Read digests of assets from manifest.yml if config.assets.manifest is on

3 files changed, 31 insertions, 2 deletions

diff --git a/actionpack/lib/sprockets/assets.rake b/actionpack/lib/sprockets/assets.rake
index 5698f22080..7ee82ee530 100644
--- a/actionpack/lib/sprockets/assets.rake
+++ b/actionpack/lib/sprockets/assets.rake
@@ -19,7 +19,8 @@ namespace :assets do
 
       config = Rails.application.config
       env    = Rails.application.assets
-      target = Rails.root.join("public#{config.assets.prefix}")
+      target = Pathname.new(File.join(Rails.public_path, config.assets.prefix))
+      manifest = {}
 
       if env.respond_to?(:each_logical_path)
         config.assets.precompile.each do |path|
@@ -31,6 +32,7 @@ namespace :assets do
             end
 
             if asset = env.find_asset(logical_path)
+              manifest[logical_path] = asset.digest_path
               filename = target.join(asset.digest_path)
               mkdir_p filename.dirname
               asset.write_to(filename)
@@ -44,6 +46,12 @@ namespace :assets do
         assets << {:to => target}
         env.precompile(*assets)
       end
+
+      if config.assets.manifest
+        File.open("#{target}/manifest.yml", 'w') do |f|
+          YAML.dump(manifest, f)
+        end
+      end
     end
   end
 
diff --git a/actionpack/lib/sprockets/helpers/rails_helper.rb b/actionpack/lib/sprockets/helpers/rails_helper.rb
index 062aa4dae5..8e7eb182fd 100644
--- a/actionpack/lib/sprockets/helpers/rails_helper.rb
+++ b/actionpack/lib/sprockets/helpers/rails_helper.rb
@@ -14,6 +14,7 @@ module Sprockets
           paths = RailsHelper::AssetPaths.new(config, controller)
           paths.asset_environment = asset_environment
           paths.asset_prefix      = asset_prefix
+          paths.asset_digests     = asset_digests
           paths
         end
       end
@@ -76,6 +77,10 @@ module Sprockets
         Rails.application.config.assets.prefix
       end
 
+      def asset_digests
+        Rails.application.config.assets.digests
+      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+.
@@ -84,7 +89,9 @@ module Sprockets
       end
 
       class AssetPaths < ::ActionView::AssetPaths #:nodoc:
-        attr_accessor :asset_environment, :asset_prefix
+        attr_accessor :asset_environment, :asset_prefix, :asset_digests
+
+        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)
@@ -103,6 +110,14 @@ module Sprockets
         end
 
         def digest_for(logical_path)
+          if asset_digests && (digest = asset_digests[logical_path])
+            return digest
+          end
+
+          if digest.nil? && Rails.application.config.assets.precompile_only
+            raise AssetNotPrecompiledError
+          end
+
           if asset = asset_environment[logical_path]
             return asset.digest_path
           end
diff --git a/actionpack/lib/sprockets/railtie.rb b/actionpack/lib/sprockets/railtie.rb
index c21bf57935..680cb980ff 100644
--- a/actionpack/lib/sprockets/railtie.rb
+++ b/actionpack/lib/sprockets/railtie.rb
@@ -26,6 +26,12 @@ module Sprockets
         end
       end
 
+      if config.assets.manifest
+        if File.exist?(path = File.join(Rails.public_path, config.assets.prefix, "manifest.yml"))
+          config.assets.digests = YAML.load_file(path)
+        end
+      end
+
       ActiveSupport.on_load(:action_view) do
         include ::Sprockets::Helpers::RailsHelper