feat: Add GetAppVersion to ICS4Wrapper

CHANGELOG.md

@@ -63,6 +63,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (middleware) [\#1022](https://github.com/cosmos/ibc-go/pull/1022) Add `GetUnwrappedChannelVersion` to the ICS4Wrapper interface. This function should be used by IBC applications to obtain their own version since the version set in the channel structure may be wrapped many times by middleware. 
 * (testing) [\#942](https://github.com/cosmos/ibc-go/pull/942) `NewTestChain` will create 4 validators in validator set by default. A new constructor function `NewTestChainWithValSet` is provided for test writers who want custom control over the validator set of test chains.
 * (testing) [\#904](https://github.com/cosmos/ibc-go/pull/904) Add `ParsePacketFromEvents` function to the testing package. Useful when sending/relaying packets via the testing package.
 * (testing) [\#893](https://github.com/cosmos/ibc-go/pull/893) Support custom private keys for testing.

docs/ibc/middleware/develop.md

@@ -49,6 +49,7 @@ type Middleware interface {
 type ICS4Wrapper interface {
     SendPacket(ctx sdk.Context, chanCap *capabilitytypes.Capability, packet exported.Packet) error
     WriteAcknowledgement(ctx sdk.Context, chanCap *capabilitytypes.Capability, packet exported.Packet, ack []byte) error
+    GetChannelVersion(ctx sdk.Context, portID, channelID string) (string, bool) 
 }
 ```
 
@@ -239,4 +240,21 @@ func SendPacket(appPacket channeltypes.Packet) {
 
     return ics4Keeper.SendPacket(packet)
 }
+
+// middleware must unwrap the channel version so the underlying application 
+// which calls this function receives the version it constructed.
+func GetUnwrappedChannelVersion(ctx sdk.Context, portID, channelID string) (string, bool) {
+    version, found := ics4Keeper.GetChannelVersion(ctx, portID, channelID)
+    if !found {
+        return "", false
+    }
+
+    // unwrap channel version
+    metadata, err := Unmarshal(version)
+    if err != nil {
+        panic() 
+    }
+
+    return metadata.AppVersion, true
+}
 ```

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

@@ -86,6 +86,16 @@ func (k Keeper) SetChannel(ctx sdk.Context, portID, channelID string, channel ty
 	store.Set(host.ChannelKey(portID, channelID), bz)
 }
 
+// GetUnwrappedChannelVersion gets the version for the specified channel.
+func (k Keeper) GetUnwrappedChannelVersion(ctx sdk.Context, portID, channelID string) (string, bool) {
+	channel, found := k.GetChannel(ctx, portID, channelID)
+	if !found {
+		return "", false
+	}
+
+	return channel.Version, true
+}
+
 // GetNextChannelSequence gets the next channel sequence from the store.
 func (k Keeper) GetNextChannelSequence(ctx sdk.Context) uint64 {
 	store := ctx.KVStore(k.storeKey)

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

@@ -7,6 +7,7 @@ import (
 
 	"github.com/cosmos/ibc-go/v3/modules/core/04-channel/types"
 	ibctesting "github.com/cosmos/ibc-go/v3/testing"
+	ibcmock "github.com/cosmos/ibc-go/v3/testing/mock"
 )
 
 // KeeperTestSuite is a testing suite to test keeper functions.
@@ -62,6 +63,24 @@ func (suite *KeeperTestSuite) TestSetChannel() {
 	suite.Equal(expectedCounterparty, storedChannel.Counterparty)
 }
 
+func (suite *KeeperTestSuite) TestGetUnwrappedChannelVersion() {
+	// create client and connections on both chains
+	path := ibctesting.NewPath(suite.chainA, suite.chainB)
+	suite.coordinator.SetupConnections(path)
+
+	version, found := suite.chainA.App.GetIBCKeeper().ChannelKeeper.GetUnwrappedChannelVersion(suite.chainA.GetContext(), path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID)
+	suite.Require().False(found)
+	suite.Require().Empty(version)
+
+	// init channel
+	err := path.EndpointA.ChanOpenInit()
+	suite.NoError(err)
+
+	channelVersion, found := suite.chainA.App.GetIBCKeeper().ChannelKeeper.GetUnwrappedChannelVersion(suite.chainA.GetContext(), path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID)
+	suite.Require().True(found)
+	suite.Require().Equal(ibcmock.Version, channelVersion)
+}
+
 // TestGetAllChannels creates multiple channels on chain A through various connections
 // and tests their retrieval. 2 channels are on connA0 and 1 channel is on connA1
 func (suite KeeperTestSuite) TestGetAllChannels() {