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Fixed ruleset
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‎README.md

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@@ -87,6 +87,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
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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: |
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| [regexp/no-invisible-character](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-invisible-character.html) | disallow invisible raw character | :star::wrench: |
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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-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-two-nums-quantifier](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-two-nums-quantifier.html) | disallow unnecessary `{n,m}` quantifier | :star: |
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| [regexp/prefer-d](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-d.html) | enforce using `\d` | :star::wrench: |

‎docs/rules/README.md

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@@ -19,6 +19,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
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| [regexp/no-escape-backspace](./no-escape-backspace.md) | disallow escape backspace (`[\b]`) | :star: |
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| [regexp/no-invisible-character](./no-invisible-character.md) | disallow invisible raw character | :star::wrench: |
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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-exactly-quantifier](./no-useless-exactly-quantifier.md) | disallow unnecessary exactly quantifier | :star: |
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| [regexp/no-useless-two-nums-quantifier](./no-useless-two-nums-quantifier.md) | disallow unnecessary `{n,m}` quantifier | :star: |
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| [regexp/prefer-d](./prefer-d.md) | enforce using `\d` | :star::wrench: |

‎docs/rules/no-useless-backreference.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-backreference"
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description: "disallow useless backreferences in regular expressions"
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---
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# regexp/no-useless-backreference
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> disallow useless backreferences in regular expressions
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## :book: Rule Details
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This rule is a copy of the ESLint core [no-useless-backreference] rule.
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The [no-useless-backreference] rule was added in ESLint 7.x, but this plugin supports ESLint 6.x.
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Copied to this plugin to allow the same [no-useless-backreference] rules to be used in ESLint 6.x.
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## :wrench: Options
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See [no-useless-backreference] document.
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## :books: Further reading
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- [no-useless-backreference]
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[no-useless-backreference]: https://eslint.org/docs/rules/no-useless-backreference
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## Implementation
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- [Rule source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/lib/rules/no-useless-backreference.ts)
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- [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/no-useless-backreference.js)

‎lib/configs/recommended.ts

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export default {
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import eslint from "eslint"
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export = {
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plugins: ["regexp"],
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rules: {
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// ESLint core rules
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"no-control-regex": "error",
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"no-invalid-regexp": "error",
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"no-misleading-character-class": "error",
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"no-regex-spaces": "error",
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"no-useless-backreference": "error",
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"prefer-regex-literals": "error",
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// If ESLint is 7 or higher, use core rule. If it is 6 or less, use the copied rule.
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[parseInt(eslint.Linter.version[0], 10) >= 7
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? "no-useless-backreference"
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: "regexp/no-useless-backreference"]: "error",
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// eslint-plugin-regexp rules
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"regexp/match-any": "error",

‎lib/rules/no-useless-backreference.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 { Node as RegExpNode, LookaroundAssertion } from "regexpp/ast"
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import { createRule, defineRegexpVisitor } from "../utils"
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/* istanbul ignore file */
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/**
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* Finds the path from the given `regexpp` AST node to the root node.
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* @param {regexpp.Node} node Node.
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* @returns {regexpp.Node[]} Array that starts with the given node and ends with the root node.
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*/
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function getPathToRoot(node: RegExpNode) {
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const path = []
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let current = node
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while (current) {
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path.push(current)
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if (!current.parent) {
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break
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}
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current = current.parent
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}
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return path
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}
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/**
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* Determines whether the given `regexpp` AST node is a lookaround node.
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* @param {regexpp.Node} node Node.
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* @returns {boolean} `true` if it is a lookaround node.
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*/
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function isLookaround(node: RegExpNode): node is LookaroundAssertion {
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return (
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node.type === "Assertion" &&
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(node.kind === "lookahead" || node.kind === "lookbehind")
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)
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}
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/**
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* Determines whether the given `regexpp` AST node is a negative lookaround node.
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* @param {regexpp.Node} node Node.
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* @returns {boolean} `true` if it is a negative lookaround node.
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*/
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function isNegativeLookaround(node: RegExpNode) {
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return isLookaround(node) && node.negate
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}
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/**
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* Get last element
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*/
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function last<T>(arr: T[]): T {
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return arr[arr.length - 1]
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}
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export default createRule("no-useless-backreference", {
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meta: {
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docs: {
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description:
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"disallow useless backreferences in regular expressions",
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recommended: false,
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},
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schema: [],
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messages: {
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nested:
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"Backreference '{{ bref }}' will be ignored. It references group '{{ group }}' from within that group.",
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forward:
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"Backreference '{{ bref }}' will be ignored. It references group '{{ group }}' which appears later in the pattern.",
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backward:
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"Backreference '{{ bref }}' will be ignored. It references group '{{ group }}' which appears before in the same lookbehind.",
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disjunctive:
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"Backreference '{{ bref }}' will be ignored. It references group '{{ group }}' which is in another alternative.",
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intoNegativeLookaround:
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"Backreference '{{ bref }}' will be ignored. It references group '{{ group }}' which is in a negative lookaround.",
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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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* @param node
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*/
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function createVisitor(node: Expression): RegExpVisitor.Handlers {
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return {
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onBackreferenceEnter(bref) {
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const group = bref.resolved,
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brefPath = getPathToRoot(bref),
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groupPath = getPathToRoot(group)
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let messageId = null
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if (brefPath.includes(group)) {
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// group is bref's ancestor => bref is nested ('nested reference') => group hasn't matched yet when bref starts to match.
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messageId = "nested"
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} else {
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// Start from the root to find the lowest common ancestor.
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let i = brefPath.length - 1,
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j = groupPath.length - 1
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do {
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i--
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j--
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} while (brefPath[i] === groupPath[j])
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const indexOfLowestCommonAncestor = j + 1,
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groupCut = groupPath.slice(
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0,
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indexOfLowestCommonAncestor,
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),
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commonPath = groupPath.slice(
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indexOfLowestCommonAncestor,
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),
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lowestCommonLookaround = commonPath.find(
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isLookaround,
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),
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isMatchingBackward =
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lowestCommonLookaround &&
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lowestCommonLookaround.kind === "lookbehind"
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if (!isMatchingBackward && bref.end <= group.start) {
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// bref is left, group is right ('forward reference') => group hasn't matched yet when bref starts to match.
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messageId = "forward"
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} else if (
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isMatchingBackward &&
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group.end <= bref.start
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) {
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// the opposite of the previous when the regex is matching backward in a lookbehind context.
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messageId = "backward"
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} else if (last(groupCut).type === "Alternative") {
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// group's and bref's ancestor nodes below the lowest common ancestor are sibling alternatives => they're disjunctive.
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messageId = "disjunctive"
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} else if (groupCut.some(isNegativeLookaround)) {
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// group is in a negative lookaround which isn't bref's ancestor => group has already failed when bref starts to match.
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messageId = "intoNegativeLookaround"
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}
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}
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if (messageId) {
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context.report({
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node,
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messageId,
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data: {
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bref: bref.raw,
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group: group.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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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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@@ -7,6 +7,7 @@ import noEmptyLookaroundsAssertion from "../rules/no-empty-lookarounds-assertion
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import noEscapeBackspace from "../rules/no-escape-backspace"
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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 noUselessExactlyQuantifier from "../rules/no-useless-exactly-quantifier"
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import noUselessTwoNumsQuantifier from "../rules/no-useless-two-nums-quantifier"
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import preferD from "../rules/prefer-d"
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noEscapeBackspace,
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noInvisibleCharacter,
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noOctal,
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noUselessBackreference,
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noUselessExactlyQuantifier,
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noUselessTwoNumsQuantifier,
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preferD,

‎package.json

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{
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"name": "eslint-plugin-regexp",
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"version": "0.1.0",
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"version": "0.1.1",
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"description": "ESLint plugin for finding RegExp mistakes and RegExp style guide violations.",
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"main": "dist/index.js",
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"files": [

‎tests/lib/rules/no-useless-backreference.ts

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import { RuleTester } from "eslint"
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import rule from "../../../lib/rules/no-useless-backreference"
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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-useless-backreference", rule as any, {
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valid: ["/.(?=(b))\\1/"],
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invalid: [
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{
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code: "/(b)(\\2a)/",
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errors: [{ messageId: "nested" }],
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},
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],
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})

‎tools/update-rulesets.ts

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"no-invalid-regexp",
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"no-misleading-character-class",
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"no-regex-spaces",
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"no-useless-backreference",
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"prefer-regex-literals",
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// "prefer-named-capture-group", // modern
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// "require-unicode-regexp", // modern
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]
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let content = `
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export default {
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import eslint from "eslint"
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export = {
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plugins: ["regexp"],
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rules: {
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// ESLint core rules
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${coreRules.map((ruleName) => `"${ruleName}": "error"`).join(",\n")},
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// If ESLint is 7 or higher, use core rule. If it is 6 or less, use the copied rule.
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[parseInt(eslint.Linter.version[0], 10) >= 7
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? "no-useless-backreference"
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: "regexp/no-useless-backreference"]: "error",
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// eslint-plugin-regexp rules
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${rules

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