fix(txn): ensure that txn hash is set (#7782) (#7784)

We were setting the hash after completing the transaction successfully. This leads to the failure of the commit as it won't contain the hash. This PR fixes that issue.

(cherry picked from commit ae029f0)

edgraph/server.go

@@ -1252,6 +1252,18 @@ func (s *Server) doQuery(ctx context.Context, req *Request) (
 			qc.latency.AssignTimestamp = time.Since(start)
 		}
 	}
+	if x.WorkerConfig.AclEnabled {
+		ns, err := x.ExtractNamespace(ctx)
+		if err != nil {
+			return nil, err
+		}
+		defer func() {
+			if resp != nil && resp.Txn != nil {
+				// attach the hash, user must send this hash when further operating on this startTs.
+				resp.Txn.Hash = getHash(ns, resp.Txn.StartTs)
+			}
+		}()
+	}
 
 	var gqlErrs error
 	if resp, rerr = processQuery(ctx, qc); rerr != nil {
@@ -1285,14 +1297,6 @@ func (s *Server) doQuery(ctx context.Context, req *Request) (
 		EncodingNs:        uint64(l.Json.Nanoseconds()),
 		TotalNs:           uint64((time.Since(l.Start)).Nanoseconds()),
 	}
-	if x.WorkerConfig.AclEnabled {
-		// attach the hash, user should send this hash when further operating on this startTs.
-		ns, err := x.ExtractNamespace(ctx)
-		if err != nil {
-			return nil, err
-		}
-		resp.Txn.Hash = getHash(ns, resp.Txn.StartTs)
-	}
 	md := metadata.Pairs(x.DgraphCostHeader, fmt.Sprint(resp.Metrics.NumUids["_total"]))
 	grpc.SendHeader(ctx, md)
 	return resp, gqlErrs