CallDispatcher trait

runtime/kusama/src/xcm_config.rs

@@ -35,6 +35,7 @@ use xcm_builder::{
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 	UsingComponents, WeightInfoBounds,
 };
+use xcm_executor::traits::JustDispatch;
 
 parameter_types! {
 	/// The location of the KSM token, from the context of this chain. Since this token is native to this
@@ -161,6 +162,7 @@ impl xcm_executor::Config for XcmConfig {
 	// No bridges yet...
 	type MessageExporter = ();
 	type UniversalAliases = Nothing;
+	type CallDispatcher = JustDispatch;
 }
 
 parameter_types! {

runtime/polkadot/src/xcm_config.rs

@@ -34,6 +34,7 @@ use xcm_builder::{
 	IsConcrete, SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation,
 	TakeWeightCredit, UsingComponents,
 };
+use xcm_executor::traits::JustDispatch;
 
 parameter_types! {
 	/// The location of the DOT token, from the context of this chain. Since this token is native to this
@@ -158,6 +159,7 @@ impl xcm_executor::Config for XcmConfig {
 	// No bridges yet...
 	type MessageExporter = ();
 	type UniversalAliases = Nothing;
+	type CallDispatcher = JustDispatch;
 }
 
 parameter_types! {

runtime/rococo/src/xcm_config.rs

@@ -34,7 +34,7 @@ use xcm_builder::{
 	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, IsConcrete,
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, UsingComponents,
 };
-use xcm_executor::XcmExecutor;
+use xcm_executor::{traits::JustDispatch, XcmExecutor};
 
 parameter_types! {
 	pub const TokenLocation: MultiLocation = Here.into_location();
@@ -144,6 +144,7 @@ impl xcm_executor::Config for XcmConfig {
 	type FeeManager = ();
 	type MessageExporter = ();
 	type UniversalAliases = Nothing;
+	type CallDispatcher = JustDispatch;
 }
 
 parameter_types! {

runtime/westend/src/xcm_config.rs

@@ -34,7 +34,7 @@ use xcm_builder::{
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 	UsingComponents, WeightInfoBounds,
 };
-use xcm_executor::XcmExecutor;
+use xcm_executor::{traits::JustDispatch, XcmExecutor};
 
 parameter_types! {
 	pub const TokenLocation: MultiLocation = Here.into_location();
@@ -123,6 +123,7 @@ impl xcm_executor::Config for XcmConfig {
 	type FeeManager = ();
 	type MessageExporter = ();
 	type UniversalAliases = Nothing;
+	type CallDispatcher = JustDispatch;
 }
 
 /// Type to convert an `Origin` type value into a `MultiLocation` value which represents an interior location

xcm/xcm-executor/src/config.rs

@@ -15,7 +15,7 @@
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
 use crate::traits::{
-	AssetExchange, AssetLock, ClaimAssets, ConvertOrigin, DropAssets, ExportXcm, FeeManager,
+	CallDispatcher, AssetExchange, AssetLock, ClaimAssets, ConvertOrigin, DropAssets, ExportXcm, FeeManager,
 	OnResponse, ShouldExecute, TransactAsset, VersionChangeNotifier, WeightBounds, WeightTrader,
 };
 use frame_support::{
@@ -94,4 +94,9 @@ pub trait Config {
 	/// The origin locations and specific universal junctions to which they are allowed to elevate
 	/// themselves.
 	type UniversalAliases: Contains<(MultiLocation, Junction)>;
+
+	/// How calls are dispatched from XCM.
+	/// Allows to modify the origin and/or the call based on the other.
+	/// To simply do `call.dispatch(origin)`, use `JustDispatch`.
+	type CallDispatcher: CallDispatcher<Self::Call>;
 }

xcm/xcm-executor/src/lib.rs

@@ -30,7 +30,7 @@ use xcm::latest::prelude::*;
 
 pub mod traits;
 use traits::{
-	validate_export, AssetExchange, AssetLock, ClaimAssets, ConvertOrigin, DropAssets, Enact,
+	CallDispatcher, validate_export, AssetExchange, AssetLock, ClaimAssets, ConvertOrigin, DropAssets, Enact,
 	ExportXcm, FeeManager, FeeReason, OnResponse, ShouldExecute, TransactAsset,
 	VersionChangeNotifier, WeightBounds, WeightTrader,
 };
@@ -512,7 +512,7 @@ impl<Config: config::Config> XcmExecutor<Config> {
 					.map_err(|_| XcmError::BadOrigin)?;
 				let weight = message_call.get_dispatch_info().weight;
 				ensure!(weight <= require_weight_at_most, XcmError::MaxWeightInvalid);
-				let maybe_actual_weight = match message_call.dispatch(dispatch_origin) {
+				let maybe_actual_weight = match Config::CallDispatcher::dispatch(message_call, dispatch_origin) {
 					Ok(post_info) => {
 						self.transact_status = MaybeErrorCode::Success;
 						post_info.actual_weight

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

@@ -15,6 +15,7 @@
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
 use parity_scale_codec::{Decode, Encode};
+use sp_runtime::{traits::Dispatchable, DispatchErrorWithPostInfo};
 use sp_std::{borrow::Borrow, prelude::*, result::Result};
 use xcm::latest::prelude::*;
 
@@ -203,3 +204,24 @@ impl<O> ConvertOrigin<O> for Tuple {
 		Err(origin)
 	}
 }
+
+/// Defines how a call is dispatched with given origin.
+/// Allows to customize call dispatch, such as adapting the origin based on the call
+/// or modifying the call.
+pub trait CallDispatcher<Call: Dispatchable> {
+	fn dispatch(
+		call: Call,
+		origin: Call::Origin,
+	) -> Result<Call::PostInfo, DispatchErrorWithPostInfo<Call::PostInfo>>;
+}
+
+/// Just call `call.dispatch(origin)`.
+pub struct JustDispatch;
+impl<Call: Dispatchable> CallDispatcher<Call> for JustDispatch {
+	fn dispatch(
+		call: Call,
+		origin: Call::Origin,
+	) -> Result<Call::PostInfo, DispatchErrorWithPostInfo<Call::PostInfo>> {
+		call.dispatch(origin)
+	}
+}

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

@@ -17,7 +17,7 @@
 //! Various traits used in configuring the executor.
 
 mod conversion;
-pub use conversion::{Convert, ConvertOrigin, Decoded, Encoded, Identity, JustTry};
+pub use conversion::{CallDispatcher, JustDispatch, Convert, ConvertOrigin, Decoded, Encoded, Identity, JustTry};
 mod drop_assets;
 pub use drop_assets::{ClaimAssets, DropAssets};
 mod asset_lock;