Booya, sprockets now works from Engines.

Gemfile

@@ -12,6 +12,7 @@ gem "rack", :git => "git://github.com/rack/rack.git"
 gem "rack-test", :git => "git://github.com/brynary/rack-test.git"
 
 gem "sprockets", :git => "git://github.com/sstephenson/sprockets.git"
+gem "coffee-script"
 
 gem "rake",  ">= 0.8.7"
 gem "mocha", ">= 0.9.8"
@@ -30,6 +31,7 @@ platforms :mri_18 do
   gem "system_timer"
   gem "ruby-debug", ">= 0.10.3"
   gem 'ruby-prof'
+  gem "json"
 end
 
 platforms :mri_19 do

railties/lib/rails/application.rb

@@ -50,6 +50,7 @@ module Rails
       end
     end
 
+    attr_accessor :assets
     delegate :default_url_options, :default_url_options=, :to => :routes
 
     # This method is called just after an application inherits from Rails::Application,
@@ -116,8 +117,6 @@ module Rails
       self
     end
 
-    alias :build_middleware_stack :app
-
     def env_config
       @env_config ||= super.merge({
         "action_dispatch.parameter_filter" => config.filter_parameters,
@@ -137,42 +136,19 @@ module Rails
       @config ||= Application::Configuration.new(find_root_with_flag("config.ru", Dir.pwd))
     end
 
-    def assets
-      @assets ||= build_asset_environment
-    end
-    attr_writer :assets
+  protected
+
+    alias :build_middleware_stack :app
 
     def build_asset_environment
-      return unless config.assets.enabled
       require 'sprockets'
       env = Sprockets::Environment.new(root.to_s)
       env.static_root = File.join(root.join("public"), config.assets.prefix)
-      env
+      env.paths.concat config.assets.paths
+      env.logger = Rails.logger
+      @assets = env
     end
 
-    initializer :add_sprockets_paths do |app|
-      if config.assets.enabled
-        paths = [
-          "app/assets/javascripts",
-          "app/assets/stylesheets",
-          "vendor/assets/javascripts",
-          "vendor/assets/stylesheets",
-          "vendor/plugins/*/app/javascripts",
-          "vendor/plugins/*/app/stylesheets",
-          "vendor/plugins/*/javascripts",
-          "vendor/plugins/*/stylesheets"
-        ] + config.assets.paths
-
-        paths.each do |pattern|
-          Dir[app.root.join(pattern)].each do |dir|
-            app.assets.paths << dir
-          end
-        end
-      end
-    end
-
-  protected
-
     def default_asset_path
       nil
     end
@@ -239,4 +215,4 @@ module Rails
       require "rails/console/helpers"
     end
   end
-end
+end

railties/lib/rails/application/finisher.rb

@@ -36,18 +36,13 @@ module Rails
       initializer :add_sprockets_route do |app|
         assets = config.assets
         if assets.enabled
+          build_asset_environment
           app.routes.append do
             mount app.assets => assets.prefix
           end
         end
       end
 
-      initializer :set_sprockets_logger do |app|
-        if config.assets.enabled
-          app.assets.logger = Rails.logger
-        end
-      end
-
       initializer :index_sprockets_environment do |app|
         if config.assets.enabled && config.action_controller.perform_caching
           app.assets = app.assets.index

railties/lib/rails/engine.rb

@@ -518,6 +518,11 @@ module Rails
       end
     end
 
+    initializer :append_app_assets_path do |app|
+      app.config.assets.paths.unshift *paths["vendor/assets"].existent
+      app.config.assets.paths.unshift *paths["app/assets"].existent
+    end
+
     initializer :prepend_helpers_path do |app|
       if !isolated? || (app == self)
         app.config.helpers_paths.unshift(*paths["app/helpers"].existent)

railties/lib/rails/engine/configuration.rb

@@ -40,6 +40,7 @@ module Rails
         @paths ||= begin
           paths = Rails::Paths::Root.new(@root)
           paths.add "app",                 :eager_load => true, :glob => "*"
+          paths.add "app/assets",          :glob => "*"
           paths.add "app/controllers",     :eager_load => true
           paths.add "app/helpers",         :eager_load => true
           paths.add "app/models",          :eager_load => true
@@ -59,6 +60,7 @@ module Rails
           paths.add "public/javascripts"
           paths.add "public/stylesheets"
           paths.add "vendor",              :load_path => true
+          paths.add "vendor/assets",       :glob => "*"
           paths.add "vendor/plugins"
           paths
         end

railties/test/railties/engine_test.rb

@@ -1,8 +1,7 @@
 require "isolation/abstract_unit"
 require "railties/shared_tests"
-require 'stringio'
-require 'rack/test'
-require 'rack/file'
+require "stringio"
+require "rack/test"
 
 module RailtiesTest
   class EngineTest < Test::Unit::TestCase

railties/test/railties/shared_tests.rb

@@ -48,6 +48,18 @@ module RailtiesTest
       end
     end
 
+    def test_serving_sprockets_assets
+      @plugin.write "app/assets/javascripts/engine.js.coffee", "square = (x) -> x * x"
+
+      boot_rails
+      require 'rack/test'
+      require 'coffee_script'
+      extend Rack::Test::Methods
+
+      get "/assets/engine.js"
+      assert_match "square = function(x) {", last_response.body
+    end
+
     def test_copying_migrations
       @plugin.write "db/migrate/1_create_users.rb", <<-RUBY
         class CreateUsers < ActiveRecord::Migration