how to get events with staticcall

[novaknole]

Hi @zemse @ricmoo

I have a contract that emits the events.. Not returns it, but emits.

I want to simulate the function ! If I use ethers's staticcall feature, problem is, I can't get events.

Isn't there any way in ethers to do this ?

[zemse]

Currently, with standard ethereum APIs, there's really no straight way to do that.

You can use debug_traceCall module of geth/erigon to get execution info and you can extract logs from it. For this you need an eth node that has tracing enabled (usually its not or being a paywall because it's a computationally expensive API).

Otherwise, a hacky way would be to use hardhat network or anvil to start a mainnet fork at current block and make a transaction on the block and get its events from the receipt. This is a slower option since the mainnet fork needs to query all the state involved but might be just worth it if you cannot manage an archive/trace node.

MEV searchers usually modify geth's eth_call implementation (which is used by ethers.js's callStatic feature) to record the emitted logs or any info they find useful, so queries are faster than debug_traceCall.

[fridary]

Currently, with standard ethereum APIs, there's really no straight way to do that.

You can use debug_traceCall module of geth/erigon to get execution info and you can extract logs from it. For this you need an eth node that has tracing enabled (usually its not or being a paywall because it's a computationally expensive API).

@zemse Can you do some help how to decode log data? This what I've done:

hash_ = '0xe0a465d1e4a622ca43db886b589122c6f44390b6a1a1715aab0948ac246619c9'
tx = requests.post(testnet, json={"method":"eth_getTransactionByHash","params":[hash_],"id":1,"jsonrpc":"2.0"}, headers={"Content-Type": "application/json"}).json()['result'] 
call = requests.post(testnet, json={
    'id': 1,
    'method': 'debug_traceCall',
    'jsonrpc': '2.0',
    'params': [
        {'to': tx['to'], 'gas': tx['gas'], 'gasPrice': tx['gasPrice'], 'value': tx['value'], 'data': tx['input'], 'from': tx['from']},
        19892443,
        #{'tracer': 'callTracer'}
        {'tracer': 'prestateTracer'}
    ]
}, headers={"Content-Type": "application/json"}).json()['result'] 

As result it gives a lot of byte code (both for callTracer and prestateTracer) that I don't know how to decode like:

{'jsonrpc': '2.0', 'id': 1, 'result': {'0x0000000000000000000000000000000000000000': {'balance': '0x2d47a082af8dc970268'}, '0x14fee680690900ba0cccfc76ad70fd1b95d10e16': {'balance': '0x0', 'code': '0x6080604052600436106103385760003560e01c8063590ffdce116101b0578063ab558e4d116100ec578063dd62ed3e11610095578063f94aa1b41161006f578063f94aa1b4146109ac578063fb78680d14610a12578063fdb78c0e14610a32578063feadde9c1....

[zemse]

Does callTracer and prestateTracer outputs have any log field? (I don't think they have). I wish someone adds a log tracer to this.