Error: invalid utf8 byte sequence; invalid continuation byte

Hi,

I am getting the following error whilst trying to parse an event using ethers.js interface.

This event emits a string, I assume this has something to do with the problem because before I added the string to the event data emission there was no problem with parsing the log.

The event in solidity:

    event LogExecutionFailure(
        address indexed executor,
        uint256 indexed executionClaimId,
        address payable indexed user,
        IGelatoTrigger trigger,
        IGelatoAction action,
        string executionFailureReason
    );

My ethers script that throws the error:

const abi = [ "event LogExecutionFailure(address indexed executor, uint256 indexed executionClaimId, address indexed user, address trigger, address action, string executionFailureReason)"]

const iface = new ethers.utils.Interface(abi);

const topicExecutionFailure = ethers.utils.id(
      "LogExecutionFailure(address,uint256,address,address,address,string)"
);

const filterExecutionFailure = {
      address: "0x21F7908734A147e084DBEe58C616fd59CE2A0a02",
      fromBlock: parseInt(searchFromBlock),
      topics: [topicExecutionFailure]
};
const logsExecutionFailure = await provider.getLogs(
      filterExecutionFailure
);
for (const log of logsExecutionFailure) {
      const parsedLog = iface.parseLog(log);
....
ERROR throws here
}

Here is a link to the tx that emitted this event on 0x21F7908734A147e084DBEe58C616fd59CE2A0a02 on Kovan

As you can see the correct string (“ErrorTransferFromUser”) is shown as part of the event data on Kovan:

Please help me find out why my ethers interface throws when trying to parseLog(log).

[ricmoo]

(you might have to skip over 68 bytes instead of 36 to get past a string link too… Maybe try 68 before 36? I’m more confident in that number now that I think about it)

[gitpusha]

(you might have to skip over 68 bytes instead of 36 to get past a string link too… Maybe try 68 before 36? I’m more confident in that number now that I think about it)

Update: This seems to have worked well!

I was able to use the string now in ethers.js

This code does the trick now, as you prescribed.

Do you think this implementation is ok?

I left out this bit:

You would also probably want to add some safety by checking revertReason.length % 32 == 4 and check that the first 4 bytes are the Error(string) selector.

because I catch any evm exceptions during the decoding anyway.

Can you elaborate on this bit revertReason.length % 32 == 4, please? I dont quite get this sanity check. Why == 4?

Thanks again for your great help.