Enable cross-chain Coretime region transfers (#3077)

This PR allows Coretime regions to be transferable via XCM.

---------

Co-authored-by: Dónal Murray <donal.murray@parity.io>

cumulus/parachains/runtimes/coretime/coretime-rococo/src/xcm_config.rs

@@ -15,11 +15,12 @@
 // along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
 
 use super::{
-	AccountId, AllPalletsWithSystem, Balances, BaseDeliveryFee, FeeAssetId, ParachainInfo,
+	AccountId, AllPalletsWithSystem, Balances, BaseDeliveryFee, Broker, FeeAssetId, ParachainInfo,
 	ParachainSystem, PolkadotXcm, Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin,
 	TransactionByteFee, WeightToFee, XcmpQueue,
 };
 use frame_support::{
+	pallet_prelude::PalletInfoAccess,
 	parameter_types,
 	traits::{ConstU32, Contains, Equals, Everything, Nothing},
 };
@@ -42,11 +43,12 @@ use xcm_builder::CurrencyAdapter;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor, IsConcrete, ParentAsSuperuser,
-	ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
-	XcmFeeManagerFromComponents, XcmFeeToAccount,
+	DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor, IsConcrete, NonFungibleAdapter,
+	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
+	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
+	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
+	XcmFeeToAccount,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -56,6 +58,8 @@ parameter_types! {
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
 	pub UniversalLocation: InteriorLocation =
 		[GlobalConsensus(RelayNetwork::get().unwrap()), Parachain(ParachainInfo::parachain_id().into())].into();
+	pub BrokerPalletLocation: Location =
+		PalletInstance(<Broker as PalletInfoAccess>::index() as u8).into();
 	pub const MaxInstructions: u32 = 100;
 	pub const MaxAssetsIntoHolding: u32 = 64;
 	pub const GovernanceLocation: Location = Location::parent();
@@ -90,6 +94,23 @@ pub type CurrencyTransactor = CurrencyAdapter<
 	(),
 >;
 
+/// Means for transacting coretime regions on this chain.
+pub type RegionTransactor = NonFungibleAdapter<
+	// Use this non-fungible implementation:
+	Broker,
+	// This adapter will handle coretime regions from the broker pallet.
+	IsConcrete<BrokerPalletLocation>,
+	// Convert an XCM Location into a local account id:
+	LocationToAccountId,
+	// Our chain's account ID type (we can't get away without mentioning it explicitly):
+	AccountId,
+	// We don't track any teleports.
+	(),
+>;
+
+/// Means for transacting assets on this chain.
+pub type AssetTransactors = (CurrencyTransactor, RegionTransactor);
+
 /// This is the type we use to convert an (incoming) XCM origin into a local `Origin` instance,
 /// ready for dispatching a transaction with XCM's `Transact`. There is an `OriginKind` that can
 /// bias the kind of local `Origin` it will become.
@@ -205,7 +226,7 @@ pub struct XcmConfig;
 impl xcm_executor::Config for XcmConfig {
 	type RuntimeCall = RuntimeCall;
 	type XcmSender = XcmRouter;
-	type AssetTransactor = CurrencyTransactor;
+	type AssetTransactor = AssetTransactors;
 	type OriginConverter = XcmOriginToTransactDispatchOrigin;
 	// Coretime chain does not recognize a reserve location for any asset. Users must teleport ROC
 	// where allowed (e.g. with the Relay Chain).

prdoc/pr_3077.prdoc

@@ -0,0 +1,13 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Enable cross-chain Coretime region transfers on Rococo Coretime chain
+
+doc:
+  - audience: Runtime User
+    description: |
+      This PR allows Coretime regions to be cross-chain transferred from the Rococo Coretime chain.
+
+crates: 
+  - name: pallet-broker
+  - name: coretime-rococo-runtime

substrate/frame/broker/src/nonfungible_impl.rs

@@ -18,7 +18,7 @@
 use super::*;
 use frame_support::{
 	pallet_prelude::{DispatchResult, *},
-	traits::nonfungible::{Inspect, Transfer},
+	traits::nonfungible::{Inspect, Mutate, Transfer},
 };
 use sp_std::vec::Vec;
 
@@ -50,3 +50,7 @@ impl<T: Config> Transfer<T::AccountId> for Pallet<T> {
 		Self::do_transfer((*index).into(), None, dest.clone()).map_err(Into::into)
 	}
 }
+
+// We don't allow any of the mutate operations, so the default implementation is used, which will
+// return `TokenError::Unsupported` in case any of the operations is called.
+impl<T: Config> Mutate<T::AccountId> for Pallet<T> {}

substrate/frame/broker/src/tests.rs

@@ -20,11 +20,11 @@
 use crate::{core_mask::*, mock::*, *};
 use frame_support::{
 	assert_noop, assert_ok,
-	traits::nonfungible::{Inspect as NftInspect, Transfer},
+	traits::nonfungible::{Inspect as NftInspect, Mutate, Transfer},
 	BoundedVec,
 };
 use frame_system::RawOrigin::Root;
-use sp_runtime::traits::Get;
+use sp_runtime::{traits::Get, TokenError};
 use CoreAssignment::*;
 use CoretimeTraceItem::*;
 use Finality::*;
@@ -197,6 +197,26 @@ fn transfer_works() {
 	});
 }
 
+#[test]
+fn mutate_operations_unsupported_for_regions() {
+	TestExt::new().execute_with(|| {
+		let region_id = RegionId { begin: 0, core: 0, mask: CoreMask::complete() };
+		assert_noop!(
+			<Broker as Mutate<_>>::mint_into(&region_id.into(), &2),
+			TokenError::Unsupported
+		);
+		assert_noop!(<Broker as Mutate<_>>::burn(&region_id.into(), None), TokenError::Unsupported);
+		assert_noop!(
+			<Broker as Mutate<_>>::set_attribute(&region_id.into(), &[], &[]),
+			TokenError::Unsupported
+		);
+		assert_noop!(
+			<Broker as Mutate<_>>::set_typed_attribute::<u8, u8>(&region_id.into(), &0, &0),
+			TokenError::Unsupported
+		);
+	});
+}
+
 #[test]
 fn permanent_is_not_reassignable() {
 	TestExt::new().endow(1, 1000).execute_with(|| {