fix(ledger): block encoding nil lists (#1558)

Signed-off-by: Chris Gianelloni <wolf31o2@blinklabs.io>

Author: wolf31o2

ledger/allegra/allegra.go

@@ -76,6 +76,27 @@ func (b *AllegraBlock) UnmarshalCBOR(cborData []byte) error {
 	return nil
 }
 
+func (b *AllegraBlock) MarshalCBOR() ([]byte, error) {
+	if b.Cbor() != nil {
+		return b.Cbor(), nil
+	}
+	// Ensure nil slices encode as empty arrays, not CBOR null
+	txBodies := b.TransactionBodies
+	if txBodies == nil {
+		txBodies = []AllegraTransactionBody{}
+	}
+	txWitnesses := b.TransactionWitnessSets
+	if txWitnesses == nil {
+		txWitnesses = []shelley.ShelleyTransactionWitnessSet{}
+	}
+	return cbor.Encode([]any{
+		b.BlockHeader,
+		txBodies,
+		txWitnesses,
+		b.TransactionMetadataSet,
+	})
+}
+
 func (AllegraBlock) Type() int {
 	return BlockTypeAllegra
 }

ledger/alonzo/alonzo.go

@@ -102,6 +102,16 @@ func (b *AlonzoBlock) MarshalCBOR() ([]byte, error) {
 		InvalidTransactions    cbor.IndefLengthList
 	}
 
+	// Ensure nil slices encode as empty arrays, not CBOR null
+	txBodies := b.TransactionBodies
+	if txBodies == nil {
+		txBodies = []AlonzoTransactionBody{}
+	}
+	txWitnesses := b.TransactionWitnessSets
+	if txWitnesses == nil {
+		txWitnesses = []AlonzoTransactionWitnessSet{}
+	}
+
 	// Convert InvalidTransactions to IndefLengthList
 	var invalidTx cbor.IndefLengthList
 	if b.InvalidTransactions != nil {
@@ -113,8 +123,8 @@ func (b *AlonzoBlock) MarshalCBOR() ([]byte, error) {
 
 	temp := tmpBlock{
 		BlockHeader:            b.BlockHeader,
-		TransactionBodies:      b.TransactionBodies,
-		TransactionWitnessSets: b.TransactionWitnessSets,
+		TransactionBodies:      txBodies,
+		TransactionWitnessSets: txWitnesses,
 		TransactionMetadataSet: b.TransactionMetadataSet,
 		InvalidTransactions:    invalidTx,
 	}

ledger/babbage/babbage.go

@@ -138,16 +138,27 @@ func (b *BabbageBlock) MarshalCBOR() ([]byte, error) {
 		return b.Cbor(), nil
 	}
 
-	// Ensure InvalidTransactions is encoded as empty array if nil
+	// Ensure nil slices are encoded as empty CBOR arrays (0x80)
+	// rather than CBOR null (0xF6). The Cardano CDDL requires
+	// arrays for transaction_bodies, transaction_witness_sets,
+	// and invalid_transactions.
+	txBodies := b.TransactionBodies
+	if txBodies == nil {
+		txBodies = []BabbageTransactionBody{}
+	}
+	txWitnesses := b.TransactionWitnessSets
+	if txWitnesses == nil {
+		txWitnesses = []BabbageTransactionWitnessSet{}
+	}
 	invalidTxs := b.InvalidTransactions
 	if invalidTxs == nil {
 		invalidTxs = []uint{}
 	}
 
 	return cbor.Encode([]any{
 		b.BlockHeader,
-		b.TransactionBodies,
-		b.TransactionWitnessSets,
+		txBodies,
+		txWitnesses,
 		b.TransactionMetadataSet,
 		invalidTxs,
 	})

ledger/conway/conway.go

@@ -139,16 +139,27 @@ func (b *ConwayBlock) MarshalCBOR() ([]byte, error) {
 		return b.Cbor(), nil
 	}
 
-	// Ensure InvalidTransactions is encoded as empty array if nil
+	// Ensure nil slices are encoded as empty CBOR arrays (0x80)
+	// rather than CBOR null (0xF6). The Cardano CDDL requires
+	// arrays for transaction_bodies, transaction_witness_sets,
+	// and invalid_transactions.
+	txBodies := b.TransactionBodies
+	if txBodies == nil {
+		txBodies = []ConwayTransactionBody{}
+	}
+	txWitnesses := b.TransactionWitnessSets
+	if txWitnesses == nil {
+		txWitnesses = []ConwayTransactionWitnessSet{}
+	}
 	invalidTxs := b.InvalidTransactions
 	if invalidTxs == nil {
 		invalidTxs = []uint{}
 	}
 
 	return cbor.Encode([]any{
 		b.BlockHeader,
-		b.TransactionBodies,
-		b.TransactionWitnessSets,
+		txBodies,
+		txWitnesses,
 		b.TransactionMetadataSet,
 		invalidTxs,
 	})

ledger/mary/mary.go

@@ -85,8 +85,21 @@ func (b *MaryBlock) MarshalCBOR() ([]byte, error) {
 	if b.Cbor() != nil {
 		return b.Cbor(), nil
 	}
-	// Otherwise, encode generically
-	return cbor.EncodeGeneric(b)
+	// Ensure nil slices encode as empty arrays, not CBOR null
+	txBodies := b.TransactionBodies
+	if txBodies == nil {
+		txBodies = []MaryTransactionBody{}
+	}
+	txWitnesses := b.TransactionWitnessSets
+	if txWitnesses == nil {
+		txWitnesses = []shelley.ShelleyTransactionWitnessSet{}
+	}
+	return cbor.Encode([]any{
+		b.BlockHeader,
+		txBodies,
+		txWitnesses,
+		b.TransactionMetadataSet,
+	})
 }
 
 func (MaryBlock) Type() int {

ledger/shelley/shelley.go

@@ -83,6 +83,27 @@ func (b *ShelleyBlock) UnmarshalCBOR(cborData []byte) error {
 	return nil
 }
 
+func (b *ShelleyBlock) MarshalCBOR() ([]byte, error) {
+	if b.Cbor() != nil {
+		return b.Cbor(), nil
+	}
+	// Ensure nil slices encode as empty arrays, not CBOR null
+	txBodies := b.TransactionBodies
+	if txBodies == nil {
+		txBodies = []ShelleyTransactionBody{}
+	}
+	txWitnesses := b.TransactionWitnessSets
+	if txWitnesses == nil {
+		txWitnesses = []ShelleyTransactionWitnessSet{}
+	}
+	return cbor.Encode([]any{
+		b.BlockHeader,
+		txBodies,
+		txWitnesses,
+		b.TransactionMetadataSet,
+	})
+}
+
 func (ShelleyBlock) Type() int {
 	return BlockTypeShelley
 }