The new SetCode transaction type introduces some additional complexity
when handling the transaction pool.
This complexity stems from two new account behaviors:
1. The balance and nonce of an account can change during regular
transaction execution *when they have a deployed delegation*.
2. The nonce and code of an account can change without any EVM execution
at all. This is the "set code" mechanism introduced by EIP-7702.
The first issue has already been considered extensively during the design
of ERC-4337, and we're relatively confident in the solution of simply
limiting the number of in-flight pending transactions an account can have
to one. This puts a reasonable bound on transaction cancellation. Normally
to cancel, you would need to spend 21,000 gas. Now it's possible to cancel
for around the cost of warming the account and sending value
(`2,600+9,000=11,600`). So 50% cheaper.
The second issue is more novel and needs further consideration.
Since authorizations are not bound to a specific transaction, we
cannot drop transactions with conflicting authorizations. Otherwise,
it might be possible to cherry-pick authorizations from txs and front
run them with different txs at much lower fee amounts, effectively DoSing
the authority. Fortunately, conflicting authorizations do not affect the
underlying validity of the transaction so we can just accept both.
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Co-authored-by: Marius van der Wijden <m.vanderwijden@live.de>
Co-authored-by: Felix Lange <fjl@twurst.com>
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