Move app initializers to sprockets railtie.

actionpack/lib/sprockets/railtie.rb

@@ -1,9 +1,40 @@
 require "sprockets"
 
+# TODO: Move this to sprockets-rails
+# If so, we can move the require to a Gemfile and remove assets.enabled
 class Sprockets::Railtie < Rails::Railtie
+  # Configure ActionController to use sprockets.
   initializer "sprockets.set_configs", :after => "action_controller.set_configs" do |app|
     ActiveSupport.on_load(:action_controller) do
       self.use_sprockets = app.config.assets.enabled
     end
   end
+
+  # We need to configure this after initialization to ensure we collect
+  # paths from all engines. This hook is invoked exactly before routes
+  # are compiled.
+  config.after_initialize do |app|
+    assets = app.config.assets
+    next unless assets.enabled
+
+    app.assets = asset_environment(app)
+    app.routes.append do
+      mount app.assets => assets.prefix
+    end
+
+    if config.action_controller.perform_caching
+      app.assets = app.assets.index
+    end
+  end
+
+  protected
+
+  def asset_environment(app)
+    assets = app.config.assets
+    env = Sprockets::Environment.new(app.root.to_s)
+    env.static_root = File.join(app.root.join("public"), assets.prefix)
+    env.paths.concat assets.paths
+    env.logger = Rails.logger
+    env
+  end
 end

railties/lib/rails/application.rb

@@ -139,15 +139,6 @@ module Rails
 
     alias :build_middleware_stack :app
 
-    def build_asset_environment
-      require 'sprockets'
-      env = Sprockets::Environment.new(root.to_s)
-      env.static_root = File.join(root.join("public"), config.assets.prefix)
-      env.paths.concat config.assets.paths
-      env.logger = Rails.logger
-      @assets = env
-    end
-
     def default_middleware_stack
       ActionDispatch::MiddlewareStack.new.tap do |middleware|
         if rack_cache = config.action_controller.perform_caching && config.action_dispatch.rack_cache

railties/lib/rails/application/finisher.rb

@@ -33,22 +33,6 @@ module Rails
         end
       end
 
-      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 :index_sprockets_environment do |app|
-        if config.assets.enabled && config.action_controller.perform_caching
-          app.assets = app.assets.index
-        end
-      end
-
       initializer :build_middleware_stack do
         build_middleware_stack
       end
@@ -69,6 +53,8 @@ module Rails
       end
 
       # Force routes to be loaded just at the end and add it to to_prepare callbacks
+      # This needs to be after the finisher hook to ensure routes added in the hook
+      # are still loaded.
       initializer :set_routes_reloader do |app|
         reloader = lambda { app.routes_reloader.execute_if_updated }
         reloader.call