feat: make vault onSlash() return real slashed amount

src/contracts/delegator/BaseDelegator.sol

@@ -175,18 +175,18 @@ contract BaseDelegator is
     function onSlash(
         bytes32 subnetwork,
         address operator,
-        uint256 slashedAmount,
+        uint256 amount,
         uint48 captureTimestamp,
         bytes memory data
     ) external nonReentrant {
-        if (IVault(vault).slasher() != msg.sender) {
+        if (msg.sender != IVault(vault).slasher()) {
             revert NotSlasher();
         }
 
         address hook_ = hook;
         if (hook_ != address(0)) {
             bytes memory calldata_ = abi.encodeWithSelector(
-                IDelegatorHook.onSlash.selector, subnetwork, operator, slashedAmount, captureTimestamp, data
+                IDelegatorHook.onSlash.selector, subnetwork, operator, amount, captureTimestamp, data
             );
 
             if (gasleft() < HOOK_RESERVE + HOOK_GAS_LIMIT * 64 / 63) {
@@ -198,7 +198,7 @@ contract BaseDelegator is
             }
         }
 
-        emit OnSlash(subnetwork, operator, slashedAmount);
+        emit OnSlash(subnetwork, operator, amount, captureTimestamp);
     }
 
     function _initialize(

src/contracts/vault/Vault.sol

@@ -218,7 +218,7 @@ contract Vault is VaultStorage, MigratableEntity, AccessControlUpgradeable, IVau
     /**
      * @inheritdoc IVault
      */
-    function onSlash(uint256 slashedAmount, uint48 captureTimestamp) external nonReentrant {
+    function onSlash(uint256 amount, uint48 captureTimestamp) external nonReentrant returns (uint256 slashedAmount) {
         if (msg.sender != slasher) {
             revert NotSlasher();
         }
@@ -233,7 +233,7 @@ contract Vault is VaultStorage, MigratableEntity, AccessControlUpgradeable, IVau
         uint256 nextWithdrawals = withdrawals[currentEpoch_ + 1];
         if (captureEpoch == currentEpoch_) {
             uint256 slashableStake = activeStake_ + nextWithdrawals;
-            slashedAmount = Math.min(slashedAmount, slashableStake);
+            slashedAmount = Math.min(amount, slashableStake);
             if (slashedAmount > 0) {
                 uint256 activeSlashed = slashedAmount.mulDiv(activeStake_, slashableStake);
                 uint256 nextWithdrawalsSlashed = slashedAmount - activeSlashed;
@@ -244,7 +244,7 @@ contract Vault is VaultStorage, MigratableEntity, AccessControlUpgradeable, IVau
         } else {
             uint256 withdrawals_ = withdrawals[currentEpoch_];
             uint256 slashableStake = activeStake_ + withdrawals_ + nextWithdrawals;
-            slashedAmount = Math.min(slashedAmount, slashableStake);
+            slashedAmount = Math.min(amount, slashableStake);
             if (slashedAmount > 0) {
                 uint256 activeSlashed = slashedAmount.mulDiv(activeStake_, slashableStake);
                 uint256 nextWithdrawalsSlashed = slashedAmount.mulDiv(nextWithdrawals, slashableStake);
@@ -265,7 +265,7 @@ contract Vault is VaultStorage, MigratableEntity, AccessControlUpgradeable, IVau
             IERC20(collateral).safeTransfer(burner, slashedAmount);
         }
 
-        emit OnSlash(msg.sender, slashedAmount);
+        emit OnSlash(amount, captureTimestamp, slashedAmount);
     }
 
     /**

src/interfaces/delegator/IBaseDelegator.sol

@@ -40,12 +40,13 @@ interface IBaseDelegator is IEntity {
     event SetMaxNetworkLimit(bytes32 indexed subnetwork, uint256 amount);
 
     /**
-     * @notice Emitted when a slash happened.
+     * @notice Emitted when a slash happens.
      * @param subnetwork full identifier of the subnetwork (address of the network concatenated with the uint96 identifier)
      * @param operator address of the operator
-     * @param slashedAmount amount of the collateral slashed
+     * @param amount amount of the collateral to be slashed
+     * @param captureTimestamp time point when the stake was captured
      */
-    event OnSlash(bytes32 indexed subnetwork, address indexed operator, uint256 slashedAmount);
+    event OnSlash(bytes32 indexed subnetwork, address indexed operator, uint256 amount, uint48 captureTimestamp);
 
     /**
      * @notice Emitted when a hook is set.
@@ -174,15 +175,15 @@ interface IBaseDelegator is IEntity {
      * @notice Called when a slash happens.
      * @param subnetwork full identifier of the subnetwork (address of the network concatenated with the uint96 identifier)
      * @param operator address of the operator
-     * @param slashedAmount amount of the collateral slashed
+     * @param amount amount of the collateral slashed
      * @param captureTimestamp time point when the stake was captured
      * @param data some additional data
      * @dev Only the vault's slasher can call this function.
      */
     function onSlash(
         bytes32 subnetwork,
         address operator,
-        uint256 slashedAmount,
+        uint256 amount,
         uint48 captureTimestamp,
         bytes calldata data
     ) external;

src/interfaces/delegator/IDelegatorHook.sol

@@ -6,14 +6,14 @@ interface IDelegatorHook {
      * @notice Called when a slash happens.
      * @param subnetwork full identifier of the subnetwork (address of the network concatenated with the uint96 identifier)
      * @param operator address of the operator
-     * @param slashedAmount amount of the collateral slashed
+     * @param amount amount of the collateral to be slashed
      * @param captureTimestamp time point when the stake was captured
      * @param data some additional data
      */
     function onSlash(
         bytes32 subnetwork,
         address operator,
-        uint256 slashedAmount,
+        uint256 amount,
         uint48 captureTimestamp,
         bytes calldata data
     ) external;

src/interfaces/slasher/ISlasher.sol

@@ -17,7 +17,7 @@ interface ISlasher {
      * @notice Emitted when a slash is performed.
      * @param subnetwork subnetwork that requested the slash
      * @param operator operator that is slashed
-     * @param slashedAmount amount of the collateral slashed
+     * @param slashedAmount virtual amount of the collateral slashed
      * @param captureTimestamp time point when the stake was captured
      */
     event Slash(bytes32 indexed subnetwork, address indexed operator, uint256 slashedAmount, uint48 captureTimestamp);
@@ -29,7 +29,7 @@ interface ISlasher {
      * @param amount maximum amount of the collateral to be slashed
      * @param captureTimestamp time point when the stake was captured
      * @param hints hints for checkpoints' indexes
-     * @return slashedAmount amount of the collateral slashed
+     * @return slashedAmount virtual amount of the collateral slashed
      * @dev Only a network middleware can call this function.
      */
     function slash(

src/interfaces/slasher/IVetoSlasher.sol

@@ -102,7 +102,7 @@ interface IVetoSlasher {
     /**
      * @notice Emitted when a slash request is executed.
      * @param slashIndex index of the slash request
-     * @param slashedAmount amount of the collateral slashed
+     * @param slashedAmount virtual amount of the collateral slashed
      */
     event ExecuteSlash(uint256 indexed slashIndex, uint256 slashedAmount);
 
@@ -207,7 +207,7 @@ interface IVetoSlasher {
      * @notice Execute a slash with a given slash index using hints.
      * @param slashIndex index of the slash request
      * @param hints hints for checkpoints' indexes
-     * @return slashedAmount amount of the collateral slashed
+     * @return slashedAmount virtual amount of the collateral slashed
      * @dev Only a network middleware can call this function.
      */
     function executeSlash(uint256 slashIndex, bytes calldata hints) external returns (uint256 slashedAmount);

src/interfaces/vault/IVault.sol

@@ -124,11 +124,12 @@ interface IVault is IMigratableEntity, IVaultStorage {
     event ClaimBatch(address indexed claimer, address indexed recipient, uint256[] epochs, uint256 amount);
 
     /**
-     * @notice Emitted when a slash happened.
-     * @param slasher address of the slasher
-     * @param slashedAmount amount of the collateral slashed
+     * @notice Emitted when a slash happens.
+     * @param amount amount of the collateral to slash
+     * @param captureTimestamp time point when the stake was captured
+     * @param slashedAmount real amount of the collateral slashed
      */
-    event OnSlash(address indexed slasher, uint256 slashedAmount);
+    event OnSlash(uint256 amount, uint48 captureTimestamp, uint256 slashedAmount);
 
     /**
      * @notice Emitted when a deposit whitelist status is enabled/disabled.
@@ -223,7 +224,7 @@ interface IVault is IMigratableEntity, IVaultStorage {
      * @notice Deposit collateral into the vault.
      * @param onBehalfOf account the deposit is made on behalf of
      * @param amount amount of the collateral to deposit
-     * @return depositedAmount amount of the collateral deposited
+     * @return depositedAmount real amount of the collateral deposited
      * @return mintedShares amount of the active shares minted
      */
     function deposit(
@@ -267,11 +268,12 @@ interface IVault is IMigratableEntity, IVaultStorage {
 
     /**
      * @notice Slash callback for burning collateral.
-     * @param slashedAmount amount to slash
+     * @param amount amount to slash
      * @param captureTimestamp time point when the stake was captured
+     * @return slashedAmount real amount of the collateral slashed
      * @dev Only the slasher can call this function.
      */
-    function onSlash(uint256 slashedAmount, uint48 captureTimestamp) external;
+    function onSlash(uint256 amount, uint48 captureTimestamp) external returns (uint256 slashedAmount);
 
     /**
      * @notice Enable/disable deposit whitelist.