no-empty-character-class.js
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/**
* @fileoverview Rule to flag the use of empty character classes in regular expressions
* @author Ian Christian Myers
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/*
* plain-English description of the following regexp:
* 0. `^` fix the match at the beginning of the string
* 1. `([^\\[]|\\.|\[([^\\\]]|\\.)+\])*`: regexp contents; 0 or more of the following
* 1.0. `[^\\[]`: any character that's not a `\` or a `[` (anything but escape sequences and character classes)
* 1.1. `\\.`: an escape sequence
* 1.2. `\[([^\\\]]|\\.)+\]`: a character class that isn't empty
* 2. `$`: fix the match at the end of the string
*/
const regex = /^([^\\[]|\\.|\[([^\\\]]|\\.)+\])*$/u;
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "problem",
docs: {
description: "Disallow empty character classes in regular expressions",
recommended: true,
url: "https://eslint.org/docs/rules/no-empty-character-class"
},
schema: [],
messages: {
unexpected: "Empty class."
}
},
create(context) {
return {
"Literal[regex]"(node) {
if (!regex.test(node.regex.pattern)) {
context.report({ node, messageId: "unexpected" });
}
}
};
}
};