eslint/lib/rules/no-global-assign.js

   1 /**
   2  * @fileoverview Rule to disallow assignments to native objects or read-only global variables
   3  * @author Ilya Volodin
   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 assignments to native objects or read-only global variables",
  18             recommended: true,
  19             url: "https://eslint.org/docs/rules/no-global-assign"
  20         },
  21
  22         schema: [
  23             {
  24                 type: "object",
  25                 properties: {
  26                     exceptions: {
  27                         type: "array",
  28                         items: { type: "string" },
  29                         uniqueItems: true
  30                     }
  31                 },
  32                 additionalProperties: false
  33             }
  34         ],
  35
  36         messages: {
  37             globalShouldNotBeModified: "Read-only global '{{name}}' should not be modified."
  38         }
  39     },
  40
  41     create(context) {
  42         const config = context.options[0];
  43         const exceptions = (config && config.exceptions) || [];
  44
  45         /**
  46          * Reports write references.
  47          * @param {Reference} reference A reference to check.
  48          * @param {int} index The index of the reference in the references.
  49          * @param {Reference[]} references The array that the reference belongs to.
  50          * @returns {void}
  51          */
  52         function checkReference(reference, index, references) {
  53             const identifier = reference.identifier;
  54
  55             if (reference.init === false &&
  56                 reference.isWrite() &&
  57
  58                 /*
  59                  * Destructuring assignments can have multiple default value,
  60                  * so possibly there are multiple writeable references for the same identifier.
  61                  */
  62                 (index === 0 || references[index - 1].identifier !== identifier)
  63             ) {
  64                 context.report({
  65                     node: identifier,
  66                     messageId: "globalShouldNotBeModified",
  67                     data: {
  68                         name: identifier.name
  69                     }
  70                 });
  71             }
  72         }
  73
  74         /**
  75          * Reports write references if a given variable is read-only builtin.
  76          * @param {Variable} variable A variable to check.
  77          * @returns {void}
  78          */
  79         function checkVariable(variable) {
  80             if (variable.writeable === false && exceptions.indexOf(variable.name) === -1) {
  81                 variable.references.forEach(checkReference);
  82             }
  83         }
  84
  85         return {
  86             Program() {
  87                 const globalScope = context.getScope();
  88
  89                 globalScope.variables.forEach(checkVariable);
  90             }
  91         };
  92     }
  93 };