eslint/lib/rules/no-useless-computed-key.js

   1 /**
   2  * @fileoverview Rule to disallow unnecessary computed property keys in object literals
   3  * @author Burak Yigit Kaya
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Requirements
   9 //------------------------------------------------------------------------------
  10
  11 const astUtils = require("./utils/ast-utils");
  12
  13 //------------------------------------------------------------------------------
  14 // Rule Definition
  15 //------------------------------------------------------------------------------
  16
  17 module.exports = {
  18     meta: {
  19         type: "suggestion",
  20
  21         docs: {
  22             description: "disallow unnecessary computed property keys in objects and classes",
  23             category: "ECMAScript 6",
  24             recommended: false,
  25             url: "https://eslint.org/docs/rules/no-useless-computed-key"
  26         },
  27
  28         schema: [{
  29             type: "object",
  30             properties: {
  31                 enforceForClassMembers: {
  32                     type: "boolean",
  33                     default: false
  34                 }
  35             },
  36             additionalProperties: false
  37         }],
  38         fixable: "code",
  39
  40         messages: {
  41             unnecessarilyComputedProperty: "Unnecessarily computed property [{{property}}] found."
  42         }
  43     },
  44     create(context) {
  45         const sourceCode = context.getSourceCode();
  46         const enforceForClassMembers = context.options[0] && context.options[0].enforceForClassMembers;
  47
  48         /**
  49          * Reports a given node if it violated this rule.
  50          * @param {ASTNode} node The node to check.
  51          * @returns {void}
  52          */
  53         function check(node) {
  54             if (!node.computed) {
  55                 return;
  56             }
  57
  58             const key = node.key,
  59                 nodeType = typeof key.value;
  60
  61             let allowedKey;
  62
  63             if (node.type === "MethodDefinition") {
  64                 allowedKey = node.static ? "prototype" : "constructor";
  65             } else {
  66                 allowedKey = "__proto__";
  67             }
  68
  69             if (key.type === "Literal" && (nodeType === "string" || nodeType === "number") && key.value !== allowedKey) {
  70                 context.report({
  71                     node,
  72                     messageId: "unnecessarilyComputedProperty",
  73                     data: { property: sourceCode.getText(key) },
  74                     fix(fixer) {
  75                         const leftSquareBracket = sourceCode.getTokenBefore(key, astUtils.isOpeningBracketToken);
  76                         const rightSquareBracket = sourceCode.getTokenAfter(key, astUtils.isClosingBracketToken);
  77
  78                         // If there are comments between the brackets and the property name, don't do a fix.
  79                         if (sourceCode.commentsExistBetween(leftSquareBracket, rightSquareBracket)) {
  80                             return null;
  81                         }
  82
  83                         const tokenBeforeLeftBracket = sourceCode.getTokenBefore(leftSquareBracket);
  84
  85                         // Insert a space before the key to avoid changing identifiers, e.g. ({ get[2]() {} }) to ({ get2() {} })
  86                         const needsSpaceBeforeKey = tokenBeforeLeftBracket.range[1] === leftSquareBracket.range[0] &&
  87                             !astUtils.canTokensBeAdjacent(tokenBeforeLeftBracket, sourceCode.getFirstToken(key));
  88
  89                         const replacementKey = (needsSpaceBeforeKey ? " " : "") + key.raw;
  90
  91                         return fixer.replaceTextRange([leftSquareBracket.range[0], rightSquareBracket.range[1]], replacementKey);
  92                     }
  93                 });
  94             }
  95         }
  96
  97         /**
  98          * A no-op function to act as placeholder for checking a node when the `enforceForClassMembers` option is `false`.
  99          * @returns {void}
 100          * @private
 101          */
 102         function noop() {}
 103
 104         return {
 105             Property: check,
 106             MethodDefinition: enforceForClassMembers ? check : noop
 107         };
 108     }
 109 };