[ETHEREUM-CONTRACTS] BatchLiquidator: don't revert for non-transferrable SuperTokens

packages/ethereum-contracts/contracts/utils/BatchLiquidator.sol

@@ -70,7 +70,10 @@ contract BatchLiquidator {
         {
             uint256 balance = ERC20(superToken).balanceOf(address(this));
             if (balance > 0) {
-                ERC20(superToken).transferFrom(address(this), msg.sender, balance);
+                // don't fail for non-transferrable tokens
+                try ERC20(superToken).transferFrom(address(this), msg.sender, balance)
+                // solhint-disable-next-line no-empty-blocks
+                {} catch {}
             }
         }
     }
@@ -110,7 +113,9 @@ contract BatchLiquidator {
         {
             uint256 balance = ERC20(superToken).balanceOf(address(this));
             if (balance > 0) {
-                ERC20(superToken).transferFrom(address(this), msg.sender, balance);
+                try ERC20(superToken).transferFrom(address(this), msg.sender, balance)
+                // solhint-disable-next-line no-empty-blocks
+                {} catch {}
             }
         }
     }

packages/ethereum-contracts/test/foundry/utils/BatchLiquidator.t.sol

@@ -2,8 +2,30 @@
 pragma solidity 0.8.19;
 
 import { FoundrySuperfluidTester, SuperTokenV1Library } from "../FoundrySuperfluidTester.sol";
-import { ISuperToken } from "../../../contracts/superfluid/SuperToken.sol";
+import { ISuperToken, SuperToken, ISuperfluid, IConstantOutflowNFT, IConstantInflowNFT } from "../../../contracts/superfluid/SuperToken.sol";
 import { BatchLiquidator } from "../../../contracts/utils/BatchLiquidator.sol";
+import "forge-std/Test.sol";
+
+contract NonTransferableST is SuperToken {
+ // transferFrom will always revert
+    constructor(
+        ISuperfluid host
+    )
+    SuperToken(host, IConstantOutflowNFT(address(0)), IConstantInflowNFT(address(0))) // solhint-disable-next-line no-empty-blocks
+    {
+    }
+
+    function transferFrom(address holder, address recipient, uint256 amount)  public override returns (bool) {
+        revert();
+    }
+
+    function mintInternal(
+        address to,
+        uint256 amount
+    ) external {
+        _mint(msg.sender, to, amount, false /* invokeHook */, false /* requireReceptionAck */, "", "");
+    }
+}
 
 contract BatchLiquidatorTest is FoundrySuperfluidTester {
     using SuperTokenV1Library for ISuperToken;
@@ -13,11 +35,14 @@ contract BatchLiquidatorTest is FoundrySuperfluidTester {
 
     int96 internal constant FLOW_RATE = 10000000000;
 
+    ISuperToken badToken;
+
     constructor() FoundrySuperfluidTester(5) { }
 
     function setUp() public override {
         super.setUp();
         batchLiquidator = new BatchLiquidator(address(sf.host), address(sf.cfa));
+        badToken = new NonTransferableST(sf.host);
     }
 
     // Helpers
@@ -129,4 +154,54 @@ contract BatchLiquidatorTest is FoundrySuperfluidTester {
         );
         vm.stopPrank();
     }
+
+    function testLiquidationWithCustomTokenRevert() public {
+        NonTransferableST(address(badToken)).mintInternal(alice, 10 ether);
+
+        vm.startPrank(alice);
+        badToken.createFlow(bob, FLOW_RATE);
+        badToken.transferAll(admin);
+        vm.warp(4 hours); // jump 4 hours
+        vm.stopPrank();
+        vm.startPrank(liquidator);
+
+        batchLiquidator.deleteFlow(address(badToken), alice, bob);
+        _assertNoFlow(alice, bob);
+
+        assertTrue(
+            superToken.balanceOf(liquidator) == 0, "BatchLiquidator: SL - Balance should be 0 because of revert"
+        );
+        vm.stopPrank();
+
+    }
+
+    function testBatchLiquidationWithCustomTokenRevert() public {
+        NonTransferableST(address(badToken)).mintInternal(alice, 10 ether);
+        NonTransferableST(address(badToken)).mintInternal(bob, 10 ether);
+
+        vm.startPrank(alice);
+        badToken.createFlow(bob, FLOW_RATE);
+        badToken.transferAll(admin);
+        vm.stopPrank();
+
+        vm.startPrank(bob);
+        badToken.createFlow(carol, FLOW_RATE);
+        badToken.transferAll(admin);
+        vm.stopPrank();
+
+        vm.warp(4 hours); // jump 4 hours
+
+        vm.startPrank(liquidator);
+
+        address[] memory senders = new address[](2);
+        address[] memory receivers = new address[](2);
+        senders[0] = alice;
+        senders[1] = bob;
+        receivers[0] = bob;
+        receivers[1] = carol;
+
+        batchLiquidator.deleteFlows(address(superToken), senders, receivers);
+        _assertNoFlow(alice, bob);
+        _assertNoFlow(bob, carol);
+    }
 }