1 | /**
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2 | * @fileoverview Rule to define spacing before/after arrow function's arrow.
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3 | * @author Jxck
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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 and after the arrow in arrow functions",
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23 | category: "ECMAScript 6",
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24 | recommended: false,
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25 | url: "https://eslint.org/docs/rules/arrow-spacing"
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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 | type: "object",
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33 | properties: {
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34 | before: {
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35 | type: "boolean",
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36 | default: true
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37 | },
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38 | after: {
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39 | type: "boolean",
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40 | default: true
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41 | }
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42 | },
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43 | additionalProperties: false
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44 | }
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45 | ],
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46 |
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47 | messages: {
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48 | expectedBefore: "Missing space before =>.",
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49 | unexpectedBefore: "Unexpected space before =>.",
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50 |
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51 | expectedAfter: "Missing space after =>.",
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52 | unexpectedAfter: "Unexpected space after =>."
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53 | }
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54 | },
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55 |
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56 | create(context) {
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57 |
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58 | // merge rules with default
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59 | const rule = Object.assign({}, context.options[0]);
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60 |
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61 | rule.before = rule.before !== false;
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62 | rule.after = rule.after !== false;
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63 |
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64 | const sourceCode = context.getSourceCode();
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65 |
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66 | /**
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67 | * Get tokens of arrow(`=>`) and before/after arrow.
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68 | * @param {ASTNode} node The arrow function node.
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69 | * @returns {Object} Tokens of arrow and before/after arrow.
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70 | */
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71 | function getTokens(node) {
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72 | const arrow = sourceCode.getTokenBefore(node.body, astUtils.isArrowToken);
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73 |
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74 | return {
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75 | before: sourceCode.getTokenBefore(arrow),
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76 | arrow,
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77 | after: sourceCode.getTokenAfter(arrow)
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78 | };
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79 | }
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80 |
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81 | /**
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82 | * Count spaces before/after arrow(`=>`) token.
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83 | * @param {Object} tokens Tokens before/after arrow.
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84 | * @returns {Object} count of space before/after arrow.
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85 | */
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86 | function countSpaces(tokens) {
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87 | const before = tokens.arrow.range[0] - tokens.before.range[1];
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88 | const after = tokens.after.range[0] - tokens.arrow.range[1];
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89 |
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90 | return { before, after };
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91 | }
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92 |
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93 | /**
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94 | * Determines whether space(s) before after arrow(`=>`) is satisfy rule.
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95 | * if before/after value is `true`, there should be space(s).
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96 | * if before/after value is `false`, there should be no space.
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97 | * @param {ASTNode} node The arrow function node.
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98 | * @returns {void}
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99 | */
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100 | function spaces(node) {
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101 | const tokens = getTokens(node);
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102 | const countSpace = countSpaces(tokens);
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103 |
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104 | if (rule.before) {
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105 |
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106 | // should be space(s) before arrow
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107 | if (countSpace.before === 0) {
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108 | context.report({
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109 | node: tokens.before,
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110 | messageId: "expectedBefore",
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111 | fix(fixer) {
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112 | return fixer.insertTextBefore(tokens.arrow, " ");
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113 | }
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114 | });
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115 | }
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116 | } else {
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117 |
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118 | // should be no space before arrow
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119 | if (countSpace.before > 0) {
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120 | context.report({
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121 | node: tokens.before,
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122 | messageId: "unexpectedBefore",
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123 | fix(fixer) {
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124 | return fixer.removeRange([tokens.before.range[1], tokens.arrow.range[0]]);
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125 | }
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126 | });
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127 | }
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128 | }
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129 |
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130 | if (rule.after) {
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131 |
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132 | // should be space(s) after arrow
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133 | if (countSpace.after === 0) {
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134 | context.report({
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135 | node: tokens.after,
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136 | messageId: "expectedAfter",
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137 | fix(fixer) {
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138 | return fixer.insertTextAfter(tokens.arrow, " ");
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139 | }
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140 | });
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141 | }
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142 | } else {
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143 |
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144 | // should be no space after arrow
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145 | if (countSpace.after > 0) {
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146 | context.report({
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147 | node: tokens.after,
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148 | messageId: "unexpectedAfter",
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149 | fix(fixer) {
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150 | return fixer.removeRange([tokens.arrow.range[1], tokens.after.range[0]]);
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151 | }
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152 | });
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153 | }
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154 | }
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155 | }
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156 |
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157 | return {
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158 | ArrowFunctionExpression: spaces
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159 | };
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160 | }
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161 | };
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