accept nil, but handle it

proxy/grpc/server.go

@@ -53,11 +53,8 @@ func (s *proxyInputSrv) SubmitRollupTransaction(ctx context.Context, req *pbseq.
 
 // GetNextBatch returns the next batch of transactions from sequencer to rollup.
 func (s *proxyOutputSrv) GetNextBatch(ctx context.Context, req *pbseq.Batch) (*pbseq.Batch, error) {
-	var lastBatch *sequencing.Batch
-	if req.Transactions != nil {
-		lastBatch = &sequencing.Batch{}
-		lastBatch.FromProto(req)
-	}
+	lastBatch := &sequencing.Batch{}
+	lastBatch.FromProto(req)
 	batch, err := s.SequencerOutput.GetNextBatch(ctx, lastBatch)
 	if err != nil {
 		return nil, err
@@ -70,11 +67,8 @@ func (s *proxyOutputSrv) GetNextBatch(ctx context.Context, req *pbseq.Batch) (*p
 
 // VerifyBatch verifies a batch of transactions received from the sequencer.
 func (s *proxyVerificationSrv) VerifyBatch(ctx context.Context, req *pbseq.Batch) (*pbseq.VerificationResponse, error) {
-	var batch *sequencing.Batch
-	if req.Transactions != nil {
-		batch = &sequencing.Batch{}
-		batch.FromProto(req)
-	}
+	batch := &sequencing.Batch{}
+	batch.FromProto(req)
 	ok, err := s.BatchVerifier.VerifyBatch(ctx, batch)
 	if err != nil {
 		return nil, err

serialization.go

@@ -6,11 +6,7 @@ import (
 
 // ToProto serializes a batch to a protobuf message.
 func (batch *Batch) ToProto() *pbseq.Batch {
-	var txs [][]byte
-	if batch != nil {
-		txs = batch.Transactions
-	}
-	return &pbseq.Batch{Transactions: txsToByteSlices(txs)}
+	return &pbseq.Batch{Transactions: txsToByteSlices(batch.Transactions)}
 }
 
 // FromProto deserializes a batch from a protobuf message.
@@ -38,12 +34,7 @@ func byteSlicesToTxs(bytes [][]byte) []Tx {
 
 // Marshal serializes a batch to a byte slice.
 func (batch *Batch) Marshal() ([]byte, error) {
-	var b []byte
-	if batch == nil {
-		return b, nil
-	}
-	pb := batch.ToProto()
-	return pb.Marshal()
+	return batch.ToProto().Marshal()
 }
 
 // Unmarshal deserializes a batch from a byte slice.

test/dummy.go

@@ -74,10 +74,10 @@ func (d *DummySequencer) SubmitRollupTransaction(ctx context.Context, rollupId [
 // GetNextBatch implements sequencing.Sequencer.
 func (d *DummySequencer) GetNextBatch(ctx context.Context, lastBatch *sequencing.Batch) (*sequencing.Batch, error) {
 	if d.lastBatchHash == nil {
-		if lastBatch != nil {
+		if lastBatch.Transactions != nil {
 			return nil, errors.New("lastBatch is supposed to be nil")
 		}
-	} else if lastBatch == nil {
+	} else if lastBatch.Transactions == nil {
 		return nil, errors.New("lastBatch is not supposed to be nil")
 	} else {
 		lastBatchBytes, err := lastBatch.Marshal()