Merge branch 'master' into unlock-minitest

33 files changed, 99 insertions, 85 deletions

diff --git a/actionview/lib/action_view.rb b/actionview/lib/action_view.rb
index 99c5b831b5..53a83d48f6 100644
--- a/actionview/lib/action_view.rb
+++ b/actionview/lib/action_view.rb
@@ -23,7 +23,7 @@
 
 require "active_support"
 require "active_support/rails"
-require "action_view/version"
+require_relative "action_view/version"
 
 module ActionView
   extend ActiveSupport::Autoload
diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index 5387174467..969d300bc1 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -1,11 +1,11 @@
 require "active_support/core_ext/module/attr_internal"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/ordered_options"
-require "action_view/log_subscriber"
-require "action_view/helpers"
-require "action_view/context"
-require "action_view/template"
-require "action_view/lookup_context"
+require_relative "log_subscriber"
+require_relative "helpers"
+require_relative "context"
+require_relative "template"
+require_relative "lookup_context"
 
 module ActionView #:nodoc:
   # = Action View Base
@@ -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/dependency_tracker.rb b/actionview/lib/action_view/dependency_tracker.rb
index 451eeec9d6..ee438f9311 100644
--- a/actionview/lib/action_view/dependency_tracker.rb
+++ b/actionview/lib/action_view/dependency_tracker.rb
@@ -1,5 +1,5 @@
 require "concurrent/map"
-require "action_view/path_set"
+require_relative "path_set"
 
 module ActionView
   class DependencyTracker # :nodoc:
diff --git a/actionview/lib/action_view/digestor.rb b/actionview/lib/action_view/digestor.rb
index 5ddf1ceb66..00ff36c879 100644
--- a/actionview/lib/action_view/digestor.rb
+++ b/actionview/lib/action_view/digestor.rb
@@ -1,5 +1,5 @@
 require "concurrent/map"
-require "action_view/dependency_tracker"
+require_relative "dependency_tracker"
 require "monitor"
 
 module ActionView
diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index c21fe782c6..cc8690e7bc 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -1,7 +1,7 @@
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/hash/keys"
-require "action_view/helpers/asset_url_helper"
-require "action_view/helpers/tag_helper"
+require_relative "asset_url_helper"
+require_relative "tag_helper"
 
 module ActionView
   # = Action View Asset Tag Helpers
@@ -203,13 +203,15 @@ module ActionView
       # ==== Options
       #
       # You can add HTML attributes using the +options+. The +options+ supports
-      # two additional keys for convenience and conformance:
+      # additional keys for convenience and conformance:
       #
       # * <tt>:alt</tt>  - If no alt text is given, the file name part of the
       #   +source+ is used (capitalized and without the extension)
       # * <tt>:size</tt> - Supplied as "{Width}x{Height}" or "{Number}", so "30x45" becomes
       #   width="30" and height="45", and "50" becomes width="50" and height="50".
       #   <tt>:size</tt> will be ignored if the value is not in the correct format.
+      # * <tt>:srcset</tt> - If supplied as a hash or array of <tt>[source, descriptor]</tt>
+      #   pairs, each image path will be expanded before the list is formatted as a string.
       #
       # ==== Examples
       #
@@ -227,16 +229,28 @@ module ActionView
       #   # => <img alt="Icon" class="menu_icon" src="/icons/icon.gif" />
       #   image_tag("/icons/icon.gif", data: { title: 'Rails Application' })
       #   # => <img data-title="Rails Application" src="/icons/icon.gif" />
+      #   image_tag("icon.png", srcset: { "icon_2x.png" => "2x", "icon_4x.png" => "4x" })
+      #   # => <img src="/assets/icon.png" srcset="/assets/icon_2x.png 2x, /assets/icon_4x.png 4x">
+      #   image_tag("pic.jpg", srcset: [["pic_1024.jpg", "1024w"], ["pic_1980.jpg", "1980w"]], sizes: "100vw")
+      #   # => <img src="/assets/pic.jpg" srcset="/assets/pic_1024.jpg 1024w, /assets/pic_1980.jpg 1980w" sizes="100vw">
       def image_tag(source, options = {})
         options = options.symbolize_keys
         check_for_image_tag_errors(options)
+        skip_pipeline = options.delete(:skip_pipeline)
 
-        src = options[:src] = path_to_image(source, skip_pipeline: options.delete(:skip_pipeline))
+        src = options[:src] = path_to_image(source, skip_pipeline: skip_pipeline)
 
         unless src.start_with?("cid:") || src.start_with?("data:") || src.blank?
           options[:alt] = options.fetch(:alt) { image_alt(src) }
         end
 
+        if options[:srcset] && !options[:srcset].is_a?(String)
+          options[:srcset] = options[:srcset].map do |src_path, size|
+            src_path = path_to_image(src_path, skip_pipeline: skip_pipeline)
+            "#{src_path} #{size}"
+          end.join(", ")
+        end
+
         options[:width], options[:height] = extract_dimensions(options.delete(:size)) if options[:size]
         tag("img", options)
       end
diff --git a/actionview/lib/action_view/helpers/cache_helper.rb b/actionview/lib/action_view/helpers/cache_helper.rb
index c3aecadcd6..b7c7324f31 100644
--- a/actionview/lib/action_view/helpers/cache_helper.rb
+++ b/actionview/lib/action_view/helpers/cache_helper.rb
@@ -214,8 +214,6 @@ module ActionView
         end
       end
 
-      attr_reader :cache_hit # :nodoc:
-
     private
 
       def fragment_name_with_digest(name, virtual_path)
@@ -236,10 +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/date_helper.rb b/actionview/lib/action_view/helpers/date_helper.rb
index 3f43465aa4..3fbed44f7e 100644
--- a/actionview/lib/action_view/helpers/date_helper.rb
+++ b/actionview/lib/action_view/helpers/date_helper.rb
@@ -1,5 +1,5 @@
 require "date"
-require "action_view/helpers/tag_helper"
+require_relative "tag_helper"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/date/conversions"
 require "active_support/core_ext/hash/slice"
@@ -1007,7 +1007,7 @@ module ActionView
           select_options[:disabled] = "disabled" if @options[:disabled]
           select_options[:class] = css_class_attribute(type, select_options[:class], @options[:with_css_classes]) if @options[:with_css_classes]
 
-          select_html = "\n"
+          select_html = "\n".dup
           select_html << content_tag("option".freeze, "", value: "") + "\n" if @options[:include_blank]
           select_html << prompt_option_tag(type, @options[:prompt]) + "\n" if @options[:prompt]
           select_html << select_options_as_html
@@ -1089,7 +1089,7 @@ module ActionView
         # Given an ordering of datetime components, create the selection HTML
         # and join them with their appropriate separators.
         def build_selects_from_types(order)
-          select = ""
+          select = "".dup
           first_visible = order.find { |type| !@options[:"discard_#{type}"] }
           order.reverse_each do |type|
             separator = separator(type) unless type == first_visible # don't add before first visible field
diff --git a/actionview/lib/action_view/helpers/form_helper.rb b/actionview/lib/action_view/helpers/form_helper.rb
index 672269b811..6b36c2272a 100644
--- a/actionview/lib/action_view/helpers/form_helper.rb
+++ b/actionview/lib/action_view/helpers/form_helper.rb
@@ -1,10 +1,10 @@
 require "cgi"
-require "action_view/helpers/date_helper"
-require "action_view/helpers/tag_helper"
-require "action_view/helpers/form_tag_helper"
-require "action_view/helpers/active_model_helper"
-require "action_view/model_naming"
-require "action_view/record_identifier"
+require_relative "date_helper"
+require_relative "tag_helper"
+require_relative "form_tag_helper"
+require_relative "active_model_helper"
+require_relative "../model_naming"
+require_relative "../record_identifier"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/string/output_safety"
@@ -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.
       #
@@ -2318,8 +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/form_options_helper.rb b/actionview/lib/action_view/helpers/form_options_helper.rb
index 07d4310a4e..0de3800a51 100644
--- a/actionview/lib/action_view/helpers/form_options_helper.rb
+++ b/actionview/lib/action_view/helpers/form_options_helper.rb
@@ -1,6 +1,6 @@
 require "cgi"
 require "erb"
-require "action_view/helpers/form_helper"
+require_relative "form_helper"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/array/wrap"
diff --git a/actionview/lib/action_view/helpers/form_tag_helper.rb b/actionview/lib/action_view/helpers/form_tag_helper.rb
index 9fc08b3837..c8c6632781 100644
--- a/actionview/lib/action_view/helpers/form_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/form_tag_helper.rb
@@ -1,5 +1,5 @@
 require "cgi"
-require "action_view/helpers/tag_helper"
+require_relative "tag_helper"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/module/attribute_accessors"
 
diff --git a/actionview/lib/action_view/helpers/javascript_helper.rb b/actionview/lib/action_view/helpers/javascript_helper.rb
index 22e1e74ad6..8806492572 100644
--- a/actionview/lib/action_view/helpers/javascript_helper.rb
+++ b/actionview/lib/action_view/helpers/javascript_helper.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tag_helper"
+require_relative "tag_helper"
 
 module ActionView
   module Helpers
@@ -13,8 +13,8 @@ module ActionView
         "'"     => "\\'"
       }
 
-      JS_ESCAPE_MAP["\342\200\250".force_encoding(Encoding::UTF_8).encode!] = "&#x2028;"
-      JS_ESCAPE_MAP["\342\200\251".force_encoding(Encoding::UTF_8).encode!] = "&#x2029;"
+      JS_ESCAPE_MAP["\342\200\250".dup.force_encoding(Encoding::UTF_8).encode!] = "&#x2028;"
+      JS_ESCAPE_MAP["\342\200\251".dup.force_encoding(Encoding::UTF_8).encode!] = "&#x2029;"
 
       # Escapes carriage returns and single and double quotes for JavaScript segments.
       #
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/check_box.rb b/actionview/lib/action_view/helpers/tags/check_box.rb
index 02f87fc89f..b9b988325d 100644
--- a/actionview/lib/action_view/helpers/tags/check_box.rb
+++ b/actionview/lib/action_view/helpers/tags/check_box.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tags/checkable"
+require_relative "checkable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
index 7252d4f2d9..ef37c1c342 100644
--- a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tags/collection_helpers"
+require_relative "collection_helpers"
 
 module ActionView
   module Helpers
@@ -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..c7d28905d0 100644
--- a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tags/collection_helpers"
+require_relative "collection_helpers"
 
 module ActionView
   module Helpers
@@ -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/radio_button.rb b/actionview/lib/action_view/helpers/tags/radio_button.rb
index 43dbd32083..782263ac5b 100644
--- a/actionview/lib/action_view/helpers/tags/radio_button.rb
+++ b/actionview/lib/action_view/helpers/tags/radio_button.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tags/checkable"
+require_relative "checkable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/select.rb b/actionview/lib/action_view/helpers/tags/select.rb
index 9ff7e54e4f..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
diff --git a/actionview/lib/action_view/helpers/tags/text_area.rb b/actionview/lib/action_view/helpers/tags/text_area.rb
index 31e3a9e9b1..1058fdf55f 100644
--- a/actionview/lib/action_view/helpers/tags/text_area.rb
+++ b/actionview/lib/action_view/helpers/tags/text_area.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tags/placeholderable"
+require_relative "placeholderable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/text_field.rb b/actionview/lib/action_view/helpers/tags/text_field.rb
index 613cade7b3..1d55105587 100644
--- a/actionview/lib/action_view/helpers/tags/text_field.rb
+++ b/actionview/lib/action_view/helpers/tags/text_field.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tags/placeholderable"
+require_relative "placeholderable"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/translation_helper.rb b/actionview/lib/action_view/helpers/translation_helper.rb
index 47ed41a129..b10cfadaed 100644
--- a/actionview/lib/action_view/helpers/translation_helper.rb
+++ b/actionview/lib/action_view/helpers/translation_helper.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/tag_helper"
+require_relative "tag_helper"
 require "active_support/core_ext/string/access"
 require "i18n/exceptions"
 
@@ -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
@@ -96,7 +95,7 @@ module ActionView
           raise e if raise_error
 
           keys = I18n.normalize_keys(e.locale, e.key, e.options[:scope])
-          title = "translation missing: #{keys.join('.')}"
+          title = "translation missing: #{keys.join('.')}".dup
 
           interpolations = options.except(:default, :scope)
           if interpolations.any?
diff --git a/actionview/lib/action_view/helpers/url_helper.rb b/actionview/lib/action_view/helpers/url_helper.rb
index a6857101b9..644e1e4391 100644
--- a/actionview/lib/action_view/helpers/url_helper.rb
+++ b/actionview/lib/action_view/helpers/url_helper.rb
@@ -1,4 +1,4 @@
-require "action_view/helpers/javascript_helper"
+require_relative "javascript_helper"
 require "active_support/core_ext/array/access"
 require "active_support/core_ext/hash/keys"
 require "active_support/core_ext/string/output_safety"
@@ -552,7 +552,10 @@ module ActionView
         request_uri = url_string.index("?") || check_parameters ? request.fullpath : request.path
         request_uri = URI.parser.unescape(request_uri).force_encoding(Encoding::BINARY)
 
-        url_string.chomp!("/") if url_string.start_with?("/") && url_string != "/"
+        if url_string.start_with?("/") && url_string != "/"
+          url_string.chomp!("/")
+          request_uri.chomp!("/")
+        end
 
         if %r{^\w+://}.match?(url_string)
           url_string == "#{request.protocol}#{request.host_with_port}#{request_uri}"
diff --git a/actionview/lib/action_view/layouts.rb b/actionview/lib/action_view/layouts.rb
index ab8409e8d0..b62fde30e8 100644
--- a/actionview/lib/action_view/layouts.rb
+++ b/actionview/lib/action_view/layouts.rb
@@ -1,4 +1,4 @@
-require "action_view/rendering"
+require_relative "rendering"
 require "active_support/core_ext/module/remove_method"
 
 module ActionView
diff --git a/actionview/lib/action_view/log_subscriber.rb b/actionview/lib/action_view/log_subscriber.rb
index d03e1a51b8..c8623f1e9f 100644
--- a/actionview/lib/action_view/log_subscriber.rb
+++ b/actionview/lib/action_view/log_subscriber.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require "active_support/log_subscriber"
 
 module ActionView
@@ -14,7 +15,7 @@ module ActionView
 
     def render_template(event)
       info do
-        message = "  Rendered #{from_rails_root(event.payload[:identifier])}"
+        message = "  Rendered #{from_rails_root(event.payload[:identifier])}".dup
         message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
         message << " (#{event.duration.round(1)}ms)"
       end
@@ -22,10 +23,10 @@ module ActionView
 
     def render_partial(event)
       info do
-        message = "  Rendered #{from_rails_root(event.payload[:identifier])}"
+        message = "  Rendered #{from_rails_root(event.payload[:identifier])}".dup
         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
@@ -73,16 +74,17 @@ 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
 
     def log_rendering_start(payload)
       info do
-        message = "  Rendering #{from_rails_root(payload[:identifier])}"
+        message = "  Rendering #{from_rails_root(payload[:identifier])}".dup
         message << " within #{from_rails_root(payload[:layout])}" if payload[:layout]
         message
       end
diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index f385a7cd04..ce5493c01b 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -1,7 +1,7 @@
 require "concurrent/map"
 require "active_support/core_ext/module/remove_method"
 require "active_support/core_ext/module/attribute_accessors"
-require "action_view/template/resolver"
+require_relative "template/resolver"
 
 module ActionView
   # = Action View Lookup Context
@@ -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/record_identifier.rb b/actionview/lib/action_view/record_identifier.rb
index 48bea315a9..6805513347 100644
--- a/actionview/lib/action_view/record_identifier.rb
+++ b/actionview/lib/action_view/record_identifier.rb
@@ -1,5 +1,5 @@
 require "active_support/core_ext/module"
-require "action_view/model_naming"
+require_relative "model_naming"
 
 module ActionView
   # RecordIdentifier encapsulates methods used by various ActionView helpers
diff --git a/actionview/lib/action_view/renderer/partial_renderer.rb b/actionview/lib/action_view/renderer/partial_renderer.rb
index 647b15ea94..77f5084686 100644
--- a/actionview/lib/action_view/renderer/partial_renderer.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer.rb
@@ -1,5 +1,5 @@
 require "concurrent/map"
-require "action_view/renderer/partial_renderer/collection_caching"
+require_relative "partial_renderer/collection_caching"
 
 module ActionView
   class PartialIteration
@@ -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 847256ac78..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
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/rendering.rb b/actionview/lib/action_view/rendering.rb
index cf18562c45..9bee76a1f7 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -1,4 +1,4 @@
-require "action_view/view_paths"
+require_relative "view_paths"
 
 module ActionView
   # This is a class to fix I18n global state. Whenever you provide I18n.locale during a request,
diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index b0e2f1e54e..80b294dc3d 100644
--- a/actionview/lib/action_view/template.rb
+++ b/actionview/lib/action_view/template.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/kernel/singleton_class"
 require "thread"
@@ -282,7 +283,7 @@ module ActionView
 
         # Make sure that the resulting String to be eval'd is in the
         # encoding of the code
-        source = <<-end_src
+        source = <<-end_src.dup
           def #{method_name}(local_assigns, output_buffer)
             _old_virtual_path, @virtual_path = @virtual_path, #{@virtual_path.inspect};_old_output_buffer = @output_buffer;#{locals_code};#{code}
           ensure
@@ -329,12 +330,12 @@ module ActionView
         locals = locals.grep(/\A@?(?![A-Z0-9])(?:[[:alnum:]_]|[^\0-\177])+\z/)
 
         # Double assign to suppress the dreaded 'assigned but unused variable' warning
-        locals.each_with_object("") { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
+        locals.each_with_object("".dup) { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
       end
 
       def method_name
         @method_name ||= begin
-          m = "_#{identifier_method_name}__#{@identifier.hash}_#{__id__}"
+          m = "_#{identifier_method_name}__#{@identifier.hash}_#{__id__}".dup
           m.tr!("-".freeze, "_".freeze)
           m
         end
diff --git a/actionview/lib/action_view/template/resolver.rb b/actionview/lib/action_view/template/resolver.rb
index d3905b5f23..0ccf398d9a 100644
--- a/actionview/lib/action_view/template/resolver.rb
+++ b/actionview/lib/action_view/template/resolver.rb
@@ -1,7 +1,7 @@
 require "pathname"
 require "active_support/core_ext/class"
 require "active_support/core_ext/module/attribute_accessors"
-require "action_view/template"
+require_relative "../template"
 require "thread"
 require "concurrent/map"
 
@@ -14,7 +14,7 @@ module ActionView
       alias_method :partial?, :partial
 
       def self.build(name, prefix, partial)
-        virtual = ""
+        virtual = "".dup
         virtual << "#{prefix}/" unless prefix.empty?
         virtual << (partial ? "_#{name}" : name)
         new name, prefix, partial, virtual
@@ -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 80403799ab..424a86ba3e 100644
--- a/actionview/lib/action_view/test_case.rb
+++ b/actionview/lib/action_view/test_case.rb
@@ -104,7 +104,7 @@ module ActionView
         # empty string ensures buffer has UTF-8 encoding as
         # new without arguments returns ASCII-8BIT encoded buffer like String#new
         @output_buffer = ActiveSupport::SafeBuffer.new ""
-        @rendered = ""
+        @rendered = "".dup
 
         make_test_case_available_to_view!
         say_no_to_protect_against_forgery!
diff --git a/actionview/lib/action_view/testing/resolvers.rb b/actionview/lib/action_view/testing/resolvers.rb
index 3188526b63..5e853311e6 100644
--- a/actionview/lib/action_view/testing/resolvers.rb
+++ b/actionview/lib/action_view/testing/resolvers.rb
@@ -1,4 +1,4 @@
-require "action_view/template/resolver"
+require_relative "../template/resolver"
 
 module ActionView #:nodoc:
   # Use FixtureResolver in your tests to simulate the presence of files on the
@@ -20,7 +20,7 @@ module ActionView #:nodoc:
     private
 
       def query(path, exts, _, _)
-        query = ""
+        query = "".dup
         EXTENSIONS.each_key do |ext|
           query << "(" << exts[ext].map { |e| e && Regexp.escape(".#{e}") }.join("|") << "|)"
         end