Decoding Tx data

[iboxgithub]

Hi,

I read the issues:
#366
#422
#423
but unfortunately I still don't manage to decode data from a Tx...

In my example, it's a Uniswap Tx:

https://etherscan.io/tx/0xa7ff37fad351241d37d59eb43268e55d6e6203e51f7747a7fcaf8f760528acb4

I tried:

let iface = new ethers.utils.Interface(abi_uniswapv2);
let y = iface.parseTransaction(tx);
console.log(y);

I also tried to just parse tx.data which doesn't work neither. Does anyone have any idea on how to fix this?
thanks for your help!

[yuetloo]

Not sure what your abi_uniswapv2 is, but, I was able to parse transaction for a different tx hash with known abi as follow:

const ethers = require('ethers');
const provider = new ethers.providers.InfuraProvider();

// abi from  https://unpkg.com/@uniswap/v2-core@1.0.0/build/IUniswapV2Pair.json
const abi = [ "function approve(address spender, uint value) external returns (bool)" ];

const iface = new ethers.utils.Interface( abi );
const hash = '0xecb316dbeac9f6d8c5802a4d927ab51a4decf3b280305b2dd9756f96fa1a24b2';
provider.getTransaction(hash).then( async (tx) => {
   const  txDesc = await iface.parseTransaction(tx);
   console.log('desc', txDesc);
});

[iboxgithub]

Hi @yuetloo , thanks for your answer. For Tx like the one you used, indeed the ABI is known, my issue is when I don't know exactly which function will be used before. In my example, I would like to see the 3 swaps ETH -> UBI, UBI -> DAI, DAI -> ETH with their parameters like minAmountOut, deadline etc... (they appear on Etherscan but as events, so post mining, whereas I should be able to see the params within the Data field)
the ABI used is from Uni router: https://etherscan.io/address/0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D#code
Services like Blocknative live decode Data in their Mempool Explorer, I am just trying to find how they do :)
thanks for your help

[yuetloo]

What error did you get? When I ran my script against your abi and tx hash, I got the following error. This means the abi doesn't contain the function (0xa454dfa9) called in the transaction.

  reason: 'no matching function',
  code: 'INVALID_ARGUMENT',
  argument: 'sighash',
  value: '0xa454dfa9'

[iboxgithub]

I have the exact same error, whereas this is a Swap on Uniswap (as we can see on Etherscan) so I don't understand why they ABI would not match. I am missing something but I don't know what... Using the lib 'ethereum-input-data-decoder' I get some parameters (not the good ones but at least 2 addresses), so I don't know what I am missing with ethers, I would like to avoid having to use another lib

[shelldor73]

Hello ! i am stuck on the same problem as you. So just want to know if you were able to find any solution to parse those transactions that come from custom contracts like the one you specified ?

[iboxgithub]

hi, no in the end when it comes from a custom contract you can't do with Ethers (at least with method above), what front end bots do in this case is to totally decode a smart contract (sometimes manually, bytecode level) which is way above my knowledge