fix hop length validation

Author: jcompagni10

x/dex/keeper/msg_server_test.go

@@ -2500,6 +2500,26 @@ func TestMsgMultiHopSwapValidate(t *testing.T) {
 			},
 			types.ErrZeroExitPrice,
 		},
+		{
+			"single hop",
+			types.MsgMultiHopSwap{
+				Creator:  sample.AccAddress(),
+				Receiver: sample.AccAddress(),
+				Routes:   []*types.MultiHopRoute{{Hops: []string{"TokenA"}}},
+				AmountIn: sdkmath.OneInt(),
+			},
+			types.ErrRouteWithoutExitToken,
+		},
+		{
+			"no hops",
+			types.MsgMultiHopSwap{
+				Creator:  sample.AccAddress(),
+				Receiver: sample.AccAddress(),
+				Routes:   []*types.MultiHopRoute{{Hops: []string{}}},
+				AmountIn: sdkmath.OneInt(),
+			},
+			types.ErrRouteWithoutExitToken,
+		},
 	}
 
 	for _, tt := range tests {

x/dex/types/message_multi_hop_swap.go

@@ -114,12 +114,12 @@ func validateRoutes(routes []*MultiHopRoute) error {
 }
 
 func validateHops(hops []string) error {
+	// check that route has at least entry and exit token
+	if len(hops) < 2 {
+		return ErrRouteWithoutExitToken
+	}
 	existingHops := make(map[string]bool, len(hops))
 	for _, hop := range hops {
-		// check that route has at least entry and exit token
-		if len(hop) < 2 {
-			return ErrRouteWithoutExitToken
-		}
 		// check if we find cycles in the route
 		if existingHops[hop] {
 			return ErrCycleInHops