feat: added drop reserve main capability

contracts/interfaces/ILendingPool.sol

@@ -396,6 +396,8 @@ interface ILendingPool {
     address interestRateStrategyAddress
   ) external;
 
+  function dropReserve(address reserve) external;
+
   function setReserveInterestRateStrategyAddress(address reserve, address rateStrategyAddress)
     external;
 

contracts/protocol/lendingpool/LendingPool.sol

@@ -665,15 +665,29 @@ 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;
   }
 
   /**
@@ -783,6 +797,16 @@ 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
@@ -1067,7 +1091,7 @@ 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);
@@ -1075,10 +1099,18 @@ 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

@@ -161,6 +161,10 @@ contract LendingPoolConfigurator is VersionedInitializable, ILendingPoolConfigur
     );
   }
 
+  function dropReserve(address asset) external onlyPoolAdmin {
+    pool.dropReserve(asset);
+  }
+
   /**
    * @dev Updates the aToken implementation for the reserve
    **/

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;

contracts/protocol/libraries/logic/ValidationLogic.sol

@@ -119,7 +119,7 @@ library ValidationLogic {
     mapping(uint256 => address) storage reserves,
     uint256 reservesCount,
     address oracle
-  ) internal view {
+  ) external view {
     ValidateBorrowLocalVars memory vars;
 
     (

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

@@ -267,6 +267,7 @@ const buildTestEnv = async (deployer: Signer, secondaryWallet: Signer) => {
   );
 
   await configureReservesByHelper(reservesParams, allReservesAddresses, testHelpers, admin);
+  lendingPoolConfiguratorProxy.dropReserve(mockTokens.KNC.address);
 
   const collateralManager = await deployLendingPoolCollateralManager();
   await waitForTx(