Extensions to nil which allow for more helpful error messages for people who are new to Rails.
Ruby raises NoMethodError if you invoke a method on an object that does not respond to it:
$ ruby -e nil.destroy -e:1: undefined method `destroy' for nil:NilClass (NoMethodError)
With these extensions, if the method belongs to the public interface of the classes in NilClass::WHINERS the error message suggests which could be the actual intended class:
$ script/runner nil.destroy ... You might have expected an instance of ActiveRecord::Base. ...
NilClass#id exists in Ruby 1.8 (though it is deprecated). Since id is a fundamental method of Active Record models NilClass#id is redefined as well to raise a RuntimeError and warn the user. She probably wanted a model database identifier and the 4 returned by the original method could result in obscure bugs.
The flag config.whiny_nils determines whether this feature is enabled. By default it is on in development and test modes, and it is off in production mode.
AS_JSON = ActiveSupport::JSON::Variable.new('null').freeze
WHINERS = [::Array]
METHOD_CLASS_MAP = Hash.new
actionpack/lib/action_controller/routing/routing_ext.rb activesupport/lib/active_support/core_ext/object/blank.rb activesupport/lib/active_support/core_ext/duplicable.rb activesupport/lib/active_support/core_ext/try.rb activesupport/lib/active_support/json/encoders/nil_class.rb activesupport/lib/active_support/whiny_nil.rb