1 | /**
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2 | * @fileoverview Rule to warn when a function expression does not have a name.
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3 | * @author Kyle T. Nunery
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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("./utils/ast-utils");
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13 |
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14 | /**
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15 | * Checks whether or not a given variable is a function name.
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16 | * @param {eslint-scope.Variable} variable A variable to check.
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17 | * @returns {boolean} `true` if the variable is a function name.
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18 | */
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19 | function isFunctionName(variable) {
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20 | return variable && variable.defs[0].type === "FunctionName";
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21 | }
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22 |
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23 | //------------------------------------------------------------------------------
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24 | // Rule Definition
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25 | //------------------------------------------------------------------------------
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26 |
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27 | module.exports = {
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28 | meta: {
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29 | type: "suggestion",
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30 |
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31 | docs: {
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32 | description: "require or disallow named `function` expressions",
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33 | category: "Stylistic Issues",
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34 | recommended: false,
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35 | url: "https://eslint.org/docs/rules/func-names"
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36 | },
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37 |
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38 | schema: {
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39 | definitions: {
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40 | value: {
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41 | enum: [
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42 | "always",
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43 | "as-needed",
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44 | "never"
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45 | ]
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46 | }
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47 | },
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48 | items: [
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49 | {
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50 | $ref: "#/definitions/value"
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51 | },
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52 | {
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53 | type: "object",
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54 | properties: {
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55 | generators: {
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56 | $ref: "#/definitions/value"
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57 | }
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58 | },
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59 | additionalProperties: false
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60 | }
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61 | ]
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62 | },
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63 |
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64 | messages: {
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65 | unnamed: "Unexpected unnamed {{name}}.",
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66 | named: "Unexpected named {{name}}."
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67 | }
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68 | },
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69 |
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70 | create(context) {
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71 |
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72 | const sourceCode = context.getSourceCode();
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73 |
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74 | /**
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75 | * Returns the config option for the given node.
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76 | * @param {ASTNode} node A node to get the config for.
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77 | * @returns {string} The config option.
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78 | */
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79 | function getConfigForNode(node) {
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80 | if (
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81 | node.generator &&
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82 | context.options.length > 1 &&
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83 | context.options[1].generators
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84 | ) {
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85 | return context.options[1].generators;
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86 | }
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87 |
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88 | return context.options[0] || "always";
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89 | }
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90 |
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91 | /**
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92 | * Determines whether the current FunctionExpression node is a get, set, or
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93 | * shorthand method in an object literal or a class.
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94 | * @param {ASTNode} node A node to check.
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95 | * @returns {boolean} True if the node is a get, set, or shorthand method.
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96 | */
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97 | function isObjectOrClassMethod(node) {
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98 | const parent = node.parent;
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99 |
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100 | return (parent.type === "MethodDefinition" || (
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101 | parent.type === "Property" && (
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102 | parent.method ||
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103 | parent.kind === "get" ||
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104 | parent.kind === "set"
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105 | )
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106 | ));
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107 | }
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108 |
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109 | /**
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110 | * Determines whether the current FunctionExpression node has a name that would be
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111 | * inferred from context in a conforming ES6 environment.
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112 | * @param {ASTNode} node A node to check.
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113 | * @returns {boolean} True if the node would have a name assigned automatically.
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114 | */
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115 | function hasInferredName(node) {
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116 | const parent = node.parent;
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117 |
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118 | return isObjectOrClassMethod(node) ||
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119 | (parent.type === "VariableDeclarator" && parent.id.type === "Identifier" && parent.init === node) ||
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120 | (parent.type === "Property" && parent.value === node) ||
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121 | (parent.type === "AssignmentExpression" && parent.left.type === "Identifier" && parent.right === node) ||
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122 | (parent.type === "AssignmentPattern" && parent.left.type === "Identifier" && parent.right === node);
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123 | }
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124 |
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125 | /**
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126 | * Reports that an unnamed function should be named
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127 | * @param {ASTNode} node The node to report in the event of an error.
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128 | * @returns {void}
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129 | */
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130 | function reportUnexpectedUnnamedFunction(node) {
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131 | context.report({
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132 | node,
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133 | messageId: "unnamed",
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134 | loc: astUtils.getFunctionHeadLoc(node, sourceCode),
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135 | data: { name: astUtils.getFunctionNameWithKind(node) }
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136 | });
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137 | }
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138 |
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139 | /**
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140 | * Reports that a named function should be unnamed
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141 | * @param {ASTNode} node The node to report in the event of an error.
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142 | * @returns {void}
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143 | */
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144 | function reportUnexpectedNamedFunction(node) {
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145 | context.report({
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146 | node,
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147 | messageId: "named",
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148 | loc: astUtils.getFunctionHeadLoc(node, sourceCode),
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149 | data: { name: astUtils.getFunctionNameWithKind(node) }
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150 | });
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151 | }
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152 |
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153 | /**
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154 | * The listener for function nodes.
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155 | * @param {ASTNode} node function node
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156 | * @returns {void}
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157 | */
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158 | function handleFunction(node) {
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159 |
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160 | // Skip recursive functions.
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161 | const nameVar = context.getDeclaredVariables(node)[0];
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162 |
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163 | if (isFunctionName(nameVar) && nameVar.references.length > 0) {
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164 | return;
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165 | }
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166 |
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167 | const hasName = Boolean(node.id && node.id.name);
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168 | const config = getConfigForNode(node);
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169 |
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170 | if (config === "never") {
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171 | if (hasName && node.type !== "FunctionDeclaration") {
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172 | reportUnexpectedNamedFunction(node);
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173 | }
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174 | } else if (config === "as-needed") {
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175 | if (!hasName && !hasInferredName(node)) {
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176 | reportUnexpectedUnnamedFunction(node);
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177 | }
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178 | } else {
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179 | if (!hasName && !isObjectOrClassMethod(node)) {
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180 | reportUnexpectedUnnamedFunction(node);
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181 | }
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182 | }
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183 | }
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184 |
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185 | return {
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186 | "FunctionExpression:exit": handleFunction,
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187 | "ExportDefaultDeclaration > FunctionDeclaration": handleFunction
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188 | };
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189 | }
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190 | };
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