LibRegex: Add basic support for unicode escapes in ECMA262Parser

This parses unicode escapes (and matches them only for utf8 strings).

2 files changed, 31 insertions, 4 deletions

diff --git a/Libraries/LibRegex/RegexParser.cpp b/Libraries/LibRegex/RegexParser.cpp
index ca86012f53..6015212123 100644
--- a/Libraries/LibRegex/RegexParser.cpp
+++ b/Libraries/LibRegex/RegexParser.cpp
@@ -1066,8 +1066,24 @@ bool ECMA262Parser::parse_atom_escape(ByteCode& stack, size_t& match_length_mini
     }
 
     if (try_skip("u")) {
-        // FIXME: Implement this path, unicode escape sequence.
-        TODO();
+        if (auto code_point = read_digits(ReadDigitsInitialZeroState::Allow, ReadDigitFollowPolicy::Any, true, 4); code_point.has_value()) {
+            // FIXME: The minimum length depends on the mode - should be utf8-length in u8 mode.
+            match_length_minimum += 1;
+            StringBuilder builder;
+            builder.append_code_point(code_point.value());
+            // FIXME: This isn't actually correct for ECMAScript.
+            auto u8_encoded = builder.string_view();
+            stack.insert_bytecode_compare_string(u8_encoded);
+            return true;
+        } else if (!unicode) {
+            // '\u' is allowed in non-unicode mode, just matches 'u'.
+            match_length_minimum += 1;
+            stack.insert_bytecode_compare_values({ { CharacterCompareType::Char, (ByteCodeValueType)'u' } });
+            return true;
+        } else {
+            set_error(Error::InvalidPattern);
+            return false;
+        }
     }
 
     // IdentityEscape
@@ -1261,8 +1277,16 @@ bool ECMA262Parser::parse_nonempty_class_ranges(Vector<CompareTypeAndValuePair>&
             }
 
             if (try_skip("u")) {
-                // FIXME: Implement this path, unicode escape sequence.
-                TODO();
+                if (auto code_point = read_digits(ReadDigitsInitialZeroState::Allow, ReadDigitFollowPolicy::Any, true, 4); code_point.has_value()) {
+                    // FIXME: While codepoint ranges are supported, codepoint matches as "Char" are not!
+                    return { { .code_point = code_point.value(), .is_character_class = false } };
+                } else if (!unicode) {
+                    // '\u' is allowed in non-unicode mode, just matches 'u'.
+                    return { { .code_point = 'u', .is_character_class = false } };
+                } else {
+                    set_error(Error::InvalidPattern);
+                    return {};
+                }
             }
 
             if (unicode) {
diff --git a/Libraries/LibRegex/Tests/Regex.cpp b/Libraries/LibRegex/Tests/Regex.cpp
index c4aa8c8d7e..d9c5f7ce31 100644
--- a/Libraries/LibRegex/Tests/Regex.cpp
+++ b/Libraries/LibRegex/Tests/Regex.cpp
@@ -477,6 +477,7 @@ TEST_CASE(ECMA262_parse)
     struct _test {
         const char* pattern;
         regex::Error expected_error { regex::Error::NoError };
+        regex::ECMAScriptFlags flags {};
     };
 
     constexpr _test tests[] {
@@ -497,6 +498,8 @@ TEST_CASE(ECMA262_parse)
         { "\\x" },                                         // Even invalid escapes are allowed if ~unicode.
         { "\\", regex::Error::InvalidTrailingEscape },
         { "(?", regex::Error::InvalidCaptureGroup },
+        { "\\u1234", regex::Error::NoError, regex::ECMAScriptFlags::Unicode },
+        { "[\\u1234]", regex::Error::NoError, regex::ECMAScriptFlags::Unicode },
     };
 
     for (auto& test : tests) {