XCM: Fix issue with RequestUnlock (#7278)

* XCM: Fix issue with RequestUnlock

* Leave API changes for v4

* Fix clippy errors

* Fix tests

---------

Co-authored-by: parity-processbot <>

polkadot/xcm/xcm-simulator/example/src/lib.rs

@@ -272,7 +272,7 @@ mod tests {
 	}
 
 	#[test]
-	fn remote_locking() {
+	fn remote_locking_and_unlocking() {
 		MockNet::reset();
 
 		let locked_amount = 100;
@@ -280,7 +280,7 @@ mod tests {
 		ParaB::execute_with(|| {
 			let message = Xcm(vec![LockAsset {
 				asset: (Here, locked_amount).into(),
-				unlocker: (Parachain(1),).into(),
+				unlocker: Parachain(1).into(),
 			}]);
 			assert_ok!(ParachainPalletXcm::send_xcm(Here, Parent, message.clone()));
 		});
@@ -306,6 +306,28 @@ mod tests {
 				}])]
 			);
 		});
+
+		ParaB::execute_with(|| {
+			// Request unlocking part of the funds on the relay chain
+			let message = Xcm(vec![RequestUnlock {
+				asset: (Parent, locked_amount - 50).into(),
+				locker: Parent.into(),
+			}]);
+			assert_ok!(ParachainPalletXcm::send_xcm(Here, (Parent, Parachain(1)), message));
+		});
+
+		Relay::execute_with(|| {
+			use pallet_balances::{BalanceLock, Reasons};
+			// Lock is reduced
+			assert_eq!(
+				relay_chain::Balances::locks(&child_account_id(2)),
+				vec![BalanceLock {
+					id: *b"py/xcmlk",
+					amount: locked_amount - 50,
+					reasons: Reasons::All
+				}]
+			);
+		});
 	}
 
 	/// Scenario:

polkadot/xcm/xcm-simulator/example/src/parachain.rs

@@ -17,9 +17,10 @@
 //! Parachain runtime mock.
 
 use codec::{Decode, Encode};
+use core::marker::PhantomData;
 use frame_support::{
 	construct_runtime, parameter_types,
-	traits::{EnsureOrigin, EnsureOriginWithArg, Everything, EverythingBut, Nothing},
+	traits::{ContainsPair, EnsureOrigin, EnsureOriginWithArg, Everything, EverythingBut, Nothing},
 	weights::{constants::WEIGHT_REF_TIME_PER_SECOND, Weight},
 };
 
@@ -27,7 +28,7 @@ use frame_system::EnsureRoot;
 use sp_core::{ConstU32, H256};
 use sp_runtime::{
 	testing::Header,
-	traits::{Hash, IdentityLookup},
+	traits::{Get, Hash, IdentityLookup},
 	AccountId32,
 };
 use sp_std::prelude::*;
@@ -238,7 +239,7 @@ impl Config for XcmConfig {
 	type Trader = FixedRateOfFungible<KsmPerSecondPerByte, ()>;
 	type ResponseHandler = ();
 	type AssetTrap = ();
-	type AssetLocker = ();
+	type AssetLocker = PolkadotXcm;
 	type AssetExchanger = ();
 	type AssetClaims = ();
 	type SubscriptionService = ();
@@ -325,7 +326,7 @@ pub mod mock_msg_queue {
 				Ok(xcm) => {
 					let location = (Parent, Parachain(sender.into()));
 					match T::XcmExecutor::execute_xcm(location, xcm, message_hash, max_weight) {
-						Outcome::Error(e) => (Err(e.clone()), Event::Fail(Some(hash), e)),
+						Outcome::Error(e) => (Err(e), Event::Fail(Some(hash), e)),
 						Outcome::Complete(w) => (Ok(w), Event::Success(Some(hash))),
 						// As far as the caller is concerned, this was dispatched without error, so
 						// we just report the weight used.
@@ -349,7 +350,7 @@ pub mod mock_msg_queue {
 				let _ = XcmpMessageFormat::decode(&mut data_ref)
 					.expect("Simulator encodes with versioned xcm format; qed");
 
-				let mut remaining_fragments = &data_ref[..];
+				let mut remaining_fragments = data_ref;
 				while !remaining_fragments.is_empty() {
 					if let Ok(xcm) =
 						VersionedXcm::<T::RuntimeCall>::decode(&mut remaining_fragments)
@@ -403,6 +404,22 @@ parameter_types! {
 	pub ReachableDest: Option<MultiLocation> = Some(Parent.into());
 }
 
+pub struct TrustedLockerCase<T>(PhantomData<T>);
+impl<T: Get<(MultiLocation, MultiAssetFilter)>> ContainsPair<MultiLocation, MultiAsset>
+	for TrustedLockerCase<T>
+{
+	fn contains(origin: &MultiLocation, asset: &MultiAsset) -> bool {
+		let (o, a) = T::get();
+		a.matches(asset) && &o == origin
+	}
+}
+
+parameter_types! {
+	pub RelayTokenForRelay: (MultiLocation, MultiAssetFilter) = (Parent.into(), Wild(AllOf { id: Concrete(Parent.into()), fun: WildFungible }));
+}
+
+pub type TrustedLockers = TrustedLockerCase<RelayTokenForRelay>;
+
 impl pallet_xcm::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type SendXcmOrigin = EnsureXcmOrigin<RuntimeOrigin, LocalOriginToLocation>;
@@ -420,7 +437,7 @@ impl pallet_xcm::Config for Runtime {
 	type AdvertisedXcmVersion = pallet_xcm::CurrentXcmVersion;
 	type Currency = Balances;
 	type CurrencyMatcher = ();
-	type TrustedLockers = ();
+	type TrustedLockers = TrustedLockers;
 	type SovereignAccountOf = LocationToAccountId;
 	type MaxLockers = ConstU32<8>;
 	type MaxRemoteLockConsumers = ConstU32<0>;