LibRegex: Allow ClearCaptureGroup to create new groups

Instead of leaking all capture groups and selectively clearing some,
simply avoid leaking things and only "define" the ones that need to
exist.
This *actually* implements the capture groups ECMA262 quirk.
Also adds the test removed in the previous commit (to avoid messing up
test runs across bisects).

1 files changed, 5 insertions, 2 deletions

diff --git a/Userland/Libraries/LibRegex/RegexByteCode.cpp b/Userland/Libraries/LibRegex/RegexByteCode.cpp
index 6177a1f3e2..050f067ae0 100644
--- a/Userland/Libraries/LibRegex/RegexByteCode.cpp
+++ b/Userland/Libraries/LibRegex/RegexByteCode.cpp
@@ -329,8 +329,11 @@ ALWAYS_INLINE ExecutionResult OpCode_ClearCaptureGroup::execute(MatchInput const
 {
     if (input.match_index < state.capture_group_matches.size()) {
         auto& group = state.capture_group_matches[input.match_index];
-        if (id() < group.size())
-            group[id()].reset();
+        auto group_id = id();
+        if (group_id >= group.size())
+            group.resize(group_id + 1);
+
+        group[group_id].reset();
     }
     return ExecutionResult::Continue;
 }