mypy complains about ABC service

[gjcarneiro]

Here's some code:

from abc import ABC, abstractmethod
from dataclasses import dataclass
from decimal import Decimal

import svcs
from typing_extensions import override


@dataclass
class Transaction:
    id: str
    amount: Decimal


class Service(ABC):
    @abstractmethod
    def create_transaction(self, *, id: str, amount: Decimal) -> Transaction: ...


class ServiceImpl(Service):
    @override
    def create_transaction(self, *, id: str, amount: Decimal) -> Transaction:
        return Transaction(id, amount)


REGISTRY = svcs.Registry()

REGISTRY.register_factory(Service, ServiceImpl)


def main() -> None:
    container = svcs.Container(REGISTRY)
    service = container.get(Service)

    print(service.create_transaction(id="id1", amount=Decimal(100)))


if __name__ == "__main__":
    main()

This code registers ServiceImpl as factory for the ABC Service. The code works perfectly in runtime, but mypy complains:

$ mypy svcs-test.py  --pretty
svcs-test.py:33: error: Only concrete class can be given where "type[Service]" is expected  [type-abstract]
        service = container.get(Service)
                                ^~~~~~~
Found 1 error in 1 file (checked 1 source file)

Any advice?

[hynek]

That’s sounds like https://svcs.hynek.me/en/stable/typing-caveats.html