API for re-sending transactions

What was wrong?

There are a few legitimate use cases for wanting to re-submit a transaction that has already been sent with modified parameters.

• Resending the same transaction with a higher gas price during times of network congestion.
• Quickly overriding a transaction sent in error (also by using a higher gas price)
• In a case where you know there is a signed transaction that was sent but never included in a block, ensuring that it will not be applied at some point in the future.

How can it be fixed?

Implement a new API web3.eth.overrideTransaction(txn_hash, txn_overrides)

• txn_hash is the hash of the transaction you wish to override.
• txn_overrides is a dictionary of transaction parameters which should be used in place of the existing transaction parameters.

Behavior is as follows.

• if no transaction can be found with the given hash an exception is thrown.
• if the transaction has already been mined an exception is thrown.
• The txn_overrides may contain any/all fields that are normally accepted as transaction params except nonce.
• If gasPrice is included in the txn_overrides, it must be greater than the existing transaction gas price (TODO: should we allow a way to bypass this validation)
• if gasPrice is not included in the txn_overrides we should ??? (TODO: how do we choose an appropriate gas price?).

[monokh]

Put in a very beginning of work on this. Apologies that this is going slow. Not had much time and doing more learning than coding here 😄 Should be able to get something reviewable quality after the weekend.

[monokh]

Web3.py actually uses eth-tester now which includes options for disabling auto mining. Therefore there won’t be problems with the tests or development:

tester = EthereumTester(auto_mine_transactions=False)
web3 = Web3(EthereumTesterProvider(tester))
tx = web3.eth.sendTransaction({
    'from': '0x82A978B3f5962A5b0957d9ee9eEf472EE55B42F1',
    'to': '0x7d577a597B2742b498Cb5Cf0C26cDCD726d39E6e',
    'value': '1000'
})
print(web3.eth.getTransaction(tx.hex()))
>>> ...... 'nonce': 0, 'blockHash': None, 'blockNumber': None, ......