Use of `get_user_model' at module level in manager causes circular import

[abhiabhi94]

Exception in thread django-main-thread:
Traceback (most recent call last):
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\apps\config.py", line 178, in get_model
    return self.models[model_name.lower()]
KeyError: 'customuser'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\contrib\auth\__init__.py", line 157, in get_user_model
    return django_apps.get_model(settings.AUTH_USER_MODEL, require_ready=False)
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\apps\registry.py", line 211, in get_model
    return app_config.get_model(model_name, require_ready=require_ready)
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\apps\config.py", line 180, in get_model
    raise LookupError(
LookupError: App 'users' doesn't have a 'CustomUser' model.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\users\tyler\appdata\local\programs\python\python38-32\lib\threading.py", line 932, in _bootstrap_inner
    self.run()
  File "c:\users\tyler\appdata\local\programs\python\python38-32\lib\threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\utils\autoreload.py", line 53, in wrapper
    fn(*args, **kwargs)
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\core\management\commands\runserver.py", line 110, in inner_run
    autoreload.raise_last_exception()
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\utils\autoreload.py", line 76, in raise_last_exception
    raise _exception[1]
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\core\management\__init__.py", line 357, in execute
    autoreload.check_errors(django.setup)()
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\utils\autoreload.py", line 53, in wrapper
    fn(*args, **kwargs)
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\apps\registry.py", line 114, in populate
    app_config.import_models()
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\apps\config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "c:\users\tyler\appdata\local\programs\python\python38-32\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\Website\SHHASMRDBAPI\users\models.py", line 4, in <module>
    from api.models.artist_model import Artist
  File "C:\Website\SHHASMRDBAPI\api\models\__init__.py", line 2, in <module>
    from .video_model import Video
  File "C:\Website\SHHASMRDBAPI\api\models\video_model.py", line 7, in <module>
    from flag.models import Flag
  File "C:\Website\SHHASMRDBAPI\flag\models.py", line 11, in <module>
    from flag.managers import FlagInstanceManager, FlagManager
  File "C:\Website\SHHASMRDBAPI\flag\managers.py", line 6, in <module>
    from flag.utils import get_content_type, get_user_for_model
  File "C:\Website\SHHASMRDBAPI\flag\utils.py", line 12, in <module>
    User = get_user_model()
  File "C:\Users\Tyler\.virtualenvs\SHHASMRDBAPI-MStoyG3z\lib\site-packages\django\contrib\auth\__init__.py", line 161, in get_user_model
    raise ImproperlyConfigured(
django.core.exceptions.ImproperlyConfigured: AUTH_USER_MODEL refers to model 'users.CustomUser' that has not been installed

Originally posted by @TSolo315 in #18 (comment)

[TSolo315]

My CustomUser model had a manytomany relationship with a Video model. The video model then had a flag field which would in turn call get_user_model() and lead to either circular import errors or the error listed above depending on the order of the Installed_apps list.

Solution: In CustomUser instead of importing the video model and initiating the field like:

favorite_videos = models.ManyToManyField(Video, blank=True, related_name='favorite_videos')

Don't import the video model and initialize like:

favorite_videos = models.ManyToManyField('api.Video', blank=True, related_name='favorite_videos')

[abhiabhi94]

I have tried experimenting inside the testapp trying to reproduce your issue. You can check the branch fix/circular-import and tell me what needs to be done.

In short, it now has User model(which is equivalent to your CustomUser) inside the user_profile app.
It acts as a foreign key to Post model of the post app. Now, the flag model is associated with this Post model. As of now, I can't reproduce the issue.

Just to be safe, have you added the location of your user model to settings.AUTH_USER_MODEL?

[TSolo315]

Yes, I set settings.AUTH_USER_MODEL to my custom user model.

My user model included these relevant fields:

favorite_artists = models.ManyToManyField(Artist, blank=True, related_name='favorite_artists')
blocked_artists = models.ManyToManyField(Artist, blank=True, related_name='blocked_artists')
favorite_videos = models.ManyToManyField(Video, blank=True, related_name='favorite_videos')
blocked_videos = models.ManyToManyField(Video, blank=True, related_name='blocked_videos')

The video model contains the flag field as well as a separate manytomany field pointing back to the user model via settings.AUTH_USER_MODEL and a foreign key relationship with the artist model.

I tested initializing with get_user_model() on a separate model and ran into the same issue so I don't think the problem is unique to this project.

[abhiabhi94]

Can you just upload a minimum reproducible example in the form of a repository somewhere and share that link here? It will help me in seeing all the code, rather than shooting in the dark. As of now, I can't seem to reproduce the issue on my end.

[TSolo315]

https://github.com/TSolo315/testflag

Ran into the issue making migrations for customUser after adding the many to many fields.

[abhiabhi94]

Thanks, I will try to look into this when I have some more time today.

[abhiabhi94]

Okay, so I could fix this by make these changes:

• using settings.AUTH_USER_MODEL in models.py
• instead of using the get_user_model over a modular level in utils.py, use it directly when it is required.

Please try to verify if it works at your end too.

Thanks for the report. If you can make these changes in #18, I will be happy to merge.

[abhiabhi94]

Also, as a piece of advice, you may probably add a third field non-binary to your gender choices