A few changes were done in this commit:

* Added :autoload to engines path API and redefine usage to be in sync with 6f83a5036d8a9c3f8ed7;
* Do not autoload code in *lib* for applications (now you need to explicitly require them). This makes an application behave closer to an engine (code in lib is still autoloaded for plugins);
* Always autoload code in app/ for engines and plugins. This makes engines behave closer to an application and should allow us to get rid of the unloadable hack required when controllers inside engines inherit from ApplicationController;

railties/lib/rails/application.rb

@@ -28,7 +28,7 @@ module Rails
   # Besides providing the same configuration as Rails::Engine and Rails::Railtie,
   # the application object has several specific configurations, for example
   # "allow_concurrency", "cache_classes", "consider_all_requests_local", "filter_parameters",
-  # "logger", "reload_engines", "reload_plugins" and so forth.
+  # "logger", "reload_plugins" and so forth.
   #
   # Check Rails::Application::Configuration to see them all.
   #
@@ -217,10 +217,5 @@ module Rails
     def initialize_generators
       require "rails/generators"
     end
-
-    # Application is always reloadable when config.cache_classes is false.
-    def reloadable?(app)
-      true
-    end
   end
 end

railties/lib/rails/application/configuration.rb

@@ -10,7 +10,7 @@ module Rails
       attr_accessor :allow_concurrency, :cache_classes, :cache_store,
                     :encoding, :consider_all_requests_local, :dependency_loading,
                     :filter_parameters,  :log_level, :logger, :middleware,
-                    :plugins, :preload_frameworks, :reload_engines, :reload_plugins,
+                    :plugins, :preload_frameworks, :reload_plugins,
                     :secret_token, :serve_static_assets, :session_options,
                     :time_zone, :whiny_nils
 
@@ -59,7 +59,7 @@ module Rails
           if File.exists?("#{root}/test/mocks/#{Rails.env}")
             ActiveSupport::Deprecation.warn "\"Rails.root/test/mocks/#{Rails.env}\" won't be added " <<
               "automatically to load paths anymore in future releases"
-            paths.mocks_path  "test/mocks", :load_path => true, :glob => Rails.env
+            paths.mocks_path  "test/mocks", :autoload => true, :glob => Rails.env
           end
 
           paths

railties/lib/rails/engine.rb

@@ -142,7 +142,7 @@ module Rails
 
     # Add configured load paths to ruby load paths and remove duplicates.
     initializer :set_load_path, :before => :bootstrap_hook do
-      config.autoload_paths.reverse_each do |path|
+      _all_load_paths.reverse_each do |path|
         $LOAD_PATH.unshift(path) if File.directory?(path)
       end
       $LOAD_PATH.uniq!
@@ -154,16 +154,12 @@ module Rails
     # This needs to be an initializer, since it needs to run once
     # per engine and get the engine as a block parameter
     initializer :set_autoload_paths, :before => :bootstrap_hook do |app|
-      ActiveSupport::Dependencies.autoload_paths.unshift(*config.autoload_paths)
+      ActiveSupport::Dependencies.autoload_paths.unshift(*_all_autoload_paths)
-
+      ActiveSupport::Dependencies.autoload_once_paths.unshift(*config.autoload_once_paths)
-      if reloadable?(app)
-        ActiveSupport::Dependencies.autoload_once_paths.unshift(*config.autoload_once_paths)
-      else
-        ActiveSupport::Dependencies.autoload_once_paths.unshift(*config.autoload_paths)
-      end
 
       # Freeze so future modifications will fail rather than do nothing mysteriously
       config.autoload_paths.freeze
+      config.eager_load_paths.freeze
       config.autoload_once_paths.freeze
     end
 
@@ -195,7 +191,6 @@ module Rails
       ActiveSupport.on_load(:action_controller) do
         prepend_view_path(views)
       end
-
       ActiveSupport.on_load(:action_mailer) do
         prepend_view_path(views)
       end
@@ -214,8 +209,12 @@ module Rails
 
   protected
 
-    def reloadable?(app)
+    def _all_autoload_paths
-      app.config.reload_engines
+      @_all_autoload_paths ||= (config.autoload_paths + config.eager_load_paths + config.autoload_once_paths).uniq
+    end
+
+    def _all_load_paths
+      @_all_load_paths ||= (config.paths.load_paths + _all_autoload_paths).uniq
     end
   end
 end

railties/lib/rails/engine/configuration.rb

@@ -42,11 +42,11 @@ module Rails
       end
 
       def autoload_once_paths
-        @autoload_once_paths ||= paths.load_once
+        @autoload_once_paths ||= paths.autoload_once
       end
 
       def autoload_paths
-        @autoload_paths ||= paths.load_paths
+        @autoload_paths ||= paths.autoload_paths
       end
     end
   end

railties/lib/rails/paths.rb

@@ -25,9 +25,7 @@ module Rails
 
       def initialize(path)
         raise if path.is_a?(Array)
-
         @children = {}
-
         @path = path
         @root = self
         @all_paths = []
@@ -38,14 +36,18 @@ module Rails
         @all_paths
       end
 
-      def load_once
+      def autoload_once
-        filter_by(:load_once?)
+        filter_by(:autoload_once?)
       end
 
       def eager_load
         filter_by(:eager_load?)
       end
 
+      def autoload_paths
+        filter_by(:autoload?)
+      end
+
       def load_paths
         filter_by(:load_path?)
       end
@@ -61,15 +63,17 @@ module Rails
     protected
 
       def filter_by(constraint)
-        all_paths.map do |path|
+        all = []
+        all_paths.each do |path|
           if path.send(constraint)
             paths  = path.paths
             paths -= path.children.values.map { |p| p.send(constraint) ? [] : p.paths }.flatten
-            paths
+            all.concat(paths)
-          else
-            []
           end
-        end.flatten.uniq.select { |p| File.exists?(p) }
+        end
+        all.uniq!
+        all.reject! { |p| !File.exists?(p) }
+        all
       end
     end
 
@@ -80,15 +84,16 @@ module Rails
       attr_accessor :glob
 
       def initialize(root, *paths)
-        @options  = paths.last.is_a?(::Hash) ? paths.pop : {}
+        options   = paths.last.is_a?(::Hash) ? paths.pop : {}
         @children = {}
         @root     = root
         @paths    = paths.flatten
-        @glob     = @options.delete(:glob)
+        @glob     = options[:glob]
 
-        @load_once  = @options[:load_once]
+        autoload_once! if options[:autoload_once]
-        @eager_load = @options[:eager_load]
+        eager_load!    if options[:eager_load]
-        @load_path  = @options[:load_path] || @eager_load || @load_once
+        autoload!      if options[:autoload]
+        load_path!     if options[:load_path]
 
         @root.all_paths << self
       end
@@ -111,24 +116,30 @@ module Rails
         @paths.concat paths
       end
 
-      def load_once!
+      def autoload_once!
-        @load_once = true
+        @autoload_once = true
-        @load_path = true
       end
 
-      def load_once?
+      def autoload_once?
-        @load_once
+        @autoload_once
       end
 
       def eager_load!
         @eager_load = true
-        @load_path  = true
       end
 
       def eager_load?
         @eager_load
       end
 
+      def autoload!
+        @autoload = true
+      end
+
+      def autoload?
+        @autoload
+      end
+
       def load_path!
         @load_path = true
       end

railties/lib/rails/plugin.rb

@@ -61,6 +61,16 @@ module Rails
       @config ||= Engine::Configuration.new
     end
 
+    initializer :handle_lib_autoload, :before => :set_load_path do |app|
+      paths = if app.config.reload_plugins
+        config.autoload_paths
+      else
+        config.autoload_once_paths
+      end
+
+      paths.concat config.paths.lib.to_a
+    end
+
     initializer :load_init_rb, :before => :load_config_initializers do |app|
       files = %w(rails/init.rb init.rb).map { |path| File.expand_path path, root }
       if initrb = files.find { |path| File.file? path }
@@ -77,11 +87,5 @@ module Rails
         raise "\"#{name}\" is a Railtie/Engine and cannot be installed as plugin"
       end
     end
-
-  protected
-
-    def reloadable?(app)
-      app.config.reload_plugins
-    end
   end
 end

railties/test/paths_test.rb

@@ -120,36 +120,36 @@ class PathsTest < ActiveSupport::TestCase
 
   test "it is possible to add a path that should be loaded only once" do
     @root.app = "/app"
-    @root.app.load_once!
+    @root.app.autoload_once!
-    assert @root.app.load_once?
+    assert @root.app.autoload_once?
-    assert @root.load_once.include?(@root.app.paths.first)
+    assert @root.autoload_once.include?(@root.app.paths.first)
   end
 
   test "it is possible to add a path without assignment and specify it should be loaded only once" do
-    @root.app "/app", :load_once => true
+    @root.app "/app", :autoload_once => true
-    assert @root.app.load_once?
+    assert @root.app.autoload_once?
-    assert @root.load_once.include?("/app")
+    assert @root.autoload_once.include?("/app")
   end
 
   test "it is possible to add multiple paths without assignment and specify it should be loaded only once" do
-    @root.app "/app", "/app2", :load_once => true
+    @root.app "/app", "/app2", :autoload_once => true
-    assert @root.app.load_once?
+    assert @root.app.autoload_once?
-    assert @root.load_once.include?("/app")
+    assert @root.autoload_once.include?("/app")
-    assert @root.load_once.include?("/app2")
+    assert @root.autoload_once.include?("/app2")
   end
 
-  test "making a path load_once more than once only includes it once in @root.load_once" do
+  test "making a path autoload_once more than once only includes it once in @root.load_once" do
     @root.app = "/app"
-    @root.app.load_once!
+    @root.app.autoload_once!
-    @root.app.load_once!
+    @root.app.autoload_once!
-    assert_equal 1, @root.load_once.select {|p| p == @root.app.paths.first }.size
+    assert_equal 1, @root.autoload_once.select {|p| p == @root.app.paths.first }.size
   end
 
-  test "paths added to a load_once path should be added to the load_once collection" do
+  test "paths added to a load_once path should be added to the autoload_once collection" do
     @root.app = "/app"
-    @root.app.load_once!
+    @root.app.autoload_once!
     @root.app << "/app2"
-    assert_equal 2, @root.load_once.size
+    assert_equal 2, @root.autoload_once.size
   end
 
   test "it is possible to mark a path as eager" do
@@ -173,11 +173,11 @@ class PathsTest < ActiveSupport::TestCase
   end
 
   test "it is possible to create a path without assignment and mark it both as eager and load once" do
-    @root.app "/app", :eager_load => true, :load_once => true
+    @root.app "/app", :eager_load => true, :autoload_once => true
     assert @root.app.eager_load?
-    assert @root.app.load_once?
+    assert @root.app.autoload_once?
     assert @root.eager_load.include?("/app")
-    assert @root.load_once.include?("/app")
+    assert @root.autoload_once.include?("/app")
   end
 
   test "making a path eager more than once only includes it once in @root.eager_paths" do
@@ -218,16 +218,16 @@ class PathsTest < ActiveSupport::TestCase
     assert_equal ["/app"], @root.load_paths
   end
 
-  test "adding a path to the eager paths also adds it to the load path" do
+  test "a path can be marked as autoload path" do
     @root.app = "app"
-    @root.app.eager_load!
+    @root.app.autoload!
-    assert_equal ["/foo/bar/app"], @root.load_paths
+    @root.app.models = "app/models"
+    assert_equal ["/foo/bar/app"], @root.autoload_paths
   end
 
-  test "adding a path to the load once paths also adds it to the load path" do
+  test "a path can be marked as autoload on creation" do
-    @root.app = "app"
+    @root.app "/app", :autoload => true
-    @root.app.load_once!
+    assert @root.app.autoload?
-    assert_equal ["/foo/bar/app"], @root.load_paths
+    assert_equal ["/app"], @root.autoload_paths
   end
-
 end

railties/test/railties/engine_test.rb

@@ -20,10 +20,6 @@ module RailtiesTest
       end
     end
 
-    def reload_config
-      :reload_engines
-    end
-
     test "Rails::Engine itself does not respond to config" do
       boot_rails
       assert !Rails::Engine.respond_to?(:config)

railties/test/railties/plugin_test.rb

@@ -15,10 +15,6 @@ module RailtiesTest
       end
     end
 
-    def reload_config
-      :reload_plugins
-    end
-
     test "Rails::Plugin itself does not respond to config" do
       boot_rails
       assert !Rails::Plugin.respond_to?(:config)
@@ -37,6 +33,32 @@ module RailtiesTest
       assert_equal "Bukkits", Bukkits.name
     end
 
+    test "plugin gets added to dependency list" do
+      boot_rails
+      assert_equal "Another", Another.name
+    end
+
+    test "plugin constants get reloaded if config.reload_plugins is set to true" do
+      add_to_config <<-RUBY
+        config.reload_plugins = true
+      RUBY
+
+      boot_rails
+
+      assert_equal "Another", Another.name
+      ActiveSupport::Dependencies.clear
+      @plugin.delete("lib/another.rb")
+      assert_raises(NameError) { Another }
+    end
+
+    test "plugin constants are not reloaded by default" do
+      boot_rails
+      assert_equal "Another", Another.name
+      ActiveSupport::Dependencies.clear
+      @plugin.delete("lib/another.rb")
+      assert_nothing_raised { Another }
+    end
+
     test "it loads the plugin's init.rb file" do
       boot_rails
       assert_equal "loaded", BUKKITS

railties/test/railties/shared_tests.rb

@@ -10,51 +10,25 @@ module RailtiesTest
       @app ||= Rails.application
     end
 
-    def test_plugin_puts_its_lib_directory_on_load_path
+    def test_puts_its_lib_directory_on_load_path
       boot_rails
       require "another"
       assert_equal "Another", Another.name
     end
 
-    def test_plugin_paths_get_added_to_as_dependency_list
+    def test_puts_its_models_directory_on_autoload_path
-      boot_rails
-      assert_equal "Another", Another.name
-    end
-
-    def test_plugins_constants_are_not_reloaded_by_default
-      boot_rails
-      assert_equal "Another", Another.name
-      ActiveSupport::Dependencies.clear
-      @plugin.delete("lib/another.rb")
-      assert_nothing_raised { Another }
-    end
-
-    def test_plugin_constants_get_reloaded_if_config_reload_plugins
-      add_to_config <<-RUBY
-        config.#{reload_config} = true
-      RUBY
-
-      boot_rails
-
-      assert_equal "Another", Another.name
-      ActiveSupport::Dependencies.clear
-      @plugin.delete("lib/another.rb")
-      assert_raises(NameError) { Another }
-    end
-
-    def test_plugin_puts_its_models_directory_on_load_path
       @plugin.write "app/models/my_bukkit.rb", "class MyBukkit ; end"
       boot_rails
       assert_nothing_raised { MyBukkit }
     end
 
-    def test_plugin_puts_its_controllers_directory_on_the_load_path
+    def test_puts_its_controllers_directory_on_autoload_path
       @plugin.write "app/controllers/bukkit_controller.rb", "class BukkitController ; end"
       boot_rails
       assert_nothing_raised { BukkitController }
     end
 
-    def test_plugin_adds_its_views_to_view_paths
+    def test_adds_its_views_to_view_paths
       @plugin.write "app/controllers/bukkit_controller.rb", <<-RUBY
         class BukkitController < ActionController::Base
           def index
@@ -72,7 +46,7 @@ module RailtiesTest
       assert_equal "Hello bukkits\n", response[2].body
     end
 
-    def test_plugin_adds_its_views_to_view_paths_with_lower_proriority
+    def test_adds_its_views_to_view_paths_with_lower_proriority_than_app_ones
       @plugin.write "app/controllers/bukkit_controller.rb", <<-RUBY
         class BukkitController < ActionController::Base
           def index
@@ -91,7 +65,7 @@ module RailtiesTest
       assert_equal "Hi bukkits\n", response[2].body
     end
 
-    def test_plugin_adds_helpers_to_controller_views
+    def test_adds_helpers_to_controller_views
       @plugin.write "app/controllers/bukkit_controller.rb", <<-RUBY
         class BukkitController < ActionController::Base
           def index
@@ -116,11 +90,10 @@ module RailtiesTest
       assert_equal "Hello bukkits\n", response[2].body
     end
 
-    def test_plugin_eager_load_any_path_under_app
+    def test_autoload_any_path_under_app
       @plugin.write "app/anything/foo.rb", <<-RUBY
         module Foo; end
       RUBY
-
       boot_rails
       assert Foo
     end
@@ -269,7 +242,7 @@ YAML
       assert_equal "Rendered from namespace", last_response.body
     end
 
-    def test_plugin_initializers
+    def test_initializers
       $plugin_initializer = false
       @plugin.write "config/initializers/foo.rb", <<-RUBY
         $plugin_initializer = true
@@ -279,7 +252,7 @@ YAML
       assert $plugin_initializer
     end
 
-    def test_plugin_midleware_referenced_in_configuration
+    def test_midleware_referenced_in_configuration
       @plugin.write "lib/bukkits.rb", <<-RUBY
         class Bukkits
           def initialize(app)