feat(linter): eslint/no-empty-character-class (#635)

closes #559

crates/oxc_linter/src/rules.rs

@@ -31,6 +31,7 @@ oxc_macros::declare_all_lint_rules! {
     eslint::no_dupe_keys,
     eslint::no_duplicate_case,
     eslint::no_empty,
+    eslint::no_empty_character_class,
     eslint::no_empty_pattern,
     eslint::no_eval,
     eslint::no_ex_assign,

crates/oxc_linter/src/rules/eslint/no_empty_character_class.rs

@@ -0,0 +1,94 @@
+// Ported from https://github.com/eslint/eslint/blob/main/lib/rules/no-empty-character-class.js
+use lazy_static::lazy_static;
+use oxc_ast::AstKind;
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::Error,
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+use regex::Regex;
+
+use crate::{context::LintContext, rule::Rule, AstNode};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint(no-empty-character-class): Empty character class")]
+#[diagnostic(severity(warning), help("Try to remove empty character class `[]` in regexp literal"))]
+struct NoEmptyCharacterClassDiagnostic(#[label] pub Span);
+
+#[derive(Debug, Default, Clone)]
+pub struct NoEmptyCharacterClass;
+
+declare_oxc_lint!(
+    /// ### What it does
+    /// Disallow empty character classes in regular expressions
+    ///
+    /// ### Why is this bad?
+    /// Because empty character classes in regular expressions do not match anything, they might be typing mistakes.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// var foo = /^abc[]/;
+    /// ```
+    NoEmptyCharacterClass,
+    correctness
+);
+
+impl Rule for NoEmptyCharacterClass {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        lazy_static! {
+            /*
+            * 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
+            */
+            static ref NO_EMPTY_CLASS_REGEX_PATTERN: Regex =
+                Regex::new(r"^([^\\\[]|\\.|\[([^\\\]]|\\.)+\])*$").unwrap();
+        }
+
+        if let AstKind::RegExpLiteral(lit) = node.kind() {
+            if !NO_EMPTY_CLASS_REGEX_PATTERN.is_match(&lit.regex.pattern) {
+                ctx.diagnostic(NoEmptyCharacterClassDiagnostic(lit.span));
+            }
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        ("var foo = /^abc[a-zA-Z]/;", None),
+        ("var regExp = new RegExp(\"^abc[]\");", None),
+        ("var foo = /^abc/;", None),
+        ("var foo = /[\\[]/;", None),
+        ("var foo = /[\\]]/;", None),
+        ("var foo = /[a-zA-Z\\[]/;", None),
+        ("var foo = /[[]/;", None),
+        ("var foo = /[\\[a-z[]]/;", None),
+        ("var foo = /[\\-\\[\\]\\/\\{\\}\\(\\)\\*\\+\\?\\.\\\\^\\$\\|]/g;", None),
+        ("var foo = /\\s*:\\s*/gim;", None),
+        ("var foo = /[\\]]/uy;", None),
+        ("var foo = /[\\]]/s;", None),
+        ("var foo = /[\\]]/d;", None),
+        ("var foo = /\\[]/", None),
+    ];
+
+    let fail = vec![
+        ("var foo = /^abc[]/;", None),
+        ("var foo = /foo[]bar/;", None),
+        ("if (foo.match(/^abc[]/)) {}", None),
+        ("if (/^abc[]/.test(foo)) {}", None),
+        ("var foo = /[]]/;", None),
+        ("var foo = /\\[[]/;", None),
+        ("var foo = /\\[\\[\\]a-z[]/;", None),
+        ("var foo = /[]]/d;", None),
+    ];
+
+    Tester::new(NoEmptyCharacterClass::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/no_empty_character_class.snap

@@ -0,0 +1,62 @@
+---
+source: crates/oxc_linter/src/tester.rs
+assertion_line: 80
+expression: no_empty_character_class
+---
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ var foo = /^abc[]/;
+   ·           ────────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ var foo = /foo[]bar/;
+   ·           ──────────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ if (foo.match(/^abc[]/)) {}
+   ·               ────────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ if (/^abc[]/.test(foo)) {}
+   ·     ────────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ var foo = /[]]/;
+   ·           ─────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ var foo = /\[[]/;
+   ·           ──────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ var foo = /\[\[\]a-z[]/;
+   ·           ─────────────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+  ⚠ eslint(no-empty-character-class): Empty character class
+   ╭─[no_empty_character_class.tsx:1:1]
+ 1 │ var foo = /[]]/d;
+   ·           ──────
+   ╰────
+  help: Try to remove empty character class `[]` in regexp literal
+
+