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ContractFunction.call may fail as args and kwargs properties may be None #2541

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iwiwi opened this issue Jun 27, 2022 · 2 comments · May be fixed by #2545
Open

ContractFunction.call may fail as args and kwargs properties may be None #2541

iwiwi opened this issue Jun 27, 2022 · 2 comments · May be fixed by #2545
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@kclowes
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priority: p3 normal

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@iwiwi
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iwiwi commented Jun 27, 2022

  • Version: 5.29.2
  • Python: 3.10.4
  • OS: linux

What was wrong?

Depending on the way how a ContractFunction is instantiated, its args and kwargs may be None, which occurs errors when invoking call.

Example code

import json
from web3.auto.infura import w3

USDC = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
EIP20_ABI = json.loads('[{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"}],"name":"approve","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_from","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transferFrom","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transfer","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"anonymous":false,"inputs":[{"indexed":true,"name":"_from","type":"address"},{"indexed":true,"name":"_to","type":"address"},{"indexed":false,"name":"_value","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"_owner","type":"address"},{"indexed":true,"name":"_spender","type":"address"},{"indexed":false,"name":"_value","type":"uint256"}],"name":"Approval","type":"event"}]')

contract = w3.eth.contract(USDC, abi=EIP20_ABI)
f = contract.get_function_by_signature("decimals()")
f.call()

Result

Traceback (most recent call last):
  File "...", line 14, in <module>
    f.call()
  File ".../venv/lib/python3.10/site-packages/web3/contract.py", line 957, in call
    return call_contract_function(
TypeError: Value after * must be an iterable, not NoneType

How can it be fixed?

The minimal fix may be changing *self.args and **self.kwargs to *(self.args or []) and **(self.kwargs or {}) in the following lines:

web3.py/web3/contract.py

Lines 1222 to 1223 in c68f656

*self.args,
**self.kwargs,

I can work on creating a PR.
@kclowes
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kclowes commented Jun 27, 2022

Sure, a PR would be great. Thanks!

@iwiwi iwiwi linked a pull request Jun 28, 2022 that will close this issue
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@iwiwi
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iwiwi commented Jun 28, 2022

Thanks for your response! Created a PR: #2545

@kclowes kclowes self-assigned this Apr 15, 2024
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Fix TypeError in ContractFunction.call when args and kwargs properties are None iwiwi/web3.py
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@iwiwi @kclowes