chore(sgho): set supply cap at initialization

Author: adamazad

src/contracts/extensions/sgho/interfaces/IsGHO.sol

@@ -45,6 +45,11 @@ interface IsGHO {
    */
   error RateMustBeLessThanMaxRate();
 
+  /**
+   * @notice Thrown when a deposit or mint would exceed the total supply cap.
+   */
+  error SupplyCapExceeded();
+
   // --- Events ---
 
   /**
@@ -53,6 +58,20 @@ interface IsGHO {
    */
   event TargetRateUpdated(uint256 newRate);
 
+  /**
+   * @notice Emitted when ERC20 tokens are rescued from the contract.
+   * @param caller The address that initiated the rescue operation.
+   * @param token The address of the rescued ERC20 token.
+   * @param to The recipient address of the rescued tokens.
+   * @param amount The amount of tokens rescued.
+   */
+  event ERC20Rescued(
+    address indexed caller,
+    address indexed token,
+    address indexed to,
+    uint256 amount
+  );
+
   // --- State Variables (as view functions) ---
 
   /**
@@ -61,6 +80,12 @@ interface IsGHO {
    */
   function gho() external view returns (address);
 
+  /**
+   * @notice Returns the total supply cap of the vault.
+   * @return The total supply cap.
+   */
+  function supplyCap() external view returns (uint256);
+
   /**
    * @notice Returns the chain ID of the network where the contract is deployed.
    * @dev This is used for EIP-712 signature validation to prevent replay attacks across different chains.
@@ -116,7 +141,12 @@ interface IsGHO {
    * @dev This function can only be called once. It sets up initial roles and configurations.
    * While the function is marked as `payable`, it is designed to reject any attached Ether value.
    */
-  function initialize(address gho_, address aclManager_, uint256 maxTargetRate_) external payable;
+  function initialize(
+    address gho_,
+    address aclManager_,
+    uint256 maxTargetRate_,
+    uint256 supplyCap_
+  ) external payable;
 
   /**
    * @notice Overload of the standard ERC20Permit `permit` function.
@@ -166,20 +196,6 @@ interface IsGHO {
 
   // --- Events ---
 
-  /**
-   * @notice Emitted when ERC20 tokens are rescued from the contract.
-   * @param caller The address that initiated the rescue operation.
-   * @param token The address of the rescued ERC20 token.
-   * @param to The recipient address of the rescued tokens.
-   * @param amount The amount of tokens rescued.
-   */
-  event ERC20Rescued(
-    address indexed caller,
-    address indexed token,
-    address indexed to,
-    uint256 amount
-  );
-
   /**
    * @notice The receive function is implemented to reject direct Ether transfers to the contract.
    */

src/contracts/extensions/sgho/sGHO.sol

@@ -27,6 +27,7 @@ contract sGHO is Initializable, ERC4626Upgradeable, ERC20PermitUpgradeable, IsGH
 
   uint256 public targetRate;
   uint256 public maxTargetRate;
+  uint256 public supplyCap;
   uint256 public yieldIndex;
   uint256 public lastUpdate;
   uint256 internal constant RATE_PRECISION = 1e10;
@@ -51,11 +52,13 @@ contract sGHO is Initializable, ERC4626Upgradeable, ERC20PermitUpgradeable, IsGH
    * @param _gho       Address of the underlying GHO token.
    * @param _aclmanager Address of the Aave ACL Manager.
    * @param _maxTargetRate The maximum allowable target rate.
+   * @param _supplyCap The total supply cap for the vault.
    */
   function initialize(
     address _gho,
     address _aclmanager,
-    uint256 _maxTargetRate
+    uint256 _maxTargetRate,
+    uint256 _supplyCap
   ) public payable initializer {
     __ERC20_init('sGHO', 'sGHO');
     __ERC4626_init(IERC20(_gho));
@@ -64,6 +67,7 @@ contract sGHO is Initializable, ERC4626Upgradeable, ERC20PermitUpgradeable, IsGH
     gho = _gho;
     aclManager = IAccessControl(_aclmanager);
     maxTargetRate = _maxTargetRate;
+    supplyCap = _supplyCap;
 
     deploymentChainId = block.chainid;
     yieldIndex = WadRayMath.RAY;
@@ -178,6 +182,22 @@ contract sGHO is Initializable, ERC4626Upgradeable, ERC20PermitUpgradeable, IsGH
     );
   }
 
+  function maxDeposit(address) public view override(ERC4626Upgradeable) returns (uint256) {
+    uint256 currentAssets = totalAssets();
+    if (currentAssets >= supplyCap) {
+      return 0;
+    }
+    return supplyCap - currentAssets;
+  }
+
+  function maxMint(address) public view override(ERC4626Upgradeable) returns (uint256) {
+    uint256 currentAssets = totalAssets();
+    if (currentAssets >= supplyCap) {
+      return 0;
+    }
+    return convertToShares(supplyCap - currentAssets);
+  }
+
   /**
    * @notice Deposits GHO into the vault and mints sGHO shares to the receiver.
    * @dev The yield index is updated before the deposit to ensure correct share calculation.

tests/extensions/sgho/sGHO.t.sol

@@ -36,6 +36,7 @@ contract sGhoTest is TestnetProcedures {
   address internal yManager; // Yield manager user
 
   uint256 internal constant MAX_TARGET_RATE = 5000; // 50%
+  uint256 internal constant SUPPLY_CAP = 1_000_000 ether; // 1M GHO
 
   // Permit constants
   string internal constant VERSION = '1'; // Matches sGHO constructor
@@ -66,7 +67,8 @@ contract sGhoTest is TestnetProcedures {
               sGHO.initialize.selector,
               address(gho),
               address(contracts.aclManager),
-              MAX_TARGET_RATE
+              MAX_TARGET_RATE,
+              SUPPLY_CAP
             )
           )
         )
@@ -302,18 +304,28 @@ contract sGhoTest is TestnetProcedures {
   }
 
   function test_4626_maxMethods() external {
-    // Deposit max checks (no limits implemented in this sGHO version)
-    assertEq(sgho.maxDeposit(user1), type(uint256).max, 'maxDeposit should be max');
-    assertEq(sgho.maxMint(user1), type(uint256).max, 'maxMint should be max');
+    // Max deposit should be the supply cap initially
+    assertEq(sgho.maxDeposit(user1), SUPPLY_CAP, 'maxDeposit should be supply cap');
 
-    // Withdraw max checks
+    // Max mint should correspond to the supply cap
+    uint256 expectedMaxMint = sgho.convertToShares(SUPPLY_CAP);
+    assertEq(sgho.maxMint(user1), expectedMaxMint, 'maxMint should be supply cap in shares');
+
+    // Deposit some amount and check max withdraw/redeem
     vm.startPrank(user1);
     uint256 depositAmount = 100 ether;
     sgho.deposit(depositAmount, user1);
     uint256 shares = sgho.balanceOf(user1);
 
     assertEq(sgho.maxWithdraw(user1), depositAmount, 'maxWithdraw mismatch');
     assertEq(sgho.maxRedeem(user1), shares, 'maxRedeem mismatch');
+
+    // Max deposit should be reduced by the deposited amount
+    assertEq(
+      sgho.maxDeposit(user1),
+      SUPPLY_CAP - depositAmount,
+      'maxDeposit should be reduced'
+    );
     vm.stopPrank();
   }
 
@@ -359,6 +371,51 @@ contract sGhoTest is TestnetProcedures {
     vm.stopPrank();
   }
 
+  // --- Supply Cap Tests ---
+  function test_revert_deposit_exceedsCap() external {
+    vm.startPrank(user1);
+    uint256 amount = SUPPLY_CAP + 1;
+    vm.expectRevert(
+      abi.encodeWithSelector(
+        ERC4626.ERC4626ExceededMaxDeposit.selector,
+        user1,
+        amount,
+        SUPPLY_CAP
+      )
+    );
+    sgho.deposit(amount, user1);
+    vm.stopPrank();
+  }
+
+  function test_revert_mint_exceedsCap() external {
+    vm.startPrank(user1);
+    uint256 shares = sgho.convertToShares(SUPPLY_CAP) + 1;
+    uint256 maxShares = sgho.maxMint(user1);
+    vm.expectRevert(
+      abi.encodeWithSelector(
+        ERC4626.ERC4626ExceededMaxMint.selector,
+        user1,
+        shares,
+        maxShares
+      )
+    );
+    sgho.mint(shares, user1);
+    vm.stopPrank();
+  }
+
+  function test_deposit_atCap() external {
+    vm.startPrank(user1);
+    sgho.deposit(SUPPLY_CAP, user1);
+    assertEq(sgho.totalAssets(), SUPPLY_CAP, 'Total assets should equal supply cap');
+    // The contract balance will be the supply cap plus the 1 GHO donated in setUp
+    assertEq(
+      gho.balanceOf(address(sgho)),
+      SUPPLY_CAP + 1 ether,
+      'Contract balance should be supply cap + initial donation'
+    );
+    vm.stopPrank();
+  }
+
   // --- Yield Integration Tests (_updateVault) ---
 
   function test_yield_claimSavingsIntegration(uint256 depositAmount, uint64 timeSkip) external {
@@ -790,7 +847,8 @@ contract sGhoTest is TestnetProcedures {
               sGHO.initialize.selector,
               address(gho),
               address(contracts.aclManager),
-              MAX_TARGET_RATE
+              MAX_TARGET_RATE,
+              SUPPLY_CAP
             )
           )
         )
@@ -811,15 +869,21 @@ contract sGhoTest is TestnetProcedures {
         sGHO.initialize.selector,
         address(gho),
         address(contracts.aclManager),
-        MAX_TARGET_RATE
+        MAX_TARGET_RATE,
+        SUPPLY_CAP
       )
     );
 
     sGHO newSgho = sGHO(payable(address(proxy)));
 
     // Should revert on second initialization via proxy
     vm.expectRevert();
-    newSgho.initialize(address(gho), address(contracts.aclManager), MAX_TARGET_RATE);
+    newSgho.initialize(
+      address(gho),
+      address(contracts.aclManager),
+      MAX_TARGET_RATE,
+      SUPPLY_CAP
+    );
   }
 
   function _wadPow(uint256 base, uint256 exp) internal pure returns (uint256) {