txnbuild: Use xdr.Price to represent prices in txnbuild instead of strings.

price/main.go

@@ -38,6 +38,15 @@ func Parse(v string) (xdr.Price, error) {
 	return continuedFraction(v)
 }
 
+// MustParse is like Parse except that it panics on errors.
+func MustParse(v string) xdr.Price {
+	result, err := Parse(v)
+	if err != nil {
+		panic(err)
+	}
+	return result
+}
+
 // continuedFraction calculates and returns the best rational approximation of
 // the given real number.
 func continuedFraction(price string) (xdrPrice xdr.Price, err error) {

services/horizon/internal/integration/clawback_test.go

@@ -93,7 +93,7 @@ func TestHappyClawbackAccountSellingLiabilities(t *testing.T) {
 		Buying:        txnbuild.NativeAsset{},
 		Selling:       asset,
 		Amount:        "5",
-		Price:         "1",
+		Price:         xdr.Price{1, 1},
 		SourceAccount: fromAccount.GetAccountID(),
 	})
 	tt.True(submissionResp.Successful)
@@ -148,7 +148,7 @@ func TestSadClawbackAccountSufficientFundsSellingLiabilities(t *testing.T) {
 		Buying:        txnbuild.NativeAsset{},
 		Selling:       asset,
 		Amount:        "5",
-		Price:         "1",
+		Price:         xdr.Price{1, 1},
 		SourceAccount: fromAccount.GetAccountID(),
 	})
 

services/horizon/internal/integration/db_test.go

@@ -79,8 +79,8 @@ func generateLiquidityPoolOps(itest *integration.Test, tt *assert.Assertions) (l
 			LiquidityPoolID: [32]byte(poolID),
 			MaxAmountA:      "400",
 			MaxAmountB:      "777",
-			MinPrice:        "0.5",
-			MaxPrice:        "2",
+			MinPrice:        xdr.Price{1, 2},
+			MaxPrice:        xdr.Price{2, 1},
 		},
 	)
 

services/horizon/internal/integration/liquidity_pool_test.go

@@ -88,8 +88,8 @@ func TestLiquidityPoolHappyPath(t *testing.T) {
 			LiquidityPoolID: [32]byte(poolID),
 			MaxAmountA:      "400",
 			MaxAmountB:      "777",
-			MinPrice:        "0.5",
-			MaxPrice:        "2",
+			MinPrice:        xdr.Price{1, 2},
+			MaxPrice:        xdr.Price{2, 1},
 		},
 	)
 
@@ -475,8 +475,8 @@ func TestLiquidityPoolRevoke(t *testing.T) {
 			LiquidityPoolID: [32]byte(poolID),
 			MaxAmountA:      "400",
 			MaxAmountB:      "777",
-			MinPrice:        "0.5",
-			MaxPrice:        "2",
+			MinPrice:        xdr.Price{1, 2},
+			MaxPrice:        xdr.Price{2, 1},
 		},
 		&txnbuild.SetTrustLineFlags{
 			SourceAccount: master.Address(),
@@ -667,8 +667,8 @@ func TestLiquidityPoolFailedDepositAndWithdraw(t *testing.T) {
 			LiquidityPoolID: nonExistentPoolID,
 			MaxAmountA:      "400",
 			MaxAmountB:      "777",
-			MinPrice:        "0.5",
-			MaxPrice:        "2",
+			MinPrice:        xdr.Price{1, 2},
+			MaxPrice:        xdr.Price{2, 1},
 		},
 	)
 	_, err = itest.Client().SubmitTransaction(tx)

services/horizon/internal/integration/muxed_operations_test.go

@@ -50,15 +50,15 @@ func TestMuxedOperations(t *testing.T) {
 			Selling:       txnbuild.NativeAsset{},
 			Buying:        txnbuild.CreditAsset{"ABCD", master.Address()},
 			Amount:        "3",
-			Price:         "1",
+			Price:         xdr.Price{1, 1},
 		},
 		// This will generate a trade effect:
 		&txnbuild.ManageSellOffer{
 			SourceAccount: masterMuxed.Address(),
 			Selling:       txnbuild.CreditAsset{"ABCD", master.Address()},
 			Buying:        txnbuild.NativeAsset{},
 			Amount:        "3",
-			Price:         "1",
+			Price:         xdr.Price{1, 1},
 		},
 		&txnbuild.ManageData{
 			SourceAccount: sponsoredMuxed.Address(),

services/horizon/internal/integration/sponsorship_test.go

@@ -516,7 +516,7 @@ func TestSponsorships(t *testing.T) {
 				Selling:       txnbuild.NativeAsset{},
 				Buying:        asset,
 				Amount:        "3",
-				Price:         "1",
+				Price:         xdr.Price{1, 1},
 			})
 
 		signers := []*keypair.Full{sponsorPair, newAccountPair}

services/horizon/internal/integration/state_verifier_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/stellar/go/services/horizon/internal/db2/history"
 	"github.com/stellar/go/services/horizon/internal/test/integration"
 	"github.com/stellar/go/txnbuild"
+	"github.com/stellar/go/xdr"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -63,7 +64,7 @@ func TestStateVerifier(t *testing.T) {
 			Selling:       txnbuild.NativeAsset{},
 			Buying:        txnbuild.CreditAsset{"ABCD", master.Address()},
 			Amount:        "3",
-			Price:         "1",
+			Price:         xdr.Price{1, 1},
 		},
 		&txnbuild.ManageData{
 			SourceAccount: sponsoredSource.AccountID,

txnbuild/create_passive_offer.go

@@ -12,8 +12,7 @@ type CreatePassiveSellOffer struct {
 	Selling       Asset
 	Buying        Asset
 	Amount        string
-	Price         string
-	price         price
+	Price         xdr.Price
 	SourceAccount string
 }
 
@@ -34,15 +33,11 @@ func (cpo *CreatePassiveSellOffer) BuildXDR(withMuxedAccounts bool) (xdr.Operati
 		return xdr.Operation{}, errors.Wrap(err, "failed to parse 'Amount'")
 	}
 
-	if err = cpo.price.parse(cpo.Price); err != nil {
-		return xdr.Operation{}, errors.Wrap(err, "failed to parse 'Price'")
-	}
-
 	xdrOp := xdr.CreatePassiveSellOfferOp{
 		Selling: xdrSelling,
 		Buying:  xdrBuying,
 		Amount:  xdrAmount,
-		Price:   cpo.price.toXDR(),
+		Price:   cpo.Price,
 	}
 
 	opType := xdr.OperationTypeCreatePassiveSellOffer
@@ -68,10 +63,7 @@ func (cpo *CreatePassiveSellOffer) FromXDR(xdrOp xdr.Operation, withMuxedAccount
 
 	cpo.SourceAccount = accountFromXDR(xdrOp.SourceAccount, withMuxedAccounts)
 	cpo.Amount = amount.String(result.Amount)
-	if result.Price != (xdr.Price{}) {
-		cpo.price.fromXDR(result.Price)
-		cpo.Price = cpo.price.string()
-	}
+	cpo.Price = result.Price
 	buyingAsset, err := assetFromXDR(result.Buying)
 	if err != nil {
 		return errors.Wrap(err, "error parsing buying_asset in create_passive_sell_offer operation")

txnbuild/create_passive_offer_test.go

@@ -15,7 +15,7 @@ func TestCreatePassiveSellOfferValidateBuyingAsset(t *testing.T) {
 		Selling: NativeAsset{},
 		Buying:  CreditAsset{"ABCD", ""},
 		Amount:  "10",
-		Price:   "1.0",
+		Price:   xdr.Price{1, 1},
 	}
 
 	_, err := NewTransaction(
@@ -42,7 +42,7 @@ func TestCreatePassiveSellOfferValidateSellingAsset(t *testing.T) {
 		Selling: CreditAsset{"ABCD0123456789", kp0.Address()},
 		Buying:  NativeAsset{},
 		Amount:  "10",
-		Price:   "1.0",
+		Price:   xdr.Price{1, 1},
 	}
 
 	_, err := NewTransaction(
@@ -69,7 +69,7 @@ func TestCreatePassiveSellOfferValidateAmount(t *testing.T) {
 		Selling: CreditAsset{"ABCD", kp0.Address()},
 		Buying:  NativeAsset{},
 		Amount:  "-3",
-		Price:   "1.0",
+		Price:   xdr.Price{1, 1},
 	}
 
 	_, err := NewTransaction(
@@ -96,7 +96,7 @@ func TestCreatePassiveSellOfferValidatePrice(t *testing.T) {
 		Selling: CreditAsset{"ABCD", kp0.Address()},
 		Buying:  NativeAsset{},
 		Amount:  "3",
-		Price:   "-1.0",
+		Price:   xdr.Price{-1, 0},
 	}
 
 	_, err := NewTransaction(
@@ -109,7 +109,7 @@ func TestCreatePassiveSellOfferValidatePrice(t *testing.T) {
 		},
 	)
 	if assert.Error(t, err) {
-		expected := `validation failed for *txnbuild.CreatePassiveSellOffer operation: Field: Price, Error: amount can not be negative`
+		expected := `validation failed for *txnbuild.CreatePassiveSellOffer operation: Field: Price, Error: price denominator cannot be 0: -1/0`
 		assert.Contains(t, err.Error(), expected)
 	}
 }
@@ -121,19 +121,16 @@ func TestCreatePassiveSellOfferPrice(t *testing.T) {
 		Selling:       CreditAsset{"ABCD", kp0.Address()},
 		Buying:        NativeAsset{},
 		Amount:        "1",
-		Price:         "0.000000001",
+		Price:         xdr.Price{1, 1000000000},
 		SourceAccount: kp0.Address(),
 	}
 
 	xdrOp, err := offer.BuildXDR(false)
 	assert.NoError(t, err)
 	expectedPrice := xdr.Price{N: 1, D: 1000000000}
 	assert.Equal(t, expectedPrice, xdrOp.Body.CreatePassiveSellOfferOp.Price)
-	assert.Equal(t, offer.Price, offer.price.string())
-	assert.Equal(t, expectedPrice, offer.price.toXDR())
 
 	parsed := CreatePassiveSellOffer{}
 	assert.NoError(t, parsed.FromXDR(xdrOp, false))
 	assert.Equal(t, offer.Price, parsed.Price)
-	assert.Equal(t, offer.price, parsed.price)
 }

txnbuild/example_test.go

@@ -2,6 +2,8 @@ package txnbuild
 
 import (
 	"fmt"
+	"github.com/stellar/go/price"
+	"github.com/stellar/go/xdr"
 	"time"
 
 	"github.com/stellar/go/keypair"
@@ -429,8 +431,7 @@ func ExampleManageSellOffer() {
 	selling := NativeAsset{}
 	buying := CreditAsset{"ABCD", "GAS4V4O2B7DW5T7IQRPEEVCRXMDZESKISR7DVIGKZQYYV3OSQ5SH5LVP"}
 	sellAmount := "100"
-	price := "0.01"
-	op, err := CreateOfferOp(selling, buying, sellAmount, price)
+	op, err := CreateOfferOp(selling, buying, sellAmount, price.MustParse("0.01"))
 	check(err)
 
 	tx, err := NewTransaction(
@@ -496,9 +497,8 @@ func ExampleManageSellOffer_updateOffer() {
 	selling := NativeAsset{}
 	buying := CreditAsset{"ABCD", "GAS4V4O2B7DW5T7IQRPEEVCRXMDZESKISR7DVIGKZQYYV3OSQ5SH5LVP"}
 	sellAmount := "50"
-	price := "0.02"
 	offerID := int64(2497628)
-	op, err := UpdateOfferOp(selling, buying, sellAmount, price, offerID)
+	op, err := UpdateOfferOp(selling, buying, sellAmount, price.MustParse("0.02"), offerID)
 	check(err)
 
 	tx, err := NewTransaction(
@@ -533,7 +533,7 @@ func ExampleCreatePassiveSellOffer() {
 		Selling: NativeAsset{},
 		Buying:  CreditAsset{"ABCD", "GAS4V4O2B7DW5T7IQRPEEVCRXMDZESKISR7DVIGKZQYYV3OSQ5SH5LVP"},
 		Amount:  "10",
-		Price:   "1.0",
+		Price:   xdr.Price{1, 1},
 	}
 
 	tx, err := NewTransaction(
@@ -682,7 +682,7 @@ func ExampleManageBuyOffer() {
 		Selling: NativeAsset{},
 		Buying:  CreditAsset{"ABCD", "GDQNY3PBOJOKYZSRMK2S7LHHGWZIUISD4QORETLMXEWXBI7KFZZMKTL3"},
 		Amount:  "100",
-		Price:   "0.01",
+		Price:   price.MustParse("0.01"),
 		OfferID: 0,
 	}
 
@@ -1040,8 +1040,8 @@ func ExampleLiquidityPoolDeposit() {
 			LiquidityPoolID: poolId,
 			MaxAmountA:      "0.1000000",
 			MaxAmountB:      "0.1000000",
-			MinPrice:        "0.1000000",
-			MaxPrice:        "0.1000000",
+			MinPrice:        price.MustParse("0.1000000"),
+			MaxPrice:        price.MustParse("0.1000000"),
 		},
 	}
 

txnbuild/helpers.go

@@ -84,6 +84,19 @@ func validateAmount(n interface{}) error {
 	return nil
 }
 
+func validatePrice(p xdr.Price) error {
+	if p.N == 0 {
+		return errors.Errorf("price cannot be 0: %d/%d", p.N, p.D)
+	}
+	if p.D == 0 {
+		return errors.Errorf("price denominator cannot be 0: %d/%d", p.N, p.D)
+	}
+	if p.N < 0 || p.D < 0 {
+		return errors.Errorf("price cannot be negative: %d/%d", p.N, p.D)
+	}
+	return nil
+}
+
 // validateAssetCode checks if the provided asset is valid as an asset code.
 // It returns an error if the asset is invalid.
 // The asset must be non native (XLM) with a valid asset code.
@@ -141,7 +154,7 @@ func validateChangeTrustAsset(asset ChangeTrustAsset) error {
 // validatePassiveOffer checks if the fields of a CreatePassiveOffer struct are valid.
 // It checks that the buying and selling assets are valid stellar assets, and that amount and price are valid.
 // It returns an error if any field is invalid.
-func validatePassiveOffer(buying, selling Asset, offerAmount, price string) error {
+func validatePassiveOffer(buying, selling Asset, offerAmount string, price xdr.Price) error {
 	// Note: see discussion on how this can be improved:
 	// https://github.com/stellar/go/pull/1707#discussion_r321508440
 	err := validateStellarAsset(buying)
@@ -159,7 +172,7 @@ func validatePassiveOffer(buying, selling Asset, offerAmount, price string) erro
 		return NewValidationError("Amount", err.Error())
 	}
 
-	err = validateAmount(price)
+	err = validatePrice(price)
 	if err != nil {
 		return NewValidationError("Price", err.Error())
 	}
@@ -170,7 +183,7 @@ func validatePassiveOffer(buying, selling Asset, offerAmount, price string) erro
 // validateOffer checks if the fields of ManageBuyOffer or ManageSellOffer struct are valid.
 // It checks that the buying and selling assets are valid stellar assets, and that amount, price and offerID
 // are valid. It returns an error if any field is invalid.
-func validateOffer(buying, selling Asset, offerAmount, price string, offerID int64) error {
+func validateOffer(buying, selling Asset, offerAmount string, price xdr.Price, offerID int64) error {
 	err := validatePassiveOffer(buying, selling, offerAmount, price)
 	if err != nil {
 		return err

txnbuild/helpers_test.go

@@ -268,7 +268,7 @@ func TestValidatePassiveOfferInvalidAmount(t *testing.T) {
 	cpo := CreatePassiveSellOffer{
 		Buying:  buying,
 		Selling: selling,
-		Price:   "1",
+		Price:   xdr.Price{1, 1},
 		Amount:  "-1",
 	}
 	err := validatePassiveOffer(cpo.Buying, cpo.Selling, cpo.Amount, cpo.Price)
@@ -284,12 +284,12 @@ func TestValidatePassiveOfferInvalidPrice(t *testing.T) {
 	cpo := CreatePassiveSellOffer{
 		Buying:  buying,
 		Selling: selling,
-		Price:   "-1",
+		Price:   xdr.Price{-1, 1},
 		Amount:  "10",
 	}
 	err := validatePassiveOffer(cpo.Buying, cpo.Selling, cpo.Amount, cpo.Price)
 	assert.Error(t, err)
-	expectedErrMsg := "Field: Price, Error: amount can not be negative"
+	expectedErrMsg := "Field: Price, Error: price cannot be negative: -1/1"
 	require.EqualError(t, err, expectedErrMsg, "valid price is required")
 }
 
@@ -299,7 +299,7 @@ func TestValidatePassiveOfferInvalidAsset(t *testing.T) {
 	cpo := CreatePassiveSellOffer{
 		Buying:  buying,
 		Selling: selling,
-		Price:   "1",
+		Price:   xdr.Price{1, 1},
 		Amount:  "10",
 	}
 	err := validatePassiveOffer(cpo.Buying, cpo.Selling, cpo.Amount, cpo.Price)
@@ -313,7 +313,7 @@ func TestValidatePassiveOfferInvalidAsset(t *testing.T) {
 	cpo1 := CreatePassiveSellOffer{
 		Buying:  buying1,
 		Selling: selling1,
-		Price:   "1",
+		Price:   xdr.Price{1, 1},
 		Amount:  "10",
 	}
 	err = validatePassiveOffer(cpo1.Buying, cpo1.Selling, cpo1.Amount, cpo1.Price)
@@ -329,7 +329,7 @@ func TestValidateOfferManageBuyOffer(t *testing.T) {
 	mbo := ManageBuyOffer{
 		Buying:  buying,
 		Selling: selling,
-		Price:   "1",
+		Price:   xdr.Price{1, 1},
 		Amount:  "10",
 		OfferID: -1,
 	}
@@ -346,7 +346,7 @@ func TestValidateOfferManageSellOffer(t *testing.T) {
 	mso := ManageSellOffer{
 		Buying:  buying,
 		Selling: selling,
-		Price:   "1",
+		Price:   xdr.Price{1, 1},
 		Amount:  "10",
 		OfferID: -1,
 	}