txnbuild: enables multiple signatures (#1198)

This PR enables multiple signatures on a transaction in the new Go SDK. It also lets every `Operation` type have a different source account than its `Transaction`. These changes are intertwined. Without multiple signatures, every operation in a transaction must share the transaction's source account. Differing source accounts are the most common use case for multiple signatures, and they also test it with greatest completeness.

txnbuild/account_merge.go

@@ -8,7 +8,8 @@ import (
 // AccountMerge represents the Stellar merge account operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type AccountMerge struct {
-	Destination string
+	Destination   string
+	SourceAccount Account
 }
 
 // BuildXDR for AccountMerge returns a fully configured XDR Operation.
@@ -22,6 +23,10 @@ func (am *AccountMerge) BuildXDR() (xdr.Operation, error) {
 
 	opType := xdr.OperationTypeAccountMerge
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, am.SourceAccount)
+	return op, nil
 }

txnbuild/allow_trust.go

@@ -8,9 +8,10 @@ import (
 // AllowTrust represents the Stellar allow trust operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type AllowTrust struct {
-	Trustor   string
-	Type      Asset
-	Authorize bool
+	Trustor       string
+	Type          Asset
+	Authorize     bool
+	SourceAccount Account
 }
 
 // BuildXDR for AllowTrust returns a fully configured XDR Operation.
@@ -44,6 +45,10 @@ func (at *AllowTrust) BuildXDR() (xdr.Operation, error) {
 
 	opType := xdr.OperationTypeAllowTrust
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, at.SourceAccount)
+	return op, nil
 }

txnbuild/bump_sequence.go

@@ -8,14 +8,19 @@ import (
 // BumpSequence represents the Stellar bump sequence operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type BumpSequence struct {
-	BumpTo int64
+	BumpTo        int64
+	SourceAccount Account
 }
 
 // BuildXDR for BumpSequence returns a fully configured XDR Operation.
 func (bs *BumpSequence) BuildXDR() (xdr.Operation, error) {
 	opType := xdr.OperationTypeBumpSequence
 	xdrOp := xdr.BumpSequenceOp{BumpTo: xdr.SequenceNumber(bs.BumpTo)}
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, bs.SourceAccount)
+	return op, nil
 }

txnbuild/change_trust.go

@@ -9,8 +9,9 @@ import (
 // ChangeTrust represents the Stellar change trust operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type ChangeTrust struct {
-	Line  Asset
-	Limit string
+	Line          Asset
+	Limit         string
+	SourceAccount Account
 }
 
 // RemoveTrustlineOp returns a ChangeTrust operation to remove the trustline of the described asset,
@@ -43,6 +44,10 @@ func (ct *ChangeTrust) BuildXDR() (xdr.Operation, error) {
 		Limit: xdrLimit,
 	}
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, ct.SourceAccount)
+	return xdr.Operation{Body: body}, nil
 }

txnbuild/cmd/demo/operations/demo.go

@@ -301,7 +301,10 @@ func deleteTrustline(source *hProtocol.Account, asset txnbuild.Asset, signer Acc
 }
 
 func deleteOffer(source *hProtocol.Account, offerID int64, signer Account) (string, error) {
-	deleteOffer := txnbuild.DeleteOfferOp(offerID)
+	deleteOffer, err := txnbuild.DeleteOfferOp(offerID)
+	if err != nil {
+		return "", errors.Wrap(err, "building offer")
+	}
 
 	tx := txnbuild.Transaction{
 		SourceAccount: source,

txnbuild/create_account.go

@@ -9,8 +9,9 @@ import (
 // CreateAccount represents the Stellar create account operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type CreateAccount struct {
-	Destination string
-	Amount      string
+	Destination   string
+	Amount        string
+	SourceAccount Account
 }
 
 // BuildXDR for CreateAccount returns a fully configured XDR Operation.
@@ -29,6 +30,10 @@ func (ca *CreateAccount) BuildXDR() (xdr.Operation, error) {
 
 	opType := xdr.OperationTypeCreateAccount
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, ca.SourceAccount)
+	return op, nil
 }

txnbuild/create_passive_offer.go

@@ -10,10 +10,11 @@ import (
 // CreatePassiveSellOffer represents the Stellar create passive offer operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type CreatePassiveSellOffer struct {
-	Selling Asset
-	Buying  Asset
-	Amount  string
-	Price   string
+	Selling       Asset
+	Buying        Asset
+	Amount        string
+	Price         string
+	SourceAccount Account
 }
 
 // BuildXDR for CreatePassiveSellOffer returns a fully configured XDR Operation.
@@ -47,6 +48,10 @@ func (cpo *CreatePassiveSellOffer) BuildXDR() (xdr.Operation, error) {
 
 	opType := xdr.OperationTypeCreatePassiveSellOffer
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, cpo.SourceAccount)
+	return op, nil
 }

txnbuild/example_test.go

@@ -305,7 +305,8 @@ func ExampleManageSellOffer() {
 	buying := CreditAsset{"ABCD", "GAS4V4O2B7DW5T7IQRPEEVCRXMDZESKISR7DVIGKZQYYV3OSQ5SH5LVP"}
 	sellAmount := "100"
 	price := "0.01"
-	op := CreateOfferOp(selling, buying, sellAmount, price)
+	op, err := CreateOfferOp(selling, buying, sellAmount, price)
+	check(err)
 
 	tx := Transaction{
 		SourceAccount: &sourceAccount,
@@ -329,7 +330,8 @@ func ExampleManageSellOffer_deleteOffer() {
 	check(err)
 
 	offerID := int64(2921622)
-	op := DeleteOfferOp(offerID)
+	op, err := DeleteOfferOp(offerID)
+	check(err)
 
 	tx := Transaction{
 		SourceAccount: &sourceAccount,
@@ -357,7 +359,8 @@ func ExampleManageSellOffer_updateOffer() {
 	sellAmount := "50"
 	price := "0.02"
 	offerID := int64(2497628)
-	op := UpdateOfferOp(selling, buying, sellAmount, price, offerID)
+	op, err := UpdateOfferOp(selling, buying, sellAmount, price, offerID)
+	check(err)
 
 	tx := Transaction{
 		SourceAccount: &sourceAccount,

txnbuild/helpers_test.go

@@ -27,18 +27,14 @@ func newKeypair(seed string) *keypair.Full {
 	return myKeypair.(*keypair.Full)
 }
 
-func buildSignEncode(tx Transaction, kp *keypair.Full, t *testing.T) (txeBase64 string) {
-	var err error
-	err = tx.Build()
-	assert.NoError(t, err)
-
-	err = tx.Sign(kp)
-	assert.NoError(t, err)
+func buildSignEncode(t *testing.T, tx Transaction, kps ...*keypair.Full) string {
+	assert.NoError(t, tx.Build())
+	assert.NoError(t, tx.Sign(kps...))
 
-	txeBase64, err = tx.Base64()
+	txeBase64, err := tx.Base64()
 	assert.NoError(t, err)
 
-	return
+	return txeBase64
 }
 
 func check(err error) {

txnbuild/inflation.go

@@ -7,12 +7,18 @@ import (
 
 // Inflation represents the Stellar inflation operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
-type Inflation struct{}
+type Inflation struct {
+	SourceAccount Account
+}
 
 // BuildXDR for Inflation returns a fully configured XDR Operation.
 func (inf *Inflation) BuildXDR() (xdr.Operation, error) {
 	opType := xdr.OperationTypeInflation
 	body, err := xdr.NewOperationBody(opType, nil)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, inf.SourceAccount)
+	return op, nil
 }

txnbuild/manage_data.go

@@ -8,8 +8,9 @@ import (
 // ManageData represents the Stellar manage data operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type ManageData struct {
-	Name  string
-	Value []byte
+	Name          string
+	Value         []byte
+	SourceAccount Account
 }
 
 // BuildXDR for ManageData returns a fully configured XDR Operation.
@@ -26,6 +27,10 @@ func (md *ManageData) BuildXDR() (xdr.Operation, error) {
 
 	opType := xdr.OperationTypeManageData
 	body, err := xdr.NewOperationBody(opType, xdrOp)
-
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, md.SourceAccount)
+	return op, nil
 }

txnbuild/manage_offer.go

@@ -8,52 +8,78 @@ import (
 )
 
 //CreateOfferOp returns a ManageSellOffer operation to create a new offer, by
-// setting the OfferID to "0".
-func CreateOfferOp(selling, buying Asset, amount, price string) ManageSellOffer {
-	return ManageSellOffer{
+// setting the OfferID to "0". The sourceAccount is optional, and if not provided,
+// will be that of the surrounding transaction.
+func CreateOfferOp(selling, buying Asset, amount, price string, sourceAccount ...Account) (ManageSellOffer, error) {
+	if len(sourceAccount) > 1 {
+		return ManageSellOffer{}, errors.New("offer can't have multiple source accounts")
+	}
+	offer := ManageSellOffer{
 		Selling: selling,
 		Buying:  buying,
 		Amount:  amount,
 		Price:   price,
 		OfferID: 0,
 	}
+	if len(sourceAccount) == 1 {
+		offer.SourceAccount = sourceAccount[0]
+	}
+	return offer, nil
 }
 
-//UpdateOfferOp returns a ManageSellOffer operation to update an offer.
-func UpdateOfferOp(selling, buying Asset, amount, price string, offerID int64) ManageSellOffer {
-	return ManageSellOffer{
+// UpdateOfferOp returns a ManageSellOffer operation to update an offer.
+// The sourceAccount is optional, and if not provided, will be that of
+// the surrounding transaction.
+func UpdateOfferOp(selling, buying Asset, amount, price string, offerID int64, sourceAccount ...Account) (ManageSellOffer, error) {
+	if len(sourceAccount) > 1 {
+		return ManageSellOffer{}, errors.New("offer can't have multiple source accounts")
+	}
+	offer := ManageSellOffer{
 		Selling: selling,
 		Buying:  buying,
 		Amount:  amount,
 		Price:   price,
 		OfferID: offerID,
 	}
+	if len(sourceAccount) == 1 {
+		offer.SourceAccount = sourceAccount[0]
+	}
+	return offer, nil
 }
 
 //DeleteOfferOp returns a ManageSellOffer operation to delete an offer, by
-// setting the Amount to "0".
-func DeleteOfferOp(offerID int64) ManageSellOffer {
+// setting the Amount to "0". The sourceAccount is optional, and if not provided,
+// will be that of the surrounding transaction.
+func DeleteOfferOp(offerID int64, sourceAccount ...Account) (ManageSellOffer, error) {
 	// It turns out Stellar core doesn't care about any of these fields except the amount.
 	// However, Horizon will reject ManageSellOffer if it is missing fields.
 	// Horizon will also reject if Buying == Selling.
 	// Therefore unfortunately we have to make up some dummy values here.
-	return ManageSellOffer{
+	if len(sourceAccount) > 1 {
+		return ManageSellOffer{}, errors.New("offer can't have multiple source accounts")
+	}
+	offer := ManageSellOffer{
 		Selling: NativeAsset{},
 		Buying:  CreditAsset{Code: "FAKE", Issuer: "GBAQPADEYSKYMYXTMASBUIS5JI3LMOAWSTM2CHGDBJ3QDDPNCSO3DVAA"},
 		Amount:  "0",
 		Price:   "1",
 		OfferID: offerID,
 	}
+	if len(sourceAccount) == 1 {
+		offer.SourceAccount = sourceAccount[0]
+	}
+	return offer, nil
 }
 
 // ManageSellOffer represents the Stellar manage offer operation. See
 // https://www.stellar.org/developers/guides/concepts/list-of-operations.html
 type ManageSellOffer struct {
-	Selling Asset
-	Buying  Asset
-	Amount  string
-	Price   string
-	OfferID int64
+	Selling       Asset
+	Buying        Asset
+	Amount        string
+	Price         string
+	OfferID       int64
+	SourceAccount Account
 }
 
 // BuildXDR for ManageSellOffer returns a fully configured XDR Operation.
@@ -87,6 +113,11 @@ func (mo *ManageSellOffer) BuildXDR() (xdr.Operation, error) {
 		OfferId: xdr.Int64(mo.OfferID),
 	}
 	body, err := xdr.NewOperationBody(opType, xdrOp)
+	if err != nil {
+		return xdr.Operation{}, errors.Wrap(err, "failed to build XDR OperationBody")
+	}
 
-	return xdr.Operation{Body: body}, errors.Wrap(err, "failed to build XDR OperationBody")
+	op := xdr.Operation{Body: body}
+	SetOpSourceAccount(&op, mo.SourceAccount)
+	return op, nil
 }

txnbuild/operation.go

@@ -8,3 +8,13 @@ import (
 type Operation interface {
 	BuildXDR() (xdr.Operation, error)
 }
+
+// SetOpSourceAccount sets the source account ID on an Operation.
+func SetOpSourceAccount(op *xdr.Operation, sourceAccount Account) {
+	if sourceAccount == nil {
+		return
+	}
+	var opSourceAccountID xdr.AccountId
+	opSourceAccountID.SetAddress(sourceAccount.GetAccountID())
+	op.SourceAccount = &opSourceAccountID
+}