remove CounterpartyHops function, add GetChannelConnection

CHANGELOG.md

@@ -45,13 +45,15 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (core) [\#629](https://github.com/cosmos/ibc-go/pull/629) Removes the GetProofSpecs from the ClientState interface. This function was previously unused by core IBC.
 * (transfer) [\#517](https://github.com/cosmos/ibc-go/pull/517) Separates the ICS 26 callback functions from `AppModule` into a new type `IBCModule` for ICS 20 transfer.
 * (modules/core/02-client) [\#536](https://github.com/cosmos/ibc-go/pull/536) GetSelfConsensusState return type changed from bool to error.
+* (channel) [\#644](https://github.com/cosmos/ibc-go/pull/644) Removes `CounterpartyHops` function from the ChannelKeeper.
 
 ### State Machine Breaking
 
 ### Improvements
 
 * [\#383](https://github.com/cosmos/ibc-go/pull/383) Adds helper functions for merging and splitting middleware versions from the underlying app version.
 * (modules/core/05-port) [\#288](https://github.com/cosmos/ibc-go/issues/288) Making the 05-port keeper function IsBound public. The IsBound function checks if the provided portID is already binded to a module.
+* (channel) [\#644](https://github.com/cosmos/ibc-go/pull/644) Adds `GetChannelConnection` to the ChannelKeeper. This function returns the connectionID and connection state associated with a channel. 
 
 ### Features
 

modules/apps/27-interchain-accounts/controller/keeper/handshake.go

@@ -105,24 +105,19 @@ func (k Keeper) OnChanCloseConfirm(
 // validateControllerPortParams asserts the provided connection sequence and counterparty connection sequence
 // match that of the associated connection stored in state
 func (k Keeper) validateControllerPortParams(ctx sdk.Context, channelID, portID string, connectionSeq, counterpartyConnectionSeq uint64) error {
-	channel, found := k.channelKeeper.GetChannel(ctx, portID, channelID)
-	if !found {
-		return sdkerrors.Wrapf(channeltypes.ErrChannelNotFound, "port ID %s channel ID %s", portID, channelID)
-	}
-
-	counterpartyHops, found := k.channelKeeper.CounterpartyHops(ctx, channel)
-	if !found {
-		return sdkerrors.Wrap(connectiontypes.ErrConnectionNotFound, channel.ConnectionHops[0])
+	connectionID, connection, err := k.channelKeeper.GetChannelConnection(ctx, portID, channelID)
+	if err != nil {
+		return err
 	}
 
-	connSeq, err := connectiontypes.ParseConnectionSequence(channel.ConnectionHops[0])
+	connSeq, err := connectiontypes.ParseConnectionSequence(connectionID)
 	if err != nil {
-		return sdkerrors.Wrapf(err, "failed to parse connection sequence %s", channel.ConnectionHops[0])
+		return sdkerrors.Wrapf(err, "failed to parse connection sequence %s", connectionID)
 	}
 
-	counterpartyConnSeq, err := connectiontypes.ParseConnectionSequence(counterpartyHops[0])
+	counterpartyConnSeq, err := connectiontypes.ParseConnectionSequence(connection.GetCounterparty().GetConnectionID())
 	if err != nil {
-		return sdkerrors.Wrapf(err, "failed to parse counterparty connection sequence %s", counterpartyHops[0])
+		return sdkerrors.Wrapf(err, "failed to parse counterparty connection sequence %s", connection.GetCounterparty().GetConnectionID())
 	}
 
 	if connSeq != connectionSeq {

modules/apps/27-interchain-accounts/host/keeper/handshake.go

@@ -105,24 +105,19 @@ func (k Keeper) OnChanCloseConfirm(
 // validateControllerPortParams asserts the provided connection sequence and counterparty connection sequence
 // match that of the associated connection stored in state
 func (k Keeper) validateControllerPortParams(ctx sdk.Context, channelID, portID string, connectionSeq, counterpartyConnectionSeq uint64) error {
-	channel, found := k.channelKeeper.GetChannel(ctx, portID, channelID)
-	if !found {
-		return sdkerrors.Wrapf(channeltypes.ErrChannelNotFound, "port ID %s channel ID %s", portID, channelID)
-	}
-
-	counterpartyHops, found := k.channelKeeper.CounterpartyHops(ctx, channel)
-	if !found {
-		return sdkerrors.Wrap(connectiontypes.ErrConnectionNotFound, channel.ConnectionHops[0])
+	connectionID, connection, err := k.channelKeeper.GetChannelConnection(ctx, portID, channelID)
+	if err != nil {
+		return err
 	}
 
-	connSeq, err := connectiontypes.ParseConnectionSequence(channel.ConnectionHops[0])
+	connSeq, err := connectiontypes.ParseConnectionSequence(connectionID)
 	if err != nil {
-		return sdkerrors.Wrapf(err, "failed to parse connection sequence %s", channel.ConnectionHops[0])
+		return sdkerrors.Wrapf(err, "failed to parse connection sequence %s", connectionID)
 	}
 
-	counterpartyConnSeq, err := connectiontypes.ParseConnectionSequence(counterpartyHops[0])
+	counterpartyConnSeq, err := connectiontypes.ParseConnectionSequence(connection.GetCounterparty().GetConnectionID())
 	if err != nil {
-		return sdkerrors.Wrapf(err, "failed to parse counterparty connection sequence %s", counterpartyHops[0])
+		return sdkerrors.Wrapf(err, "failed to parse counterparty connection sequence %s", connection.GetCounterparty().GetConnectionID())
 	}
 
 	if connSeq != connectionSeq {

modules/apps/27-interchain-accounts/types/expected_keepers.go

@@ -27,7 +27,7 @@ type ICS4Wrapper interface {
 type ChannelKeeper interface {
 	GetChannel(ctx sdk.Context, srcPort, srcChan string) (channel channeltypes.Channel, found bool)
 	GetNextSequenceSend(ctx sdk.Context, portID, channelID string) (uint64, bool)
-	CounterpartyHops(ctx sdk.Context, channel channeltypes.Channel) ([]string, bool)
+	GetChannelConnection(ctx sdk.Context, portID, channelID string) (string, ibcexported.ConnectionI, error)
 }
 
 // PortKeeper defines the expected IBC port keeper

modules/core/04-channel/keeper/handshake.go

@@ -5,34 +5,14 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 	capabilitytypes "github.com/cosmos/cosmos-sdk/x/capability/types"
+
 	connectiontypes "github.com/cosmos/ibc-go/v3/modules/core/03-connection/types"
 	"github.com/cosmos/ibc-go/v3/modules/core/04-channel/types"
 	porttypes "github.com/cosmos/ibc-go/v3/modules/core/05-port/types"
 	host "github.com/cosmos/ibc-go/v3/modules/core/24-host"
 	"github.com/cosmos/ibc-go/v3/modules/core/exported"
 )
 
-// CounterpartyHops returns the connection hops of the counterparty channel.
-// The counterparty hops are stored in the inverse order as the channel's.
-// NOTE: Since connectionHops only supports single connection channels for now,
-// this function requires that connection hops only contain a single connection id
-func (k Keeper) CounterpartyHops(ctx sdk.Context, ch types.Channel) ([]string, bool) {
-	// Return empty array if connection hops is more than one
-	// ConnectionHops length should be verified earlier
-	if len(ch.ConnectionHops) != 1 {
-		return []string{}, false
-	}
-	counterpartyHops := make([]string, 1)
-	hop := ch.ConnectionHops[0]
-	conn, found := k.connectionKeeper.GetConnection(ctx, hop)
-	if !found {
-		return []string{}, false
-	}
-
-	counterpartyHops[0] = conn.GetCounterparty().GetConnectionID()
-	return counterpartyHops, true
-}
-
 // ChanOpenInit is called by a module to initiate a channel opening handshake with
 // a module on another chain. The counterparty channel identifier is validated to be
 // empty in msg validation.
@@ -127,6 +107,11 @@ func (k Keeper) ChanOpenTry(
 
 	channelID := previousChannelID
 
+	// connection hops only supports a single connection
+	if len(connectionHops) != 1 {
+		return "", nil, sdkerrors.Wrapf(types.ErrTooManyConnectionHops, "expected 1, got %d", len(connectionHops))
+	}
+
 	// empty channel identifier indicates continuing a previous channel handshake
 	if previousChannelID != "" {
 		// channel identifier and connection hop length checked on msg.ValidateBasic()
@@ -139,7 +124,7 @@ func (k Keeper) ChanOpenTry(
 		if !(previousChannel.Ordering == order &&
 			previousChannel.Counterparty.PortId == counterparty.PortId &&
 			previousChannel.Counterparty.ChannelId == "" &&
-			previousChannel.ConnectionHops[0] == connectionHops[0] &&
+			previousChannel.ConnectionHops[0] == connectionHops[0] && // ChanOpenInit will only set a single connection hop
 			previousChannel.Version == version) {
 			return "", nil, sdkerrors.Wrap(types.ErrInvalidChannel, "channel fields mismatch previous channel fields")
 		}
@@ -189,12 +174,7 @@ func (k Keeper) ChanOpenTry(
 	// NOTE: this step has been switched with the one below to reverse the connection
 	// hops
 	channel := types.NewChannel(types.TRYOPEN, order, counterparty, connectionHops, version)
-
-	counterpartyHops, found := k.CounterpartyHops(ctx, channel)
-	if !found {
-		// should not reach here, connectionEnd was able to be retrieved above
-		panic("cannot find connection")
-	}
+	counterpartyHops := []string{connectionEnd.GetCounterparty().GetConnectionID()}
 
 	// expectedCounterpaty is the counterparty of the counterparty's channel end
 	// (i.e self)
@@ -297,11 +277,7 @@ func (k Keeper) ChanOpenAck(
 		)
 	}
 
-	counterpartyHops, found := k.CounterpartyHops(ctx, channel)
-	if !found {
-		// should not reach here, connectionEnd was able to be retrieved above
-		panic("cannot find connection")
-	}
+	counterpartyHops := []string{connectionEnd.GetCounterparty().GetConnectionID()}
 
 	// counterparty of the counterparty channel end (i.e self)
 	expectedCounterparty := types.NewCounterparty(portID, channelID)
@@ -381,11 +357,7 @@ func (k Keeper) ChanOpenConfirm(
 		)
 	}
 
-	counterpartyHops, found := k.CounterpartyHops(ctx, channel)
-	if !found {
-		// Should not reach here, connectionEnd was able to be retrieved above
-		panic("cannot find connection")
-	}
+	counterpartyHops := []string{connectionEnd.GetCounterparty().GetConnectionID()}
 
 	counterparty := types.NewCounterparty(portID, channelID)
 	expectedChannel := types.NewChannel(
@@ -519,11 +491,7 @@ func (k Keeper) ChanCloseConfirm(
 		)
 	}
 
-	counterpartyHops, found := k.CounterpartyHops(ctx, channel)
-	if !found {
-		// Should not reach here, connectionEnd was able to be retrieved above
-		panic("cannot find connection")
-	}
+	counterpartyHops := []string{connectionEnd.GetCounterparty().GetConnectionID()}
 
 	counterparty := types.NewCounterparty(portID, channelID)
 	expectedChannel := types.NewChannel(

modules/core/04-channel/keeper/keeper.go

@@ -403,6 +403,23 @@ func (k Keeper) GetChannelClientState(ctx sdk.Context, portID, channelID string)
 	return connection.ClientId, clientState, nil
 }
 
+// GetChannelConnection returns the connection ID and state associated with the given port and channel identifier.
+func (k Keeper) GetChannelConnection(ctx sdk.Context, portID, channelID string) (string, exported.ConnectionI, error) {
+	channel, found := k.GetChannel(ctx, portID, channelID)
+	if !found {
+		return "", nil, sdkerrors.Wrapf(types.ErrChannelNotFound, "port-id: %s, channel-id: %s", portID, channelID)
+	}
+
+	connectionID := channel.ConnectionHops[0]
+
+	connection, found := k.connectionKeeper.GetConnection(ctx, connectionID)
+	if !found {
+		return "", nil, sdkerrors.Wrapf(connectiontypes.ErrConnectionNotFound, "connection-id: %s", connectionID)
+	}
+
+	return connectionID, connection, nil
+}
+
 // LookupModuleByChannel will return the IBCModule along with the capability associated with a given channel defined by its portID and channelID
 func (k Keeper) LookupModuleByChannel(ctx sdk.Context, portID, channelID string) (string, *capabilitytypes.Capability, error) {
 	modules, cap, err := k.scopedKeeper.LookupModules(ctx, host.ChannelCapabilityPath(portID, channelID))

modules/core/04-channel/keeper/timeout.go

@@ -227,11 +227,7 @@ func (k Keeper) TimeoutOnClose(
 		return sdkerrors.Wrapf(types.ErrInvalidPacket, "packet commitment bytes are not equal: got (%v), expected (%v)", commitment, packetCommitment)
 	}
 
-	counterpartyHops, found := k.CounterpartyHops(ctx, channel)
-	if !found {
-		// Should not reach here, connectionEnd was able to be retrieved above
-		panic("cannot find connection")
-	}
+	counterpartyHops := []string{connectionEnd.GetCounterparty().GetConnectionID()}
 
 	counterparty := types.NewCounterparty(packet.GetSourcePort(), packet.GetSourceChannel())
 	expectedChannel := types.NewChannel(