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regexp/no-extra-lookaround-assertions rule (#482)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,61 @@ | ||
| --- | ||
| pageClass: "rule-details" | ||
| sidebarDepth: 0 | ||
| title: "regexp/no-extra-lookaround-assertions" | ||
| description: "disallow unnecessary nested lookaround assertions" | ||
| --- | ||
| # regexp/no-extra-lookaround-assertions | ||
|
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||
| > disallow unnecessary nested lookaround assertions | ||
| - :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge> | ||
| - :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule. | ||
|
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| ## :book: Rule Details | ||
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| The last positive lookahead assertion within a lookahead assertion is the same without lookahead assertions. | ||
| Also, The first positive lookbehind assertion within a lookbehind assertion is the same without lookbehind assertions. | ||
| They can be inlined or converted to group. | ||
|
|
||
| ```js | ||
| /a(?=b(?=c))/u; /* -> */ /a(?=bc)/u; | ||
| /a(?=b(?=c|C))/u; /* -> */ /a(?=b(?:c|C))/u; | ||
|
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| /(?<=(?<=a)b)c/u; /* -> */ /(?<=ab)c/u; | ||
| /(?<=(?<=a|A)b)c/u; /* -> */ /(?<=(?:a|A)b)c/u; | ||
| ``` | ||
| This rule aims to report and fix these unnecessary lookaround assertions. | ||
| <eslint-code-block fix> | ||
| ```js | ||
| /* eslint regexp/no-extra-lookaround-assertions: "error" */ | ||
|
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||
| /* ✓ GOOD */ | ||
| var ts = 'JavaScript'.replace(/Java(?=Script)/u, 'Type'); | ||
| var java = 'JavaScript'.replace(/(?<=Java)Script/u, ''); | ||
| var re1 = /a(?=bc)/u; | ||
| var re2 = /a(?=b(?:c|C))/u; | ||
| var re3 = /(?<=ab)c/u; | ||
| var re4 = /(?<=(?:a|A)b)c/u; | ||
|
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| /* ✗ BAD */ | ||
| var ts = 'JavaScript'.replace(/Java(?=Scrip(?=t))/u, 'Type'); | ||
| var java = 'JavaScript'.replace(/(?<=(?<=J)ava)Script/u, ''); | ||
| var re1 = /a(?=b(?=c))/u; | ||
| var re2 = /a(?=b(?=c|C))/u; | ||
| var re3 = /(?<=(?<=a)b)c/u; | ||
| var re4 = /(?<=(?<=a|A)b)c/u; | ||
| ``` | ||
| </eslint-code-block> | ||
| ## :wrench: Options | ||
| Nothing. | ||
| ## :mag: Implementation | ||
| - [Rule source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/lib/rules/no-extra-lookaround-assertions.ts) | ||
| - [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/no-extra-lookaround-assertions.ts) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,119 @@ | ||
| import type { LookaroundAssertion } from "regexpp/ast" | ||
| import type { RegExpVisitor } from "regexpp/visitor" | ||
| import type { RegExpContext } from "../utils" | ||
| import { createRule, defineRegexpVisitor } from "../utils" | ||
|
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| export default createRule("no-extra-lookaround-assertions", { | ||
| meta: { | ||
| docs: { | ||
| description: "disallow unnecessary nested lookaround assertions", | ||
| category: "Best Practices", | ||
| // TODO Switch to recommended in the major version. | ||
| // recommended: true, | ||
| recommended: false, | ||
| }, | ||
| fixable: "code", | ||
| schema: [], | ||
| messages: { | ||
| canBeInlined: | ||
| "This {{kind}} assertion is useless and can be inlined.", | ||
| canBeConvertedIntoGroup: | ||
| "This {{kind}} assertion is useless and can be converted into a group.", | ||
| }, | ||
| type: "suggestion", | ||
| }, | ||
| create(context) { | ||
| /** | ||
| * Create visitor | ||
| */ | ||
| function createVisitor( | ||
| regexpContext: RegExpContext, | ||
| ): RegExpVisitor.Handlers { | ||
| return { | ||
| onAssertionEnter(aNode) { | ||
| if ( | ||
| aNode.kind === "lookahead" || | ||
| aNode.kind === "lookbehind" | ||
| ) { | ||
| verify(regexpContext, aNode) | ||
| } | ||
| }, | ||
| } | ||
| } | ||
|
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| /** Verify for lookaround assertion */ | ||
| function verify( | ||
| regexpContext: RegExpContext, | ||
| assertion: LookaroundAssertion, | ||
| ) { | ||
| for (const alternative of assertion.alternatives) { | ||
| const nested = at( | ||
| alternative.elements, | ||
| assertion.kind === "lookahead" | ||
| ? // The last positive lookahead assertion within | ||
| // a lookahead assertion is the same without the assertion. | ||
| -1 | ||
| : // The first positive lookbehind assertion within | ||
| // a lookbehind assertion is the same without the assertion. | ||
| 0, | ||
| ) | ||
| if ( | ||
| nested?.type === "Assertion" && | ||
| nested.kind === assertion.kind && | ||
| !nested.negate | ||
| ) { | ||
| reportLookaroundAssertion(regexpContext, nested) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /** Report */ | ||
| function reportLookaroundAssertion( | ||
| { node, getRegexpLocation, fixReplaceNode }: RegExpContext, | ||
| assertion: LookaroundAssertion, | ||
| ) { | ||
| let messageId, replaceText | ||
| if (assertion.alternatives.length === 1) { | ||
| messageId = "canBeInlined" | ||
| // unwrap `(?=` and `)`, `(?<=` and `)` | ||
| replaceText = assertion.alternatives[0].raw | ||
| } else { | ||
| messageId = "canBeConvertedIntoGroup" | ||
| // replace `?=` with `?:`, or `?<=` with `?:` | ||
| replaceText = `(?:${assertion.alternatives | ||
| .map((alt) => alt.raw) | ||
| .join("|")})` | ||
| } | ||
|
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||
| context.report({ | ||
| node, | ||
| loc: getRegexpLocation(assertion), | ||
| messageId, | ||
| data: { | ||
| kind: assertion.kind, | ||
| }, | ||
| fix: fixReplaceNode(assertion, replaceText), | ||
| }) | ||
| } | ||
|
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| return defineRegexpVisitor(context, { | ||
| createVisitor, | ||
| }) | ||
| }, | ||
| }) | ||
|
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| // TODO After dropping support for Node < v16.6.0 we can use native `.at()`. | ||
| /** | ||
| * `.at()` polyfill | ||
| * see https://github.com/tc39/proposal-relative-indexing-method#polyfill | ||
| */ | ||
| function at<T>(array: T[], n: number) { | ||
| // ToInteger() abstract op | ||
| let num = Math.trunc(n) || 0 | ||
| // Allow negative indexing from the end | ||
| if (num < 0) num += array.length | ||
| // OOB access is guaranteed to return undefined | ||
| if (num < 0 || num >= array.length) return undefined | ||
| // Otherwise, this is just normal property access | ||
| return array[num] | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,129 @@ | ||
| import { RuleTester } from "eslint" | ||
| import rule from "../../../lib/rules/no-extra-lookaround-assertions" | ||
|
|
||
| const tester = new RuleTester({ | ||
| parserOptions: { | ||
| ecmaVersion: 2020, | ||
| sourceType: "module", | ||
| }, | ||
| }) | ||
|
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| tester.run("no-extra-lookaround-assertions", rule as any, { | ||
| valid: [ | ||
| `console.log('JavaScript'.replace(/Java(?=Script)/u, 'Type'))`, | ||
| `console.log('JavaScript'.replace(/(?<=Java)Script/u, ''))`, | ||
| ], | ||
| invalid: [ | ||
| { | ||
| code: `console.log('JavaScript'.replace(/Java(?=Scrip(?=t))/u, 'Type'))`, | ||
| output: `console.log('JavaScript'.replace(/Java(?=Script)/u, 'Type'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookahead assertion is useless and can be inlined.", | ||
| column: 47, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: `console.log('JavaScript'.replace(/(?<=(?<=J)ava)Script/u, ''))`, | ||
| output: `console.log('JavaScript'.replace(/(?<=Java)Script/u, ''))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookbehind assertion is useless and can be inlined.", | ||
| column: 39, | ||
| }, | ||
| ], | ||
| }, | ||
| // Within negate | ||
| { | ||
| code: `console.log('JavaScript Java JavaRuntime'.replace(/Java(?!Scrip(?=t))/gu, 'Python'))`, | ||
| output: `console.log('JavaScript Java JavaRuntime'.replace(/Java(?!Script)/gu, 'Python'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookahead assertion is useless and can be inlined.", | ||
| column: 64, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: `console.log('JavaScript TypeScript ActionScript'.replace(/(?<!(?<=J)ava)Script/gu, 'ScriptCompiler'))`, | ||
| output: `console.log('JavaScript TypeScript ActionScript'.replace(/(?<!Java)Script/gu, 'ScriptCompiler'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookbehind assertion is useless and can be inlined.", | ||
| column: 63, | ||
| }, | ||
| ], | ||
| }, | ||
| // Multiple alternatives | ||
| { | ||
| code: `console.log('JavaScriptChecker JavaScriptLinter'.replace(/Java(?=Script(?=Checker|Linter))/gu, 'Type'))`, | ||
| output: `console.log('JavaScriptChecker JavaScriptLinter'.replace(/Java(?=Script(?:Checker|Linter))/gu, 'Type'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookahead assertion is useless and can be converted into a group.", | ||
| column: 72, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: `console.log('JavaScriptChecker JavaScriptLinter'.replace(/Java(?=Script(?=(?:Check|Lint)er))/gu, 'Type'))`, | ||
| output: `console.log('JavaScriptChecker JavaScriptLinter'.replace(/Java(?=Script(?:Check|Lint)er)/gu, 'Type'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookahead assertion is useless and can be inlined.", | ||
| column: 72, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: `console.log('ESLint JSLint TSLint'.replace(/(?<=(?<=J|T)S)Lint/gu, '-Runtime'))`, | ||
| output: `console.log('ESLint JSLint TSLint'.replace(/(?<=(?:J|T)S)Lint/gu, '-Runtime'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookbehind assertion is useless and can be converted into a group.", | ||
| column: 49, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: `console.log('JavaScriptChecker JavaScriptLinter'.replace(/Java(?=Script(?=Checker)|Script(?=Linter))/gu, 'Type'))`, | ||
| output: `console.log('JavaScriptChecker JavaScriptLinter'.replace(/Java(?=ScriptChecker|ScriptLinter)/gu, 'Type'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookahead assertion is useless and can be inlined.", | ||
| column: 72, | ||
| }, | ||
| { | ||
| message: | ||
| "This lookahead assertion is useless and can be inlined.", | ||
| column: 90, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: `console.log('ESLint JSLint TSLint'.replace(/(?<=(?<=J)S|(?<=T)S)Lint/gu, '-Runtime'))`, | ||
| output: `console.log('ESLint JSLint TSLint'.replace(/(?<=JS|TS)Lint/gu, '-Runtime'))`, | ||
| errors: [ | ||
| { | ||
| message: | ||
| "This lookbehind assertion is useless and can be inlined.", | ||
| column: 49, | ||
| }, | ||
| { | ||
| message: | ||
| "This lookbehind assertion is useless and can be inlined.", | ||
| column: 57, | ||
| }, | ||
| ], | ||
| }, | ||
| ], | ||
| }) |