I18n support for plugins

Rails will now automatically add locale files found in any engine's locale
directory to the I18n.load_path (i.e. files that match the glob pattern
"config/locales/**/*.{rb,yml}" relative to engine directories).

[#2325 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

railties/CHANGELOG

@@ -1,5 +1,7 @@
 *Edge*
 
+* I18n support for plugins.  #2325 [Antonio Tapiador, Sven Fuchs]
+
 * Ruby 1.9: use UTF-8 for default internal and external encodings.  [Jeremy Kemper]
 
 * Added db/seeds.rb as a default file for storing seed data for the database. Can be loaded with rake db:seed (or created alongside the db with db:setup). (This is also known as the "Stop Putting Gawd Damn Seed Data In Your Migrations" feature) [DHH]

railties/lib/rails/plugin.rb

@@ -71,6 +71,10 @@ def routed?
       File.exist?(routing_file)
     end
 
+    # Returns true if there is any localization file in locale_path
+    def localized?
+      locale_files.any?
+    end
 
     def view_path
       File.join(directory, 'app', 'views')
@@ -87,6 +91,14 @@ def metal_path
     def routing_file
       File.join(directory, 'config', 'routes.rb')
     end
+
+    def locale_path
+      File.join(directory, 'config', 'locales')
+    end
+
+    def locale_files
+      Dir[ File.join(locale_path, '*.{rb,yml}') ]
+    end
 
 
     private

railties/lib/rails/plugin/loader.rb

@@ -73,6 +73,7 @@ def engine_metal_paths
         def configure_engines
           if engines.any?
             add_engine_routing_configurations
+            add_engine_locales
             add_engine_controller_paths
             add_engine_view_paths
           end
@@ -84,6 +85,12 @@ def add_engine_routing_configurations
           end
         end
 
+        def add_engine_locales
+          # reverse it such that the last engine can overwrite translations from the first, like with routes
+          locale_files = engines.select(&:localized?).collect(&:locale_files).reverse.flatten
+          I18n.load_path += locale_files - I18n.load_path
+        end
+
         def add_engine_controller_paths
           ActionController::Routing.controller_paths += engines.collect {|engine| engine.controller_path }
         end

railties/test/fixtures/plugins/engines/engine/config/locales/en.yml

@@ -0,0 +1,2 @@
+en:
+  hello: "Hello from Engine"

railties/test/initializer_test.rb

@@ -406,6 +406,7 @@ def test_config_defaults_and_settings_should_be_added_to_i18n_defaults
      File.expand_path(File.dirname(__FILE__) + "/../../actionpack/lib/action_view/locale/en.yml"),
      File.expand_path(File.dirname(__FILE__) + "/../../activemodel/lib/active_model/locale/en.yml"),
      File.expand_path(File.dirname(__FILE__) + "/../../activerecord/lib/active_record/locale/en.yml"),
+     File.expand_path(File.dirname(__FILE__) + "/../../railties/test/fixtures/plugins/engines/engine/config/locales/en.yml"),
      "my/test/locale.yml",
      "my/other/locale.yml" ], I18n.load_path.collect { |path| path =~ /\.\./ ? File.expand_path(path) : path }
   end

railties/test/plugin_loader_test.rb

@@ -156,6 +156,14 @@ def test_should_add_all_load_paths_from_a_plugin_to_LOAD_PATH_array
     plugin_load_paths.each { |path| assert $LOAD_PATH.include?(path) }
   end
 
+  def test_should_add_locale_files_to_I18n_load_path
+    only_load_the_following_plugins! [:engine]
+
+    @loader.send :add_engine_locales
+
+    assert I18n.load_path.include?(File.join(plugin_fixture_path('engines/engine'), 'config', 'locales', 'en.yml'))
+  end
+
 
   private
     def reset_load_path!