PyCQA/flake8-bugbear

Loop variable use in closure not considered

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#175 opened on Jul 11, 2021

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enhancementhelp wanted

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Description

Running

flake8==3.9.2
flake8-bugbear==21.4.3
flake8-polyfill==1.0.2
flake8-quotes==3.2.0

on

def main():
    def f(x):
        print(i, x)

    for i in [1, 2, 3]:
        f('HI')

gives me

bugbearbug.py:5:9: B007 Loop control variable 'i' not used within the loop body. If this is intended, start the name with an underscore.

Clearly, i is being used (within the nested function), but bugbear doesn't seem to see it.

Contributor guide

Research direction
Investigate the B007 check in flake8 bugbear's source code to understand how it tracks variable usage. Modify the logic to account for variables used in nested closures by traversing nested function scopes.
Tech stack
python
Domain
tooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Python
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60