fCU call to unknown hash ignored

[advaita-saha]

nimbus-eth1/execution_chain/beacon/api_handler/api_forkchoice.nim

Lines 110 to 117 in 24f0760

	# If the head hash is unknown (was not given to us in a newPayload request),
	# we cannot resolve the header, so not much to do. This could be extended in
	# the future to resolve from the `eth` network, but it's an unexpected case
	# that should be fixed, not papered over.
	let header = chain.quarantine.getHeader(headHash).valueOr:
	warn "Forkchoice requested unknown head",
	hash = headHash.short
	return simpleFCU(PayloadExecutionStatus.syncing)

In this code path, we can see that fCU call to blocks whose header is not with us, are ignored.

But the syncer already have interface which allows us to sync from just a blockHash

nimbus-eth1/execution_chain/nimbus_execution_client.nim

Lines 178 to 187 in 24f0760

	# Optional for pre-setting the sync target (e.g. for debugging)
	if config.beaconSyncTarget.isSome():
	syncerShouldRun = true
	let
	hex = config.beaconSyncTarget.unsafeGet
	isFinal = config.beaconSyncTargetIsFinal
	if not nimbus.beaconSyncRef.configTarget(hex, isFinal):
	fatal "Error parsing hash32 argument for --debug-beacon-sync-target",
	hash32=hex
	quit QuitFailure

What needs to be done is unify the interface, such that only need the hash, and let the syncer handle the rest. Use that same interface inside the forkChoice api call, instead of handling this case separately

[advaita-saha]

@mjfh Can you look into this?
It would be very helpful to get this done

[mjfh]

The beaconSyncTarget and beaconSyncTargetIsFinal are completely independent from any other hash logic. So I do not see what you want to unify here.