not-async-context-manager false positive: wrapped asynccontextmanager

[belm0]

Steps to reproduce

def foo():
    @asynccontextmanager
    async def wrapper(*args, **kwargs):
        pass
    return wrapper

async with foo():
    pass

E1701: Async context manager 'wrapper' doesn't implement __aenter__ and __aexit__. (not-async-context-manager)

The troubling thing is that foo() is part of a public API, which means every project using it would need to suppress not-async-context-manager.

pylint --version output

pylint 2.6.0
astroid 2.4.2
Python 3.8.2 (default, Jun 15 2020, 10:47:09)
[Clang 9.0.0 (clang-900.0.39.2)]

[belm0]

This check is similarly confused by context manager provided by decorators on Trio's CapacityLimiter:

https://github.com/python-trio/trio/blob/cabdd9fb69bcd9e9283ec3eda343a1904c81b528/trio/_sync.py#L101-L103

(that may be covered by existing contextmanager-decorators option, though I haven't checked to see if it correctly supports async context managers)

[ToucanBran]

can confirm also facing the same issue

pylint 2.6.0
astroid 2.4.2
Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 17:54:52) [MSC v.1900 32 bit (Intel)]

[hippo91]

@belm0, @ToucanBran thank for the report.
I can reproduce it with the following code:

#pylint:disable=missing-module-docstring,missing-function-docstring,blacklisted-name
#pylint:disable=unused-argument
from contextlib import asynccontextmanager

def foo():
    @asynccontextmanager
    async def wrapper(*args, **kwargs):
        pass
    return wrapper

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