Wrap catchup error to preserve original error message

Signed-off-by: Maurice van Veen <github@mauricevanveen.com>

server/jetstream_cluster.go

@@ -8280,6 +8280,19 @@ var (
 	errCatchupTooManyRetries  = errors.New("catchup failed, too many retries")
 )
 
+type catchupErr struct {
+	msg string
+	err error
+}
+
+func (e *catchupErr) Error() string {
+	return e.msg
+}
+
+func (e *catchupErr) Unwrap() error {
+	return e.err
+}
+
 // Process a stream snapshot.
 func (mset *stream) processSnapshot(snap *StreamReplicatedState) (e error) {
 	// Update any deletes, etc.
@@ -8380,7 +8393,10 @@ RETRY:
 	releaseSyncOutSem()
 
 	if n.GroupLeader() == _EMPTY_ {
-		return errors.Join(errCatchupAbortedNoLeader, fmt.Errorf("catchup for stream '%s > %s' aborted, no leader", mset.account(), mset.name()))
+		return &catchupErr{
+			msg: fmt.Sprintf("catchup for stream '%s > %s' aborted, no leader", mset.account(), mset.name()),
+			err: errCatchupAbortedNoLeader,
+		}
 	}
 
 	// If we have a sub clear that here.

server/jetstream_cluster_4_test.go

@@ -4119,7 +4119,7 @@ func TestJetStreamClusterDesyncAfterErrorDuringCatchup(t *testing.T) {
 				var snap StreamReplicatedState
 				snap.LastSeq = 1_000 // ensure we can catchup based on the snapshot
 				err := mset.processSnapshot(&snap)
-				require_Error(t, err, errCatchupAbortedNoLeader)
+				require_True(t, errors.Is(err, errCatchupAbortedNoLeader))
 				require_True(t, isClusterResetErr(err))
 				mset.resetClusteredState(err)
 			},