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app_vue/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");
+
+//------------------------------------------------------------------------------
+// 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"));
+
+/**
+ * Parses a regular expression into a list of characters with character class info.
+ * @param {string} regExpText The raw text used to create the regular expression
+ * @returns {Object[]} A list of characters, each with info on escaping and whether they're in a character class.
+ * @example
+ *
+ * parseRegExp('a\\b[cd-]')
+ *
+ * returns:
+ * [
+ *   {text: 'a', index: 0, escaped: false, inCharClass: false, startsCharClass: false, endsCharClass: false},
+ *   {text: 'b', index: 2, escaped: true, inCharClass: false, startsCharClass: false, endsCharClass: false},
+ *   {text: 'c', index: 4, escaped: false, inCharClass: true, startsCharClass: true, endsCharClass: false},
+ *   {text: 'd', index: 5, escaped: false, inCharClass: true, startsCharClass: false, endsCharClass: false},
+ *   {text: '-', index: 6, escaped: false, inCharClass: true, startsCharClass: false, endsCharClass: false}
+ * ]
+ */
+function parseRegExp(regExpText) {
+    const charList = [];
+
+    regExpText.split("").reduce((state, char, index) => {
+        if (!state.escapeNextChar) {
+            if (char === "\\") {
+                return Object.assign(state, { escapeNextChar: true });
+            }
+            if (char === "[" && !state.inCharClass) {
+                return Object.assign(state, { inCharClass: true, startingCharClass: true });
+            }
+            if (char === "]" && state.inCharClass) {
+                if (charList.length && charList[charList.length - 1].inCharClass) {
+                    charList[charList.length - 1].endsCharClass = true;
+                }
+                return Object.assign(state, { inCharClass: false, startingCharClass: false });
+            }
+        }
+        charList.push({
+            text: char,
+            index,
+            escaped: state.escapeNextChar,
+            inCharClass: state.inCharClass,
+            startsCharClass: state.startingCharClass,
+            endsCharClass: false
+        });
+        return Object.assign(state, { escapeNextChar: false, startingCharClass: false });
+    }, { escapeNextChar: false, inCharClass: false, startingCharClass: false });
+
+    return charList;
+}
+
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "disallow unnecessary escape characters",
+            category: "Best Practices",
+            recommended: true,
+            url: "https://eslint.org/docs/rules/no-useless-escape",
+            suggestion: true
+        },
+
+        messages: {
+            unnecessaryEscape: "Unnecessary escape character: \\{{character}}.",
+            removeEscape: "Remove the `\\`. This maintains the current functionality.",
+            escapeBackslash: "Replace the `\\` with `\\\\` to include the actual backslash character."
+        },
+
+        schema: []
+    },
+
+    create(context) {
+        const sourceCode = context.getSourceCode();
+
+        /**
+         * 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)
+         * @returns {void}
+         */
+        function report(node, startOffset, character) {
+            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: [
+                    {
+                        messageId: "removeEscape",
+                        fix(fixer) {
+                            return fixer.removeRange(range);
+                        }
+                    },
+                    {
+                        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 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) {
+                parseRegExp(node.regex.pattern)
+
+                    /*
+                     * 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.
+                     */
+                    .filter(charInfo => !(charInfo.text === "-" && charInfo.inCharClass && !charInfo.startsCharClass && !charInfo.endsCharClass))
+
+                    /*
+                     * 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.
+                     */
+                    .filter(charInfo => !(charInfo.text === "^" && charInfo.startsCharClass))
+
+                    // Filter out characters that aren't escaped.
+                    .filter(charInfo => charInfo.escaped)
+
+                    // Filter out characters that are valid to escape, based on their position in the regular expression.
+                    .filter(charInfo => !(charInfo.inCharClass ? REGEX_GENERAL_ESCAPES : REGEX_NON_CHARCLASS_ESCAPES).has(charInfo.text))
+
+                    // Report all the remaining characters.
+                    .forEach(charInfo => report(node, charInfo.index, charInfo.text));
+            }
+
+        }
+
+        return {
+            Literal: check,
+            TemplateElement: check
+        };
+    }
+};