Set relative url root in assets when controller isn't available for Sprockets. Fix #2435

See https://github.com/rails/sass-rails/issues/42 for details

actionpack/CHANGELOG

@@ -48,6 +48,8 @@
 
 *Rails 3.1.1 (unreleased)*
 
+* Set relative url root in assets when controller isn't available for Sprockets (eg. Sass files using asset_path). Fixes #2435 [Guillermo Iguaran]
+
 * Fixed the behavior of asset pipeline when config.assets.digest and config.assets.compile are false and requested asset isn't precompiled.
   Before the requested asset were compiled anyway ignoring that the config.assets.compile flag is false. [Guillermo Iguaran]
 

actionpack/lib/sprockets/helpers/rails_helper.rb

@@ -17,6 +17,7 @@ module Sprockets
           paths.asset_digests     = asset_digests
           paths.compile_assets    = compile_assets?
           paths.digest_assets     = digest_assets?
+          paths.relative_url_root = config.action_controller.relative_url_root
           paths
         end
       end
@@ -96,12 +97,17 @@ module Sprockets
       end
 
       class AssetPaths < ::ActionView::AssetPaths #:nodoc:
-        attr_accessor :asset_environment, :asset_prefix, :asset_digests, :compile_assets, :digest_assets
+        attr_accessor :asset_environment, :asset_prefix, :asset_digests, :compile_assets,
+                      :digest_assets, :relative_url_root
 
         class AssetNotPrecompiledError < StandardError; end
 
-        def compute_public_path(source, dir, ext=nil, include_host=true, protocol=nil)
-          super(source, asset_prefix, ext, include_host, protocol)
+        def compute_public_path(source, dir, ext = nil, include_host = true, protocol = nil)
+          public_path = super(source, asset_prefix, ext, include_host, protocol)
+          if !is_uri?(public_path) && relative_url_root
+            public_path = rewrite_relative_url_root(public_path, relative_url_root)
+          end
+          public_path
         end
 
         # Return the filesystem path for the source
@@ -149,6 +155,10 @@ module Sprockets
             source
           end
         end
+
+        def relative_url_root
+          has_request? ? super : @relative_url_root
+        end
       end
     end
   end

actionpack/test/template/sprockets_helper_test.rb

@@ -124,6 +124,13 @@ class SprocketsHelperTest < ActionView::TestCase
      asset_path("/images/logo.gif")
   end
 
+  test "asset path with relative url root when controller isn't present but relative_url_root is" do
+    @controller = nil
+    @config.action_controller.relative_url_root = "/collaboration/hieraki"
+    assert_equal "/collaboration/hieraki/images/logo.gif",
+     asset_path("/images/logo.gif")
+  end
+
   test "javascript path" do
     assert_match %r{/assets/application-[0-9a-f]+.js},
       asset_path(:application, "js")