reveal_type(User.objects.filter) returns UserManager rather than QuerySet[User]

[kracekumar]

Bug report

from django.contrib.auth.models import User

reveal_type(User.objects.filter(
  email='[email protected]'))

output

# mypy filename.py
note: Revealed type is 
  'django.contrib.auth.models.UserManager
  [django.contrib.auth.models.User]'

What's wrong

The output should QuerySet[django.contrib.auth.models.User]

I don't know this is mypy bug or stubs bug.

How is that should be

QuerySet[django.contrib.auth.models.User]

System information

• OS: OSX
• python version: 3.9.4
• django version: 3.2
• mypy version: 0.812
• django-stubs version: 1.8.0

Mypy config

[mypy]
strict = True
disallow_any_explicit = True
disallow_untyped_calls = True
disallow_untyped_defs = True
disallow_incomplete_defs = True
pretty = True
warn_return_any = False

plugins =
        mypy_django_plugin.main,
        mypy_drf_plugin.main

[mypy.plugins.django-stubs]
django_settings_module = "koans.dj_koans.mysite.mysite.settings"

[sobolevn]

@kracekumar does this happen with other models? Or only with User?

[kracekumar]

@sobolevn It happens for all the models.

from django.db import models
from django.utils import timezone

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField("date published")


class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

reveal_type(Question.objects.filter(id=1))
reveal_type(Choice.objects.filter(id=1))

output

note: Revealed type is 'django.db.models.manager.BaseManager[Any]'
note: Revealed type is 'django.db.models.manager.BaseManager[Any]'

[sobolevn]

Yes, I can confirm: https://github.com/typeddjango/django-stubs/pull/636/checks?check_run_id=2754398770#step:7:249

In [5]: type(ApplicationSubmission.objects.filter(id__gt=0))
Out[5]: django.db.models.query.QuerySet

[p7g]

I think this is because the stub for QuerySet has filter (and other methods) typed like def filter(self: _QS, *args: Any, **kwargs: Any) -> _QS: ..., and these queryset method types are copied verbatim to the generated Manager class type. The result is that any chain of QuerySet methods off of the Manager is typed as a Manager, even though at runtime queryset methods on managers return a queryset.

[sobolevn]

Yes, this is exactly the cause!