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no-negated-condition rule (#1963)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,92 @@ | ||
| # 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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,137 @@ | ||
| /* | ||
| 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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| 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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