XCM: Land XCM Builder (#1793)

* Land XCM Builder

* Clean up Cargo dependencies

Co-authored-by: Gavin Wood <gavin@parity.io>

polkadot/Cargo.toml

@@ -41,6 +41,7 @@ members = [
 	"service",
 	"validation",
 	"xcm",
+	"xcm/xcm-builder",
 	"xcm/xcm-executor",
 	"node/collation-generation",
 	"node/core/av-store",

polkadot/parachain/src/primitives.rs

@@ -124,9 +124,21 @@ impl Id {
 	}
 
 	/// Returns `true` if this parachain runs with system-level privileges.
+	/// Use IsSystem instead.
+	#[deprecated]
 	pub fn is_system(&self) -> bool { self.0 < USER_INDEX_START }
 }
 
+pub trait IsSystem {
+	fn is_system(&self) -> bool;
+}
+
+impl IsSystem for Id {
+	fn is_system(&self) -> bool {
+		self.0 < USER_INDEX_START
+	}
+}
+
 impl sp_std::ops::Add<u32> for Id {
 	type Output = Self;
 

polkadot/xcm/Cargo.toml

@@ -7,3 +7,10 @@ edition = "2018"
 
 [dependencies]
 codec = { package = "parity-scale-codec", version = "1.3.5", default-features = false, features = [ "derive" ] }
+
+[features]
+default = ["std"]
+wasm-api = []
+std = [
+	"codec/std",
+]

polkadot/xcm/xcm-builder/Cargo.toml

@@ -0,0 +1,33 @@
+[package]
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+name = "xcm-builder"
+description = "Tools & types for building with XCM and its executor."
+version = "0.8.22"
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
+xcm = { path = "..", default-features = false }
+xcm-executor = { path = "../xcm-executor", default-features = false }
+sp-std = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-arithmetic = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-io = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-runtime = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+frame-support = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+
+# Polkadot dependencies
+polkadot-parachain = { path = "../../parachain", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"xcm/std",
+	"xcm-executor/std",
+	"sp-std/std",
+	"sp-arithmetic/std",
+	"sp-io/std",
+	"sp-runtime/std",
+	"frame-support/std",
+	"polkadot-parachain/std",
+]

polkadot/xcm/xcm-builder/src/currency_adapter.rs

@@ -0,0 +1,54 @@
+// 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 sp_std::{result, convert::TryInto, marker::PhantomData};
+use xcm::v0::{Error, Result, MultiAsset, MultiLocation};
+use sp_arithmetic::traits::SaturatedConversion;
+use frame_support::traits::{ExistenceRequirement::AllowDeath, WithdrawReason};
+use xcm_executor::traits::{MatchesFungible, LocationConversion, TransactAsset};
+
+pub struct CurrencyAdapter<Currency, Matcher, AccountIdConverter, AccountId>(
+	PhantomData<Currency>,
+	PhantomData<Matcher>,
+	PhantomData<AccountIdConverter>,
+	PhantomData<AccountId>,
+);
+
+impl<
+	Matcher: MatchesFungible<Currency::Balance>,
+	AccountIdConverter: LocationConversion<AccountId>,
+	Currency: frame_support::traits::Currency<AccountId>,
+	AccountId,	// can't get away without it since Currency is generic over it.
+> TransactAsset for CurrencyAdapter<Currency, Matcher, AccountIdConverter, AccountId> {
+
+	fn deposit_asset(what: &MultiAsset, who: &MultiLocation) -> Result {
+		// Check we handle this asset.
+		let amount = Matcher::matches_fungible(&what).ok_or(())?.saturated_into();
+		let who = AccountIdConverter::from_location(who).ok_or(())?;
+		let balance_amount = amount.try_into().map_err(|_| ())?;
+		let _imbalance = Currency::deposit_creating(&who, balance_amount);
+		Ok(())
+	}
+
+	fn withdraw_asset(what: &MultiAsset, who: &MultiLocation) -> result::Result<MultiAsset, Error> {
+		// Check we handle this asset.
+		let amount = Matcher::matches_fungible(&what).ok_or(())?.saturated_into();
+		let who = AccountIdConverter::from_location(who).ok_or(())?;
+		let balance_amount = amount.try_into().map_err(|_| ())?;
+		Currency::withdraw(&who, balance_amount, WithdrawReason::Transfer.into(), AllowDeath).map_err(|_| ())?;
+		Ok(what.clone())
+	}
+}

polkadot/xcm/xcm-builder/src/lib.rs

@@ -0,0 +1,56 @@
+// 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/>.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+mod location_conversion;
+pub use location_conversion::{
+	Account32Hash, ParentIsDefault, ChildParachainConvertsVia, SiblingParachainConvertsVia, AccountId32Aliases
+};
+
+mod origin_conversion;
+pub use origin_conversion::{
+	SovereignSignedViaLocation, ParentAsSuperuser, ChildSystemParachainAsSuperuser, SiblingSystemParachainAsSuperuser,
+	ChildParachainAsNative, SiblingParachainAsNative, RelayChainAsNative, SignedAccountId32AsNative
+};
+
+mod currency_adapter;
+pub use currency_adapter::CurrencyAdapter;
+
+use sp_std::marker::PhantomData;
+use xcm_executor::traits::InvertLocation;
+use xcm::v0::{MultiLocation, Junction};
+use frame_support::traits::Get;
+
+/// Simple location inverter; give it this location's ancestry and it'll
+pub struct LocationInverter<Ancestry>(PhantomData<Ancestry>);
+
+impl<Ancestry: Get<MultiLocation>> InvertLocation for LocationInverter<Ancestry> {
+	fn invert_location(location: &MultiLocation) -> MultiLocation {
+		let mut ancestry = Ancestry::get();
+		let mut result = location.clone();
+		for (i, j) in location.iter_rev()
+			.map(|j| match j {
+				Junction::Parent => ancestry.take_first().unwrap_or(Junction::OnlyChild),
+				_ => Junction::Parent,
+			})
+			.enumerate()
+		{
+			*result.at_mut(i).expect("location and result begin equal; same size; qed") = j;
+		}
+		result
+	}
+}

polkadot/xcm/xcm-builder/src/location_conversion.rs

@@ -0,0 +1,126 @@
+// 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 sp_std::marker::PhantomData;
+use sp_io::hashing::blake2_256;
+use sp_runtime::traits::AccountIdConversion;
+use frame_support::traits::Get;
+use codec::Encode;
+use xcm::v0::{MultiLocation, NetworkId, Junction};
+use xcm_executor::traits::LocationConversion;
+
+pub struct Account32Hash<Network, AccountId>(PhantomData<(Network, AccountId)>);
+
+impl<
+	Network: Get<NetworkId>,
+	AccountId: From<[u8; 32]> + Into<[u8; 32]>,
+> LocationConversion<AccountId> for Account32Hash<Network, AccountId> {
+	fn from_location(location: &MultiLocation) -> Option<AccountId> {
+		Some(("multiloc", location).using_encoded(blake2_256).into())
+	}
+
+	fn try_into_location(who: AccountId) -> Result<MultiLocation, AccountId> {
+		Err(who)
+	}
+}
+
+pub struct ParentIsDefault<AccountId>(PhantomData<AccountId>);
+
+impl<
+	AccountId: Default + Eq,
+> LocationConversion<AccountId> for ParentIsDefault<AccountId> {
+	fn from_location(location: &MultiLocation) -> Option<AccountId> {
+		if let MultiLocation::X1(Junction::Parent) = location {
+			Some(AccountId::default())
+		} else {
+			None
+		}
+	}
+
+	fn try_into_location(who: AccountId) -> Result<MultiLocation, AccountId> {
+		if who == AccountId::default() {
+			Ok(Junction::Parent.into())
+		} else {
+			Err(who)
+		}
+	}
+}
+
+pub struct ChildParachainConvertsVia<ParaId, AccountId>(PhantomData<(ParaId, AccountId)>);
+
+impl<
+	ParaId: From<u32> + Into<u32> + AccountIdConversion<AccountId>,
+	AccountId,
+> LocationConversion<AccountId> for ChildParachainConvertsVia<ParaId, AccountId> {
+	fn from_location(location: &MultiLocation) -> Option<AccountId> {
+		if let MultiLocation::X1(Junction::Parachain { id }) = location {
+			Some(ParaId::from(*id).into_account())
+		} else {
+			None
+		}
+	}
+
+	fn try_into_location(who: AccountId) -> Result<MultiLocation, AccountId> {
+		if let Some(id) = ParaId::try_from_account(&who) {
+			Ok(Junction::Parachain { id: id.into() }.into())
+		} else {
+			Err(who)
+		}
+	}
+}
+
+pub struct SiblingParachainConvertsVia<ParaId, AccountId>(PhantomData<(ParaId, AccountId)>);
+
+impl<
+	ParaId: From<u32> + Into<u32> + AccountIdConversion<AccountId>,
+	AccountId,
+> LocationConversion<AccountId> for SiblingParachainConvertsVia<ParaId, AccountId> {
+	fn from_location(location: &MultiLocation) -> Option<AccountId> {
+		if let MultiLocation::X2(Junction::Parent, Junction::Parachain { id }) = location {
+			Some(ParaId::from(*id).into_account())
+		} else {
+			None
+		}
+	}
+
+	fn try_into_location(who: AccountId) -> Result<MultiLocation, AccountId> {
+		if let Some(id) = ParaId::try_from_account(&who) {
+			Ok([Junction::Parent, Junction::Parachain { id: id.into() }].into())
+		} else {
+			Err(who)
+		}
+	}
+}
+
+pub struct AccountId32Aliases<Network, AccountId>(PhantomData<(Network, AccountId)>);
+
+impl<
+	Network: Get<NetworkId>,
+	AccountId: From<[u8; 32]> + Into<[u8; 32]>,
+> LocationConversion<AccountId> for AccountId32Aliases<Network, AccountId> {
+	fn from_location(location: &MultiLocation) -> Option<AccountId> {
+		if let MultiLocation::X1(Junction::AccountId32 { id, network }) = location {
+			if matches!(network, NetworkId::Any) || network == &Network::get() {
+				return Some((*id).into())
+			}
+		}
+		None
+	}
+
+	fn try_into_location(who: AccountId) -> Result<MultiLocation, AccountId> {
+		Ok(Junction::AccountId32 { id: who.into(), network: Network::get() }.into())
+	}
+}

polkadot/xcm/xcm-builder/src/origin_conversion.rs

@@ -0,0 +1,150 @@
+// 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 sp_std::marker::PhantomData;
+use frame_support::traits::{Get, OriginTrait};
+use xcm::v0::{MultiLocation, OriginKind, NetworkId, Junction};
+use xcm_executor::traits::{LocationConversion, ConvertOrigin};
+use polkadot_parachain::primitives::IsSystem;
+
+/// Sovereign accounts use the system's `Signed` origin with an account ID derived from the
+/// `LocationConverter`.
+pub struct SovereignSignedViaLocation<LocationConverter, Origin>(
+	PhantomData<(LocationConverter, Origin)>
+);
+impl<
+	LocationConverter: LocationConversion<Origin::AccountId>,
+	Origin: OriginTrait,
+> ConvertOrigin<Origin> for SovereignSignedViaLocation<LocationConverter, Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		if let OriginKind::SovereignAccount = kind {
+			let location = LocationConverter::from_location(&origin).ok_or(origin)?;
+			Ok(Origin::signed(location).into())
+		} else {
+			Err(origin)
+		}
+	}
+}
+
+pub struct ParentAsSuperuser<Origin>(PhantomData<Origin>);
+impl<
+	Origin: OriginTrait,
+> ConvertOrigin<Origin> for ParentAsSuperuser<Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Superuser, MultiLocation::X1(Junction::Parent)) =>
+				Ok(Origin::root()),
+			(_, origin) => Err(origin),
+		}
+	}
+}
+
+pub struct ChildSystemParachainAsSuperuser<ParaId, Origin>(PhantomData<(ParaId, Origin)>);
+impl<
+	ParaId: IsSystem + From<u32>,
+	Origin: OriginTrait,
+> ConvertOrigin<Origin> for ChildSystemParachainAsSuperuser<ParaId, Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Superuser, MultiLocation::X1(Junction::Parachain { id }))
+			if ParaId::from(id).is_system() =>
+				Ok(Origin::root()),
+			(_, origin) => Err(origin),
+		}
+	}
+}
+
+pub struct SiblingSystemParachainAsSuperuser<ParaId, Origin>(PhantomData<(ParaId, Origin)>);
+impl<
+	ParaId: IsSystem + From<u32>,
+	Origin: OriginTrait
+> ConvertOrigin<Origin> for SiblingSystemParachainAsSuperuser<ParaId, Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Superuser, MultiLocation::X2(Junction::Parent, Junction::Parachain { id }))
+			if ParaId::from(id).is_system() =>
+				Ok(Origin::root()),
+			(_, origin) => Err(origin),
+		}
+	}
+}
+
+pub struct ChildParachainAsNative<ParachainOrigin, Origin>(
+	PhantomData<(ParachainOrigin, Origin)>
+);
+impl<
+	ParachainOrigin: From<u32>,
+	Origin: From<ParachainOrigin>,
+> ConvertOrigin<Origin> for ChildParachainAsNative<ParachainOrigin, Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Native, MultiLocation::X1(Junction::Parachain { id }))
+			=> Ok(Origin::from(ParachainOrigin::from(id))),
+			(_, origin) => Err(origin),
+		}
+	}
+}
+
+pub struct SiblingParachainAsNative<ParachainOrigin, Origin>(
+	PhantomData<(ParachainOrigin, Origin)>
+);
+impl<
+	ParachainOrigin: From<u32>,
+	Origin: From<ParachainOrigin>,
+> ConvertOrigin<Origin> for SiblingParachainAsNative<ParachainOrigin, Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Native, MultiLocation::X2(Junction::Parent, Junction::Parachain { id }))
+			=> Ok(Origin::from(ParachainOrigin::from(id))),
+			(_, origin) => Err(origin),
+		}
+	}
+}
+
+// Our Relay-chain has a native origin given by the `Get`ter.
+pub struct RelayChainAsNative<RelayOrigin, Origin>(
+	PhantomData<(RelayOrigin, Origin)>
+);
+impl<
+	RelayOrigin: Get<Origin>,
+	Origin,
+> ConvertOrigin<Origin> for RelayChainAsNative<RelayOrigin, Origin> {
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Native, MultiLocation::X1(Junction::Parent)) => Ok(RelayOrigin::get()),
+			(_, origin) => Err(origin),
+		}
+	}
+}
+
+pub struct SignedAccountId32AsNative<Network, Origin>(
+	PhantomData<(Network, Origin)>
+);
+impl<
+	Network: Get<NetworkId>,
+	Origin: OriginTrait,
+> ConvertOrigin<Origin> for SignedAccountId32AsNative<Network, Origin> where
+	Origin::AccountId: From<[u8; 32]>,
+{
+	fn convert_origin(origin: MultiLocation, kind: OriginKind) -> Result<Origin, MultiLocation> {
+		match (kind, origin) {
+			(OriginKind::Native, MultiLocation::X1(Junction::AccountId32 { id, network }))
+			if matches!(network, NetworkId::Any) || network == Network::get()
+			=> Ok(Origin::signed(id.into())),
+			(_, origin) => Err(origin),
+		}
+	}
+}