txnbuild: Add ToXDR functions which do not return errors

txnbuild/CHANGELOG.md

@@ -6,6 +6,7 @@ file.  This project adheres to [Semantic Versioning](http://semver.org/).
 ## Unreleased
 
 * `txnbuild` now generates V1 transaction envelopes which are only supported by Protocol 13 ([#2640](https://github.com/stellar/go/pull/2640))
+* Add `ToXDR()` functions for `Transaction` and `FeeBumpTransaction` instances which return xdr transaction envelopes without errors ([#2651](https://github.com/stellar/go/pull/2651))
 
 ## [v3.1.0](https://github.com/stellar/go/releases/tag/horizonclient-v3.1.0) - 2020-05-14
 

txnbuild/signers_test.go

@@ -436,12 +436,15 @@ func TestSetOptionsMultSigners(t *testing.T) {
 	assert.Equal(t, expected, received, "Base 64 XDR should match")
 }
 
-type SignatureList interface {
+type transactionCommon interface {
 	Signatures() []xdr.DecoratedSignature
 	Hash(networkStr string) ([32]byte, error)
+	Base64() (string, error)
+	TxEnvelope() (xdr.TransactionEnvelope, error)
+	ToXDR() xdr.TransactionEnvelope
 }
 
-func verifySignatures(t *testing.T, tx SignatureList, signers ...*keypair.Full) {
+func verifySignatures(t *testing.T, tx transactionCommon, signers ...*keypair.Full) {
 	assert.Len(t, tx.Signatures(), len(signers))
 
 	hash, err := tx.Hash(network.TestNetworkPassphrase)
@@ -452,6 +455,25 @@ func verifySignatures(t *testing.T, tx SignatureList, signers ...*keypair.Full)
 	}
 }
 
+func assertBase64(t *testing.T, tx transactionCommon) string {
+	base64, err := tx.Base64()
+	assert.NoError(t, err)
+
+	envCopy, err := tx.TxEnvelope()
+	assert.NoError(t, err)
+	envCopyBase64, err := xdr.MarshalBase64(envCopy)
+	assert.NoError(t, err)
+
+	envRef := tx.ToXDR()
+	envRefBase64, err := xdr.MarshalBase64(envRef)
+	assert.NoError(t, err)
+
+	assert.Equal(t, base64, envCopyBase64)
+	assert.Equal(t, base64, envRefBase64)
+
+	return base64
+}
+
 func TestSigningImmutability(t *testing.T) {
 	kp0, kp1, kp2 := newKeypair0(), newKeypair1(), newKeypair2()
 
@@ -466,18 +488,15 @@ func TestSigningImmutability(t *testing.T) {
 	assert.NoError(t, err)
 	root, err = root.Sign(network.TestNetworkPassphrase, kp0)
 	assert.NoError(t, err)
-	rootB64, err := root.Base64()
-	assert.NoError(t, err)
+	rootB64 := assertBase64(t, root)
 
 	left, err := root.Sign(network.TestNetworkPassphrase, kp1)
 	assert.NoError(t, err)
-	leftB64, err := left.Base64()
-	assert.NoError(t, err)
+	leftB64 := assertBase64(t, left)
 
 	right, err := root.Sign(network.TestNetworkPassphrase, kp2)
 	assert.NoError(t, err)
-	rightB64, err := right.Base64()
-	assert.NoError(t, err)
+	rightB64 := assertBase64(t, right)
 
 	expectedRootB64, err := newSignedTransaction(
 		params, network.TestNetworkPassphrase, kp0,
@@ -521,18 +540,16 @@ func TestFeeBumpSigningImmutability(t *testing.T) {
 	root, err := NewFeeBumpTransaction(params)
 	assert.NoError(t, err)
 	root, err = root.Sign(network.TestNetworkPassphrase, kp1)
-	rootB64, err := root.Base64()
 	assert.NoError(t, err)
+	rootB64 := assertBase64(t, root)
 
 	left, err := root.Sign(network.TestNetworkPassphrase, kp0)
 	assert.NoError(t, err)
-	leftB64, err := left.Base64()
-	assert.NoError(t, err)
+	leftB64 := assertBase64(t, left)
 
 	right, err := root.Sign(network.TestNetworkPassphrase, kp2)
 	assert.NoError(t, err)
-	rightB64, err := right.Base64()
-	assert.NoError(t, err)
+	rightB64 := assertBase64(t, right)
 
 	expectedRootB64, err := newSignedFeeBumpTransaction(
 		params, network.TestNetworkPassphrase, kp1,

txnbuild/transaction.go

@@ -319,6 +319,23 @@ func (t *Transaction) TxEnvelope() (xdr.TransactionEnvelope, error) {
 	return cloneEnvelope(t.envelope, t.signatures)
 }
 
+// ToXDR is like TxEnvelope except that the transaction envelope returned by ToXDR
+// should not be modified because any changes applied to the transaction envelope may
+// affect the internals of the Transaction instance.
+func (t *Transaction) ToXDR() xdr.TransactionEnvelope {
+	env := t.envelope
+	switch env.Type {
+	case xdr.EnvelopeTypeEnvelopeTypeTx:
+		env.V1.Signatures = t.signatures
+	case xdr.EnvelopeTypeEnvelopeTypeTxV0:
+		env.V0.Signatures = t.signatures
+	default:
+		panic("invalid transaction type: " + env.Type.String())
+	}
+
+	return env
+}
+
 // MarshalBinary returns the binary XDR representation of the transaction envelope.
 func (t *Transaction) MarshalBinary() ([]byte, error) {
 	return marshallBinary(t.envelope, t.signatures)
@@ -432,6 +449,21 @@ func (t *FeeBumpTransaction) TxEnvelope() (xdr.TransactionEnvelope, error) {
 	return cloneEnvelope(t.envelope, t.signatures)
 }
 
+// ToXDR is like TxEnvelope except that the transaction envelope returned by ToXDR
+// should not be modified because any changes applied to the transaction envelope may
+// affect the internals of the FeeBumpTransaction instance.
+func (t *FeeBumpTransaction) ToXDR() xdr.TransactionEnvelope {
+	env := t.envelope
+	switch env.Type {
+	case xdr.EnvelopeTypeEnvelopeTypeTxFeeBump:
+		env.FeeBump.Signatures = t.signatures
+	default:
+		panic("invalid transaction type: " + env.Type.String())
+	}
+
+	return env
+}
+
 // MarshalBinary returns the binary XDR representation of the transaction envelope.
 func (t *FeeBumpTransaction) MarshalBinary() ([]byte, error) {
 	return marshallBinary(t.envelope, t.signatures)