xcm-fee-payment-runtime-api 0.4.0

// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Substrate 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.

// Substrate 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/>.

//! Tests for using both the XCM fee payment API and the dry-run API.

use frame_system::RawOrigin;
use sp_api::ProvideRuntimeApi;
use sp_runtime::testing::H256;
use xcm::prelude::*;
use xcm_fee_payment_runtime_api::{dry_run::DryRunApi, fees::XcmPaymentApi};

mod mock;
use mock::{
	fake_message_hash, new_test_ext_with_balances, new_test_ext_with_balances_and_assets,
	DeliveryFees, ExistentialDeposit, HereLocation, OriginCaller, RuntimeCall, RuntimeEvent,
	TestClient,
};

// Scenario: User `1` in the local chain (id 2000) wants to transfer assets to account `[0u8; 32]`
// on "AssetHub". He wants to make sure he has enough for fees, so before he calls the
// `transfer_asset` extrinsic to do the transfer, he decides to use the `XcmDryRunApi` and
// `XcmPaymentApi` runtime APIs to estimate fees. This uses a teleport because we're dealing with
// the native token of the chain, which is registered on "AssetHub". The fees are sent as a reserve
// asset transfer, since they're paid in the relay token.
//
//                 Teleport Parachain(2000) Token
//                 Reserve Asset Transfer Relay Token for fees
// Parachain(2000) -------------------------------------------> Parachain(1000)
#[test]
fn fee_estimation_for_teleport() {
	let _ = env_logger::builder().is_test(true).try_init();
	let who = 1; // AccountId = u64.
	let balances = vec![(who, 100 + DeliveryFees::get() + ExistentialDeposit::get())];
	let assets = vec![(1, who, 50)];
	new_test_ext_with_balances_and_assets(balances, assets).execute_with(|| {
		let client = TestClient;
		let runtime_api = client.runtime_api();
		let call = RuntimeCall::XcmPallet(pallet_xcm::Call::transfer_assets {
			dest: Box::new(VersionedLocation::from((Parent, Parachain(1000)))),
			beneficiary: Box::new(VersionedLocation::from(AccountId32 {
				id: [0u8; 32],
				network: None,
			})),
			assets: Box::new(VersionedAssets::from(vec![
				(Here, 100u128).into(),
				(Parent, 20u128).into(),
			])),
			fee_asset_item: 1, // Fees are paid with the RelayToken
			weight_limit: Unlimited,
		});
		let origin = OriginCaller::system(RawOrigin::Signed(who));
		let dry_run_effects =
			runtime_api.dry_run_call(H256::zero(), origin, call).unwrap().unwrap();

		assert_eq!(
			dry_run_effects.local_xcm,
			Some(VersionedXcm::from(
				Xcm::builder_unsafe()
					.withdraw_asset((Parent, 20u128))
					.burn_asset((Parent, 20u128))
					.withdraw_asset((Here, 100u128))
					.burn_asset((Here, 100u128))
					.build()
			)),
		);
		let send_destination = Location::new(1, [Parachain(1000)]);
		let send_message = Xcm::<()>::builder_unsafe()
			.withdraw_asset((Parent, 20u128))
			.buy_execution((Parent, 20u128), Unlimited)
			.receive_teleported_asset(((Parent, Parachain(2000)), 100u128))
			.clear_origin()
			.deposit_asset(AllCounted(2), [0u8; 32])
			.build();
		assert_eq!(
			dry_run_effects.forwarded_xcms,
			vec![(
				VersionedLocation::from(send_destination.clone()),
				vec![VersionedXcm::from(send_message.clone())],
			),],
		);

		assert_eq!(
			dry_run_effects.emitted_events,
			vec![
				RuntimeEvent::System(frame_system::Event::NewAccount {
					account: 8660274132218572653 // TODO: Why is this not `1`?
				}),
				RuntimeEvent::Balances(pallet_balances::Event::Endowed {
					account: 8660274132218572653,
					free_balance: 100
				}),
				RuntimeEvent::Balances(pallet_balances::Event::Minted {
					who: 8660274132218572653,
					amount: 100
				}),
				RuntimeEvent::AssetsPallet(pallet_assets::Event::Burned {
					asset_id: 1,
					owner: 1,
					balance: 20
				}),
				RuntimeEvent::Balances(pallet_balances::Event::Burned { who: 1, amount: 100 }),
				RuntimeEvent::XcmPallet(pallet_xcm::Event::Attempted {
					outcome: Outcome::Complete { used: Weight::from_parts(400, 40) },
				}),
				RuntimeEvent::Balances(pallet_balances::Event::Burned { who: 1, amount: 20 }),
				RuntimeEvent::XcmPallet(pallet_xcm::Event::FeesPaid {
					paying: AccountIndex64 { index: 1, network: None }.into(),
					fees: (Here, 20u128).into(),
				}),
				RuntimeEvent::XcmPallet(pallet_xcm::Event::Sent {
					origin: AccountIndex64 { index: 1, network: None }.into(),
					destination: (Parent, Parachain(1000)).into(),
					message: send_message.clone(),
					message_id: fake_message_hash(&send_message),
				}),
			]
		);

		// Weighing the local program is not relevant for extrinsics that already
		// take this weight into account.
		// In this case, we really only care about delivery fees.
		let local_xcm = dry_run_effects.local_xcm.unwrap();

		// We get a double result since the actual call returns a result and the runtime api returns
		// results.
		let weight =
			runtime_api.query_xcm_weight(H256::zero(), local_xcm.clone()).unwrap().unwrap();
		assert_eq!(weight, Weight::from_parts(400, 40));
		let execution_fees = runtime_api
			.query_weight_to_asset_fee(
				H256::zero(),
				weight,
				VersionedAssetId::from(AssetId(HereLocation::get())),
			)
			.unwrap()
			.unwrap();
		assert_eq!(execution_fees, 440);

		let mut forwarded_xcms_iter = dry_run_effects.forwarded_xcms.into_iter();

		let (destination, remote_messages) = forwarded_xcms_iter.next().unwrap();
		let remote_message = &remote_messages[0];

		let delivery_fees = runtime_api
			.query_delivery_fees(H256::zero(), destination.clone(), remote_message.clone())
			.unwrap()
			.unwrap();
		assert_eq!(delivery_fees, VersionedAssets::from((Here, 20u128)));

		// This would have to be the runtime API of the destination,
		// which we have the location for.
		// If I had a mock runtime configured for "AssetHub" then I would use the
		// runtime APIs from that.
		let remote_execution_weight = runtime_api
			.query_xcm_weight(H256::zero(), remote_message.clone())
			.unwrap()
			.unwrap();
		let remote_execution_fees = runtime_api
			.query_weight_to_asset_fee(
				H256::zero(),
				remote_execution_weight,
				VersionedAssetId::from(AssetId(HereLocation::get())),
			)
			.unwrap()
			.unwrap();
		assert_eq!(remote_execution_fees, 550);

		// Now we know that locally we need to use `execution_fees` and
		// `delivery_fees`.
		// On the message we forward to the destination, we need to
		// put `remote_execution_fees` in `BuyExecution`.
		// For the `transfer_assets` extrinsic, it just means passing the correct amount
		// of fees in the parameters.
	});
}

// Same scenario as in `fee_estimation_for_teleport`, but the user in parachain 2000 wants
// to send relay tokens over to parachain 1000.
//
//                 Reserve Asset Transfer Relay Token
//                 Reserve Asset Transfer Relay Token for fees
// Parachain(2000) -------------------------------------------> Parachain(1000)
#[test]
fn dry_run_reserve_asset_transfer() {
	let _ = env_logger::builder().is_test(true).try_init();
	let who = 1; // AccountId = u64.
			 // Native token used for fees.
	let balances = vec![(who, DeliveryFees::get() + ExistentialDeposit::get())];
	// Relay token is the one we want to transfer.
	let assets = vec![(1, who, 100)]; // id, account_id, balance.
	new_test_ext_with_balances_and_assets(balances, assets).execute_with(|| {
		let client = TestClient;
		let runtime_api = client.runtime_api();
		let call = RuntimeCall::XcmPallet(pallet_xcm::Call::transfer_assets {
			dest: Box::new(VersionedLocation::from((Parent, Parachain(1000)))),
			beneficiary: Box::new(VersionedLocation::from(AccountId32 {
				id: [0u8; 32],
				network: None,
			})),
			assets: Box::new(VersionedAssets::from((Parent, 100u128))),
			fee_asset_item: 0,
			weight_limit: Unlimited,
		});
		let origin = OriginCaller::system(RawOrigin::Signed(who));
		let dry_run_effects =
			runtime_api.dry_run_call(H256::zero(), origin, call).unwrap().unwrap();

		assert_eq!(
			dry_run_effects.local_xcm,
			Some(VersionedXcm::from(
				Xcm::builder_unsafe()
					.withdraw_asset((Parent, 100u128))
					.burn_asset((Parent, 100u128))
					.build()
			)),
		);

		// In this case, the transfer type is `DestinationReserve`, so the remote xcm just withdraws
		// the assets.
		let send_destination = Location::new(1, Parachain(1000));
		let send_message = Xcm::<()>::builder_unsafe()
			.withdraw_asset((Parent, 100u128))
			.clear_origin()
			.buy_execution((Parent, 100u128), Unlimited)
			.deposit_asset(AllCounted(1), [0u8; 32])
			.build();
		assert_eq!(
			dry_run_effects.forwarded_xcms,
			vec![(
				VersionedLocation::from(send_destination.clone()),
				vec![VersionedXcm::from(send_message.clone())],
			),],
		);

		assert_eq!(
			dry_run_effects.emitted_events,
			vec![
				RuntimeEvent::AssetsPallet(pallet_assets::Event::Burned {
					asset_id: 1,
					owner: 1,
					balance: 100
				}),
				RuntimeEvent::XcmPallet(pallet_xcm::Event::Attempted {
					outcome: Outcome::Complete { used: Weight::from_parts(200, 20) }
				}),
				RuntimeEvent::Balances(pallet_balances::Event::Burned { who: 1, amount: 20 }),
				RuntimeEvent::XcmPallet(pallet_xcm::Event::FeesPaid {
					paying: AccountIndex64 { index: 1, network: None }.into(),
					fees: (Here, 20u128).into()
				}),
				RuntimeEvent::XcmPallet(pallet_xcm::Event::Sent {
					origin: AccountIndex64 { index: 1, network: None }.into(),
					destination: send_destination.clone(),
					message: send_message.clone(),
					message_id: fake_message_hash(&send_message),
				}),
			]
		);
	});
}

#[test]
fn dry_run_xcm() {
	let _ = env_logger::builder().is_test(true).try_init();
	let who = 1; // AccountId = u64.
	let transfer_amount = 100u128;
	// We need to build the XCM to weigh it and then build the real XCM that can pay for fees.
	let inner_xcm = Xcm::<()>::builder_unsafe()
		.buy_execution((Here, 1u128), Unlimited) // We'd need to query the destination chain for fees.
		.deposit_asset(AllCounted(1), [0u8; 32])
		.build();
	let xcm_to_weigh = Xcm::<RuntimeCall>::builder_unsafe()
		.withdraw_asset((Here, transfer_amount))
		.clear_origin()
		.buy_execution((Here, transfer_amount), Unlimited)
		.deposit_reserve_asset(AllCounted(1), (Parent, Parachain(2100)), inner_xcm.clone())
		.build();
	let client = TestClient;
	let runtime_api = client.runtime_api();
	let xcm_weight = runtime_api
		.query_xcm_weight(H256::zero(), VersionedXcm::from(xcm_to_weigh.clone().into()))
		.unwrap()
		.unwrap();
	let execution_fees = runtime_api
		.query_weight_to_asset_fee(
			H256::zero(),
			xcm_weight,
			VersionedAssetId::from(AssetId(Here.into())),
		)
		.unwrap()
		.unwrap();
	let xcm = Xcm::<RuntimeCall>::builder_unsafe()
		.withdraw_asset((Here, transfer_amount + execution_fees))
		.clear_origin()
		.buy_execution((Here, execution_fees), Unlimited)
		.deposit_reserve_asset(AllCounted(1), (Parent, Parachain(2100)), inner_xcm.clone())
		.build();
	let balances = vec![(
		who,
		transfer_amount + execution_fees + DeliveryFees::get() + ExistentialDeposit::get(),
	)];
	new_test_ext_with_balances(balances).execute_with(|| {
		let dry_run_effects = runtime_api
			.dry_run_xcm(
				H256::zero(),
				VersionedLocation::from([AccountIndex64 { index: 1, network: None }]),
				VersionedXcm::from(xcm),
			)
			.unwrap()
			.unwrap();
		assert_eq!(
			dry_run_effects.forwarded_xcms,
			vec![(
				VersionedLocation::from((Parent, Parachain(2100))),
				vec![VersionedXcm::from(
					Xcm::<()>::builder_unsafe()
						.reserve_asset_deposited((
							(Parent, Parachain(2000)),
							transfer_amount + execution_fees - DeliveryFees::get()
						))
						.clear_origin()
						.buy_execution((Here, 1u128), Unlimited)
						.deposit_asset(AllCounted(1), [0u8; 32])
						.build()
				)],
			),]
		);

		assert_eq!(
			dry_run_effects.emitted_events,
			vec![
				RuntimeEvent::Balances(pallet_balances::Event::Burned { who: 1, amount: 540 }),
				RuntimeEvent::System(frame_system::Event::NewAccount { account: 2100 }),
				RuntimeEvent::Balances(pallet_balances::Event::Endowed {
					account: 2100,
					free_balance: 520
				}),
				RuntimeEvent::Balances(pallet_balances::Event::Minted { who: 2100, amount: 520 }),
			]
		);
	});
}