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334 lines
13 KiB
334 lines
13 KiB
1 month ago
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/**
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* @fileoverview Look for useless escapes in strings and regexes
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* @author Onur Temizkan
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*/
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"use strict";
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const astUtils = require("./utils/ast-utils");
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const { RegExpParser, visitRegExpAST } = require("@eslint-community/regexpp");
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/**
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* @typedef {import('@eslint-community/regexpp').AST.CharacterClass} CharacterClass
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* @typedef {import('@eslint-community/regexpp').AST.ExpressionCharacterClass} ExpressionCharacterClass
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*/
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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/**
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* Returns the union of two sets.
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* @param {Set} setA The first set
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* @param {Set} setB The second set
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* @returns {Set} The union of the two sets
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*/
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function union(setA, setB) {
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return new Set(function *() {
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yield* setA;
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yield* setB;
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}());
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}
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const VALID_STRING_ESCAPES = union(new Set("\\nrvtbfux"), astUtils.LINEBREAKS);
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const REGEX_GENERAL_ESCAPES = new Set("\\bcdDfnpPrsStvwWxu0123456789]");
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const REGEX_NON_CHARCLASS_ESCAPES = union(REGEX_GENERAL_ESCAPES, new Set("^/.$*+?[{}|()Bk"));
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/*
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* Set of characters that require escaping in character classes in `unicodeSets` mode.
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* ( ) [ ] { } / - \ | are ClassSetSyntaxCharacter
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*/
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const REGEX_CLASSSET_CHARACTER_ESCAPES = union(REGEX_GENERAL_ESCAPES, new Set("q/[{}|()-"));
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/*
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* A single character set of ClassSetReservedDoublePunctuator.
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* && !! ## $$ %% ** ++ ,, .. :: ;; << == >> ?? @@ ^^ `` ~~ are ClassSetReservedDoublePunctuator
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*/
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const REGEX_CLASS_SET_RESERVED_DOUBLE_PUNCTUATOR = new Set("!#$%&*+,.:;<=>?@^`~");
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/** @type {import('../shared/types').Rule} */
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "Disallow unnecessary escape characters",
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recommended: true,
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url: "https://eslint.org/docs/latest/rules/no-useless-escape"
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},
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hasSuggestions: true,
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messages: {
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unnecessaryEscape: "Unnecessary escape character: \\{{character}}.",
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removeEscape: "Remove the `\\`. This maintains the current functionality.",
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removeEscapeDoNotKeepSemantics: "Remove the `\\` if it was inserted by mistake.",
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escapeBackslash: "Replace the `\\` with `\\\\` to include the actual backslash character."
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},
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schema: []
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},
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create(context) {
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const sourceCode = context.sourceCode;
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const parser = new RegExpParser();
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/**
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* Reports a node
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* @param {ASTNode} node The node to report
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* @param {number} startOffset The backslash's offset from the start of the node
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* @param {string} character The uselessly escaped character (not including the backslash)
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* @param {boolean} [disableEscapeBackslashSuggest] `true` if escapeBackslash suggestion should be turned off.
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* @returns {void}
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*/
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function report(node, startOffset, character, disableEscapeBackslashSuggest) {
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const rangeStart = node.range[0] + startOffset;
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const range = [rangeStart, rangeStart + 1];
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const start = sourceCode.getLocFromIndex(rangeStart);
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context.report({
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node,
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loc: {
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start,
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end: { line: start.line, column: start.column + 1 }
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},
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messageId: "unnecessaryEscape",
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data: { character },
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suggest: [
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{
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// Removing unnecessary `\` characters in a directive is not guaranteed to maintain functionality.
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messageId: astUtils.isDirective(node.parent)
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? "removeEscapeDoNotKeepSemantics" : "removeEscape",
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fix(fixer) {
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return fixer.removeRange(range);
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}
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},
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...disableEscapeBackslashSuggest
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? []
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: [
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{
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messageId: "escapeBackslash",
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fix(fixer) {
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return fixer.insertTextBeforeRange(range, "\\");
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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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* Checks if the escape character in given string slice is unnecessary.
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* @private
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* @param {ASTNode} node node to validate.
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* @param {string} match string slice to validate.
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* @returns {void}
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*/
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function validateString(node, match) {
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const isTemplateElement = node.type === "TemplateElement";
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const escapedChar = match[0][1];
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let isUnnecessaryEscape = !VALID_STRING_ESCAPES.has(escapedChar);
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let isQuoteEscape;
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if (isTemplateElement) {
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isQuoteEscape = escapedChar === "`";
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if (escapedChar === "$") {
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// Warn if `\$` is not followed by `{`
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isUnnecessaryEscape = match.input[match.index + 2] !== "{";
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} else if (escapedChar === "{") {
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/*
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* Warn if `\{` is not preceded by `$`. If preceded by `$`, escaping
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* is necessary and the rule should not warn. If preceded by `/$`, the rule
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* will warn for the `/$` instead, as it is the first unnecessarily escaped character.
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*/
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isUnnecessaryEscape = match.input[match.index - 1] !== "$";
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}
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} else {
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isQuoteEscape = escapedChar === node.raw[0];
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}
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if (isUnnecessaryEscape && !isQuoteEscape) {
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report(node, match.index, match[0].slice(1));
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}
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}
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/**
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* Checks if the escape character in given regexp is unnecessary.
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* @private
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* @param {ASTNode} node node to validate.
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* @returns {void}
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*/
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function validateRegExp(node) {
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const { pattern, flags } = node.regex;
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let patternNode;
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const unicode = flags.includes("u");
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const unicodeSets = flags.includes("v");
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try {
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patternNode = parser.parsePattern(pattern, 0, pattern.length, { unicode, unicodeSets });
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} catch {
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// Ignore regular expressions with syntax errors
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return;
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}
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/** @type {(CharacterClass | ExpressionCharacterClass)[]} */
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const characterClassStack = [];
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visitRegExpAST(patternNode, {
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onCharacterClassEnter: characterClassNode => characterClassStack.unshift(characterClassNode),
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onCharacterClassLeave: () => characterClassStack.shift(),
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onExpressionCharacterClassEnter: characterClassNode => characterClassStack.unshift(characterClassNode),
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onExpressionCharacterClassLeave: () => characterClassStack.shift(),
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onCharacterEnter(characterNode) {
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if (!characterNode.raw.startsWith("\\")) {
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// It's not an escaped character.
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return;
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}
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const escapedChar = characterNode.raw.slice(1);
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if (escapedChar !== String.fromCodePoint(characterNode.value)) {
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// It's a valid escape.
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return;
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}
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let allowedEscapes;
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if (characterClassStack.length) {
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allowedEscapes = unicodeSets ? REGEX_CLASSSET_CHARACTER_ESCAPES : REGEX_GENERAL_ESCAPES;
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} else {
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allowedEscapes = REGEX_NON_CHARCLASS_ESCAPES;
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}
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if (allowedEscapes.has(escapedChar)) {
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return;
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}
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const reportedIndex = characterNode.start + 1;
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let disableEscapeBackslashSuggest = false;
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if (characterClassStack.length) {
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const characterClassNode = characterClassStack[0];
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if (escapedChar === "^") {
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/*
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* The '^' character is also a special case; it must always be escaped outside of character classes, but
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* it only needs to be escaped in character classes if it's at the beginning of the character class. To
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* account for this, consider it to be a valid escape character outside of character classes, and filter
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* out '^' characters that appear at the start of a character class.
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*/
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if (characterClassNode.start + 1 === characterNode.start) {
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return;
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}
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}
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if (!unicodeSets) {
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if (escapedChar === "-") {
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/*
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* The '-' character is a special case, because it's only valid to escape it if it's in a character
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* class, and is not at either edge of the character class. To account for this, don't consider '-'
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* characters to be valid in general, and filter out '-' characters that appear in the middle of a
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* character class.
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*/
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if (characterClassNode.start + 1 !== characterNode.start && characterNode.end !== characterClassNode.end - 1) {
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return;
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}
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}
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} else { // unicodeSets mode
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if (REGEX_CLASS_SET_RESERVED_DOUBLE_PUNCTUATOR.has(escapedChar)) {
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// Escaping is valid if it is a ClassSetReservedDoublePunctuator.
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if (pattern[characterNode.end] === escapedChar) {
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return;
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}
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if (pattern[characterNode.start - 1] === escapedChar) {
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if (escapedChar !== "^") {
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return;
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}
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// If the previous character is a `negate` caret(`^`), escape to caret is unnecessary.
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if (!characterClassNode.negate) {
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return;
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}
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const negateCaretIndex = characterClassNode.start + 1;
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if (negateCaretIndex < characterNode.start - 1) {
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return;
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}
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}
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}
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if (characterNode.parent.type === "ClassIntersection" || characterNode.parent.type === "ClassSubtraction") {
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disableEscapeBackslashSuggest = true;
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}
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}
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}
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report(
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node,
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reportedIndex,
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escapedChar,
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disableEscapeBackslashSuggest
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);
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}
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});
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}
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/**
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* Checks if a node has an escape.
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* @param {ASTNode} node node to check.
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* @returns {void}
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*/
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function check(node) {
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const isTemplateElement = node.type === "TemplateElement";
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if (
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isTemplateElement &&
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node.parent &&
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node.parent.parent &&
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node.parent.parent.type === "TaggedTemplateExpression" &&
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node.parent === node.parent.parent.quasi
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) {
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// Don't report tagged template literals, because the backslash character is accessible to the tag function.
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return;
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}
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if (typeof node.value === "string" || isTemplateElement) {
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/*
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* JSXAttribute doesn't have any escape sequence: https://facebook.github.io/jsx/.
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* In addition, backticks are not supported by JSX yet: https://github.com/facebook/jsx/issues/25.
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*/
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if (node.parent.type === "JSXAttribute" || node.parent.type === "JSXElement" || node.parent.type === "JSXFragment") {
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return;
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}
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const value = isTemplateElement ? sourceCode.getText(node) : node.raw;
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const pattern = /\\[^\d]/gu;
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let match;
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while ((match = pattern.exec(value))) {
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validateString(node, match);
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}
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} else if (node.regex) {
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validateRegExp(node);
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}
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}
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return {
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Literal: check,
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TemplateElement: check
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};
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}
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};
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