Readded calculateAvailableBorrowsETH

contracts/interfaces/ILendingPool.sol

@@ -367,6 +367,7 @@ interface ILendingPool {
     returns (
       uint256 totalCollateralETH,
       uint256 totalBorrowsETH,
+      uint256 availableBorrowsETH,
       uint256 currentLiquidationThreshold,
       uint256 ltv,
       uint256 healthFactor

contracts/lendingpool/LendingPool.sol

@@ -29,7 +29,6 @@ import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {ILendingPool} from '../interfaces/ILendingPool.sol';
 import {LendingPoolStorage} from './LendingPoolStorage.sol';
 import {IReserveInterestRateStrategy} from '../interfaces/IReserveInterestRateStrategy.sol';
-
 /**
  * @title LendingPool contract
  * @notice Implements the actions of the LendingPool, and exposes accessory methods to fetch the users and reserve data
@@ -161,6 +160,14 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     emit Withdraw(asset, msg.sender, amount);
   }
 
+  /**
+   * @dev returns the borrow allowance of the user
+   * @param asset The underlying asset of the debt token
+   * @param fromUser The user to giving allowance
+   * @param toUser The user to give allowance to
+   * @param interestRateMode Type of debt: 1 for stable, 2 for variable
+   * @return the current allowance of toUser
+   **/
   function getBorrowAllowance(
     address fromUser,
     address toUser,
@@ -363,15 +370,13 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
 
     IERC20 stableDebtToken = IERC20(reserve.stableDebtTokenAddress);
     IERC20 variableDebtToken = IERC20(reserve.variableDebtTokenAddress);
+    address aTokenAddress = reserve.aTokenAddress;
 
     uint256 stableBorrowBalance = IERC20(stableDebtToken).balanceOf(user);
 
-    // user must be borrowing on asset at a stable rate
-    require(stableBorrowBalance > 0, Errors.NOT_ENOUGH_STABLE_BORROW_BALANCE);
-
     //if the utilization rate is below 95%, no rebalances are needed
     uint256 totalBorrows = stableDebtToken.totalSupply().add(variableDebtToken.totalSupply()).wadToRay();
-    uint256 availableLiquidity = IERC20(asset).balanceOf(reserve.aTokenAddress).wadToRay();
+    uint256 availableLiquidity = IERC20(asset).balanceOf(aTokenAddress).wadToRay();
     uint256 usageRatio = totalBorrows == 0
       ? 0
       : totalBorrows.rayDiv(availableLiquidity.add(totalBorrows));
@@ -398,11 +403,10 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     IStableDebtToken(address(stableDebtToken)).burn(user, stableBorrowBalance);
     IStableDebtToken(address(stableDebtToken)).mint(user, stableBorrowBalance, reserve.currentStableBorrowRate);
 
-    reserve.updateInterestRates(asset, reserve.aTokenAddress, 0, 0);
+    reserve.updateInterestRates(asset, aTokenAddress, 0, 0);
 
     emit RebalanceStableBorrowRate(asset, user);
 
-    return;
   }
 
   /**
@@ -731,6 +735,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     returns (
       uint256 totalCollateralETH,
       uint256 totalBorrowsETH,
+      uint256 availableBorrowsETH,
       uint256 currentLiquidationThreshold,
       uint256 ltv,
       uint256 healthFactor
@@ -749,6 +754,12 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
       _reservesList,
       _addressesProvider.getPriceOracle()
     );
+    
+    availableBorrowsETH = GenericLogic.calculateAvailableBorrowsETH(
+      totalCollateralETH,
+      totalBorrowsETH,
+      ltv
+    );
   }
 
   function getUserReserveData(address asset, address user)

contracts/libraries/configuration/ReserveConfiguration.sol

@@ -6,7 +6,6 @@ import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 import {ReserveLogic} from '../logic/ReserveLogic.sol';
 import {WadRayMath} from '../math/WadRayMath.sol';
 import {IPriceOracleGetter} from '../../interfaces/IPriceOracleGetter.sol';
-import "@nomiclabs/buidler/console.sol";
 
 /**
  * @title ReserveConfiguration library

contracts/libraries/logic/GenericLogic.sol

@@ -253,4 +253,28 @@ library GenericLogic {
 
     return (collateralBalanceETH.percentMul(liquidationThreshold)).wadDiv(borrowBalanceETH);
   }
+
+    /**
+   * @dev calculates the equivalent amount in ETH that an user can borrow, depending on the available collateral and the
+   * average Loan To Value.
+   * @param collateralBalanceETH the total collateral balance
+   * @param borrowBalanceETH the total borrow balance
+   * @param ltv the average loan to value
+   * @return the amount available to borrow in ETH for the user
+   **/
+
+  function calculateAvailableBorrowsETH(
+    uint256 collateralBalanceETH,
+    uint256 borrowBalanceETH,
+    uint256 ltv
+  ) internal pure returns (uint256) {
+    uint256 availableBorrowsETH = collateralBalanceETH.percentMul(ltv); //ltv is in percentage
+
+    if (availableBorrowsETH < borrowBalanceETH) {
+      return 0;
+    }
+
+    availableBorrowsETH = availableBorrowsETH.sub(borrowBalanceETH);
+    return availableBorrowsETH;
+  }
 }

contracts/tokenization/StableDebtToken.sol

@@ -8,7 +8,6 @@ import {DebtTokenBase} from './base/DebtTokenBase.sol';
 import {MathUtils} from '../libraries/math/MathUtils.sol';
 import {WadRayMath} from '../libraries/math/WadRayMath.sol';
 import {IStableDebtToken} from './interfaces/IStableDebtToken.sol';
-import "@nomiclabs/buidler/console.sol";
 
 /**
  * @title contract StableDebtToken

test/helpers/actions.ts

@@ -636,11 +636,6 @@ export const rebalanceStableBorrowRate = async (
     testEnv
   );
 
-  console.log("avl liquidity ", reserveDataBefore.availableLiquidity.toFixed());
-  console.log("Total borrows stable ", reserveDataBefore.totalStableDebt.toFixed());
-  console.log("Total borrows variable ", reserveDataBefore.totalVariableDebt.toFixed());
-  console.log("Usage ratio ", reserveDataBefore.utilizationRate.toFixed());
-
   if (expectedResult === 'success') {
     const txResult = await waitForTx(
       await pool.connect(user.signer).rebalanceStableBorrowRate(reserve, target.address)

test/helpers/scenarios/rebalance-stable-rate.json

@@ -78,8 +78,8 @@
           "name": "borrow",
           "args": {
             "reserve": "DAI",
-            "amount": "600",
-            "borrowRateMode": "variable",
+            "amount": "250",
+            "borrowRateMode": "stable",
             "user": "1",
             "timeTravel": "365"
           },
@@ -98,14 +98,68 @@
       ]
     },
     {
-      "description": "User 1 swaps to stable, user 0 tries to rebalance but the conditions are not met (revert expected)",
+      "description": "User 1 borrows another 200 at stable, user 0 tries to rebalance but the conditions are not met (revert expected)",
       "actions": [
         {
-          "name": "swapBorrowRateMode",
+          "name": "borrow",
           "args": {
             "reserve": "DAI",
+            "amount": "200",
+            "borrowRateMode": "stable",
             "user": "1",
-            "borrowRateMode": "variable"
+            "timeTravel": "365"
+          },
+          "expected": "success"
+        },
+        {
+          "name": "rebalanceStableBorrowRate",
+          "args": {
+            "reserve": "DAI",
+            "user": "0",
+            "target": "1"
+          },
+          "expected": "revert",
+          "revertMessage": "Interest rate rebalance conditions were not met"
+        }
+      ]
+    },
+    {
+      "description": "User 1 borrows another 200 at stable, user 0 tries to rebalance but the conditions are not met (revert expected)",
+      "actions": [
+        {
+          "name": "borrow",
+          "args": {
+            "reserve": "DAI",
+            "amount": "200",
+            "borrowRateMode": "stable",
+            "user": "1",
+            "timeTravel": "365"
+          },
+          "expected": "success"
+        },
+        {
+          "name": "rebalanceStableBorrowRate",
+          "args": {
+            "reserve": "DAI",
+            "user": "0",
+            "target": "1"
+          },
+          "expected": "revert",
+          "revertMessage": "Interest rate rebalance conditions were not met"
+        }
+      ]
+    },
+    {
+      "description": "User 1 borrows another 100 at stable, user 0 tries to rebalance but the conditions are not met (revert expected)",
+      "actions": [
+        {
+          "name": "borrow",
+          "args": {
+            "reserve": "DAI",
+            "amount": "100",
+            "borrowRateMode": "stable",
+            "user": "1",
+            "timeTravel": "365"
           },
           "expected": "success"
         },
@@ -155,7 +209,7 @@
           "name": "borrow",
           "args": {
             "reserve": "DAI",
-            "amount": "340",
+            "amount": "190",
             "borrowRateMode": "variable",
             "user": "2"
           },

test/scenario.spec.ts

@@ -10,7 +10,7 @@ import {executeStory} from './helpers/scenario-engine';
 
 const scenarioFolder = './test/helpers/scenarios/';
 
-const selectedScenarios: string[] = ['rebalance-stable-rate.json'];
+const selectedScenarios: string[] = [];
 
 fs.readdirSync(scenarioFolder).forEach((file) => {
   if (selectedScenarios.length > 0 && !selectedScenarios.includes(file)) return;