abi decode value returned as `[Getter]` and throws error when accessing it

[miguelmota]

Hi,

I'm trying to decode function data but geting an unexpected result. This ABI has two input types so the expected result is an array with two values. The result array is indeed length of 2, however the first item is returned as [Getter] function instead of returning the address value.

const ethers = require('ethers')
const fragment = { constant: false, inputs: [{ name: '_to', type: 'address' }, { name: '_value', type: 'uint256' }], name: 'transfer', outputs: [{ name: 'success', type: 'bool' }], payable: false, type: 'function' }

const ifc = new ethers.utils.Interface([])
const data = '0xa9059cbb85f1150654584d0192059454e9dc1532d9d9cf914926406a02370cea80cf32f600000000000000000000000000000000000000000000000000000000033dc10b'
const result = ifc.decodeFunctionData(ethers.utils.FunctionFragment.fromObject(fragment), data)
console.log(result)
console.log(result.length)
console.log(result[0])

[
  [Getter],
  BigNumber { _hex: '0x033dc10b', _isBigNumber: true },
  _value: BigNumber { _hex: '0x033dc10b', _isBigNumber: true }
]
2
/home/mota/Sandbox/test/node_modules/ethers/node_modules/@ethersproject/abi/lib/coders/array.js:163
                get: function () { throw value; }
                                   ^

_to: value out of range (argument="value", value=20, code=INVALID_ARGUMENT, version=bytes/5.0.11)
    at Logger.makeError (/home/mota/Sandbox/test/node_modules/@ethersproject/logger/lib/index.js:180:21)
    at Logger.throwError (/home/mota/Sandbox/test/node_modules/@ethersproject/logger/lib/index.js:189:20)
    at Logger.throwArgumentError (/home/mota/Sandbox/test/node_modules/@ethersproject/logger/lib/index.js:192:21)
    at Object.hexZeroPad (/home/mota/Sandbox/test/node_modules/@ethersproject/bytes/lib/index.js:264:16)
    at AddressCoder.decode (/home/mota/Sandbox/test/node_modules/ethers/node_modules/@ethersproject/abi/lib/coders/address.js:40:45)
    at /home/mota/Sandbox/test/node_modules/ethers/node_modules/@ethersproject/abi/lib/coders/array.js:109:31
    at Array.forEach (<anonymous>)
    at Object.unpack (/home/mota/Sandbox/test/node_modules/ethers/node_modules/@ethersproject/abi/lib/coders/array.js:88:12)
    at TupleCoder.decode (/home/mota/Sandbox/test/node_modules/ethers/node_modules/@ethersproject/abi/lib/coders/tuple.js:74:49)
    at AbiCoder.decode (/home/mota/Sandbox/test/node_modules/ethers/node_modules/@ethersproject/abi/lib/abi-coder.js:100:22) {
  reason: 'value out of range',
  code: 'INVALID_ARGUMENT',
  argument: 'value',
  value: 20,
  baseType: 'address',
  type: 'address'
}

Tx for reference: https://etherscan.io/tx/0x0fc8f1cb5112c4679dfcbde54306cabecedfbfd115030252b2e3d77ed7b7da8c

Etherscan is able to decode it correctly

[ricmoo]

A Result object uses a getter to defer access errors, for when the value is invalid for the type. Otherwise the decoding would fail immediately and error recovery would be impossible.

In your above example, you can see the data is an invalid address, as there are non-zero bytes in the top 12 bytes of what you are trying to interpret as an address. An ABI encoded address must have all its upper 96 bits zero.

The contract seems to have a bug in it? Was it written in assembly directly? Or perhaps the contract contains an asm block that is corrupting the return memory space?

[miguelmota]

Not sure about the implementation details of the contract since it's not something I wrote.
Is it possible to access the the data for the input parameter to be able to truncate it manually? For example, If I were to wrap it an try catch and if it throws then check the field type and if it's an address type then try to truncate it and checksum it. Is this possible?

[armagg]

do you have an update?
I faced with this error in decoding tron trx data for some of them ( about 30 percent)

[realarlong]

can you find any solution?

[ricmoo]

Yes, that it the entire point of that getter. It allows access to a value which would have otherwise fully crashed parsing. :)

If you look at the error, it contains the entire data used, which caused the problem, which can be used, for example, with toUtf8String, but with a folding error handler.

See #1894 for a code example which does exactly this. :)