pylint-dev/pylint

Unnecessary use of a comprehension: Wrong fix

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#8,256 opened on Feb 10, 2023

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Bug :beetle:Good first issueMinor 💅Needs PR

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Description

Bug description

# pylint: disable=missing-docstring
dict1 = {(1, 2): 3}
dict2 = {a: b for a, b in dict1}

Configuration

No response

Command used

pylint x.py

Pylint output

************* Module a
a.py:x:3: [R1721(unnecessary-comprehension), ] Unnecessary use of a comprehension, use dict(dict1) instead.

Expected behavior

unnecessary-comprehension is correct, but since dict1 already is a dict, dict(dict1) would simply create a copy of dict1.

The correct fix here would be: dict(dict1.keys())

Pylint version

pylint 2.13.9
astroid 2.11.7
Python 3.6.8 (default, Mar 18 2021, 08:58:41) 
[GCC 8.4.1 20200928 (Red Hat 8.4.1-1)]

OS / Environment

Red Hat 8

Additional dependencies

No response

Contributor guide

Research direction
Inspect the logic for 'unnecessary comprehension' checker in pylint/checkers/refactoring/misplaced comparison constant.py or similar. The issue is that when the iterable is a dict, the suggestion should use `dict(dict1.keys())` instead of `dict(dict1)`.
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
GitPython
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65