1 | /**
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2 | * @fileoverview Rule to validate spacing before function paren.
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3 | * @author Mathias Schreck <https://github.com/lo1tuma>
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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 | // Requirements
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9 | //------------------------------------------------------------------------------
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10 |
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11 | const astUtils = require("./utils/ast-utils");
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12 |
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13 | //------------------------------------------------------------------------------
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14 | // Rule Definition
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15 | //------------------------------------------------------------------------------
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16 |
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17 | module.exports = {
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18 | meta: {
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19 | type: "layout",
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20 |
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21 | docs: {
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22 | description: "enforce consistent spacing before `function` definition opening parenthesis",
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23 | category: "Stylistic Issues",
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24 | recommended: false,
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25 | url: "https://eslint.org/docs/rules/space-before-function-paren"
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26 | },
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27 |
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28 | fixable: "whitespace",
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29 |
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30 | schema: [
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31 | {
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32 | oneOf: [
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33 | {
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34 | enum: ["always", "never"]
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35 | },
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36 | {
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37 | type: "object",
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38 | properties: {
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39 | anonymous: {
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40 | enum: ["always", "never", "ignore"]
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41 | },
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42 | named: {
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43 | enum: ["always", "never", "ignore"]
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44 | },
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45 | asyncArrow: {
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46 | enum: ["always", "never", "ignore"]
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47 | }
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48 | },
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49 | additionalProperties: false
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50 | }
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51 | ]
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52 | }
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53 | ],
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54 |
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55 | messages: {
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56 | unexpectedSpace: "Unexpected space before function parentheses.",
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57 | missingSpace: "Missing space before function parentheses."
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58 | }
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59 | },
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60 |
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61 | create(context) {
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62 | const sourceCode = context.getSourceCode();
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63 | const baseConfig = typeof context.options[0] === "string" ? context.options[0] : "always";
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64 | const overrideConfig = typeof context.options[0] === "object" ? context.options[0] : {};
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65 |
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66 | /**
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67 | * Determines whether a function has a name.
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68 | * @param {ASTNode} node The function node.
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69 | * @returns {boolean} Whether the function has a name.
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70 | */
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71 | function isNamedFunction(node) {
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72 | if (node.id) {
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73 | return true;
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74 | }
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75 |
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76 | const parent = node.parent;
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77 |
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78 | return parent.type === "MethodDefinition" ||
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79 | (parent.type === "Property" &&
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80 | (
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81 | parent.kind === "get" ||
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82 | parent.kind === "set" ||
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83 | parent.method
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84 | )
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85 | );
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86 | }
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87 |
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88 | /**
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89 | * Gets the config for a given function
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90 | * @param {ASTNode} node The function node
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91 | * @returns {string} "always", "never", or "ignore"
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92 | */
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93 | function getConfigForFunction(node) {
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94 | if (node.type === "ArrowFunctionExpression") {
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95 |
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96 | // Always ignore non-async functions and arrow functions without parens, e.g. async foo => bar
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97 | if (node.async && astUtils.isOpeningParenToken(sourceCode.getFirstToken(node, { skip: 1 }))) {
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98 | return overrideConfig.asyncArrow || baseConfig;
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99 | }
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100 | } else if (isNamedFunction(node)) {
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101 | return overrideConfig.named || baseConfig;
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102 |
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103 | // `generator-star-spacing` should warn anonymous generators. E.g. `function* () {}`
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104 | } else if (!node.generator) {
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105 | return overrideConfig.anonymous || baseConfig;
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106 | }
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107 |
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108 | return "ignore";
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109 | }
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110 |
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111 | /**
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112 | * Checks the parens of a function node
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113 | * @param {ASTNode} node A function node
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114 | * @returns {void}
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115 | */
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116 | function checkFunction(node) {
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117 | const functionConfig = getConfigForFunction(node);
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118 |
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119 | if (functionConfig === "ignore") {
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120 | return;
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121 | }
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122 |
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123 | const rightToken = sourceCode.getFirstToken(node, astUtils.isOpeningParenToken);
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124 | const leftToken = sourceCode.getTokenBefore(rightToken);
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125 | const hasSpacing = sourceCode.isSpaceBetweenTokens(leftToken, rightToken);
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126 |
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127 | if (hasSpacing && functionConfig === "never") {
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128 | context.report({
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129 | node,
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130 | loc: {
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131 | start: leftToken.loc.end,
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132 | end: rightToken.loc.start
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133 | },
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134 | messageId: "unexpectedSpace",
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135 | fix(fixer) {
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136 | const comments = sourceCode.getCommentsBefore(rightToken);
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137 |
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138 | // Don't fix anything if there's a single line comment between the left and the right token
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139 | if (comments.some(comment => comment.type === "Line")) {
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140 | return null;
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141 | }
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142 | return fixer.replaceTextRange(
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143 | [leftToken.range[1], rightToken.range[0]],
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144 | comments.reduce((text, comment) => text + sourceCode.getText(comment), "")
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145 | );
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146 | }
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147 | });
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148 | } else if (!hasSpacing && functionConfig === "always") {
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149 | context.report({
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150 | node,
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151 | loc: rightToken.loc,
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152 | messageId: "missingSpace",
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153 | fix: fixer => fixer.insertTextAfter(leftToken, " ")
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154 | });
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155 | }
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156 | }
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157 |
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158 | return {
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159 | ArrowFunctionExpression: checkFunction,
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160 | FunctionDeclaration: checkFunction,
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161 | FunctionExpression: checkFunction
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162 | };
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163 | }
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164 | };
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