feat: added drop reserve main capability

contracts/interfaces/ILendingPool.sol

@@ -168,14 +168,11 @@ interface ILendingPool {
   );
 
   /**
-  * @dev Emitted when the protocol treasury receives minted aTokens from the accrued interest.
-  * @param reserve the address of the reserve
-  * @param amountMinted the amount minted to the treasury
-  **/
-  event MintedToTreasury(
-    address indexed reserve,
-    uint256 amountMinted
-  );
+   * @dev Emitted when the protocol treasury receives minted aTokens from the accrued interest.
+   * @param reserve the address of the reserve
+   * @param amountMinted the amount minted to the treasury
+   **/
+  event MintedToTreasury(address indexed reserve, uint256 amountMinted);
 
   /**
    * @dev Deposits an `amount` of underlying asset into the reserve, receiving in return overlying aTokens.
@@ -406,6 +403,8 @@ interface ILendingPool {
     address interestRateStrategyAddress
   ) external;
 
+  function dropReserve(address reserve) external;
+
   function setReserveInterestRateStrategyAddress(address reserve, address rateStrategyAddress)
     external;
 

contracts/protocol/lendingpool/LendingPool.sol

@@ -545,11 +545,11 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
   function mintToTreasury(address[] calldata reserves) public {
     for (uint256 i = 0; i < reserves.length; i++) {
       address reserveAddress = reserves[i];
-      
+
       DataTypes.ReserveData storage reserve = _reserves[reserveAddress];
 
       // this cover both inactive reserves and invalid reserves since the flag will be 0 for both
-      if(!reserve.configuration.getActive()){
+      if (!reserve.configuration.getActive()) {
         continue;
       }
 
@@ -690,15 +690,29 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
   }
 
   /**
-   * @dev Returns the list of the initialized reserves
+   * @dev Returns the list of the initialized reserves, does not contain dropped reserves
    **/
   function getReservesList() external view override returns (address[] memory) {
-    address[] memory _activeReserves = new address[](_reservesCount);
+    uint256 reserveListCount = _reservesCount;
+    uint256 droppedReservesCount = 0;
+    address[] memory reserves = new address[](reserveListCount);
 
-    for (uint256 i = 0; i < _reservesCount; i++) {
-      _activeReserves[i] = _reservesList[i];
+    for (uint256 i = 0; i < reserveListCount; i++) {
+      if (_reservesList[i] != address(0)) {
+        reserves[i - droppedReservesCount] = _reservesList[i];
+      } else {
+        droppedReservesCount++;
+      }
     }
-    return _activeReserves;
+
+    if (droppedReservesCount == 0) return reserves;
+
+    address[] memory undroppedReserves = new address[](reserveListCount - droppedReservesCount);
+    for (uint256 i = 0; i < reserveListCount - droppedReservesCount; i++) {
+      undroppedReserves[i] = reserves[i];
+    }
+
+    return undroppedReserves;
   }
 
   /**
@@ -808,6 +822,16 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     _addReserveToList(asset);
   }
 
+  /**
+   * @dev Drop a reserve
+   * - Only callable by the LendingPoolConfigurator contract
+   * @param asset The address of the underlying asset of the reserve
+   **/
+  function dropReserve(address asset) external override onlyLendingPoolConfigurator {
+    _reserves[asset].dropReserve();
+    _removeReserveFromList(asset);
+  }
+
   /**
    * @dev Updates the address of the interest rate strategy contract
    * - Only callable by the LendingPoolConfigurator contract
@@ -1084,7 +1108,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     return paybackAmount;
   }
 
-  function _addReserveToList(address asset) internal {
+  function _addReserveToList(address asset) internal returns (uint8) {
     uint256 reservesCount = _reservesCount;
 
     require(reservesCount < _maxNumberOfReserves, Errors.LP_NO_MORE_RESERVES_ALLOWED);
@@ -1092,10 +1116,18 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     bool reserveAlreadyAdded = _reserves[asset].id != 0 || _reservesList[0] == asset;
 
     if (!reserveAlreadyAdded) {
-      _reserves[asset].id = uint8(reservesCount);
-      _reservesList[reservesCount] = asset;
-
-      _reservesCount = reservesCount + 1;
+      for (uint8 i = 0; i <= reservesCount; i++) {
+        if (_reservesList[i] == address(0)) {
+          _reserves[asset].id = i;
+          _reservesList[i] = asset;
+          _reservesCount = reservesCount + 1;
+          return i;
+        }
+      }
     }
   }
+
+  function _removeReserveFromList(address asset) internal {
+    _reservesList[_reserves[asset].id] = address(0);
+  }
 }

contracts/protocol/lendingpool/LendingPoolConfigurator.sol

@@ -159,6 +159,11 @@ contract LendingPoolConfigurator is VersionedInitializable, ILendingPoolConfigur
     );
   }
 
+  /// @inheritdoc ILendingPoolConfigurator
+  function dropReserve(address asset) external onlyPoolAdmin {
+    _pool.dropReserve(asset);
+  }
+
   /// @inheritdoc ILendingPoolConfigurator
   function updateAToken(UpdateATokenInput calldata input) external override onlyPoolAdmin {
     ILendingPool cachedPool = _pool;

contracts/protocol/libraries/helpers/Errors.sol

@@ -109,6 +109,9 @@ library Errors {
   string public constant LPC_CALLER_NOT_EMERGENCY_OR_POOL_ADMIN = '85';
   string public constant VL_RESERVE_PAUSED = '86';
   string public constant LPC_CALLER_NOT_RISK_OR_POOL_ADMIN = '87';
+  string public constant RL_ATOKEN_SUPPLY_NOT_NULL = '88';
+  string public constant RL_STABLE_DEBT_NOT_NULL = '89';
+  string public constant RL_VARIABLE_DEBT_SUPPLY_NOT_NULL = '90';
 
   enum CollateralManagerErrors {
     NO_ERROR,

contracts/protocol/libraries/logic/ReserveLogic.sol

@@ -178,6 +178,23 @@ library ReserveLogic {
     reserve.interestRateStrategyAddress = interestRateStrategyAddress;
   }
 
+  /**
+   * @dev drop a reserve
+   * @param reserve The reserve object
+   **/
+  function dropReserve(DataTypes.ReserveData storage reserve) external {
+    require(IERC20(reserve.aTokenAddress).totalSupply() == 0, Errors.RL_ATOKEN_SUPPLY_NOT_NULL);
+    require(
+      IERC20(reserve.stableDebtTokenAddress).totalSupply() == 0,
+      Errors.RL_STABLE_DEBT_NOT_NULL
+    );
+    require(
+      IERC20(reserve.variableDebtTokenAddress).totalSupply() == 0,
+      Errors.RL_VARIABLE_DEBT_SUPPLY_NOT_NULL
+    );
+    reserve.id = type(uint8).max;
+  }
+
   struct UpdateInterestRatesLocalVars {
     address stableDebtTokenAddress;
     uint256 availableLiquidity;
@@ -320,7 +337,9 @@ library ReserveLogic {
     vars.amountToMint = vars.totalDebtAccrued.percentMul(vars.reserveFactor);
 
     if (vars.amountToMint != 0) {
-      reserve.accruedToTreasury = reserve.accruedToTreasury.add(vars.amountToMint.rayDiv(newLiquidityIndex));
+      reserve.accruedToTreasury = reserve.accruedToTreasury.add(
+        vars.amountToMint.rayDiv(newLiquidityIndex)
+      );
     }
   }
 

test-suites/test-aave/__setup.spec.ts

@@ -265,6 +265,7 @@ const buildTestEnv = async (deployer: Signer, secondaryWallet: Signer) => {
   );
 
   await configureReservesByHelper(reservesParams, allReservesAddresses, testHelpers, admin);
+  lendingPoolConfiguratorProxy.dropReserve(mockTokens.KNC.address);
 
   const collateralManager = await deployLendingPoolCollateralManager();
   await waitForTx(