Use precompiled assets if present

lib/premailer-rails3/css_loaders.rb

@@ -37,10 +37,11 @@ module AssetPipelineLoader
       def load(path)
         if assets_enabled?
           file = file_name(path)
-          if asset = Rails.application.assets.find_asset(file)
-            asset.to_s
-          else
+          asset = read_asset_from_pipeline(file)
+          if asset.blank?
             request_and_unzip(file)
+          else
+            asset
           end
         end
       end
@@ -49,6 +50,11 @@ def assets_enabled?
         Rails.configuration.assets.enabled rescue false
       end
 
+      def assets_precompiled?
+        # If on-the-fly asset compilation is disabled, we must be precompiling assets.
+        !Rails.configuration.assets.compile rescue false
+      end
+
       def file_name(path)
         if path == :default
           'email.css'
@@ -58,6 +64,17 @@ def file_name(path)
         end
       end
 
+      def read_asset_from_pipeline(file)
+        if assets_precompiled?
+          # Read the precompiled asset
+          asset_path = ActionController::Base.helpers.asset_path(file)
+          File.read(File.join(Rails.public_path, asset_path))
+        else
+          # This will compile and return the asset
+          Rails.application.assets.find_asset(file).to_s
+        end
+      end
+
       def request_and_unzip(file)
         url = [
           Rails.configuration.action_controller.asset_host,

spec/premailer-rails3/css_helper_spec.rb

@@ -127,13 +127,15 @@ def css_for_doc(doc)
     end
 
     context 'when Rails asset pipeline is used' do
+
       before {
         Rails.configuration.stubs(:assets).returns(
           stub(
             :enabled => true,
             :prefix  => '/assets'
           )
         )
+        PremailerRails::CSSLoaders::AssetPipelineLoader.stubs(:assets_precompiled?).returns(false)
       }
 
       it 'should load email.css when the default CSS is requested' do
@@ -201,6 +203,20 @@ def css_for_doc(doc)
           ).should == 'content of base.css'
         end
       end
+
+      context 'when assets are precompiled' do
+        before {
+          PremailerRails::CSSLoaders::AssetPipelineLoader.stubs(:assets_precompiled?).returns(true)
+        }
+
+        it 'should load precompiled assets from the filesystem' do
+          File.expects(:read) \
+              .with('RAILS_ROOT/public/somewhere/on/the/disk/precompiled.css') \
+              .returns('content of compiled css')
+
+          load_css('precompiled.css').should == 'content of compiled css'
+        end
+      end
     end
 
     context 'when static stylesheets are used' do

spec/spec_helper.rb

@@ -1,3 +1,4 @@
+require 'stubs/action_controller'
 require 'stubs/action_mailer'
 require 'stubs/rails'
 require 'stubs/hassle'

spec/stubs/action_controller.rb

@@ -0,0 +1,14 @@
+# ActionController::Base.helpers.asset_path(file)
+module ActionController
+  module FakeHelpers
+    def self.asset_path(file)
+      'somewhere/on/the/disk/' + file
+    end
+  end
+
+  module Base
+    def self.helpers
+      FakeHelpers
+    end
+  end
+end

spec/stubs/rails.rb

@@ -57,6 +57,10 @@ def logger
     Logger
   end
 
+  def public_path
+    File.join(root, 'public')
+  end
+
   def root
     'RAILS_ROOT'
   end