not-async-context-manager / E1701

Message emitted:

Async context manager '%s' doesn't implement __aenter__ and __aexit__.

Description:

Used when an async context manager is used with an object that does not implement the async context management protocol.

Problematic code:

class ContextManager:
    def __enter__(self):
        pass

    def __exit__(self, *exc):
        pass


async def foo():
    async with ContextManager():  # [not-async-context-manager]
        pass

Correct code:

class AsyncContextManager:
    def __aenter__(self):
        pass

    def __aexit__(self, *exc):
        pass


async def foo():
    async with AsyncContextManager():
        pass

Additional details:

Async context manager doesn't implement __aenter__ and __aexit__. It can't be emitted when using Python < 3.5.

Created by the async checker.