fix: address review feedback on repay approval amount

- Round the approval amount to the token's decimals on both branches of
  getRepayAmountToApprove. The repay input has no decimalScale, so a typed
  7dp amount on a 6dp token made parseUnits throw during render and took the
  modal down. Rounding up keeps the approval at or above the gate's target.
- Key the USDT-on-Ethereum reset check off the amount actually being
  approved rather than signatureAmount, which is the '-1' sentinel on a max
  repay and skipped the check entirely. An exact approval on a max repay
  leaves a residual allowance, and USDT reverts approve() over a non-zero
  allowance, so the next full repay failed at gas estimation.
- Report the approval amount to Amplitude in token units instead of base
  units, matching every other GENERAL.TRANSACTION caller.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: sammdec

src/components/transactions/__tests__/utils.test.ts

@@ -1,4 +1,5 @@
 import { BigNumber } from 'bignumber.js';
+import { parseUnits } from 'ethers/lib/utils';
 
 import { checkRequiresApproval, getRepayAmountToApprove, getSafeAmountToRepayAll } from '../utils';
 
@@ -45,6 +46,32 @@ describe('getRepayAmountToApprove', () => {
     ).toBe('10.5');
   });
 
+  it('trims a typed amount to the token decimals so parseUnits cannot throw', () => {
+    // The repay input has no decimalScale, so 7dp on a 6dp token is reachable by typing.
+    const approved = getRepayAmountToApprove({
+      amountRequiringApproval: '1.1234567',
+      isMaxRepay: false,
+      decimals: 6,
+    });
+
+    expect(approved).toBe('1.123457');
+    expect(() => parseUnits(approved, 6)).not.toThrow();
+  });
+
+  it('rounds a typed amount up, so the trimmed approval still clears the gate', () => {
+    const typed = '1.1234567';
+    const approved = getRepayAmountToApprove({
+      amountRequiringApproval: typed,
+      isMaxRepay: false,
+      decimals: 6,
+    });
+
+    expect(new BigNumber(approved).isGreaterThanOrEqualTo(typed)).toBe(true);
+    expect(
+      checkRequiresApproval({ approvedAmount: approved, amount: typed, signedAmount: '0' })
+    ).toBe(false);
+  });
+
   it('reproduces the reported bug: a hand-set approval above the debt still fails the gate', () => {
     expect(new BigNumber(HAND_SET_APPROVAL).isGreaterThan(DEBT)).toBe(true);
     expect(passesGate(HAND_SET_APPROVAL, DEBT)).toBe(false);

src/components/transactions/utils.ts

@@ -55,15 +55,18 @@ export const getRepayAmountToApprove = ({
   amountRequiringApproval: string;
   isMaxRepay: boolean;
   decimals: number;
-}): string =>
+}): string => {
   // A typed amount is fixed, so the gate's target cannot drift away from it. A full repay
   // is derived from live debt and does drift, hence the margin.
-  isMaxRepay
-    ? valueToBigNumber(amountRequiringApproval)
-        .multipliedBy(REPAY_ALL_APPROVAL_MARGIN)
-        .decimalPlaces(decimals, BigNumber.ROUND_UP)
-        .toString(10)
-    : amountRequiringApproval;
+  const amount = isMaxRepay
+    ? valueToBigNumber(amountRequiringApproval).multipliedBy(REPAY_ALL_APPROVAL_MARGIN)
+    : valueToBigNumber(amountRequiringApproval);
+
+  // The repay input accepts more decimals than the token has, and this result is handed to
+  // `parseUnits` during render, which throws on the excess. Rounding up rather than down
+  // keeps the approval at or above what the gate asked for.
+  return amount.decimalPlaces(decimals, BigNumber.ROUND_UP).toString(10);
+};
 
 export const checkRequiresApproval = ({
   approvedAmount,

src/hooks/useApprovalTx.tsx

@@ -1,7 +1,7 @@
 import { ApproveType, MAX_UINT_AMOUNT, ProtocolAction } from '@aave/contract-helpers';
 import { SignatureLike } from '@ethersproject/bytes';
 import { constants, ethers } from 'ethers';
-import { parseUnits } from 'ethers/lib/utils';
+import { formatUnits, parseUnits } from 'ethers/lib/utils';
 import { useEffect, useState } from 'react';
 import { MOCK_SIGNED_HASH } from 'src/helpers/useTransactionHandler';
 import { useWeb3Context } from 'src/libs/hooks/useWeb3Context';
@@ -68,23 +68,29 @@ export const useApprovalTx = ({
 
   const [requiresApprovalReset, setRequiresApprovalReset] = useState(false);
 
+  // What the next approval will actually be for, in token units. `signatureAmount` is only
+  // a stand-in for it: on a full repay it is the '-1' sentinel, which would skip the check
+  // below even though `amountToApprove` holds a real, finite allowance to compare against.
+  const newApprovalAmount = amountToApprove
+    ? formatUnits(amountToApprove, decimals)
+    : signatureAmount;
+
   // Warning for USDT on Ethereum approval reset
   useEffect(() => {
     if (
       !chainId ||
       !isUSDTOnEthereum(symbol, chainId, underlyingChainId) ||
       !setShowUSDTResetWarning ||
-      !signatureAmount ||
-      signatureAmount === '0' ||
-      signatureAmount === '-1'
+      !newApprovalAmount ||
+      Number(newApprovalAmount) <= 0
     ) {
       return;
     }
 
     const currentApproved = approvedAmount?.amount ?? '0';
 
     if (
-      needsUSDTApprovalReset(symbol, chainId, currentApproved, signatureAmount, underlyingChainId)
+      needsUSDTApprovalReset(symbol, chainId, currentApproved, newApprovalAmount, underlyingChainId)
     ) {
       setShowUSDTResetWarning(true);
       setRequiresApprovalReset(true);
@@ -97,7 +103,7 @@ export const useApprovalTx = ({
     chainId,
     underlyingChainId,
     approvedAmount?.amount,
-    signatureAmount,
+    newApprovalAmount,
     setShowUSDTResetWarning,
   ]);
 
@@ -207,7 +213,7 @@ export const useApprovalTx = ({
             action: ProtocolAction.approval,
             txState: 'success',
             asset: assetAddress,
-            amount: amountToApprove ?? MAX_UINT_AMOUNT,
+            amount: amountToApprove ? formatUnits(amountToApprove, decimals) : MAX_UINT_AMOUNT,
             assetName: symbol,
           });
           if (onApprovalTxConfirmed) {