refactor: RegisterInterchainAccount (cosmos#814)

## Description

closes: cosmos#802 

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

- [ ] Targeted PR against correct branch (see [CONTRIBUTING.md](https://github.com/cosmos/ibc-go/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
- [ ] Code follows the [module structure standards](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules/structure.md).
- [ ] Wrote unit and integration [tests](https://github.com/cosmos/ibc-go/blob/master/CONTRIBUTING.md#testing)
- [ ] Updated relevant documentation (`docs/`) or specification (`x/<module>/spec/`)
- [ ] Added relevant `godoc` [comments](https://blog.golang.org/godoc-documenting-go-code).
- [ ] Added a relevant changelog entry to the `Unreleased` section in `CHANGELOG.md`
- [ ] Re-reviewed `Files changed` in the Github PR explorer
- [ ] Review `Codecov Report` in the comment section below once CI passes

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

@@ -21,13 +21,20 @@ func (k Keeper) RegisterInterchainAccount(ctx sdk.Context, connectionID, owner s
 		return err
 	}
 
-	if k.portKeeper.IsBound(ctx, portID) {
-		return sdkerrors.Wrap(icatypes.ErrPortAlreadyBound, portID)
+	// if there is an active channel for this portID / connectionID return an error
+	activeChannelID, found := k.GetOpenActiveChannel(ctx, connectionID, portID)
+	if found {
+		return sdkerrors.Wrapf(icatypes.ErrActiveChannelAlreadySet, "existing active channel %s for portID %s on connection %s for owner %s", activeChannelID, portID, connectionID, owner)
 	}
 
-	cap := k.BindPort(ctx, portID)
-	if err := k.ClaimCapability(ctx, cap, host.PortPath(portID)); err != nil {
-		return sdkerrors.Wrap(err, "unable to bind to newly generated portID")
+	switch {
+	case k.portKeeper.IsBound(ctx, portID) && !k.IsBound(ctx, portID):
+		return sdkerrors.Wrapf(icatypes.ErrPortAlreadyBound, "another module has claimed capability for and bound port with portID: %s", portID)
+	case !k.portKeeper.IsBound(ctx, portID):
+		cap := k.BindPort(ctx, portID)
+		if err := k.ClaimCapability(ctx, cap, host.PortPath(portID)); err != nil {
+			return sdkerrors.Wrapf(err, "unable to bind to newly generated portID: %s", portID)
+		}
 	}
 
 	connectionEnd, err := k.channelKeeper.GetConnection(ctx, connectionID)

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

@@ -3,6 +3,7 @@ package keeper_test
 import (
 	icatypes "github.com/cosmos/ibc-go/v3/modules/apps/27-interchain-accounts/types"
 	channeltypes "github.com/cosmos/ibc-go/v3/modules/core/04-channel/types"
+	host "github.com/cosmos/ibc-go/v3/modules/core/24-host"
 	ibctesting "github.com/cosmos/ibc-go/v3/testing"
 )
 
@@ -22,9 +23,11 @@ func (suite *KeeperTestSuite) TestRegisterInterchainAccount() {
 			"success", func() {}, true,
 		},
 		{
-			"port is already bound",
+			"port is already bound for owner but capability is claimed by another module",
 			func() {
-				suite.chainA.GetSimApp().IBCKeeper.PortKeeper.BindPort(suite.chainA.GetContext(), TestPortID)
+				cap := suite.chainA.GetSimApp().IBCKeeper.PortKeeper.BindPort(suite.chainA.GetContext(), TestPortID)
+				err := suite.chainA.GetSimApp().TransferKeeper.ClaimCapability(suite.chainA.GetContext(), cap, host.PortPath(TestPortID))
+				suite.Require().NoError(err)
 			},
 			false,
 		},
@@ -56,7 +59,6 @@ func (suite *KeeperTestSuite) TestRegisterInterchainAccount() {
 			false,
 		},
 	}
-
 	for _, tc := range testCases {
 		tc := tc
 
@@ -77,7 +79,6 @@ func (suite *KeeperTestSuite) TestRegisterInterchainAccount() {
 			} else {
 				suite.Require().Error(err)
 			}
-
 		})
 	}
 }

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

@@ -13,8 +13,8 @@ var (
 	ErrInvalidRoute                = sdkerrors.Register(ModuleName, 7, "invalid route")
 	ErrInterchainAccountNotFound   = sdkerrors.Register(ModuleName, 8, "interchain account not found")
 	ErrInterchainAccountAlreadySet = sdkerrors.Register(ModuleName, 9, "interchain account is already set")
-	ErrActiveChannelNotFound       = sdkerrors.Register(ModuleName, 10, "no active channel for this owner")
-	ErrActiveChannelAlreadySet     = sdkerrors.Register(ModuleName, 11, "active channel already set for this owner")
+	ErrActiveChannelAlreadySet     = sdkerrors.Register(ModuleName, 10, "active channel already set for this owner")
+	ErrActiveChannelNotFound       = sdkerrors.Register(ModuleName, 11, "no active channel for this owner")
 	ErrInvalidVersion              = sdkerrors.Register(ModuleName, 12, "invalid interchain accounts version")
 	ErrInvalidAccountAddress       = sdkerrors.Register(ModuleName, 13, "invalid account address")
 	ErrUnsupported                 = sdkerrors.Register(ModuleName, 14, "interchain account does not support this action")