1 | /**
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2 | * @fileoverview Rule to disallow empty functions.
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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("./utils/ast-utils");
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13 |
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14 | //------------------------------------------------------------------------------
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15 | // Helpers
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16 | //------------------------------------------------------------------------------
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17 |
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18 | const ALLOW_OPTIONS = Object.freeze([
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19 | "functions",
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20 | "arrowFunctions",
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21 | "generatorFunctions",
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22 | "methods",
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23 | "generatorMethods",
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24 | "getters",
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25 | "setters",
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26 | "constructors",
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27 | "asyncFunctions",
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28 | "asyncMethods"
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29 | ]);
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30 |
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31 | /**
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32 | * Gets the kind of a given function node.
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33 | * @param {ASTNode} node A function node to get. This is one of
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34 | * an ArrowFunctionExpression, a FunctionDeclaration, or a
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35 | * FunctionExpression.
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36 | * @returns {string} The kind of the function. This is one of "functions",
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37 | * "arrowFunctions", "generatorFunctions", "asyncFunctions", "methods",
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38 | * "generatorMethods", "asyncMethods", "getters", "setters", and
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39 | * "constructors".
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40 | */
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41 | function getKind(node) {
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42 | const parent = node.parent;
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43 | let kind = "";
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44 |
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45 | if (node.type === "ArrowFunctionExpression") {
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46 | return "arrowFunctions";
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47 | }
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48 |
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49 | // Detects main kind.
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50 | if (parent.type === "Property") {
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51 | if (parent.kind === "get") {
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52 | return "getters";
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53 | }
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54 | if (parent.kind === "set") {
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55 | return "setters";
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56 | }
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57 | kind = parent.method ? "methods" : "functions";
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58 |
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59 | } else if (parent.type === "MethodDefinition") {
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60 | if (parent.kind === "get") {
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61 | return "getters";
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62 | }
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63 | if (parent.kind === "set") {
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64 | return "setters";
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65 | }
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66 | if (parent.kind === "constructor") {
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67 | return "constructors";
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68 | }
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69 | kind = "methods";
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70 |
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71 | } else {
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72 | kind = "functions";
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73 | }
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74 |
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75 | // Detects prefix.
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76 | let prefix = "";
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77 |
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78 | if (node.generator) {
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79 | prefix = "generator";
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80 | } else if (node.async) {
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81 | prefix = "async";
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82 | } else {
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83 | return kind;
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84 | }
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85 | return prefix + kind[0].toUpperCase() + kind.slice(1);
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86 | }
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87 |
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88 | //------------------------------------------------------------------------------
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89 | // Rule Definition
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90 | //------------------------------------------------------------------------------
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91 |
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92 | module.exports = {
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93 | meta: {
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94 | type: "suggestion",
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95 |
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96 | docs: {
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97 | description: "disallow empty functions",
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98 | category: "Best Practices",
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99 | recommended: false,
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100 | url: "https://eslint.org/docs/rules/no-empty-function"
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101 | },
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102 |
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103 | schema: [
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104 | {
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105 | type: "object",
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106 | properties: {
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107 | allow: {
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108 | type: "array",
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109 | items: { enum: ALLOW_OPTIONS },
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110 | uniqueItems: true
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111 | }
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112 | },
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113 | additionalProperties: false
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114 | }
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115 | ],
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116 |
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117 | messages: {
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118 | unexpected: "Unexpected empty {{name}}."
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119 | }
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120 | },
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121 |
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122 | create(context) {
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123 | const options = context.options[0] || {};
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124 | const allowed = options.allow || [];
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125 |
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126 | const sourceCode = context.getSourceCode();
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127 |
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128 | /**
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129 | * Reports a given function node if the node matches the following patterns.
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130 | *
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131 | * - Not allowed by options.
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132 | * - The body is empty.
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133 | * - The body doesn't have any comments.
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134 | * @param {ASTNode} node A function node to report. This is one of
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135 | * an ArrowFunctionExpression, a FunctionDeclaration, or a
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136 | * FunctionExpression.
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137 | * @returns {void}
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138 | */
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139 | function reportIfEmpty(node) {
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140 | const kind = getKind(node);
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141 | const name = astUtils.getFunctionNameWithKind(node);
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142 | const innerComments = sourceCode.getTokens(node.body, {
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143 | includeComments: true,
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144 | filter: astUtils.isCommentToken
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145 | });
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146 |
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147 | if (allowed.indexOf(kind) === -1 &&
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148 | node.body.type === "BlockStatement" &&
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149 | node.body.body.length === 0 &&
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150 | innerComments.length === 0
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151 | ) {
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152 | context.report({
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153 | node,
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154 | loc: node.body.loc,
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155 | messageId: "unexpected",
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156 | data: { name }
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157 | });
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158 | }
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159 | }
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160 |
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161 | return {
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162 | ArrowFunctionExpression: reportIfEmpty,
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163 | FunctionDeclaration: reportIfEmpty,
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164 | FunctionExpression: reportIfEmpty
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165 | };
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166 | }
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167 | };
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