XCMv5: Fix for compatibility with V4

[yrong]

Description

Our smoke tests transfer WETH from Sepolia to Westend-AssetHub breaks, try to reregister WETH on AH but fails as following:

https://bridgehub-westend.subscan.io/xcm_message/westend-4796d6b3600aca32ef63b9953acf6a456cfd2fbe

https://assethub-westend.subscan.io/extrinsic/9731267-0?event=9731267-2

The reason is that the transact call encoded on BH to register the asset

polkadot-sdk/bridges/snowbridge/primitives/router/src/inbound/mod.rs

Lines 282 to 289 in a77940b

	call: (
	create_call_index,
	asset_id,
	MultiAddress::<[u8; 32], ()>::Id(owner),
	MINIMUM_DEPOSIT,
	)
	.encode()
	.into(),

0x3500020209079edaa8020300fff9976782d46cc05630d1f6ebab18b2324d6b1400ce796ae65569a670d0c1cc1ac12515a3ce21b5fbf729d63d7b289baad070139d01000000000000000000000000000000

the asset_id which is the xcm location can't be decoded on AH in V5

Issue initial post in https://matrix.to/#/!qUtSTcfMJzBdPmpFKa:parity.io/$RNMAxIIOKGtBAqkgwiFuQf4eNaYpmOK-Pfw4d6vv1aU?via=parity.io&via=matrix.org&via=web3.foundation

[vgeddes]

Can you be more specific about what the problem is? The element link does not seem to be working for me.

XCMv4 and XCMv5 each have their own NetworkId with different encoding layouts, and they need to be explicitly converted to each other using From or TryFrom traits.

So then surely BH needs to take care to send an XCM to AH that is in the correct format?

[acatangiu]

The PR makes sense if we have v4::NetworkId entries in storage that we want to directly interpret as v5::NetworkId entries without migrating them.

Is this the case?

[yrong]

The PR makes sense if we have v4::NetworkId entries in storage that we want to directly interpret as v5::NetworkId entries without migrating them.

Is this the case?

Actually we don't store the call on BH, just send the encoded call to AH directly.

[alistair-singh]

+1

[acatangiu]

cc @franciscoaguirre

[yrong]

@acatangiu For AssetIdParameter could we use the VersionedLocation

polkadot-sdk/cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

Lines 417 to 418 in a77940b

	type AssetId = xcm::v5::Location;
	type AssetIdParameter = xcm::v5::Location;

instead?

[yrong]

@franciscoaguirre Could you help to approve this PR or anything unclear that I can provide, please let me know.

[franciscoaguirre]

Seems reasonable to keep the same indices

[acatangiu]

@acatangiu For AssetIdParameter could we use the VersionedLocation

polkadot-sdk/cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

Lines 417 to 418 in a77940b

	type AssetId = xcm::v5::Location;
	type AssetIdParameter = xcm::v5::Location;

instead?

AFAIK this has been discussed before and decided against because the storage still needs an upgrade every time to avoid situations of incorrect duplicate assetids registered: e.g. same ID but once with v3 and once with v4 - in the end it doesn't seem to help and makes code more complicated...