[Feature] Add serde rountrip tests for executionpayload

[mattsse]

Component

rpc

Describe the feature you would like

for these we need some sanity serde rountrip tests:

alloy/crates/rpc-types-engine/src/payload.rs

Lines 827 to 832 in 0fbc37d

	/// An execution payload, which can be either [ExecutionPayloadV1], [ExecutionPayloadV2], or
	/// [ExecutionPayloadV3].
	#[derive(Clone, Debug, PartialEq, Eq)]
	#[cfg_attr(feature = "serde", derive(serde::Serialize))]
	#[cfg_attr(feature = "serde", serde(untagged))]
	pub enum ExecutionPayload {

because I believe V3 deserde doesn't behave as expected and we likely need manual deserde impl

see also: alloy-rs/op-alloy#416 (comment)

Additional context

No response

[siosw]

right now if we have a ExecutionPayloadV3 json, we can still do:
let payload: ExecutionPayloadV2 = serde_json::from_str(json).unwrap();

and extra fields just implicitly get ignored. but obv you can no longer roundtrip then.

is this the behavior you're referring to?

[mattsse]

exactly

which means the untagged serde for deserialize is wrong

I guess we could solve this with deny_unknown_fields but could be problematic as well

[siosw]

afaik we can't use deny_unknown_field because we rely on flatten already and the two are incompatible

i'd like to work on this. do you think it makes sense to start with a test that asserts this faulty behavior and then work on a custom deserde impl in a follow up PR?

[mattsse]

do you think it makes sense to start with a test that asserts this faulty behavior and then work on a custom deserde impl in a follow up PR?

yep

great, assigned