Statemint Reserve Asset Transfer (#552)

* add AssetId type alias in statemint-common

* add FungiblesAdapter to allow for asset transactions via XCM

* use custom Polkadot

* fix FungiblesAdapter usage and add CheckingAccount

* update deps

* remove polkadot overrides

* update deps

* pull NonZeroIssuance struct into common + add FungiblesTransactor to Statemine and Westmint

* remove unnecessary tuple wrapping + adjust asset transactor comments

* accept statemint as reserve in rococo test parachain

* adjust parachain config (add Statemint as reserve)

* add test and docs for AssetsFrom

* cargo fmt

Co-authored-by: Ricardo Rius <ricardo@parity.io>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

polkadot-parachains/rococo/Cargo.toml

@@ -39,6 +39,8 @@ pallet-transaction-payment = { git = "https://github.com/paritytech/substrate",
 pallet-aura = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 pallet-transaction-payment-rpc-runtime-api = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 
+parachains-common = { path = "../parachains-common", default-features = false }
+
 # Cumulus dependencies
 cumulus-pallet-aura-ext = { path = "../../pallets/aura-ext", default-features = false }
 cumulus-pallet-parachain-system = { path = "../../pallets/parachain-system", default-features = false }

polkadot-parachains/rococo/src/lib.rs

@@ -45,7 +45,10 @@ pub use frame_support::{
 	},
 	StorageValue,
 };
-use frame_system::limits::{BlockLength, BlockWeights};
+use frame_system::{
+	limits::{BlockLength, BlockWeights},
+	EnsureOneOf, EnsureRoot,
+};
 pub use pallet_balances::Call as BalancesCall;
 pub use pallet_timestamp::Call as TimestampCall;
 pub use sp_consensus_aura::sr25519::AuthorityId as AuraId;
@@ -53,6 +56,13 @@ pub use sp_consensus_aura::sr25519::AuthorityId as AuraId;
 pub use sp_runtime::BuildStorage;
 pub use sp_runtime::{Perbill, Permill};
 
+use parachains_common::{
+	impls::{AssetsFrom, NonZeroIssuance},
+	AssetId,
+};
+use xcm_builder::{AsPrefixedGeneralIndex, ConvertedConcreteAssetId, FungiblesAdapter};
+use xcm_executor::traits::JustTry;
+
 // XCM imports
 use pallet_xcm::{EnsureXcm, IsMajorityOfBody, XcmPassthrough};
 use polkadot_parachain::primitives::Sibling;
@@ -258,6 +268,7 @@ parameter_types! {
 	pub const RococoNetwork: NetworkId = NetworkId::Polkadot;
 	pub RelayChainOrigin: Origin = cumulus_pallet_xcm::Origin::Relay.into();
 	pub Ancestry: MultiLocation = Parachain(ParachainInfo::parachain_id().into()).into();
+	pub CheckingAccount: AccountId = PolkadotXcm::check_account();
 }
 
 /// Type for specifying how a `MultiLocation` can be converted into an `AccountId`. This is used
@@ -273,7 +284,7 @@ pub type LocationToAccountId = (
 );
 
 /// Means for transacting assets on this chain.
-pub type LocalAssetTransactor = CurrencyAdapter<
+pub type CurrencyTransactor = CurrencyAdapter<
 	// Use this currency:
 	Balances,
 	// Use this currency when it is a fungible asset matching the given location or name:
@@ -286,6 +297,30 @@ pub type LocalAssetTransactor = CurrencyAdapter<
 	(),
 >;
 
+/// Means for transacting assets besides the native currency on this chain.
+pub type FungiblesTransactor = FungiblesAdapter<
+	// Use this fungibles implementation:
+	Assets,
+	// Use this currency when it is a fungible asset matching the given location or name:
+	ConvertedConcreteAssetId<
+		AssetId,
+		u64,
+		AsPrefixedGeneralIndex<StatemintLocation, AssetId, JustTry>,
+		JustTry,
+	>,
+	// Convert an XCM MultiLocation into a local account id:
+	LocationToAccountId,
+	// Our chain's account ID type (we can't get away without mentioning it explicitly):
+	AccountId,
+	// We only want to allow teleports of known assets. We use non-zero issuance as an indication
+	// that this asset is known.
+	NonZeroIssuance<AccountId, Assets>,
+	// The account to use for tracking teleports.
+	CheckingAccount,
+>;
+/// Means for transacting assets on this chain.
+pub type AssetTransactors = (CurrencyTransactor, FungiblesTransactor);
+
 /// 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` which can
 /// biases the kind of local `Origin` it will become.
@@ -324,22 +359,34 @@ match_type! {
 		MultiLocation { parents: 1, interior: X1(Plurality { id: BodyId::Unit, .. }) }
 	};
 }
+match_type! {
+	pub type Statemint: impl Contains<MultiLocation> = {
+		MultiLocation { parents: 1, interior: X1(Parachain(1000)) }
+	};
+}
 
 pub type Barrier = (
 	TakeWeightCredit,
 	AllowTopLevelPaidExecutionFrom<Everything>,
 	AllowUnpaidExecutionFrom<ParentOrParentsUnitPlurality>,
 	// ^^^ Parent & its unit plurality gets free execution
+	AllowUnpaidExecutionFrom<Statemint>,
 );
 
+parameter_types! {
+	pub StatemintLocation: MultiLocation = MultiLocation::new(1, X1(Parachain(1000)));
+}
+
+pub type Reserves = (NativeAsset, AssetsFrom<StatemintLocation>);
+
 pub struct XcmConfig;
 impl Config for XcmConfig {
 	type Call = Call;
 	type XcmSender = XcmRouter;
 	// How to withdraw and deposit an asset.
-	type AssetTransactor = LocalAssetTransactor;
+	type AssetTransactor = AssetTransactors;
 	type OriginConverter = XcmOriginToTransactDispatchOrigin;
-	type IsReserve = NativeAsset;
+	type IsReserve = Reserves;
 	type IsTeleporter = NativeAsset; // <- should be enough to allow teleportation of ROC
 	type LocationInverter = LocationInverter<Ancestry>;
 	type Barrier = Barrier;
@@ -416,12 +463,16 @@ parameter_types! {
 }
 
 /// A majority of the Unit body from Rococo over XCM is our required administration origin.
-pub type AdminOrigin = EnsureXcm<IsMajorityOfBody<RocLocation, UnitBody>>;
+pub type AdminOrigin = EnsureOneOf<
+	AccountId,
+	EnsureRoot<AccountId>,
+	EnsureXcm<IsMajorityOfBody<RocLocation, UnitBody>>,
+>;
 
 impl pallet_assets::Config for Runtime {
 	type Event = Event;
 	type Balance = u64;
-	type AssetId = u32;
+	type AssetId = AssetId;
 	type Currency = Balances;
 	type ForceOrigin = AdminOrigin;
 	type AssetDeposit = AssetDeposit;