jsx-eslint/eslint-plugin-react

react/no-unused-prop-types false positive when using memo

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#3403 opened on Sep 5, 2022

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bughelp wanted

Description

Here's an example using CRA

Expected: No warning

Actual:

  • npm run lint
eslint-example/src/App.js
  23:3  warning  'showFirst' PropType is defined but prop is never used  react/no-unused-prop-types

This started when going from version 7.30.0 to 7.30.1.

  • If I remove memo the warning goes away
  • If I wrap the ternary in the return with a fragment the warning goes away but then I'd have to silence react/jsx-no-useless-fragment so not helpful either.

Contributor guide

Tech stack
javascriptreact
Domain
frontend
Issue type
bug
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic React knowledgeUnderstanding of ESLint rule structure
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55
Research direction
The issue is a false positive in the react/no unused prop types rule when a component is wrapped in React.memo. The rule started incorrectly warning after version 7.30.0. Investigate the rule's source code in the lib/rules/no unused prop types.js file, particularly the logic that handles wrapped components. Look for changes between versions that might have introduced this regression. Review the comments for additional test cases and consider reproducing the issue with the provided example.