1 | /**
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2 | * @fileoverview Rule to flag statements that use magic numbers (adapted from https://github.com/danielstjules/buddy.js)
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3 | * @author Vincent Lemeunier
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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 | // Rule Definition
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10 | //------------------------------------------------------------------------------
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11 |
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12 | module.exports = {
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13 | meta: {
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14 | docs: {
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15 | description: "disallow magic numbers",
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16 | category: "Best Practices",
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17 | recommended: false,
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18 | url: "https://eslint.org/docs/rules/no-magic-numbers"
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19 | },
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20 |
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21 | schema: [{
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22 | type: "object",
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23 | properties: {
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24 | detectObjects: {
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25 | type: "boolean"
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26 | },
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27 | enforceConst: {
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28 | type: "boolean"
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29 | },
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30 | ignore: {
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31 | type: "array",
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32 | items: {
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33 | type: "number"
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34 | },
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35 | uniqueItems: true
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36 | },
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37 | ignoreArrayIndexes: {
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38 | type: "boolean"
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39 | }
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40 | },
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41 | additionalProperties: false
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42 | }]
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43 | },
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44 |
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45 | create(context) {
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46 | const config = context.options[0] || {},
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47 | detectObjects = !!config.detectObjects,
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48 | enforceConst = !!config.enforceConst,
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49 | ignore = config.ignore || [],
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50 | ignoreArrayIndexes = !!config.ignoreArrayIndexes;
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51 |
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52 | /**
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53 | * Returns whether the node is number literal
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54 | * @param {Node} node - the node literal being evaluated
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55 | * @returns {boolean} true if the node is a number literal
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56 | */
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57 | function isNumber(node) {
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58 | return typeof node.value === "number";
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59 | }
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60 |
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61 | /**
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62 | * Returns whether the number should be ignored
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63 | * @param {number} num - the number
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64 | * @returns {boolean} true if the number should be ignored
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65 | */
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66 | function shouldIgnoreNumber(num) {
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67 | return ignore.indexOf(num) !== -1;
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68 | }
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69 |
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70 | /**
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71 | * Returns whether the number should be ignored when used as a radix within parseInt() or Number.parseInt()
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72 | * @param {ASTNode} parent - the non-"UnaryExpression" parent
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73 | * @param {ASTNode} node - the node literal being evaluated
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74 | * @returns {boolean} true if the number should be ignored
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75 | */
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76 | function shouldIgnoreParseInt(parent, node) {
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77 | return parent.type === "CallExpression" && node === parent.arguments[1] &&
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78 | (parent.callee.name === "parseInt" ||
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79 | parent.callee.type === "MemberExpression" &&
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80 | parent.callee.object.name === "Number" &&
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81 | parent.callee.property.name === "parseInt");
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82 | }
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83 |
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84 | /**
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85 | * Returns whether the number should be ignored when used to define a JSX prop
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86 | * @param {ASTNode} parent - the non-"UnaryExpression" parent
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87 | * @returns {boolean} true if the number should be ignored
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88 | */
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89 | function shouldIgnoreJSXNumbers(parent) {
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90 | return parent.type.indexOf("JSX") === 0;
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91 | }
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92 |
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93 | /**
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94 | * Returns whether the number should be ignored when used as an array index with enabled 'ignoreArrayIndexes' option.
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95 | * @param {ASTNode} parent - the non-"UnaryExpression" parent.
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96 | * @returns {boolean} true if the number should be ignored
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97 | */
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98 | function shouldIgnoreArrayIndexes(parent) {
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99 | return parent.type === "MemberExpression" && ignoreArrayIndexes;
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100 | }
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101 |
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102 | return {
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103 | Literal(node) {
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104 | let parent = node.parent,
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105 | value = node.value,
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106 | raw = node.raw;
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107 | const okTypes = detectObjects ? [] : ["ObjectExpression", "Property", "AssignmentExpression"];
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108 |
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109 | if (!isNumber(node)) {
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110 | return;
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111 | }
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112 |
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113 | // For negative magic numbers: update the value and parent node
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114 | if (parent.type === "UnaryExpression" && parent.operator === "-") {
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115 | node = parent;
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116 | parent = node.parent;
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117 | value = -value;
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118 | raw = `-${raw}`;
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119 | }
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120 |
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121 | if (shouldIgnoreNumber(value) ||
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122 | shouldIgnoreParseInt(parent, node) ||
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123 | shouldIgnoreArrayIndexes(parent) ||
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124 | shouldIgnoreJSXNumbers(parent)) {
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125 | return;
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126 | }
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127 |
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128 | if (parent.type === "VariableDeclarator") {
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129 | if (enforceConst && parent.parent.kind !== "const") {
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130 | context.report({
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131 | node,
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132 | message: "Number constants declarations must use 'const'."
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133 | });
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134 | }
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135 | } else if (
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136 | okTypes.indexOf(parent.type) === -1 ||
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137 | (parent.type === "AssignmentExpression" && parent.left.type === "Identifier")
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138 | ) {
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139 | context.report({
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140 | node,
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141 | message: "No magic number: {{raw}}.",
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142 | data: {
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143 | raw
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144 | }
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145 | });
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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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