file_name
 
         # FIXME: We are avoiding to use alias because a bug on thor that make
         # this method public and add it to the task list.
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index fd9da7803f..5ee9ae05e3 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -130,6 +130,8 @@ module Rails
       assets_config_exist            = File.exist?("config/initializers/assets.rb")
       csp_config_exist               = File.exist?("config/initializers/content_security_policy.rb")
 
+      @config_target_version = Rails.application.config.loaded_config_version || "5.0"
+
       config
 
       unless cookie_serializer_config_exist
@@ -167,7 +169,7 @@ module Rails
       return if options[:pretend] || options[:dummy_app]
 
       require "rails/generators/rails/master_key/master_key_generator"
-      master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet])
+      master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet], force: options[:force])
       master_key_generator.add_master_key_file_silently
       master_key_generator.ignore_master_key_file_silently
     end
@@ -233,6 +235,10 @@ module Rails
     def vendor
       empty_directory_with_keep_file "vendor"
     end
+
+    def config_target_version
+      defined?(@config_target_version) ? @config_target_version : Rails::VERSION::STRING.to_f
+    end
   end
 
   module Generators
@@ -242,7 +248,7 @@ module Rails
     RESERVED_NAMES = %w[application destroy plugin runner test]
 
     class AppGenerator < AppBase # :nodoc:
-      WEBPACKS = %w( react vue angular elm )
+      WEBPACKS = %w( react vue angular elm stimulus )
 
       add_shared_options_for "application"
 
@@ -383,9 +389,13 @@ module Rails
         end
       end
 
-      def delete_application_layout_file_if_api_option
+      def delete_app_views_if_api_option
         if options[:api]
-          remove_file "app/views/layouts/application.html.erb"
+          if options[:skip_action_mailer]
+            remove_dir "app/views"
+          else
+            remove_file "app/views/layouts/application.html.erb"
+          end
         end
       end
 
diff --git a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
index 5460155b3e..ef715f1368 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
@@ -3,6 +3,7 @@
   <head>
     <title><%= camelized %></title>
     <%%= csrf_meta_tags %>
+    <%%= csp_meta_tag %>
 
     <%- if options[:skip_javascript] -%>
     <%%= stylesheet_link_tag    'application', media: 'all' %>
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
index b4e4d95286..90ddcc520e 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
+++ b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
@@ -1,7 +1,7 @@
 APP_ROOT = File.expand_path('..', __dir__)
 Dir.chdir(APP_ROOT) do
   begin
-    exec "yarnpkg #{ARGV.join(' ')}"
+    exec "yarnpkg", *ARGV
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
diff --git a/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
index d1a09f9c3c..9a427113c7 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
@@ -24,7 +24,7 @@ Bundler.require(*Rails.groups)
 module <%= app_const_base %>
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults <%= Rails::VERSION::STRING.to_f %>
+    config.load_defaults <%= build(:config_target_version) %>
 
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration can go into files in config/initializers
diff --git a/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
index 720d36a2a4..42d46b8175 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
@@ -4,7 +4,3 @@ require 'bundler/setup' # Set up gems listed in the Gemfile.
 <% if depend_on_bootsnap? -%>
 require 'bootsnap/setup' # Speed up boot time by caching expensive operations.
 <%- end -%>
-
-if %w[s server c console].any? { |a| ARGV.include?(a) }
-  puts "=> Booting Rails"
-end
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
index 4c0f36db98..926326b5bb 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
@@ -34,8 +34,6 @@ Rails.application.configure do
   # Do not fallback to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
-  # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb
-
   <%- end -%>
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.action_controller.asset_host = 'http://assets.example.com'
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
index c82324ae4d..d3bcaa5ec8 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
@@ -4,17 +4,20 @@
 # For further information see the following documentation
 # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
 
-Rails.application.config.content_security_policy do |policy|
-  policy.default_src :self, :https
-  policy.font_src    :self, :https, :data
-  policy.img_src     :self, :https, :data
-  policy.object_src  :none
-  policy.script_src  :self, :https, :unsafe_inline
-  policy.style_src   :self, :https, :unsafe_inline
+# Rails.application.config.content_security_policy do |policy|
+#   policy.default_src :self, :https
+#   policy.font_src    :self, :https, :data
+#   policy.img_src     :self, :https, :data
+#   policy.object_src  :none
+#   policy.script_src  :self, :https
+#   policy.style_src   :self, :https
 
-  # Specify URI for violation reports
-  # policy.report_uri "/csp-violation-report-endpoint"
-end
+#   # Specify URI for violation reports
+#   # policy.report_uri "/csp-violation-report-endpoint"
+# end
+
+# If you are using UJS then enable automatic nonce generation
+# Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
 
 # Report CSP violations to a specified URI
 # For further information see the following documentation:
diff --git a/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
index fac165a24d..1c0cde0b09 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
@@ -1,12 +1,10 @@
 test:
   service: Disk
   root: <%%= Rails.root.join("tmp/storage") %>
-  host: http://localhost:3000
 
 local:
   service: Disk
   root: <%%= Rails.root.join("storage") %>
-  host: http://localhost:3000
 
 # Use rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
 # amazon:
diff --git a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
index 52d68cc77c..c918b57eca 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
@@ -3,6 +3,13 @@ require_relative '../config/environment'
 require 'rails/test_help'
 
 class ActiveSupport::TestCase
+  # Run tests in parallel with specified workers
+<% if defined?(JRUBY_VERSION) -%>
+  parallelize(workers: 2, with: :threads)
+<%- else -%>
+  parallelize(workers: 2)
+<% end -%>
+
 <% unless options[:skip_active_record] -%>
   # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
   fixtures :all
diff --git a/railties/lib/rails/generators/rails/controller/controller_generator.rb b/railties/lib/rails/generators/rails/controller/controller_generator.rb
index 6d45d6e8f8..6e2495d45f 100644
--- a/railties/lib/rails/generators/rails/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/rails/controller/controller_generator.rb
@@ -16,6 +16,7 @@ module Rails
 
       def add_routes
         return if options[:skip_routes]
+        return if actions.empty?
         route generate_routing_code
       end
 
diff --git a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
index 9103b1122e..719e0c1e4c 100644
--- a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
+++ b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
@@ -6,7 +6,7 @@ require "active_support/encrypted_configuration"
 
 module Rails
   module Generators
-    class CredentialsGenerator < Base
+    class CredentialsGenerator < Base # :nodoc:
       def add_credentials_file
         unless credentials.content_path.exist?
           template = credentials_template
@@ -42,9 +42,14 @@ module Rails
         end
 
         def credentials_template
-          "# aws:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n" +
-          "# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.\n" +
-          "secret_key_base: #{SecureRandom.hex(64)}"
+          <<~YAML
+            # aws:
+            #   access_key_id: 123
+            #   secret_access_key: 345
+
+            # Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
+            secret_key_base: #{SecureRandom.hex(64)}
+          YAML
         end
     end
   end
diff --git a/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
index 4ce2fc1d86..867e28c6db 100644
--- a/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
+++ b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
@@ -5,23 +5,7 @@ require "active_support/encrypted_file"
 
 module Rails
   module Generators
-    class EncryptedFileGenerator < Base
-      def add_encrypted_file(file_path, key_path)
-        unless File.exist?(file_path)
-          say "Adding #{file_path} to store encrypted content."
-          say ""
-          say "The following content has been encrypted with the encryption key:"
-          say ""
-          say template, :on_green
-          say ""
-
-          add_encrypted_file_silently(file_path, key_path)
-
-          say "You can edit encrypted file with `bin/rails encrypted:edit #{file_path}`."
-          say ""
-        end
-      end
-
+    class EncryptedFileGenerator < Base # :nodoc:
       def add_encrypted_file_silently(file_path, key_path, template = encrypted_file_template)
         unless File.exist?(file_path)
           setup = { content_path: file_path, key_path: key_path, env_key: "RAILS_MASTER_KEY", raise_if_missing_key: true }
@@ -31,7 +15,12 @@ module Rails
 
       private
         def encrypted_file_template
-          "# aws:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n"
+          <<~YAML
+            # aws:
+            #   access_key_id: 123
+            #   secret_access_key: 345
+
+          YAML
         end
     end
   end
diff --git a/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
index a396a9661f..90068c678d 100644
--- a/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
+++ b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
@@ -6,7 +6,7 @@ require "active_support/encrypted_file"
 
 module Rails
   module Generators
-    class EncryptionKeyFileGenerator < Base
+    class EncryptionKeyFileGenerator < Base # :nodoc:
       def add_key_file(key_path)
         key_path = Pathname.new(key_path)
 
diff --git a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
index 7f57340c11..21664ea86d 100644
--- a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
+++ b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
@@ -7,7 +7,7 @@ require "active_support/encrypted_file"
 
 module Rails
   module Generators
-    class MasterKeyGenerator < Base
+    class MasterKeyGenerator < Base # :nodoc:
       MASTER_KEY_PATH = Pathname.new("config/master.key")
 
       def add_master_key_file
@@ -27,7 +27,9 @@ module Rails
       end
 
       def add_master_key_file_silently(key = nil)
-        key_file_generator.add_key_file_silently(MASTER_KEY_PATH, key)
+        unless MASTER_KEY_PATH.exist?
+          key_file_generator.add_key_file_silently(MASTER_KEY_PATH, key)
+        end
       end
 
       def ignore_master_key_file
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
index abbacd9bec..b86ef0f2f8 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationController < ActionController::#{api? ? "API" : "Base"}
     #{ api? ? '# ' : '' }protect_from_forgery with: :exception
   end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
index 25d692732d..be078f36de 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   module ApplicationHelper
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
index bad1ff2d16..846863bc13 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationJob < ActiveJob::Base
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
index 09aac13f42..246e274348 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationMailer < ActionMailer::Base
     default from: 'from@example.com'
     layout 'mailer'
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
index 8aa3de78f1..21465278be 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationRecord < ActiveRecord::Base
     self.abstract_class = true
   end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
index 6bc480161d..6e54a1ce9d 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
@@ -2,9 +2,13 @@
 <html>
 <head>
   <title><%= humanized %></title>
+  <%%= csrf_meta_tags %>
+  <%%= csp_meta_tag %>
+
   <%%= stylesheet_link_tag    "<%= namespaced_name %>/application", media: "all" %>
+  <%- unless options[:skip_javascript] -%>
   <%%= javascript_include_tag "<%= namespaced_name %>/application" %>
-  <%%= csrf_meta_tags %>
+  <%- end -%>
 </head>
 <body>
 
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 b3264509fc..ee8e469da2 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
@@ -19,10 +19,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
index 8938770fc4..4ec1804940 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class Engine < ::Rails::Engine
   #{mountable? ? '  isolate_namespace ' + camelized_modules : ' '}
   #{api? ? "  config.generators.api_only = true" : ' '}
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
index 7bdf4ee5fb..b853fabcc3 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class Railtie < ::Rails::Railtie
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
index f3d80c87f5..51049826bf 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
@@ -10,6 +10,7 @@
 // Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
 // about supported directives.
 //
+//= require rails-ujs
 <% unless skip_active_storage? -%>
 //= require activestorage
 <% end -%>
diff --git a/railties/lib/rails/generators/resource_helpers.rb b/railties/lib/rails/generators/resource_helpers.rb
index a146a8fda6..5675faff70 100644
--- a/railties/lib/rails/generators/resource_helpers.rb
+++ b/railties/lib/rails/generators/resource_helpers.rb
@@ -25,13 +25,8 @@ module Rails
         assign_controller_names!(controller_name.pluralize)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :controller_name, :controller_file_name
-
       private
+        attr_reader :controller_name, :controller_file_name
 
         def controller_class_path
           if options[:model_name]
diff --git a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
index b6c13b41ae..e2e8b18eab 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
@@ -23,7 +23,7 @@ module TestUnit # :nodoc:
         template template_file,
                  File.join("test/controllers", controller_class_path, "#{controller_file_name}_controller_test.rb")
 
-        unless options.api? || options[:system_tests].nil?
+        if !options.api? && options[:system_tests]
           template "system_test.rb", File.join("test/system", class_path, "#{file_name.pluralize}_test.rb")
         end
       end
diff --git a/railties/lib/rails/info.rb b/railties/lib/rails/info.rb
index d8f361f524..d5c9973c6b 100644
--- a/railties/lib/rails/info.rb
+++ b/railties/lib/rails/info.rb
@@ -99,7 +99,7 @@ module Rails
     end
 
     property "Database schema version" do
-      ActiveRecord::Migrator.current_version rescue nil
+      ActiveRecord::Base.connection.migration_context.current_version rescue nil
     end
   end
 end
diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 66636e5d6b..0b0e802358 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -6,9 +6,9 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugExceptions::RESCUES_TEMPLATE_PATH
 
   before_action :require_local!, unless: :show_previews?
-  before_action :find_preview, only: :preview
+  before_action :find_preview, :set_locale, only: :preview
 
-  helper_method :part_query
+  helper_method :part_query, :locale_query
 
   def index
     @previews = ActionMailer::Preview.all
@@ -84,4 +84,12 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
     def part_query(mime_type)
       request.query_parameters.merge(part: mime_type).to_query
     end
+
+    def locale_query(locale)
+      request.query_parameters.merge(locale: locale).to_query
+    end
+
+    def set_locale
+      I18n.locale = params[:locale] || I18n.default_locale
+    end
 end
diff --git a/railties/lib/rails/ruby_version_check.rb b/railties/lib/rails/ruby_version_check.rb
index 76b6b80d28..f8d3311156 100644
--- a/railties/lib/rails/ruby_version_check.rb
+++ b/railties/lib/rails/ruby_version_check.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-if RUBY_VERSION < "2.2.2" && RUBY_ENGINE == "ruby"
+if RUBY_VERSION < "2.4.1" && RUBY_ENGINE == "ruby"
   desc = defined?(RUBY_DESCRIPTION) ? RUBY_DESCRIPTION : "ruby #{RUBY_VERSION} (#{RUBY_RELEASE_DATE})"
   abort <<-end_message
 
-    Rails 5 requires Ruby 2.2.2 or newer.
+    Rails 6 requires Ruby 2.4.1 or newer.
 
     You're running
       #{desc}
 
-    Please upgrade to Ruby 2.2.2 or newer to continue.
+    Please upgrade to Ruby 2.4.1 or newer to continue.
 
   end_message
 end
diff --git a/railties/lib/rails/secrets.rb b/railties/lib/rails/secrets.rb
index 30e3478c9b..747cf31d7a 100644
--- a/railties/lib/rails/secrets.rb
+++ b/railties/lib/rails/secrets.rb
@@ -2,7 +2,6 @@
 
 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. 😘
diff --git a/railties/lib/rails/templates/rails/mailers/email.html.erb b/railties/lib/rails/templates/rails/mailers/email.html.erb
index 89c1129f90..2a41c29602 100644
--- a/railties/lib/rails/templates/rails/mailers/email.html.erb
+++ b/railties/lib/rails/templates/rails/mailers/email.html.erb
@@ -95,11 +95,25 @@
       </dd>
     <% end %>
 
+    <dt>Format:</dt>
     <% if @email.multipart? %>
       <dd>
-        <select onchange="formatChanged(this);">
-          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="?<%= part_query('text/html') %>">View as HTML email</option>
-          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="?<%= part_query('text/plain') %>">View as plain-text email</option>
+        <select id="part" onchange="refreshBody();">
+          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="<%= part_query('text/html') %>">View as HTML email</option>
+          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="<%= part_query('text/plain') %>">View as plain-text email</option>
+        </select>
+      </dd>
+    <% else %>
+      <dd id="mime_type" data-mime-type="<%= part_query(@email.mime_type) %>"><%= @email.mime_type == 'text/html' ? 'HTML email' : 'plain-text email' %></dd>
+    <% end %>
+
+    <% if I18n.available_locales.count > 1 %>
+      <dt>Locale:</dt>
+      <dd>
+        <select id="locale" onchange="refreshBody();">
+          <% I18n.available_locales.each do |locale| %>
+            <option <%= I18n.locale == locale ? 'selected' : '' %> value="<%= locale_query(locale) %>"><%= locale %></option>
+          <% end %>
         </select>
       </dd>
     <% end %>
@@ -116,15 +130,27 @@
 <% end %>
 
 <script>
-  function formatChanged(form) {
-    var part_name = form.options[form.selectedIndex].value
-    var iframe =document.getElementsByName('messageBody')[0];
-    iframe.contentWindow.location.replace(part_name);
+  function refreshBody() {
+    var part_select = document.querySelector('select#part');
+    var locale_select = document.querySelector('select#locale');
+    var iframe = document.getElementsByName('messageBody')[0];
+    var part_param = part_select ?
+      part_select.options[part_select.selectedIndex].value :
+      document.querySelector('#mime_type').dataset.mimeType;
+    var locale_param = locale_select ? locale_select.options[locale_select.selectedIndex].value : null;
+    var fresh_location;
+    if (locale_param) {
+      fresh_location = '?' + part_param + '&' + locale_param;
+    } else {
+      fresh_location = '?' + part_param;
+    }
+    iframe.contentWindow.location = fresh_location;
 
     if (history.replaceState) {
-      var url    = location.pathname.replace(/\.(txt|html)$/, '');
-      var format = /html/.test(part_name) ? '.html' : '.txt';
-      window.history.replaceState({}, '', url + format);
+      var url = location.pathname.replace(/\.(txt|html)$/, '');
+      var format = /html/.test(part_param) ? '.html' : '.txt';
+      var state_to_replace = locale_param ? (url + format + '?' + locale_param) : (url + format);
+      window.history.replaceState({}, '', state_to_replace);
     }
   }
 </script>
diff --git a/railties/lib/rails/test_help.rb b/railties/lib/rails/test_help.rb
index 76c28ac85e..4bd7d74b04 100644
--- a/railties/lib/rails/test_help.rb
+++ b/railties/lib/rails/test_help.rb
@@ -22,6 +22,7 @@ if defined?(ActiveRecord::Base)
 
   module ActiveSupport
     class TestCase
+      include ActiveRecord::TestDatabases
       include ActiveRecord::TestFixtures
       self.fixture_path = "#{Rails.root}/test/fixtures/"
       self.file_fixture_path = fixture_path + "files"