(feat) Add possibility to transfer entire balance.

CHANGELOG.md

@@ -80,6 +80,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 * (apps/transfer) [\#6492](https://github.com/cosmos/ibc-go/pull/6492) Added new `Tokens` field to `MsgTransfer` to enable sending of multiple denoms, and deprecated the `Token` field.
 * (apps/transfer) [\#6693](https://github.com/cosmos/ibc-go/pull/6693) Added new `Forwarding` field to `MsgTransfer` to enable forwarding tokens through multiple intermediary chains with a single transaction. This also enables automatic unwinding of tokens to their native chain. `x/authz` support for transfer allows granters to specify a set of possible forwarding hops that are allowed for grantees.
+* (apps/transfer) [\#6877](https://github.com/cosmos/ibc-go/pull/6877) Added the possibility to transfer the entire balance of a particular denomination by using as amount a value equal to [`UnboundedSpendLimit`](https://github.com/cosmos/ibc-go/blob/715f00eef8727da41db25fdd4763b709bdbba07e/modules/apps/transfer/types/transfer_authorization.go#L253-L255)
 
 ### Bug Fixes
 

e2e/tests/transfer/base_test.go

@@ -553,3 +553,77 @@ func (s *TransferTestSuite) TestMsgTransfer_WithMemo() {
 		s.Require().Equal(testvalues.IBCTransferAmount, actualBalance.Int64())
 	})
 }
+
+// TestMsgTransfer_EntireBalance tests that it is possible to transfer the entire balance
+// of a given denom by using types.UnboundedSpendLimit as the amount.
+func (s *TransferTestSuite) TestMsgTransfer_EntireBalance() {
+	t := s.T()
+	ctx := context.TODO()
+
+	testName := t.Name()
+	t.Parallel()
+	relayer, channelA := s.CreateTransferPath(testName)
+
+	chainA, chainB := s.GetChains()
+
+	chainADenom := chainA.Config().Denom
+
+	chainAWallet := s.CreateUserOnChainA(ctx, testvalues.StartingTokenAmount)
+	chainAAddress := chainAWallet.FormattedAddress()
+
+	chainBWallet := s.CreateUserOnChainB(ctx, testvalues.StartingTokenAmount)
+	chainBAddress := chainBWallet.FormattedAddress()
+
+	coinFromA := testvalues.DefaultTransferAmount(chainADenom)
+
+	s.Require().NoError(test.WaitForBlocks(ctx, 1, chainA, chainB), "failed to wait for blocks")
+
+	t.Run("IBC token transfer from chainA to chainB", func(t *testing.T) {
+		transferTxResp := s.Transfer(ctx, chainA, chainAWallet, channelA.PortID, channelA.ChannelID, sdk.NewCoins(coinFromA), chainAAddress, chainBAddress, s.GetTimeoutHeight(ctx, chainA), 0, "", nil)
+		s.AssertTxSuccess(transferTxResp)
+	})
+
+	t.Run("tokens are escrowed", func(t *testing.T) {
+		actualBalance, err := s.GetChainANativeBalance(ctx, chainAWallet)
+		s.Require().NoError(err)
+
+		s.Require().Equal(testvalues.StartingTokenAmount-coinFromA.Amount.Int64(), actualBalance)
+	})
+
+	t.Run("start relayer", func(t *testing.T) {
+		s.StartRelayer(relayer, testName)
+	})
+
+	chainBIBCToken := testsuite.GetIBCToken(chainADenom, channelA.Counterparty.PortID, channelA.Counterparty.ChannelID)
+
+	t.Run("packets relayed", func(t *testing.T) {
+		s.AssertPacketRelayed(ctx, chainA, channelA.PortID, channelA.ChannelID, 1)
+		actualBalance, err := query.Balance(ctx, chainB, chainBAddress, chainBIBCToken.IBCDenom())
+
+		s.Require().NoError(err)
+		s.Require().Equal(coinFromA.Amount.Int64(), actualBalance.Int64())
+
+		actualBalance, err = query.Balance(ctx, chainA, chainAAddress, chainADenom)
+
+		s.Require().NoError(err)
+		s.Require().Equal(testvalues.StartingTokenAmount-coinFromA.Amount.Int64(), actualBalance.Int64())
+	})
+
+	t.Run("send entire balance from B to A", func(t *testing.T) {
+		transferTxResp := s.Transfer(ctx, chainB, chainBWallet, channelA.Counterparty.PortID, channelA.Counterparty.ChannelID, sdk.NewCoins(sdk.NewCoin(chainBIBCToken.IBCDenom(), transfertypes.UnboundedSpendLimit())), chainBAddress, chainAAddress, s.GetTimeoutHeight(ctx, chainB), 0, "", nil)
+		s.AssertTxSuccess(transferTxResp)
+	})
+
+	t.Run("packets relayed", func(t *testing.T) {
+		s.AssertPacketRelayed(ctx, chainA, channelA.PortID, channelA.ChannelID, 1)
+		actualBalance, err := query.Balance(ctx, chainA, chainAAddress, chainADenom)
+
+		s.Require().NoError(err)
+		s.Require().Equal(testvalues.StartingTokenAmount, actualBalance.Int64())
+
+		actualBalance, err = query.Balance(ctx, chainB, chainBAddress, chainBIBCToken.IBCDenom())
+
+		s.Require().NoError(err)
+		s.Require().Zero(actualBalance.Int64())
+	})
+}

modules/apps/transfer/keeper/relay.go

@@ -98,6 +98,11 @@ func (k Keeper) sendTransfer(
 	tokens := make([]types.Token, 0, len(coins))
 
 	for _, coin := range coins {
+		// Using types.UnboundedSpendLimit allows us to send the entire balance of a given denom.
+		if coin.Amount.Equal(types.UnboundedSpendLimit()) {
+			coin.Amount = k.bankKeeper.GetBalance(ctx, sender, coin.Denom).Amount
+		}
+
 		token, err := k.tokenFromCoin(ctx, coin)
 		if err != nil {
 			return 0, err

modules/apps/transfer/keeper/relay_test.go

@@ -113,6 +113,16 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 			},
 			nil,
 		},
+		{
+			"successful transfer of entire balance",
+			func() {
+				coins = sdk.NewCoins(sdk.NewCoin(coins[0].Denom, types.UnboundedSpendLimit()))
+				var ok bool
+				expEscrowAmounts[0], ok = sdkmath.NewIntFromString(ibctesting.DefaultChainAmount)
+				suite.Require().True(ok)
+			},
+			nil,
+		},
 		{
 			"failure: source channel not found",
 			func() {

testing/chain.go

@@ -45,6 +45,10 @@ type SenderAccount struct {
 	SenderAccount sdk.AccountI
 }
 
+const (
+	DefaultChainAmount = "10000000000000000000"
+)
+
 // TestChain is a testing struct that wraps a simapp with the last TM Header, the current ABCI
 // header and the validators of the TestChain. It also contains a field called ChainID. This
 // is the clientID that *other* chains use to refer to this TestChain. The SenderAccount
@@ -107,7 +111,7 @@ func NewTestChainWithValSet(tb testing.TB, coord *Coordinator, chainID string, v
 	for i := 0; i < MaxAccounts; i++ {
 		senderPrivKey := secp256k1.GenPrivKey()
 		acc := authtypes.NewBaseAccount(senderPrivKey.PubKey().Address().Bytes(), senderPrivKey.PubKey(), uint64(i), 0)
-		amount, ok := sdkmath.NewIntFromString("10000000000000000000")
+		amount, ok := sdkmath.NewIntFromString(DefaultChainAmount)
 		require.True(tb, ok)
 
 		// add sender account