Feature request : warning when incorrectly using `__isnull` filters

[malo-malo]

Bug report

What's wrong

This is more of a feature request (for which I did not find a template).
I would like to have a warning or an error when incorrectly using __isnull filters on a field that cannot be null.

How is that should be

For example, with the following model

class MyModel(models.Model):
  name = models.CharField(null=False)

I would like to have warnings in the following cases :

MyModel.objects.filter(name__isnull=False) # Always true, this is a noop that should be removed
MyModel.objects.filter(name__isnull=True) # Filters out the entire queryset, probably a mistake

System information

• OS: Ubuntu 22.04.5 LTS
• python version: Python 3.11.14
• django version: 4.2.26
• mypy version: 1.16.1
• django-stubs version: 5.2.1
• django-stubs-ext version: 5.2.1

[sobolevn]

PRs are welcome :)

[DeXtAr47-oss]

hi @sobolevn I'm thinking of adding a mypy plugin in querysets.pyi file, if no one is working on this then I would like to open a pr

[UnknownPlatypus]

Go for it, however I think you should have a look at orm_lookups.py instead. Especially the typecheck_queryset_filter function which will probably be the place to add such feature