Django support: MongoEngineBackend does not respect custom user model's USERNAME_FIELD

[mikelrob]

I've created a custom user model which does not have a username field, but rather uses the email field in lieu.

I followed the article @ http://docs.mongoengine.org/django.html#custom-user-model, carrying out both modifications in the settings.py:

INSTALLED_APPS = (
    ...
    'django.contrib.auth',
    'mongoengine.django.mongo_auth',
    ...
)

AUTH_USER_MODEL = 'mongo_auth.MongoUser'

and importantly:

MONGOENGINE_USER_DOCUMENT = 'MongoLogOn.models.User'  # my custom User Model

My custom User model specifies the following:

class User(MongoUser):
    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['password']

It is worth noting that the above inherited MongoUserDoc is a direct copy of mongoengine.django.auth.User with the username field removed as the 30 char limit is far too restrictive.

The trouble I'm having is that when I call authenticate(<email>, <password>) in my log in view, it returns None.

I suspect the trouble is caused by the MongoEngineBackend as it blindly tries to retrieve the User document using the username field instead respecting the USERNAME_FIELD which is set in the custom User model as seen below:

class MongoEngineBackend(object):
    ...
    def authenticate(self, username=None, password=None):
        user = self.user_document.objects(username=username).first()

My work around uses the following to circumvent the issue:

class MongoEngineBackend(object):
    ...
    def authenticate(self, username=None, password=None):
        filter_dict = {self.user_document.USERNAME_FIELD: username}
        user = self.user_document.objects(**filter_dict).first()

So far I have had success with this work around.

[mmellison]

Label and close as part of Django split. See #973.