Merge pull request #184 from unioncredit/feature/uni-2213-interest-pa…

…yment-on-base-is-wrong fix: interest calc error when borrow more than once
unioncredit · Dec 9, 2024 · 063829e · 063829e
2 parents 7a0a034 + a340007
commit 063829e
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Showing 2 changed files with 18 additions and 2 deletions.
diff --git a/contracts/market/UToken.sol b/contracts/market/UToken.sol
@@ -640,8 +640,9 @@ contract UToken is IUToken, Controller, ERC20PermitUpgradeable, ReentrancyGuardU
         if (totalBorrowsNew > _debtCeiling) revert AmountExceedGlobalMax();
 
         // Update internal balances
-        uint256 newPrincipal = actualAmount + fee;
-        accountBorrows[msg.sender].principal += newPrincipal;
+        accountBorrows[msg.sender].principal += actualAmount + fee;
+        uint256 newPrincipal = _getBorrowed(msg.sender);
+
         accountBorrows[msg.sender].interest = accountBorrowsNew - newPrincipal;
         accountBorrows[msg.sender].interestIndex = borrowIndex;
         _totalBorrows = totalBorrowsNew;

diff --git a/test/foundry/uToken/TestBorrowRepay.t.sol b/test/foundry/uToken/TestBorrowRepay.t.sol
@@ -67,6 +67,21 @@ contract TestBorrowRepay is TestUTokenBase {
         assertEq(borrowed, realBorrowAmount + fees);
     }
 
+    function testBorrowTwoTimes() public {
+        vm.startPrank(ALICE);
+        uint256 originationFee = uToken.originationFee();
+        uint256 borrowRatePerSecond = uToken.borrowRatePerSecond();
+        uToken.borrow(ALICE, 1 * UNIT);
+        uToken.borrow(ALICE, 1 * UNIT);
+        skip(block.timestamp);
+        uint256 interest = uToken.calculatingInterest(ALICE);
+        uint256 borrowed = 2 * UNIT;
+        uint256 fee = (borrowed * 10 ** (18 - tokenDecimals) * originationFee) / 1e18;
+        uint256 expectInterest = ((borrowed + fee) * borrowRatePerSecond) / 1e18; //1 sec
+        assertEq(interest, expectInterest);
+        vm.stopPrank();
+    }
+
     function testRepayBorrow(uint256 borrowAmount) public {
         vm.assume(borrowAmount >= MIN_BORROW && borrowAmount < MAX_BORROW - (MAX_BORROW * ORIGINATION_FEE) / 1e18);