1 files changed, 27 insertions, 9 deletions

diff --git a/actionpack/lib/sprockets/helpers/rails_helper.rb b/actionpack/lib/sprockets/helpers/rails_helper.rb
index f218ab3416..7d709de9e2 100644
--- a/actionpack/lib/sprockets/helpers/rails_helper.rb
+++ b/actionpack/lib/sprockets/helpers/rails_helper.rb
@@ -16,7 +16,10 @@ module Sprockets
           else
             config.default_asset_host_protocol ||= :relative
           end
-          RailsHelper::AssetPaths.new(config, controller)
+          paths = RailsHelper::AssetPaths.new(config, controller)
+          paths.asset_environment = asset_environment
+          paths.asset_prefix      = asset_prefix
+          paths
         end
       end
 
@@ -76,9 +79,28 @@ module Sprockets
           params[:debug_assets] == 'true'
       end
 
+      # Override to specify an alternative prefix for asset path generation.
+      # When combined with a custom +asset_environment+, this can be used to
+      # implement themes that can take advantage of the asset pipeline.
+      #
+      # If you only want to change where the assets are mounted, refer to
+      # +config.assets.prefix+ instead.
+      def asset_prefix
+        Rails.application.config.assets.prefix
+      end
+
+      # Override to specify an alternative asset environment for asset
+      # path generation. The environment should already have been mounted
+      # at the prefix returned by +asset_prefix+.
+      def asset_environment
+        Rails.application.assets
+      end
+
       class AssetPaths < ::ActionView::AssetPaths #:nodoc:
-        def compute_public_path(source, dir, ext=nil, include_host=true, protocol = nil)
-          super(source, Rails.application.config.assets.prefix, ext, include_host, protocol)
+        attr_accessor :asset_environment, :asset_prefix
+
+        def compute_public_path(source, dir, ext=nil, include_host=true, protocol=nil)
+          super(source, asset_prefix, ext, include_host, protocol)
         end
 
         # Return the filesystem path for the source
@@ -90,14 +112,14 @@ module Sprockets
           source = source.to_s
           return nil if is_uri?(source)
           source = rewrite_extension(source, nil, ext)
-          assets[source]
+          asset_environment[source]
         end
 
         def rewrite_asset_path(source, dir)
           if source[0] == ?/
             source
           else
-            assets.path(source, performing_caching?, dir)
+            asset_environment.path(source, performing_caching?, dir)
           end
         end
 
@@ -109,10 +131,6 @@ module Sprockets
           end
         end
 
-        def assets
-          Rails.application.assets
-        end
-
         # When included in Sprockets::Context, we need to ask the top-level config as the controller is not available
         def performing_caching?
           config.action_controller.present? ? config.action_controller.perform_caching : config.perform_caching