eslint/lib/rules/no-undefined.js

   1 /**
   2  * @fileoverview Rule to flag references to the undefined variable.
   3  * @author Michael Ficarra
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Rule Definition
   9 //------------------------------------------------------------------------------
  10
  11 module.exports = {
  12     meta: {
  13         type: "suggestion",
  14
  15         docs: {
  16             description: "disallow the use of `undefined` as an identifier",
  17             recommended: false,
  18             url: "https://eslint.org/docs/rules/no-undefined"
  19         },
  20
  21         schema: [],
  22
  23         messages: {
  24             unexpectedUndefined: "Unexpected use of undefined."
  25         }
  26     },
  27
  28     create(context) {
  29
  30         /**
  31          * Report an invalid "undefined" identifier node.
  32          * @param {ASTNode} node The node to report.
  33          * @returns {void}
  34          */
  35         function report(node) {
  36             context.report({
  37                 node,
  38                 messageId: "unexpectedUndefined"
  39             });
  40         }
  41
  42         /**
  43          * Checks the given scope for references to `undefined` and reports
  44          * all references found.
  45          * @param {eslint-scope.Scope} scope The scope to check.
  46          * @returns {void}
  47          */
  48         function checkScope(scope) {
  49             const undefinedVar = scope.set.get("undefined");
  50
  51             if (!undefinedVar) {
  52                 return;
  53             }
  54
  55             const references = undefinedVar.references;
  56
  57             const defs = undefinedVar.defs;
  58
  59             // Report non-initializing references (those are covered in defs below)
  60             references
  61                 .filter(ref => !ref.init)
  62                 .forEach(ref => report(ref.identifier));
  63
  64             defs.forEach(def => report(def.name));
  65         }
  66
  67         return {
  68             "Program:exit"() {
  69                 const globalScope = context.getScope();
  70
  71                 const stack = [globalScope];
  72
  73                 while (stack.length) {
  74                     const scope = stack.pop();
  75
  76                     stack.push(...scope.childScopes);
  77                     checkScope(scope);
  78                 }
  79             }
  80         };
  81
  82     }
  83 };