Add config.action_controller.include behavior to plugins.

railties/lib/rails/configuration.rb

 require 'active_support/ordered_options'
 
 module Rails
+  # Create a Plugin::Options from ActiveSuppot::OrderedOptions,
+  # which support the following syntax:
+  #
+  #   controller.action_controller.include FooBar
+  #
+  class Plugin::Options < ActiveSupport::OrderedOptions #:nodoc:
+    attr_reader :includes
+
+    def initialize(*args)
+      @includes = []
+      super
+    end
+
+    def include(*args)
+      @includes.concat(args)
+    end
+  end
+
   # Temporarily separate the plugin configuration class from the main
   # configuration class while this bit is being cleaned up.
   class Plugin::Configuration
@@ -16,7 +34,7 @@ def initialize(base = nil)
         @options    = base.options.dup
         @middleware = base.middleware.dup
       else
-        @options    = Hash.new { |h,k| h[k] = ActiveSupport::OrderedOptions.new }
+        @options    = Hash.new { |h,k| h[k] = Rails::Plugin::Options.new }
         @middleware = ActionDispatch::MiddlewareStack.new
       end
     end

railties/lib/rails/plugin.rb

@@ -25,6 +25,24 @@ def self.config
       Configuration.default
     end
 
+    # Creates an initializer which includes all given modules to the given class.
+    #
+    #   module Rails
+    #     class ActionController < Rails::Plugin
+    #       plugin_name :action_controller
+    #       include_modules_in "ActionController::Base"
+    #     end
+    #   end
+    #
+    def self.include_modules_in(klass, from=plugin_name)
+      self.initializer :"#{from}.include_modules" do |app|
+        klass = klass.constantize if klass.is_a?(String)
+        app.config.send(from).includes.each do |mod|
+          klass.send(:include, mod.is_a?(String) ? mod.constantize : mod)
+        end
+      end
+    end
+
     class Vendored < Plugin
       def self.all(list, paths)
         plugins = []

railties/test/plugins/configuration_test.rb

@@ -8,6 +8,10 @@ def setup
       require "rails"
     end
 
+    module Bar; end
+    module Baz; end
+    module All; end
+
     test "config is available to plugins" do
       class Foo < Rails::Plugin ; end
       assert_nil Foo.config.action_controller.foo
@@ -24,6 +28,18 @@ class Foo < Rails::Plugin ; config.foo.greetings = "hello" ; end
       assert_equal "hello", AppTemplate::Application.config.foo.greetings
     end
 
+    test "plugin configurations allow modules to be given" do
+      class Foo < Rails::Plugin ; config.foo.include(Bar, Baz) ; end
+      assert_equal [Bar, Baz], Foo.config.foo.includes
+    end
+
+    test "plugin includes given modules in given class" do
+      class Foo < Rails::Plugin ; config.foo.include(Bar, "PluginsTest::ConfigurationTest::Baz") ; include_modules_in All ; end
+      Foo.new.run_initializers(Foo)
+      assert All.ancestors.include?(Bar)
+      assert All.ancestors.include?(Baz)
+    end
+
     test "plugin config merges are deep" do
       class Foo < Rails::Plugin ; config.foo.greetings = 'hello' ; end
       class MyApp < Rails::Application