My team has run into a bug inUniqueTogetherValidator where it does not work properly with fields with thesource attribute. If a field has asource that is different than the field's name on the serializer, then that field is effectively ignored when checking for uniqueness violations, and theValidationError is not raised.

I am using a serializer set up like this. Note thatUniqueTogetherValidator is expecting the serializer's name for thefields argument— you'll get an erroron this line if you try to provide thesource name instead.

classExampleSerializer(serializers.Serializer):list_id=serializers.PrimaryKeyRelatedField(source='list')position=serializers.IntegerField(source='ordering_key')classMeta:validators= [UniqueTogetherValidator(queryset=ToDoItem.objects.all(),fields=['list_id','position']            )        ]

I believe the bug occurs at this position in the code:

Online 172, we check iffield (which comes fromsource) is inself.fields (which is the name on the serializer). If we're looking at the serializer above, thenattrs.keys() would be['list', 'ordering_key'] andself.fields is['list_id', 'position'].

This means thatchecked_values will always be empty, and aValidationError will never be raised.

Checklist

• Raised initially as discussion #...
• This is not a feature request suitable for implementation outside this project. Please elaborate what it is:
  • compatibility fix for new Django/Python version ...
  • other type of bug fix
  • other type of improvement that does not touch existing code or change existing behavior (e.g. wrapper for new Django field)
• I have reduced the issue to the simplest possible case.

REST Framework version: 3.15.1