Engine can now serve files with ActionDispatch::Static

railties/lib/rails/application/configuration.rb

@@ -11,7 +11,7 @@ class Configuration < ::Rails::Engine::Configuration
                     :encoding, :consider_all_requests_local, :dependency_loading,
                     :filter_parameters,  :log_level, :logger,
                     :preload_frameworks, :reload_plugins,
-                    :secret_token, :serve_static_assets, :session_options,
+                    :secret_token, :session_options,
                     :time_zone, :whiny_nils
 
       def initialize(*)

railties/lib/rails/engine.rb

@@ -152,13 +152,22 @@ def railties
     end
 
     def app
-      @app ||= config.middleware.build(endpoint)
+      @app ||= begin
+        config.middleware = config.middleware.merge_into(default_middleware_stack)
+        config.middleware.build(endpoint)
+      end
     end
 
     def endpoint
       self.class.endpoint || routes
     end
 
+    def default_middleware_stack
+      ActionDispatch::MiddlewareStack.new.tap do |middleware|
+        middleware.use ::ActionDispatch::Static, paths.public.to_a.first if config.serve_static_assets
+      end
+    end
+
     def call(env)
       app.call(env)
     end

railties/lib/rails/engine/configuration.rb

@@ -5,12 +5,13 @@ class Engine
     class Configuration < ::Rails::Railtie::Configuration
       attr_reader :root
       attr_writer :eager_load_paths, :autoload_once_paths, :autoload_paths
-      attr_accessor :middleware, :plugins
+      attr_accessor :middleware, :plugins, :serve_static_assets
 
       def initialize(root=nil)
         super()
         @root = root
-        @middleware = ActionDispatch::MiddlewareStack.new
+        @serve_static_assets = true
+        @middleware = Rails::Configuration::MiddlewareStackProxy.new
       end
 
       def paths

railties/lib/rails/railtie/configuration.rb

@@ -78,4 +78,4 @@ def method_missing(name, *args, &blk)
       end
     end
   end
-end
\ No newline at end of file
+end

railties/test/railties/engine_test.rb

@@ -127,5 +127,31 @@ class Engine < ::Rails::Engine
 
       assert Bukkits::Engine.config.yaffle_loaded
     end
+
+    test "engine can serve files" do
+      @plugin.write "lib/bukkits.rb", <<-RUBY
+        class Bukkits
+          class Engine < ::Rails::Engine
+            paths.public = "#{File.join(@plugin.path, "lib/bukkits/public")}"
+            config.serve_static_assets = true
+          end
+        end
+      RUBY
+
+      @plugin.write "lib/bukkits/public/omg.txt", <<-RUBY
+        OMG
+      RUBY
+
+      boot_rails
+
+      Rails::Application.routes.draw do |map|
+        mount(Bukkits::Engine => "/bukkits")
+      end
+
+      env = Rack::MockRequest.env_for("/bukkits/omg.txt")
+      response = Rails::Application.call(env)
+
+      assert_equal response[2].path, File.join(@plugin.path, "lib/bukkits/public/omg.txt")
+    end
   end
 end