fix: change non nil relayer check to non empty

CHANGELOG.md

@@ -81,6 +81,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* (apps/29-fee) [\#1774](https://github.com/cosmos/ibc-go/pull/1774) Change non nil relayer assertion to non empty to avoid import/export issues for genesis upgrades. 
 * (makefile) [\#1785](https://github.com/cosmos/ibc-go/pull/1785) Fetch the correct versions of protocol buffers dependencies from tendermint, cosmos-sdk, and ics23.
 * (apps/29-fee) [\#1278](https://github.com/cosmos/ibc-go/pull/1278) The URI path for the query to get all incentivized packets for a specific channel did not follow the same format as the rest of queries.
 

modules/apps/29-fee/types/errors.go

@@ -10,7 +10,7 @@ var (
 	ErrRefundAccNotFound             = sdkerrors.Register(ModuleName, 3, "no account found for given refund address")
 	ErrBalanceNotFound               = sdkerrors.Register(ModuleName, 4, "balance not found for given account address")
 	ErrFeeNotFound                   = sdkerrors.Register(ModuleName, 5, "there is no fee escrowed for the given packetID")
-	ErrRelayersNotNil                = sdkerrors.Register(ModuleName, 6, "relayers must be nil. This feature is not supported")
+	ErrRelayersNotEmpty              = sdkerrors.Register(ModuleName, 6, "relayers must not be set. This feature is not supported")
 	ErrCounterpartyPayeeEmpty        = sdkerrors.Register(ModuleName, 7, "counterparty payee must not be empty")
 	ErrForwardRelayerAddressNotFound = sdkerrors.Register(ModuleName, 8, "forward relayer address not found")
 	ErrFeeNotEnabled                 = sdkerrors.Register(ModuleName, 9, "fee module is not enabled for this channel. If this error occurs after channel setup, fee module may not be enabled")

modules/apps/29-fee/types/fee.go

@@ -25,9 +25,9 @@ func (p PacketFee) Validate() error {
 		return sdkerrors.Wrap(err, "failed to convert RefundAddress into sdk.AccAddress")
 	}
 
-	// enforce relayer is nil
-	if p.Relayers != nil {
-		return ErrRelayersNotNil
+	// enforce relayers are not set
+	if len(p.Relayers) != 0 {
+		return ErrRelayersNotEmpty
 	}
 
 	if err := p.Fee.Validate(); err != nil {

modules/apps/29-fee/types/fee_test.go

@@ -47,6 +47,13 @@ func TestPacketFeeValidation(t *testing.T) {
 			func() {},
 			true,
 		},
+		{
+			"success with empty slice for Relayers",
+			func() {
+				packetFee.Relayers = []string{}
+			},
+			true,
+		},
 		{
 			"should fail when refund address is invalid",
 			func() {
@@ -102,6 +109,13 @@ func TestPacketFeeValidation(t *testing.T) {
 			},
 			false,
 		},
+		{
+			"should fail with non empty Relayers",
+			func() {
+				packetFee.Relayers = []string{"relayer"}
+			},
+			false,
+		},
 	}
 
 	for _, tc := range testCases {
@@ -113,9 +127,9 @@ func TestPacketFeeValidation(t *testing.T) {
 		err := packetFee.Validate()
 
 		if tc.expPass {
-			require.NoError(t, err)
+			require.NoError(t, err, tc.name)
 		} else {
-			require.Error(t, err)
+			require.Error(t, err, tc.name)
 		}
 	}
 }

modules/apps/29-fee/types/msgs.go

@@ -133,9 +133,9 @@ func (msg MsgPayPacketFee) ValidateBasic() error {
 		return sdkerrors.Wrap(err, "failed to convert msg.Signer into sdk.AccAddress")
 	}
 
-	// enforce relayer is nil
-	if msg.Relayers != nil {
-		return ErrRelayersNotNil
+	// enforce relayer is not set
+	if len(msg.Relayers) != 0 {
+		return ErrRelayersNotEmpty
 	}
 
 	if err := msg.Fee.Validate(); err != nil {

modules/apps/29-fee/types/msgs_test.go

@@ -172,6 +172,13 @@ func TestMsgPayPacketFeeValidation(t *testing.T) {
 			func() {},
 			true,
 		},
+		{
+			"success with empty relayers",
+			func() {
+				msg.Relayers = []string{}
+			},
+			true,
+		},
 		{
 			"invalid channelID",
 			func() {
@@ -211,9 +218,9 @@ func TestMsgPayPacketFeeValidation(t *testing.T) {
 		err := msg.ValidateBasic()
 
 		if tc.expPass {
-			require.NoError(t, err)
+			require.NoError(t, err, tc.name)
 		} else {
-			require.Error(t, err)
+			require.Error(t, err, tc.name)
 		}
 	}
 }
@@ -258,6 +265,13 @@ func TestMsgPayPacketFeeAsyncValidation(t *testing.T) {
 			func() {},
 			true,
 		},
+		{
+			"success with empty relayers",
+			func() {
+				msg.PacketFee.Relayers = []string{}
+			},
+			true,
+		},
 		{
 			"invalid channelID",
 			func() {
@@ -355,9 +369,9 @@ func TestMsgPayPacketFeeAsyncValidation(t *testing.T) {
 		err := msg.ValidateBasic()
 
 		if tc.expPass {
-			require.NoError(t, err)
+			require.NoError(t, err, tc.name)
 		} else {
-			require.Error(t, err)
+			require.Error(t, err, tc.name)
 		}
 	}
 }