eslint/lib/rules/no-undef-init.js

   1 /**
   2  * @fileoverview Rule to flag when initializing to undefined
   3  * @author Ilya Volodin
   4  */
   5
   6 "use strict";
   7
   8 const astUtils = require("./utils/ast-utils");
   9
  10 //------------------------------------------------------------------------------
  11 // Rule Definition
  12 //------------------------------------------------------------------------------
  13
  14 /** @type {import('../shared/types').Rule} */
  15 module.exports = {
  16     meta: {
  17         type: "suggestion",
  18
  19         docs: {
  20             description: "disallow initializing variables to `undefined`",
  21             recommended: false,
  22             url: "https://eslint.org/docs/rules/no-undef-init"
  23         },
  24
  25         schema: [],
  26         fixable: "code",
  27
  28         messages: {
  29             unnecessaryUndefinedInit: "It's not necessary to initialize '{{name}}' to undefined."
  30         }
  31     },
  32
  33     create(context) {
  34
  35         const sourceCode = context.getSourceCode();
  36
  37         return {
  38
  39             VariableDeclarator(node) {
  40                 const name = sourceCode.getText(node.id),
  41                     init = node.init && node.init.name,
  42                     scope = context.getScope(),
  43                     undefinedVar = astUtils.getVariableByName(scope, "undefined"),
  44                     shadowed = undefinedVar && undefinedVar.defs.length > 0,
  45                     lastToken = sourceCode.getLastToken(node);
  46
  47                 if (init === "undefined" && node.parent.kind !== "const" && !shadowed) {
  48                     context.report({
  49                         node,
  50                         messageId: "unnecessaryUndefinedInit",
  51                         data: { name },
  52                         fix(fixer) {
  53                             if (node.parent.kind === "var") {
  54                                 return null;
  55                             }
  56
  57                             if (node.id.type === "ArrayPattern" || node.id.type === "ObjectPattern") {
  58
  59                                 // Don't fix destructuring assignment to `undefined`.
  60                                 return null;
  61                             }
  62
  63                             if (sourceCode.commentsExistBetween(node.id, lastToken)) {
  64                                 return null;
  65                             }
  66
  67                             return fixer.removeRange([node.id.range[1], node.range[1]]);
  68                         }
  69                     });
  70                 }
  71             }
  72         };
  73
  74     }
  75 };