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Add regexp/no-empty-character-class rule (#329)
* Add `regexp/no-empty-character-class` rule * Add comment * update no-empty-character-class * Update lib/rules/no-empty-character-class.ts Co-authored-by: Michael Schmidt <[email protected]> * Update lib/rules/no-empty-character-class.ts Co-authored-by: Michael Schmidt <[email protected]> * Update docs/rules/no-empty-character-class.md Co-authored-by: Michael Schmidt <[email protected]> * Update lib/rules/no-empty-character-class.ts Co-authored-by: Michael Schmidt <[email protected]> * Update docs/rules/no-empty-character-class.md Co-authored-by: Michael Schmidt <[email protected]> * update no-empty-character-class Co-authored-by: Michael Schmidt <[email protected]>
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‎README.md

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@@ -108,6 +108,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
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| [regexp/no-dupe-disjunctions](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-dupe-disjunctions.html) | disallow duplicate disjunctions | :star: |
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| [regexp/no-empty-alternative](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-empty-alternative.html) | disallow alternatives without elements | :star: |
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| [regexp/no-empty-capturing-group](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-empty-capturing-group.html) | disallow capturing group that captures empty. | :star: |
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| [regexp/no-empty-character-class](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-empty-character-class.html) | disallow character classes that match no characters | |
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| [regexp/no-empty-group](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-empty-group.html) | disallow empty group | :star: |
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| [regexp/no-empty-lookarounds-assertion](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-empty-lookarounds-assertion.html) | disallow empty lookahead assertion or empty lookbehind assertion | :star: |
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| [regexp/no-escape-backspace](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-escape-backspace.html) | disallow escape backspace (`[\b]`) | :star: |

‎docs/rules/README.md

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@@ -17,6 +17,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
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| [regexp/no-dupe-disjunctions](./no-dupe-disjunctions.md) | disallow duplicate disjunctions | :star: |
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| [regexp/no-empty-alternative](./no-empty-alternative.md) | disallow alternatives without elements | :star: |
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| [regexp/no-empty-capturing-group](./no-empty-capturing-group.md) | disallow capturing group that captures empty. | :star: |
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| [regexp/no-empty-character-class](./no-empty-character-class.md) | disallow character classes that match no characters | |
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| [regexp/no-empty-group](./no-empty-group.md) | disallow empty group | :star: |
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| [regexp/no-empty-lookarounds-assertion](./no-empty-lookarounds-assertion.md) | disallow empty lookahead assertion or empty lookbehind assertion | :star: |
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| [regexp/no-escape-backspace](./no-escape-backspace.md) | disallow escape backspace (`[\b]`) | :star: |

‎docs/rules/no-empty-character-class.md

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---
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pageClass: "rule-details"
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sidebarDepth: 0
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title: "regexp/no-empty-character-class"
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description: "disallow character classes that match no characters"
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---
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# regexp/no-empty-character-class
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> disallow character classes that match no characters
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- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
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## :book: Rule Details
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This rule reports character classes that cannot match any characters.
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Character classes that cannot match any characters are either empty or negated character classes of elements that contain all characters.
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The reports for this rule include reports for the ESLint core [no-empty-character-class] rule. That is, if you use this rule, you can turn off the ESLint core [no-empty-character-class] rule.
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<eslint-code-block>
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```js
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/* eslint regexp/no-empty-character-class: "error" */
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/* ✓ GOOD */
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var foo = /abc[d]/;
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var foo = /abc[a-z]/;
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var foo = /[^]/;
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var foo = /[\s\S]/;
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/* ✗ BAD */
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var foo = /abc[]/;
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var foo = /[^\s\S]/;
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```
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</eslint-code-block>
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## :wrench: Options
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Nothing.
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## :books: Further reading
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- [no-empty-character-class]
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[no-empty-character-class]: https://eslint.org/docs/rules/no-empty-character-class
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## :mag: Implementation
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- [Rule source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/lib/rules/no-empty-character-class.ts)
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- [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/no-empty-character-class.ts)

‎lib/configs/recommended.ts

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// The ESLint rule will report fewer cases than our rule
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"no-invalid-regexp": "off",
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"no-useless-backreference": "off",
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// TODO Switch in the major version.
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// "no-empty-character-class": "off",
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// eslint-plugin-regexp rules
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"regexp/confusing-quantifier": "warn",

‎lib/rules/no-empty-character-class.ts

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import { matchesNoCharacters } from "regexp-ast-analysis"
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import type { RegExpVisitor } from "regexpp/visitor"
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import type { RegExpContext } from "../utils"
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import { createRule, defineRegexpVisitor } from "../utils"
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export default createRule("no-empty-character-class", {
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meta: {
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docs: {
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description: "disallow character classes that match no characters",
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category: "Possible Errors",
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// TODO Switch to recommended in the major version.
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// recommended: true,
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recommended: false,
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},
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schema: [],
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messages: {
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empty:
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"This character class matches no characters because it is empty.",
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cannotMatchAny: "This character class cannot match any characters.",
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},
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type: "suggestion", // "problem",
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},
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create(context) {
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/**
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* Create visitor
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*/
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function createVisitor(
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regexpContext: RegExpContext,
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): RegExpVisitor.Handlers {
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const { node, getRegexpLocation, flags } = regexpContext
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return {
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onCharacterClassEnter(ccNode) {
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if (matchesNoCharacters(ccNode, flags)) {
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context.report({
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node,
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loc: getRegexpLocation(ccNode),
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messageId: ccNode.elements.length
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? "cannotMatchAny"
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: "empty",
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})
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}
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},
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}
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}
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return defineRegexpVisitor(context, {
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createVisitor,
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})
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},
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})

‎lib/utils/rules.ts

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import noDupeDisjunctions from "../rules/no-dupe-disjunctions"
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import noEmptyAlternative from "../rules/no-empty-alternative"
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import noEmptyCapturingGroup from "../rules/no-empty-capturing-group"
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import noEmptyCharacterClass from "../rules/no-empty-character-class"
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import noEmptyGroup from "../rules/no-empty-group"
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import noEmptyLookaroundsAssertion from "../rules/no-empty-lookarounds-assertion"
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import noEscapeBackspace from "../rules/no-escape-backspace"
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noDupeDisjunctions,
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noEmptyAlternative,
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noEmptyCapturingGroup,
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noEmptyCharacterClass,
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noEmptyGroup,
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noEmptyLookaroundsAssertion,
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noEscapeBackspace,

‎tests/lib/rules/no-empty-character-class.ts

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import { RuleTester } from "eslint"
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import rule from "../../../lib/rules/no-empty-character-class"
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const tester = new RuleTester({
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parserOptions: {
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ecmaVersion: 2020,
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sourceType: "module",
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},
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})
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tester.run("no-empty-character-class", rule as any, {
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valid: [
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`/[a]/`,
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`/[a-z]/`,
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`/[a]?/`,
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`/[a]*/`,
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`/[[]/`,
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String.raw`/\[]/`,
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`/[^]/`,
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`/[()]/`,
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`/[ ]/`,
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String.raw`/[\s\S]/`,
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String.raw`/[\da-zA-Z_\W]/`,
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],
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invalid: [
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{
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code: `/[]/`,
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errors: [
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{
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message:
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"This character class matches no characters because it is empty.",
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line: 1,
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column: 2,
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},
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],
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},
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{
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code: `/abc[]/`,
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errors: [
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{
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message:
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"This character class matches no characters because it is empty.",
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line: 1,
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column: 5,
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},
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],
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},
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{
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code: `/([])/`,
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errors: [
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{
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message:
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"This character class matches no characters because it is empty.",
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line: 1,
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column: 3,
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},
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],
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},
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{
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code: `new RegExp("[]");`,
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errors: [
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{
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message:
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"This character class matches no characters because it is empty.",
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line: 1,
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column: 13,
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},
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],
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},
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{
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code: String.raw`/[^\s\S]/`,
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errors: ["This character class cannot match any characters."],
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},
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{
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code: String.raw`/[^\da-zA-Z_\W]/`,
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errors: ["This character class cannot match any characters."],
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},
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],
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})

‎tools/update-rulesets.ts

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// The ESLint rule will report fewer cases than our rule
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"no-invalid-regexp": "off",
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"no-useless-backreference": "off",
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// TODO Switch in the major version.
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// "no-empty-character-class": "off",
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// eslint-plugin-regexp rules
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${rules

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