fix: communicate correct premium in case of debt-bearing flashloan (#822)

* pick: cherry-pick fl fix from #820

* Update test-suites/pool-flashloan.spec.ts

* Update contracts/protocol/libraries/logic/FlashLoanLogic.sol

Author: sakulstra

contracts/protocol/libraries/logic/FlashLoanLogic.sol

@@ -91,7 +91,10 @@ library FlashLoanLogic {
 
     for (vars.i = 0; vars.i < params.assets.length; vars.i++) {
       vars.currentAmount = params.amounts[vars.i];
-      vars.totalPremiums[vars.i] = vars.currentAmount.percentMul(vars.flashloanPremiumTotal);
+      vars.totalPremiums[vars.i] = DataTypes.InterestRateMode(params.interestRateModes[vars.i]) ==
+        DataTypes.InterestRateMode.NONE
+        ? vars.currentAmount.percentMul(vars.flashloanPremiumTotal)
+        : 0;
       IAToken(reservesData[params.assets[vars.i]].aTokenAddress).transferUnderlyingTo(
         params.receiverAddress,
         vars.currentAmount

test-suites/pool-flashloan.spec.ts

@@ -176,7 +176,7 @@ makeSuite('Pool: FlashLoan', (testEnv: TestEnv) => {
     }
   });
 
-  it('Takes an authorized AAVE flash loan with mode = 0, returns the funds correctly', async () => {
+  it('Takes an authorized AAVE flash loan with mode = 0, returns the funds correctly, premium should be 0', async () => {
     const {
       pool,
       helpersContract,
@@ -194,17 +194,21 @@ makeSuite('Pool: FlashLoan', (testEnv: TestEnv) => {
 
     const totalLiquidityBefore = reserveData.totalAToken;
 
-    await pool
-      .connect(authorizedUser.signer)
-      .flashLoan(
-        _mockFlashLoanReceiver.address,
-        [aave.address],
-        [flashBorrowedAmount],
-        [0],
-        _mockFlashLoanReceiver.address,
-        '0x10',
-        '0'
-      );
+    await expect(
+      pool
+        .connect(authorizedUser.signer)
+        .flashLoan(
+          _mockFlashLoanReceiver.address,
+          [aave.address],
+          [flashBorrowedAmount],
+          [0],
+          _mockFlashLoanReceiver.address,
+          '0x10',
+          '0'
+        )
+    )
+      .to.emit(_mockFlashLoanReceiver, 'ExecutedWithSuccess')
+      .withArgs([aave.address], [flashBorrowedAmount], [0]);
 
     await pool.mintToTreasury([aave.address]);
 
@@ -570,7 +574,7 @@ makeSuite('Pool: FlashLoan', (testEnv: TestEnv) => {
     ).to.be.revertedWith(COLLATERAL_BALANCE_IS_ZERO);
   });
 
-  it('Caller deposits 5 WETH as collateral, Takes a USDC flashloan with mode = 2, does not return the funds. A loan for caller is created', async () => {
+  it('Caller deposits 5 WETH as collateral, Takes a USDC flashloan with mode = 2, does not return the funds. A loan for caller is created, premium should be 0', async () => {
     const { usdc, pool, weth, users, helpersContract } = testEnv;
 
     const caller = users[2];
@@ -585,21 +589,26 @@ makeSuite('Pool: FlashLoan', (testEnv: TestEnv) => {
 
     await pool.connect(caller.signer).deposit(weth.address, amountToDeposit, caller.address, '0');
 
-    await _mockFlashLoanReceiver.setFailExecutionTransfer(true);
-
     const flashloanAmount = await convertToCurrencyDecimals(usdc.address, '500');
 
-    await pool
-      .connect(caller.signer)
-      .flashLoan(
-        _mockFlashLoanReceiver.address,
-        [usdc.address],
-        [flashloanAmount],
-        [2],
-        caller.address,
-        '0x10',
-        '0'
-      );
+    await _mockFlashLoanReceiver.setFailExecutionTransfer(false);
+
+    await expect(
+      pool
+        .connect(caller.signer)
+        .flashLoan(
+          _mockFlashLoanReceiver.address,
+          [usdc.address],
+          [flashloanAmount],
+          [2],
+          caller.address,
+          '0x10',
+          '0'
+        )
+    )
+      .to.emit(_mockFlashLoanReceiver, 'ExecutedWithSuccess')
+      .withArgs([usdc.address], [flashloanAmount], [0]);
+
     const { variableDebtTokenAddress } = await helpersContract.getReserveTokensAddresses(
       usdc.address
     );