Rule proposal: `no-negated-some-every`

Description

[
    ![].every(() => true) === [].some(() => !true),
    ![0].every(() => true) === [0].some(() => !true),
    ![1].every(() => true) === [1].some(() => !true),
    ![].every(() => false) === [].some(() => !false),
    ![0].every(() => false) === [0].some(() => !false),
    ![1].every(() => false) === [1].some(() => !false),
]

if (!array.some(element => test(element)));

if (!array.every(element => test(element)));

if (array.every(element => !test(element)));

if (array.some(element => !test(element)));

if (!array.every(Boolean));

if (
	  !array.some(element => {
	  	if (foo) {
			return true;
		}

	  	if (bar) {
			return false;
		}

		return baz;
	  })
);

Contributor guide

Tech stack

javascriptnodejs

Domain

toolingdeveloper experience

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.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

mostly clear

Prerequisites

ESLint plugin basicsAST traversalJavaScript array methodsWriting tests

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

45

Research direction

Study existing rules in the eslint plugin unicorn repository to understand the rule structure (e.g., rules/*.js files, tests). Implement a new rule that detects negated `Array.prototype.some()` and `Array.prototype.every()` calls and suggests using positive forms. Address the ambiguous cases mentioned in the issue, particularly complex callback bodies. Write comprehensive tests for the provided examples and edge cases. Review the issue comments for any additional maintainer guidance or discussion on scope.