False positive ``no-member`` with ``@contextmanager`` decorated generators

[ZeeD]

I have this little snippet:

import contextlib

@contextlib.contextmanager
def context_manager():
    try:
        yield
    finally:
        pass

cm = context_manager()
cm.__enter__()
cm.__exit__(None, None, None)

pylint signals the "direct" access to the __enter__ and __exit__ callables as an error:

contextmanaged.py:13:0: E1101: Generator 'generator' has no '__enter__' member (no-member)
contextmanaged.py:14:0: E1101: Generator 'generator' has no '__exit__' member (no-member)

while "uncommon" at least, I think it should not be marked as an error.

> pylint --version
pylint 2.1.1
astroid 2.0.4
Python 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]

[PCManticore]

Thanks for the report, definitely a bug.

[Vihrastik]

And for

import contextlib

@contextlib.contextmanager
def context_manager():
    try:
        yield
    finally:
        pass

with context_manager:
    pass

have an error

[E1129 not-context-manager] Context manager 'context_manager' doesn't implement __enter__ and __exit__.

[PCManticore]

@Vihrastik You need to call context_manager for that to be valid, e.g.:

import contextlib

@contextlib.contextmanager
def context_manager():
    try:
        yield
    finally:
        pass

with context_manager(): # notice the function call
    pass

[Vihrastik]

@Vihrastik You need to call context_manager for that to be valid, e.g.:

import contextlib

@contextlib.contextmanager
def context_manager():
    try:
        yield
    finally:
        pass

with context_manager(): # notice the function call
    pass

no, i just forgot to write it in the example of code. this error is active with call.

[gyermolenko]

Hi. I wanted to work on this issue if nobody minds.

Regarding snippet

import contextlib

@contextlib.contextmanager
def context_manager():
    try:
        yield
    finally:
        pass

with context_manager():
    pass

which @Vihrastik reports to [E1129 not-context-manager] - I did not reproduce that with pylint 2.3.1 / astroid 2.2.5.

However when I created local env with pylint from master (2.4.0.dev0) / astroid 2.2.5 I receive error from #3022 about posonlyargs. Installing astroid from master fixes the issue.

[PCManticore]

Hi @gyermolenko Feel free to tackle this issue! Regarding your issue with posonlyargs, pylint from master needs the up to date astroid.

[clavedeluna]

@Vihrastik You need to call context_manager for that to be valid, e.g.:

import contextlib

@contextlib.contextmanager
def context_manager():
    try:
        yield
    finally:
        pass

with context_manager(): # notice the function call
    pass

no, i just forgot to write it in the example of code. this error is active with call.

I'm not able to reproduce this second issue, but I am able to reproduce original issue raised at the top.

[clavedeluna]

@DanielNoord I thought maybe the changes in https://github.com/PyCQA/astroid/pull/1810 would fix the initial FP, but it's still present. What else needs to happen in astroid?

[DanielNoord]

Have you checked out main? We haven't released a version with that fix in it.

[Pierre-Sassoulas]

There's two PR left for astroid 2.13.0, you can follow progress here: https://github.com/PyCQA/astroid/milestone/40

[clavedeluna]

Score! Testing this out on astroid main solves this issue. Will update labels and hopefully can be closed once 2.13.0 is out.

[Pierre-Sassoulas]

@clavedeluna 2.13.2 is out, the pylint PR is #8030

[socketpair]

Finally, in what versions of Pylint / Astroid it is fixed ? I'm using Fedora 38 and this is triggered in spite of relatively new versions.

[Pierre-Sassoulas]

The milestone is 2.16.0 here, please open a new issue if there was a regression :)