plataformatec/simple_form — pull request #771 by zephyr-dev (2013-03-18 14:06:50+00:00)
Title: Fix the way `detect_common_display_methods` finds label & value methods

It was previously looking at an instance of the `collection` instead of the `collection_classes`. Since the grouped collection input supplies a list of collection classes that differ from the regular collection, it was incorrectly looking for labelling and value methods on the option instances, rather than the optgroup instances.