Only add Rack::Cache to the middleware stack if config.action_controller.perform_caching is set.

railties/lib/rails/application.rb

@@ -147,9 +147,11 @@ def config
 
     def default_middleware_stack
       ActionDispatch::MiddlewareStack.new.tap do |middleware|
-        require "action_dispatch/http/rack_cache" if config.action_dispatch.rack_cache
+        rack_cache = config.action_controller.perform_caching && config.action_dispatch.rack_cache
 
-        middleware.use ::Rack::Cache, config.action_dispatch.rack_cache if config.action_dispatch.rack_cache
+        require "action_dispatch/http/rack_cache" if rack_cache
+
+        middleware.use ::Rack::Cache, rack_cache if rack_cache
         middleware.use ::ActionDispatch::Static, config.static_asset_paths if config.serve_static_assets
         middleware.use ::Rack::Lock if !config.allow_concurrency
         middleware.use ::Rack::Runtime

railties/test/application/middleware/cache_test.rb

@@ -24,7 +24,7 @@ def app(env = "production")
     end
 
     def simple_controller
-      controller :foo, <<-RUBY
+      controller :expires, <<-RUBY
         class ExpiresController < ApplicationController
           def expires_header
             expires_in 10, :public => !params[:private]
@@ -55,6 +55,20 @@ def render_conditionally(headers)
       RUBY
     end
 
+    def test_cache_is_disabled_in_dev_mode
+      simple_controller
+      app("development")
+
+      get "/expires/expires_header"
+      assert_nil last_response.headers['X-Rack-Cache']
+
+      body = last_response.body
+
+      get "/expires/expires_header"
+      assert_nil last_response.headers['X-Rack-Cache']
+      assert_not_equal body, last_response.body
+    end
+
     def test_cache_works_with_expires
       simple_controller
 

railties/test/application/middleware_test.rb

@@ -18,6 +18,33 @@ def app
     test "default middleware stack" do
       boot!
 
+      assert_equal [
+        "ActionDispatch::Static",
+        "Rack::Lock",
+        "ActiveSupport::Cache::Strategy::LocalCache",
+        "Rack::Runtime",
+        "Rails::Rack::Logger",
+        "ActionDispatch::ShowExceptions",
+        "ActionDispatch::RemoteIp",
+        "Rack::Sendfile",
+        "ActionDispatch::Callbacks",
+        "ActiveRecord::ConnectionAdapters::ConnectionManagement",
+        "ActiveRecord::QueryCache",
+        "ActionDispatch::Cookies",
+        "ActionDispatch::Session::CookieStore",
+        "ActionDispatch::Flash",
+        "ActionDispatch::ParamsParser",
+        "Rack::MethodOverride",
+        "ActionDispatch::Head",
+        "ActionDispatch::BestStandardsSupport"
+      ], middleware
+    end
+
+    test "Rack::Cache is present when action_controller.perform_caching is set" do
+      add_to_config "config.action_controller.perform_caching = true"
+
+      boot!
+
       assert_equal [
         "Rack::Cache",
         "ActionDispatch::Static",
@@ -82,24 +109,24 @@ def app
     test "insert middleware after" do
       add_to_config "config.middleware.insert_after ActionDispatch::Static, Rack::Config"
       boot!
-      assert_equal "Rack::Config", middleware.third
+      assert_equal "Rack::Config", middleware.second
     end
 
     test "RAILS_CACHE does not respond to middleware" do
       add_to_config "config.cache_store = :memory_store"
       boot!
-      assert_equal "Rack::Runtime", middleware.fourth
+      assert_equal "Rack::Runtime", middleware.third
     end
 
     test "RAILS_CACHE does respond to middleware" do
       boot!
-      assert_equal "Rack::Runtime", middleware.fifth
+      assert_equal "Rack::Runtime", middleware.fourth
     end
 
     test "insert middleware before" do
       add_to_config "config.middleware.insert_before ActionDispatch::Static, Rack::Config"
       boot!
-      assert_equal "Rack::Config", middleware.second
+      assert_equal "Rack::Config", middleware.first
     end
 
     # x_sendfile_header middleware