Clear other messages before dry-run to get only the ones produced during

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

@@ -408,6 +408,10 @@ 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 get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		ViaBridgeHubExporter::<T, I>::get_messages()
 	}

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

@@ -130,6 +130,10 @@ impl SendXcm for TestToBridgeHubSender {
 }
 
 impl InspectMessageQueues for TestToBridgeHubSender {
+	fn clear_messages() {
+		SENT_XCM.with(|q| q.borrow_mut().clear());
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		SENT_XCM.with(|q| {
 			(*q.borrow())

bridges/modules/xcm-bridge-hub/src/mock.rs

@@ -295,6 +295,10 @@ impl SendXcm for TestExportXcmWithXcmOverBridge {
 	}
 }
 impl InspectMessageQueues for TestExportXcmWithXcmOverBridge {
+	fn clear_messages() {
+		todo!()
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		todo!()
 	}

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

@@ -1540,6 +1540,10 @@ impl<T: Config> UpwardMessageSender for Pallet<T> {
 }
 
 impl<T: Config> InspectMessageQueues for Pallet<T> {
+	fn clear_messages() {
+		PendingUpwardMessages::<T>::kill();
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		use xcm::prelude::*;
 

cumulus/pallets/xcmp-queue/src/lib.rs

@@ -64,7 +64,7 @@ use frame_support::{
 	defensive, defensive_assert,
 	traits::{Defensive, EnqueueMessage, EnsureOrigin, Get, QueueFootprint, QueuePausedQuery},
 	weights::{Weight, WeightMeter},
-	BoundedVec,
+	BoundedVec, StoragePrefixedMap,
 };
 use pallet_message_queue::OnQueueChanged;
 use polkadot_runtime_common::xcm_sender::PriceForMessageDelivery;
@@ -1008,6 +1008,11 @@ impl<T: Config> SendXcm for Pallet<T> {
 }
 
 impl<T: Config> InspectMessageQueues for Pallet<T> {
+	fn clear_messages() {
+		// Best effort.
+		let _ = OutboundXcmpMessages::<T>::clear(u32::MAX, None);
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		use xcm::prelude::*;
 

cumulus/primitives/utility/src/lib.rs

@@ -99,6 +99,10 @@ where
 impl<T: UpwardMessageSender + InspectMessageQueues, W, P> InspectMessageQueues
 	for ParentAsUmp<T, W, P>
 {
+	fn clear_messages() {
+		T::clear_messages();
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		T::get_messages()
 	}

polkadot/runtime/common/src/xcm_sender.rs

@@ -19,7 +19,7 @@
 use alloc::vec::Vec;
 use codec::{Decode, Encode};
 use core::marker::PhantomData;
-use frame_support::traits::Get;
+use frame_support::{traits::Get, StoragePrefixedMap};
 use frame_system::pallet_prelude::BlockNumberFor;
 use polkadot_primitives::Id as ParaId;
 use polkadot_runtime_parachains::{
@@ -141,6 +141,11 @@ where
 }
 
 impl<T: dmp::Config, W, P> InspectMessageQueues for ChildParachainRouter<T, W, P> {
+	fn clear_messages() {
+		// Best effort.
+		let _ = dmp::DownwardMessageQueues::<T>::clear(u32::MAX, None);
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		dmp::DownwardMessageQueues::<T>::iter()
 			.map(|(para_id, messages)| {

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

@@ -2457,10 +2457,14 @@ impl<T: Config> Pallet<T> {
 		<RuntimeCall as Dispatchable>::RuntimeOrigin: From<OriginCaller>,
 	{
 		crate::Pallet::<Runtime>::set_record_xcm(true);
-		frame_system::Pallet::<Runtime>::reset_events(); // To make sure we only record events from current call.
+		// Clear other messages in queues...
+		Router::clear_messages();
+		// ...and reset events to make sure we only record events from current call.
+		frame_system::Pallet::<Runtime>::reset_events();
 		let result = call.dispatch(origin.into());
 		crate::Pallet::<Runtime>::set_record_xcm(false);
 		let local_xcm = crate::Pallet::<Runtime>::recorded_xcm();
+		// Should only get messages from this call since we cleared previous ones.
 		let forwarded_xcms = Router::get_messages();
 		let events: Vec<<Runtime as frame_system::Config>::RuntimeEvent> =
 			frame_system::Pallet::<Runtime>::read_events_no_consensus()

polkadot/xcm/xcm-builder/src/routing.rs

@@ -62,6 +62,10 @@ impl<Inner: SendXcm> SendXcm for WithUniqueTopic<Inner> {
 	}
 }
 impl<Inner: InspectMessageQueues> InspectMessageQueues for WithUniqueTopic<Inner> {
+	fn clear_messages() {
+		Inner::clear_messages()
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		Inner::get_messages()
 	}
@@ -149,12 +153,21 @@ impl EnsureDelivery for Tuple {
 /// Inspects messages in queues.
 /// Meant to be used in runtime APIs, not in runtimes.
 pub trait InspectMessageQueues {
+	/// Clear the queues at the beginning of Runtime API call, so that subsequent
+	/// `Self::get_messages()` will return only messages generated by said Runtime API.
+	fn clear_messages();
 	/// Get queued messages and their destinations.
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)>;
 }
 
 #[impl_trait_for_tuples::impl_for_tuples(30)]
 impl InspectMessageQueues for Tuple {
+	fn clear_messages() {
+		for_tuples!( #(
+			Tuple::clear_messages();
+		)* );
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		let mut messages = Vec::new();
 

polkadot/xcm/xcm-builder/src/universal_exports.rs

@@ -340,6 +340,10 @@ impl<Bridges: ExporterFor, Router: SendXcm, UniversalLocation: Get<InteriorLocat
 impl<Bridges, Router: InspectMessageQueues, UniversalLocation> InspectMessageQueues
 	for SovereignPaidRemoteExporter<Bridges, Router, UniversalLocation>
 {
+	fn clear_messages() {
+		Router::clear_messages()
+	}
+
 	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
 		Router::get_messages()
 	}

prdoc/pr_5581.prdoc

@@ -0,0 +1,28 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Clear other messages before dry-running
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      The DryRunApi.dry_run_call and DryRunApi.dry_run_xcm functions just returned
+      in forwarded_xcms all the existing messages in the queues at the time.
+      Now messages are cleared before dry-running, meaning only the messages produced
+      by the call (or xcm) will be returned.
+
+crates:
+  - name: pallet-xcm
+    bump: minor
+  - name: staging-xcm-builder
+    bump: major
+  - name: pallet-xcm-bridge-hub-router
+    bump: minor
+  - name: cumulus-pallet-parachain-system
+    bump: minor
+  - name: cumulus-pallet-xcmp-queue
+    bump: minor
+  - name: cumulus-primitives-utility
+    bump: minor
+  - name: polkadot-runtime-common
+    bump: minor