Allow impersonating contracts

[antazoey]

Component

Anvil

Describe the feature you would like

For feature-parity sake with Hardhat, I would like to be able to impersonate contracts. This helps migrate tests from hardhat to foundry.

Currently when I try to do this, there is an issue with code.
However - even when I set the code to be empty, I have issues with estimating fees.

Additional context

No response

[mattsse]

what version are you on? there was a fix for this this weekend #1912

[antazoey]

what version are you on? there was a fix for this this weekend #1912

I built Anvil from master branch.
when I try to estimate the gas, I get the error: gas exceeds allowance: 0
and when I specify gas, I get an error 'Insufficient funds for gas * price + value'

[mattsse]

I see
You can of course set the balance of the account manually via anvil_setBalance (I believe) (same as hardhat)

[antazoey]

Yes, that did it!
so one thing I noticed is that in Hardhat my reverts would fail first before the balance checking stuff whereas in Anvil, this failed first, which is how I found this issue or go into this situation (during migration)

It totally is not a big deal though! And now I am writing better tests because of it :)

[ThomasdenH]

How does impersonating contracts work? I tried doing the following:

  const provider = new ethers.providers.JsonRpcProvider();
  const timeLock = "0x3b870db67a45611CF4723d44487EAF398fAc51E3";
  await provider.send("anvil_impersonateAccount", [
    "0x3b870db67a45611CF4723d44487EAF398fAc51E3",
  ]);
  const signer = provider.getSigner(timeLock);
  const fyToken = new Contract(
    "0x53358d088d835399F1E97D2a01d79fC925c7D999",
    fyTokenAbi,
    signer
  );
  const tx1 = await fyToken.setFlashFeeFactor(1);

However, this gives the error

{
  "jsonrpc": "2.0",
  "id": 47,
  "error": {
    "code": -32603,
    "message": "EVM error RejectCallerWithCode"
  }
}

error={"code":-32603},
requestBody="{\"method\":\"eth_estimateGas\",\"params\":[{\"from\":\"0x3b870db67a45611cf4723d44487eaf398fac51e3\",\"to\":\"0x53358d088d835399f1e97d2a01d79fc925c7d999\",\"data\":\"0x159c03dd0000000000000000000000000000000000000000000000000000000000000001\"}],\"id\":47,\"jsonrpc\":\"2.0\"

Edit: The following sequence of requests did the job:

await provider.send("anvil_impersonateAccount", [timeLock]);
await provider.send("anvil_setCode", [timeLock, ""]);
await provider.send("anvil_setBalance", [timeLock, "1000000000000000000"]);

[mattsse]

Oh right, the evm implementation doesn't allow calls from contracts, https://eips.ethereum.org/EIPS/eip-3607
need to check if there's a workaround for that, but will document this

[naddison36]

I also hit this error. Thanks @ThomasdenH for the workaround of setting the code of the impersonated contract to an empty string.

For anyone else looking for this workaround, here's how I did it using Hardhat API calls

// impersonates a specific account
export const impersonate = async (addr: string, fund = true): Promise<Signer> => {
    // Dynamic import hardhat module to avoid importing while hardhat config is being defined.
    // The error this avoids is:
    // Error HH9: Error while loading Hardhat's configuration.
    const { network, ethers } = await import("hardhat")
    await network.provider.request({
        method: "hardhat_impersonateAccount",
        params: [addr],
    })
    // this is needed for Anvil which does not allow a contract to be impersonated.
    // The following sets the contract's code to a zero number of bytes so the contract can be impersonated.
    // https://github.com/foundry-rs/foundry/issues/1943
    await network.provider.request({
        method: "hardhat_setCode",
        params: [addr, "0x"],
    })
    if (fund) {
        // Give the account 10 Ether
        await network.provider.request({
            method: "hardhat_setBalance",
            params: [addr, "0x8AC7230489E80000"],
        })
    }
    return ethers.provider.getSigner(addr)
}

[mattsse]

#2090 should remove the code temporarily

do you run into issues where this doesn't work properly? @naddison36