Add asset helpers to facilitate generating asset urls via the asset p…

…ipeline.

README.markdown

@@ -44,6 +44,22 @@ The [list of supported options](http://sass-lang.com/docs/yardoc/file.SASS_REFER
   files (containing mixins and variables) because it is difficult to control the
   cascade ordering for imports that contain styles using this approach.
 
+* **Asset Helpers**. When using the asset pipeline, paths to assets must be rewritten.
+  When referencing assets use the following asset helpers:
+
+  * `asset_path($relative-asset-path, $asset-class)` - Returns a string to the asset.
+    For example: `asset_path("rails.png", image)` becomes `"/assets/rails.png"`
+  * `asset_url($relative-asset-path, $asset-class)` - Returns url reference to the asset.
+
+    For example: `asset_url("rails.png", image)` becomes `url(/assets/rails.png)`
+  * As a convenience, for each of the following asset classes there are
+    corresponding `_path` and `_url` helpers:
+    image, font, video, audio, javascript, stylesheet.
+
+    For example: `image_url("rails.png")` becomes `url(/assets/rails.png)` and
+    `image_path("rails.png")` becomes `"/assets/rails.png"`.
+
+
 ## Running Tests
 
     $ bundle install

lib/sass/rails.rb

@@ -7,6 +7,7 @@ module Rails
 require 'sass/rails/logger'
 require 'sass/rails/railtie'
 require 'sass/rails/monkey_patches'
+require 'sass/rails/helpers'
 require 'sass/rails/importer'
 require 'sass/rails/template_handlers'
 require 'sass/rails/version'

lib/sass/rails/helpers.rb

@@ -0,0 +1,38 @@
+module Sass
+  module Rails
+    module Helpers
+
+      def asset_path(asset, kind)
+        Sass::Script::String.new(public_path(asset.value, kind.value), true)
+      end
+
+      def asset_url(asset, kind)
+        Sass::Script::String.new(%Q{url(#{public_path(asset.value, kind.value)})})
+      end
+
+      [:image, :font, :video, :audio, :javascript, :stylesheet].each do |asset_class|
+        class_eval %Q{
+          def #{asset_class}_path(asset)
+            asset_path(asset, Sass::Script::String.new("#{asset_class}"))
+          end
+          def #{asset_class}_url(asset)
+            asset_url(asset, Sass::Script::String.new("#{asset_class}"))
+          end
+        }, __FILE__, __LINE__ - 7
+      end
+
+    protected
+      def public_path(asset, kind)
+        options[:custom][:resolver].public_path(asset, kind.pluralize)
+      end
+    end
+  end
+end
+
+module Sass
+  module Script
+    module Functions
+      include Sass::Rails::Helpers
+    end
+  end
+end

lib/sass/rails/template_handlers.rb

@@ -57,7 +57,10 @@ def sass_options(scope)
         :line => line,
         :syntax => syntax,
         :importer => importer,
-        :load_paths => load_paths
+        :load_paths => load_paths,
+        :custom => {
+          :resolver => Resolver.new(scope)
+        }
       )
     end
 

test/fixtures/scss_project/app/assets/stylesheets/application.css.scss

@@ -8,3 +8,9 @@
   color: yellow;
   @include background-from-partial(red);
 }
+
+.rails {
+  asset-path: asset-path("rails.png", image);
+  asset-url: asset-url("rails.png", image);
+  image-url: image-url("rails.png");
+}

test/sass_rails_test.rb

@@ -54,6 +54,12 @@ class SassRailsTest < Sass::Rails::TestCase
     assert_match css_output, /plain-old-css/
     assert_match css_output, /another-plain-old-css/
   end
+  test "sass asset paths work" do
+    css_output = sprockets_render("scss_project", "application.css.scss")
+    assert_match css_output, %r{asset-path:\s*"/assets/rails.png"}
+    assert_match css_output, %r{asset-url:\s*url\(/assets/rails.png\)}
+    assert_match css_output, %r{image-url:\s*url\(/assets/rails.png\)}
+  end
   test "css compressor compresses" do
     assert_equal "div{color:red}\n", Sass::Rails::CssCompressor.new.compress(<<CSS)
 div {