Getting array data with parseLogs in ethers.js

[Mudloop]

Ethers Version

5.6.5

Search Terms

No response

Describe the Problem

Hi,

I have an event that looks like this in Solidity :

event Entered(
    uint256[] indexed,
    uint256[] indexed
);

The problem is that when I crawl the logs using provider.getLogs() and then parse it with contract.interface.parseLog(), it returns the following args object :

"args": [
    {
        "_isIndexed": true,
        "hash": "0x4e5c294aaf165995a44b3b577370da9ad3e78ed52350bffb6f003b116b28b4be"
    },
    {
        "_isIndexed": true,
        "hash": "0x4e5c294aaf165995a44b3b577370da9ad3e78ed52350bffb6f003b116b28b4be"
    }
]

So the uint256[] array arguments only come through as hashes.

Is there a way to get ethersjs to retrieve the actual data in the uint256[] arrays from these events, or are these arguments only stored as hashes on the blockchain?

The fact that the args object comes through as an array (instead of giving me named arguments like it usually does) might indicate that ethersjs doesn't know how to deal with these properly, but there might still be a way to parse it. I haven't been able to find any info online on how to achieve this.

Thanks for the help!

Code Snippet

const logs = await app.provider.getLogs({
    address: c.address,
    fromBlock: await app.provider.getBlockNumber() - 10000,
    toBlock: await app.provider.getBlockNumber(),
});
for (let i = 0; i < logs.length; i++) {
	let parsed = c.interface.parseLog(logs[i]);
    console.log(parsed);
}

Contract ABI

{
  "anonymous": false,
  "inputs": [    
    {
      "indexed": true,
      "internalType": "uint256[]",
      "type": "uint256[]"
    },
    {
      "indexed": true,
      "internalType": "uint256[]",
      "type": "uint256[]"
    }
  ],
  "name": "Entered",
  "type": "event"
}

Errors

No response

Environment

Ethereum (mainnet/ropsten/rinkeby/goerli)

Environment (Other)

No response

[ricmoo]

Any parameter that is indexed, but it’s type cannot fit into 32 bytes, will be hashed and that is how it is stored on the blockchain.

If you need access to that data, you will need your event to include both the indexed and non-index version. For example, this is a common pattern (the string type doesn’t fit into 32 bytes, so this is the case even if the string is under 32 bytes long): event Foo(string indexed searchName, string name) and in solidity it would be called as emit Foo(name, name).

Logging topics cost an extra 375 gas and logging data costs extra gas for each byte; so the more data you log the more the tx will cost.

Does that make sense?

[Mudloop]

Yes, that makes a lot of sense. In hindsight I don't even need these indexed, since I'm crawling the events and indexing them in my own database - so I'll only need the fields once.
I was assuming it was like an indexed field in a database and it would both store the data and index it too, but I guess that's not how it works.
Thanks for your response!

[typedarray]

The fact that the args object comes through as an array (instead of giving me named arguments like it usually does)

I'm running into this aspect of the issue. It seems like if an event log includes any indexed argument that does not fit into 32 bytes, none of the event args will be available as named properties of the parsedLog.args object.

Is this the intended behavior? As a workaround, is it safe to do something like this?

const parsedLog = contract.interface.parseLog(log)

const args: Record<string, unknown> = {};

parsedLog.eventFragment.inputs.forEach((input, index) => {
  args[input.name] = parsedLog.args[index];
});

[ricmoo]

That should definitely not be the case.

Can you make sure your argument names are correctly specified in the ABI?

[typedarray]

I'm noticing this behavior for the FileCreated event on this contract. The argument names look correct. I'm using the ABI copied directly from Etherscan, and the ABI matches the verified source code. The log is coming from provider.send("eth_getLogs", ...).

Happy to attempt a reproducible example - do you have a template or suggestion of how to do that?

[ricmoo]

I usually just use https://playground.ethers.org for one-liners (or close to it). You should be able to just include the specific event ABI fragment and log to reproduce it…

[typedarray]

This input to https://playground.ethers.org appears to demonstrate the issue. (The event here corresponds to the one emitted by this tx)

new Contract("0x9746fD0A77829E12F8A9DBe70D7a322412325B91", [{
  "anonymous": false,
  "inputs": [
    {
      "indexed": true,
      "internalType": "string",
      "name": "indexedFilename",
      "type": "string"
    },
    {
      "indexed": true,
      "internalType": "bytes32",
      "name": "checksum",
      "type": "bytes32"
    },
    {
      "indexed": false,
      "internalType": "string",
      "name": "filename",
      "type": "string"
    },
    {
      "indexed": false,
      "internalType": "uint256",
      "name": "size",
      "type": "uint256"
    },
    {
      "indexed": false,
      "internalType": "bytes",
      "name": "metadata",
      "type": "bytes"
    }
  ],
  "name": "FileCreated",
  "type": "event"
}], provider).interface.parseLog({
  address: "0x9746fd0a77829e12f8a9dbe70d7a322412325b91",
  blockHash:
    "0xecb27efdd67a0ede946dfbfa4422f02df8ed24edef006d7cbdca2e3cc863ef80",
  blockNumber: "0xf3ded4",
  data: "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",
  logIndex: "0xce",
  removed: false,
  topics: [
    "0xbf4d3dad9eb190a395deec4f74f993087bfb5df21ff6c0e1403ec61042090c2d",
    "0x5910bcd49163a9732a5defa7ecccb5e77bc69f296d21d7c217ba37818c33d1a7",
    "0x83f94617674079bd3667d2c62dcc340346f17cd97a03977b67acc42c69322bbd",
  ],
  transactionHash:
    "0x24e50389c76ac159cb1f532d32aaec57dd2fbe5ed62a3012c2aeeab4c7560a19",
  transactionIndex: "0x77",
})