Args types for Model.objects.filter

[mjozan]

Hello,

I am using vscode with Pylance and I would like to know if it is normal that the types for Model.objects.filter arguments are Any. So if I do this it does not complain:

class Cheese(models.Model):
    a: BooleanField = models.BooleanField()


def f() -> None:
    Cheese.objects.filter(does_not_exist=True)

When I ctrl + click it redirects me to this line that shows that there is not type checking for the filter argument.

django-stubs/django-stubs/db/models/manager.pyi

Line 116 in e566001

def filter(self, *args: Any, **kwargs: Any) -> QuerySet[_T]: ...

Is there a way to have type checking for these arguments please?

[ducdetronquito]

As far as I know, there is no way to do this because of the dynamic nature of the Django ORM itself and its numerous magic methods like myfield__isnull=True, myfield__gte=3, for which their type can only be evaluated at runtime.

On approach could be to provide a type safe method defined on the model instead of using the ORM directly: the method user can then query your model in a typesafe way, and the potential type unsafety are constrained within this method and not everywhere in your codebase. But the drawbacks could be that you lose some flexibility or a way to chain QuerySet method like you are used to.

class Cheese(modesl.Model):
    is_good =   models.BooleanField()

    @classmethod
    def get_good_cheeses(cls) -> list["Cheese"]:
        return cls.objects.filter(is_good=True)

[UnknownPlatypus]

This can maybe be improved in the mypy plugin ?