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

5 files changed, 16 insertions, 7 deletions

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