1 | /**
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2 | * @fileoverview A rule to disallow `this` keywords outside of classes or class-like objects.
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3 | * @author Toru Nagashima
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4 | */
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5 |
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6 | ;
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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 astUtils = require("../ast-utils");
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13 |
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14 | //------------------------------------------------------------------------------
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15 | // Rule Definition
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16 | //------------------------------------------------------------------------------
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17 |
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18 | module.exports = {
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19 | meta: {
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20 | docs: {
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21 | description: "disallow `this` keywords outside of classes or class-like objects",
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22 | category: "Best Practices",
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23 | recommended: false
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24 | },
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25 |
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26 | schema: []
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27 | },
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28 |
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29 | create(context) {
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30 | const stack = [],
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31 | sourceCode = context.getSourceCode();
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32 |
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33 | let insideClassProperty = false;
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34 |
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35 | /**
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36 | * Gets the current checking context.
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37 | *
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38 | * The return value has a flag that whether or not `this` keyword is valid.
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39 | * The flag is initialized when got at the first time.
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40 | *
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41 | * @returns {{valid: boolean}}
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42 | * an object which has a flag that whether or not `this` keyword is valid.
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43 | */
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44 | stack.getCurrent = function() {
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45 | const current = this[this.length - 1];
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46 |
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47 | if (!current.init) {
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48 | current.init = true;
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49 | current.valid = !astUtils.isDefaultThisBinding(
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50 | current.node,
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51 | sourceCode);
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52 | }
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53 | return current;
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54 | };
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55 |
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56 | /**
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57 | * `this` should be fair game anywhere inside a class property.
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58 | *
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59 | * @returns {void}
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60 | */
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61 | function enterClassProperty() {
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62 | insideClassProperty = true;
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63 | }
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64 |
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65 | /**
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66 | * Back to the normal check.
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67 | * @returns {void}
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68 | */
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69 | function exitClassProperty() {
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70 | insideClassProperty = false;
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71 | }
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72 |
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73 | /**
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74 | * Pushs new checking context into the stack.
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75 | *
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76 | * The checking context is not initialized yet.
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77 | * Because most functions don't have `this` keyword.
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78 | * When `this` keyword was found, the checking context is initialized.
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79 | *
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80 | * @param {ASTNode} node - A function node that was entered.
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81 | * @returns {void}
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82 | */
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83 | function enterFunction(node) {
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84 |
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85 | // `this` can be invalid only under strict mode.
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86 | stack.push({
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87 | init: !context.getScope().isStrict,
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88 | node,
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89 | valid: true
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90 | });
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91 | }
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92 |
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93 | /**
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94 | * Pops the current checking context from the stack.
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95 | * @returns {void}
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96 | */
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97 | function exitFunction() {
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98 | stack.pop();
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99 | }
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100 |
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101 | return {
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102 |
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103 | /*
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104 | * `this` is invalid only under strict mode.
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105 | * Modules is always strict mode.
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106 | */
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107 | Program(node) {
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108 | const scope = context.getScope(),
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109 | features = context.parserOptions.ecmaFeatures || {};
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110 |
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111 | stack.push({
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112 | init: true,
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113 | node,
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114 | valid: !(
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115 | scope.isStrict ||
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116 | node.sourceType === "module" ||
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117 | (features.globalReturn && scope.childScopes[0].isStrict)
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118 | )
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119 | });
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120 | },
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121 |
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122 | "Program:exit"() {
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123 | stack.pop();
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124 | },
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125 |
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126 | ClassProperty: enterClassProperty,
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127 | "ClassProperty:exit": exitClassProperty,
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128 | FunctionDeclaration: enterFunction,
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129 | "FunctionDeclaration:exit": exitFunction,
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130 | FunctionExpression: enterFunction,
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131 | "FunctionExpression:exit": exitFunction,
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132 |
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133 | // Reports if `this` of the current context is invalid.
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134 | ThisExpression(node) {
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135 | const current = stack.getCurrent();
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136 |
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137 | if (!insideClassProperty && current && !current.valid) {
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138 | context.report(node, "Unexpected 'this'.");
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139 | }
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140 | }
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141 | };
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142 | }
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143 | };
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