- Refactored validation logic of liquidationCall() and repayWithCollateral() to ValidationLogic.

contracts/lendingpool/LendingPool.sol

@@ -385,7 +385,6 @@ contract LendingPool is VersionedInitializable, ILendingPool {
     uint256 purchaseAmount,
     bool receiveAToken
   ) external override {
-    ValidationLogic.validateLiquidation(_reserves[collateral], _reserves[asset]);
     
     address liquidationManager = _addressesProvider.getLendingPoolLiquidationManager();
 
@@ -446,8 +445,6 @@ contract LendingPool is VersionedInitializable, ILendingPool {
     require(!_flashLiquidationLocked, Errors.REENTRANCY_NOT_ALLOWED);
     _flashLiquidationLocked = true;
 
-    ValidationLogic.validateLiquidation(_reserves[collateral], _reserves[principal]);
-
     address liquidationManager = _addressesProvider.getLendingPoolLiquidationManager();
 
     //solium-disable-next-line

contracts/lendingpool/LendingPoolLiquidationManager.sol

@@ -21,6 +21,7 @@ import {PercentageMath} from '../libraries/math/PercentageMath.sol';
 import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {ISwapAdapter} from '../interfaces/ISwapAdapter.sol';
 import {Errors} from '../libraries/helpers/Errors.sol';
+import {ValidationLogic} from '../libraries/logic/ValidationLogic.sol';
 
 /**
  * @title LendingPoolLiquidationManager contract
@@ -88,15 +89,6 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
     uint256 swappedCollateralAmount
   );
 
-  enum LiquidationErrors {
-    NO_ERROR,
-    NO_COLLATERAL_AVAILABLE,
-    COLLATERAL_CANNOT_BE_LIQUIDATED,
-    CURRRENCY_NOT_BORROWED,
-    HEALTH_FACTOR_ABOVE_THRESHOLD,
-    NOT_ENOUGH_LIQUIDITY
-  }
-
   struct LiquidationCallLocalVars {
     uint256 userCollateralBalance;
     uint256 userStableDebt;
@@ -112,6 +104,9 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
     uint256 healthFactor;
     IAToken collateralAtoken;
     bool isCollateralEnabled;
+    address principalAToken;
+    uint256 errorCode;
+    string errorMsg;
   }
 
   /**
@@ -138,8 +133,8 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
     uint256 purchaseAmount,
     bool receiveAToken
   ) external returns (uint256, string memory) {
-    ReserveLogic.ReserveData storage principalReserve = reserves[principal];
     ReserveLogic.ReserveData storage collateralReserve = reserves[collateral];
+    ReserveLogic.ReserveData storage principalReserve = reserves[principal];
     UserConfiguration.Map storage userConfig = usersConfig[user];
 
     LiquidationCallLocalVars memory vars;
@@ -152,43 +147,29 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
       addressesProvider.getPriceOracle()
     );
 
-    if (vars.healthFactor >= GenericLogic.HEALTH_FACTOR_LIQUIDATION_THRESHOLD) {
-      return (
-        uint256(LiquidationErrors.HEALTH_FACTOR_ABOVE_THRESHOLD),
-        Errors.HEALTH_FACTOR_NOT_BELOW_THRESHOLD
-      );
-    }
-
-    vars.collateralAtoken = IAToken(collateralReserve.aTokenAddress);
-
-    vars.userCollateralBalance = vars.collateralAtoken.balanceOf(user);
-
-    vars.isCollateralEnabled =
-      collateralReserve.configuration.getLiquidationThreshold() > 0 &&
-      userConfig.isUsingAsCollateral(collateralReserve.index);
-
-    //if collateral isn't enabled as collateral by user, it cannot be liquidated
-    if (!vars.isCollateralEnabled) {
-      return (
-        uint256(LiquidationErrors.COLLATERAL_CANNOT_BE_LIQUIDATED),
-        Errors.COLLATERAL_CANNOT_BE_LIQUIDATED
-      );
-    }
-
     //if the user hasn't borrowed the specific currency defined by asset, it cannot be liquidated
     (vars.userStableDebt, vars.userVariableDebt) = Helpers.getUserCurrentDebt(
       user,
       principalReserve
     );
 
-    if (vars.userStableDebt == 0 && vars.userVariableDebt == 0) {
-      return (
-        uint256(LiquidationErrors.CURRRENCY_NOT_BORROWED),
-        Errors.SPECIFIED_CURRENCY_NOT_BORROWED_BY_USER
-      );
+    (vars.errorCode, vars.errorMsg) = ValidationLogic.validateLiquidationCall(
+      collateralReserve,
+      principalReserve,
+      userConfig,
+      vars.healthFactor,
+      vars.userStableDebt,
+      vars.userVariableDebt
+    );
+
+    if (Errors.LiquidationErrors(vars.errorCode) != Errors.LiquidationErrors.NO_ERROR) {
+      return (vars.errorCode, vars.errorMsg);
     }
 
-    //all clear - calculate the max principal amount that can be liquidated
+    vars.collateralAtoken = IAToken(collateralReserve.aTokenAddress);
+
+    vars.userCollateralBalance = vars.collateralAtoken.balanceOf(user);
+
     vars.maxPrincipalAmountToLiquidate = vars.userStableDebt.add(vars.userVariableDebt).percentMul(
       LIQUIDATION_CLOSE_FACTOR_PERCENT
     );
@@ -224,7 +205,7 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
       );
       if (currentAvailableCollateral < vars.maxCollateralToLiquidate) {
         return (
-          uint256(LiquidationErrors.NOT_ENOUGH_LIQUIDITY),
+          uint256(Errors.LiquidationErrors.NOT_ENOUGH_LIQUIDITY),
           Errors.NOT_ENOUGH_LIQUIDITY_TO_LIQUIDATE
         );
       }
@@ -291,7 +272,7 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
       receiveAToken
     );
 
-    return (uint256(LiquidationErrors.NO_ERROR), Errors.NO_ERRORS);
+    return (uint256(Errors.LiquidationErrors.NO_ERROR), Errors.NO_ERRORS);
   }
 
   /**
@@ -314,9 +295,8 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
     address receiver,
     bytes calldata params
   ) external returns (uint256, string memory) {
-    ReserveLogic.ReserveData storage debtReserve = reserves[principal];
     ReserveLogic.ReserveData storage collateralReserve = reserves[collateral];
-
+    ReserveLogic.ReserveData storage debtReserve = reserves[principal];
     UserConfiguration.Map storage userConfig = usersConfig[user];
 
     LiquidationCallLocalVars memory vars;
@@ -329,36 +309,20 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
       addressesProvider.getPriceOracle()
     );
 
-    if (
-      msg.sender != user && vars.healthFactor >= GenericLogic.HEALTH_FACTOR_LIQUIDATION_THRESHOLD
-    ) {
-      return (
-        uint256(LiquidationErrors.HEALTH_FACTOR_ABOVE_THRESHOLD),
-        Errors.HEALTH_FACTOR_NOT_BELOW_THRESHOLD
-      );
-    }
-
-    if (msg.sender != user) {
-      vars.isCollateralEnabled =
-        collateralReserve.configuration.getLiquidationThreshold() > 0 &&
-        userConfig.isUsingAsCollateral(collateralReserve.index);
-
-      //if collateral isn't enabled as collateral by user, it cannot be liquidated
-      if (!vars.isCollateralEnabled) {
-        return (
-          uint256(LiquidationErrors.COLLATERAL_CANNOT_BE_LIQUIDATED),
-          Errors.COLLATERAL_CANNOT_BE_LIQUIDATED
-        );
-      }
-    }
-
     (vars.userStableDebt, vars.userVariableDebt) = Helpers.getUserCurrentDebt(user, debtReserve);
 
-    if (vars.userStableDebt == 0 && vars.userVariableDebt == 0) {
-      return (
-        uint256(LiquidationErrors.CURRRENCY_NOT_BORROWED),
-        Errors.SPECIFIED_CURRENCY_NOT_BORROWED_BY_USER
-      );
+    (vars.errorCode, vars.errorMsg) = ValidationLogic.validateRepayWithCollateral(
+      collateralReserve,
+      debtReserve,
+      userConfig,
+      user,
+      vars.healthFactor,
+      vars.userStableDebt,
+      vars.userVariableDebt
+    );
+
+    if (Errors.LiquidationErrors(vars.errorCode) != Errors.LiquidationErrors.NO_ERROR) {
+      return (vars.errorCode, vars.errorMsg);
     }
 
     vars.maxPrincipalAmountToLiquidate = vars.userStableDebt.add(vars.userVariableDebt);
@@ -397,7 +361,7 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
       usersConfig[user].setUsingAsCollateral(collateralReserve.index, false);
     }
 
-    address principalAToken = debtReserve.aTokenAddress;
+    vars.principalAToken = debtReserve.aTokenAddress;
 
     // Notifies the receiver to proceed, sending as param the underlying already transferred
     ISwapAdapter(receiver).executeOperation(
@@ -410,8 +374,8 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
 
     //updating debt reserve
     debtReserve.updateCumulativeIndexesAndTimestamp();
-    debtReserve.updateInterestRates(principal, principalAToken, vars.actualAmountToLiquidate, 0);
-    IERC20(principal).transferFrom(receiver, principalAToken, vars.actualAmountToLiquidate);
+    debtReserve.updateInterestRates(principal, vars.principalAToken, vars.actualAmountToLiquidate, 0);
+    IERC20(principal).transferFrom(receiver, vars.principalAToken, vars.actualAmountToLiquidate);
 
     if (vars.userVariableDebt >= vars.actualAmountToLiquidate) {
       IVariableDebtToken(debtReserve.variableDebtTokenAddress).burn(
@@ -443,7 +407,7 @@ contract LendingPoolLiquidationManager is VersionedInitializable {
       vars.maxCollateralToLiquidate
     );
 
-    return (uint256(LiquidationErrors.NO_ERROR), Errors.NO_ERRORS);
+    return (uint256(Errors.LiquidationErrors.NO_ERROR), Errors.NO_ERRORS);
   }
 
   struct AvailableCollateralToLiquidateLocalVars {

contracts/libraries/helpers/Errors.sol

@@ -76,4 +76,14 @@ library Errors {
   string public constant MULTIPLICATION_OVERFLOW = '44';
   string public constant ADDITION_OVERFLOW = '45';
   string public constant DIVISION_BY_ZERO = '46';
+
+  enum LiquidationErrors {
+    NO_ERROR,
+    NO_COLLATERAL_AVAILABLE,
+    COLLATERAL_CANNOT_BE_LIQUIDATED,
+    CURRRENCY_NOT_BORROWED,
+    HEALTH_FACTOR_ABOVE_THRESHOLD,
+    NOT_ENOUGH_LIQUIDITY,
+    NO_ACTIVE_RESERVE
+  }
 }

contracts/libraries/logic/ValidationLogic.sol

@@ -13,6 +13,7 @@ import {ReserveConfiguration} from '../configuration/ReserveConfiguration.sol';
 import {UserConfiguration} from '../configuration/UserConfiguration.sol';
 import {IPriceOracleGetter} from '../../interfaces/IPriceOracleGetter.sol';
 import {Errors} from '../helpers/Errors.sol';
+import {Helpers} from '../helpers/Helpers.sol';
 
 /**
  * @title ReserveLogic library
@@ -331,18 +332,114 @@ library ValidationLogic {
   }
 
   /**
-   * @dev Validates configurations for liquidation actions, both liquidationCall() and repayWithCollateral()
+   * @dev Validates the liquidationCall() action
    * @param collateralReserve The reserve data of the collateral
    * @param principalReserve The reserve data of the principal
+   * @param userConfig The user configuration
+   * @param userHealthFactor The user's health factor
+   * @param userStableDebt Total stable debt balance of the user
+   * @param userVariableDebt Total variable debt balance of the user
    **/
-  function validateLiquidation(
+  function validateLiquidationCall(
     ReserveLogic.ReserveData storage collateralReserve,
-    ReserveLogic.ReserveData storage principalReserve
-  ) internal view {
-    require(
-        collateralReserve.configuration.getActive() && 
-        principalReserve.configuration.getActive(), 
-      Errors.NO_ACTIVE_RESERVE
-    );
+    ReserveLogic.ReserveData storage principalReserve,
+    UserConfiguration.Map storage userConfig,
+    uint256 userHealthFactor,
+    uint256 userStableDebt,
+    uint256 userVariableDebt
+  ) internal view returns(uint256, string memory) {
+    if ( !collateralReserve.configuration.getActive() || !principalReserve.configuration.getActive()) {
+      return (
+        uint256(Errors.LiquidationErrors.NO_ACTIVE_RESERVE),
+        Errors.NO_ACTIVE_RESERVE
+      );
+    }
+
+    if (userHealthFactor >= GenericLogic.HEALTH_FACTOR_LIQUIDATION_THRESHOLD) {
+      return (
+        uint256(Errors.LiquidationErrors.HEALTH_FACTOR_ABOVE_THRESHOLD),
+        Errors.HEALTH_FACTOR_NOT_BELOW_THRESHOLD
+      );
+    }
+
+    bool isCollateralEnabled =
+      collateralReserve.configuration.getLiquidationThreshold() > 0 &&
+      userConfig.isUsingAsCollateral(collateralReserve.index);
+
+    //if collateral isn't enabled as collateral by user, it cannot be liquidated
+    if (!isCollateralEnabled) {
+      return (
+        uint256(Errors.LiquidationErrors.COLLATERAL_CANNOT_BE_LIQUIDATED),
+        Errors.COLLATERAL_CANNOT_BE_LIQUIDATED
+      );
+    }
+
+    if (userStableDebt == 0 && userVariableDebt == 0) {
+      return (
+        uint256(Errors.LiquidationErrors.CURRRENCY_NOT_BORROWED),
+        Errors.SPECIFIED_CURRENCY_NOT_BORROWED_BY_USER
+      );
+    }
+
+    return (uint256(Errors.LiquidationErrors.NO_ERROR), Errors.NO_ERRORS);
+  }
+
+  /**
+   * @dev Validates the repayWithCollateral() action
+   * @param collateralReserve The reserve data of the collateral
+   * @param principalReserve The reserve data of the principal
+   * @param userConfig The user configuration
+   * @param user The address of the user
+   * @param userHealthFactor The user's health factor
+   * @param userStableDebt Total stable debt balance of the user
+   * @param userVariableDebt Total variable debt balance of the user
+   **/
+  function validateRepayWithCollateral(
+    ReserveLogic.ReserveData storage collateralReserve,
+    ReserveLogic.ReserveData storage principalReserve,
+    UserConfiguration.Map storage userConfig,
+    address user,
+    uint256 userHealthFactor,
+    uint256 userStableDebt,
+    uint256 userVariableDebt
+  ) internal view returns(uint256, string memory) {
+    if ( !collateralReserve.configuration.getActive() || !principalReserve.configuration.getActive()) {
+      return (
+        uint256(Errors.LiquidationErrors.NO_ACTIVE_RESERVE),
+        Errors.NO_ACTIVE_RESERVE
+      );
+    }
+
+    if (
+      msg.sender != user && userHealthFactor >= GenericLogic.HEALTH_FACTOR_LIQUIDATION_THRESHOLD
+    ) {
+      return (
+        uint256(Errors.LiquidationErrors.HEALTH_FACTOR_ABOVE_THRESHOLD),
+        Errors.HEALTH_FACTOR_NOT_BELOW_THRESHOLD
+      );
+    }
+
+    if (msg.sender != user) {
+      bool isCollateralEnabled =
+        collateralReserve.configuration.getLiquidationThreshold() > 0 &&
+        userConfig.isUsingAsCollateral(collateralReserve.index);
+
+      //if collateral isn't enabled as collateral by user, it cannot be liquidated
+      if (!isCollateralEnabled) {
+        return (
+          uint256(Errors.LiquidationErrors.COLLATERAL_CANNOT_BE_LIQUIDATED),
+          Errors.COLLATERAL_CANNOT_BE_LIQUIDATED
+        );
+      }
+    }
+
+    if (userStableDebt == 0 && userVariableDebt == 0) {
+      return (
+        uint256(Errors.LiquidationErrors.CURRRENCY_NOT_BORROWED),
+        Errors.SPECIFIED_CURRENCY_NOT_BORROWED_BY_USER
+      );
+    }
+
+    return (uint256(Errors.LiquidationErrors.NO_ERROR), Errors.NO_ERRORS);
   }
 }