Tweaks to XCM for Benchmarking (#4283)

* tweaks to xcm stuff for benchmarking

* Update xcm/xcm-executor/src/lib.rs

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

@@ -1261,6 +1261,12 @@ pub mod pallet {
 			VersionNotifyTargets::<T>::remove(XCM_VERSION, LatestVersionedMultiLocation(dest));
 			Ok(())
 		}
+
+		/// Return true if a location is subscribed to XCM version changes.
+		fn is_subscribed(dest: &MultiLocation) -> bool {
+			let versioned_dest = LatestVersionedMultiLocation(dest);
+			VersionNotifyTargets::<T>::contains_key(XCM_VERSION, versioned_dest)
+		}
 	}
 
 	impl<T: Config> DropAssets for Pallet<T> {

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

@@ -25,6 +25,9 @@ mod mock;
 #[cfg(test)]
 mod tests;
 
+#[cfg(feature = "std")]
+pub mod test_utils;
+
 mod location_conversion;
 pub use location_conversion::{
 	Account32Hash, AccountId32Aliases, AccountKey20Aliases, ChildParachainConvertsVia,

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

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-use crate::barriers::AllowSubscriptionsFrom;
+use crate::{barriers::AllowSubscriptionsFrom, test_utils::*};
 pub use crate::{
 	AllowKnownQueryResponses, AllowTopLevelPaidExecutionFrom, AllowUnpaidExecutionFrom,
 	FixedRateOfFungible, FixedWeightBounds, LocationInverter, TakeWeightCredit,
@@ -36,7 +36,6 @@ pub use sp_std::{
 	marker::PhantomData,
 };
 pub use xcm::latest::prelude::*;
-use xcm_executor::traits::{ClaimAssets, DropAssets, VersionChangeNotifier};
 pub use xcm_executor::{
 	traits::{ConvertOrigin, FilterAssetLocation, InvertLocation, OnResponse, TransactAsset},
 	Assets, Config,
@@ -273,57 +272,6 @@ pub type TestBarrier = (
 	AllowSubscriptionsFrom<IsInVec<AllowSubsFrom>>,
 );
 
-parameter_types! {
-	pub static TrappedAssets: Vec<(MultiLocation, MultiAssets)> = vec![];
-}
-
-pub struct TestAssetTrap;
-
-impl DropAssets for TestAssetTrap {
-	fn drop_assets(origin: &MultiLocation, assets: Assets) -> Weight {
-		let mut t: Vec<(MultiLocation, MultiAssets)> = TrappedAssets::get();
-		t.push((origin.clone(), assets.into()));
-		TrappedAssets::set(t);
-		5
-	}
-}
-
-impl ClaimAssets for TestAssetTrap {
-	fn claim_assets(origin: &MultiLocation, ticket: &MultiLocation, what: &MultiAssets) -> bool {
-		let mut t: Vec<(MultiLocation, MultiAssets)> = TrappedAssets::get();
-		if let (0, X1(GeneralIndex(i))) = (ticket.parents, &ticket.interior) {
-			if let Some((l, a)) = t.get(*i as usize) {
-				if l == origin && a == what {
-					t.swap_remove(*i as usize);
-					TrappedAssets::set(t);
-					return true
-				}
-			}
-		}
-		false
-	}
-}
-
-parameter_types! {
-	pub static SubscriptionRequests: Vec<(MultiLocation, Option<(QueryId, u64)>)> = vec![];
-}
-pub struct TestSubscriptionService;
-
-impl VersionChangeNotifier for TestSubscriptionService {
-	fn start(location: &MultiLocation, query_id: QueryId, max_weight: u64) -> XcmResult {
-		let mut r = SubscriptionRequests::get();
-		r.push((location.clone(), Some((query_id, max_weight))));
-		SubscriptionRequests::set(r);
-		Ok(())
-	}
-	fn stop(location: &MultiLocation) -> XcmResult {
-		let mut r = SubscriptionRequests::get();
-		r.push((location.clone(), None));
-		SubscriptionRequests::set(r);
-		Ok(())
-	}
-}
-
 pub struct TestConfig;
 impl Config for TestConfig {
 	type Call = TestCall;

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

@@ -0,0 +1,83 @@
+// Copyright 2020 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/>.
+
+// Shared test utilities and implementations for the XCM Builder.
+
+use frame_support::{dispatch::Weight, parameter_types};
+use sp_std::vec::Vec;
+pub use xcm::latest::prelude::*;
+use xcm_executor::traits::{ClaimAssets, DropAssets, VersionChangeNotifier};
+pub use xcm_executor::{
+	traits::{ConvertOrigin, FilterAssetLocation, InvertLocation, OnResponse, TransactAsset},
+	Assets, Config,
+};
+
+parameter_types! {
+	pub static SubscriptionRequests: Vec<(MultiLocation, Option<(QueryId, u64)>)> = vec![];
+}
+
+pub struct TestSubscriptionService;
+
+impl VersionChangeNotifier for TestSubscriptionService {
+	fn start(location: &MultiLocation, query_id: QueryId, max_weight: u64) -> XcmResult {
+		let mut r = SubscriptionRequests::get();
+		r.push((location.clone(), Some((query_id, max_weight))));
+		SubscriptionRequests::set(r);
+		Ok(())
+	}
+	fn stop(location: &MultiLocation) -> XcmResult {
+		let mut r = SubscriptionRequests::get();
+		r.retain(|(l, _q)| l != location);
+		r.push((location.clone(), None));
+		SubscriptionRequests::set(r);
+		Ok(())
+	}
+	fn is_subscribed(location: &MultiLocation) -> bool {
+		let r = SubscriptionRequests::get();
+		r.iter().any(|(l, q)| l == location && q.is_some())
+	}
+}
+
+parameter_types! {
+	pub static TrappedAssets: Vec<(MultiLocation, MultiAssets)> = vec![];
+}
+
+pub struct TestAssetTrap;
+
+impl DropAssets for TestAssetTrap {
+	fn drop_assets(origin: &MultiLocation, assets: Assets) -> Weight {
+		let mut t: Vec<(MultiLocation, MultiAssets)> = TrappedAssets::get();
+		t.push((origin.clone(), assets.into()));
+		TrappedAssets::set(t);
+		5
+	}
+}
+
+impl ClaimAssets for TestAssetTrap {
+	fn claim_assets(origin: &MultiLocation, ticket: &MultiLocation, what: &MultiAssets) -> bool {
+		let mut t: Vec<(MultiLocation, MultiAssets)> = TrappedAssets::get();
+		if let (0, X1(GeneralIndex(i))) = (ticket.parents, &ticket.interior) {
+			if let Some((l, a)) = t.get(*i as usize) {
+				if l == origin && a == what {
+					t.swap_remove(*i as usize);
+					TrappedAssets::set(t);
+					return true
+				}
+			}
+		}
+		false
+	}
+}

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

@@ -14,7 +14,7 @@
 // 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::{mock::*, *};
+use super::{mock::*, test_utils::*, *};
 use frame_support::{assert_err, weights::constants::WEIGHT_PER_SECOND};
 use xcm::latest::prelude::*;
 use xcm_executor::{traits::*, Config, XcmExecutor};

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

@@ -139,26 +139,7 @@ impl<Config: config::Config> ExecuteXcm<Config::Call> for XcmExecutor<Config> {
 			}
 		}
 
-		vm.refund_surplus();
+		vm.post_execute(xcm_weight)
-		drop(vm.trader);
-
-		let mut weight_used = xcm_weight.saturating_sub(vm.total_surplus);
-
-		if !vm.holding.is_empty() {
-			log::trace!(target: "xcm::execute_xcm_in_credit", "Trapping assets in holding register: {:?} (original_origin: {:?})", vm.holding, vm.original_origin);
-			let trap_weight = Config::AssetTrap::drop_assets(&vm.original_origin, vm.holding);
-			weight_used.saturating_accrue(trap_weight);
-		};
-
-		match vm.error {
-			None => Outcome::Complete(weight_used),
-			// TODO: #2841 #REALWEIGHT We should deduct the cost of any instructions following
-			// the error which didn't end up being executed.
-			Some((_i, e)) => {
-				log::debug!(target: "xcm::execute_xcm_in_credit", "Execution errored at {:?}: {:?} (original_origin: {:?})", _i, e, vm.original_origin);
-				Outcome::Incomplete(weight_used, e)
-			},
-		}
 	}
 }
 
@@ -228,6 +209,31 @@ impl<Config: config::Config> XcmExecutor<Config> {
 		result
 	}
 
+	/// Execute any final operations after having executed the XCM message.
+	/// This includes refunding surplus weight, trapping extra holding funds, and returning any errors during execution.
+	pub fn post_execute(mut self, xcm_weight: Weight) -> Outcome {
+		self.refund_surplus();
+		drop(self.trader);
+
+		let mut weight_used = xcm_weight.saturating_sub(self.total_surplus);
+
+		if !self.holding.is_empty() {
+			log::trace!(target: "xcm::execute_xcm_in_credit", "Trapping assets in holding register: {:?} (original_origin: {:?})", self.holding, self.original_origin);
+			let trap_weight = Config::AssetTrap::drop_assets(&self.original_origin, self.holding);
+			weight_used.saturating_accrue(trap_weight);
+		};
+
+		match self.error {
+			None => Outcome::Complete(weight_used),
+			// TODO: #2841 #REALWEIGHT We should deduct the cost of any instructions following
+			// the error which didn't end up being executed.
+			Some((_i, e)) => {
+				log::debug!(target: "xcm::execute_xcm_in_credit", "Execution errored at {:?}: {:?} (original_origin: {:?})", _i, e, self.original_origin);
+				Outcome::Incomplete(weight_used, e)
+			},
+		}
+	}
+
 	/// Remove the registered error handler and return it. Do not refund its weight.
 	fn take_error_handler(&mut self) -> Xcm<Config::Call> {
 		let mut r = Xcm::<Config::Call>(vec![]);

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

@@ -58,6 +58,9 @@ pub trait VersionChangeNotifier {
 	/// Stop notifying `location` should the XCM change. Returns an error if there is no existing
 	/// notification set up.
 	fn stop(location: &MultiLocation) -> XcmResult;
+
+	/// Return true if a location is subscribed to XCM version changes.
+	fn is_subscribed(location: &MultiLocation) -> bool;
 }
 
 impl VersionChangeNotifier for () {
@@ -67,4 +70,7 @@ impl VersionChangeNotifier for () {
 	fn stop(_: &MultiLocation) -> XcmResult {
 		Err(XcmError::Unimplemented)
 	}
+	fn is_subscribed(_: &MultiLocation) -> bool {
+		false
+	}
 }