From f9bea6304dfba902b1937b3bc29b1ebc2f67e55b Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Wed, 23 Jan 2019 14:19:50 -0800
Subject: [PATCH 01/10] Move templates to an anonymous subclass of AV::Base

Now we can throw away the subclass and the generated methods will get
GC'd too
---
 .../action_dispatch/middleware/debug_view.rb  |  9 ++++++++
 actionview/lib/action_view.rb                 |  1 -
 actionview/lib/action_view/base.rb            | 16 +++++++-------
 actionview/lib/action_view/lookup_context.rb  |  5 +++++
 actionview/lib/action_view/rendering.rb       | 17 ++++-----------
 actionview/test/abstract_unit.rb              |  6 ++++--
 .../activerecord/multifetch_cache_test.rb     |  4 +++-
 .../test/template/compiled_templates_test.rb  | 17 ++++++++++++---
 .../test/template/log_subscriber_test.rb      |  5 ++++-
 actionview/test/template/render_test.rb       | 21 +++++++++++++++++--
 .../test/template/streaming_render_test.rb    |  5 ++++-
 actionview/test/template/template_test.rb     |  4 +++-
 .../test/template/translation_helper_test.rb  |  5 ++++-
 13 files changed, 82 insertions(+), 33 deletions(-)

diff --git a/actionpack/lib/action_dispatch/middleware/debug_view.rb b/actionpack/lib/action_dispatch/middleware/debug_view.rb
index 5a7010a1c2..499bb1b391 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_view.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_view.rb
@@ -9,12 +9,21 @@ module ActionDispatch
   class DebugView < ActionView::Base # :nodoc:
     RESCUES_TEMPLATE_PATH = File.expand_path("templates", __dir__)
 
+    module CompiledTemplates
+    end
+
+    include CompiledTemplates
+
     def initialize(assigns)
       paths = [RESCUES_TEMPLATE_PATH]
       renderer = ActionView::Renderer.new ActionView::LookupContext.new(paths)
       super(renderer, assigns)
     end
 
+    def compiled_method_container
+      CompiledTemplates
+    end
+
     def debug_params(params)
       clean_params = params.clone
       clean_params.delete("action")
diff --git a/actionview/lib/action_view.rb b/actionview/lib/action_view.rb
index 6ff2d70e35..8cb4648a67 100644
--- a/actionview/lib/action_view.rb
+++ b/actionview/lib/action_view.rb
@@ -35,7 +35,6 @@ module ActionView
   eager_autoload do
     autoload :Base
     autoload :Context
-    autoload :CompiledTemplates, "action_view/context"
     autoload :Digestor
     autoload :Helpers
     autoload :LookupContext
diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index b143e13c96..1e58004fcf 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -11,10 +11,6 @@ require "action_view/template"
 require "action_view/lookup_context"
 
 module ActionView #:nodoc:
-  module CompiledTemplates #:nodoc:
-    # holds compiled template code
-  end
-
   # = Action View Base
   #
   # Action View templates can be written in several ways.
@@ -146,8 +142,6 @@ module ActionView #:nodoc:
   class Base
     include Helpers, ::ERB::Util, Context
 
-    include CompiledTemplates
-
     # Specify the proc used to decorate input tags that refer to attributes with errors.
     cattr_accessor :field_error_proc, default: Proc.new { |html_tag, instance| "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe }
 
@@ -186,6 +180,14 @@ module ActionView #:nodoc:
       def xss_safe? #:nodoc:
         true
       end
+
+      def with_empty_template_cache # :nodoc:
+        template_container = Module.new
+        Class.new(self) {
+          include template_container
+          define_method(:compiled_method_container) { template_container }
+        }
+      end
     end
 
     attr_reader :view_renderer
@@ -260,7 +262,7 @@ module ActionView #:nodoc:
     end
 
     def compiled_method_container
-      CompiledTemplates
+      raise NotImplementedError
     end
 
     ActiveSupport.run_load_hooks(:action_view, self)
diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index c2f6439e26..c3bb0a49fc 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -68,12 +68,17 @@ module ActionView
       end
 
       def self.clear
+        @view_context_class = nil
         @details_keys.clear
       end
 
       def self.digest_caches
         @details_keys.values
       end
+
+      def self.view_context_class(klass)
+        @view_context_class ||= klass.with_empty_template_cache
+      end
     end
 
     # Add caching behavior on top of Details.
diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index 205665a8c6..01caa82ec6 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -36,21 +36,12 @@ module ActionView
 
     module ClassMethods
       def view_context_class
-        @view_context_class ||= begin
-          supports_path = supports_path?
-          routes  = respond_to?(:_routes)  && _routes
-          helpers = respond_to?(:_helpers) && _helpers
+        klass = ActionView::LookupContext::DetailsKey.view_context_class(ActionView::Base)
 
-          Class.new(ActionView::Base) do
-            if routes
-              include routes.url_helpers(supports_path)
-              include routes.mounted_helpers
-            end
+        @view_context_class ||= build_view_context_class(klass, supports_path?, _routes, _helpers)
 
-            if helpers
-              include helpers
-            end
-          end
+        if klass.changed?(@view_context_class)
+          @view_context_class = build_view_context_class(klass, supports_path?, _routes, _helpers)
         end
       end
     end
diff --git a/actionview/test/abstract_unit.rb b/actionview/test/abstract_unit.rb
index acc2ed029b..b649b3c9dd 100644
--- a/actionview/test/abstract_unit.rb
+++ b/actionview/test/abstract_unit.rb
@@ -48,7 +48,8 @@ module RenderERBUtils
     @view ||= begin
       path = ActionView::FileSystemResolver.new(FIXTURE_LOAD_PATH)
       view_paths = ActionView::PathSet.new([path])
-      ActionView::Base.with_view_paths(view_paths)
+      view = ActionView::Base.with_empty_template_cache
+      view.with_view_paths(view_paths)
     end
   end
 
@@ -61,7 +62,8 @@ module RenderERBUtils
       ActionView::Template.handler_for_extension(:erb),
       {})
 
-    template.render(ActionView::Base.empty, {}).strip
+    view = ActionView::Base.with_empty_template_cache
+    template.render(view.empty, {}).strip
   end
 end
 
diff --git a/actionview/test/activerecord/multifetch_cache_test.rb b/actionview/test/activerecord/multifetch_cache_test.rb
index 229b4e56d0..f56168bda5 100644
--- a/actionview/test/activerecord/multifetch_cache_test.rb
+++ b/actionview/test/activerecord/multifetch_cache_test.rb
@@ -10,8 +10,10 @@ class MultifetchCacheTest < ActiveRecordTestCase
 
   def setup
     view_paths = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
 
-    @view = Class.new(ActionView::Base) do
+    @view = Class.new(ActionView::Base.with_empty_template_cache) do
       def view_cache_dependencies
         []
       end
diff --git a/actionview/test/template/compiled_templates_test.rb b/actionview/test/template/compiled_templates_test.rb
index ded4786e62..3d4561b55f 100644
--- a/actionview/test/template/compiled_templates_test.rb
+++ b/actionview/test/template/compiled_templates_test.rb
@@ -3,7 +3,18 @@
 require "abstract_unit"
 
 class CompiledTemplatesTest < ActiveSupport::TestCase
-  teardown do
+  attr_reader :view_class
+
+  def setup
+    super
+    view_paths     = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
+    @view_class = ActionView::Base.with_empty_template_cache
+  end
+
+  def teardown
+    super
     ActionView::LookupContext::DetailsKey.clear
   end
 
@@ -72,13 +83,13 @@ class CompiledTemplatesTest < ActiveSupport::TestCase
 
     def render_with_cache(*args)
       view_paths = ActionController::Base.view_paths
-      ActionView::Base.with_view_paths(view_paths, {}).render(*args)
+      view_class.with_view_paths(view_paths, {}).render(*args)
     end
 
     def render_without_cache(*args)
       path = ActionView::FileSystemResolver.new(FIXTURE_LOAD_PATH)
       view_paths = ActionView::PathSet.new([path])
-      ActionView::Base.with_view_paths(view_paths, {}).render(*args)
+      view_class.with_view_paths(view_paths, {}).render(*args)
     end
 
     def modify_template(template, content)
diff --git a/actionview/test/template/log_subscriber_test.rb b/actionview/test/template/log_subscriber_test.rb
index 9fcf80bb24..7f98207e3d 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -12,9 +12,12 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
     super
 
     view_paths     = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
+
     lookup_context = ActionView::LookupContext.new(view_paths, {}, ["test"])
     renderer       = ActionView::Renderer.new(lookup_context)
-    @view          = ActionView::Base.new(renderer, {})
+    @view          = ActionView::Base.with_empty_template_cache.new(renderer, {})
 
     ActionView::LogSubscriber.attach_to :action_view
 
diff --git a/actionview/test/template/render_test.rb b/actionview/test/template/render_test.rb
index f89d087c34..372b85a4a5 100644
--- a/actionview/test/template/render_test.rb
+++ b/actionview/test/template/render_test.rb
@@ -9,7 +9,8 @@ end
 module RenderTestCases
   def setup_view(paths)
     @assigns = { secret: "in the sauce" }
-    @view = Class.new(ActionView::Base) do
+
+    @view = Class.new(ActionView::Base.with_empty_template_cache) do
       def view_cache_dependencies; []; end
 
       def combined_fragment_cache_key(key)
@@ -17,7 +18,16 @@ module RenderTestCases
       end
     end.with_view_paths(paths, @assigns)
 
-    @controller_view = TestController.new.view_context
+    controller = TestController.new
+    view = @view
+
+    @controller_view = Class.new(controller.view_context_class) do
+      include view.compiled_method_container
+
+      define_method(:compiled_method_container) do
+        view.compiled_method_container
+      end
+    end.new(controller.view_renderer, controller.view_assigns, controller)
 
     # Reload and register danish language for testing
     I18n.backend.store_translations "da", {}
@@ -629,6 +639,8 @@ class CachedViewRenderTest < ActiveSupport::TestCase
   # Ensure view path cache is primed
   def setup
     view_paths = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
     assert_equal ActionView::OptimizedFileSystemResolver, view_paths.first.class
     setup_view(view_paths)
   end
@@ -645,6 +657,9 @@ class LazyViewRenderTest < ActiveSupport::TestCase
   # Test the same thing as above, but make sure the view path
   # is not eager loaded
   def setup
+    view_paths = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
     path = ActionView::FileSystemResolver.new(FIXTURE_LOAD_PATH)
     view_paths = ActionView::PathSet.new([path])
     assert_equal ActionView::FileSystemResolver.new(FIXTURE_LOAD_PATH), view_paths.first
@@ -704,6 +719,8 @@ class CachedCollectionViewRenderTest < ActiveSupport::TestCase
   setup do
     view_paths = ActionController::Base.view_paths
     assert_equal ActionView::OptimizedFileSystemResolver, view_paths.first.class
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
 
     ActionView::PartialRenderer.collection_cache = ActiveSupport::Cache::MemoryStore.new
 
diff --git a/actionview/test/template/streaming_render_test.rb b/actionview/test/template/streaming_render_test.rb
index dda2095013..4567ee31b4 100644
--- a/actionview/test/template/streaming_render_test.rb
+++ b/actionview/test/template/streaming_render_test.rb
@@ -8,8 +8,11 @@ end
 class SetupFiberedBase < ActiveSupport::TestCase
   def setup
     view_paths = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
+
     @assigns = { secret: "in the sauce", name: nil }
-    @view = ActionView::Base.with_view_paths(view_paths, @assigns)
+    @view = ActionView::Base.with_empty_template_cache.with_view_paths(view_paths, @assigns)
     @controller_view = TestController.new.view_context
   end
 
diff --git a/actionview/test/template/template_test.rb b/actionview/test/template/template_test.rb
index 8257d97b7c..8af6739e45 100644
--- a/actionview/test/template/template_test.rb
+++ b/actionview/test/template/template_test.rb
@@ -20,6 +20,7 @@ class TestERBTemplate < ActiveSupport::TestCase
 
   class Context < ActionView::Base
     def initialize
+      super
       @output_buffer = "original"
       @virtual_path = nil
     end
@@ -63,7 +64,8 @@ class TestERBTemplate < ActiveSupport::TestCase
   end
 
   def setup
-    @context = Context.new
+    @context = Context.with_empty_template_cache.new
+    super
   end
 
   def test_basic_template
diff --git a/actionview/test/template/translation_helper_test.rb b/actionview/test/template/translation_helper_test.rb
index d04e68e182..7094d4c7fc 100644
--- a/actionview/test/template/translation_helper_test.rb
+++ b/actionview/test/template/translation_helper_test.rb
@@ -36,7 +36,10 @@ class TranslationHelperTest < ActiveSupport::TestCase
         }
       }
     )
-    @view = ::ActionView::Base.with_view_paths(ActionController::Base.view_paths, {})
+    view_paths     = ActionController::Base.view_paths
+    view_paths.each(&:clear_cache)
+    ActionView::LookupContext.fallbacks.each(&:clear_cache)
+    @view = ::ActionView::Base.with_empty_template_cache.with_view_paths(view_paths, {})
   end
 
   teardown do

From 5b4df9d0eb295d402489465f3600576038f5762d Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Wed, 23 Jan 2019 15:44:32 -0800
Subject: [PATCH 02/10] Regenerate AV::Base subclass when DetailsKey gets
 cleared

---
 actionview/lib/action_view/base.rb      |  7 ++++++-
 actionview/lib/action_view/rendering.rb | 25 +++++++++++++++++++++++--
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index 1e58004fcf..c5d8cdd409 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -185,9 +185,14 @@ module ActionView #:nodoc:
         template_container = Module.new
         Class.new(self) {
           include template_container
-          define_method(:compiled_method_container) { template_container }
+          define_method(:compiled_method_container)           { template_container }
+          define_singleton_method(:compiled_method_container) { template_container }
         }
       end
+
+      def changed?(other) # :nodoc:
+        compiled_method_container != other.compiled_method_container
+      end
     end
 
     attr_reader :view_renderer
diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index 01caa82ec6..8246e4ba6d 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -35,14 +35,35 @@ module ActionView
     end
 
     module ClassMethods
+      def _routes
+      end
+
+      def _helpers
+      end
+
+      def build_av_class(klass, supports_path, routes, helpers)
+        Class.new(klass) do
+          if routes
+            include routes.url_helpers(supports_path)
+            include routes.mounted_helpers
+          end
+
+          if helpers
+            include helpers
+          end
+        end
+      end
+
       def view_context_class
         klass = ActionView::LookupContext::DetailsKey.view_context_class(ActionView::Base)
 
-        @view_context_class ||= build_view_context_class(klass, supports_path?, _routes, _helpers)
+        @view_context_class ||= build_av_class(klass, supports_path?, _routes, _helpers)
 
         if klass.changed?(@view_context_class)
-          @view_context_class = build_view_context_class(klass, supports_path?, _routes, _helpers)
+          @view_context_class = build_av_class(klass, supports_path?, _routes, _helpers)
         end
+
+        @view_context_class
       end
     end
 

From 7d0ce785d4d0d3c8f31eb63b653d1c5d2a2bdad7 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Wed, 23 Jan 2019 15:50:48 -0800
Subject: [PATCH 03/10] Remove finalizer and configuration

---
 actionview/lib/action_view/railtie.rb           |  8 --------
 actionview/lib/action_view/template.rb          | 15 ---------------
 guides/source/configuring.md                    |  7 -------
 .../templates/config/environments/test.rb.tt    |  3 ---
 railties/test/application/configuration_test.rb | 17 -----------------
 5 files changed, 50 deletions(-)

diff --git a/actionview/lib/action_view/railtie.rb b/actionview/lib/action_view/railtie.rb
index 12d06bf376..12bdc642d4 100644
--- a/actionview/lib/action_view/railtie.rb
+++ b/actionview/lib/action_view/railtie.rb
@@ -10,7 +10,6 @@ module ActionView
     config.action_view.embed_authenticity_token_in_remote_forms = nil
     config.action_view.debug_missing_translation = true
     config.action_view.default_enforce_utf8 = nil
-    config.action_view.finalize_compiled_template_methods = true
 
     config.eager_load_namespaces << ActionView
 
@@ -46,13 +45,6 @@ module ActionView
       end
     end
 
-    initializer "action_view.finalize_compiled_template_methods" do |app|
-      ActiveSupport.on_load(:action_view) do
-        ActionView::Template.finalize_compiled_template_methods =
-          app.config.action_view.delete(:finalize_compiled_template_methods)
-      end
-    end
-
     initializer "action_view.logger" do
       ActiveSupport.on_load(:action_view) { self.logger ||= Rails.logger }
     end
diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index 8a5407c622..69e28770eb 100644
--- a/actionview/lib/action_view/template.rb
+++ b/actionview/lib/action_view/template.rb
@@ -10,8 +10,6 @@ module ActionView
   class Template
     extend ActiveSupport::Autoload
 
-    mattr_accessor :finalize_compiled_template_methods, default: true
-
     # === Encodings in ActionView::Template
     #
     # ActionView::Template is one of a few sources of potential
@@ -118,16 +116,6 @@ module ActionView
 
     attr_reader :source, :identifier, :handler, :original_encoding, :updated_at
 
-    # This finalizer is needed (and exactly with a proc inside another proc)
-    # otherwise templates leak in development.
-    Finalizer = proc do |method_name, mod| # :nodoc:
-      proc do
-        mod.module_eval do
-          remove_possible_method method_name
-        end
-      end
-    end
-
     attr_reader :variable
 
     def initialize(source, identifier, handler, details)
@@ -337,9 +325,6 @@ module ActionView
         end
 
         mod.module_eval(source, identifier, 0)
-        if finalize_compiled_template_methods
-          ObjectSpace.define_finalizer(self, Finalizer[method_name, mod])
-        end
       end
 
       def handle_render_error(view, e)
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 2911b1f7c3..e7129dd274 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -590,13 +590,6 @@ Defaults to `'signed cookie'`.
 
 * `config.action_view.default_enforce_utf8` determines whether forms are generated with a hidden tag that forces older versions of Internet Explorer to submit forms encoded in UTF-8. This defaults to `false`.
 
-* `config.action_view.finalize_compiled_template_methods` determines
-  whether the methods on `ActionView::CompiledTemplates` that templates
-  compile themselves to are removed when template instances are
-  destroyed by the garbage collector. This helps prevent memory leaks in
-  development mode, but for large test suites, disabling this option in
-  the test environment can improve performance. This defaults to `true`.
-
 
 ### Configuring Action Mailbox
 
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
index 223aa56187..63ed3fa952 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
@@ -48,7 +48,4 @@ Rails.application.configure do
 
   # Raises error for missing translations.
   # config.action_view.raise_on_missing_translations = true
-
-  # Prevent expensive template finalization at end of test suite runs.
-  config.action_view.finalize_compiled_template_methods = false
 end
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 7006b0855f..79bf7e6fd0 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -2092,23 +2092,6 @@ module ApplicationTests
       assert_equal true, ActionView::Helpers::FormTagHelper.default_enforce_utf8
     end
 
-    test "ActionView::Template.finalize_compiled_template_methods is true by default" do
-      app "test"
-      assert_equal true, ActionView::Template.finalize_compiled_template_methods
-    end
-
-    test "ActionView::Template.finalize_compiled_template_methods can be configured via config.action_view.finalize_compiled_template_methods" do
-      app_file "config/environments/test.rb", <<-RUBY
-      Rails.application.configure do
-        config.action_view.finalize_compiled_template_methods = false
-      end
-      RUBY
-
-      app "test"
-
-      assert_equal false, ActionView::Template.finalize_compiled_template_methods
-    end
-
     test "ActiveJob::Base.return_false_on_aborted_enqueue is true by default" do
       app "development"
 

From 6dcd43b2a8a81b6131f5a569fffae6a17d337032 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Wed, 23 Jan 2019 16:11:54 -0800
Subject: [PATCH 04/10] =?UTF-8?q?=F0=9F=9A=A8=20Make=20the=20cops=20happy?=
 =?UTF-8?q?=20=F0=9F=9A=A8?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 actionview/test/template/compiled_templates_test.rb | 2 +-
 actionview/test/template/log_subscriber_test.rb     | 2 +-
 actionview/test/template/translation_helper_test.rb | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/actionview/test/template/compiled_templates_test.rb b/actionview/test/template/compiled_templates_test.rb
index 3d4561b55f..6375555bb4 100644
--- a/actionview/test/template/compiled_templates_test.rb
+++ b/actionview/test/template/compiled_templates_test.rb
@@ -7,7 +7,7 @@ class CompiledTemplatesTest < ActiveSupport::TestCase
 
   def setup
     super
-    view_paths     = ActionController::Base.view_paths
+    view_paths = ActionController::Base.view_paths
     view_paths.each(&:clear_cache)
     ActionView::LookupContext.fallbacks.each(&:clear_cache)
     @view_class = ActionView::Base.with_empty_template_cache
diff --git a/actionview/test/template/log_subscriber_test.rb b/actionview/test/template/log_subscriber_test.rb
index 7f98207e3d..4574b798d9 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -11,7 +11,7 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
   def setup
     super
 
-    view_paths     = ActionController::Base.view_paths
+    view_paths = ActionController::Base.view_paths
     view_paths.each(&:clear_cache)
     ActionView::LookupContext.fallbacks.each(&:clear_cache)
 
diff --git a/actionview/test/template/translation_helper_test.rb b/actionview/test/template/translation_helper_test.rb
index 7094d4c7fc..23fc9850c4 100644
--- a/actionview/test/template/translation_helper_test.rb
+++ b/actionview/test/template/translation_helper_test.rb
@@ -36,7 +36,7 @@ class TranslationHelperTest < ActiveSupport::TestCase
         }
       }
     )
-    view_paths     = ActionController::Base.view_paths
+    view_paths = ActionController::Base.view_paths
     view_paths.each(&:clear_cache)
     ActionView::LookupContext.fallbacks.each(&:clear_cache)
     @view = ::ActionView::Base.with_empty_template_cache.with_view_paths(view_paths, {})

From 517b96207d0e083a42b81414efa9f9b6ba300e03 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 24 Jan 2019 12:43:07 -0800
Subject: [PATCH 05/10] Pull generated methods up in to the anonymous subclass

Then we don't need the extra module.
---
 .../lib/action_dispatch/middleware/debug_view.rb      |  7 +------
 actionview/lib/action_view/base.rb                    | 11 ++++++-----
 actionview/test/template/render_test.rb               |  9 +--------
 3 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/actionpack/lib/action_dispatch/middleware/debug_view.rb b/actionpack/lib/action_dispatch/middleware/debug_view.rb
index 499bb1b391..f16484d1ea 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_view.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_view.rb
@@ -9,11 +9,6 @@ module ActionDispatch
   class DebugView < ActionView::Base # :nodoc:
     RESCUES_TEMPLATE_PATH = File.expand_path("templates", __dir__)
 
-    module CompiledTemplates
-    end
-
-    include CompiledTemplates
-
     def initialize(assigns)
       paths = [RESCUES_TEMPLATE_PATH]
       renderer = ActionView::Renderer.new ActionView::LookupContext.new(paths)
@@ -21,7 +16,7 @@ module ActionDispatch
     end
 
     def compiled_method_container
-      CompiledTemplates
+      self.class
     end
 
     def debug_params(params)
diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index c5d8cdd409..71aa68499d 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -182,11 +182,12 @@ module ActionView #:nodoc:
       end
 
       def with_empty_template_cache # :nodoc:
-        template_container = Module.new
-        Class.new(self) {
-          include template_container
-          define_method(:compiled_method_container)           { template_container }
-          define_singleton_method(:compiled_method_container) { template_container }
+        subclass = Class.new(self) {
+          # We can't implement these as self.class because subclasses will
+          # share the same template cache as superclasses, so "changed?" won't work
+          # correctly.
+          define_method(:compiled_method_container)           { subclass }
+          define_singleton_method(:compiled_method_container) { subclass }
         }
       end
 
diff --git a/actionview/test/template/render_test.rb b/actionview/test/template/render_test.rb
index 372b85a4a5..b8d8717db4 100644
--- a/actionview/test/template/render_test.rb
+++ b/actionview/test/template/render_test.rb
@@ -19,15 +19,8 @@ module RenderTestCases
     end.with_view_paths(paths, @assigns)
 
     controller = TestController.new
-    view = @view
 
-    @controller_view = Class.new(controller.view_context_class) do
-      include view.compiled_method_container
-
-      define_method(:compiled_method_container) do
-        view.compiled_method_container
-      end
-    end.new(controller.view_renderer, controller.view_assigns, controller)
+    @controller_view = controller.view_context_class.with_empty_template_cache.new(controller.view_renderer, controller.view_assigns, controller)
 
     # Reload and register danish language for testing
     I18n.backend.store_translations "da", {}

From 8fc73067e3c11810af374e886a41b9f3611a8873 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 24 Jan 2019 12:45:21 -0800
Subject: [PATCH 06/10] Rename method so it is more descriptive

---
 actionview/lib/action_view/rendering.rb | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index 8246e4ba6d..cf7d1105e0 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -41,7 +41,7 @@ module ActionView
       def _helpers
       end
 
-      def build_av_class(klass, supports_path, routes, helpers)
+      def build_view_context_class(klass, supports_path, routes, helpers)
         Class.new(klass) do
           if routes
             include routes.url_helpers(supports_path)
@@ -57,10 +57,10 @@ module ActionView
       def view_context_class
         klass = ActionView::LookupContext::DetailsKey.view_context_class(ActionView::Base)
 
-        @view_context_class ||= build_av_class(klass, supports_path?, _routes, _helpers)
+        @view_context_class ||= build_view_context_class(klass, supports_path?, _routes, _helpers)
 
         if klass.changed?(@view_context_class)
-          @view_context_class = build_av_class(klass, supports_path?, _routes, _helpers)
+          @view_context_class = build_view_context_class(klass, supports_path?, _routes, _helpers)
         end
 
         @view_context_class

From 7761ddbebb5627769cd9fa9d9f1ff5a072716b47 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 24 Jan 2019 13:50:24 -0800
Subject: [PATCH 07/10] Deprecate finalizer configuration (it doesn't do
 anything)

Revert "Remove finalizer and configuration"

This reverts commit 9e7b4a3173788ea43b11e74a4d2f69a5f1565daa.
---
 actionview/CHANGELOG.md                       |  6 ++++++
 actionview/lib/action_view/railtie.rb         | 13 ++++++++++++
 actionview/lib/action_view/template.rb        |  9 ++++++++
 .../test/application/configuration_test.rb    | 21 +++++++++++++++++++
 4 files changed, 49 insertions(+)

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index 5e17e65bde..ecc02d510b 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   ActionView::Template.finalize_compiled_template_methods is deprecated with
+    no replacement.
+
+*   config.action_view.finalize_compiled_template_methods is deprecated with
+    no replacement.
+
 *   Ensure unique DOM IDs for collection inputs with float values.
     Fixes #34974
 
diff --git a/actionview/lib/action_view/railtie.rb b/actionview/lib/action_view/railtie.rb
index 12bdc642d4..a25e1d3d02 100644
--- a/actionview/lib/action_view/railtie.rb
+++ b/actionview/lib/action_view/railtie.rb
@@ -6,10 +6,13 @@ require "rails"
 module ActionView
   # = Action View Railtie
   class Railtie < Rails::Engine # :nodoc:
+    NULL_OPTION = Object.new
+
     config.action_view = ActiveSupport::OrderedOptions.new
     config.action_view.embed_authenticity_token_in_remote_forms = nil
     config.action_view.debug_missing_translation = true
     config.action_view.default_enforce_utf8 = nil
+    config.action_view.finalize_compiled_template_methods = NULL_OPTION
 
     config.eager_load_namespaces << ActionView
 
@@ -45,6 +48,16 @@ module ActionView
       end
     end
 
+    initializer "action_view.finalize_compiled_template_methods" do |app|
+      ActiveSupport.on_load(:action_view) do
+        option = app.config.action_view.delete(:finalize_compiled_template_methods)
+
+        if option != NULL_OPTION
+          ActiveSupport::Deprecation.warn "action_view.finalize_compiled_template_methods is deprecated and has no effect"
+        end
+      end
+    end
+
     initializer "action_view.logger" do
       ActiveSupport.on_load(:action_view) { self.logger ||= Rails.logger }
     end
diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index 69e28770eb..37f476e554 100644
--- a/actionview/lib/action_view/template.rb
+++ b/actionview/lib/action_view/template.rb
@@ -2,6 +2,7 @@
 
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/kernel/singleton_class"
+require "active_support/deprecation"
 require "thread"
 require "delegate"
 
@@ -10,6 +11,14 @@ module ActionView
   class Template
     extend ActiveSupport::Autoload
 
+    def self.finalize_compiled_template_methods
+      ActiveSupport::Deprecation.warn "ActionView::Template.finalize_compiled_template_methods is deprecated and has no effect"
+    end
+
+    def self.finalize_compiled_template_methods=(_)
+      ActiveSupport::Deprecation.warn "ActionView::Template.finalize_compiled_template_methods= is deprecated and has no effect"
+    end
+
     # === Encodings in ActionView::Template
     #
     # ActionView::Template is one of a few sources of potential
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 79bf7e6fd0..37fba72ee3 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -2092,6 +2092,27 @@ module ApplicationTests
       assert_equal true, ActionView::Helpers::FormTagHelper.default_enforce_utf8
     end
 
+    test "ActionView::Template.finalize_compiled_template_methods is true by default" do
+      app "test"
+      assert_deprecated do
+        ActionView::Template.finalize_compiled_template_methods
+      end
+    end
+
+    test "ActionView::Template.finalize_compiled_template_methods can be configured via config.action_view.finalize_compiled_template_methods" do
+      app_file "config/environments/test.rb", <<-RUBY
+      Rails.application.configure do
+        config.action_view.finalize_compiled_template_methods = false
+      end
+      RUBY
+
+      app "test"
+
+      assert_deprecated do
+        ActionView::Template.finalize_compiled_template_methods
+      end
+    end
+
     test "ActiveJob::Base.return_false_on_aborted_enqueue is true by default" do
       app "development"
 

From 9aa9b6d6e12b1b900f783abc40f50e4771f55d6f Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 24 Jan 2019 13:59:26 -0800
Subject: [PATCH 08/10] Add a message to help allocate AV::Base instances

---
 actionview/lib/action_view/base.rb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index 71aa68499d..df87de4406 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -268,7 +268,11 @@ module ActionView #:nodoc:
     end
 
     def compiled_method_container
-      raise NotImplementedError
+      raise NotImplementedError, <<~msg
+        Subclasses of ActionView::Base must implement `compiled_method_container`
+        or use the class method `with_empty_template_cache` for constructing
+        an ActionView::Base subclass thata has an empty cache.
+      msg
     end
 
     ActiveSupport.run_load_hooks(:action_view, self)

From cf0dd4a71da69cf7f39da59a992f04b3c7bcbb19 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 24 Jan 2019 14:30:40 -0800
Subject: [PATCH 09/10] Fix some typos!

---
 actionview/CHANGELOG.md            | 4 ++++
 actionview/lib/action_view/base.rb | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index ecc02d510b..5e7b271fb9 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,9 +1,13 @@
 *   ActionView::Template.finalize_compiled_template_methods is deprecated with
     no replacement.
 
+    *tenderlove*
+
 *   config.action_view.finalize_compiled_template_methods is deprecated with
     no replacement.
 
+    *tenderlove*
+
 *   Ensure unique DOM IDs for collection inputs with float values.
     Fixes #34974
 
diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index df87de4406..420136d6de 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -271,7 +271,7 @@ module ActionView #:nodoc:
       raise NotImplementedError, <<~msg
         Subclasses of ActionView::Base must implement `compiled_method_container`
         or use the class method `with_empty_template_cache` for constructing
-        an ActionView::Base subclass thata has an empty cache.
+        an ActionView::Base subclass that has an empty cache.
       msg
     end
 

From 570bcdaa65987ac2f5cc84fdf83678cd5c0bb7d8 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Wed, 6 Feb 2019 16:50:06 -0800
Subject: [PATCH 10/10] Fix deprecation warnings and call super

---
 actionview/test/template/template_test.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/actionview/test/template/template_test.rb b/actionview/test/template/template_test.rb
index 8af6739e45..a069c8f2d0 100644
--- a/actionview/test/template/template_test.rb
+++ b/actionview/test/template/template_test.rb
@@ -19,7 +19,7 @@ class TestERBTemplate < ActiveSupport::TestCase
   end
 
   class Context < ActionView::Base
-    def initialize
+    def initialize(*)
       super
       @output_buffer = "original"
       @virtual_path = nil
@@ -64,7 +64,7 @@ class TestERBTemplate < ActiveSupport::TestCase
   end
 
   def setup
-    @context = Context.with_empty_template_cache.new
+    @context = Context.with_empty_template_cache.empty
     super
   end