python - Pyre: `Invalid class instantiation` on a factory pattern with ABC type hint - Stack Overflow

admin2025-05-02  0

I have implemented a factory pattern but Pyre-check trips over the type-hinting, thinking I want to instantiate the mapping dict type hint: type[MyClassABC]

Here is a minimum example, also a pyre-check playground that runs the checks online.

The goal is a factory pattern with proper type hinting. To achieve this I created an ABC for the class, with an abstract method for the __init__, this way in my IDE I can see which parameters to supply thanks to the ABC init. However, I get the error:

 33:15: Invalid class instantiation [45]: Cannot instantiate abstract class `MyClassABC` with abstract method `__init__`. 

Because Pyre-check thinks I am going to instantiate the type-hint, type[MyClassABC]. How can I fix my type hinting so that it's still proper type hinting but Pyre-check doesn't think I'm instantiating an abstract method? I would like to keep the abstractmethod init for the parameter type hinting.

from abc import abstractmethod


class MyClassABC:
    @abstractmethod
    def __init__(self, name: str) -> None:
        pass


class MyClass2(MyClassABC):
    def __init__(self, name: str) -> None:
        self.name = name


class MyClass(MyClassABC):
    def __init__(self, name: str) -> None:
        self.name = name


class ClassFactory:
    MAPPING: dict[str, type[MyClassABC]] = {
        "myclass": MyClass,
        "myclass2": MyClass2,
    }

    @staticmethod
    def get_class() -> type[MyClassABC]:
        return ClassFactory.MAPPING["myclass"]


if __name__ == "__main__":
    factory_cls = ClassFactory.get_class()
    instance = factory_cls(name="test")
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