Don't rely on Rails.application global state in Config

railties/lib/rails/application.rb

@@ -55,10 +55,6 @@ module Rails
       @railties ||= Railties.new(config)
     end
 
-    def metal_loader
-      @metal_loader ||= MetalLoader.new
-    end
-
     def routes_reloader
       @routes_reloader ||= RoutesReloader.new
     end

railties/lib/rails/configuration.rb

@@ -50,6 +50,10 @@ module Rails
         super || name.to_s =~ config_key_regexp
       end
 
+      def metal_loader
+        @metal_loader ||= Rails::Application::MetalLoader.new
+      end
+
     private
 
       def method_missing(name, *args, &blk)
@@ -75,17 +79,17 @@ module Rails
       def default_middleware
         require 'action_dispatch'
         ActionDispatch::MiddlewareStack.new.tap do |middleware|
-          middleware.use('::ActionDispatch::Static', lambda { Rails.public_path }, :if => lambda { Rails.application.config.serve_static_assets })
-          middleware.use('::Rack::Lock', :if => lambda { !Rails.application.config.allow_concurrency })
+          middleware.use('::ActionDispatch::Static', lambda { Rails.public_path }, :if => lambda { serve_static_assets })
+          middleware.use('::Rack::Lock', :if => lambda { !allow_concurrency })
           middleware.use('::Rack::Runtime')
           middleware.use('::Rails::Rack::Logger')
-          middleware.use('::ActionDispatch::ShowExceptions', lambda { Rails.application.config.consider_all_requests_local })
-          middleware.use('::Rack::Sendfile', lambda { Rails.application.config.action_dispatch.x_sendfile_header })
-          middleware.use('::ActionDispatch::Callbacks', lambda { !Rails.application.config.cache_classes })
+          middleware.use('::ActionDispatch::ShowExceptions', lambda { consider_all_requests_local })
+          middleware.use('::Rack::Sendfile', lambda { action_dispatch.x_sendfile_header })
+          middleware.use('::ActionDispatch::Callbacks', lambda { !cache_classes })
           middleware.use('::ActionDispatch::Cookies')
           middleware.use(lambda { ActionController::Base.session_store }, lambda { ActionController::Base.session_options })
           middleware.use('::ActionDispatch::Flash', :if => lambda { ActionController::Base.session_store })
-          middleware.use(lambda { Rails.application.metal_loader.build_middleware(Rails.application.config.metals) }, :if => lambda { Rails.application.metal_loader.metals.any? })
+          middleware.use(lambda { metal_loader.build_middleware(metals) }, :if => lambda { metal_loader.metals.any? })
           middleware.use('ActionDispatch::ParamsParser')
           middleware.use('::Rack::MethodOverride')
           middleware.use('::ActionDispatch::Head')

railties/lib/rails/engine.rb

@@ -41,7 +41,7 @@ module Rails
       end
     end
 
-    delegate :middleware, :paths, :root, :to => :config
+    delegate :middleware, :paths, :metal_loader, :root, :to => :config
 
     def load_tasks
       super