Unexpected warnings on final class derived from ABC

[Azureblade3808]

Environment data

• Language Server version: 2021.8.4-pre.1
• OS and version: Windows 7
• Python version (& distribution if applicable, e.g. Anaconda): Python 3.8.11 (Anaconda)

Sample code

from abc import ABC
from typing import final

class Base(ABC):
    pass

@final
class Derived(Base):
    pass

_ = Derived()

Expected behavior

No error.

Actual behavior

[erictraut]

Thanks for the bug report. It's a trivial fix. I wasn't handling the case where there were no abstract methods defined in the abstract base class. Kind of a weird use case, but I guess it's legit. This will be fixed in the next release.

[Azureblade3808]

With some abstract methods in the base class, all of which get implemented in the derived class, the warning still exists. So the issue may not be that rare like the sample shows.

[erictraut]

Yeah, that's a good point. My fix will address that case too.

[jakebailey]

This issue has been fixed in version 2021.7.0, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/main/CHANGELOG.md#202190-1-september-2021