Properly reload routes defined in class definition

Sometimes it's easier to define routes inside Engine or
Application class definition (e.g. one file applications). The
problem with such case is that if there is a plugin that
has config/routes.rb file, it will trigger routes reload on application.
Since routes definition for application is not in config/routes.rb
file routes_reloader will fail to reload application's routes
properly. With this commit you can pass routes definition as a block
to routes method, which will allow to properly reload it:

class MyApp::Application < Rails::Application
  routes do
    resources :users
  end
end

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -1,6 +1,7 @@
 require 'rack/mount'
 require 'forwardable'
 require 'active_support/core_ext/object/to_query'
+require 'active_support/core_ext/hash/slice'
 
 module ActionDispatch
   module Routing

railties/lib/rails/application.rb

@@ -85,14 +85,25 @@ module Rails
     end
 
     def reload_routes!
+      routes_to_reload.each do |_routes, draw_block|
         _routes = self.routes
         _routes.disable_clear_and_finalize = true
         _routes.clear!
+        _routes.draw(&draw_block) if draw_block
+      end
       routes_reloader.paths.each { |path| load(path) }
+      routes_to_reload.each do |_routes, draw_block|
         ActiveSupport.on_load(:action_controller) { _routes.finalize! }
+      end
     ensure
+      routes_to_reload.each do |_routes, draw_block|
         _routes.disable_clear_and_finalize = false
       end
+    end
+
+    def routes_to_reload
+      @routes_to_reload ||= {}
+    end
 
     def initialize!
       raise "Application has been already initialized." if @initialized

railties/lib/rails/engine.rb

@@ -399,8 +399,10 @@ module Rails
       }
     end
 
-    def routes
+    def routes(&block)
       @routes ||= ActionDispatch::Routing::RouteSet.new
+      self.routes_draw_block = block if block_given?
+      @routes
     end
 
     def initializers
@@ -447,6 +449,7 @@ module Rails
     end
 
     initializer :add_routing_paths do |app|
+      app.routes_to_reload[self.routes] = routes_draw_block
       paths.config.routes.to_a.each do |route|
         app.routes_reloader.paths.unshift(route) if File.exists?(route)
       end
@@ -499,6 +502,8 @@ module Rails
     end
 
   protected
+    attr_accessor :routes_draw_block
+
     def find_root_with_flag(flag, default=nil)
       root_path = self.class.called_from
 

railties/test/railties/engine_test.rb

@@ -663,5 +663,45 @@ module RailtiesTest
 
       assert_equal AppTemplate._railtie, AppTemplate::Engine
     end
+
+    test "properly reload routes" do
+      # when routes are inside application class definition
+      # they should not be reloaded when engine's routes
+      # file has changed
+      add_to_config <<-RUBY
+        routes do
+          mount lambda{|env| [200, {}, ["foo"]]} => "/foo"
+          mount Bukkits::Engine => "/bukkits"
+        end
+      RUBY
+
+      FileUtils.rm(File.join(app_path, "config/routes.rb"))
+
+      @plugin.write "config/routes.rb", <<-RUBY
+        Bukkits::Engine.routes.draw do
+          mount lambda{|env| [200, {}, ["bar"]]} => "/bar"
+        end
+      RUBY
+
+      @plugin.write "lib/bukkits.rb", <<-RUBY
+        module Bukkits
+          class Engine < ::Rails::Engine
+            namespace(Bukkits)
+          end
+        end
+      RUBY
+
+      require 'rack/test'
+      extend Rack::Test::Methods
+
+      boot_rails
+
+      require "#{rails_root}/config/environment"
+      get "/foo"
+      assert_equal "foo", last_response.body
+
+      get "/bukkits/bar"
+      assert_equal "bar", last_response.body
+    end
   end
 end