Fix Self typed custom queryset methods incompatible with base queryse…

[moranabadie]

I have made things!

I made a mistake indeed, methods with -> Self for as_manager or from_queryset managers returns an instance of the queryset, not the generated manager.

Related issues

Closes #1840

[moranabadie]

I have executed the tests without mypy and the types matches with mypy.

Du you agree with the two tests in the yml @MrkGrgsn @flaeppe ?

[flaeppe]

I think we would also gain from an assert that a return type of the explicit 'Self' is left untouched.

e.g. that a return type like below is left unchanged

class BaseQuerySet(models.QuerySet["MyModel"]):
    def method(self) -> BaseQuerySet:
        return self

reveal_type(MyModel.objects.method())  # N: Revealed type is "myapp.models.BaseQuerySet"

[MrkGrgsn]

Looks good. A couple of questions though.

1. The as_manager test case is more comprehensive than the from_queryset one although both scenarios should have the same result with respect to custom queryset methods returning Self. Would it make sense for the queryset set up and assertions to be the same in both?
2. Should we also assert that custom manager methods returning Self resolve correctly? I admit I can't think of a use-case for such a method!

class CustomManager(BaseManager):
    def self_return(self) -> Self: ...

NewManager = CustomManager.from_queryset(ModelQuerySet)

reveal_type(MyModel.objects.self_return())  # N: Revealed type is "myapp.models.CustomManagerFromModelQuerySet"

[moranabadie]

# N: Revealed type is "myapp.models.BaseQuerySet"

ok I just added the test for this

[moranabadie]

# N: Revealed type is "myapp.models.CustomManagerFromModelQuerySet"

You are right, The two tests are now mostly the same.

I also added the CustomManager test :)

[MrkGrgsn]

The updates look good to me 👍

[flaeppe]

Thanks