* A new module (ActiveSupport::Autoload) is provide that extends
autoloading with new behavior.
* All autoloads in modules that have extended ActiveSupport::Autoload
will be eagerly required in threadsafe environments
* Autoloads can optionally leave off the path if the path is the same
as full_constant_name.underscore
* It is possible to specify that a group of autoloads live under an
additional path. For instance, all of ActionDispatch's middlewares
are ActionDispatch::MiddlewareName, but they live under
"action_dispatch/middlewares/middleware_name"
* It is possible to specify that a group of autoloads are all found
at the same path. For instance, a number of exceptions might all
be declared there.
* One consequence of this is that testing-related constants are not
autoloaded. To get the testing helpers for a given component,
require "component_name/test_case". For instance, "action_controller/test_case".
* test_help.rb, which is automatically required by a Rails application's
test helper, requires the test_case.rb for all active components, so
this change will not be disruptive in existing or new applications.
Joshua Peek