Introduce transactional processing for xcm instructions

runtime/kusama/src/xcm_config.rs

@@ -33,10 +33,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, IsChildSystemParachain, IsConcrete,
-	MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, UsingComponents, WeightInfoBounds,
-	WithComputedOrigin,
+	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, FrameTransactionalProcessor,
+	IsChildSystemParachain, IsConcrete, MintLocation, OriginToPluralityVoice,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -331,6 +331,7 @@ impl xcm_executor::Config for XcmConfig {
 	type UniversalAliases = Nothing;
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 parameter_types! {

runtime/polkadot/src/xcm_config.rs

@@ -36,9 +36,9 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, BackingToPlurality,
 	ChildParachainAsNative, ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter,
-	FixedWeightBounds, IsConcrete, MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, UsingComponents,
-	WithComputedOrigin,
+	FixedWeightBounds, FrameTransactionalProcessor, IsConcrete, MintLocation,
+	OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, UsingComponents, WithComputedOrigin,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -350,6 +350,7 @@ impl xcm_executor::Config for XcmConfig {
 	type UniversalAliases = Nothing;
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 parameter_types! {

runtime/rococo/src/xcm_config.rs

@@ -33,9 +33,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, BackingToPlurality,
 	ChildParachainAsNative, ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, IsChildSystemParachain, IsConcrete,
-	MintLocation, SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation,
-	TakeWeightCredit, UsingComponents, WeightInfoBounds, WithComputedOrigin,
+	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, FrameTransactionalProcessor,
+	IsChildSystemParachain, IsConcrete, MintLocation, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, UsingComponents,
+	WeightInfoBounds, WithComputedOrigin,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -308,6 +309,7 @@ impl xcm_executor::Config for XcmConfig {
 	type UniversalAliases = Nothing;
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 parameter_types! {

runtime/westend/src/xcm_config.rs

@@ -32,9 +32,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain, IsConcrete, MintLocation,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin,
+	CurrencyAdapter as XcmCurrencyAdapter, FrameTransactionalProcessor, IsChildSystemParachain,
+	IsConcrete, MintLocation, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, UsingComponents, WeightInfoBounds,
+	WithComputedOrigin,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -245,6 +246,7 @@ impl xcm_executor::Config for XcmConfig {
 	type UniversalAliases = Nothing;
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;
+	type TransactionalProcessor = FrameTransactionalProcessor;
 }
 
 /// Type to convert an `Origin` type value into a `MultiLocation` value which represents an interior location

xcm/xcm-builder/src/lib.rs

@@ -85,3 +85,6 @@ pub use universal_exports::{
 	HaulBlobError, HaulBlobExporter, NetworkExportTable, SovereignPaidRemoteExporter,
 	UnpaidLocalExporter, UnpaidRemoteExporter,
 };
+
+mod transactional;
+pub use transactional::FrameTransactionalProcessor;

xcm/xcm-builder/src/transactional.rs

@@ -0,0 +1,44 @@
+// 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::{
+	pallet_prelude::DispatchError,
+	storage::{with_transaction, TransactionOutcome},
+};
+use xcm::latest::prelude::*;
+use xcm_executor::traits::ProcessTransaction;
+
+pub struct FrameTransactionalProcessor;
+impl ProcessTransaction for FrameTransactionalProcessor {
+	fn process_transaction<F>(f: F) -> Result<(), XcmError>
+	where
+		F: FnOnce() -> Result<(), XcmError>,
+	{
+		let transaction_outcome =
+			with_transaction(|| -> TransactionOutcome<Result<_, DispatchError>> {
+				let outcome = f();
+				match &outcome {
+					Ok(_) => TransactionOutcome::Commit(Ok(None)),
+					Err(err) => TransactionOutcome::Rollback(Ok(Some(*err))),
+				}
+			});
+		match transaction_outcome {
+			Ok(None) => Ok(()),
+			Ok(Some(err)) => Err(err),
+			Err(err) => Err(XcmError::FailedToTransactAsset(err.into())),
+		}
+	}
+}

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},
@@ -106,4 +106,6 @@ 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>;
+
+	type TransactionalProcessor: ProcessTransaction;
 }

xcm/xcm-executor/src/lib.rs

@@ -31,8 +31,8 @@ use xcm::latest::prelude::*;
 pub mod traits;
 use traits::{
 	validate_export, AssetExchange, AssetLock, CallDispatcher, ClaimAssets, ConvertOrigin,
-	DropAssets, Enact, ExportXcm, FeeManager, FeeReason, OnResponse, ShouldExecute, TransactAsset,
-	VersionChangeNotifier, WeightBounds, WeightTrader,
+	DropAssets, Enact, ExportXcm, FeeManager, FeeReason, OnResponse, ProcessTransaction,
+	ShouldExecute, TransactAsset, VersionChangeNotifier, WeightBounds, WeightTrader,
 };
 
 mod assets;
@@ -473,13 +473,19 @@ impl<Config: config::Config> XcmExecutor<Config> {
 		);
 		match instr {
 			WithdrawAsset(assets) => {
-				// Take `assets` from the origin account (on-chain) and place in holding.
-				let origin = *self.origin_ref().ok_or(XcmError::BadOrigin)?;
-				for asset in assets.into_inner().into_iter() {
-					Config::AssetTransactor::withdraw_asset(&asset, &origin, Some(&self.context))?;
-					self.subsume_asset(asset)?;
-				}
-				Ok(())
+				Config::TransactionalProcessor::process_transaction(|| -> Result<(), XcmError> {
+					// Take `assets` from the origin account (on-chain) and place in holding.
+					let origin = *self.origin_ref().ok_or(XcmError::BadOrigin)?;
+					for asset in assets.into_inner().into_iter() {
+						Config::AssetTransactor::withdraw_asset(
+							&asset,
+							&origin,
+							Some(&self.context),
+						)?;
+						self.subsume_asset(asset)?;
+					}
+					Ok(())
+				})
 			},
 			ReserveAssetDeposited(assets) => {
 				// check whether we trust origin to be our reserve location for this asset.

xcm/xcm-executor/src/traits/mod.rs

@@ -39,6 +39,8 @@ pub use token_matching::{
 };
 mod on_response;
 pub use on_response::{OnResponse, VersionChangeNotifier};
+mod process_transaction;
+pub use process_transaction::ProcessTransaction;
 mod should_execute;
 pub use should_execute::ShouldExecute;
 mod transact_asset;
@@ -51,7 +53,7 @@ pub mod prelude {
 		export_xcm, validate_export, AssetExchange, AssetLock, ClaimAssets, Convert, ConvertOrigin,
 		Decoded, DropAssets, Enact, Encoded, Error, ExportXcm, FeeManager, FeeReason, Identity,
 		JustTry, LockError, MatchesFungible, MatchesFungibles, MatchesNonFungible,
-		MatchesNonFungibles, OnResponse, ShouldExecute, TransactAsset, VersionChangeNotifier,
-		WeightBounds, WeightTrader, WithOriginFilter,
+		MatchesNonFungibles, OnResponse, ProcessTransaction, ShouldExecute, TransactAsset,
+		VersionChangeNotifier, WeightBounds, WeightTrader, WithOriginFilter,
 	};
 }

xcm/xcm-executor/src/traits/process_transaction.rs

@@ -0,0 +1,23 @@
+// 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/>.
+
+use xcm::latest::prelude::*;
+
+pub trait ProcessTransaction {
+	fn process_transaction<F>(f: F) -> Result<(), XcmError>
+	where
+		F: FnOnce() -> Result<(), XcmError>;
+}