2 files changed, 10 insertions, 7 deletions
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 696fbf6e09..9a427ebfdb 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -30,10 +30,8 @@ module ActionController
       end
     end
 
-    def build(action, app=nil, &block)
-      app  ||= block
+    def build(action, app = Proc.new)
       action = action.to_s
-      raise "MiddlewareStack#build requires an app" unless app
 
       middlewares.reverse.inject(app) do |a, middleware|
         middleware.valid?(action) ? middleware.build(a) : a
@@ -223,13 +221,18 @@ module ActionController
     # Makes the controller a Rack endpoint that runs the action in the given
     # +env+'s +action_dispatch.request.path_parameters+ key.
     def self.call(env)
-      action(env['action_dispatch.request.path_parameters'][:action]).call(env)
+      req = ActionDispatch::Request.new env
+      action(req.path_parameters[:action]).call(env)
     end
 
     # Returns a Rack endpoint for the given action name.
     def self.action(name, klass = ActionDispatch::Request)
-      middleware_stack.build(name.to_s) do |env|
-        new.dispatch(name, klass.new(env))
+      if middleware_stack.any?
+        middleware_stack.build(name) do |env|
+          new.dispatch(name, klass.new(env))
+        end
+      else
+        lambda { |env| new.dispatch(name, klass.new(env)) }
       end
     end
 
diff --git a/actionpack/lib/action_controller/metal/renderers.rb b/actionpack/lib/action_controller/metal/renderers.rb
index 29ce5abd55..46405cef55 100644
--- a/actionpack/lib/action_controller/metal/renderers.rb
+++ b/actionpack/lib/action_controller/metal/renderers.rb
@@ -78,7 +78,7 @@ module ActionController
     #     respond_to do |format|
     #       format.html
     #       format.csv { render csv: @csvable, filename: @csvable.name }
-    #     }
+    #     end
     #   end
     # To use renderers and their mime types in more concise ways, see
     # <tt>ActionController::MimeResponds::ClassMethods.respond_to</tt> and