Incompatibility with django-cte

[StefanBrand]

Bug report

What's wrong

After adding django-cte to a codebase I got an Internal error from mypy and traced it down to the presence of the django-stubs mypy plug-in. -> python/mypy#13010

How is that should be

I would like to keep using django-stubs in addition to django_cte functionality.

System information

• OS: Docker image python:3.9.1
• python version: 3.9.1
• django version: 4.0.1
• mypy version: 0.970+dev.eb1b1e007e7fd1e976e6dd0f49a71b662a30a2d6
• django-stubs version: 1.12.0
• django-stubs-ext version: 0.5.0

[StefanBrand]

I could track it down to one use of django_cte.CTEQuerySet in a custom queryset:

from django_cte import CTEQuerySet

class CustomQuerySet(CTEQuerySet):
    ...

If I replace the CTEQuerySet back to a normal django.db.models.QuerySet, Success: no issues found in 1 source file.

from django.db import models

class CustomQuerySet(models.QuerySet):
    ...

PS.: At runtime this leads to AttributeError: 'CustomQuerySet' object has no attribute 'with_cte'.

[sobolevn]

If you can create a reproducible example, I would be happy to fix it!

[StefanBrand]

Tracking the issue down further, CustomManager = models.Manager.from_queryset(CustomQuerySet) seems to be a problem.

from django.db import models
from django_cte import CTEQuerySet

class CustomQuerySet(CTEQuerySet):
    ...

CustomManager = models.Manager.from_queryset(CustomQuerySet)

class MyModel(models.Model):
    objects = CustomManager()
    ...

results in the mypy crash, while the following works (resulting in Could not resolve manager type for "models.MyModel.objects"):

from django.db import models
from django_cte import CTEManager, CTEQuerySet

class CustomQuerySet(CTEQuerySet):
    ...

CustomManager = CTEManager.from_queryset(CustomQuerySet)

class MyModel(models.Model):
    objects = CustomManager()
    ...

Here is a diff. It seems that models.Manager does not work together with CTEQuerySet. The as_manager() method of CTEQuerySet of course also uses CTEManager.

 from django.db import models
-from django_cte import CTEQuerySet
+from django_cte import CTEManager, CTEQuerySet
 
 class CustomQuerySet(CTEQuerySet):
     ...
 
-CustomManager = models.Manager.from_queryset(CustomQuerySet)
+CustomManager = CTEManager.from_queryset(CustomQuerySet)
 
 class MyModel(models.Model):
     objects = CustomManager()

I am mainly using from_queryset because QuerySet.as_manager is not supported by django-stubs yet. However with django-cte types for the manager are not available either way, so I'll accept some type: ignore there. This is better than mypy not working at all. :)

PS.: Unfortunately I cannot reproduce the problem in a minimal, less complex project. 🙁