Merge pull request #29559 from kirs/eager-load-controller-actions

Eager load controller actions to reduce response time of the first request

actionmailer/lib/action_mailer/railtie.rb

@@ -58,6 +58,12 @@ class Railtie < Rails::Railtie # :nodoc:
       end
     end
 
+    initializer "action_mailer.eager_load_actions" do
+      ActiveSupport.on_load(:after_initialize) do
+        ActionMailer::Base.descendants.each(&:action_methods) if config.eager_load
+      end
+    end
+
     config.after_initialize do |app|
       options = app.config.action_mailer
 

actionpack/lib/action_controller/railtie.rb

@@ -79,5 +79,11 @@ class Railtie < Rails::Railtie #:nodoc:
         end
       end
     end
+
+    initializer "action_controller.eager_load_actions" do
+      ActiveSupport.on_load(:after_initialize) do
+        ActionController::Metal.descendants.each(&:action_methods) if config.eager_load
+      end
+    end
   end
 end

railties/test/application/configuration_test.rb

@@ -238,6 +238,66 @@ def change
       assert_instance_of Pathname, Rails.public_path
     end
 
+    test "does not eager load controller actions in development" do
+      app_file "app/controllers/posts_controller.rb", <<-RUBY
+        class PostsController < ActionController::Base
+          def index;end
+          def show;end
+        end
+      RUBY
+
+      app "development"
+
+      assert_nil PostsController.instance_variable_get(:@action_methods)
+    end
+
+    test "eager loads controller actions in production" do
+      app_file "app/controllers/posts_controller.rb", <<-RUBY
+        class PostsController < ActionController::Base
+          def index;end
+          def show;end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        config.eager_load = true
+        config.cache_classes = true
+      RUBY
+
+      app "production"
+
+      assert_equal %w(index show).to_set, PostsController.instance_variable_get(:@action_methods)
+    end
+
+    test "does not eager load mailer actions in development" do
+      app_file "app/mailers/posts_mailer.rb", <<-RUBY
+        class PostsMailer < ActionMailer::Base
+          def noop_email;end
+        end
+      RUBY
+
+      app "development"
+
+      assert_nil PostsMailer.instance_variable_get(:@action_methods)
+    end
+
+    test "eager loads mailer actions in production" do
+      app_file "app/mailers/posts_mailer.rb", <<-RUBY
+        class PostsMailer < ActionMailer::Base
+          def noop_email;end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        config.eager_load = true
+        config.cache_classes = true
+      RUBY
+
+      app "production"
+
+      assert_equal %w(noop_email).to_set, PostsMailer.instance_variable_get(:@action_methods)
+    end
+
     test "initialize an eager loaded, cache classes app" do
       add_to_config <<-RUBY
         config.eager_load = true