add borrowRateMode check on credit delegation

contracts/lendingpool/LendingPool.sol

@@ -167,11 +167,8 @@ contract LendingPool is VersionedInitializable, ILendingPool {
     address asset,
     uint256 interestRateMode
   ) external override view returns (uint256) {
-    address debtToken = ReserveLogic.InterestRateMode.STABLE ==
+    return
-      ReserveLogic.InterestRateMode(interestRateMode)
+      _borrowAllowance[_reserves[asset].getDebtTokenAddress(interestRateMode)][fromUser][toUser];
-      ? _reserves[asset].stableDebtTokenAddress
-      : _reserves[asset].variableDebtTokenAddress;
-    return _borrowAllowance[debtToken][fromUser][toUser];
   }
 
   function delegateBorrowAllowance(
@@ -180,10 +177,8 @@ contract LendingPool is VersionedInitializable, ILendingPool {
     uint256 interestRateMode,
     uint256 amount
   ) external override {
-    address debtToken = ReserveLogic.InterestRateMode.STABLE ==
+    address debtToken = _reserves[asset].getDebtTokenAddress(interestRateMode);
-      ReserveLogic.InterestRateMode(interestRateMode)
+
-      ? _reserves[asset].stableDebtTokenAddress
-      : _reserves[asset].variableDebtTokenAddress;
     _borrowAllowance[debtToken][msg.sender][user] = amount;
     emit BorrowAllowanceDelegated(asset, msg.sender, user, interestRateMode, amount);
   }
@@ -206,10 +201,7 @@ contract LendingPool is VersionedInitializable, ILendingPool {
     ReserveLogic.ReserveData storage reserve = _reserves[asset];
 
     if (onBehalfOf != msg.sender) {
-      address debtToken = ReserveLogic.InterestRateMode.STABLE ==
+      address debtToken = reserve.getDebtTokenAddress(interestRateMode);
-        ReserveLogic.InterestRateMode(interestRateMode)
-        ? reserve.stableDebtTokenAddress
-        : reserve.variableDebtTokenAddress;
 
       _borrowAllowance[debtToken][onBehalfOf][msg
         .sender] = _borrowAllowance[debtToken][onBehalfOf][msg.sender].sub(

contracts/libraries/logic/ReserveLogic.sol

@@ -116,6 +116,22 @@ library ReserveLogic {
     return cumulated;
   }
 
+  function getDebtTokenAddress(ReserveLogic.ReserveData storage reserve, uint256 interestRateMode)
+    internal
+    view
+    returns (address)
+  {
+    require(
+      ReserveLogic.InterestRateMode.STABLE == ReserveLogic.InterestRateMode(interestRateMode) ||
+        ReserveLogic.InterestRateMode.VARIABLE == ReserveLogic.InterestRateMode(interestRateMode),
+      Errors.INVALID_INTEREST_RATE_MODE_SELECTED
+    );
+    return
+      ReserveLogic.InterestRateMode.STABLE == ReserveLogic.InterestRateMode(interestRateMode)
+        ? reserve.stableDebtTokenAddress
+        : reserve.variableDebtTokenAddress;
+  }
+
   /**
    * @dev Updates the liquidity cumulative index Ci and variable borrow cumulative index Bvc. Refer to the whitepaper for
    * a formal specification.

test/helpers/actions.ts

@@ -284,19 +284,27 @@ export const delegateBorrowAllowance = async (
   interestRateMode: string,
   user: SignerWithAddress,
   receiver: tEthereumAddress,
-  testEnv: TestEnv
+  expectedResult: string,
+  testEnv: TestEnv,
+  revertMessage?: string
 ) => {
   const {pool} = testEnv;
 
   const reserve = await getReserveAddressFromSymbol(reserveSymbol);
   const amountToDelegate = await convertToCurrencyDecimals(reserve, amount);
 
-  await pool
+  const delegateAllowancePromise = pool
     .connect(user.signer)
     .delegateBorrowAllowance(receiver, reserve, interestRateMode, amountToDelegate.toString());
-  expect(
+  if (expectedResult === 'revert') {
-    (await pool.getBorrowAllowance(user.address, receiver, reserve, interestRateMode)).toString()
+    await expect(delegateAllowancePromise, revertMessage).to.be.reverted;
-  ).to.be.equal(amountToDelegate.toString(), 'borrowAllowance are set incorrectly');
+    return;
+  } else {
+    await delegateAllowancePromise;
+    expect(
+      (await pool.getBorrowAllowance(user.address, receiver, reserve, interestRateMode)).toString()
+    ).to.be.equal(amountToDelegate.toString(), 'borrowAllowance are set incorrectly');
+  }
 };
 
 export const borrow = async (

test/helpers/scenario-engine.ts

@@ -111,7 +111,16 @@ const executeAction = async (action: Action, users: SignerWithAddress[], testEnv
           throw `Invalid amount to deposit into the ${reserve} reserve`;
         }
 
-        await delegateBorrowAllowance(reserve, amount, rateMode, user, toUser, testEnv);
+        await delegateBorrowAllowance(
+          reserve,
+          amount,
+          rateMode,
+          user,
+          toUser,
+          expected,
+          testEnv,
+          revertMessage
+        );
       }
       break;
 

test/helpers/scenarios/credit-delegation.json

@@ -73,7 +73,7 @@
       ]
     },
     {
-      "description": "User 0 delegates borrowing of 1 WETH to user 4, user 4 borrows 3 WETH on behalf of user 0, revert expected",
+      "description": "User 0 delegates borrowing of 1 WETH to user 4, user 4 borrows 3 WETH variable on behalf of user 0, revert expected",
       "actions": [
         {
           "name": "delegateBorrowAllowance",
@@ -81,6 +81,7 @@
             "reserve": "WETH",
             "amount": "1",
             "user": "0",
+            "borrowRateMode": "variable",
             "toUser": "4"
           },
           "expected": "success"
@@ -125,6 +126,23 @@
           "expected": "success"
         }
       ]
+    },
+    {
+      "description": "User 0 delegates borrowing of 1 WETH to user 2 with wrong borrowRateMode, revert expected",
+      "actions": [
+        {
+          "name": "delegateBorrowAllowance",
+          "args": {
+            "reserve": "WETH",
+            "amount": "1",
+            "user": "0",
+            "borrowRateMode": "random",
+            "toUser": "2"
+          },
+          "expected": "revert",
+          "revertMessage": "8"
+        }
+      ]
     }
   ]
 }