prevent protocol fee recipient from being address(0) when protocol fee is non-zero

Spearbit #5

Author: hoytech

src/EulerSwapProtocolFeeConfig.sol

@@ -30,6 +30,7 @@ contract EulerSwapProtocolFeeConfig is IEulerSwapProtocolFeeConfig, EVCUtil {
 
     error Unauthorized();
     error InvalidProtocolFee();
+    error InvalidProtocolFeeRecipient();
 
     constructor(address evc, address admin_) EVCUtil(evc) {
         admin = admin_;
@@ -52,6 +53,7 @@ contract EulerSwapProtocolFeeConfig is IEulerSwapProtocolFeeConfig, EVCUtil {
     /// @inheritdoc IEulerSwapProtocolFeeConfig
     function setDefault(address recipient, uint64 fee) external onlyAdmin {
         require(fee <= MAX_PROTOCOL_FEE, InvalidProtocolFee());
+        require(fee == 0 || recipient != address(0), InvalidProtocolFeeRecipient());
 
         defaultRecipient = recipient;
         defaultFee = fee;

test/Fees.t.sol

@@ -221,6 +221,10 @@ contract FeesTest is EulerSwapTestBase {
         vm.expectRevert(EulerSwapProtocolFeeConfig.InvalidProtocolFee.selector);
         protocolFeeConfig.setDefault(address(8888), 0.15000001e18);
 
+        vm.prank(protocolFeeAdmin);
+        vm.expectRevert(EulerSwapProtocolFeeConfig.InvalidProtocolFeeRecipient.selector);
+        protocolFeeConfig.setDefault(address(0), 0.1e18);
+
         // Set a default
 
         vm.prank(protocolFeeAdmin);
@@ -275,6 +279,17 @@ contract FeesTest is EulerSwapTestBase {
             assertEq(recipient, address(7777));
             assertEq(fee, 0.12e18);
         }
+
+        // Change override back to 0s
+
+        vm.prank(protocolFeeAdmin);
+        protocolFeeConfig.setDefault(address(0), 0);
+
+        {
+            (address recipient, uint64 fee) = protocolFeeConfig.getProtocolFee(address(eulerSwap));
+            assertEq(recipient, address(0));
+            assertEq(fee, 0);
+        }
     }
 
     function test_fees_protocolFees_setAdmin() public {