| 25 | 25 | The reason for this bug is commit https://github.com/django/django/commit/47016adbf54b54143d4cf052eeb29fc72d27e6b1 which was proposed and accepted as a fix for bug https://code.djangoproject.com/ticket/28490. The problem is while it fixed that bug it broke the functionality of _check_list_display_item in other cases. The rationale for that change was that after field=getattr(model, item) field could be None if item was a descriptor returning None, but subsequent code incorrectly interpreted field being None as meaning getattr raised an AttributeError. As this was done **after** trying field = model._meta.get_field(item) and that failing that meant the validation error should be returned. However, after the above change if hasattr(model, item) is false then we no longer even try field = model._meta.get_field(item) before returning an error. The reason hasattr(model, item) is false in the case of a PositionField is its __get__ method throws an exception if called on an instance of the PositionField class on the Thing model class, rather than a Thing instance. |