Introduce transactional processing for xcm instructions

runtime/kusama/src/xcm_config.rs

@@ -39,10 +39,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain, IsConcrete, MintLocation,
-	OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	CurrencyAdapter as XcmCurrencyAdapter, FrameTransactionalProcessor, IsChildSystemParachain,
+	IsConcrete, MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -346,6 +346,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 parameter_types! {

runtime/polkadot/src/xcm_config.rs

@@ -42,9 +42,9 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, BackingToPlurality,
 	ChildParachainAsNative, ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter,
-	IsConcrete, MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin,
+	FrameTransactionalProcessor, IsConcrete, MintLocation, OriginToPluralityVoice,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -347,6 +347,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 parameter_types! {

runtime/rococo/src/xcm_config.rs

@@ -38,10 +38,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, BackingToPlurality,
 	ChildParachainAsNative, ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, IsChildSystemParachain, IsConcrete,
-	MintLocation, SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation,
-	TakeWeightCredit, TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin,
-	WithUniqueTopic,
+	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, FrameTransactionalProcessor,
+	IsChildSystemParachain, IsConcrete, MintLocation, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -320,6 +320,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 parameter_types! {

runtime/test-runtime/src/xcm_config.rs

@@ -22,8 +22,8 @@ use frame_support::{
 use frame_system::EnsureRoot;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AllowUnpaidExecutionFrom, EnsureXcmOrigin, FixedWeightBounds, SignedAccountId32AsNative,
-	SignedToAccountId32,
+	AllowUnpaidExecutionFrom, EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor,
+	SignedAccountId32AsNative, SignedToAccountId32,
 };
 use xcm_executor::{
 	traits::{TransactAsset, WeightTrader},
@@ -74,6 +74,7 @@ impl TransactAsset for DummyAssetTransactor {
 	}
 }
 
+#[derive(Clone)]
 pub struct DummyWeightTrader;
 impl WeightTrader for DummyWeightTrader {
 	fn new() -> Self {
@@ -121,6 +122,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = super::RuntimeCall;
 	type SafeCallFilter = Everything;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 #[cfg(feature = "runtime-benchmarks")]

runtime/westend/src/xcm_config.rs

@@ -37,9 +37,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain, IsConcrete, MintLocation,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	CurrencyAdapter as XcmCurrencyAdapter, FrameTransactionalProcessor, IsChildSystemParachain,
+	IsConcrete, MintLocation, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
+	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -269,6 +270,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 /// Type to convert an `Origin` type value into a `MultiLocation` value which represents an interior location

xcm/pallet-xcm-benchmarks/src/fungible/mock.rs

@@ -26,7 +26,7 @@ use frame_support::{
 use sp_core::H256;
 use sp_runtime::traits::{BlakeTwo256, IdentityLookup};
 use xcm::latest::prelude::*;
-use xcm_builder::{AllowUnpaidExecutionFrom, MintLocation};
+use xcm_builder::{AllowUnpaidExecutionFrom, FrameTransactionalProcessor, MintLocation};
 
 type Block = frame_system::mocking::MockBlock<Test>;
 
@@ -152,6 +152,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = RuntimeCall;
 	type SafeCallFilter = Everything;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 impl crate::Config for Test {

xcm/pallet-xcm-benchmarks/src/generic/mock.rs

@@ -30,7 +30,7 @@ use xcm_builder::{
 		Assets, TestAssetExchanger, TestAssetLocker, TestAssetTrap, TestSubscriptionService,
 		TestUniversalAliases,
 	},
-	AliasForeignAccountId32, AllowUnpaidExecutionFrom,
+	AliasForeignAccountId32, AllowUnpaidExecutionFrom, FrameTransactionalProcessor,
 };
 use xcm_executor::traits::ConvertOrigin;
 
@@ -131,6 +131,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = RuntimeCall;
 	type SafeCallFilter = Everything;
 	type Aliasers = Aliasers;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 impl crate::Config for Test {

xcm/pallet-xcm/src/mock.rs

@@ -31,8 +31,8 @@ use xcm_builder::{
 	AccountId32Aliases, AllowKnownQueryResponses, AllowSubscriptionsFrom,
 	AllowTopLevelPaidExecutionFrom, Case, ChildParachainAsNative, ChildParachainConvertsVia,
 	ChildSystemParachainAsSuperuser, CurrencyAdapter as XcmCurrencyAdapter, FixedRateOfFungible,
-	FixedWeightBounds, IsConcrete, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit,
+	FixedWeightBounds, FrameTransactionalProcessor, IsConcrete, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 };
 use xcm_executor::XcmExecutor;
 
@@ -306,6 +306,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = RuntimeCall;
 	type SafeCallFilter = Everything;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, AnyNetwork>;

xcm/xcm-builder/src/lib.rs

@@ -107,3 +107,6 @@ pub use origin_aliases::AliasForeignAccountId32;
 
 mod pay;
 pub use pay::{FixedLocation, LocatableAssetId, PayAccountId32OnChainOverXcm, PayOverXcm};
+
+mod transactional;
+pub use transactional::FrameTransactionalProcessor;

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

@@ -21,7 +21,7 @@ use crate::{
 pub use crate::{
 	AliasForeignAccountId32, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowTopLevelPaidExecutionFrom, AllowUnpaidExecutionFrom, FixedRateOfFungible,
-	FixedWeightBounds, TakeWeightCredit,
+	FixedWeightBounds, FrameTransactionalProcessor, TakeWeightCredit,
 };
 use frame_support::traits::{ContainsPair, Everything};
 pub use frame_support::{
@@ -685,6 +685,7 @@ impl Config for TestConfig {
 	type CallDispatcher = TestCall;
 	type SafeCallFilter = Everything;
 	type Aliasers = AliasForeignAccountId32<SiblingPrefix>;
+	type TransactionalProcessor = ();
 }
 
 pub fn fungible_multi_asset(location: MultiLocation, amount: u128) -> MultiAsset {

xcm/xcm-builder/src/transactional.rs

@@ -0,0 +1,39 @@
+// Copyright 2021 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 frame_support::storage::{with_transaction_unchecked, TransactionOutcome};
+use xcm::latest::prelude::*;
+use xcm_executor::traits::ProcessTransaction;
+
+/// Transactional processor implementation using frame transactional layers.
+pub struct FrameTransactionalProcessor;
+impl ProcessTransaction for FrameTransactionalProcessor {
+	const IS_TRANSACTIONAL: bool = true;
+
+	fn process<F>(f: F) -> Result<(), XcmError>
+	where
+		F: FnOnce() -> Result<(), XcmError>,
+	{
+		// Is safe to use because of the `MAX_XCM_DECODE_DEPTH`.
+		with_transaction_unchecked(|| -> TransactionOutcome<Result<(), XcmError>> {
+			let outcome = f();
+			match &outcome {
+				Ok(_) => TransactionOutcome::Commit(Ok(())),
+				Err(err) => TransactionOutcome::Rollback(Err(*err)),
+			}
+		})
+	}
+}

xcm/xcm-builder/src/weight.rs

@@ -190,6 +190,16 @@ impl<T: Get<(AssetId, u128, u128)>, R: TakeRevenue> Drop for FixedRateOfFungible
 	}
 }
 
+impl<T, R> Clone for FixedRateOfFungible<T, R>
+where
+	T: Get<(AssetId, u128, u128)>,
+	R: TakeRevenue,
+{
+	fn clone(&self) -> FixedRateOfFungible<T, R> {
+		Self(self.0, self.1, PhantomData)
+	}
+}
+
 /// Weight trader which uses the configured `WeightToFee` to set the right price for weight and then
 /// places any weight bought into the right account.
 pub struct UsingComponents<
@@ -257,3 +267,16 @@ impl<
 		OnUnbalanced::on_unbalanced(Currency::issue(self.1));
 	}
 }
+
+impl<WeightToFee, AssetId, AccountId, Currency, OnUnbalanced> Clone
+	for UsingComponents<WeightToFee, AssetId, AccountId, Currency, OnUnbalanced>
+where
+	WeightToFee: WeightToFeeT<Balance = Currency::Balance>,
+	AssetId: Get<MultiLocation>,
+	Currency: CurrencyT<AccountId>,
+	OnUnbalanced: OnUnbalancedT<Currency::NegativeImbalance>,
+{
+	fn clone(&self) -> UsingComponents<WeightToFee, AssetId, AccountId, Currency, OnUnbalanced> {
+		Self(self.0, self.1, PhantomData)
+	}
+}

xcm/xcm-builder/tests/mock/mod.rs

@@ -34,8 +34,9 @@ use xcm_builder::{
 	AccountId32Aliases, AllowTopLevelPaidExecutionFrom, AllowUnpaidExecutionFrom,
 	ChildParachainAsNative, ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
 	CurrencyAdapter as XcmCurrencyAdapter, FixedRateOfFungible, FixedWeightBounds,
-	IsChildSystemParachain, IsConcrete, MintLocation, RespectSuspension, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	FrameTransactionalProcessor, IsChildSystemParachain, IsConcrete, MintLocation,
+	RespectSuspension, SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation,
+	TakeWeightCredit,
 };
 
 pub type AccountId = AccountId32;
@@ -203,6 +204,7 @@ impl xcm_executor::Config for XcmConfig {
 	type CallDispatcher = RuntimeCall;
 	type SafeCallFilter = Everything;
 	type Aliasers = Nothing;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, KusamaNetwork>;

xcm/xcm-executor/src/config.rs

@@ -16,8 +16,8 @@
 
 use crate::traits::{
 	AssetExchange, AssetLock, CallDispatcher, ClaimAssets, ConvertOrigin, DropAssets, ExportXcm,
-	FeeManager, OnResponse, ShouldExecute, TransactAsset, VersionChangeNotifier, WeightBounds,
-	WeightTrader,
+	FeeManager, OnResponse, ProcessTransaction, ShouldExecute, TransactAsset,
+	VersionChangeNotifier, WeightBounds, WeightTrader,
 };
 use frame_support::{
 	dispatch::{Dispatchable, GetDispatchInfo, Parameter, PostDispatchInfo},
@@ -59,7 +59,7 @@ pub trait Config {
 	type Weigher: WeightBounds<Self::RuntimeCall>;
 
 	/// The means of purchasing weight credit for XCM execution.
-	type Trader: WeightTrader;
+	type Trader: WeightTrader + Clone;
 
 	/// What to do when a response of a query is found.
 	type ResponseHandler: OnResponse;
@@ -110,4 +110,7 @@ pub trait Config {
 	/// Use this type to explicitly whitelist calls that cannot undergo recursion. This is a
 	/// temporary measure until we properly account for proof size weights for XCM instructions.
 	type SafeCallFilter: Contains<Self::RuntimeCall>;
+
+	/// Transactional processor for XCM instructions.
+	type TransactionalProcessor: ProcessTransaction;
 }