feat: add helper function for parsing clientID from client state path

CHANGELOG.md

@@ -115,6 +115,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Features
 
+* (core/24-host) [\#2820](https://github.com/cosmos/ibc-go/pull/2820) Add `MustParseClientStatePath` which parses the clientID from a client state key path. 
 * (apps/27-interchain-accounts) [\#2147](https://github.com/cosmos/ibc-go/pull/2147) Adding a `SubmitTx` gRPC endpoint for the ICS27 Controller module which allows owners of interchain accounts to submit transactions. This replaces the previously existing need for authentication modules to implement this standard functionality.
 * (testing/simapp) [\#2190](https://github.com/cosmos/ibc-go/pull/2190) Adding the new `x/group` cosmos-sdk module to simapp.
 

modules/core/02-client/keeper/keeper.go

@@ -359,15 +359,16 @@ func (k Keeper) IterateClients(ctx sdk.Context, cb func(clientID string, cs expo
 
 	defer iterator.Close()
 	for ; iterator.Valid(); iterator.Next() {
-		keySplit := strings.Split(string(iterator.Key()), "/")
-		if keySplit[len(keySplit)-1] != host.KeyClientState {
+		path := string(iterator.Key())
+		if !strings.Contains(path, host.KeyClientState) {
+			// skip non client state keys
 			continue
 		}
+
+		clientID := host.MustParseClientStatePath(path)
 		clientState := k.MustUnmarshalClientState(iterator.Value())
 
-		// key is ibc/{clientid}/clientState
-		// Thus, keySplit[1] is clientID
-		if cb(keySplit[1], clientState) {
+		if cb(clientID, clientState) {
 			break
 		}
 	}

modules/core/24-host/parse.go

@@ -32,6 +32,40 @@ func ParseIdentifier(identifier, prefix string) (uint64, error) {
 	return sequence, nil
 }
 
+// MustParseClientStatePath returns the client ID from a client state path. It panics
+// if the provided path is invalid or if the clientID is empty.
+func MustParseClientStatePath(path string) string {
+	clientID, err := parseClientStatePath(path)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	return clientID
+}
+
+// parseClientStatePath returns the client ID from a client state path. It returns
+// an error if the provided path is invalid.
+func parseClientStatePath(path string) (string, error) {
+	split := strings.Split(path, "/")
+	if len(split) != 3 {
+		return "", sdkerrors.Wrapf(ErrInvalidPath, "cannot parse client state path %s", path)
+	}
+
+	if split[0] != string(KeyClientStorePrefix) {
+		return "", sdkerrors.Wrapf(ErrInvalidPath, "path does not begin with client store prefix: expected %s, got %s", KeyClientStorePrefix, split[0])
+	}
+
+	if split[2] != KeyClientState {
+		return "", sdkerrors.Wrapf(ErrInvalidPath, "path does not end with client state key: expected %s, got %s", KeyClientState, split[2])
+	}
+
+	if strings.TrimSpace(split[1]) == "" {
+		return "", sdkerrors.Wrap(ErrInvalidPath, "clientID is empty")
+	}
+
+	return split[1], nil
+}
+
 // ParseConnectionPath returns the connection ID from a full path. It returns
 // an error if the provided path is invalid.
 func ParseConnectionPath(path string) (string, error) {

modules/core/24-host/parse_test.go

@@ -1,13 +1,15 @@
 package host_test
 
 import (
+	"fmt"
 	"math"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	connectiontypes "github.com/cosmos/ibc-go/v6/modules/core/03-connection/types"
 	host "github.com/cosmos/ibc-go/v6/modules/core/24-host"
+	ibctesting "github.com/cosmos/ibc-go/v6/testing"
 )
 
 func TestParseIdentifier(t *testing.T) {
@@ -46,3 +48,32 @@ func TestParseIdentifier(t *testing.T) {
 		}
 	}
 }
+
+func TestMustParseClientStatePath(t *testing.T) {
+	testCases := []struct {
+		name    string
+		path    string
+		expPass bool
+	}{
+		{"valid", host.FullClientStatePath(ibctesting.FirstClientID), true},
+		{"path too large", fmt.Sprintf("clients/clients/%s/clientState", ibctesting.FirstClientID), false},
+		{"path too small", fmt.Sprintf("clients/%s", ibctesting.FirstClientID), false},
+		{"path does not begin with client store", fmt.Sprintf("cli/%s/%s", ibctesting.FirstClientID, host.KeyClientState), false},
+		{"path does not end with client state key", fmt.Sprintf("%s/%s/consensus", string(host.KeyClientStorePrefix), ibctesting.FirstClientID), false},
+		{"client ID is empty", host.FullClientStatePath(""), false},
+		{"client ID is only spaces", host.FullClientStatePath("   "), false},
+	}
+
+	for _, tc := range testCases {
+		if tc.expPass {
+			require.NotPanics(t, func() {
+				clientID := host.MustParseClientStatePath(tc.path)
+				require.Equal(t, ibctesting.FirstClientID, clientID)
+			})
+		} else {
+			require.Panics(t, func() {
+				host.MustParseClientStatePath(tc.path)
+			})
+		}
+	}
+}