Merge branch 'master' into bug/filtered_parameters_class

48 files changed, 249 insertions, 170 deletions

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index d478f4c437..ceaea40d18 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,15 @@
+*   Generate field ids in `collection_check_boxes` and `collection_radio_buttons`.
+
+    This makes sure that the labels are linked up with the fields.
+
+    Fixes #29014.
+
+    *Yuji Yaginuma*
+
+*   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.
 
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..f321b9f720 100644
--- a/actionview/app/assets/javascripts/README.md
+++ b/actionview/app/assets/javascripts/README.md
@@ -30,16 +30,27 @@ Run `yarn add rails-ujs` to install the rails-ujs package.
 Usage
 ------------
 
-Require `rails-ujs` into your application.js manifest.
+Require `rails-ujs` in your application.js manifest.
 
 ```javascript
 //= require rails-ujs
 ```
 
+Usage with yarn
+------------
+
+When using with the 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/start.coffee b/actionview/app/assets/javascripts/rails-ujs/start.coffee
index 5746a22287..55595ac96f 100644
--- a/actionview/app/assets/javascripts/rails-ujs/start.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/start.coffee
@@ -9,7 +9,7 @@
 } = Rails
 
 # For backward compatibility
-if jQuery? and not jQuery.rails
+if jQuery? and jQuery.ajax? and not jQuery.rails
   jQuery.rails = Rails
   jQuery.ajaxPrefilter (options, originalOptions, xhr) ->
     CSRFProtection(xhr) unless options.crossDomain
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/bin/test b/actionview/bin/test
index a7beb14b27..470ce93f10 100755
--- a/actionview/bin/test
+++ b/actionview/bin/test
@@ -1,4 +1,4 @@
 #!/usr/bin/env ruby
 
 COMPONENT_ROOT = File.expand_path("..", __dir__)
-require File.expand_path("../tools/test", COMPONENT_ROOT)
+require_relative "../../tools/test"
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/base.rb b/actionview/lib/action_view/base.rb
index 5387174467..1808553239 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -140,30 +140,25 @@ module ActionView #:nodoc:
     include Helpers, ::ERB::Util, Context
 
     # Specify the proc used to decorate input tags that refer to attributes with errors.
-    cattr_accessor :field_error_proc
-    @@field_error_proc = Proc.new { |html_tag, instance| "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe }
+    cattr_accessor :field_error_proc, default: Proc.new { |html_tag, instance| "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe }
 
     # How to complete the streaming when an exception occurs.
     # This is our best guess: first try to close the attribute, then the tag.
-    cattr_accessor :streaming_completion_on_exception
-    @@streaming_completion_on_exception = %("><script>window.location = "/500.html"</script></html>)
+    cattr_accessor :streaming_completion_on_exception, default: %("><script>window.location = "/500.html"</script></html>)
 
     # Specify whether rendering within namespaced controllers should prefix
     # the partial paths for ActiveModel objects with the namespace.
     # (e.g., an Admin::PostsController would render @post using /admin/posts/_post.erb)
-    cattr_accessor :prefix_partial_path_with_controller_namespace
-    @@prefix_partial_path_with_controller_namespace = true
+    cattr_accessor :prefix_partial_path_with_controller_namespace, default: true
 
     # Specify default_formats that can be rendered.
     cattr_accessor :default_formats
 
     # Specify whether an error should be raised for missing translations
-    cattr_accessor :raise_on_missing_translations
-    @@raise_on_missing_translations = false
+    cattr_accessor :raise_on_missing_translations, default: false
 
     # Specify whether submit_tag should automatically disable on click
-    cattr_accessor :automatically_disable_submit_tag
-    @@automatically_disable_submit_tag = true
+    cattr_accessor :automatically_disable_submit_tag, default: true
 
     class_attribute :_routes
     class_attribute :logger
@@ -207,6 +202,7 @@ module ActionView #:nodoc:
         @view_renderer = ActionView::Renderer.new(lookup_context)
       end
 
+      @cache_hit = {}
       assign(assigns)
       assign_controller(controller)
       _prepare_context
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..b7c7324f31 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:
@@ -211,16 +214,19 @@ module ActionView
         end
       end
 
-      attr_reader :cache_hit # :nodoc:
-
     private
 
       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
@@ -228,10 +234,10 @@ module ActionView
 
       def fragment_for(name = {}, options = nil, &block)
         if content = read_fragment_for(name, options)
-          @cache_hit = true
+          @view_renderer.cache_hits[@virtual_path] = :hit if defined?(@view_renderer)
           content
         else
-          @cache_hit = false
+          @view_renderer.cache_hits[@virtual_path] = :miss if defined?(@view_renderer)
           write_fragment_for(name, options, &block)
         end
       end
diff --git a/actionview/lib/action_view/helpers/form_helper.rb b/actionview/lib/action_view/helpers/form_helper.rb
index 3eafe0028e..4b2561e53d 100644
--- a/actionview/lib/action_view/helpers/form_helper.rb
+++ b/actionview/lib/action_view/helpers/form_helper.rb
@@ -474,7 +474,7 @@ module ActionView
       end
       private :apply_form_for_options!
 
-      mattr_accessor(:form_with_generates_remote_forms) { true }
+      mattr_accessor :form_with_generates_remote_forms, default: true
 
       # Creates a form tag based on mixing URLs, scopes, or models.
       #
@@ -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
 
@@ -2317,8 +2318,6 @@ module ActionView
   end
 
   ActiveSupport.on_load(:action_view) do
-    cattr_accessor(:default_form_builder, instance_writer: false, instance_reader: false) do
-      ::ActionView::Helpers::FormBuilder
-    end
+    cattr_accessor :default_form_builder, instance_writer: false, instance_reader: false, default: ::ActionView::Helpers::FormBuilder
   end
 end
diff --git a/actionview/lib/action_view/helpers/tags/base.rb b/actionview/lib/action_view/helpers/tags/base.rb
index aa420c4b66..0895533a60 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.except!("skip_default_ids", "allow_method_names_outside_object"))
+            select = content_tag("select", add_options(option_tags, options, value), html_options)
 
             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/collection_check_boxes.rb b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
index 7252d4f2d9..e02b7bdb2e 100644
--- a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
@@ -10,6 +10,7 @@ module ActionView
           def check_box(extra_html_options = {})
             html_options = extra_html_options.merge(@input_html_options)
             html_options[:multiple] = true
+            html_options[:skip_default_ids] = false
             @template_object.check_box(@object_name, @method_name, html_options, @value, nil)
           end
         end
diff --git a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
index a5f72af9ff..f085a5fb73 100644
--- a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
@@ -9,6 +9,7 @@ module ActionView
         class RadioButtonBuilder < Builder # :nodoc:
           def radio_button(extra_html_options = {})
             html_options = extra_html_options.merge(@input_html_options)
+            html_options[:skip_default_ids] = false
             @template_object.radio_button(@object_name, @method_name, @value, html_options)
           end
         end
diff --git a/actionview/lib/action_view/helpers/tags/select.rb b/actionview/lib/action_view/helpers/tags/select.rb
index 667c7e945a..380f7a8c4e 100644
--- a/actionview/lib/action_view/helpers/tags/select.rb
+++ b/actionview/lib/action_view/helpers/tags/select.rb
@@ -6,7 +6,7 @@ module ActionView
           @choices = block_given? ? template_object.capture { yield || "" } : choices
           @choices = @choices.to_a if @choices.is_a?(Range)
 
-          @html_options = html_options
+          @html_options = html_options.except(:skip_default_ids, :allow_method_names_outside_object)
 
           super(object_name, method_name, template_object, options)
         end
@@ -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/helpers/translation_helper.rb b/actionview/lib/action_view/helpers/translation_helper.rb
index 47ed41a129..cc928f2b7a 100644
--- a/actionview/lib/action_view/helpers/translation_helper.rb
+++ b/actionview/lib/action_view/helpers/translation_helper.rb
@@ -11,8 +11,7 @@ module ActionView
       include TagHelper
 
       included do
-        mattr_accessor :debug_missing_translation
-        self.debug_missing_translation = true
+        mattr_accessor :debug_missing_translation, default: true
       end
 
       # Delegates to <tt>I18n#translate</tt> but also performs three additional
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/log_subscriber.rb b/actionview/lib/action_view/log_subscriber.rb
index d03e1a51b8..ab8ec0aa42 100644
--- a/actionview/lib/action_view/log_subscriber.rb
+++ b/actionview/lib/action_view/log_subscriber.rb
@@ -25,7 +25,7 @@ module ActionView
         message = "  Rendered #{from_rails_root(event.payload[:identifier])}"
         message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
         message << " (#{event.duration.round(1)}ms)"
-        message << " #{cache_message(event.payload)}" if event.payload.key?(:cache_hit)
+        message << " #{cache_message(event.payload)}" unless event.payload[:cache_hit].nil?
         message
       end
     end
@@ -73,9 +73,10 @@ module ActionView
     end
 
     def cache_message(payload) # :doc:
-      if payload[:cache_hit]
+      case payload[:cache_hit]
+      when :hit
         "[cache hit]"
-      else
+      when :miss
         "[cache miss]"
       end
     end
diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index f385a7cd04..b7dbb38369 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -14,11 +14,9 @@ module ActionView
   class LookupContext #:nodoc:
     attr_accessor :prefixes, :rendered_format
 
-    mattr_accessor :fallbacks
-    @@fallbacks = FallbackFileSystemResolver.instances
+    mattr_accessor :fallbacks, default: FallbackFileSystemResolver.instances
 
-    mattr_accessor :registered_details
-    self.registered_details = []
+    mattr_accessor :registered_details, default: []
 
     def self.register_detail(name, &block)
       registered_details << name
diff --git a/actionview/lib/action_view/renderer/partial_renderer.rb b/actionview/lib/action_view/renderer/partial_renderer.rb
index 647b15ea94..1f8f997a2d 100644
--- a/actionview/lib/action_view/renderer/partial_renderer.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer.rb
@@ -344,7 +344,7 @@ module ActionView
           end
 
           content = layout.render(view, locals) { content } if layout
-          payload[:cache_hit] = view.cache_hit
+          payload[:cache_hit] = view.view_renderer.cache_hits[@template.virtual_path]
           content
         end
       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..32663fb80d 100644
--- a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
@@ -5,7 +5,7 @@ module ActionView
     included do
       # Fallback cache store if Action View is used without Rails.
       # Otherwise overridden in Railtie to use Rails.cache.
-      mattr_accessor(:collection_cache) { ActiveSupport::Cache::MemoryStore.new }
+      mattr_accessor :collection_cache, default: ActiveSupport::Cache::MemoryStore.new
     end
 
     private
@@ -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/renderer/renderer.rb b/actionview/lib/action_view/renderer/renderer.rb
index 2a3b89aebf..bcdeb85d30 100644
--- a/actionview/lib/action_view/renderer/renderer.rb
+++ b/actionview/lib/action_view/renderer/renderer.rb
@@ -46,5 +46,9 @@ module ActionView
     def render_partial(context, options, &block) #:nodoc:
       PartialRenderer.new(@lookup_context).render(context, options, block)
     end
+
+    def cache_hits # :nodoc:
+      @cache_hits ||= {}
+    end
   end
 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/template/resolver.rb b/actionview/lib/action_view/template/resolver.rb
index d3905b5f23..75ea4d31f5 100644
--- a/actionview/lib/action_view/template/resolver.rb
+++ b/actionview/lib/action_view/template/resolver.rb
@@ -125,8 +125,7 @@ module ActionView
         end
     end
 
-    cattr_accessor :caching
-    self.caching = true
+    cattr_accessor :caching, default: true
 
     class << self
       alias :caching? :caching
diff --git a/actionview/lib/action_view/test_case.rb b/actionview/lib/action_view/test_case.rb
index ae4fec4337..80403799ab 100644
--- a/actionview/lib/action_view/test_case.rb
+++ b/actionview/lib/action_view/test_case.rb
@@ -71,7 +71,7 @@ module ActionView
         def helper_method(*methods)
           # Almost a duplicate from ActionController::Helpers
           methods.flatten.each do |method|
-            _helpers.module_eval <<-end_eval
+            _helpers.module_eval <<-end_eval, __FILE__, __LINE__ + 1
               def #{method}(*args, &block)                    # def current_user(*args, &block)
                 _test_case.send(%(#{method}), *args, &block)  #   _test_case.send(%(current_user), *args, &block)
               end                                             # end
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/relation_cache_test.rb b/actionview/test/activerecord/relation_cache_test.rb
index 43f7242ee9..d12c426586 100644
--- a/actionview/test/activerecord/relation_cache_test.rb
+++ b/actionview/test/activerecord/relation_cache_test.rb
@@ -4,13 +4,17 @@ class RelationCacheTest < ActionView::TestCase
   tests ActionView::Helpers::CacheHelper
 
   def setup
-    @virtual_path = "path"
+    view_paths     = ActionController::Base.view_paths
+    lookup_context = ActionView::LookupContext.new(view_paths, {}, ["test"])
+    @view_renderer = ActionView::Renderer.new(lookup_context)
+    @virtual_path  = "path"
+
     controller.cache_store = ActiveSupport::Cache::MemoryStore.new
   end
 
   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/test/_cached_nested_cached_customer.erb b/actionview/test/fixtures/test/_cached_nested_cached_customer.erb
new file mode 100644
index 0000000000..01bf025cd3
--- /dev/null
+++ b/actionview/test/fixtures/test/_cached_nested_cached_customer.erb
@@ -0,0 +1,3 @@
+<% cache cached_customer do %>
+  <%= render partial: "test/cached_customer", locals: { cached_customer: cached_customer } %>
+<% end %>
diff --git a/actionview/test/fixtures/test/_nested_cached_customer.erb b/actionview/test/fixtures/test/_nested_cached_customer.erb
new file mode 100644
index 0000000000..f43adc94c9
--- /dev/null
+++ b/actionview/test/fixtures/test/_nested_cached_customer.erb
@@ -0,0 +1 @@
+<%= render partial: "test/cached_customer", locals: { cached_customer: cached_customer } %>
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index b7a993c5c9..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" />),
diff --git a/actionview/test/template/date_helper_test.rb b/actionview/test/template/date_helper_test.rb
index a259752d6a..b667303318 100644
--- a/actionview/test/template/date_helper_test.rb
+++ b/actionview/test/template/date_helper_test.rb
@@ -138,11 +138,19 @@ class DateHelperTest < ActionView::TestCase
     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" }
+  def test_distance_in_words_doesnt_use_the_quotient_operator
+    rubinius_skip "Date is written in Ruby and relies on Fixnum#/"
+    jruby_skip "Date is written in Ruby and relies on Fixnum#/"
+
+    klass = RUBY_VERSION > "2.4" ? Integer : Fixnum
+
+    # Make sure that we avoid {Integer,Fixnum}#/ (redefined by mathn)
+    klass.send :private, :/
+
     from = Time.utc(2004, 6, 6, 21, 45, 0)
     assert_distance_of_time_in_words(from)
+  ensure
+    klass.send :public, :/
   end
 
   def test_time_ago_in_words_passes_include_seconds
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 bff0643fb0..ecdd5ce672 100644
--- a/actionview/test/template/form_helper/form_with_test.rb
+++ b/actionview/test/template/form_helper/form_with_test.rb
@@ -403,9 +403,9 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts") do
       "<input type='hidden' name='post[active]' value='' />" \
-      "<input name='post[active]' type='radio' value='true' />" \
+      "<input name='post[active]' type='radio' value='true' id='post_active_true' />" \
       "<label for='post_active_true'>true</label>" \
-      "<input checked='checked' name='post[active]' type='radio' value='false' />" \
+      "<input checked='checked' name='post[active]' type='radio' value='false' id='post_active_false' />" \
       "<label for='post_active_false'>false</label>"
     end
 
@@ -426,10 +426,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     expected = whole_form("/posts") do
       "<input type='hidden' name='post[active]' value='' />" \
       "<label for='post_active_true'>" \
-      "<input name='post[active]' type='radio' value='true' />" \
+      "<input name='post[active]' type='radio' value='true' id='post_active_true' />" \
       "true</label>" \
       "<label for='post_active_false'>" \
-      "<input checked='checked' name='post[active]' type='radio' value='false' />" \
+      "<input checked='checked' name='post[active]' type='radio' value='false' id='post_active_false' />" \
       "false</label>"
     end
 
@@ -452,10 +452,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     expected = whole_form("/posts") do
       "<input type='hidden' name='post[active]' value='' />" \
       "<label for='post_active_true'>" \
-      "<input name='post[active]' type='radio' value='true' />" \
+      "<input name='post[active]' type='radio' value='true' id='post_active_true' />" \
       "true</label>" \
       "<label for='post_active_false'>" \
-      "<input checked='checked' name='post[active]' type='radio' value='false' />" \
+      "<input checked='checked' name='post[active]' type='radio' value='false' id='post_active_false' />" \
       "false</label>" \
       "<input name='post[id]' type='hidden' value='1' />"
     end
@@ -473,9 +473,9 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts") do
       "<input type='hidden' name='post[1][active]' value='' />" \
-      "<input name='post[1][active]' type='radio' value='true' />" \
+      "<input name='post[1][active]' type='radio' value='true' id='post_1_active_true' />" \
       "<label for='post_1_active_true'>true</label>" \
-      "<input checked='checked' name='post[1][active]' type='radio' value='false' />" \
+      "<input checked='checked' name='post[1][active]' type='radio' value='false' id='post_1_active_false' />" \
       "<label for='post_1_active_false'>false</label>"
     end
 
@@ -492,11 +492,11 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts") do
       "<input name='post[tag_ids][]' type='hidden' value='' />" \
-      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='1' />" \
+      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='1' id='post_tag_ids_1' />" \
       "<label for='post_tag_ids_1'>Tag 1</label>" \
-      "<input name='post[tag_ids][]' type='checkbox' value='2' />" \
+      "<input name='post[tag_ids][]' type='checkbox' value='2' id='post_tag_ids_2' />" \
       "<label for='post_tag_ids_2'>Tag 2</label>" \
-      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' />" \
+      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' id='post_tag_ids_3' />" \
       "<label for='post_tag_ids_3'>Tag 3</label>"
     end
 
@@ -517,13 +517,13 @@ class FormWithActsLikeFormForTest < FormWithTest
     expected = whole_form("/posts") do
       "<input name='post[tag_ids][]' type='hidden' value='' />" \
       "<label for='post_tag_ids_1'>" \
-      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='1' />" \
+      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='1' id='post_tag_ids_1' />" \
       "Tag 1</label>" \
       "<label for='post_tag_ids_2'>" \
-      "<input name='post[tag_ids][]' type='checkbox' value='2' />" \
+      "<input name='post[tag_ids][]' type='checkbox' value='2' id='post_tag_ids_2' />" \
       "Tag 2</label>" \
       "<label for='post_tag_ids_3'>" \
-      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' />" \
+      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' id='post_tag_ids_3' />" \
       "Tag 3</label>"
     end
 
@@ -547,13 +547,13 @@ class FormWithActsLikeFormForTest < FormWithTest
     expected = whole_form("/posts") do
       "<input name='post[tag_ids][]' type='hidden' value='' />" \
       "<label for='post_tag_ids_1'>" \
-      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='1' />" \
+      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='1' id='post_tag_ids_1' />" \
       "Tag 1</label>" \
       "<label for='post_tag_ids_2'>" \
-      "<input name='post[tag_ids][]' type='checkbox' value='2' />" \
+      "<input name='post[tag_ids][]' type='checkbox' value='2' id='post_tag_ids_2' />" \
       "Tag 2</label>" \
       "<label for='post_tag_ids_3'>" \
-      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' />" \
+      "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' id='post_tag_ids_3' />" \
       "Tag 3</label>" \
       "<input name='post[id]' type='hidden' value='1' />"
     end
@@ -572,7 +572,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts") do
       "<input name='post[1][tag_ids][]' type='hidden' value='' />" \
-      "<input checked='checked' name='post[1][tag_ids][]' type='checkbox' value='1' />" \
+      "<input checked='checked' name='post[1][tag_ids][]' type='checkbox' value='1' id='post_1_tag_ids_1' />" \
       "<label for='post_1_tag_ids_1'>Tag 1</label>"
     end
 
@@ -878,24 +878,6 @@ class FormWithActsLikeFormForTest < FormWithTest
     assert_dom_equal expected, output_buffer
   end
 
-  def test_form_with_with_namespace
-    skip "Do namespaces still make sense?"
-    form_for(@post, namespace: "namespace") do |f|
-      concat f.text_field(:title)
-      concat f.text_area(:body)
-      concat f.check_box(:secret)
-    end
-
-    expected = whole_form("/posts/123", "namespace_edit_post_123", "edit_post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
-      "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
-    end
-
-    assert_dom_equal expected, output_buffer
-  end
-
   def test_submit_with_object_as_new_record_and_locale_strings
     with_locale :submit do
       @post.persisted = false
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..4c9f84f277 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -8,11 +8,14 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
 
   def setup
     super
-    view_paths = ActionController::Base.view_paths
+
+    view_paths     = ActionController::Base.view_paths
     lookup_context = ActionView::LookupContext.new(view_paths, {}, ["test"])
-    renderer = ActionView::Renderer.new(lookup_context)
-    @view = ActionView::Base.new(renderer, {})
+    renderer       = ActionView::Renderer.new(lookup_context)
+    @view          = ActionView::Base.new(renderer, {})
+
     ActionView::LogSubscriber.attach_to :action_view
+
     unless Rails.respond_to?(:root)
       @defined_root = true
       def Rails.root; :defined_root; end # Minitest `stub` expects the method to be defined.
@@ -21,7 +24,9 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
 
   def teardown
     super
+
     ActiveSupport::LogSubscriber.log_subscribers.clear
+
     # We need to undef `root`, RenderTestCases don't want this to be defined
     Rails.instance_eval { undef :root } if @defined_root
   end
@@ -39,7 +44,7 @@ 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
@@ -103,9 +108,9 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
       set_view_cache_dependencies
       set_cache_controller
 
-      @view.render(partial: "test/cached_customer", locals: { cached_customer: Customer.new("david") })
       # Second render should hit cache.
       @view.render(partial: "test/cached_customer", locals: { cached_customer: Customer.new("david") })
+      @view.render(partial: "test/cached_customer", locals: { cached_customer: Customer.new("david") })
       wait
 
       assert_equal 2, @logger.logged(:info).size
@@ -113,6 +118,46 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
     end
   end
 
+  def test_render_uncached_outer_partial_with_inner_cached_partial_wont_mix_cache_hits_or_misses
+    Rails.stub(:root, File.expand_path(FIXTURE_LOAD_PATH)) do
+      set_view_cache_dependencies
+      set_cache_controller
+
+      @view.render(partial: "test/nested_cached_customer", locals: { cached_customer: Customer.new("Stan") })
+      wait
+      *, cached_inner, uncached_outer = @logger.logged(:info)
+      assert_match(/Rendered test\/_cached_customer\.erb (.*) \[cache miss\]/, cached_inner)
+      assert_match(/Rendered test\/_nested_cached_customer\.erb \(.*?ms\)$/, uncached_outer)
+
+      # Second render hits the cache for the _cached_customer partial. Outer template's log shouldn't be affected.
+      @view.render(partial: "test/nested_cached_customer", locals: { cached_customer: Customer.new("Stan") })
+      wait
+      *, cached_inner, uncached_outer = @logger.logged(:info)
+      assert_match(/Rendered test\/_cached_customer\.erb (.*) \[cache hit\]/, cached_inner)
+      assert_match(/Rendered test\/_nested_cached_customer\.erb \(.*?ms\)$/, uncached_outer)
+    end
+  end
+
+  def test_render_cached_outer_partial_with_cached_inner_partial
+    Rails.stub(:root, File.expand_path(FIXTURE_LOAD_PATH)) do
+      set_view_cache_dependencies
+      set_cache_controller
+
+      @view.render(partial: "test/cached_nested_cached_customer", locals: { cached_customer: Customer.new("Stan") })
+      wait
+      *, cached_inner, cached_outer = @logger.logged(:info)
+      assert_match(/Rendered test\/_cached_customer\.erb (.*) \[cache miss\]/, cached_inner)
+      assert_match(/Rendered test\/_cached_nested_cached_customer\.erb (.*) \[cache miss\]/, cached_outer)
+
+      # One render: inner partial skipped, because the outer has been cached.
+      assert_difference -> { @logger.logged(:info).size }, +1 do
+        @view.render(partial: "test/cached_nested_cached_customer", locals: { cached_customer: Customer.new("Stan") })
+        wait
+      end
+      assert_match(/Rendered test\/_cached_nested_cached_customer\.erb (.*) \[cache hit\]/, @logger.logged(:info).last)
+    end
+  end
+
   def test_render_partial_with_cache_hitted_and_missed
     Rails.stub(:root, File.expand_path(FIXTURE_LOAD_PATH)) do
       set_view_cache_dependencies
diff --git a/actionview/test/template/render_test.rb b/actionview/test/template/render_test.rb
index 3f66ab3ed3..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)
 
@@ -138,7 +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
 
@@ -160,7 +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
@@ -718,6 +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..30dc719ce6 100644
--- a/actionview/test/template/url_helper_test.rb
+++ b/actionview/test/template/url_helper_test.rb
@@ -7,8 +7,7 @@ class UrlHelperTest < ActiveSupport::TestCase
   # In those cases, we'll set up a simple mock
   attr_accessor :controller, :request
 
-  cattr_accessor :request_forgery
-  self.request_forgery = false
+  cattr_accessor :request_forgery, default: false
 
   routes = ActionDispatch::Routing::RouteSet.new
   routes.draw do
@@ -615,8 +614,8 @@ 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