module ActiveSupport::Dependencies

def remove_constant(const) #:nodoc:
  # Normalize ::Foo, ::Object::Foo, Object::Foo, Object::Object::Foo, etc. as Foo.
  normalized = const.to_s.sub(/\A::/, "")
  normalized.sub!(/\A(Object::)+/, "")
  constants = normalized.split("::")
  to_remove = constants.pop
  # Remove the file path from the loaded list.
  file_path = search_for_file(const.underscore)
  if file_path
    expanded = File.expand_path(file_path)
    expanded.sub!(/\.rb\z/, "")
    loaded.delete(expanded)
  end
  if constants.empty?
    parent = Object
  else
    # This method is robust to non-reachable constants.
    #
    # Non-reachable constants may be passed if some of the parents were
    # autoloaded and already removed. It is easier to do a sanity check
    # here than require the caller to be clever. We check the parent
    # rather than the very const argument because we do not want to
    # trigger Kernel#autoloads, see the comment below.
    parent_name = constants.join("::")
    return unless qualified_const_defined?(parent_name)
    parent = constantize(parent_name)
  end
  # In an autoloaded user.rb like this
  #
  #   autoload :Foo, 'foo'
  #
  #   class User < ActiveRecord::Base
  #   end
  #
  # we correctly register "Foo" as being autoloaded. But if the app does
  # not use the "Foo" constant we need to be careful not to trigger
  # loading "foo.rb" ourselves. While #const_defined? and #const_get? do
  # require the file, #autoload? and #remove_const don't.
  #
  # We are going to remove the constant nonetheless ---which exists as
  # far as Ruby is concerned--- because if the user removes the macro
  # call from a class or module that were not autoloaded, as in the
  # example above with Object, accessing to that constant must err.
  unless parent.autoload?(to_remove)
    begin
      constantized = parent.const_get(to_remove, false)
    rescue NameError
      # The constant is no longer reachable, just skip it.
      return
    else
      constantized.before_remove_const if constantized.respond_to?(:before_remove_const)
    end
  end
  begin
    parent.instance_eval { remove_const to_remove }
  rescue NameError
    # The constant is no longer reachable, just skip it.
  end
end