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. `\/`: the `/` that begins the regexp
* 2. `([^\\[]|\\.|\[([^\\\]]|\\.)+\])*`: regexp contents; 0 or more of the following
* 2.0. `[^\\[]`: any character that's not a `\` or a `[` (anything but escape sequences and character classes)
* 2.1. `\\.`: an escape sequence
* 2.2. `\[([^\\\]]|\\.)+\]`: a character class that isn't empty
* 3. `\/` the `/` that ends the regexp
* 4. `[gimuy]*`: optional regexp flags
* 5. `$`: fix the match at the end of the string
*/
const regex = /^\/([^\\[]|\\.|\[([^\\\]]|\\.)+\])*\/[gimuys]*$/u;
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "problem",
docs: {
description: "disallow empty character classes in regular expressions",
category: "Possible Errors",
recommended: true,
url: "https://eslint.org/docs/rules/no-empty-character-class"
},
schema: [],
messages: {
unexpected: "Empty class."
}
},
create(context) {
const sourceCode = context.getSourceCode();
return {
Literal(node) {
const token = sourceCode.getFirstToken(node);
if (token.type === "RegularExpression" && !regex.test(token.value)) {
context.report({ node, messageId: "unexpected" });
}
}
};
}
};