feat: add OperatorSharesSlashed event to track shares slashed per operator (#1051)

* feat: add OperatorSharesSlashed event to track shares slashed per operator

* feat: add unit tests

* fix: add more tests

Author: bowenli86

src/contracts/core/DelegationManager.sol

@@ -307,6 +307,9 @@ contract DelegationManager is
             sharesToDecrease: operatorSharesSlashed
         });
 
+        // Emit event for operator shares being slashed
+        emit OperatorSharesSlashed(operator, strategy, totalDepositSharesToBurn);
+
         IShareManager shareManager = _getShareManager(strategy);
         // NOTE: for beaconChainETHStrategy, increased burnable shares currently have no mechanism for burning
         shareManager.increaseBurnableShares(strategy, totalDepositSharesToBurn);

src/contracts/interfaces/IDelegationManager.sol

@@ -170,6 +170,9 @@ interface IDelegationManagerEvents is IDelegationManagerTypes {
 
     /// @notice Emitted when a queued withdrawal is completed
     event SlashingWithdrawalCompleted(bytes32 withdrawalRoot);
+
+    /// @notice Emitted whenever an operator's shares are slashed for a given strategy
+    event OperatorSharesSlashed(address indexed operator, IStrategy strategy, uint256 totalSlashedShares);
 }
 
 /**

src/test/unit/DelegationUnit.t.sol

@@ -6910,6 +6910,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                 sharesToBurn: sharesToBurn
             })
         );
+        
+        // Assert OperatorSharesSlashed event was emitted with correct params
+        cheats.expectEmit(true, true, true, true, address(delegationManager));
+        emit OperatorSharesSlashed(operator, strategyMock, sharesToBurn);
+
         cheats.prank(address(allocationManagerMock));
         delegationManager.slashOperatorShares({
             operator: operator,
@@ -6994,6 +6999,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                 sharesToBurn: sharesToBurn
             })
         );
+
+        // Assert OperatorSharesSlashed event was emitted with correct params
+        cheats.expectEmit(true, true, true, true, address(delegationManager));
+        emit OperatorSharesSlashed(operator, strategyMock, sharesToBurn);
+
         cheats.prank(address(allocationManagerMock));
         delegationManager.slashOperatorShares({
             operator: operator,
@@ -7072,6 +7082,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                 sharesToBurn: sharesToBurn
             })
         );
+
+        // Assert OperatorSharesSlashed event was emitted with correct params
+        cheats.expectEmit(true, true, true, true, address(delegationManager));
+        emit OperatorSharesSlashed(operator, strategyMock, sharesToBurn);
+
         cheats.prank(address(allocationManagerMock));
         delegationManager.slashOperatorShares({
             operator: operator,
@@ -7163,6 +7178,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                 sharesToBurn: sharesToBurn
             })
         );
+
+        // Assert OperatorSharesSlashed event was emitted with correct params
+        cheats.expectEmit(true, true, true, true, address(delegationManager));
+        emit OperatorSharesSlashed(operator, strategyMock, sharesToBurn);
+
         cheats.prank(address(allocationManagerMock));
         delegationManager.slashOperatorShares({
             operator: operator,
@@ -7237,6 +7257,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                     sharesToBurn: sharesToBurn
                 })
             );
+
+            // Assert OperatorSharesSlashed event was emitted with correct params
+            cheats.expectEmit(true, true, true, true, address(delegationManager));
+            emit OperatorSharesSlashed(operator, strategyMock, sharesToBurn);
+
             cheats.prank(address(allocationManagerMock));
             delegationManager.slashOperatorShares({
                 operator: operator,
@@ -7294,6 +7319,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                     sharesToBurn: sharesToBurn
                 })
             );
+
+            // Assert OperatorSharesSlashed event was emitted with correct params
+            cheats.expectEmit(true, true, true, true, address(delegationManager));
+            emit OperatorSharesSlashed(operator, strategyMock, sharesToBurn);
+
             cheats.prank(address(allocationManagerMock));
             delegationManager.slashOperatorShares({
                 operator: operator,
@@ -7399,6 +7429,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
                 sharesToBurn: 0
             })
         );
+
+        // Assert OperatorSharesSlashed event was emitted with correct params
+        cheats.expectEmit(true, true, true, true, address(delegationManager));
+        emit OperatorSharesSlashed(operator, strategyMock, 0);
+
         cheats.prank(address(allocationManagerMock));
         delegationManager.slashOperatorShares({
             operator: operator,
@@ -7474,6 +7509,11 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
         _setOperatorMagnitude(operator, beaconChainETHStrategy, newMagnitude);
         cheats.expectEmit(true, true, true, true, address(delegationManager));
         emit OperatorSharesDecreased(operator, address(0), beaconChainETHStrategy, sharesToDecrease);
+
+        // Assert OperatorSharesSlashed event was emitted with correct params
+        cheats.expectEmit(true, true, true, true, address(delegationManager));
+        emit OperatorSharesSlashed(operator, beaconChainETHStrategy, sharesToDecrease);
+
         cheats.prank(address(allocationManagerMock));
         delegationManager.slashOperatorShares({
             operator: operator,
@@ -7518,6 +7558,10 @@ contract DelegationManagerUnitTests_slashingShares is DelegationManagerUnitTests
             newOperatorMagnitude -= slashMagnitude;
             _setOperatorMagnitude(defaultOperator, strategyMock, newOperatorMagnitude);
 
+            // Assert OperatorSharesSlashed event was emitted with correct params
+            cheats.expectEmit(true, true, true, true, address(delegationManager));
+            emit OperatorSharesSlashed(defaultOperator, strategyMock, 44440000449046438731194137360795695);
+
             cheats.prank(address(allocationManagerMock));
             delegationManager.slashOperatorShares(
                 defaultOperator,