How to use estimateGas on an empty account?

[TimDaub]

• I have a very specific problem. I want to call the OptimismPortal's depositTransaction endpoint
• https://etherscan.io/address/0x5fb30336a8d0841cf15d452afa297cb6d10877d7#writeContract
• It executes a call on Optimism, but the transaction is sent to mainnet and deposits funds into Optimism directly.
• I have successfully used this to buy my NFT on Optimism through an L1 transaction; here are the transactions
  • https://optimistic.etherscan.io/tx/0x80cb2bce6e59668856331af7ce6682f7613e949b231659f8f92624afa7e6aaea
  • https://etherscan.io/tx/0x0eccb3a74248f438f393dd70471e2207840d04bfaf743930d2ddaf90adfa76a1
• However, for this I used a manual way of estimating the gasLimit I should pass in. Yet, now when I actually try to implement this for users in my frontend, my case is that I will have to estimate their gas costs on Optimism, but I will only have to do that when they DON'T have funds on Optimism.
• Here's a snippet of my code to estimate the gas costs, and this actually doesn't error when the from address is actually the connected address in the frontend (and it has Optimism funds)

//...
  const opProvider = getProvider({ chainId: optimism.id });
  const contract = new Contract(addressDelegator, abiDelegator, opProvider);
  const txRequest = {
    from: zeroAddress, // 0x000...
    to: addressDelegator,
    data: contract.interface.encodeFunctionData("setup", [
      quantity,
      payload,
      comment,
      referral,
    ]),
    value: price,
    chainId: optimism.id,
  };
  const gasLimit = await opProvider.estimateGas(txRequest);
  console.log(gasLimit);

//...

• However, when the from address doesn't have funds on Optimism, the issue is that the frontend will throw an insufficient funds error. So (as can also be seen in the above snippet), I tried to work around that using the zero-address which has around 2k USD on Optimism. Yet, even for that address ethers throws (I don't know why). Here's that error

Uncaught (in promise) Error: cannot estimate gas; transaction may fail or may require manual gas limit [ See: https://links.ethers.org/v5-errors-UNPREDICTABLE_GAS_LIMIT ] (reason="execution reverted", method="estimateGas", transaction={"from":"0x0000000000000000000000000000000000000000","to":"0xEA3B341b1f189f8e56b00c8E387B770acAE121CF","value":{"type":"BigNumber","hex":"0x0bdafbdb9d9000"},"data":"0x00cc0d100000000000000000000000000000000000000000000000000000000000000001dc1d74609a14faeee0b6afc6e1aa672f75832ea02f8e056c8420136302852dd35373c1fabb7532980418e839525c0ac8f90d52539938ac0464eed619494747392e53e38734d91644927b4f7cf9049f2b42a9340d00000000000000000000000100000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","accessList":null}, error={"reason":"processing response error","code":"SERVER_ERROR","body":"{\"jsonrpc\":\"2.0\",\"id\":47,\"error\":{\"code\":3,\"message\":\"execution reverted\",\"data\":\"0x2e076300\"}}","error":{"code":3,"data":"0x2e076300"},"requestBody":"{\"method\":\"eth_estimateGas\",\"params\":[{\"value\":\"0xbdafbdb9d9000\",\"from\":\"0x0000000000000000000000000000000000000000\",\"to\":\"0xea3b341b1f189f8e56b00c8e387b770acae121cf\",\"data\":\"0x00cc0d100000000000000000000000000000000000000000000000000000000000000001dc1d74609a14faeee0b6afc6e1aa672f75832ea02f8e056c8420136302852dd35373c1fabb7532980418e839525c0ac8f90d52539938ac0464eed619494747392e53e38734d91644927b4f7cf9049f2b42a9340d00000000000000000000000100000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000\"}],\"id\":47,\"jsonrpc\":\"2.0\"}","requestMethod":"POST","url":"https://opt-mainnet.g.alchemy.com/v2/3ZBBnBhNn0nMmNcdgXFpqWqC981hd1Z2"}, code=UNPREDICTABLE_GAS_LIMIT, version=providers/5.7.2)
    at Logger.makeError (index.ts:269:28)
    at Logger.throwError (index.ts:281:20)
    at checkError (json-rpc-provider.ts:78:20)
    at AlchemyProvider.<anonymous> (json-rpc-provider.ts:642:20)
    at Generator.throw (<anonymous>)
    at rejected (json-rpc-provider.ts:20:1)

So what to do here? I'd prefer to not hard code the gas value but I feel like this is the only option that is left here.

[ricmoo]

Do you have the valid errors in your ABI that the contract can throw? I see it is using the error selector 0x2e076300 but it isn’t present in 4byte.

It looks like the actual contract is explicitly reverting though. Is it possible to compute the actual worst case gas limit and use that?

[TimDaub]

Hey @ricmoo, thanks for the quick response.

This is how I define my ABIs

const abiOptimismPortal = [
  {
    inputs: [
      { internalType: "address", name: "_to", type: "address" },
      { internalType: "uint256", name: "_value", type: "uint256" },
      { internalType: "uint64", name: "_gasLimit", type: "uint64" },
      { internalType: "bool", name: "_isCreation", type: "bool" },
      { internalType: "bytes", name: "_data", type: "bytes" },
    ],
    name: "depositTransaction",
    outputs: [],
    stateMutability: "payable",
    type: "function",
  },
];
const abiDelegator = [
  {
    inputs: [
      {
        internalType: "uint256",
        name: "quantity",
        type: "uint256",
      },
      {
        internalType: "bytes32[3]",
        name: "data",
        type: "bytes32[3]",
      },
      {
        internalType: "string",
        name: "comment",
        type: "string",
      },
      { internalType: "address", name: "referral", type: "address" },
    ],
    name: "setup",
    outputs: [],
    stateMutability: "payable",
    type: "function",
  },
];

But basically what you're saying is that the contract is actually throwing. Actually what can be is that the contract called on Optimism is reverting because it will attempt to mint an NFT and many NFT contracts have mints to address zero blocked. But anyways, I feel like using estimateGas is a fool's errand here because it can never truly well be estimated in the name of another transaction, right? As it would precisely lead to such errors occasionally. So maybe just getting a good upper bound gasLimit is the way to go here?

Anyways, I tried finding where the error code originated but I spent already a lot of time in trying to estimate gas, so if you also say that setting an upper gasLimit, I'll go with that.

[JohnOConnel]

@ricmoo Is it then not possible to estimate gas when there are no funds in the wallet? Services like meta-mask are still able to calculate gas when using an empty wallet. Is this then based on a fallback value? If so, what would be a good number for ETH fallback gas limit? Thanks