no-useless-rename.js

   1 /**
   2  * @fileoverview Disallow renaming import, export, and destructured assignments to the same name.
   3  * @author Kai Cataldo
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Rule Definition
  10 //------------------------------------------------------------------------------
  11
  12 module.exports = {
  13     meta: {
  14         type: "suggestion",
  15
  16         docs: {
  17             description: "disallow renaming import, export, and destructured assignments to the same name",
  18             category: "ECMAScript 6",
  19             recommended: false,
  20             url: "https://eslint.org/docs/rules/no-useless-rename"
  21         },
  22
  23         fixable: "code",
  24
  25         schema: [
  26             {
  27                 type: "object",
  28                 properties: {
  29                     ignoreDestructuring: { type: "boolean", default: false },
  30                     ignoreImport: { type: "boolean", default: false },
  31                     ignoreExport: { type: "boolean", default: false }
  32                 },
  33                 additionalProperties: false
  34             }
  35         ]
  36     },
  37
  38     create(context) {
  39         const sourceCode = context.getSourceCode(),
  40             options = context.options[0] || {},
  41             ignoreDestructuring = options.ignoreDestructuring === true,
  42             ignoreImport = options.ignoreImport === true,
  43             ignoreExport = options.ignoreExport === true;
  44
  45         //--------------------------------------------------------------------------
  46         // Helpers
  47         //--------------------------------------------------------------------------
  48
  49         /**
  50          * Reports error for unnecessarily renamed assignments
  51          * @param {ASTNode} node node to report
  52          * @param {ASTNode} initial node with initial name value
  53          * @param {ASTNode} result node with new name value
  54          * @param {string} type the type of the offending node
  55          * @returns {void}
  56          */
  57         function reportError(node, initial, result, type) {
  58             const name = initial.type === "Identifier" ? initial.name : initial.value;
  59
  60             return context.report({
  61                 node,
  62                 message: "{{type}} {{name}} unnecessarily renamed.",
  63                 data: {
  64                     name,
  65                     type
  66                 },
  67                 fix(fixer) {
  68                     if (sourceCode.commentsExistBetween(initial, result)) {
  69                         return null;
  70                     }
  71
  72                     const replacementText = result.type === "AssignmentPattern"
  73                         ? sourceCode.getText(result)
  74                         : name;
  75
  76                     return fixer.replaceTextRange([
  77                         initial.range[0],
  78                         result.range[1]
  79                     ], replacementText);
  80                 }
  81             });
  82         }
  83
  84         /**
  85          * Checks whether a destructured assignment is unnecessarily renamed
  86          * @param {ASTNode} node node to check
  87          * @returns {void}
  88          */
  89         function checkDestructured(node) {
  90             if (ignoreDestructuring) {
  91                 return;
  92             }
  93
  94             for (const property of node.properties) {
  95
  96                 /*
  97                  * TODO: Remove after babel-eslint removes ExperimentalRestProperty
  98                  * https://github.com/eslint/eslint/issues/12335
  99                  */
 100                 if (property.type === "ExperimentalRestProperty") {
 101                     continue;
 102                 }
 103
 104                 /**
 105                  * Properties using shorthand syntax and rest elements can not be renamed.
 106                  * If the property is computed, we have no idea if a rename is useless or not.
 107                  */
 108                 if (property.shorthand || property.type === "RestElement" || property.computed) {
 109                     continue;
 110                 }
 111
 112                 const key = (property.key.type === "Identifier" && property.key.name) || (property.key.type === "Literal" && property.key.value);
 113                 const renamedKey = property.value.type === "AssignmentPattern" ? property.value.left.name : property.value.name;
 114
 115                 if (key === renamedKey) {
 116                     reportError(property, property.key, property.value, "Destructuring assignment");
 117                 }
 118             }
 119         }
 120
 121         /**
 122          * Checks whether an import is unnecessarily renamed
 123          * @param {ASTNode} node node to check
 124          * @returns {void}
 125          */
 126         function checkImport(node) {
 127             if (ignoreImport) {
 128                 return;
 129             }
 130
 131             if (node.imported.name === node.local.name &&
 132                     node.imported.range[0] !== node.local.range[0]) {
 133                 reportError(node, node.imported, node.local, "Import");
 134             }
 135         }
 136
 137         /**
 138          * Checks whether an export is unnecessarily renamed
 139          * @param {ASTNode} node node to check
 140          * @returns {void}
 141          */
 142         function checkExport(node) {
 143             if (ignoreExport) {
 144                 return;
 145             }
 146
 147             if (node.local.name === node.exported.name &&
 148                     node.local.range[0] !== node.exported.range[0]) {
 149                 reportError(node, node.local, node.exported, "Export");
 150             }
 151
 152         }
 153
 154         //--------------------------------------------------------------------------
 155         // Public
 156         //--------------------------------------------------------------------------
 157
 158         return {
 159             ObjectPattern: checkDestructured,
 160             ImportSpecifier: checkImport,
 161             ExportSpecifier: checkExport
 162         };
 163     }
 164 };