Type error when calling methods of protocol superclass

[medihack]

Describe the bug

In previous versions of pyright the below code didn't have any type errors.

class Base(Protocol):
    def get_data(self):
        ...

class MyMixin:
    def get(self: Base):
        self.get_data()
        super().get_data()

But at least since v1.1.348 (and also the current v1.1.348) the last line (super().get_data()) leads to the error (as mentioned in the discussions):

error: Method "get_data" cannot be called because it is abstract and unimplemented (reportAbstractUsage)

VS Code extension or command-line

Currently running Pyright v1.1.349 from the command line.

[erictraut]

Thanks for the bug report. When you initially mentioned this in the discussion, I assumed it was related to this issue, but that was an incorrect assumption.

This issue is related to a different change that was required for conformance with the typing spec.

Your use case is a little different than the case covered by the typing spec because you've explicitly declared the type of the self parameter to be a protocol. (Technically, the type of self should be Base & Mixin where & represents an intersection, but intersections are not yet supported by the type system.)

I'll need to think more about how to implement this check in a way that is both conformant with the typing standard and enables your use case.

[medihack]

Getting type hints correctly for mixins in Django is a real pain (and this is not just my use case). And yes, I came to the same conclusion that intersections are missing in the Python type system. Especially when the Mixin itself has attributes, here is a real-world example:

class ViewProtocol(Protocol):
    request: HttpRequest

    def dispatch(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse:
        ...

    def get(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse:
        ...

    def get_context_data(self, **kwargs: Any) -> dict[str, Any]:
        ...


class LockedMixinProtocol(ViewProtocol, Protocol):
    settings_model: type[AppSettings]
    section_name: str


class LockedMixin:
    def dispatch(
        self: LockedMixinProtocol, request: HttpRequest, *args: Any, **kwargs: Any
    ) -> HttpResponse:
        settings = self.settings_model.get()

        if settings.locked and not (is_logged_in_user(request.user) and request.user.is_superuser):
            if request.method != "GET":
                raise SuspiciousOperation()

            return TemplateView.as_view(
                template_name="core/section_locked.html",
                extra_context={"section_name": self.section_name},
            )(request)

        return super().dispatch(request, *args, **kwargs)

I hope there will be a solution (I really hate those # type: ignore ;-)). Protocols are also the way mypy recommends to handle Mixins. But those examples do not have any super calls.

[erictraut]

This will be addressed in the next release.

[erictraut]

This is addressed in pyright 1.1.350, which I just published.