no-useless-backreference.js

/**
 * @fileoverview Rule to disallow useless backreferences in regular expressions
 * @author Milos Djermanovic
 */

"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const { CALL, CONSTRUCT, ReferenceTracker, getStringIfConstant } = require("eslint-utils");
const { RegExpParser, visitRegExpAST } = require("regexpp");

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

const parser = new RegExpParser();

/**
 * Finds the path from the given `regexpp` AST node to the root node.
 * @param {regexpp.Node} node Node.
 * @returns {regexpp.Node[]} Array that starts with the given node and ends with the root node.
 */
function getPathToRoot(node) {
    const path = [];
    let current = node;

    do {
        path.push(current);
        current = current.parent;
    } while (current);

    return path;
}

/**
 * Determines whether the given `regexpp` AST node is a lookaround node.
 * @param {regexpp.Node} node Node.
 * @returns {boolean} `true` if it is a lookaround node.
 */
function isLookaround(node) {
    return node.type === "Assertion" &&
        (node.kind === "lookahead" || node.kind === "lookbehind");
}

/**
 * Determines whether the given `regexpp` AST node is a negative lookaround node.
 * @param {regexpp.Node} node Node.
 * @returns {boolean} `true` if it is a negative lookaround node.
 */
function isNegativeLookaround(node) {
    return isLookaround(node) && node.negate;
}

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = {
    meta: {
        type: "problem",

        docs: {
            description: "disallow useless backreferences in regular expressions",
            category: "Possible Errors",
            recommended: false,
            url: "https://eslint.org/docs/rules/no-useless-backreference"
        },