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Add
no-negated-condition
rule (#1963)
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# Disallow negated conditions | ||
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✅ This rule is enabled in the `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs). | ||
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🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix). | ||
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<!-- end auto-generated rule header --> | ||
<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` --> | ||
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Negated conditions are more difficult to understand. Code can be made more readable by inverting the condition. | ||
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This is an improved version of the [`no-negated-condition`](https://eslint.org/docs/latest/rules/no-negated-condition) ESLint rule that makes it automatically fixable. [ESLint did not want to make it fixable.](https://github.com/eslint/eslint/issues/14792) | ||
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## Fail | ||
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```js | ||
if (!a) { | ||
doSomethingC(); | ||
} else { | ||
doSomethingB(); | ||
} | ||
``` | ||
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```js | ||
if (a !== b) { | ||
doSomethingC(); | ||
} else { | ||
doSomethingB(); | ||
} | ||
``` | ||
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```js | ||
!a ? c : b | ||
``` | ||
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```js | ||
if (a != b) { | ||
doSomethingC(); | ||
} else { | ||
doSomethingB(); | ||
} | ||
``` | ||
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## Pass | ||
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```js | ||
if (a) { | ||
doSomethingB(); | ||
} else { | ||
doSomethingC(); | ||
} | ||
``` | ||
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```js | ||
if (a === b) { | ||
doSomethingB(); | ||
} else { | ||
doSomethingC(); | ||
} | ||
``` | ||
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```js | ||
a ? b : c | ||
``` | ||
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```js | ||
if (a == b) { | ||
doSomethingB(); | ||
} else { | ||
doSomethingC(); | ||
} | ||
``` | ||
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```js | ||
if (!a) { | ||
doSomething(); | ||
} | ||
``` | ||
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```js | ||
if (!a) { | ||
doSomething(); | ||
} else if (b) { | ||
doSomethingElse(); | ||
} | ||
``` | ||
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```js | ||
if (a != b) { | ||
doSomething(); | ||
} | ||
``` |
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/* | ||
Based on ESLint builtin `no-negated-condition` rule | ||
https://github.com/eslint/eslint/blob/5c39425fc55ecc0b97bbd07ac22654c0eb4f789c/lib/rules/no-negated-condition.js | ||
*/ | ||
'use strict'; | ||
const {matches} = require('./selectors/index.js'); | ||
const { | ||
removeParentheses, | ||
fixSpaceAroundKeyword, | ||
addParenthesizesToReturnOrThrowExpression, | ||
} = require('./fix/index.js'); | ||
const { | ||
getParenthesizedRange, | ||
isParenthesized, | ||
} = require('./utils/parentheses.js'); | ||
const isOnSameLine = require('./utils/is-on-same-line.js'); | ||
const needsSemicolon = require('./utils/needs-semicolon.js'); | ||
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const MESSAGE_ID = 'no-negated-condition'; | ||
const messages = { | ||
[MESSAGE_ID]: 'Unexpected negated condition.', | ||
}; | ||
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const selector = [ | ||
matches([ | ||
'IfStatement[alternate][alternate.type!="IfStatement"]', | ||
'ConditionalExpression', | ||
]), | ||
matches([ | ||
'[test.type="UnaryExpression"][test.operator="!"]', | ||
'[test.type="BinaryExpression"][test.operator="!="]', | ||
'[test.type="BinaryExpression"][test.operator="!=="]', | ||
]), | ||
].join(''); | ||
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function * convertNegatedCondition(fixer, node, sourceCode) { | ||
const {test} = node; | ||
if (test.type === 'UnaryExpression') { | ||
const token = sourceCode.getFirstToken(test); | ||
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if (node.type === 'IfStatement') { | ||
yield * removeParentheses(test.argument, fixer, sourceCode); | ||
} | ||
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yield fixer.remove(token); | ||
return; | ||
} | ||
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const token = sourceCode.getTokenAfter( | ||
test.left, | ||
token => token.type === 'Punctuator' && token.value === test.operator, | ||
); | ||
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yield fixer.replaceText(token, '=' + token.value.slice(1)); | ||
} | ||
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function * swapConsequentAndAlternate(fixer, node, sourceCode) { | ||
const isIfStatement = node.type === 'IfStatement'; | ||
const [consequent, alternate] = [ | ||
node.consequent, | ||
node.alternate, | ||
].map(node => { | ||
const range = getParenthesizedRange(node, sourceCode); | ||
let text = sourceCode.text.slice(...range); | ||
// `if (!a) b(); else c()` can't fix to `if (!a) c() else b();` | ||
if (isIfStatement && node.type !== 'BlockStatement') { | ||
text = `{${text}}`; | ||
} | ||
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return { | ||
range, | ||
text, | ||
}; | ||
}); | ||
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if (consequent.text === alternate.text) { | ||
return; | ||
} | ||
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yield fixer.replaceTextRange(consequent.range, alternate.text); | ||
yield fixer.replaceTextRange(alternate.range, consequent.text); | ||
} | ||
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/** @param {import('eslint').Rule.RuleContext} context */ | ||
const create = context => ({ | ||
[selector](node) { | ||
return { | ||
node: node.test, | ||
messageId: MESSAGE_ID, | ||
/** @param {import('eslint').Rule.RuleFixer} fixer */ | ||
* fix(fixer) { | ||
const sourceCode = context.getSourceCode(); | ||
yield * convertNegatedCondition(fixer, node, sourceCode); | ||
yield * swapConsequentAndAlternate(fixer, node, sourceCode); | ||
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if ( | ||
node.type !== 'ConditionalExpression' | ||
|| node.test.type !== 'UnaryExpression' | ||
) { | ||
return; | ||
} | ||
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yield * fixSpaceAroundKeyword(fixer, node, sourceCode); | ||
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const {test, parent} = node; | ||
const [firstToken, secondToken] = sourceCode.getFirstTokens(test, 2); | ||
if ( | ||
(parent.type === 'ReturnStatement' || parent.type === 'ThrowStatement') | ||
&& parent.argument === node | ||
&& !(isParenthesized(node, sourceCode) && !isParenthesized(test, sourceCode)) | ||
&& !isOnSameLine(firstToken, secondToken) | ||
) { | ||
yield * addParenthesizesToReturnOrThrowExpression(fixer, parent, sourceCode); | ||
return; | ||
} | ||
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const tokenBefore = sourceCode.getTokenBefore(node); | ||
if (needsSemicolon(tokenBefore, sourceCode, secondToken.value)) { | ||
yield fixer.insertTextBefore(node, ';'); | ||
} | ||
}, | ||
}; | ||
}, | ||
}); | ||
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/** @type {import('eslint').Rule.RuleModule} */ | ||
module.exports = { | ||
create, | ||
meta: { | ||
type: 'suggestion', | ||
docs: { | ||
description: 'Disallow negated conditions.', | ||
}, | ||
fixable: 'code', | ||
messages, | ||
}, | ||
}; |
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import outdent from 'outdent'; | ||
import {getTester} from './utils/test.mjs'; | ||
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const {test} = getTester(import.meta); | ||
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test.snapshot({ | ||
valid: [ | ||
'if (a) {}', | ||
'if (a) {} else {}', | ||
'if (!a) {}', | ||
'if (!a) {} else if (b) {}', | ||
'if (!a) {} else if (b) {} else {}', | ||
'if (a == b) {}', | ||
'if (a == b) {} else {}', | ||
'if (a != b) {}', | ||
'if (a != b) {} else if (b) {}', | ||
'if (a != b) {} else if (b) {} else {}', | ||
'if (a !== b) {}', | ||
'if (a === b) {} else {}', | ||
'a ? b : c', | ||
], | ||
invalid: [ | ||
'if (!a) {;} else {;}', | ||
'if (a != b) {;} else {;}', | ||
'if (a !== b) {;} else {;}', | ||
'!a ? b : c', | ||
'a != b ? c : d', | ||
'a !== b ? c : d', | ||
'(( !a )) ? b : c', | ||
'!(( a )) ? b : c', | ||
'if(!(( a ))) b(); else c();', | ||
'if((( !a ))) b(); else c();', | ||
'function a() {return!a ? b : c}', | ||
'function a() {return!(( a )) ? b : c}', | ||
outdent` | ||
function a() { | ||
return ! // comment | ||
a ? b : c; | ||
} | ||
`, | ||
outdent` | ||
function a() { | ||
return (! // ReturnStatement argument is parenthesized | ||
a ? b : c); | ||
} | ||
`, | ||
outdent` | ||
function a() { | ||
return ( | ||
! // UnaryExpression argument is parenthesized | ||
a) ? b : c; | ||
} | ||
`, | ||
outdent` | ||
function a() { | ||
throw ! // comment | ||
a ? b : c; | ||
} | ||
`, | ||
'!a ? b : c ? d : e', | ||
'!a ? b : (( c ? d : e ))', | ||
outdent` | ||
a | ||
![] ? b : c | ||
`, | ||
outdent` | ||
a | ||
!+b ? c : d | ||
`, | ||
outdent` | ||
a | ||
!(b) ? c : d | ||
`, | ||
outdent` | ||
a | ||
!b ? c : d | ||
`, | ||
outdent` | ||
if (!a) | ||
b() | ||
else | ||
c() | ||
`, | ||
'if(!a) b(); else c()', | ||
outdent` | ||
function fn() { | ||
if(!a) b(); else return | ||
} | ||
`, | ||
'if(!a) {b()} else {c()}', | ||
'if(!!a) b(); else c();', | ||
'(!!a) ? b() : c();', | ||
outdent` | ||
function fn() { | ||
return!a !== b ? c : d | ||
return((!((a)) != b)) ? c : d | ||
} | ||
`, | ||
outdent` | ||
if (!a) { | ||
b(); | ||
} else if (!c) { | ||
d(); | ||
} else { | ||
e(); | ||
} | ||
`, | ||
], | ||
}); |
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