1 | /**
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2 | * @fileoverview Restrict usage of duplicate imports.
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3 | * @author Simen Bekkhus
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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 | // Rule Definition
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9 | //------------------------------------------------------------------------------
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10 |
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11 | /**
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12 | * Returns the name of the module imported or re-exported.
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13 | * @param {ASTNode} node A node to get.
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14 | * @returns {string} the name of the module, or empty string if no name.
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15 | */
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16 | function getValue(node) {
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17 | if (node && node.source && node.source.value) {
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18 | return node.source.value.trim();
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19 | }
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20 |
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21 | return "";
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22 | }
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23 |
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24 | /**
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25 | * Checks if the name of the import or export exists in the given array, and reports if so.
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26 | * @param {RuleContext} context The ESLint rule context object.
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27 | * @param {ASTNode} node A node to get.
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28 | * @param {string} value The name of the imported or exported module.
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29 | * @param {string[]} array The array containing other imports or exports in the file.
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30 | * @param {string} messageId A messageId to be reported after the name of the module
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31 | *
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32 | * @returns {void} No return value
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33 | */
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34 | function checkAndReport(context, node, value, array, messageId) {
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35 | if (array.indexOf(value) !== -1) {
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36 | context.report({
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37 | node,
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38 | messageId,
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39 | data: {
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40 | module: value
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41 | }
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42 | });
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43 | }
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44 | }
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45 |
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46 | /**
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47 | * @callback nodeCallback
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48 | * @param {ASTNode} node A node to handle.
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49 | */
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50 |
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51 | /**
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52 | * Returns a function handling the imports of a given file
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53 | * @param {RuleContext} context The ESLint rule context object.
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54 | * @param {boolean} includeExports Whether or not to check for exports in addition to imports.
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55 | * @param {string[]} importsInFile The array containing other imports in the file.
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56 | * @param {string[]} exportsInFile The array containing other exports in the file.
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57 | *
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58 | * @returns {nodeCallback} A function passed to ESLint to handle the statement.
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59 | */
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60 | function handleImports(context, includeExports, importsInFile, exportsInFile) {
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61 | return function(node) {
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62 | const value = getValue(node);
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63 |
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64 | if (value) {
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65 | checkAndReport(context, node, value, importsInFile, "import");
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66 |
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67 | if (includeExports) {
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68 | checkAndReport(context, node, value, exportsInFile, "importAs");
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69 | }
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70 |
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71 | importsInFile.push(value);
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72 | }
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73 | };
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74 | }
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75 |
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76 | /**
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77 | * Returns a function handling the exports of a given file
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78 | * @param {RuleContext} context The ESLint rule context object.
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79 | * @param {string[]} importsInFile The array containing other imports in the file.
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80 | * @param {string[]} exportsInFile The array containing other exports in the file.
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81 | *
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82 | * @returns {nodeCallback} A function passed to ESLint to handle the statement.
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83 | */
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84 | function handleExports(context, importsInFile, exportsInFile) {
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85 | return function(node) {
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86 | const value = getValue(node);
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87 |
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88 | if (value) {
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89 | checkAndReport(context, node, value, exportsInFile, "export");
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90 | checkAndReport(context, node, value, importsInFile, "exportAs");
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91 |
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92 | exportsInFile.push(value);
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93 | }
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94 | };
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95 | }
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96 |
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97 | module.exports = {
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98 | meta: {
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99 | type: "problem",
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100 |
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101 | docs: {
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102 | description: "disallow duplicate module imports",
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103 | category: "ECMAScript 6",
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104 | recommended: false,
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105 | url: "https://eslint.org/docs/rules/no-duplicate-imports"
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106 | },
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107 |
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108 | schema: [{
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109 | type: "object",
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110 | properties: {
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111 | includeExports: {
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112 | type: "boolean",
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113 | default: false
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114 | }
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115 | },
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116 | additionalProperties: false
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117 | }],
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118 | messages: {
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119 | import: "'{{module}}' import is duplicated.",
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120 | importAs: "'{{module}}' import is duplicated as export.",
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121 | export: "'{{module}}' export is duplicated.",
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122 | exportAs: "'{{module}}' export is duplicated as import."
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123 | }
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124 | },
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125 |
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126 | create(context) {
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127 | const includeExports = (context.options[0] || {}).includeExports,
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128 | importsInFile = [],
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129 | exportsInFile = [];
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130 |
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131 | const handlers = {
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132 | ImportDeclaration: handleImports(context, includeExports, importsInFile, exportsInFile)
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133 | };
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134 |
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135 | if (includeExports) {
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136 | handlers.ExportNamedDeclaration = handleExports(context, importsInFile, exportsInFile);
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137 | handlers.ExportAllDeclaration = handleExports(context, importsInFile, exportsInFile);
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138 | }
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139 |
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140 | return handlers;
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141 | }
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142 | };
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