restore Clone, but encourage ShallowClone

Author: rohenaz

script/interpreter/operations.go

@@ -2016,7 +2016,7 @@ func opcodeCheckSig(op *ParsedOpcode, t *thread) error {
 		return err
 	}
 
-	txCopy := t.tx.Clone()
+	txCopy := t.tx.ShallowClone()
 	sourceTxOut := txCopy.Inputs[t.inputIdx].SourceTxOutput()
 	sourceTxOut.LockingScript = up
 
@@ -2282,7 +2282,7 @@ func opcodeCheckMultiSig(op *ParsedOpcode, t *thread) error {
 		}
 
 		// Generate the signature hash based on the signature hash type.
-		txCopy := t.tx.Clone()
+		txCopy := t.tx.ShallowClone()
 		input := txCopy.Inputs[t.inputIdx]
 		sourceOut := input.SourceTxOutput()
 		if sourceOut != nil {

transaction/signaturehash.go

@@ -188,7 +188,7 @@ func (tx *Transaction) CalcInputPreimageLegacy(inputNumber uint32, shf sighash.F
 		return defaultHex, nil
 	}
 
-	txCopy := tx.Clone()
+	txCopy := tx.ShallowClone()
 
 	for i := range txCopy.Inputs {
 		if i == int(inputNumber) {

transaction/transaction.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"encoding/hex"
 	"io"
+	"log"
 	"slices"
 
 	"github.com/bitcoin-sv/go-sdk/chainhash"
@@ -313,7 +314,27 @@ func (tx *Transaction) BytesWithClearedInputs(index int, lockingScript []byte) [
 	return tx.toBytesHelper(index, lockingScript, false)
 }
 
+// Clone returns a deep clone of the tx. Consider using ShallowClone if
+// you don't need to clone the source transactions.
 func (tx *Transaction) Clone() *Transaction {
+	// Ignore err as byte slice passed in is created from valid tx
+	clone, err := NewTransactionFromBytes(tx.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for i, input := range tx.Inputs {
+		if input.SourceTransaction != nil {
+			clone.Inputs[i].SourceTransaction = input.SourceTransaction.Clone()
+		}
+		// clone.Inputs[i].SourceTransaction = input.SourceTransaction
+		clone.Inputs[i].sourceOutput = input.sourceOutput
+	}
+
+	return clone
+}
+
+func (tx *Transaction) ShallowClone() *Transaction {
 	// Creating a new Tx from scratch is much faster than cloning from bytes
 	// ~ 420ns/op vs 2200ns/op of the above function in benchmarking
 	// this matters as we clone txs a couple of times when verifying signatures

transaction/transaction_test.go

@@ -98,7 +98,7 @@ func TestClone(t *testing.T) {
 	tx, err := transaction.NewTransactionFromBEEFHex(BRC62Hex)
 	require.NoError(t, err)
 
-	clone := tx.Clone()
+	clone := tx.ShallowClone()
 	require.Equal(t, tx.Bytes(), clone.Bytes())
 }
 
@@ -107,7 +107,7 @@ func BenchmarkClone(b *testing.B) {
 
 	b.Run("clone", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
-			clone := tx.Clone()
+			clone := tx.ShallowClone()
 			_ = clone
 		}
 	})
@@ -132,7 +132,7 @@ func TestSignUnsigned(t *testing.T) {
 	tx, err := transaction.NewTransactionFromBEEFHex(BRC62Hex)
 	require.NoError(t, err)
 
-	cloneTx := tx.Clone()
+	cloneTx := tx.ShallowClone()
 	pk, _ := ec.NewPrivateKey()
 
 	// Adding a script template with random key so sigs will be different