fix bug with a try catch on approval (#516)

src/components/CurrencyInputPanel/index.js

@@ -20,6 +20,7 @@ import TokenLogo from '../TokenLogo'
 import SearchIcon from '../../assets/images/magnifying-glass.svg'
 import { useTransactionAdder, usePendingApproval } from '../../contexts/Transactions'
 import { useTokenDetails, useAllTokenDetails } from '../../contexts/Tokens'
+import { useAddressBalance } from '../../contexts/Balances'
 import { ReactComponent as Close } from '../../assets/images/x.svg'
 import { transparentize } from 'polished'
 import { Spinner } from '../../theme'
@@ -296,6 +297,10 @@ export default function CurrencyInputPanel({
 
   const allTokens = useAllTokenDetails()
 
+  const { account } = useWeb3Context()
+
+  const userTokenBalance = useAddressBalance(account, selectedTokenAddress)
+
   function renderUnlockButton() {
     if (disableUnlock || !showUnlock || selectedTokenAddress === 'ETH' || !selectedTokenAddress) {
       return null
@@ -304,14 +309,26 @@ export default function CurrencyInputPanel({
         return (
           <SubCurrencySelect
             onClick={async () => {
-              const estimatedGas = await tokenContract.estimate.approve(
-                selectedTokenExchangeAddress,
-                ethers.constants.MaxUint256
-              )
-              tokenContract
-                .approve(selectedTokenExchangeAddress, ethers.constants.MaxUint256, {
-                  gasLimit: calculateGasMargin(estimatedGas, GAS_MARGIN)
+              let estimatedGas
+              let useUserBalance = false
+              estimatedGas = await tokenContract.estimate
+                .approve(selectedTokenExchangeAddress, ethers.constants.MaxUint256)
+                .catch(e => {
+                  console.log('Error setting max token approval.')
                 })
+              if (!estimatedGas) {
+                // general fallback for tokens who restrict approval amounts
+                estimatedGas = await tokenContract.estimate.approve(selectedTokenExchangeAddress, userTokenBalance)
+                useUserBalance = true
+              }
+              tokenContract
+                .approve(
+                  selectedTokenExchangeAddress,
+                  useUserBalance ? userTokenBalance : ethers.constants.MaxUint256,
+                  {
+                    gasLimit: calculateGasMargin(estimatedGas, GAS_MARGIN)
+                  }
+                )
                 .then(response => {
                   addTransaction(response, { approval: selectedTokenAddress })
                 })

src/pages/Pool/AddLiquidity.js

@@ -551,6 +551,7 @@ export default function AddLiquidity({ params }) {
   }, [inputValueParsed, inputBalance, outputValueMax, outputBalance, t])
 
   const allowance = useAddressAllowance(account, outputCurrency, exchangeAddress)
+
   const [showUnlock, setShowUnlock] = useState(false)
   useEffect(() => {
     if (outputValueParsed && allowance) {