eslint/lib/rules/no-empty-character-class.js

   1 /**
   2  * @fileoverview Rule to flag the use of empty character classes in regular expressions
   3  * @author Ian Christian Myers
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Helpers
  10 //------------------------------------------------------------------------------
  11
  12 /*
  13  * plain-English description of the following regexp:
  14  * 0. `^` fix the match at the beginning of the string
  15  * 1. `([^\\[]|\\.|\[([^\\\]]|\\.)+\])*`: regexp contents; 0 or more of the following
  16  * 1.0. `[^\\[]`: any character that's not a `\` or a `[` (anything but escape sequences and character classes)
  17  * 1.1. `\\.`: an escape sequence
  18  * 1.2. `\[([^\\\]]|\\.)+\]`: a character class that isn't empty
  19  * 2. `$`: fix the match at the end of the string
  20  */
  21 const regex = /^([^\\[]|\\.|\[([^\\\]]|\\.)+\])*$/u;
  22
  23 //------------------------------------------------------------------------------
  24 // Rule Definition
  25 //------------------------------------------------------------------------------
  26
  27 /** @type {import('../shared/types').Rule} */
  28 module.exports = {
  29     meta: {
  30         type: "problem",
  31
  32         docs: {
  33             description: "Disallow empty character classes in regular expressions",
  34             recommended: true,
  35             url: "https://eslint.org/docs/latest/rules/no-empty-character-class"
  36         },
  37
  38         schema: [],
  39
  40         messages: {
  41             unexpected: "Empty class."
  42         }
  43     },
  44
  45     create(context) {
  46         return {
  47             "Literal[regex]"(node) {
  48                 if (!regex.test(node.regex.pattern)) {
  49                     context.report({ node, messageId: "unexpected" });
  50                 }
  51             }
  52         };
  53
  54     }
  55 };