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Add regexp/no-useless-escape rule (#44)
* Add `regexp/no-useless-escape` rule * update
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‎README.md

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@@ -91,6 +91,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
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| [regexp/no-octal](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-octal.html) | disallow octal escape sequence | :star: |
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| [regexp/no-useless-backreference](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-backreference.html) | disallow useless backreferences in regular expressions | |
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| [regexp/no-useless-character-class](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-character-class.html) | disallow character class with one character | :wrench: |
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| [regexp/no-useless-escape](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-escape.html) | disallow unnecessary escape characters in RegExp | |
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| [regexp/no-useless-exactly-quantifier](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-exactly-quantifier.html) | disallow unnecessary exactly quantifier | :star: |
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| [regexp/no-useless-non-capturing-group](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-non-capturing-group.html) | disallow unnecessary Non-capturing group | :wrench: |
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| [regexp/no-useless-non-greedy](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-non-greedy.html) | disallow unnecessary quantifier non-greedy (`?`) | :wrench: |

‎docs/rules/README.md

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@@ -23,6 +23,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
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| [regexp/no-octal](./no-octal.md) | disallow octal escape sequence | :star: |
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| [regexp/no-useless-backreference](./no-useless-backreference.md) | disallow useless backreferences in regular expressions | |
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| [regexp/no-useless-character-class](./no-useless-character-class.md) | disallow character class with one character | :wrench: |
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| [regexp/no-useless-escape](./no-useless-escape.md) | disallow unnecessary escape characters in RegExp | |
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| [regexp/no-useless-exactly-quantifier](./no-useless-exactly-quantifier.md) | disallow unnecessary exactly quantifier | :star: |
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| [regexp/no-useless-non-capturing-group](./no-useless-non-capturing-group.md) | disallow unnecessary Non-capturing group | :wrench: |
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| [regexp/no-useless-non-greedy](./no-useless-non-greedy.md) | disallow unnecessary quantifier non-greedy (`?`) | :wrench: |

‎docs/rules/no-useless-escape.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-useless-escape"
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description: "disallow unnecessary escape characters in RegExp"
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---
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# regexp/no-useless-escape
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> disallow unnecessary escape characters in RegExp
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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 unnecessary escape characters in RegExp.
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You may be able to find another mistake by finding unnecessary escapes.
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<eslint-code-block>
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```js
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/* eslint regexp/no-useless-escape: "error" */
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/* ✓ GOOD */
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var foo = /\[/
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var foo = /\\/
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/* ✗ BAD */
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var foo = /\a/
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var foo = /\x7/
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var foo = /\u41/
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var foo = /\u{[41]}/
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```
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</eslint-code-block>
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This rule checks for unnecessary escapes with deeper regular expression parsing than the ESLint core's [no-useless-escape] rule.
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<eslint-code-block>
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```js
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/* eslint no-useless-escape: "error" */
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// no-useless-escape rule also reports it.
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var foo = /\a/
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// no-useless-escape rule DOES NOT report it.
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var foo = /\x7/
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var foo = /\u41/
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var foo = /\u{[41]}/
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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-useless-escape]
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[no-useless-escape]: https://eslint.org/docs/rules/no-useless-escape
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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-useless-escape.ts)
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- [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/no-useless-escape.ts)

‎lib/rules/no-useless-escape.ts

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import type { Expression } from "estree"
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import type { RegExpVisitor } from "regexpp/visitor"
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import type { Character } from "regexpp/ast"
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import {
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createRule,
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defineRegexpVisitor,
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getRegexpLocation,
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CP_BACK_SLASH,
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CP_STAR,
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CP_CLOSING_BRACKET,
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CP_SLASH,
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CP_CARET,
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CP_DOT,
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CP_DOLLAR,
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CP_PLUS,
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CP_QUESTION,
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CP_CLOSING_BRACE,
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CP_CLOSING_PAREN,
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CP_OPENING_BRACE,
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CP_OPENING_BRACKET,
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CP_OPENING_PAREN,
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CP_PIPE,
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CP_MINUS,
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canUnwrapped,
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} from "../utils"
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const REGEX_CHAR_CLASS_ESCAPES = new Set([
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CP_BACK_SLASH, // \\
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CP_CLOSING_BRACKET, // ]
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CP_MINUS, // -
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])
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const REGEX_ESCAPES = new Set([
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CP_BACK_SLASH, // \\
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CP_SLASH, // /
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CP_CARET, // ^
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CP_DOT, // .
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CP_DOLLAR, // $
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CP_STAR, // *
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CP_PLUS, // +
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CP_QUESTION, // ?
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CP_OPENING_BRACKET, // [
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CP_CLOSING_BRACKET, // ]
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CP_OPENING_BRACE, // {
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CP_CLOSING_BRACE, // }
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CP_PIPE, // |
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CP_OPENING_PAREN, // (
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CP_CLOSING_PAREN, // )
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])
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export default createRule("no-useless-escape", {
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meta: {
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docs: {
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description: "disallow unnecessary escape characters in RegExp",
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// TODO 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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unnecessary: "Unnecessary escape character: \\{{character}}.",
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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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const sourceCode = context.getSourceCode()
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/**
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* Create visitor
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* @param node
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*/
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function createVisitor(node: Expression): RegExpVisitor.Handlers {
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/** Report */
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function report(
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cNode: Character,
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offset: number,
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character: string,
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) {
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context.report({
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node,
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loc: getRegexpLocation(sourceCode, node, cNode, [
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offset,
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offset + 1,
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]),
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messageId: "unnecessary",
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data: {
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character,
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},
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})
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}
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let inCharacterClass = false
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return {
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onCharacterClassEnter() {
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inCharacterClass = true
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},
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onCharacterClassLeave() {
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inCharacterClass = false
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},
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onCharacterEnter(cNode) {
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if (cNode.raw.startsWith("\\")) {
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// escapes
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const char = cNode.raw.slice(1)
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if (char === String.fromCodePoint(cNode.value)) {
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const allowedEscapes = inCharacterClass
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? REGEX_CHAR_CLASS_ESCAPES
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: REGEX_ESCAPES
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if (allowedEscapes.has(cNode.value)) {
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return
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}
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if (inCharacterClass && cNode.value === CP_CARET) {
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const target =
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cNode.parent.type === "CharacterClassRange"
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? cNode.parent
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: cNode
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const parent = target.parent
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if (parent.type === "CharacterClass") {
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if (parent.elements.indexOf(target) === 0) {
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// e.g. /[\^]/
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return
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}
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}
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}
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if (!canUnwrapped(cNode, char)) {
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return
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}
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report(cNode, 0, char)
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}
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// else if (cNode.value === CP_BACK_SLASH) {
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// // Invalid escape for /\c/
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// if (cNode.raw === "\\") {
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// const parent = cNode.parent
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// if (
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// parent.type === "Alternative" ||
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// parent.type === "CharacterClass"
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// ) {
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// const next =
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// parent.elements[
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// parent.elements.indexOf(cNode) + 1
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// ]
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// if (next && next.raw.length === 1) {
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// report(cNode, 0, next.raw)
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// }
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// }
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// }
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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/index.ts

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@@ -3,12 +3,7 @@ import type { RuleListener, RuleModule, PartialRuleModule } from "../types"
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import type { RegExpVisitor } from "regexpp/visitor"
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import type {
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Alternative,
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AnyCharacterSet,
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Assertion,
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Backreference,
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CapturingGroup,
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CharacterClass,
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Group,
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Element,
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Node as RegExpNode,
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Quantifier,
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} from "regexpp/ast"
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*/
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export function canUnwrapped(
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/* eslint-enable complexity -- X( */
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node:
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| CharacterClass
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| Group
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| CapturingGroup
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| Assertion
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| Quantifier
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| AnyCharacterSet
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| Backreference,
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node: Element,
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text: string,
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): boolean {
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const { alternative, index } = getAlternativeAndIndex()
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const parent = node.parent
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let target: Element, alternative: Alternative
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if (parent.type === "Quantifier") {
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alternative = parent.parent
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target = parent
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} else if (parent.type === "Alternative") {
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alternative = parent
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target = node
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} else {
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return true
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}
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const index = alternative.elements.indexOf(target)
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if (index === 0) {
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return true
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}
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}
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return true
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/** Get alternative and element index */
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function getAlternativeAndIndex() {
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const parent = node.parent
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let target:
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| CharacterClass
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| Group
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| CapturingGroup
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| Assertion
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| Quantifier
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| AnyCharacterSet
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| Backreference,
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alt: Alternative
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if (parent.type === "Quantifier") {
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alt = parent.parent
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target = parent
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} else {
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alt = parent
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target = node
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}
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return {
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alternative: alt,
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index: alt.elements.indexOf(target),
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}
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}
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}

‎lib/utils/rules.ts

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@@ -11,6 +11,7 @@ import noInvisibleCharacter from "../rules/no-invisible-character"
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import noOctal from "../rules/no-octal"
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import noUselessBackreference from "../rules/no-useless-backreference"
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import noUselessCharacterClass from "../rules/no-useless-character-class"
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import noUselessEscape from "../rules/no-useless-escape"
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import noUselessExactlyQuantifier from "../rules/no-useless-exactly-quantifier"
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import noUselessNonCapturingGroup from "../rules/no-useless-non-capturing-group"
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import noUselessNonGreedy from "../rules/no-useless-non-greedy"
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noOctal,
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noUselessBackreference,
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noUselessCharacterClass,
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noUselessEscape,
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noUselessExactlyQuantifier,
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noUselessNonCapturingGroup,
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noUselessNonGreedy,

‎lib/utils/unicode.ts

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export const CP_CR = 13
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export const CP_SPACE = " ".codePointAt(0)!
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export const CP_BAN = "!".codePointAt(0)!
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export const CP_DOLLAR = "$".codePointAt(0)!
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export const CP_OPENING_PAREN = "(".codePointAt(0)!
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export const CP_CLOSING_PAREN = ")".codePointAt(0)!
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export const CP_STAR = "*".codePointAt(0)!
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export const CP_PLUS = "+".codePointAt(0)!
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export const CP_MINUS = "-".codePointAt(0)!
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export const CP_DOT = ".".codePointAt(0)!
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export const CP_SLASH = "/".codePointAt(0)!
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export const CP_COLON = ":".codePointAt(0)!
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export const CP_QUESTION = "?".codePointAt(0)!
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export const CP_AT = "@".codePointAt(0)!
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export const CP_OPENING_BRACKET = "[".codePointAt(0)!
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export const CP_BACK_SLASH = "\\".codePointAt(0)!
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export const CP_CLOSING_BRACKET = "]".codePointAt(0)!
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export const CP_CARET = "^".codePointAt(0)!
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export const CP_BACKTICK = "`".codePointAt(0)!
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export const CP_OPENING_BRACE = "{".codePointAt(0)!
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export const CP_PIPE = "|".codePointAt(0)!
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export const CP_CLOSING_BRACE = "}".codePointAt(0)!
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export const CP_TILDE = "~".codePointAt(0)!
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export const CP_NEL = "\u0085".codePointAt(0)!
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export const CP_NBSP = "\u00a0".codePointAt(0)!

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