Fix migrations for pallet-xcm (paritytech#6148)

Relates to: paritytech#4826
Relates to: paritytech#3214

## Description

`pallet-xcm` stores some operational data that uses `Versioned*` XCM
types. When we add a new XCM version (XV), we deprecate XV-2 and remove
XV-3. Without proper migration, this can lead to issues with
[undecodable
storage](https://github.com/paritytech/polkadot-sdk/actions/runs/11381324568/job/31662577532?pr=6092),
as was identified on the XCMv5 branch where XCMv2 was removed.

This PR extends the existing `MigrateToLatestXcmVersion` to include
migration for the `Queries`, `LockedFungibles`, and
`RemoteLockedFungibles` storage types. Additionally, more checks were
added to `try_state` for these types.

## TODO
- [x] create tracking issue for `polkadot-fellows`
polkadot-fellows/runtimes#492
- [x] Add missing `MigrateToLatestXcmVersion` for westend
- [x] fix pallet-xcm `Queries`
- fails for Westend
https://github.com/paritytech/polkadot-sdk/actions/runs/11381324568/job/31662577532?pr=6092
- `V2` was removed from `Versioned*` stuff, but we have a live data with
V2 e.g. Queries - e.g. Kusama or Polkadot relay chains
```
VersionNotifier: {
        origin: {
          V2: {
            parents: 0
            interior: {
              X1: {
                Parachain: 2,124
              }
            }
          }
        }
        isActive: true
      } 
```

![image](https://github.com/user-attachments/assets/f59f761b-46a7-4def-8aea-45c4e41c0a00)
- [x] fix also for `RemoteLockedFungibles` 
- [x] fix also for `LockedFungibles`

## Follow-ups

- [ ] deploy on Westend chains before XCMv5
- [ ] paritytech#6188

---------

Co-authored-by: command-bot <>
Co-authored-by: GitHub Action <[email protected]>
Co-authored-by: Francisco Aguirre <[email protected]>

polkadot/runtime/westend/src/lib.rs

@@ -1809,6 +1809,8 @@ pub mod migrations {
 		>,
 		parachains_shared::migration::MigrateToV1<Runtime>,
 		parachains_scheduler::migration::MigrateV2ToV3<Runtime>,
+		// permanent
+		pallet_xcm::migration::MigrateToLatestXcmVersion<Runtime>,
 	);
 }
 

polkadot/xcm/docs/src/cookbook/relay_token_transactor/parachain/xcm_config.rs

@@ -168,7 +168,7 @@ impl pallet_xcm::Config for Runtime {
 	type UniversalLocation = UniversalLocation;
 	// No version discovery needed
 	const VERSION_DISCOVERY_QUEUE_SIZE: u32 = 0;
-	type AdvertisedXcmVersion = frame::traits::ConstU32<3>;
+	type AdvertisedXcmVersion = pallet_xcm::CurrentXcmVersion;
 	type AdminOrigin = frame_system::EnsureRoot<AccountId>;
 	// No locking
 	type TrustedLockers = ();

polkadot/xcm/docs/src/cookbook/relay_token_transactor/relay_chain/xcm_config.rs

@@ -142,7 +142,7 @@ impl pallet_xcm::Config for Runtime {
 	type UniversalLocation = UniversalLocation;
 	// No version discovery needed
 	const VERSION_DISCOVERY_QUEUE_SIZE: u32 = 0;
-	type AdvertisedXcmVersion = frame::traits::ConstU32<3>;
+	type AdvertisedXcmVersion = pallet_xcm::CurrentXcmVersion;
 	type AdminOrigin = frame_system::EnsureRoot<AccountId>;
 	// No locking
 	type TrustedLockers = ();

polkadot/xcm/pallet-xcm/src/lib.rs

@@ -2807,6 +2807,44 @@ impl<T: Config> Pallet<T> {
 	/// set.
 	#[cfg(any(feature = "try-runtime", test))]
 	pub fn do_try_state() -> Result<(), TryRuntimeError> {
+		use migration::data::NeedsMigration;
+
+		// Take the minimum version between `SafeXcmVersion` and `latest - 1` and ensure that the
+		// operational data is stored at least at that version, for example, to prevent issues when
+		// removing older XCM versions.
+		let minimal_allowed_xcm_version = if let Some(safe_xcm_version) = SafeXcmVersion::<T>::get()
+		{
+			XCM_VERSION.saturating_sub(1).min(safe_xcm_version)
+		} else {
+			XCM_VERSION.saturating_sub(1)
+		};
+
+		// check `Queries`
+		ensure!(
+			!Queries::<T>::iter_values()
+				.any(|data| data.needs_migration(minimal_allowed_xcm_version)),
+			TryRuntimeError::Other("`Queries` data should be migrated to the higher xcm version!")
+		);
+
+		// check `LockedFungibles`
+		ensure!(
+			!LockedFungibles::<T>::iter_values()
+				.any(|data| data.needs_migration(minimal_allowed_xcm_version)),
+			TryRuntimeError::Other(
+				"`LockedFungibles` data should be migrated to the higher xcm version!"
+			)
+		);
+
+		// check `RemoteLockedFungibles`
+		ensure!(
+			!RemoteLockedFungibles::<T>::iter()
+				.any(|(key, data)| key.needs_migration(minimal_allowed_xcm_version) ||
+					data.needs_migration(minimal_allowed_xcm_version)),
+			TryRuntimeError::Other(
+				"`RemoteLockedFungibles` data should be migrated to the higher xcm version!"
+			)
+		);
+
 		// if migration has been already scheduled, everything is ok and data will be eventually
 		// migrated
 		if CurrentMigration::<T>::exists() {
@@ -2887,7 +2925,7 @@ impl<T: Config> xcm_executor::traits::Enact for UnlockTicket<T> {
 		let mut maybe_remove_index = None;
 		let mut locked = BalanceOf::<T>::zero();
 		let mut found = false;
-		// We could just as well do with with an into_iter, filter_map and collect, however this way
+		// We could just as well do with an into_iter, filter_map and collect, however this way
 		// avoids making an allocation.
 		for (i, x) in locks.iter_mut().enumerate() {
 			if x.1.try_as::<_>().defensive() == Ok(&self.unlocker) {
@@ -3268,7 +3306,7 @@ impl<T: Config> OnResponse for Pallet<T> {
 					});
 					return Weight::zero()
 				}
-				return match maybe_notify {
+				match maybe_notify {
 					Some((pallet_index, call_index)) => {
 						// This is a bit horrible, but we happen to know that the `Call` will
 						// be built by `(pallet_index: u8, call_index: u8, QueryId, Response)`.