[stable2407] Backport #5913 (#6004)

Backport #5913 into `stable2407` from franciscoaguirre.

See the
[documentation](https://github.com/paritytech/polkadot-sdk/blob/master/docs/BACKPORT.md)
on how to use this bot.

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---------

Co-authored-by: Francisco Aguirre <[email protected]>
Co-authored-by: Egor_P <[email protected]>

bridges/modules/xcm-bridge-hub-router/src/lib.rs

@@ -96,7 +96,7 @@ pub mod pallet {
 		/// Origin of the sibling bridge hub that is allowed to report bridge status.
 		type BridgeHubOrigin: EnsureOrigin<Self::RuntimeOrigin>;
 		/// Actual message sender (`HRMP` or `DMP`) to the sibling bridge hub location.
-		type ToBridgeHubSender: SendXcm + InspectMessageQueues;
+		type ToBridgeHubSender: SendXcm;
 		/// Underlying channel with the sibling bridge hub. It must match the channel, used
 		/// by the `Self::ToBridgeHubSender`.
 		type WithBridgeHubChannel: XcmChannelStatusProvider;
@@ -398,12 +398,12 @@ impl<T: Config<I>, I: 'static> SendXcm for Pallet<T, I> {
 }
 
 impl<T: Config<I>, I: 'static> InspectMessageQueues for Pallet<T, I> {
-	fn clear_messages() {
-		ViaBridgeHubExporter::<T, I>::clear_messages()
-	}
+	fn clear_messages() {}
 
+	/// This router needs to implement `InspectMessageQueues` but doesn't have to
+	/// return any messages, since it just reuses the `XcmpQueue` router.
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
-		ViaBridgeHubExporter::<T, I>::get_messages()
+		Vec::new()
 	}
 }
 
@@ -648,34 +648,13 @@ mod tests {
 	}
 
 	#[test]
-	fn get_messages_works() {
+	fn get_messages_does_not_return_anything() {
 		run_test(|| {
 			assert_ok!(send_xcm::<XcmBridgeHubRouter>(
 				(Parent, Parent, GlobalConsensus(BridgedNetworkId::get()), Parachain(1000)).into(),
 				vec![ClearOrigin].into()
 			));
-			assert_eq!(
-				XcmBridgeHubRouter::get_messages(),
-				vec![(
-					VersionedLocation::V4((Parent, Parachain(1002)).into()),
-					vec![VersionedXcm::V4(
-						Xcm::builder()
-							.withdraw_asset((Parent, 1_002_000))
-							.buy_execution((Parent, 1_002_000), Unlimited)
-							.set_appendix(
-								Xcm::builder_unsafe()
-									.deposit_asset(AllCounted(1), (Parent, Parachain(1000)))
-									.build()
-							)
-							.export_message(
-								Kusama,
-								Parachain(1000),
-								Xcm::builder_unsafe().clear_origin().build()
-							)
-							.build()
-					)],
-				),],
-			);
+			assert_eq!(XcmBridgeHubRouter::get_messages(), vec![]);
 		});
 	}
 }

cumulus/pallets/parachain-system/src/lib.rs

@@ -1623,7 +1623,11 @@ impl<T: Config> InspectMessageQueues for Pallet<T> {
 			.map(|encoded_message| VersionedXcm::<()>::decode(&mut &encoded_message[..]).unwrap())
 			.collect();
 
-		vec![(VersionedLocation::V4(Parent.into()), messages)]
+		if messages.is_empty() {
+			vec![]
+		} else {
+			vec![(VersionedLocation::from(Location::parent()), messages)]
+		}
 	}
 }