took into account comments

x/ccv/provider/keeper/msg_server.go

@@ -474,7 +474,13 @@ func (k msgServer) UpdateConsumer(goCtx context.Context, msg *types.MsgUpdateCon
 		return &resp, errorsmod.Wrapf(ccvtypes.ErrInvalidConsumerState, "cannot get consumer chain ID: %s", err.Error())
 	}
 
+	// We only validate and use `NewChainId` if it is not empty (because `NewChainId` is an optional argument)
+	// or `NewChainId` is different from the current chain id of the consumer chain.
 	if strings.TrimSpace(msg.NewChainId) != "" && msg.NewChainId != chainId {
+		if err = types.ValidateChainId("NewChainId", msg.NewChainId); err != nil {
+			return &resp, errorsmod.Wrapf(types.ErrInvalidMsgUpdateConsumer, "invalid new chain id: %s", err.Error())
+		}
+
 		if k.IsConsumerPrelaunched(ctx, consumerId) {
 			chainId = msg.NewChainId
 			k.SetConsumerChainId(ctx, consumerId, chainId)
@@ -521,14 +527,13 @@ func (k msgServer) UpdateConsumer(goCtx context.Context, msg *types.MsgUpdateCon
 	previousSpawnTime := previousInitializationParameters.SpawnTime
 
 	if msg.InitializationParameters != nil {
-		phase := k.GetConsumerPhase(ctx, consumerId)
-
-		if phase == types.CONSUMER_PHASE_LAUNCHED {
+		if !k.IsConsumerPrelaunched(ctx, consumerId) {
 			return &resp, errorsmod.Wrap(types.ErrInvalidMsgUpdateConsumer,
 				"cannot update the initialization parameters of an an already launched chain; "+
 					"do not provide any initialization parameters when updating a launched chain")
 		}
 
+		phase := k.GetConsumerPhase(ctx, consumerId)
 		if msg.InitializationParameters.SpawnTime.IsZero() {
 			if phase == types.CONSUMER_PHASE_INITIALIZED {
 				// chain was previously ready to launch at `previousSpawnTime` so we remove the

x/ccv/provider/keeper/msg_server_test.go

@@ -122,6 +122,17 @@ func TestUpdateConsumer(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, expectedChainId, chainId)
 
+	// assert that we cannot change the chain to that of a reserved chain id
+	_, err = msgServer.UpdateConsumer(ctx,
+		&providertypes.MsgUpdateConsumer{
+			Owner: "submitter", ConsumerId: consumerId,
+			Metadata:                 nil,
+			InitializationParameters: nil,
+			PowerShapingParameters:   nil,
+			NewChainId:               "stride-1", // reversed chain id
+		})
+	require.ErrorContains(t, err, "cannot use a reserved chain id")
+
 	expectedConsumerMetadata := providertypes.ConsumerMetadata{
 		Name:        "name2",
 		Description: "description2",

x/ccv/provider/types/msg.go

@@ -295,20 +295,35 @@ func NewMsgCreateConsumer(submitter, chainId string, metadata ConsumerMetadata,
 	}, nil
 }
 
-// ValidateBasic implements the sdk.HasValidateBasic interface.
-func (msg MsgCreateConsumer) ValidateBasic() error {
-	if err := ValidateStringField("ChainId", msg.ChainId, cmttypes.MaxChainIDLen); err != nil {
-		return errorsmod.Wrapf(ErrInvalidMsgCreateConsumer, "ChainId: %s", err.Error())
-	}
-
+// IsReservedChainId returns true if the specific chain id is reserved and cannot be used by other consumer chains
+func IsReservedChainId(chainId string) bool {
 	// With permissionless ICS, we can have multiple consumer chains with the exact same chain id.
 	// However, as we already have the Neutron and Stride Top N chains running, as a first step we would like to
 	// prevent permissionless chains from re-using the chain ids of Neutron and Stride. Note that this is just a
 	// preliminary measure that will be removed later on as part of:
 	// TODO (#2242): find a better way of ignoring past misbehaviors
-	if msg.ChainId == "neutron-1" || msg.ChainId == "stride-1" {
-		return errorsmod.Wrapf(ErrInvalidMsgCreateConsumer,
-			"cannot reuse chain ids of existing Neutron and Stride Top N consumer chains")
+	return chainId == "neutron-1" || chainId == "stride-1"
+}
+
+// ValidateChainId validates that the chain id is valid and is not reserved.
+// Can be called for the `MsgUpdateConsumer.NewChainId` field as well, so this method takes the `field` as an argument
+// to return more appropriate error messages in case the validation fails.
+func ValidateChainId(field string, chainId string) error {
+	if err := ValidateStringField(field, chainId, cmttypes.MaxChainIDLen); err != nil {
+		return errorsmod.Wrapf(ErrInvalidMsgCreateConsumer, "%s: %s", field, err.Error())
+	}
+
+	if IsReservedChainId(chainId) {
+		return errorsmod.Wrapf(ErrInvalidMsgCreateConsumer, "cannot use a reserved chain id")
+	}
+
+	return nil
+}
+
+// ValidateBasic implements the sdk.HasValidateBasic interface.
+func (msg MsgCreateConsumer) ValidateBasic() error {
+	if err := ValidateChainId("ChainId", msg.ChainId); err != nil {
+		return errorsmod.Wrapf(ErrInvalidMsgCreateConsumer, "ChainId: %s", err.Error())
 	}
 
 	if err := ValidateConsumerMetadata(msg.Metadata); err != nil {
@@ -389,9 +404,10 @@ func (msg MsgUpdateConsumer) ValidateBasic() error {
 		}
 	}
 
-	if msg.NewChainId != "" && len(msg.NewChainId) > cmttypes.MaxChainIDLen {
-		return errorsmod.Wrapf(ErrInvalidMsgUpdateConsumer, "NewChainId (%s) is too long; got: %d, max: %d",
-			msg.NewChainId, len(msg.NewChainId), cmttypes.MaxChainIDLen)
+	if strings.TrimSpace(msg.NewChainId) != "" {
+		if err := ValidateStringField("NewChainId", msg.NewChainId, cmttypes.MaxChainIDLen); err != nil {
+			return errorsmod.Wrapf(ErrInvalidMsgUpdateConsumer, "NewChainId: %s", err.Error())
+		}
 	}
 
 	return nil

x/ccv/provider/types/msg_test.go

@@ -1,6 +1,7 @@
 package types_test
 
 import (
+	"strings"
 	"testing"
 	"time"
 
@@ -554,7 +555,7 @@ func TestMsgUpdateConsumerValidateBasic(t *testing.T) {
 		{
 			"too long new chain id",
 			types.PowerShapingParameters{},
-			"this is an extremely long chain id that is so long that the validation would fail",
+			strings.Repeat("thisIsAnExtremelyLongChainId", 2),
 			false,
 		},
 	}
@@ -725,3 +726,50 @@ func TestValidateInitialHeight(t *testing.T) {
 		}
 	}
 }
+
+func TestValidateChainId(t *testing.T) {
+	testCases := []struct {
+		name    string
+		chainId string
+		expPass bool
+	}{
+		{
+			name:    "valid chain id",
+			chainId: "chain-1",
+			expPass: true,
+		},
+		{
+			name:    "valid chain id with no revision",
+			chainId: "chainId",
+			expPass: true,
+		},
+		{
+			name:    "invalid (too long) chain id",
+			chainId: strings.Repeat("thisIsAnExtremelyLongChainId", 2),
+			expPass: false,
+		},
+		{
+			name:    "reserved chain id",
+			chainId: "stride-1",
+			expPass: false,
+		},
+		{
+			name:    "reserved chain id",
+			chainId: "neutron-1",
+			expPass: false,
+		},
+		{
+			name:    "empty chain id",
+			chainId: "    ",
+			expPass: false,
+		},
+	}
+	for _, tc := range testCases {
+		err := types.ValidateChainId("ChainId", tc.chainId)
+		if tc.expPass {
+			require.NoError(t, err, "valid case: '%s' should not return error. got %w", tc.name, err)
+		} else {
+			require.Error(t, err, "invalid case: '%s' must return error but got none", tc.name)
+		}
+	}
+}