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qwen/nodejs/node_modules/eslint/lib/rules/no-useless-escape.js

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