PyCQA/flake8-bugbear

New check: duplicate types in type hint, or duplicate literals in set

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#371 opened on Mar 21, 2023

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Description

a: int | int | float = ...
b: Union[List[int, int]] = ...
c: Optional[int] | int | None = ... # can probably rely on other linters to not have to deal with this one
d: set[int] = {1, 2, 3, 3, 5}

e: Tuple[int, int] = ... # not an error

these should pretty much always be typos and/or bad copy-pastes, with very few to no false alarms. Don't think it's super common, but definitely not rare or super esoteric.

The check shouldn't have to be too complicated to implement, for the type hint probably need a whitelist of what types you look in (List/list, Set/set, Dict/dict (with special logic), OrderedDict, Optional, Union, Literal...).

For sets you only need to look inside set() (ast.Call) and inside {} (ast.Set), and probably only include literal int/float/strings.

Contributor guide

Research direction
Examine existing checks in flake8 bugbear to understand the pattern, then use ast module to detect duplicate types in type hints and duplicate literals in sets.
Tech stack
python
Domain
devtools
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
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
PythonASTFlake8
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50