address PR comments

arbnode/transaction_streamer.go

@@ -478,8 +478,11 @@ func (s *TransactionStreamer) getMessageWithMetadataAndBlockInfo(seqNum arbutil.
 
 	key = dbKey(blockMetadataInputFeedPrefix, uint64(seqNum))
 	blockMetadata, err := s.db.Get(key)
-	if err != nil && !dbutil.IsErrNotFound(err) {
-		return nil, err
+	if err != nil {
+		if !dbutil.IsErrNotFound(err) {
+			return nil, err
+		}
+		blockMetadata = nil
 	}
 
 	msgWithBlockInfo := arbostypes.MessageWithMetadataAndBlockInfo{
@@ -1099,13 +1102,16 @@ func (s *TransactionStreamer) writeMessages(pos arbutil.MessageIndex, messages [
 
 func (s *TransactionStreamer) BlockMetadataAtCount(count arbutil.MessageIndex) (arbostypes.BlockMetadata, error) {
 	if count == 0 {
-		return []byte{}, nil
+		return nil, nil
 	}
 	pos := count - 1
 
 	key := dbKey(blockMetadataInputFeedPrefix, uint64(pos))
 	blockMetadata, err := s.db.Get(key)
-	if err != nil && !dbutil.IsErrNotFound(err) {
+	if err != nil {
+		if dbutil.IsErrNotFound(err) {
+			return nil, nil
+		}
 		return nil, err
 	}
 	return blockMetadata, nil

arbos/arbostypes/messagewithmeta.go

@@ -3,6 +3,7 @@ package arbostypes
 import (
 	"context"
 	"encoding/binary"
+	"errors"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -36,12 +37,18 @@ var TestMessageWithMetadataAndRequestId = MessageWithMetadata{
 }
 
 // IsTxTimeboosted given a tx's index in the block returns whether the tx was timeboosted or not
-func (b BlockMetadata) IsTxTimeboosted(txIndex int) bool {
+func (b BlockMetadata) IsTxTimeboosted(txIndex int) (bool, error) {
+	if len(b) == 0 {
+		return false, errors.New("blockMetadata is not set")
+	}
+	if txIndex < 0 {
+		return false, fmt.Errorf("invalid transaction index- %d, should be positive", txIndex)
+	}
 	maxTxCount := (len(b) - 1) * 8
 	if txIndex >= maxTxCount {
-		return false
+		return false, nil
 	}
-	return b[1+(txIndex/8)]&(1<<(txIndex%8)) != 0
+	return b[1+(txIndex/8)]&(1<<(txIndex%8)) != 0, nil
 }
 
 func (m *MessageWithMetadata) Hash(sequenceNumber arbutil.MessageIndex, chainId uint64) (common.Hash, error) {

broadcaster/message/message_blockmetadata_test.go

@@ -30,11 +30,13 @@ func TestTimeboostedInDifferentScenarios(t *testing.T) {
 		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
-			for txIndex, isTxTimeBoosted := range tc.txs {
-				if isTxTimeBoosted && !tc.blockMetadata.IsTxTimeboosted(txIndex) {
-					t.Fatalf("incorrect timeboosted bit for tx of index %d, it should be timeboosted", txIndex)
-				} else if !isTxTimeBoosted && tc.blockMetadata.IsTxTimeboosted(txIndex) {
-					t.Fatalf("incorrect timeboosted bit for tx of index %d, it shouldn't be timeboosted", txIndex)
+			for txIndex, want := range tc.txs {
+				have, err := tc.blockMetadata.IsTxTimeboosted(txIndex)
+				if err != nil {
+					t.Fatalf("error getting timeboosted bit for tx of index %d: %v", txIndex, err)
+				}
+				if want != have {
+					t.Fatalf("incorrect timeboosted bit for tx of index %d, Got: %v, Want: %v", txIndex, have, want)
 				}
 			}
 		})

system_tests/timeboost_test.go

@@ -150,14 +150,16 @@ func TestSequencerFeed_ExpressLaneAuction_ExpressLaneTxsHaveAdvantage_Timebooste
 		Require(t, err)
 		var foundUserTx bool
 		for txIndex, tx := range userTxBlock.Transactions() {
+			got, err := blockMetadataOfBlock.IsTxTimeboosted(txIndex)
+			Require(t, err)
 			if tx.Hash() == userTx.Hash() {
 				foundUserTx = true
-				if !isTimeboosted && blockMetadataOfBlock.IsTxTimeboosted(txIndex) {
+				if !isTimeboosted && got {
 					t.Fatalf("incorrect timeboosted bit for %s's tx, it shouldn't be timeboosted", user)
-				} else if isTimeboosted && !blockMetadataOfBlock.IsTxTimeboosted(txIndex) {
+				} else if isTimeboosted && !got {
 					t.Fatalf("incorrect timeboosted bit for %s's tx, it should be timeboosted", user)
 				}
-			} else if blockMetadataOfBlock.IsTxTimeboosted(txIndex) {
+			} else if got {
 				// Other tx's right now shouln't be timeboosted
 				t.Fatalf("incorrect timeboosted bit for nonspecified tx with index: %d, it shouldn't be timeboosted", txIndex)
 			}