add a util function in MessageReceiverApp to deal with the "receving native token" issue

contracts/interfaces/IBridge.sol

@@ -3,6 +3,8 @@
 pragma solidity >=0.8.0;
 
 interface IBridge {
+    function nativeWrap() external view returns (address);
+
     function send(
         address _receiver,
         address _token,

contracts/message/apps/BatchTransfer.sol

@@ -123,6 +123,7 @@ contract BatchTransfer is MessageSenderApp, MessageReceiverApp {
         address // executor
     ) external payable override onlyMessageBus returns (ExecutionStatus) {
         TransferRequest memory transfer = abi.decode((_message), (TransferRequest));
+        wrapBridgeOutToken(_token, _amount);
         uint256 totalAmt;
         for (uint256 i = 0; i < transfer.accounts.length; i++) {
             IERC20(_token).safeTransfer(transfer.accounts[i], transfer.amounts[i]);
@@ -150,6 +151,7 @@ contract BatchTransfer is MessageSenderApp, MessageReceiverApp {
         address // executor
     ) external payable override onlyMessageBus returns (ExecutionStatus) {
         TransferRequest memory transfer = abi.decode((_message), (TransferRequest));
+        wrapBridgeOutToken(_token, _amount);
         IERC20(_token).safeTransfer(transfer.sender, _amount);
         bytes memory message = abi.encode(TransferReceipt({nonce: transfer.nonce, status: TransferStatus.Fail}));
         sendMessage(_sender, _srcChainId, message, msg.value);

contracts/message/apps/MsgTest.sol

@@ -61,6 +61,7 @@ contract MsgTest is MessageSenderApp, MessageReceiverApp {
         address // executor
     ) external payable override onlyMessageBus returns (ExecutionStatus) {
         (address receiver, bytes memory message) = abi.decode((_message), (address, bytes));
+        wrapBridgeOutToken(_token, _amount);
         IERC20(_token).safeTransfer(receiver, _amount);
         emit MessageReceivedWithTransfer(_token, _amount, _sender, _srcChainId, receiver, message);
         return ExecutionStatus.Success;
@@ -73,6 +74,7 @@ contract MsgTest is MessageSenderApp, MessageReceiverApp {
         address // executor
     ) external payable override onlyMessageBus returns (ExecutionStatus) {
         (address receiver, bytes memory message) = abi.decode((_message), (address, bytes));
+        wrapBridgeOutToken(_token, _amount);
         IERC20(_token).safeTransfer(receiver, _amount);
         emit Refunded(receiver, _token, _amount, message);
         return ExecutionStatus.Success;

contracts/message/apps/TransferSwap.sol

@@ -258,6 +258,7 @@ contract TransferSwap is MessageSenderApp, MessageReceiverApp {
         address // executor
     ) external payable override onlyMessageBus returns (ExecutionStatus) {
         SwapRequest memory m = abi.decode((_message), (SwapRequest));
+        wrapBridgeOutToken(_token, _amount);
         require(_token == m.swap.path[0], "bridged token must be the same as the first token in destination swap path");
         bytes32 id = _computeSwapRequestId(m.receiver, _srcChainId, uint64(block.chainid), _message);
         uint256 dstAmount;

contracts/message/framework/MessageReceiverApp.sol

@@ -3,6 +3,9 @@
 pragma solidity 0.8.9;
 
 import "../interfaces/IMessageReceiverApp.sol";
+import "../interfaces/IMessageBus.sol";
+import "../../interfaces/IBridge.sol";
+import "../../interfaces/IWETH.sol";
 import "./MessageBusAddress.sol";
 
 abstract contract MessageReceiverApp is IMessageReceiverApp, MessageBusAddress {
@@ -81,4 +84,24 @@ abstract contract MessageReceiverApp is IMessageReceiverApp, MessageBusAddress {
         bytes calldata _message,
         address _executor
     ) external payable virtual override onlyMessageBus returns (ExecutionStatus) {}
+
+    /**
+     * @notice util function that checks whether the bridge out token is native and wraps it
+     * @dev when the bridged token is a native or wrapped native token, whether your contracts receives native/wrapped token depends on whether
+     * the "nativeWrap" field is set in the Bridge contract. An easy but sometimes gas-inefficient way to deal with this is to always check and
+     * wrap the bridge out token using this function.
+     * note Assumption: only the liquidity bridge is capable of sending a native wrap
+     * @param _bridgeOutToken token out from liquidity bridge
+     * @param _amount amount of token
+     */
+    function wrapBridgeOutToken(address _bridgeOutToken, uint256 _amount) internal {
+        address bridge = IMessageBus(messageBus).liquidityBridge();
+        if (bridge == address(0)) {
+            return;
+        }
+        address nativeWrap = IBridge(bridge).nativeWrap();
+        if (_bridgeOutToken == nativeWrap) {
+            IWETH(nativeWrap).deposit{value: _amount}();
+        }
+    }
 }