beda-software/drf-writable-nested

django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

aboutofpluto opened this issue · 3 comments

aboutofpluto commented

Hi there,

I have this error message as soon as I add 'drf_writable_nested' to INSTALLED_APPS.

** How to reproduce **

My environment is:

$ python --version
Python 3.7.3

$ pip freeze
...
Django==2.2.7
...
djangorestframework==3.10.3
...
drf-writable-nested==0.5.1
...

The problem occurs with the simplest possible installation:

  1. Start a new project
$ django-admin startproject testproject
  1. Edit settings.py to add drf and drf_writable_nested
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'rest_framework',
    'drf_writable_nested',
]
  1. run server (or any command actually)
$  python manage.py runserver
....
File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/drf_writable_nested/__init__.py", line 11, in <module>
    from .mixins import NestedUpdateMixin, NestedCreateMixin, UniqueFieldsMixin
  File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/drf_writable_nested/mixins.py", line 4, in <module>
    from django.contrib.contenttypes.fields import GenericRelation
  File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/django/contrib/contenttypes/fields.py", line 3, in <module>
    from django.contrib.contenttypes.models import ContentType
  File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/django/contrib/contenttypes/models.py", line 133, in <module>
    class ContentType(models.Model):
  File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/django/db/models/base.py", line 103, in __new__
    app_config = apps.get_containing_app_config(module)
  File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/django/apps/registry.py", line 252, in get_containing_app_config
    self.check_apps_ready()
  File "/home/ab/work/django/venv-django-2.2.7/lib/python3.7/site-packages/django/apps/registry.py", line 135, in check_apps_ready
    raise AppRegistryNotReady("Apps aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

** Possible fix **

This can be solved by removing the import statements from drf_writable_nested/__init__.py
This fix is logical (to me at least) and simply implies to import from serializers:

from drf_writable_nested.serializers import WritableNestedModelSerializer

If you think the fix is valid, I'll create a pull request.

Best regards,
ab

ruscoder commented

Hello @aboutofpluto. Thank you for your contribution. There is another opened issue about fixing the tests for Django 2.2 (#87). Your fix will break backward compatibility. If you have ideas about how to fix it in another way - welcome

jqsjqs commented

I am also having this issue.

@aboutofpluto Looks like this patch is a graceful solve that won't break backward compatibility.
@ruscoder can we get it merged?

ruscoder commented

@aboutofpluto @jqsjqs
The simplest solution is not to add 'drf_writable_nested' to installed_apps - it is not necessary for the package.

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