Fix trace pending txns

Author: wojciechos

rpc/trace.go

@@ -142,6 +142,18 @@ func (h *Handler) traceTransaction(ctx context.Context, hash *felt.Felt) (*vm.Tr
 	httpHeader.Set(ExecutionStepsHeader, "0")
 
 	if err != nil {
+		if pendingB := h.syncReader.PendingBlock(); pendingB != nil {
+			txIndex := slices.IndexFunc(pendingB.Transactions, func(tx core.Transaction) bool {
+				return tx.Hash().Equal(hash)
+			})
+			if txIndex != -1 {
+				traceResults, header, traceBlockErr := h.traceBlockTransactions(ctx, pendingB)
+				if traceBlockErr != nil {
+					return nil, header, traceBlockErr
+				}
+				return traceResults[txIndex].TraceRoot, header, nil
+			}
+		}
 		return nil, httpHeader, ErrTxnHashNotFound
 	}