Get rid of static_paths method and instead configure paths for ActionDispatch::Static in initializers

railties/lib/rails/application.rb

@@ -145,25 +145,9 @@ module Rails
 
   protected
 
-    def static_paths
-      @static_paths ||= begin
-        static_paths = ActiveSupport::OrderedHash.new
-        static_paths["/"] = paths.public.to_a.first
-
-        railties.all do |railtie|
-          if railtie.config.respond_to?(:asset_path) && railtie.config.asset_path
-            public_path = railtie.config.paths.public.to_a.first
-            static_paths[railtie.config.asset_path % ""] = public_path if File.exists?(public_path)
-          end
-        end
-
-        static_paths
-      end
-    end
-
     def default_middleware_stack
       ActionDispatch::MiddlewareStack.new.tap do |middleware|
-        middleware.use ::ActionDispatch::Static, static_paths if config.serve_static_assets
+        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
         middleware.use ::Rails::Rack::Logger

railties/lib/rails/application/configuration.rb

@@ -37,6 +37,10 @@ module Rails
         super(value)
       end
 
+      def compiled_asset_path
+        "/"
+      end
+
       def encoding=(value)
         @encoding = value
         if "ruby".encoding_aware?

railties/lib/rails/engine.rb

@@ -428,6 +428,13 @@ module Rails
     initializer :default_asset_path do
       config.asset_path = "/#{engine_name}%s" unless config.asset_path
     end
+
+    initializer :append_asset_paths do
+      public_path = config.paths.public.to_a.first
+      if config.compiled_asset_path && File.exist?(public_path)
+        config.static_asset_paths[config.compiled_asset_path] = public_path
+      end
+    end
   protected
     def find_root_with_flag(flag, default=nil)
       root_path = self.class.called_from

railties/lib/rails/engine/configuration.rb

@@ -55,6 +55,10 @@ module Rails
       def autoload_paths
         @autoload_paths ||= paths.autoload_paths
       end
+
+      def compiled_asset_path
+        asset_path % "" if asset_path
+      end
     end
   end
 end

railties/lib/rails/railtie/configuration.rb

@@ -5,6 +5,7 @@ module Rails
     class Configuration
       def initialize
         @@options ||= {}
+        @@static_asset_paths = ActiveSupport::OrderedHash.new
       end
 
       # This allows you to modify the application's middlewares from Engines.
@@ -65,6 +66,13 @@ module Rails
         super || @@options.key?(name.to_sym)
       end
 
+      # static_asset_paths is a Hash containing asset_paths
+      # with associated public folders, like:
+      # { "/" => "/app/public", "/my_engine" => "app/engines/my_engine/public" }
+      def static_asset_paths
+        @@static_asset_paths
+      end
+
     private
 
       def method_missing(name, *args, &blk)

railties/test/railties/engine_test.rb

@@ -287,6 +287,7 @@ module RailtiesTest
 
       @plugin.write "public/bukkits.html", "/bukkits/bukkits.html"
       app_file "public/app.html", "/app.html"
+      app_file "public/bukkits/file_from_app.html", "/bukkits/file_from_app.html"
 
       boot_rails
 
@@ -297,6 +298,10 @@ module RailtiesTest
       env = Rack::MockRequest.env_for("/bukkits/bukkits.html")
       response = Rails.application.call(env)
       assert_equal response[2].path, File.join(@plugin.path, "public/bukkits.html")
+
+      env = Rack::MockRequest.env_for("/bukkits/file_from_app.html")
+      response = Rails.application.call(env)
+      assert_equal response[2].path, File.join(app_path, "public/bukkits/file_from_app.html")
     end
 
     test "shared engine should include application's helpers" do