eslint/lib/rules/no-undef.js

   1 /**
   2  * @fileoverview Rule to flag references to undeclared variables.
   3  * @author Mark Macdonald
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Helpers
   9 //------------------------------------------------------------------------------
  10
  11 /**
  12  * Checks if the given node is the argument of a typeof operator.
  13  * @param {ASTNode} node The AST node being checked.
  14  * @returns {boolean} Whether or not the node is the argument of a typeof operator.
  15  */
  16 function hasTypeOfOperator(node) {
  17     const parent = node.parent;
  18
  19     return parent.type === "UnaryExpression" && parent.operator === "typeof";
  20 }
  21
  22 //------------------------------------------------------------------------------
  23 // Rule Definition
  24 //------------------------------------------------------------------------------
  25
  26 /** @type {import('../shared/types').Rule} */
  27 module.exports = {
  28     meta: {
  29         type: "problem",
  30
  31         docs: {
  32             description: "Disallow the use of undeclared variables unless mentioned in `/*global */` comments",
  33             recommended: true,
  34             url: "https://eslint.org/docs/rules/no-undef"
  35         },
  36
  37         schema: [
  38             {
  39                 type: "object",
  40                 properties: {
  41                     typeof: {
  42                         type: "boolean",
  43                         default: false
  44                     }
  45                 },
  46                 additionalProperties: false
  47             }
  48         ],
  49         messages: {
  50             undef: "'{{name}}' is not defined."
  51         }
  52     },
  53
  54     create(context) {
  55         const options = context.options[0];
  56         const considerTypeOf = options && options.typeof === true || false;
  57
  58         return {
  59             "Program:exit"(/* node */) {
  60                 const globalScope = context.getScope();
  61
  62                 globalScope.through.forEach(ref => {
  63                     const identifier = ref.identifier;
  64
  65                     if (!considerTypeOf && hasTypeOfOperator(identifier)) {
  66                         return;
  67                     }
  68
  69                     context.report({
  70                         node: identifier,
  71                         messageId: "undef",
  72                         data: identifier
  73                     });
  74                 });
  75             }
  76         };
  77     }
  78 };