error "sending a transaction requires a signer" when calling a constant method

const ethersProvider = new ethers.providers.InfuraProvider("ropsten", infuraKey); contract = new ethers.Contract(contractAddress, abi, ethersProvider) contract.balanceOfUnderlying(fromAddress)

The code above errors out with Error: sending a transaction requires a signer (operation="sendTransaction", code=UNSUPPORTED_OPERATION, version=contracts/5.0.5) but I’m not entirely sure why. I’ve instantiated the contract passing the contract’s address, abi and an Infura provider (in this order).

Any thoughts? I’m currently in the process of migrating from web3.js to ethers.js so maybe I’m missing something. Other constant method calls are working with the Infura provider, without a signer.

Contract ABI

JSON.parse(`[{"inputs":[{"internalType":"address","name":"underlying_","type":"address"},{"internalType":"contractComptrollerInterface","name":"comptroller_","type":"address"},{"internalType":"contractInterestRateModel","name":"interestRateModel_","type":"address"},{"internalType":"uint256","name":"initialExchangeRateMantissa_","type":"uint256"},{"internalType":"string","name":"name_","type":"string"},{"internalType":"string","name":"symbol_","type":"string"},{"internalType":"uint8","name":"decimals_","type":"uint8"},{"internalType":"addresspayable","name":"admin_","type":"address"},{"internalType":"address","name":"implementation_","type":"address"},{"internalType":"bytes","name":"becomeImplementationData","type":"bytes"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"cashPrior","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"interestAccumulated","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"borrowIndex","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"totalBorrows","type":"uint256"}],"name":"AccrueInterest","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"spender","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"borrower","type":"address"},{"indexed":false,"internalType":"uint256","name":"borrowAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"accountBorrows","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"totalBorrows","type":"uint256"}],"name":"Borrow","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"error","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"info","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"detail","type":"uint256"}],"name":"Failure","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"liquidator","type":"address"},{"indexed":false,"internalType":"address","name":"borrower","type":"address"},{"indexed":false,"internalType":"uint256","name":"repayAmount","type":"uint256"},{"indexed":false,"internalType":"address","name":"cTokenCollateral","type":"address"},{"indexed":false,"internalType":"uint256","name":"seizeTokens","type":"uint256"}],"name":"LiquidateBorrow","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"minter","type":"address"},{"indexed":false,"internalType":"uint256","name":"mintAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"mintTokens","type":"uint256"}],"name":"Mint","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"oldAdmin","type":"address"},{"indexed":false,"internalType":"address","name":"newAdmin","type":"address"}],"name":"NewAdmin","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"contractComptrollerInterface","name":"oldComptroller","type":"address"},{"indexed":false,"internalType":"contractComptrollerInterface","name":"newComptroller","type":"address"}],"name":"NewComptroller","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"oldImplementation","type":"address"},{"indexed":false,"internalType":"address","name":"newImplementation","type":"address"}],"name":"NewImplementation","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"contractInterestRateModel","name":"oldInterestRateModel","type":"address"},{"indexed":false,"internalType":"contractInterestRateModel","name":"newInterestRateModel","type":"address"}],"name":"NewMarketInterestRateModel","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"oldPendingAdmin","type":"address"},{"indexed":false,"internalType":"address","name":"newPendingAdmin","type":"address"}],"name":"NewPendingAdmin","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"oldReserveFactorMantissa","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"newReserveFactorMantissa","type":"uint256"}],"name":"NewReserveFactor","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"redeemer","type":"address"},{"indexed":false,"internalType":"uint256","name":"redeemAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"redeemTokens","type":"uint256"}],"name":"Redeem","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"payer","type":"address"},{"indexed":false,"internalType":"address","name":"borrower","type":"address"},{"indexed":false,"internalType":"uint256","name":"repayAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"accountBorrows","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"totalBorrows","type":"uint256"}],"name":"RepayBorrow","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"benefactor","type":"address"},{"indexed":false,"internalType":"uint256","name":"addAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"newTotalReserves","type":"uint256"}],"name":"ReservesAdded","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"admin","type":"address"},{"indexed":false,"internalType":"uint256","name":"reduceAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"newTotalReserves","type":"uint256"}],"name":"ReservesReduced","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Transfer","type":"event"},{"payable":true,"stateMutability":"payable","type":"fallback"},{"constant":false,"inputs":[],"name":"_acceptAdmin","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"addAmount","type":"uint256"}],"name":"_addReserves","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"reduceAmount","type":"uint256"}],"name":"_reduceReserves","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"contractComptrollerInterface","name":"newComptroller","type":"address"}],"name":"_setComptroller","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"implementation_","type":"address"},{"internalType":"bool","name":"allowResign","type":"bool"},{"internalType":"bytes","name":"becomeImplementationData","type":"bytes"}],"name":"_setImplementation","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"contractInterestRateModel","name":"newInterestRateModel","type":"address"}],"name":"_setInterestRateModel","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"addresspayable","name":"newPendingAdmin","type":"address"}],"name":"_setPendingAdmin","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"newReserveFactorMantissa","type":"uint256"}],"name":"_setReserveFactor","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"accrualBlockNumber","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"accrueInterest","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"admin","outputs":[{"internalType":"addresspayable","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"spender","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"owner","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"owner","type":"address"}],"name":"balanceOfUnderlying","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"borrowAmount","type":"uint256"}],"name":"borrow","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"borrowBalanceCurrent","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"borrowBalanceStored","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"borrowIndex","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"borrowRatePerBlock","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"comptroller","outputs":[{"internalType":"contractComptrollerInterface","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"bytes","name":"data","type":"bytes"}],"name":"delegateToImplementation","outputs":[{"internalType":"bytes","name":"","type":"bytes"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"internalType":"bytes","name":"data","type":"bytes"}],"name":"delegateToViewImplementation","outputs":[{"internalType":"bytes","name":"","type":"bytes"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"exchangeRateCurrent","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"exchangeRateStored","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"getAccountSnapshot","outputs":[{"internalType":"uint256","name":"","type":"uint256"},{"internalType":"uint256","name":"","type":"uint256"},{"internalType":"uint256","name":"","type":"uint256"},{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"getCash","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"implementation","outputs":[{"internalType":"address","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"interestRateModel","outputs":[{"internalType":"contractInterestRateModel","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"isCToken","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"borrower","type":"address"},{"internalType":"uint256","name":"repayAmount","type":"uint256"},{"internalType":"contractCTokenInterface","name":"cTokenCollateral","type":"address"}],"name":"liquidateBorrow","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"mintAmount","type":"uint256"}],"name":"mint","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"pendingAdmin","outputs":[{"internalType":"addresspayable","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"redeemTokens","type":"uint256"}],"name":"redeem","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"redeemAmount","type":"uint256"}],"name":"redeemUnderlying","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"repayAmount","type":"uint256"}],"name":"repayBorrow","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"borrower","type":"address"},{"internalType":"uint256","name":"repayAmount","type":"uint256"}],"name":"repayBorrowBehalf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"reserveFactorMantissa","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"liquidator","type":"address"},{"internalType":"address","name":"borrower","type":"address"},{"internalType":"uint256","name":"seizeTokens","type":"uint256"}],"name":"seize","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"supplyRatePerBlock","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"totalBorrows","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"totalBorrowsCurrent","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"totalReserves","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"src","type":"address"},{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"underlying","outputs":[{"internalType":"address","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"}]`)

[zemse]

Oh, I didn’t notice that.

{
  "constant": false,
  "inputs": [
    {
      "internalType": "address",
      "name": "owner",
      "type": "address"
    }
  ],
  "name": "balanceOfUnderlying",
  "outputs": [
    {
      "internalType": "uint256",
      "name": "",
      "type": "uint256"
    }
  ],
  "payable": false,
  "stateMutability": "nonpayable",
  "type": "function"
}

You can see the "constant": false, in the generated ABI, which causes the sendTransaction behavior. Can you do a recheck if that method is actually marked as view or pure in your smart contract?

[csmartinsfct]

This is actually a smart contract from compound.finance and you’re right, it isn’t marked as view or pure.

Smart contract

Closing the issue. Thank you @zemse. Keep up the great work @ricmoo - very thankful, great library 😃