sindresorhus/eslint-plugin-unicorn

Improve `prefer-set-has`

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#1,338 opened on Jun 4, 2021

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enhancementhelp wanted

Description

Currently, we only report cases that Array only called .includes(). But in some other cases, it should still be preferred.

const foo = [1, 2, 3];

if (foo.includes(1));

// Still work the same if we use `Set`
for (const element of foo);
const bar = [...foo, somethingElse];
call(...foo);
const length = foo.length; // Use `.size` when switch to Set

// Even this, if the callback don't use the second parameter, they are the same
foo.forEach(element => call(element));

We only need make sure the original Array have unique values.

Contributor guide

Tech stack
javascriptnodejs
Domain
developer experiencetooling
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.
half day
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.
mostly clear
Prerequisites
Familiarity with ESLint plugin developmentUnderstanding of ASTKnowledge of JavaScript Set and Array
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Examine the existing rule implementation in rules/prefer set has.js to understand how .includes() is currently detected. Then, extend the detection to include patterns like for of loops, spread operators, and .forEach() calls, ensuring that the original array has unique values. Consider using AST selectors or visitors to match these patterns. Look at any existing tests in test/snapshots/ or test/rules/ to ensure coverage.