Better reconstruct error msg while EL client is syncing (#11851)

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

beacon-chain/execution/engine_client.go

@@ -86,6 +86,8 @@ type EngineCaller interface {
 	GetTerminalBlockHash(ctx context.Context, transitionTime uint64) ([]byte, bool, error)
 }
 
+var EmptyBlockHash = errors.New("Block hash is empty 0x0000...")
+
 // NewPayload calls the engine_newPayloadVX method via JSON-RPC.
 func (s *Service) NewPayload(ctx context.Context, payload interfaces.ExecutionData) ([]byte, error) {
 	ctx, span := trace.StartSpan(ctx, "powchain.engine-api-client.NewPayload")
@@ -471,6 +473,10 @@ func (s *Service) ReconstructFullBlock(
 	if executionBlock == nil {
 		return nil, fmt.Errorf("received nil execution block for request by hash %#x", executionBlockHash)
 	}
+	if bytes.Equal(executionBlock.Hash.Bytes(), []byte{}) {
+		return nil, EmptyBlockHash
+	}
+
 	executionBlock.Version = blindedBlock.Version()
 	payload, err := fullPayloadFromExecutionBlock(header, executionBlock)
 	if err != nil {

beacon-chain/sync/rpc_beacon_blocks_by_root.go

@@ -6,6 +6,7 @@ import (
 	libp2pcore "github.com/libp2p/go-libp2p/core"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/v3/beacon-chain/execution"
 	"github.com/prysmaticlabs/prysm/v3/beacon-chain/p2p/types"
 	"github.com/prysmaticlabs/prysm/v3/config/params"
 	"github.com/prysmaticlabs/prysm/v3/consensus-types/blocks"
@@ -77,7 +78,11 @@ func (s *Service) beaconBlocksRootRPCHandler(ctx context.Context, msg interface{
 		if blk.Block().IsBlinded() {
 			blk, err = s.cfg.executionPayloadReconstructor.ReconstructFullBlock(ctx, blk)
 			if err != nil {
-				log.WithError(err).Error("Could not get reconstruct full bellatrix block from blinded body")
+				if errors.Is(err, execution.EmptyBlockHash) {
+					log.WithError(err).Warn("Could not reconstruct block from header with syncing execution client. Waiting to complete syncing")
+				} else {
+					log.WithError(err).Error("Could not get reconstruct full block from blinded body")
+				}
 				s.writeErrorResponseToStream(responseCodeServerError, types.ErrGeneric.Error(), stream)
 				return err
 			}