Question

Currently, in django.contrib.auth, there can be two users with the username ‘john’ and ‘John’. How can I prevent this from happening.

The most straightforward approach is add a clean method in contib.auth.models and convert it to a lowercase before saving but i dont want to edit the contrib.auth package.

Thanks.

Answer 1

Listen on pre_save for the Users model and then do your checks there. Least intrusive and most portable way.

Here is an example on how this would look like (adapted from the user profile example):

def username_check(sender, instance, **kwargs):
    if User.objects.filter(username=instance.username.lower()).count():
       raise ValidationError('Duplicate username')

pre_save.connect(username_check, sender=User)