refactor: further refactored the caching logic

contracts/protocol/lendingpool/LendingPool.sol

@@ -49,6 +49,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
   using WadRayMath for uint256;
   using PercentageMath for uint256;
   using SafeERC20 for IERC20;
+  using ReserveLogic for DataTypes.ReserveCache;
 
   uint256 public constant LENDINGPOOL_REVISION = 0x2;
 
@@ -288,40 +289,26 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
 
     if (interestRateMode == DataTypes.InterestRateMode.STABLE) {
       IStableDebtToken(reserveCache.stableDebtTokenAddress).burn(msg.sender, stableDebt);
-
-      reserveCache.nextPrincipalStableDebt = reserveCache.nextTotalStableDebt = reserveCache
-        .currTotalStableDebt
-        .sub(stableDebt);
-
       IVariableDebtToken(reserveCache.variableDebtTokenAddress).mint(
         msg.sender,
         msg.sender,
         stableDebt,
         reserveCache.nextVariableBorrowIndex
       );
-      reserveCache.nextScaledVariableDebt = reserveCache.currScaledVariableDebt.add(
-        stableDebt.rayDiv(reserveCache.nextVariableBorrowIndex)
-      );
+      reserveCache.refreshDebt(0, stableDebt, stableDebt, 0);
     } else {
       IVariableDebtToken(reserveCache.variableDebtTokenAddress).burn(
         msg.sender,
         variableDebt,
         reserveCache.nextVariableBorrowIndex
       );
-      reserveCache.nextScaledVariableDebt = reserveCache.currScaledVariableDebt.sub(
-        variableDebt.rayDiv(reserveCache.nextVariableBorrowIndex)
-      );
-
       IStableDebtToken(reserveCache.stableDebtTokenAddress).mint(
         msg.sender,
         msg.sender,
         variableDebt,
         reserve.currentStableBorrowRate
       );
-
-      reserveCache.nextPrincipalStableDebt = reserveCache.nextTotalStableDebt = reserveCache
-        .currTotalStableDebt
-        .add(stableDebt);
+      reserveCache.refreshDebt(variableDebt, 0, 0, variableDebt);
     }
 
     reserve.updateInterestRates(reserveCache, asset, 0, 0);
@@ -365,6 +352,8 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
       reserve.currentStableBorrowRate
     );
 
+    reserveCache.refreshDebt(stableDebt, stableDebt, 0, 0);
+
     reserve.updateInterestRates(reserveCache, asset, 0, 0);
 
     emit RebalanceStableBorrowRate(asset, user);
@@ -915,8 +904,8 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     );
 
     uint256 currentStableRate = 0;
-
     bool isFirstBorrowing = false;
+
     if (DataTypes.InterestRateMode(vars.interestRateMode) == DataTypes.InterestRateMode.STABLE) {
       currentStableRate = reserve.currentStableBorrowRate;
 
@@ -926,11 +915,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
         vars.amount,
         currentStableRate
       );
-
-      reserveCache.nextPrincipalStableDebt = reserveCache.nextTotalStableDebt = reserveCache
-        .currTotalStableDebt
-        .add(vars.amount);
-      
+      reserveCache.refreshDebt(vars.amount, 0, 0, 0);
     } else {
       isFirstBorrowing = IVariableDebtToken(reserveCache.variableDebtTokenAddress).mint(
         vars.user,
@@ -938,10 +923,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
         vars.amount,
         reserveCache.nextVariableBorrowIndex
       );
-
-      reserveCache.nextScaledVariableDebt = reserveCache.nextScaledVariableDebt.add(
-        vars.amount.rayDiv(reserveCache.nextVariableBorrowIndex)
-      );
+      reserveCache.refreshDebt(0, 0, vars.amount, 0);
     }
 
     if (isFirstBorrowing) {
@@ -1090,18 +1072,14 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
 
     if (interestRateMode == DataTypes.InterestRateMode.STABLE) {
       IStableDebtToken(reserveCache.stableDebtTokenAddress).burn(onBehalfOf, paybackAmount);
-      reserveCache.nextPrincipalStableDebt = reserveCache.nextTotalStableDebt = reserveCache
-        .currTotalStableDebt
-        .sub(paybackAmount);
+      reserveCache.refreshDebt(0, paybackAmount, 0, 0);
     } else {
       IVariableDebtToken(reserveCache.variableDebtTokenAddress).burn(
         onBehalfOf,
         paybackAmount,
         reserveCache.nextVariableBorrowIndex
       );
-      reserveCache.nextScaledVariableDebt = reserveCache.currScaledVariableDebt.sub(
-        paybackAmount.rayDiv(reserveCache.nextVariableBorrowIndex)
-      );
+      reserveCache.refreshDebt(0, 0, 0, paybackAmount);
     }
 
     reserve.updateInterestRates(reserveCache, asset, paybackAmount, 0);

contracts/protocol/lendingpool/LendingPoolCollateralManager.sol

@@ -10,6 +10,7 @@ import {IPriceOracleGetter} from '../../interfaces/IPriceOracleGetter.sol';
 import {ILendingPoolCollateralManager} from '../../interfaces/ILendingPoolCollateralManager.sol';
 import {VersionedInitializable} from '../libraries/aave-upgradeability/VersionedInitializable.sol';
 import {GenericLogic} from '../libraries/logic/GenericLogic.sol';
+import {ReserveLogic} from '../libraries/logic/ReserveLogic.sol';
 import {Helpers} from '../libraries/helpers/Helpers.sol';
 import {WadRayMath} from '../libraries/math/WadRayMath.sol';
 import {PercentageMath} from '../libraries/math/PercentageMath.sol';
@@ -35,6 +36,7 @@ contract LendingPoolCollateralManager is
   using SafeMath for uint256;
   using WadRayMath for uint256;
   using PercentageMath for uint256;
+  using ReserveLogic for DataTypes.ReserveCache;
 
   uint256 internal constant LIQUIDATION_CLOSE_FACTOR_PERCENT = 5000;
 
@@ -173,9 +175,8 @@ contract LendingPoolCollateralManager is
         vars.actualDebtToLiquidate,
         debtReserveCache.nextVariableBorrowIndex
       );
-      debtReserveCache.nextScaledVariableDebt = debtReserveCache.currScaledVariableDebt.sub(
-        vars.actualDebtToLiquidate.rayDiv(debtReserveCache.nextVariableBorrowIndex)
-      );
+      debtReserveCache.refreshDebt(0, 0, 0, vars.actualDebtToLiquidate);
+      debtReserve.updateInterestRates(debtReserveCache, debtAsset, vars.actualDebtToLiquidate, 0);
     } else {
       // If the user doesn't have variable debt, no need to try to burn variable debt tokens
       if (vars.userVariableDebt > 0) {
@@ -184,27 +185,20 @@ contract LendingPoolCollateralManager is
           vars.userVariableDebt,
           debtReserveCache.nextVariableBorrowIndex
         );
-        debtReserveCache.nextScaledVariableDebt = debtReserveCache
-          .currScaledVariableDebt
-          .sub(vars.userVariableDebt.rayDiv(debtReserveCache.nextVariableBorrowIndex));
       }
       IStableDebtToken(debtReserveCache.stableDebtTokenAddress).burn(
         user,
         vars.actualDebtToLiquidate.sub(vars.userVariableDebt)
       );
-
-      debtReserveCache.nextPrincipalStableDebt = debtReserveCache
-        .nextTotalStableDebt = debtReserveCache.currTotalStableDebt.sub(
-        vars.actualDebtToLiquidate.sub(vars.userVariableDebt)
+      debtReserveCache.refreshDebt(
+        0,
+        vars.actualDebtToLiquidate.sub(vars.userVariableDebt),
+        0,
+        vars.userVariableDebt
       );
-    }
 
-    debtReserve.updateInterestRates(
-      debtReserveCache,
-      debtAsset,
-      vars.actualDebtToLiquidate,
-      0
-    );
+      debtReserve.updateInterestRates(debtReserveCache, debtAsset, vars.actualDebtToLiquidate, 0);
+    }
 
     if (receiveAToken) {
       vars.liquidatorPreviousATokenBalance = IERC20(vars.collateralAtoken).balanceOf(msg.sender);
@@ -216,7 +210,7 @@ contract LendingPoolCollateralManager is
         emit ReserveUsedAsCollateralEnabled(collateralAsset, msg.sender);
       }
     } else {
-       collateralReserve.updateState(collateralReserveCache);
+      collateralReserve.updateState(collateralReserveCache);
       collateralReserve.updateInterestRates(
         collateralReserveCache,
         collateralAsset,

contracts/protocol/libraries/logic/ReserveLogic.sol

@@ -186,10 +186,6 @@ library ReserveLogic {
   ) internal {
     UpdateInterestRatesLocalVars memory vars;
 
-    if (reserveCache.currTotalStableDebt != reserveCache.nextTotalStableDebt) {
-      reserveCache.nextAvgStableBorrowRate = IStableDebtToken(reserveCache.stableDebtTokenAddress)
-        .getAverageStableRate();
-    }
 
     reserveCache.nextTotalVariableDebt = reserveCache.nextScaledVariableDebt.rayMul(
       reserveCache.nextVariableBorrowIndex
@@ -228,11 +224,9 @@ library ReserveLogic {
   }
 
   struct MintToTreasuryLocalVars {
-    uint256 currentStableDebt;
-    uint256 principalStableDebt;
-    uint256 previousStableDebt;
-    uint256 currentVariableDebt;
-    uint256 previousVariableDebt;
+    uint256 prevTotalStableDebt;
+    uint256 prevTotalVariableDebt;
+    uint256 currTotalVariableDebt;
     uint256 avgStableRate;
     uint256 cumulatedStableInterest;
     uint256 totalDebtAccrued;
@@ -260,12 +254,12 @@ library ReserveLogic {
     }
 
     //calculate the last principal variable debt
-    vars.previousVariableDebt = reserveCache.currScaledVariableDebt.rayMul(
+    vars.prevTotalVariableDebt = reserveCache.currScaledVariableDebt.rayMul(
       reserveCache.currVariableBorrowIndex
     );
 
     //calculate the new total supply after accumulation of the index
-    vars.currentVariableDebt = reserveCache.currScaledVariableDebt.rayMul(
+    vars.currTotalVariableDebt = reserveCache.currScaledVariableDebt.rayMul(
       reserveCache.nextVariableBorrowIndex
     );
 
@@ -276,16 +270,16 @@ library ReserveLogic {
       reserveCache.reserveLastUpdateTimestamp
     );
 
-    vars.previousStableDebt = reserveCache.currPrincipalStableDebt.rayMul(
+    vars.prevTotalStableDebt = reserveCache.currPrincipalStableDebt.rayMul(
       vars.cumulatedStableInterest
     );
 
     //debt accrued is the sum of the current debt minus the sum of the debt at the last update
     vars.totalDebtAccrued = vars
-      .currentVariableDebt
+      .currTotalVariableDebt
       .add(reserveCache.currTotalStableDebt)
-      .sub(vars.previousVariableDebt)
-      .sub(vars.previousStableDebt);
+      .sub(vars.prevTotalVariableDebt)
+      .sub(vars.prevTotalStableDebt);
 
     vars.amountToMint = vars.totalDebtAccrued.percentMul(vars.reserveFactor);
 
@@ -385,4 +379,32 @@ library ReserveLogic {
 
     return reserveCache;
   }
+
+  function refreshDebt(
+    DataTypes.ReserveCache memory cache,
+    uint256 stableDebtMinted,
+    uint256 stableDebtBurned,
+    uint256 variableDebtMinted,
+    uint256 variableDebtBurned
+  ) internal {
+    uint256 scaledVariableDebtMinted = variableDebtMinted.rayDiv(cache.nextVariableBorrowIndex);
+    uint256 scaledVariableDebtBurned = variableDebtBurned.rayDiv(cache.nextVariableBorrowIndex);
+
+    if (cache.currTotalStableDebt.add(stableDebtMinted) > stableDebtBurned) {
+      cache.nextPrincipalStableDebt = cache.nextTotalStableDebt = cache
+        .currTotalStableDebt
+        .add(stableDebtMinted)
+        .sub(stableDebtBurned);
+      if (stableDebtMinted != 0 || stableDebtBurned != 0) {
+        cache.nextAvgStableBorrowRate = IStableDebtToken(cache.stableDebtTokenAddress)
+          .getAverageStableRate();
+      }
+    } else {
+      cache.nextPrincipalStableDebt = cache.nextTotalStableDebt = cache.nextAvgStableBorrowRate = 0;
+    }
+
+    cache.nextScaledVariableDebt = cache.currScaledVariableDebt.add(scaledVariableDebtMinted).sub(
+      scaledVariableDebtBurned
+    );
+  }
 }

package-lock.json

@@ -14793,7 +14793,7 @@
               }
             },
             "ethereumjs-abi": {
-              "version": "git+https://github.com/ethereumjs/ethereumjs-abi.git#1a27c59c15ab1e95ee8e5c4ed6ad814c49cc439e",
+              "version": "git+https://github.com/ethereumjs/ethereumjs-abi.git#ee3994657fa7a427238e6ba92a84d0b529bbcde0",
               "from": "git+https://github.com/ethereumjs/ethereumjs-abi.git",
               "dev": true,
               "requires": {