Added tests for XCM barriers: AllowSubscriptions, WithUniqueTopic and TrailingSetTopicAsId (#3955)

Closes: https://github.com/paritytech/polkadot-sdk/issues/1756

polkadot/xcm/xcm-builder/src/tests/barriers.rs

@@ -309,3 +309,62 @@ fn suspension_should_work() {
 	);
 	assert_eq!(r, Ok(()));
 }
+
+#[test]
+fn allow_subscriptions_from_should_work() {
+	// allow only parent
+	AllowSubsFrom::set(vec![Location::parent()]);
+
+	let valid_xcm_1 = Xcm::<TestCall>(vec![SubscribeVersion {
+		query_id: 42,
+		max_response_weight: Weight::from_parts(5000, 5000),
+	}]);
+	let valid_xcm_2 = Xcm::<TestCall>(vec![UnsubscribeVersion]);
+	let invalid_xcm_1 = Xcm::<TestCall>(vec![
+		SetAppendix(Xcm(vec![])),
+		SubscribeVersion { query_id: 42, max_response_weight: Weight::from_parts(5000, 5000) },
+	]);
+	let invalid_xcm_2 = Xcm::<TestCall>(vec![
+		SubscribeVersion { query_id: 42, max_response_weight: Weight::from_parts(5000, 5000) },
+		SetTopic([0; 32]),
+	]);
+
+	let test_data = vec![
+		(
+			valid_xcm_1.clone(),
+			Parachain(1).into_location(),
+			// not allowed origin
+			Err(ProcessMessageError::Unsupported),
+		),
+		(valid_xcm_1, Location::parent(), Ok(())),
+		(
+			valid_xcm_2.clone(),
+			Parachain(1).into_location(),
+			// not allowed origin
+			Err(ProcessMessageError::Unsupported),
+		),
+		(valid_xcm_2, Location::parent(), Ok(())),
+		(
+			invalid_xcm_1,
+			Location::parent(),
+			// invalid XCM
+			Err(ProcessMessageError::BadFormat),
+		),
+		(
+			invalid_xcm_2,
+			Location::parent(),
+			// invalid XCM
+			Err(ProcessMessageError::BadFormat),
+		),
+	];
+
+	for (mut message, origin, expected_result) in test_data {
+		let r = AllowSubscriptionsFrom::<IsInVec<AllowSubsFrom>>::should_execute(
+			&origin,
+			message.inner_mut(),
+			Weight::from_parts(10, 10),
+			&mut props(Weight::zero()),
+		);
+		assert_eq!(r, expected_result, "Failed for origin: {origin:?} and message: {message:?}");
+	}
+}

polkadot/xcm/xcm-builder/src/tests/mod.rs

@@ -36,6 +36,7 @@ mod locking;
 mod origins;
 mod pay;
 mod querying;
+mod routing;
 mod transacting;
 mod version_subscriptions;
 mod weight;

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

@@ -0,0 +1,95 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+use super::*;
+use frame_support::{assert_ok, traits::Everything};
+use xcm_executor::traits::Properties;
+
+fn props() -> Properties {
+	Properties { weight_credit: Weight::zero(), message_id: None }
+}
+
+#[test]
+fn trailing_set_topic_as_id_with_unique_topic_should_work() {
+	type AllowSubscriptions = AllowSubscriptionsFrom<Everything>;
+
+	// check the validity of XCM for the `AllowSubscriptions` barrier
+	let valid_xcm = Xcm::<()>(vec![SubscribeVersion {
+		query_id: 42,
+		max_response_weight: Weight::from_parts(5000, 5000),
+	}]);
+	assert_eq!(
+		AllowSubscriptions::should_execute(
+			&Location::parent(),
+			valid_xcm.clone().inner_mut(),
+			Weight::from_parts(10, 10),
+			&mut props(),
+		),
+		Ok(())
+	);
+
+	// simulate sending `valid_xcm` with the `WithUniqueTopic` router
+	let mut sent_xcm = sp_io::TestExternalities::default().execute_with(|| {
+		assert_ok!(send_xcm::<WithUniqueTopic<TestMessageSender>>(Location::parent(), valid_xcm,));
+		sent_xcm()
+	});
+	assert_eq!(1, sent_xcm.len());
+
+	// `sent_xcm` should contain `SubscribeVersion` and have `SetTopic` added
+	let mut sent_xcm = sent_xcm.remove(0).1;
+	let _ = sent_xcm
+		.0
+		.matcher()
+		.assert_remaining_insts(2)
+		.expect("two instructions")
+		.match_next_inst(|instr| match instr {
+			SubscribeVersion { .. } => Ok(()),
+			_ => Err(ProcessMessageError::BadFormat),
+		})
+		.expect("expected instruction `SubscribeVersion`")
+		.match_next_inst(|instr| match instr {
+			SetTopic(..) => Ok(()),
+			_ => Err(ProcessMessageError::BadFormat),
+		})
+		.expect("expected instruction `SetTopic`");
+
+	// `sent_xcm` contains `SetTopic` and is now invalid for `AllowSubscriptions`
+	assert_eq!(
+		AllowSubscriptions::should_execute(
+			&Location::parent(),
+			sent_xcm.clone().inner_mut(),
+			Weight::from_parts(10, 10),
+			&mut props(),
+		),
+		Err(ProcessMessageError::BadFormat)
+	);
+
+	// let's apply `TrailingSetTopicAsId` before `AllowSubscriptions`
+	let mut props = props();
+	assert!(props.message_id.is_none());
+
+	// should pass, and the `message_id` is set
+	assert_eq!(
+		TrailingSetTopicAsId::<AllowSubscriptions>::should_execute(
+			&Location::parent(),
+			sent_xcm.clone().inner_mut(),
+			Weight::from_parts(10, 10),
+			&mut props,
+		),
+		Ok(())
+	);
+	assert!(props.message_id.is_some());
+}

polkadot/xcm/xcm-builder/src/tests/version_subscriptions.rs

@@ -27,16 +27,32 @@ fn simple_version_subscriptions_should_work() {
 	]);
 	let mut hash = fake_message_hash(&message);
 	let weight_limit = Weight::from_parts(20, 20);
-	let r = XcmExecutor::<TestConfig>::prepare_and_execute(
-		origin,
-		message,
-		&mut hash,
-		weight_limit,
-		Weight::zero(),
-	);
-	assert_eq!(r, Outcome::Error { error: XcmError::Barrier });
 
-	let origin = Parachain(1000);
+	// this case fails because the origin is not allowed
+	assert_eq!(
+		XcmExecutor::<TestConfig>::prepare_and_execute(
+			origin,
+			message.clone(),
+			&mut hash,
+			weight_limit,
+			Weight::zero(),
+		),
+		Outcome::Error { error: XcmError::Barrier }
+	);
+
+	// this case fails because the additional `SetAppendix` instruction is not allowed in the
+	// `AllowSubscriptionsFrom`
+	assert_eq!(
+		XcmExecutor::<TestConfig>::prepare_and_execute(
+			Parent,
+			message,
+			&mut hash,
+			weight_limit,
+			Weight::zero(),
+		),
+		Outcome::Error { error: XcmError::Barrier }
+	);
+
 	let message = Xcm::<TestCall>(vec![SubscribeVersion {
 		query_id: 42,
 		max_response_weight: Weight::from_parts(5000, 5000),

polkadot/xcm/xcm-executor/src/traits/should_execute.rs

@@ -33,9 +33,9 @@ pub struct Properties {
 /// Trait to determine whether the execution engine should actually execute a given XCM.
 ///
 /// Can be amalgamated into a tuple to have multiple trials. If any of the tuple elements returns
-/// `Ok()`, the execution stops. Else, `Err(_)` is returned if all elements reject the message.
+/// `Ok(())`, the execution stops. Else, `Err(_)` is returned if all elements reject the message.
 pub trait ShouldExecute {
-	/// Returns `true` if the given `message` may be executed.
+	/// Returns `Ok(())` if the given `message` may be executed.
 	///
 	/// - `origin`: The origin (sender) of the message.
 	/// - `instructions`: The message itself.