Queryset: TypeError: 'type' object is not subscriptable

[sobolevn]

Code:

# -*- coding: utf-8 -*-

from django.db.models.query import QuerySet

from server.apps.main.models import BlogPost


def published_posts() -> QuerySet[BlogPost]:
    """Returns published blog posts."""
    return BlogPost.objects.filter(
        is_published=True,
    )

Output:

» python manage.py runserver
2019-08-26 08:32:24 [INFO] Watching for file changes with StatReloader
Performing system checks...

Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/Users/sobolev/.pyenv/versions/3.7.4/lib/python3.7/threading.py", line 926, in _bootstrap_inner
    self.run()
  File "/Users/sobolev/.pyenv/versions/3.7.4/lib/python3.7/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 117, in inner_run
    self.check(display_num_errors=True)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/core/management/base.py", line 390, in check
    include_deployment_checks=include_deployment_checks,
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/core/management/base.py", line 377, in _run_checks
    return checks.run_checks(**kwargs)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/core/checks/registry.py", line 72, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/core/checks/urls.py", line 13, in check_url_config
    return check_resolver(resolver)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/core/checks/urls.py", line 23, in check_resolver
    return check_method()
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/urls/resolvers.py", line 398, in check
    for pattern in self.url_patterns:
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/urls/resolvers.py", line 579, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/Users/sobolev/Desktop/django_stubs_example/.venv/lib/python3.7/site-packages/django/urls/resolvers.py", line 572, in urlconf_module
    return import_module(self.urlconf_name)
  File "/Users/sobolev/.pyenv/versions/3.7.4/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/Users/sobolev/Desktop/django_stubs_example/server/urls.py", line 21, in <module>
    from server.apps.main import urls as main_urls
  File "/Users/sobolev/Desktop/django_stubs_example/server/apps/main/urls.py", line 6, in <module>
    from server.apps.main.views import BlogPostViewset, index
  File "/Users/sobolev/Desktop/django_stubs_example/server/apps/main/views.py", line 7, in <module>
    from server.apps.main.logic import repo
  File "/Users/sobolev/Desktop/django_stubs_example/server/apps/main/logic/repo.py", line 8, in <module>
    def published_posts() -> QuerySet[BlogPost]:
TypeError: 'type' object is not subscriptable

Reproduction: https://github.com/sobolevn/django_stubs_example

Fix:

def published_posts() -> 'QuerySet[BlogPost]':
    ...

I guess that it is related to #144 and also should be just documented properly.
Because for now it might cause a confusion for newcomers.

[MarcinWieczorek]

Any update on this?

[mkurnikov]

Short term fix:

• for annotations - wrap with string, as mentioned by @sobolevn
• for subclassing -

class MyManager(models.Manager):
    pass
class MyModel(models.Model):
    objects = MyManager()

if you have this code (models.Manager is the same as models.Manager[Any]), plugin should perform some magic so that actual objects class will have the correct generic Manager[MyModel].

Long term fix:
vote, push core-devs, add comments under django/deps#65 (comment)

We really need to document this stuff...

[MohGanji]

Short term fix:

• for annotations - wrap with string, as mentioned by @sobolevn

To make it easier to access, this means doing like this:

def published_posts() -> 'QuerySet[BlogPost]:'
    pass

[antonio-antuan]

I can suggest a hack that helped me:

T = TypeVar('T', bound='BaseUser')
if TYPE_CHECKING:

    _UserManager = BaseUserManager
else:

    class FakeGenericMeta(BaseUserManager.__class__):  # TODO hack, will be deleted with django 3.1
        def __getitem__(self, item):
            return self

    class _UserManager(BaseUserManager, metaclass=FakeGenericMeta):
        pass


class UserManager(_UserManager[T]):
    pass

class BaseUser(AbstractBaseUser):
    objects: UserManager[BaseUser] = UserManager()
...

[flaeppe]

QuerySet has had subscriptable support for quite some time