LibRegex: Generate a 'Compare' op for empty character classes

Otherwise it would match zero-length strings. Fixes SerenityOS#6256.
luteresa · Apr 12, 2021 · 5a14f7e · 5a14f7e
1 parent 7c98a6b
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diff --git a/Userland/Libraries/LibJS/Tests/builtins/RegExp/RegExp.prototype.exec.js b/Userland/Libraries/LibJS/Tests/builtins/RegExp/RegExp.prototype.exec.js
@@ -136,3 +136,15 @@ test("brace quantifier with invalid contents", () => {
  expect(res.length).toBe(1);
  expect(res[0]).toBe("{{lit-746579221856449}}");
 });
+
+// #6256
+test("empty character class semantics", () => {
+ // Should not match zero-length strings.
+ let res = /[]/.exec("");
+ expect(res).toBe(null);
+
+ // Inverse form, should match anything.
+ res = /[^]/.exec("x");
+ expect(res.length).toBe(1);
+ expect(res[0]).toBe("x");
+});
diff --git a/Userland/Libraries/LibRegex/RegexParser.cpp b/Userland/Libraries/LibRegex/RegexParser.cpp
@@ -1418,6 +1418,9 @@ bool ECMA262Parser::parse_character_class(ByteCode& stack, size_t& match_length_
 
  if (match(TokenType::RightBracket)) {
  consume();
+ // Should only have at most an 'Inverse'
+ VERIFY(compares.size() <= 1);
+ stack.insert_bytecode_compare_values(move(compares));
  return true;
  }