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

3 files changed, 6 insertions, 4 deletions

diff --git a/railties/lib/rails/application/routes_reloader.rb b/railties/lib/rails/application/routes_reloader.rb
index fde6211c5d..a5154f4bba 100644
--- a/railties/lib/rails/application/routes_reloader.rb
+++ b/railties/lib/rails/application/routes_reloader.rb
@@ -27,7 +27,7 @@ module Rails
 
         routes.clear!
         paths.each { |path| load(path) }
-        routes.finalize!
+        ActionController.base_hook { routes.finalize! }
 
         nil
       ensure
diff --git a/railties/lib/rails/console/helpers.rb b/railties/lib/rails/console/helpers.rb
index 039db667c4..212fc6125a 100644
--- a/railties/lib/rails/console/helpers.rb
+++ b/railties/lib/rails/console/helpers.rb
@@ -2,4 +2,6 @@ def helper
   @helper ||= ApplicationController.helpers
 end
 
-@controller = ApplicationController.new
+def controller
+  @controller ||= ApplicationController.new
+end
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index 8f5040ea13..85b4ff8470 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -97,8 +97,8 @@ module Rails
 
     initializer :add_view_paths do
       views = paths.app.views.to_a
-      ActionController::Base.prepend_view_path(views) if defined?(ActionController::Base)
-      ActionMailer::Base.prepend_view_path(views) if defined?(ActionMailer::Base)
+      ActionController.base_hook { prepend_view_path(views) } if defined?(ActionController)
+      ActionMailer.base_hook { prepend_view_path(views) } if defined?(ActionMailer)
     end
 
     initializer :add_metals do |app|