Make many parts of Rails lazy. In order to facilitate this,

add lazy_load_hooks.rb, which allows us to declare code that
should be run at some later time. For instance, this allows
us to defer requiring ActiveRecord::Base at boot time purely
to apply configuration. Instead, we register a hook that should
apply configuration once ActiveRecord::Base is loaded.

With these changes, brings down total boot time of a
new app to 300ms in production and 400ms in dev.

TODO: rename base_hook

12 files changed, 32 insertions, 17 deletions

diff --git a/actionpack/lib/action_controller/base.rb b/actionpack/lib/action_controller/base.rb
index 78871154c3..d00afa6d4e 100644
--- a/actionpack/lib/action_controller/base.rb
+++ b/actionpack/lib/action_controller/base.rb
@@ -58,6 +58,8 @@ module ActionController
       filter
     end
 
+    ActionController.run_base_hooks(self)
+
   end
 end
 
diff --git a/actionpack/lib/action_controller/railtie.rb b/actionpack/lib/action_controller/railtie.rb
index e9edf80451..ca03fc62da 100644
--- a/actionpack/lib/action_controller/railtie.rb
+++ b/actionpack/lib/action_controller/railtie.rb
@@ -40,7 +40,7 @@ module ActionController
     log_subscriber ActionController::Railties::LogSubscriber.new
 
     initializer "action_controller.logger" do
-      ActionController::Base.logger ||= Rails.logger
+      ActionController.base_hook { self.logger ||= Rails.logger }
     end
 
     initializer "action_controller.set_configs" do |app|
@@ -51,19 +51,23 @@ module ActionController
       ac.stylesheets_dir = paths.public.stylesheets.to_a.first
       ac.secret = app.config.cookie_secret
 
-      ActionController::Base.config.replace(ac)
+      ActionController.base_hook { self.config.replace(ac) }
     end
 
     initializer "action_controller.initialize_framework_caches" do
-      ActionController::Base.cache_store ||= RAILS_CACHE
+      ActionController.base_hook { self.cache_store ||= RAILS_CACHE }
     end
 
     initializer "action_controller.set_helpers_path" do |app|
-      ActionController::Base.helpers_path = app.config.paths.app.helpers.to_a
+      ActionController.base_hook do
+        self.helpers_path = app.config.paths.app.helpers.to_a
+      end
     end
 
     initializer "action_controller.url_helpers" do |app|
-      ActionController::Base.extend ::ActionController::Railtie::UrlHelpers.with(app.routes)
+      ActionController.base_hook do
+        extend ::ActionController::Railtie::UrlHelpers.with(app.routes)
+      end
 
       message = "ActionController::Routing::Routes is deprecated. " \
                 "Instead, use Rails.application.routes"
diff --git a/actionpack/lib/action_dispatch/middleware/params_parser.rb b/actionpack/lib/action_dispatch/middleware/params_parser.rb
index 522982e202..f4c4324fb0 100644
--- a/actionpack/lib/action_dispatch/middleware/params_parser.rb
+++ b/actionpack/lib/action_dispatch/middleware/params_parser.rb
@@ -1,4 +1,3 @@
-require 'active_support/json'
 require 'action_dispatch/http/request'
 
 module ActionDispatch
diff --git a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
index db64711052..22da82479e 100644
--- a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
@@ -1,5 +1,4 @@
 require 'active_support/core_ext/hash/keys'
-require 'rack/request'
 
 module ActionDispatch
   module Session
diff --git a/actionpack/lib/action_dispatch/middleware/stack.rb b/actionpack/lib/action_dispatch/middleware/stack.rb
index 18a2922fa7..c52c8c0e6a 100644
--- a/actionpack/lib/action_dispatch/middleware/stack.rb
+++ b/actionpack/lib/action_dispatch/middleware/stack.rb
@@ -58,7 +58,7 @@ module ActionDispatch
           if lazy_compare?(@klass) && lazy_compare?(middleware)
             normalize(@klass) == normalize(middleware)
           else
-            klass == ActiveSupport::Inflector.constantize(middleware.to_s)
+            klass.name == middleware.to_s
           end
         end
       end
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 52e7b0e77d..52a8df4273 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -1,3 +1,5 @@
+require "active_support/core_ext/hash/except"
+
 module ActionDispatch
   module Routing
     class Mapper
@@ -85,7 +87,7 @@ module ActionDispatch
           end
 
           def requirements
-            @requirements ||= returning(@options[:constraints] || {}) do |requirements|
+            @requirements ||= (@options[:constraints] || {}).tap do |requirements|
               requirements.reverse_merge!(@scope[:constraints]) if @scope[:constraints]
               @options.each { |k, v| requirements[k] = v if v.is_a?(Regexp) }
             end
diff --git a/actionpack/lib/action_view.rb b/actionpack/lib/action_view.rb
index f5035fe45a..33bf0b8deb 100644
--- a/actionpack/lib/action_view.rb
+++ b/actionpack/lib/action_view.rb
@@ -41,6 +41,7 @@ module ActionView
       autoload :Rendering
     end
 
+    autoload :Base
     autoload :MissingTemplate,   'action_view/base'
     autoload :Resolver,          'action_view/template/resolver'
     autoload :PathResolver,      'action_view/template/resolver'
@@ -56,6 +57,5 @@ module ActionView
 end
 
 require 'active_support/core_ext/string/output_safety'
-require 'action_view/base'
 
 I18n.load_path << "#{File.dirname(__FILE__)}/action_view/locale/en.yml"
diff --git a/actionpack/lib/action_view/base.rb b/actionpack/lib/action_view/base.rb
index 76f9eb2b0d..e88ccc645e 100644
--- a/actionpack/lib/action_view/base.rb
+++ b/actionpack/lib/action_view/base.rb
@@ -177,6 +177,8 @@ module ActionView #:nodoc:
 
     extend ActiveSupport::Memoizable
 
+    ActionView.run_base_hooks(self)
+
     attr_accessor :base_path, :assigns, :template_extension
     attr_internal :captures
 
diff --git a/actionpack/lib/action_view/helpers/active_model_helper.rb b/actionpack/lib/action_view/helpers/active_model_helper.rb
index ed83b8a8b2..4e12cdab54 100644
--- a/actionpack/lib/action_view/helpers/active_model_helper.rb
+++ b/actionpack/lib/action_view/helpers/active_model_helper.rb
@@ -5,9 +5,11 @@ require 'active_support/core_ext/enumerable'
 require 'active_support/core_ext/kernel/reporting'
 
 module ActionView
-  class Base
-    @@field_error_proc = Proc.new{ |html_tag, instance| "<div class=\"fieldWithErrors\">#{html_tag}</div>".html_safe }
-    cattr_accessor :field_error_proc
+  ActionView.base_hook do
+    class ActionView::Base
+      @@field_error_proc = Proc.new{ |html_tag, instance| "<div class=\"fieldWithErrors\">#{html_tag}</div>".html_safe }
+      cattr_accessor :field_error_proc
+    end
   end
 
   module Helpers
diff --git a/actionpack/lib/action_view/helpers/form_helper.rb b/actionpack/lib/action_view/helpers/form_helper.rb
index ace3bcfde3..742e873a49 100644
--- a/actionpack/lib/action_view/helpers/form_helper.rb
+++ b/actionpack/lib/action_view/helpers/form_helper.rb
@@ -1211,8 +1211,10 @@ module ActionView
     end
   end
 
-  class Base
-    cattr_accessor :default_form_builder
-    @@default_form_builder = ::ActionView::Helpers::FormBuilder
+  ActionView.base_hook do
+    class ActionView::Base
+      cattr_accessor :default_form_builder
+      @@default_form_builder = ::ActionView::Helpers::FormBuilder
+    end
   end
 end
diff --git a/actionpack/lib/action_view/railtie.rb b/actionpack/lib/action_view/railtie.rb
index 03f18ac172..2e5d115630 100644
--- a/actionpack/lib/action_view/railtie.rb
+++ b/actionpack/lib/action_view/railtie.rb
@@ -10,7 +10,9 @@ module ActionView
 
     initializer "action_view.cache_asset_timestamps" do |app|
       unless app.config.cache_classes
-        ActionView::Helpers::AssetTagHelper.cache_asset_timestamps = false
+        ActionView.base_hook do
+          ActionView::Helpers::AssetTagHelper.cache_asset_timestamps = false
+        end
       end
     end
   end
diff --git a/actionpack/lib/action_view/test_case.rb b/actionpack/lib/action_view/test_case.rb
index 72dbead14b..1578ac9479 100644
--- a/actionpack/lib/action_view/test_case.rb
+++ b/actionpack/lib/action_view/test_case.rb
@@ -1,4 +1,5 @@
 require 'action_controller/test_case'
+require 'action_view'
 
 module ActionView
   class Base