pallet-xcm: enhance reserve_transfer_assets to support remote reser…

…ves (paritytech#1672)

## Motivation

`pallet-xcm` is the main user-facing interface for XCM functionality,
including assets manipulation functions like `teleportAssets()` and
`reserve_transfer_assets()` calls.

While `teleportAsset()` works both ways, `reserve_transfer_assets()`
works only for sending reserve-based assets to a remote destination and
beneficiary when the reserve is the _local chain_.

## Solution

This PR enhances `pallet_xcm::(limited_)reserve_withdraw_assets` to
support transfers when reserves are other chains.
This will allow complete, **bi-directional** reserve-based asset
transfers user stories using `pallet-xcm`.

Enables following scenarios:
- transferring assets with local reserve (was previously supported iff
asset used as fee also had local reserve - now it works in all cases),
- transferring assets with reserve on destination,
- transferring assets with reserve on remote/third-party chain (iff
assets and fees have same remote reserve),
- transferring assets with reserve different than the reserve of the
asset to be used as fees - meaning can be used to transfer random asset
with local/dest reserve while using DOT for fees on all involved chains,
even if DOT local/dest reserve doesn't match asset reserve,
- transferring assets with any type of local/dest reserve while using
fees which can be teleported between involved chains.

All of the above is done by pallet inner logic without the user having
to specify which scenario/reserves/teleports/etc. The correct scenario
and corresponding XCM programs are identified, and respectively, built
automatically based on runtime configuration of trusted teleporters and
trusted reserves.

#### Current limitations:
- while `fees` and "non-fee" `assets` CAN have different reserves (or
fees CAN be teleported), the remaining "non-fee" `assets` CANNOT, among
themselves, have different reserve locations (this is also implicitly
enforced by `MAX_ASSETS_FOR_TRANSFER=2`, but this can be safely
increased in the future).
- `fees` and "non-fee" `assets` CANNOT have **different remote**
reserves (this could also be supported in the future, but adds even more
complexity while possibly not being worth it - we'll see what the future
holds).

Fixes paritytech#1584
Fixes paritytech#2055

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Branislav Kontur <bkontur@gmail.com>

cumulus/parachain-template/runtime/src/xcm_config.rs

@@ -150,11 +150,6 @@ pub type XcmRouter = WithUniqueTopic<(
 	XcmpQueue,
 )>;
 
-#[cfg(feature = "runtime-benchmarks")]
-parameter_types! {
-	pub ReachableDest: Option<MultiLocation> = Some(Parent.into());
-}
-
 impl pallet_xcm::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type SendXcmOrigin = EnsureXcmOrigin<RuntimeOrigin, LocalOriginToLocation>;
@@ -180,8 +175,6 @@ impl pallet_xcm::Config for Runtime {
 	type SovereignAccountOf = LocationToAccountId;
 	type MaxLockers = ConstU32<8>;
 	type WeightInfo = pallet_xcm::TestWeightInfo;
-	#[cfg(feature = "runtime-benchmarks")]
-	type ReachableDest = ReachableDest;
 	type AdminOrigin = EnsureRoot<AccountId>;
 	type MaxRemoteLockConsumers = ConstU32<0>;
 	type RemoteLockConsumerIdentifier = ();

cumulus/parachains/integration-tests/emulated/chains/parachains/assets/asset-hub-rococo/src/lib.rs

@@ -21,7 +21,7 @@ use frame_support::traits::OnInitialize;
 // Cumulus
 use emulated_integration_tests_common::{
 	impl_accounts_helpers_for_parachain, impl_assert_events_helpers_for_parachain,
-	impl_assets_helpers_for_system_parachain, xcm_emulator::decl_test_parachains,
+	impl_assets_helpers_for_parachain, xcm_emulator::decl_test_parachains,
 };
 use rococo_emulated_chain::Rococo;
 
@@ -51,5 +51,5 @@ decl_test_parachains! {
 
 // AssetHubRococo implementation
 impl_accounts_helpers_for_parachain!(AssetHubRococo);
-impl_assert_events_helpers_for_parachain!(AssetHubRococo);
-impl_assets_helpers_for_system_parachain!(AssetHubRococo, Rococo);
+impl_assert_events_helpers_for_parachain!(AssetHubRococo, false);
+impl_assets_helpers_for_parachain!(AssetHubRococo, Rococo);

cumulus/parachains/integration-tests/emulated/chains/parachains/assets/asset-hub-westend/src/lib.rs

@@ -21,7 +21,7 @@ use frame_support::traits::OnInitialize;
 // Cumulus
 use emulated_integration_tests_common::{
 	impl_accounts_helpers_for_parachain, impl_assert_events_helpers_for_parachain,
-	impl_assets_helpers_for_system_parachain, xcm_emulator::decl_test_parachains,
+	impl_assets_helpers_for_parachain, xcm_emulator::decl_test_parachains,
 };
 use westend_emulated_chain::Westend;
 
@@ -51,5 +51,5 @@ decl_test_parachains! {
 
 // AssetHubWestend implementation
 impl_accounts_helpers_for_parachain!(AssetHubWestend);
-impl_assert_events_helpers_for_parachain!(AssetHubWestend);
-impl_assets_helpers_for_system_parachain!(AssetHubWestend, Westend);
+impl_assert_events_helpers_for_parachain!(AssetHubWestend, false);
+impl_assets_helpers_for_parachain!(AssetHubWestend, Westend);

cumulus/parachains/integration-tests/emulated/chains/parachains/assets/asset-hub-wococo/src/lib.rs

@@ -19,7 +19,7 @@ use frame_support::traits::OnInitialize;
 // Cumulus
 use emulated_integration_tests_common::{
 	impl_accounts_helpers_for_parachain, impl_assert_events_helpers_for_parachain,
-	impl_assets_helpers_for_system_parachain, xcm_emulator::decl_test_parachains,
+	impl_assets_helpers_for_parachain, xcm_emulator::decl_test_parachains,
 };
 use wococo_emulated_chain::Wococo;
 
@@ -49,5 +49,5 @@ decl_test_parachains! {
 
 // AssetHubWococo implementation
 impl_accounts_helpers_for_parachain!(AssetHubWococo);
-impl_assert_events_helpers_for_parachain!(AssetHubWococo);
-impl_assets_helpers_for_system_parachain!(AssetHubWococo, Wococo);
+impl_assert_events_helpers_for_parachain!(AssetHubWococo, false);
+impl_assets_helpers_for_parachain!(AssetHubWococo, Wococo);

cumulus/parachains/integration-tests/emulated/chains/parachains/bridges/bridge-hub-rococo/src/lib.rs

@@ -46,4 +46,4 @@ decl_test_parachains! {
 
 // BridgeHubRococo implementation
 impl_accounts_helpers_for_parachain!(BridgeHubRococo);
-impl_assert_events_helpers_for_parachain!(BridgeHubRococo);
+impl_assert_events_helpers_for_parachain!(BridgeHubRococo, false);

cumulus/parachains/integration-tests/emulated/chains/parachains/bridges/bridge-hub-westend/src/lib.rs

@@ -46,4 +46,4 @@ decl_test_parachains! {
 
 // BridgeHubWestend implementation
 impl_accounts_helpers_for_parachain!(BridgeHubWestend);
-impl_assert_events_helpers_for_parachain!(BridgeHubWestend);
+impl_assert_events_helpers_for_parachain!(BridgeHubWestend, false);

cumulus/parachains/integration-tests/emulated/chains/parachains/bridges/bridge-hub-wococo/src/lib.rs

@@ -44,4 +44,4 @@ decl_test_parachains! {
 
 // BridgeHubWococo implementation
 impl_accounts_helpers_for_parachain!(BridgeHubWococo);
-impl_assert_events_helpers_for_parachain!(BridgeHubWococo);
+impl_assert_events_helpers_for_parachain!(BridgeHubWococo, false);

cumulus/parachains/integration-tests/emulated/chains/parachains/testing/penpal/Cargo.toml

@@ -22,3 +22,4 @@ parachains-common = { path = "../../../../../../../parachains/common" }
 cumulus-primitives-core = { path = "../../../../../../../primitives/core", default-features = false }
 emulated-integration-tests-common = { path = "../../../../common", default-features = false }
 penpal-runtime = { path = "../../../../../../runtimes/testing/penpal" }
+rococo-emulated-chain = { path = "../../../relays/rococo" }

cumulus/parachains/integration-tests/emulated/chains/parachains/testing/penpal/src/lib.rs

@@ -21,8 +21,10 @@ use frame_support::traits::OnInitialize;
 
 // Cumulus
 use emulated_integration_tests_common::{
-	impl_assert_events_helpers_for_parachain, xcm_emulator::decl_test_parachains,
+	impl_accounts_helpers_for_parachain, impl_assert_events_helpers_for_parachain,
+	impl_assets_helpers_for_parachain, xcm_emulator::decl_test_parachains,
 };
+use rococo_emulated_chain::Rococo;
 
 // Penpal Parachain declaration
 decl_test_parachains! {
@@ -40,6 +42,7 @@ decl_test_parachains! {
 		pallets = {
 			PolkadotXcm: penpal_runtime::PolkadotXcm,
 			Assets: penpal_runtime::Assets,
+			Balances: penpal_runtime::Balances,
 		}
 	},
 	pub struct PenpalB {
@@ -56,10 +59,13 @@ decl_test_parachains! {
 		pallets = {
 			PolkadotXcm: penpal_runtime::PolkadotXcm,
 			Assets: penpal_runtime::Assets,
+			Balances: penpal_runtime::Balances,
 		}
 	},
 }
 
 // Penpal implementation
-impl_assert_events_helpers_for_parachain!(PenpalA);
-impl_assert_events_helpers_for_parachain!(PenpalB);
+impl_accounts_helpers_for_parachain!(PenpalA);
+impl_assets_helpers_for_parachain!(PenpalA, Rococo);
+impl_assert_events_helpers_for_parachain!(PenpalA, true);
+impl_assert_events_helpers_for_parachain!(PenpalB, true);

cumulus/parachains/integration-tests/emulated/chains/relays/westend/src/lib.rs

@@ -30,7 +30,7 @@ decl_test_relay_chains! {
 		on_init = (),
 		runtime = westend_runtime,
 		core = {
-			SovereignAccountOf: westend_runtime::xcm_config::LocationConverter, //TODO: rename to SovereignAccountOf,
+			SovereignAccountOf: westend_runtime::xcm_config::LocationConverter,
 		},
 		pallets = {
 			XcmPallet: westend_runtime::XcmPallet,

cumulus/parachains/integration-tests/emulated/common/src/impls.rs

@@ -399,7 +399,7 @@ macro_rules! impl_accounts_helpers_for_parachain {
 
 #[macro_export]
 macro_rules! impl_assert_events_helpers_for_parachain {
-	( $chain:ident ) => {
+	( $chain:ident, $ignore_weight:expr ) => {
 		$crate::impls::paste::paste! {
 			type [<$chain RuntimeEvent>]<N> = <$chain<N> as $crate::impls::Chain>::RuntimeEvent;
 
@@ -412,7 +412,7 @@ macro_rules! impl_assert_events_helpers_for_parachain {
 							[<$chain RuntimeEvent>]::<N>::PolkadotXcm(
 								$crate::impls::pallet_xcm::Event::Attempted { outcome: $crate::impls::Outcome::Complete(weight) }
 							) => {
-								weight: $crate::impls::weight_within_threshold(
+								weight: $ignore_weight || $crate::impls::weight_within_threshold(
 									($crate::impls::REF_TIME_THRESHOLD, $crate::impls::PROOF_SIZE_THRESHOLD),
 									expected_weight.unwrap_or(*weight),
 									*weight
@@ -434,7 +434,7 @@ macro_rules! impl_assert_events_helpers_for_parachain {
 							[<$chain RuntimeEvent>]::<N>::PolkadotXcm(
 								$crate::impls::pallet_xcm::Event::Attempted { outcome: $crate::impls::Outcome::Incomplete(weight, error) }
 							) => {
-								weight: $crate::impls::weight_within_threshold(
+								weight: $ignore_weight || $crate::impls::weight_within_threshold(
 									($crate::impls::REF_TIME_THRESHOLD, $crate::impls::PROOF_SIZE_THRESHOLD),
 									expected_weight.unwrap_or(*weight),
 									*weight
@@ -490,7 +490,7 @@ macro_rules! impl_assert_events_helpers_for_parachain {
 							[<$chain RuntimeEvent>]::<N>::MessageQueue($crate::impls::pallet_message_queue::Event::Processed {
 								success: true, weight_used: weight, ..
 							}) => {
-								weight: $crate::impls::weight_within_threshold(
+								weight: $ignore_weight || $crate::impls::weight_within_threshold(
 									($crate::impls::REF_TIME_THRESHOLD, $crate::impls::PROOF_SIZE_THRESHOLD),
 									expected_weight.unwrap_or(*weight),
 									*weight
@@ -510,7 +510,7 @@ macro_rules! impl_assert_events_helpers_for_parachain {
 							[<$chain RuntimeEvent>]::<N>::MessageQueue($crate::impls::pallet_message_queue::Event::Processed {
 								success: false, weight_used: weight, ..
 							}) => {
-								weight: $crate::impls::weight_within_threshold(
+								weight: $ignore_weight || $crate::impls::weight_within_threshold(
 									($crate::impls::REF_TIME_THRESHOLD, $crate::impls::PROOF_SIZE_THRESHOLD),
 									expected_weight.unwrap_or(*weight),
 									*weight
@@ -541,7 +541,7 @@ macro_rules! impl_assert_events_helpers_for_parachain {
 						vec![
 							[<$chain RuntimeEvent>]::<N>::MessageQueue($crate::impls::pallet_message_queue::Event::Processed { success: true, weight_used: weight, .. }
 							) => {
-								weight: $crate::impls::weight_within_threshold(
+								weight: $ignore_weight || $crate::impls::weight_within_threshold(
 									($crate::impls::REF_TIME_THRESHOLD, $crate::impls::PROOF_SIZE_THRESHOLD),
 									expected_weight.unwrap_or(*weight),
 									*weight
@@ -556,7 +556,7 @@ macro_rules! impl_assert_events_helpers_for_parachain {
 }
 
 #[macro_export]
-macro_rules! impl_assets_helpers_for_system_parachain {
+macro_rules! impl_assets_helpers_for_parachain {
 	( $chain:ident, $relay_chain:ident ) => {
 		$crate::impls::paste::paste! {
 			impl<N: $crate::impls::Network> $chain<N> {

cumulus/parachains/integration-tests/emulated/tests/assets/asset-hub-rococo/Cargo.toml

@@ -17,6 +17,7 @@ frame-support = { path = "../../../../../../../substrate/frame/support", default
 pallet-balances = { path = "../../../../../../../substrate/frame/balances", default-features = false}
 pallet-assets = { path = "../../../../../../../substrate/frame/assets", default-features = false}
 pallet-asset-conversion = { path = "../../../../../../../substrate/frame/asset-conversion", default-features = false}
+pallet-message-queue = { path = "../../../../../../../substrate/frame/message-queue", default-features = false }
 
 # Polkadot
 xcm = { package = "staging-xcm", path = "../../../../../../../polkadot/xcm", default-features = false}
@@ -28,5 +29,6 @@ rococo-runtime = { path = "../../../../../../../polkadot/runtime/rococo" }
 asset-test-utils = { path = "../../../../../runtimes/assets/test-utils" }
 parachains-common = { path = "../../../../../../parachains/common" }
 asset-hub-rococo-runtime = { path = "../../../../../runtimes/assets/asset-hub-rococo" }
-emulated-integration-tests-common = { path = "../../../common", default-features = false}
+emulated-integration-tests-common = { path = "../../../common", default-features = false }
+penpal-runtime = { path = "../../../../../runtimes/testing/penpal" }
 rococo-system-emulated-network ={ path = "../../../networks/rococo-system" }

cumulus/parachains/integration-tests/emulated/tests/assets/asset-hub-rococo/src/lib.rs

@@ -61,18 +61,20 @@ pub const ASSET_MIN_BALANCE: u128 = 1000;
 pub const ASSETS_PALLET_ID: u8 = 50;
 
 pub type RelayToSystemParaTest = Test<Rococo, AssetHubRococo>;
+pub type RelayToParaTest = Test<Rococo, PenpalA>;
 pub type SystemParaToRelayTest = Test<AssetHubRococo, Rococo>;
 pub type SystemParaToParaTest = Test<AssetHubRococo, PenpalA>;
+pub type ParaToSystemParaTest = Test<PenpalA, AssetHubRococo>;
 
-/// Returns a `TestArgs` instance to de used for the Relay Chain accross integraton tests
-pub fn relay_test_args(amount: Balance) -> TestArgs {
+/// Returns a `TestArgs` instance to be used for the Relay Chain across integration tests
+pub fn relay_test_args(
+	dest: MultiLocation,
+	beneficiary_id: AccountId32,
+	amount: Balance,
+) -> TestArgs {
 	TestArgs {
-		dest: Rococo::child_location_of(AssetHubRococo::para_id()),
-		beneficiary: AccountId32Junction {
-			network: None,
-			id: AssetHubRococoReceiver::get().into(),
-		}
-		.into(),
+		dest,
+		beneficiary: AccountId32Junction { network: None, id: beneficiary_id.into() }.into(),
 		amount,
 		assets: (Here, amount).into(),
 		asset_id: None,
@@ -81,21 +83,22 @@ pub fn relay_test_args(amount: Balance) -> TestArgs {
 	}
 }
 
-/// Returns a `TestArgs` instance to de used for the System Parachain accross integraton tests
-pub fn system_para_test_args(
+/// Returns a `TestArgs` instance to be used by parachains across integration tests
+pub fn para_test_args(
 	dest: MultiLocation,
 	beneficiary_id: AccountId32,
 	amount: Balance,
 	assets: MultiAssets,
 	asset_id: Option<u32>,
+	fee_asset_item: u32,
 ) -> TestArgs {
 	TestArgs {
 		dest,
 		beneficiary: AccountId32Junction { network: None, id: beneficiary_id.into() }.into(),
 		amount,
 		assets,
 		asset_id,
-		fee_asset_item: 0,
+		fee_asset_item,
 		weight_limit: WeightLimit::Unlimited,
 	}
 }