Allow to change engine's loading priority with config.railties_order=

railties/lib/rails/application.rb

@@ -127,6 +127,28 @@ def env_config
       })
     end
 
+    def ordered_railties
+      @ordered_railties ||= begin
+        order = config.railties_order.map do |railtie|
+          if railtie == :main_app
+            self
+          elsif railtie.respond_to?(:instance)
+            railtie.instance
+          else
+            railtie
+          end
+        end
+
+        all = (railties.all - order)
+        all.push(self)   unless all.include?(self)
+        order.push(:all) unless order.include?(:all)
+
+        index = order.index(:all)
+        order[index] = all
+        order.reverse.flatten
+      end
+    end
+
     def initializers
       Bootstrap.initializers_for(self) +
       super +

railties/lib/rails/application/configuration.rb

@@ -10,8 +10,8 @@ class Configuration < ::Rails::Engine::Configuration
                     :dependency_loading, :filter_parameters,
                     :force_ssl, :helpers_paths, :logger, :log_tags, :preload_frameworks,
                     :reload_plugins, :secret_token, :serve_static_assets,
-                    :ssl_options, :static_cache_control, :session_options, 
-                    :time_zone, :whiny_nils
+                    :ssl_options, :static_cache_control, :session_options,
+                    :time_zone, :whiny_nils, :railties_order
 
       attr_writer :log_level
       attr_reader :encoding
@@ -35,6 +35,7 @@ def initialize(*)
         @middleware                  = app_middleware
         @generators                  = app_generators
         @cache_store                 = [ :file_store, "#{root}/tmp/cache/" ]
+        @railties_order              = [:all]
 
         @assets = ActiveSupport::OrderedOptions.new
         @assets.enabled                  = false

railties/lib/rails/engine.rb

@@ -330,6 +330,17 @@ module Rails
   #
   #   MyEngine::Engine.load_seed
   #
+  # == Loading priority
+  #
+  # In order to change engine's priority you can use config.railties_order in main application.
+  # It will affect the priority of loading views, helpers, assets and all the other files
+  # related to engine or application.
+  #
+  # Example:
+  #
+  #   # load Blog::Engine with highest priority, followed by application and other railties
+  #   config.railties_order = [Blog::Engine, :main_app, :all]
+  #
   class Engine < Railtie
     autoload :Configuration, "rails/engine/configuration"
     autoload :Railties,      "rails/engine/railties"
@@ -480,10 +491,19 @@ def routes
       @routes
     end
 
+    def ordered_railties
+      railties.all + [self]
+    end
+
     def initializers
       initializers = []
-      railties.all { |r| initializers += r.initializers }
-      initializers += super
+      ordered_railties.each do |r|
+        if r == self
+          initializers += super
+        else
+          initializers += r.initializers
+        end
+      end
       initializers
     end
 

railties/test/railties/engine_test.rb

@@ -667,6 +667,132 @@ def baz
       assert_equal expected, methods
     end
 
+    test "setting priority for engines with config.railties_order" do
+      @blog = engine "blog" do |plugin|
+        plugin.write "lib/blog.rb", <<-RUBY
+          module Blog
+            class Engine < ::Rails::Engine
+            end
+          end
+        RUBY
+      end
+
+      @plugin.write "lib/bukkits.rb", <<-RUBY
+        module Bukkits
+          class Engine < ::Rails::Engine
+            isolate_namespace Bukkits
+          end
+        end
+      RUBY
+
+      controller "main", <<-RUBY
+        class MainController < ActionController::Base
+          def foo
+            render :inline => '<%= render :partial => "shared/foo" %>'
+          end
+
+          def bar
+            render :inline => '<%= render :partial => "shared/bar" %>'
+          end
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          match "/foo" => "main#foo"
+          match "/bar" => "main#bar"
+        end
+      RUBY
+
+      @plugin.write "app/views/shared/_foo.html.erb", <<-RUBY
+        Bukkit's foo partial
+      RUBY
+
+      app_file "app/views/shared/_foo.html.erb", <<-RUBY
+        App's foo partial
+      RUBY
+
+      @blog.write "app/views/shared/_bar.html.erb", <<-RUBY
+        Blog's bar partial
+      RUBY
+
+      app_file "app/views/shared/_bar.html.erb", <<-RUBY
+        App's bar partial
+      RUBY
+
+      @plugin.write "app/assets/javascripts/foo.js", <<-RUBY
+        // Bukkit's foo js
+      RUBY
+
+      app_file "app/assets/javascripts/foo.js", <<-RUBY
+        // App's foo js
+      RUBY
+
+      @blog.write "app/assets/javascripts/bar.js", <<-RUBY
+        // Blog's bar js
+      RUBY
+
+      app_file "app/assets/javascripts/bar.js", <<-RUBY
+        // App's bar js
+      RUBY
+
+      add_to_config("config.railties_order = [:all, :main_app, Blog::Engine]")
+
+      boot_rails
+      require "#{rails_root}/config/environment"
+
+      get("/foo")
+      assert_equal "Bukkit's foo partial", last_response.body.strip
+
+      get("/bar")
+      assert_equal "App's bar partial", last_response.body.strip
+
+      get("/assets/foo.js")
+      assert_equal "// Bukkit's foo js\n;", last_response.body.strip
+
+      get("/assets/bar.js")
+      assert_equal "// App's bar js\n;", last_response.body.strip
+    end
+
+    test "railties_order adds :all with lowest priority if not given" do
+      @plugin.write "lib/bukkits.rb", <<-RUBY
+        module Bukkits
+          class Engine < ::Rails::Engine
+          end
+        end
+      RUBY
+
+      controller "main", <<-RUBY
+        class MainController < ActionController::Base
+          def foo
+            render :inline => '<%= render :partial => "shared/foo" %>'
+          end
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          match "/foo" => "main#foo"
+        end
+      RUBY
+
+      @plugin.write "app/views/shared/_foo.html.erb", <<-RUBY
+        Bukkit's foo partial
+      RUBY
+
+      app_file "app/views/shared/_foo.html.erb", <<-RUBY
+        App's foo partial
+      RUBY
+
+      add_to_config("config.railties_order = [Bukkits::Engine]")
+
+      boot_rails
+      require "#{rails_root}/config/environment"
+
+      get("/foo")
+      assert_equal "Bukkit's foo partial", last_response.body.strip
+    end
+
   private
     def app
       Rails.application