Downloading pypy locally to investigate test failures. Not sure what the strategy for the type failures is (ex. switch from Sequence to list, drop the type entirely and noqa or resolve via getting type stubs for mypy?). I misunderstoof mypy errors, it just wants type hints for the data inside the container objects.

Thanks so much for the help!

I think there might be a bug: all derived class of BaseFileLock share the same _instances:

from filelock import UnixFileLock, BaseFileLock

assert UnixFileLock._instances is BaseFileLock._instances

This can be resolved by meta class or simpler __init_subclass__ (python>=3.6)

BTW, maybe we should check if args like mode and timeout is the same as the singleton?

@YouJiacheng good callout. I think I avoided a metaclass in the first place because BaseFileLock inherits from ABC which sets its metaclass already. I can take a look at this later today.

Checking mode and timeout don't seem particularly relevant if we determine two singleton locks are the sam object (so will have the same values), unless you meant something else there.

Okay, __init_subclass__ can be used instead of metaclass.

By checking mode and timeout, I mean: if mode and timeout are different, but lock_file are the same, there should be some warning, since the second mode and timeout will be ignored.

@YouJiacheng here is the fix using __init_subclass__: #318.

As for the other question, deciding on how to handle that seems like something for @gaborbernat to decide on. We could:

1. raise an error
2. update the existing singleton lock
3. ignore doing anything (current behavior)

1. raise an error

Would be my vote.

Fix for incompatible singleton args: #320.