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feat: no-empty-character-class support v flag (#17419)
Reports nested character classes Refs #17223
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‎docs/src/rules/no-empty-character-class.md‎

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@@ -24,6 +24,23 @@ Examples of **incorrect** code for this rule:
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/^abc[]/.test("abcdefg"); // false
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"abcdefg".match(/^abc[]/); // null
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/^abc[[]]/v.test("abcdefg"); // false
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"abcdefg".match(/^abc[[]]/v); // null
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/^abc[[]--[x]]/v.test("abcdefg"); // false
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"abcdefg".match(/^abc[[]--[x]]/v); // null
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/^abc[[d]&&[]]/v.test("abcdefg"); // false
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"abcdefg".match(/^abc[[d]&&[]]/v); // null
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const regex = /^abc[d[]]/v;
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regex.test("abcdefg"); // true, the nested `[]` has no effect
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"abcdefg".match(regex); // ["abcd"]
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regex.test("abcefg"); // false, the nested `[]` has no effect
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"abcefg".match(regex); // null
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regex.test("abc"); // false, the nested `[]` has no effect
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"abc".match(regex); // null
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```
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:::
@@ -40,6 +57,9 @@ Examples of **correct** code for this rule:
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/^abc[a-z]/.test("abcdefg"); // true
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"abcdefg".match(/^abc[a-z]/); // ["abcd"]
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/^abc[^]/.test("abcdefg"); // true
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"abcdefg".match(/^abc[^]/); // ["abcd"]
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```
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:::

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

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@@ -5,20 +5,18 @@
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const { RegExpParser, visitRegExpAST } = require("@eslint-community/regexpp");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/*
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* plain-English description of the following regexp:
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* 0. `^` fix the match at the beginning of the string
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* 1. `([^\\[]|\\.|\[([^\\\]]|\\.)+\])*`: regexp contents; 0 or more of the following
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* 1.0. `[^\\[]`: any character that's not a `\` or a `[` (anything but escape sequences and character classes)
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* 1.1. `\\.`: an escape sequence
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* 1.2. `\[([^\\\]]|\\.)+\]`: a character class that isn't empty
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* 2. `$`: fix the match at the end of the string
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*/
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const regex = /^([^\\[]|\\.|\[([^\\\]]|\\.)+\])*$/u;
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const parser = new RegExpParser();
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const QUICK_TEST_REGEX = /\[\]/u;
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//------------------------------------------------------------------------------
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// Rule Definition
@@ -45,9 +43,32 @@ module.exports = {
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create(context) {
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return {
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"Literal[regex]"(node) {
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if (!regex.test(node.regex.pattern)) {
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context.report({ node, messageId: "unexpected" });
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const { pattern, flags } = node.regex;
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if (!QUICK_TEST_REGEX.test(pattern)) {
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return;
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}
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let regExpAST;
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try {
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regExpAST = parser.parsePattern(pattern, 0, pattern.length, {
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unicode: flags.includes("u"),
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unicodeSets: flags.includes("v")
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});
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} catch {
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// Ignore regular expressions that regexpp cannot parse
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return;
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}
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visitRegExpAST(regExpAST, {
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onCharacterClassEnter(characterClass) {
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if (!characterClass.negate && characterClass.elements.length === 0) {
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context.report({ node, messageId: "unexpected" });
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}
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}
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});
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}
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};
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‎tests/lib/rules/no-empty-character-class.js‎

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@@ -25,15 +25,26 @@ ruleTester.run("no-empty-character-class", rule, {
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"var foo = /^abc/;",
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"var foo = /[\\[]/;",
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"var foo = /[\\]]/;",
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"var foo = /\\[][\\]]/;",
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"var foo = /[a-zA-Z\\[]/;",
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"var foo = /[[]/;",
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"var foo = /[\\[a-z[]]/;",
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"var foo = /[\\-\\[\\]\\/\\{\\}\\(\\)\\*\\+\\?\\.\\\\^\\$\\|]/g;",
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"var foo = /\\s*:\\s*/gim;",
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"var foo = /[^]/;", // this rule allows negated empty character classes
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"var foo = /\\[][^]/;",
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{ code: "var foo = /[\\]]/uy;", parserOptions: { ecmaVersion: 6 } },
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{ code: "var foo = /[\\]]/s;", parserOptions: { ecmaVersion: 2018 } },
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{ code: "var foo = /[\\]]/d;", parserOptions: { ecmaVersion: 2022 } },
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"var foo = /\\[]/"
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"var foo = /\\[]/",
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{ code: "var foo = /[[^]]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[[\\]]]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[[\\[]]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[a--b]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[a&&b]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[[a][b]]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[\\q{}]/v;", parserOptions: { ecmaVersion: 2024 } },
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{ code: "var foo = /[[^]--\\p{ASCII}]/v;", parserOptions: { ecmaVersion: 2024 } }
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],
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invalid: [
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{ code: "var foo = /^abc[]/;", errors: [{ messageId: "unexpected", type: "Literal" }] },
@@ -43,6 +54,15 @@ ruleTester.run("no-empty-character-class", rule, {
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{ code: "var foo = /[]]/;", errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /\\[[]/;", errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /\\[\\[\\]a-z[]/;", errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[]]/d;", parserOptions: { ecmaVersion: 2022 }, errors: [{ messageId: "unexpected", type: "Literal" }] }
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{ code: "var foo = /[]]/d;", parserOptions: { ecmaVersion: 2022 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[(]\\u{0}*[]/u;", parserOptions: { ecmaVersion: 2015 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[[]]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[[a][]]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[a[[b[]c]]d]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[a--[]]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[[]--b]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[a&&[]]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
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{ code: "var foo = /[[]&&b]/v;", parserOptions: { ecmaVersion: 2024 }, errors: [{ messageId: "unexpected", type: "Literal" }] }
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]
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});

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