Revert if updating receiver fails

src/MultiBridgeMessageReceiver.sol

@@ -276,11 +276,13 @@ contract MultiBridgeMessageReceiver is IMultiBridgeMessageReceiver, ExecutorAwar
         if (_receiverAdapter == address(0)) {
             revert Error.ZERO_ADDRESS_INPUT();
         }
-        if (_add) {
-            _addTrustedExecutor(_receiverAdapter);
-        } else {
-            _removeTrustedExecutor(_receiverAdapter);
+        bool success = _add ? _addTrustedExecutor(_receiverAdapter) : _removeTrustedExecutor(_receiverAdapter);
+
+        if (!success) {
+            // only fails because we are either attempting to add an existing adapter, or remove a non-existing adapter
+            revert Error.UPDATE_RECEIVER_ADAPTER_FAILED(_add ? "adapter already added" : "adapter not found");
         }
+
         emit BridgeReceiverAdapterUpdated(_receiverAdapter, _add);
     }
 

src/libraries/Error.sol

@@ -20,6 +20,10 @@ library Error {
     /// @dev is thrown if caller is invalid receiver adapter
     error INVALID_RECEIVER_ADAPTER();
 
+    /// @dev is thrown if updating a receiver adapter fails
+    /// @param reason is the reason for failure
+    error UPDATE_RECEIVER_ADAPTER_FAILED(string reason);
+
     /// @dev is thrown if caller is not self
     error INVALID_SELF_CALLER();
 

test/unit-tests/MultiBridgeMessageReceiver.t.sol

@@ -400,6 +400,19 @@ contract MultiBridgeMessageReceiverTest is Setup {
         assertTrue(receiver.isTrustedExecutor(address(42)));
     }
 
+    /// @dev adding a receiver adapter that already exists should fail
+    function test_update_receiver_adapter_add_existing() public {
+        vm.startPrank(timelockAddr);
+
+        address[] memory updatedAdapters = new address[](1);
+        updatedAdapters[0] = wormholeAdapterAddr;
+        bool[] memory operations = new bool[](1);
+        operations[0] = true;
+
+        vm.expectRevert(abi.encodeWithSelector(Error.UPDATE_RECEIVER_ADAPTER_FAILED.selector, "adapter already added"));
+        receiver.updateReceiverAdapters(updatedAdapters, operations);
+    }
+
     /// @dev removes one receiver adapter
     function test_update_receiver_adapter_remove() public {
         vm.startPrank(timelockAddr);
@@ -420,6 +433,21 @@ contract MultiBridgeMessageReceiverTest is Setup {
         assertTrue(receiver.isTrustedExecutor(axelarAdapterAddr));
     }
 
+    /// @dev removing a receiver adapter that does not exist should fail
+    function test_update_receiver_adapter_remove_non_existing() public {
+        vm.startPrank(timelockAddr);
+
+        address[] memory updatedAdapters = new address[](1);
+        updatedAdapters[0] = address(42);
+        bool[] memory operations = new bool[](1);
+        operations[0] = false;
+
+        assertFalse(receiver.isTrustedExecutor(address(42)));
+
+        vm.expectRevert(abi.encodeWithSelector(Error.UPDATE_RECEIVER_ADAPTER_FAILED.selector, "adapter not found"));
+        receiver.updateReceiverAdapters(updatedAdapters, operations);
+    }
+
     /// @dev only governance timelock can call
     function test_update_receiver_adapter_only_governance_timelock() public {
         vm.startPrank(caller);