224 lines
8.7 KiB
JavaScript
224 lines
8.7 KiB
JavaScript
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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("../ast-utils");
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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("\\bcdDfnrsStvwWxu0123456789]");
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const REGEX_NON_CHARCLASS_ESCAPES = union(REGEX_GENERAL_ESCAPES, new Set("^/.$*+?[{}|()B"));
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/**
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* Parses a regular expression into a list of characters with character class info.
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* @param {string} regExpText The raw text used to create the regular expression
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* @returns {Object[]} A list of characters, each with info on escaping and whether they're in a character class.
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* @example
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*
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* parseRegExp('a\\b[cd-]')
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*
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* returns:
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* [
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* {text: 'a', index: 0, escaped: false, inCharClass: false, startsCharClass: false, endsCharClass: false},
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* {text: 'b', index: 2, escaped: true, inCharClass: false, startsCharClass: false, endsCharClass: false},
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* {text: 'c', index: 4, escaped: false, inCharClass: true, startsCharClass: true, endsCharClass: false},
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* {text: 'd', index: 5, escaped: false, inCharClass: true, startsCharClass: false, endsCharClass: false},
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* {text: '-', index: 6, escaped: false, inCharClass: true, startsCharClass: false, endsCharClass: false}
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* ]
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*/
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function parseRegExp(regExpText) {
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const charList = [];
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regExpText.split("").reduce((state, char, index) => {
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if (!state.escapeNextChar) {
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if (char === "\\") {
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return Object.assign(state, { escapeNextChar: true });
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}
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if (char === "[" && !state.inCharClass) {
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return Object.assign(state, { inCharClass: true, startingCharClass: true });
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}
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if (char === "]" && state.inCharClass) {
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if (charList.length && charList[charList.length - 1].inCharClass) {
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charList[charList.length - 1].endsCharClass = true;
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}
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return Object.assign(state, { inCharClass: false, startingCharClass: false });
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}
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}
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charList.push({
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text: char,
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index,
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escaped: state.escapeNextChar,
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inCharClass: state.inCharClass,
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startsCharClass: state.startingCharClass,
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endsCharClass: false
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});
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return Object.assign(state, { escapeNextChar: false, startingCharClass: false });
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}, { escapeNextChar: false, inCharClass: false, startingCharClass: false });
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return charList;
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}
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module.exports = {
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meta: {
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docs: {
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description: "disallow unnecessary escape characters",
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category: "Best Practices",
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recommended: true
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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.getSourceCode();
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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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* @returns {void}
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*/
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function report(node, startOffset, character) {
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context.report({
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node,
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loc: sourceCode.getLocFromIndex(sourceCode.getIndexFromLoc(node.loc.start) + startOffset),
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message: "Unnecessary escape character: \\{{character}}.",
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data: { character }
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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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*
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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 + 1, match[0].slice(1));
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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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*
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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") {
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return;
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}
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const value = isTemplateElement ? node.value.raw : node.raw.slice(1, -1);
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const pattern = /\\[^\d]/g;
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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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parseRegExp(node.regex.pattern)
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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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.filter(charInfo => !(charInfo.text === "-" && charInfo.inCharClass && !charInfo.startsCharClass && !charInfo.endsCharClass))
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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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.filter(charInfo => !(charInfo.text === "^" && charInfo.startsCharClass))
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// Filter out characters that aren't escaped.
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.filter(charInfo => charInfo.escaped)
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// Filter out characters that are valid to escape, based on their position in the regular expression.
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.filter(charInfo => !(charInfo.inCharClass ? REGEX_GENERAL_ESCAPES : REGEX_NON_CHARCLASS_ESCAPES).has(charInfo.text))
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// Report all the remaining characters.
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.forEach(charInfo => report(node, charInfo.index, charInfo.text));
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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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