refactor: RegisterInterchainAccount (#814)

## Description

closes: #802

---

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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

(cherry picked from commit fed6a86)

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")