Prevents EthereumBlobExporter from consuming dest when returning NotApplicable

[claravanstaden]

Description

The EthereumBlobExporter consumes the dest parameter when the destination is not Here. Subsequent exporters will receive a None value for the destination instead of the original destination value, which is incorrect.

Closes #5788

Integration

Minor fix related to the exporter behaviour.

Review Notes

Verified that tests exporter_validate_with_invalid_dest_does_not_alter_destination and exporter_validate_with_invalid_universal_source_does_not_alter_universal_source fail without the fix in the exporter.

[bkontur]

@claravanstaden
bellow there is a another usage:

if Ok(local_net) != universal_location.global_consensus() {
			log::trace!(target: "xcm::ethereum_blob_exporter", "skipped due to unmatched relay network {local_net:?}.");
			return Err(SendError::NotApplicable)
		}

[claravanstaden]

I wondered about that one, because the comment only mentions dest and msg. But basically no mutable parameters should be altered when the error is NotApplicable?

[claravanstaden]

Fixed in bfc90ba. This case is easy to miss... Perhaps the parameters should not be mutable in the first place?

[claravanstaden]

I replaced it with a clone, as @yrong suggested. :) 4fe4085

[yrong]

How about just replace take here with clone without other reset operations?

[claravanstaden]

Good point, that is much better. :) 4fe4085

[yrong]

Same as #5789 (comment)

[claravanstaden]

4fe4085

[yrong]

+1

[bkontur]

I would maybe also change this:

log::error!(target: "xcm::ethereum_blob_exporter", "could not get global consensus from universal source '{universal_source:?}'.");
				SendError::Unroutable

to:

log::error!(target: "xcm::ethereum_blob_exporter", "could not get global consensus from universal source '{universal_source:?}'.");
				SendError::NotApplicable

to give a chance other routers in the tuple.

[bkontur]

and other suggestion change MissingArgument->NotApplicable:

		let para_id = match local_sub.as_slice() {
			[Parachain(para_id)] => *para_id,
			_ => {
				log::error!(target: "xcm::ethereum_blob_exporter", "could not get parachain id from universal source '{local_sub:?}'.");
                                // TODO: why not `NotApplicable`?
				return Err(SendError::MissingArgument)
			},
		};

	/// A needed argument is `None` when it should be `Some`.
	MissingArgument,

[bkontur]

and one more, I would move message.take() as a last step after all the validations pass.
And also Unroutable could be NotApplicable to give other router a chance.

		let message = message.take().ok_or_else(|| {
			log::error!(target: "xcm::ethereum_blob_exporter", "xcm message not provided.");
			SendError::MissingArgument
		})?;
		let source_location = Location::new(1, local_sub.clone());
		let agent_id = match AgentHashedDescription::convert_location(&source_location) {
			Some(id) => id,
			None => {
				log::error!(target: "xcm::ethereum_blob_exporter", "unroutable due to not being able to create agent id. '{source_location:?}'");
				return Err(SendError::Unroutable)
			},
		};

[acatangiu]

needs a prdoc

[claravanstaden]

@alistair-singh please double check this looks okay. 🙏🏻

[alistair-singh]

+1