def _call_contract(
self,
web3: Optional[Web3],
contract_address: ChecksumEthAddress,
abi: List,
method_name: str,
arguments: Optional[List[Any]] = None,
) -> Any:
"""Performs an eth_call to an ethereum contract
May raise:
- RemoteError if etherscan is used and there is a problem with
reaching it or with the returned result
- BlockchainQueryError if web3 is used and there is a VM execution error
"""
if web3 is None:
return self._call_contract_etherscan(
contract_address=contract_address,
abi=abi,
method_name=method_name,
arguments=arguments,
)
contract = web3.eth.contract(address=contract_address, abi=abi)
try:
method = getattr(contract.caller, method_name)
result = method(*arguments if arguments else [])
except (ValueError, BadFunctionCallOutput) as e:
raise BlockchainQueryError(
f'Error doing call on contract {contract_address}: {str(e)}',
) from e
return result
def _call_contract_etherscan(
self,
contract_address: ChecksumEthAddress,
abi: List,
method_name: str,
arguments: Optional[List[Any]] = None,
) -> Any:
"""Performs an eth_call to an ethereum contract via etherscan
May raise:
- RemoteError if there is a problem with
reaching etherscan or with the returned result
"""
web3 = Web3()
contract = web3.eth.contract(address=contract_address, abi=abi)
input_data = contract.encodeABI(method_name,
args=arguments if arguments else [])
result = self.etherscan.eth_call(
to_address=contract_address,
input_data=input_data,
)
if result == '0x':
raise BlockchainQueryError(
f'Error doing call on contract {contract_address} for {method_name} '
f'with arguments: {str(arguments)} via etherscan. Returned 0x result',
)
fn_abi = contract._find_matching_fn_abi(
fn_identifier=method_name,
args=arguments,
)
output_types = get_abi_output_types(fn_abi)
output_data = web3.codec.decode_abi(output_types,
bytes.fromhex(result[2:]))
if len(output_data) == 1:
# due to https://github.com/PyCQA/pylint/issues/4114
return output_data[0] # pylint: disable=unsubscriptable-object
return output_data