1 | /**
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2 | * @fileoverview Rule to enforce consistent naming of "this" context variables
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3 | * @author Raphael Pigulla
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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 | // Rule Definition
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9 | //------------------------------------------------------------------------------
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10 |
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11 | module.exports = {
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12 | meta: {
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13 | type: "suggestion",
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14 |
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15 | docs: {
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16 | description: "enforce consistent naming when capturing the current execution context",
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17 | category: "Stylistic Issues",
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18 | recommended: false,
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19 | url: "https://eslint.org/docs/rules/consistent-this"
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20 | },
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21 |
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22 | schema: {
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23 | type: "array",
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24 | items: {
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25 | type: "string",
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26 | minLength: 1
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27 | },
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28 | uniqueItems: true
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29 | },
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30 |
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31 | messages: {
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32 | aliasNotAssignedToThis: "Designated alias '{{name}}' is not assigned to 'this'.",
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33 | unexpectedAlias: "Unexpected alias '{{name}}' for 'this'."
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34 | }
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35 | },
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36 |
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37 | create(context) {
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38 | let aliases = [];
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39 |
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40 | if (context.options.length === 0) {
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41 | aliases.push("that");
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42 | } else {
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43 | aliases = context.options;
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44 | }
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45 |
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46 | /**
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47 | * Reports that a variable declarator or assignment expression is assigning
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48 | * a non-'this' value to the specified alias.
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49 | * @param {ASTNode} node The assigning node.
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50 | * @param {string} name the name of the alias that was incorrectly used.
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51 | * @returns {void}
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52 | */
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53 | function reportBadAssignment(node, name) {
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54 | context.report({ node, messageId: "aliasNotAssignedToThis", data: { name } });
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55 | }
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56 |
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57 | /**
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58 | * Checks that an assignment to an identifier only assigns 'this' to the
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59 | * appropriate alias, and the alias is only assigned to 'this'.
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60 | * @param {ASTNode} node The assigning node.
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61 | * @param {Identifier} name The name of the variable assigned to.
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62 | * @param {Expression} value The value of the assignment.
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63 | * @returns {void}
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64 | */
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65 | function checkAssignment(node, name, value) {
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66 | const isThis = value.type === "ThisExpression";
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67 |
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68 | if (aliases.indexOf(name) !== -1) {
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69 | if (!isThis || node.operator && node.operator !== "=") {
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70 | reportBadAssignment(node, name);
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71 | }
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72 | } else if (isThis) {
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73 | context.report({ node, messageId: "unexpectedAlias", data: { name } });
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74 | }
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75 | }
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76 |
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77 | /**
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78 | * Ensures that a variable declaration of the alias in a program or function
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79 | * is assigned to the correct value.
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80 | * @param {string} alias alias the check the assignment of.
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81 | * @param {Object} scope scope of the current code we are checking.
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82 | * @private
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83 | * @returns {void}
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84 | */
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85 | function checkWasAssigned(alias, scope) {
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86 | const variable = scope.set.get(alias);
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87 |
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88 | if (!variable) {
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89 | return;
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90 | }
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91 |
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92 | if (variable.defs.some(def => def.node.type === "VariableDeclarator" &&
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93 | def.node.init !== null)) {
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94 | return;
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95 | }
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96 |
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97 | /*
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98 | * The alias has been declared and not assigned: check it was
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99 | * assigned later in the same scope.
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100 | */
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101 | if (!variable.references.some(reference => {
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102 | const write = reference.writeExpr;
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103 |
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104 | return (
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105 | reference.from === scope &&
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106 | write && write.type === "ThisExpression" &&
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107 | write.parent.operator === "="
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108 | );
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109 | })) {
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110 | variable.defs.map(def => def.node).forEach(node => {
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111 | reportBadAssignment(node, alias);
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112 | });
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113 | }
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114 | }
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115 |
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116 | /**
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117 | * Check each alias to ensure that is was assigned to the correct value.
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118 | * @returns {void}
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119 | */
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120 | function ensureWasAssigned() {
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121 | const scope = context.getScope();
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122 |
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123 | aliases.forEach(alias => {
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124 | checkWasAssigned(alias, scope);
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125 | });
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126 | }
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127 |
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128 | return {
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129 | "Program:exit": ensureWasAssigned,
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130 | "FunctionExpression:exit": ensureWasAssigned,
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131 | "FunctionDeclaration:exit": ensureWasAssigned,
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132 |
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133 | VariableDeclarator(node) {
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134 | const id = node.id;
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135 | const isDestructuring =
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136 | id.type === "ArrayPattern" || id.type === "ObjectPattern";
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137 |
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138 | if (node.init !== null && !isDestructuring) {
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139 | checkAssignment(node, id.name, node.init);
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140 | }
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141 | },
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142 |
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143 | AssignmentExpression(node) {
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144 | if (node.left.type === "Identifier") {
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145 | checkAssignment(node, node.left.name, node.right);
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146 | }
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147 | }
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148 | };
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149 |
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150 | }
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151 | };
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