fales positive: unnecessary-dunder-call (__aiter__, __anext__)

[belm0]

Bug description

As of recent pylint versions, I'm seeing the errors below, even though it's suggesting the wrong builtin (iter() rather than aiter()), and even though I'm on Python 3.8 (which doesn't have aiter() and anext() builtins).

Configuration

No response

Command used

pylint

Pylint output

C2801: Unnecessarily calls dunder method __aiter__. Use iter built-in function. (unnecessary-dunder-call)
C2801: Unnecessarily calls dunder method __anext__. Use next built-in function. (unnecessary-dunder-call)

Expected behavior

no errors

Pylint version

pylint 2.15.3
astroid 2.12.10
Python 3.8.12 (default, Sep 23 2021, 08:42:37)
[Clang 12.0.0 (clang-1200.0.32.29)]

OS / Environment

No response

Additional dependencies

No response

[DanielNoord]

@jpy-git Do you happen to know anything about this? Or would you want to take a look at this?

[belm0]

1. fix entries in DUNDER_METHODS. "Use {iter,next}" --> "Use {aiter,anext}"

https://github.com/PyCQA/pylint/blob/ec85e2988679a28dbe11f46d60056b4dd569c44b/pylint/checkers/dunder_methods.py#L108-L109

2. this checker needs to have awareness of the Python version. The brute force for this case would be to declare the set of builtins requiring >= 3.10, and add it to the checker condition.

NEEDS_PYTHON_3_10 = {'__aiter__', '__anext__'}

(If there is no time to do this for the next release, at least disable these entries in DUNDER_METHODS.)

[DanielNoord]

1. fix entries in DUNDER_METHODS. "Use {iter,next}" --> "Use {aiter,anext}"

https://github.com/PyCQA/pylint/blob/ec85e2988679a28dbe11f46d60056b4dd569c44b/pylint/checkers/dunder_methods.py#L108-L109

This is an easy fix. Would you want to open a PR for this? You've done all the work already!

2. this checker needs to have awareness of the Python version. The brute force for this case would be to declare the set of builtins requiring >= 3.10, and add it to the checker condition.

NEEDS_PYTHON_3_10 = {'__aiter__', '__anext__'}

(If there is no time to do this for the next release, at least disable these entries in DUNDER_METHODS.)

I'm not sure I understand this. If you're using __aiter__ then aiter() is available as well right?

[belm0]

I'm not sure I understand this. If you're using __aiter__ then aiter() is available as well right?

No-- this is the misunderstanding of this checker. __aiter__ / __anext__ came with async iterators in Python 3.5, while aiter() / anext() convenience builtins didn't appear until Python 3.10.

[belm0]

some reasons to consider dropping __aiter__ / __anext__ from the table for now:

1. the current pylint guidance is potentially harmful (suggesting the wrong, non-async builtins)
2. even if (1) is trivially corrected, since the builtins were only introduced in a recent Python version, following the pylint guidance will often not be the right thing to do. For example, when the __aiter__ reference is in a library that's trying to be compatible with older, but not yet EOL'd Python versions. (As most libraries should strive to do.) So this guidance is only suited for an application context -- and pylint can't discern that.

As for fixing (rather than removing), I could contribute the change, but it's probably 1-2 hrs for me to work out, including proper tests-- not sure when I can get to it.

[DanielNoord]

I'll work on a fix today which uses py-version, that option allows you to specify which Python version you support.