1 | /**
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2 | * @fileoverview Disallow construction of dense arrays using the Array constructor
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3 | * @author Matt DuVall <http://www.mattduvall.com/>
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4 | */
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5 |
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6 | "use strict";
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7 |
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8 | //------------------------------------------------------------------------------
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9 | // Requirements
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10 | //------------------------------------------------------------------------------
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11 |
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12 | const {
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13 | getVariableByName,
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14 | isClosingParenToken,
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15 | isOpeningParenToken,
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16 | isStartOfExpressionStatement,
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17 | needsPrecedingSemicolon
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18 | } = require("./utils/ast-utils");
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19 |
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20 | //------------------------------------------------------------------------------
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21 | // Rule Definition
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22 | //------------------------------------------------------------------------------
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23 |
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24 | /** @type {import('../shared/types').Rule} */
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25 | module.exports = {
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26 | meta: {
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27 | type: "suggestion",
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28 |
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29 | docs: {
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30 | description: "Disallow `Array` constructors",
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31 | recommended: false,
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32 | url: "https://eslint.org/docs/latest/rules/no-array-constructor"
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33 | },
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34 |
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35 | hasSuggestions: true,
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36 |
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37 | schema: [],
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38 |
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39 | messages: {
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40 | preferLiteral: "The array literal notation [] is preferable.",
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41 | useLiteral: "Replace with an array literal.",
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42 | useLiteralAfterSemicolon: "Replace with an array literal, add preceding semicolon."
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43 | }
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44 | },
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45 |
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46 | create(context) {
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47 |
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48 | const sourceCode = context.sourceCode;
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49 |
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50 | /**
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51 | * Gets the text between the calling parentheses of a CallExpression or NewExpression.
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52 | * @param {ASTNode} node A CallExpression or NewExpression node.
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53 | * @returns {string} The text between the calling parentheses, or an empty string if there are none.
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54 | */
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55 | function getArgumentsText(node) {
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56 | const lastToken = sourceCode.getLastToken(node);
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57 |
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58 | if (!isClosingParenToken(lastToken)) {
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59 | return "";
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60 | }
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61 |
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62 | let firstToken = node.callee;
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63 |
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64 | do {
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65 | firstToken = sourceCode.getTokenAfter(firstToken);
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66 | if (!firstToken || firstToken === lastToken) {
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67 | return "";
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68 | }
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69 | } while (!isOpeningParenToken(firstToken));
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70 |
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71 | return sourceCode.text.slice(firstToken.range[1], lastToken.range[0]);
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72 | }
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73 |
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74 | /**
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75 | * Disallow construction of dense arrays using the Array constructor
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76 | * @param {ASTNode} node node to evaluate
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77 | * @returns {void}
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78 | * @private
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79 | */
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80 | function check(node) {
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81 | if (
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82 | node.callee.type !== "Identifier" ||
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83 | node.callee.name !== "Array" ||
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84 | node.arguments.length === 1 &&
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85 | node.arguments[0].type !== "SpreadElement") {
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86 | return;
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87 | }
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88 |
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89 | const variable = getVariableByName(sourceCode.getScope(node), "Array");
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90 |
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91 | /*
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92 | * Check if `Array` is a predefined global variable: predefined globals have no declarations,
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93 | * meaning that the `identifiers` list of the variable object is empty.
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94 | */
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95 | if (variable && variable.identifiers.length === 0) {
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96 | const argsText = getArgumentsText(node);
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97 | let fixText;
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98 | let messageId;
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99 |
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100 | /*
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101 | * Check if the suggested change should include a preceding semicolon or not.
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102 | * Due to JavaScript's ASI rules, a missing semicolon may be inserted automatically
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103 | * before an expression like `Array()` or `new Array()`, but not when the expression
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104 | * is changed into an array literal like `[]`.
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105 | */
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106 | if (isStartOfExpressionStatement(node) && needsPrecedingSemicolon(sourceCode, node)) {
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107 | fixText = `;[${argsText}]`;
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108 | messageId = "useLiteralAfterSemicolon";
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109 | } else {
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110 | fixText = `[${argsText}]`;
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111 | messageId = "useLiteral";
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112 | }
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113 |
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114 | context.report({
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115 | node,
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116 | messageId: "preferLiteral",
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117 | suggest: [
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118 | {
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119 | messageId,
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120 | fix: fixer => fixer.replaceText(node, fixText)
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121 | }
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122 | ]
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123 | });
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124 | }
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125 | }
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126 |
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127 | return {
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128 | CallExpression: check,
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129 | NewExpression: check
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130 | };
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131 |
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132 | }
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133 | };
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