Revamp xcm executor to add destination to FeeReason

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/xcm_config.rs

@@ -45,7 +45,10 @@ use parachains_common::{
 use polkadot_parachain_primitives::primitives::Sibling;
 use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use snowbridge_router_primitives::inbound::GlobalConsensusEthereumConvertsFor;
-use sp_runtime::traits::{AccountIdConversion, ConvertInto};
+use sp_runtime::{
+	traits::{AccountIdConversion, ConvertInto},
+	SaturatedConversion,
+};
 use sp_std::marker::PhantomData;
 use testnet_parachains_constants::rococo::snowbridge::{
 	EthereumNetwork, INBOUND_QUEUE_PALLET_INDEX,
@@ -60,15 +63,15 @@ use xcm_builder::{
 	AllowHrmpNotificationsFromRelayChain, AllowKnownQueryResponses, AllowSubscriptionsFrom,
 	AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain, DenyThenTry,
 	DescribeAllTerminal, DescribeFamily, EnsureXcmOrigin, ExporterFor, FrameTransactionalProcessor,
-	FungibleAdapter, FungiblesAdapter, GlobalConsensusParachainConvertsFor, HashedDescription,
-	InspectMessageQueues, IsConcrete, LocalMint, NetworkExportTableItem, NoChecking,
-	NonFungiblesAdapter, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
+	FungibleAdapter, FungiblesAdapter, GlobalConsensusParachainConvertsFor, HandleFee,
+	HashedDescription, InspectMessageQueues, IsConcrete, LocalMint, NetworkExportTableItem,
+	NoChecking, NonFungiblesAdapter, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
 	SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, StartsWith,
 	StartsWithExplicitGlobalConsensus, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
 	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
 };
-use xcm_executor::XcmExecutor;
+use xcm_executor::{traits::FeeReason, XcmExecutor};
 
 parameter_types! {
 	pub const TokenLocation: Location = Location::parent();
@@ -420,7 +423,15 @@ impl xcm_executor::Config for XcmConfig {
 	type AssetExchanger = ();
 	type FeeManager = XcmFeeManagerFromComponents<
 		WaivedLocations,
-		SendXcmFeeToAccount<Self::AssetTransactor, TreasuryAccount>,
+		(
+			SnowbridgeExportFee<
+				Balance,
+				bridging::to_ethereum::BridgeHubEthereumBaseFee,
+				TokenLocation,
+				bridging::to_ethereum::EthereumLocation,
+			>,
+			SendXcmFeeToAccount<Self::AssetTransactor, TreasuryAccount>,
+		),
 	>;
 	type MessageExporter = ();
 	type UniversalAliases =
@@ -536,6 +547,58 @@ impl<Bridges, Router: InspectMessageQueues, UniversalLocation> InspectMessageQue
 	}
 }
 
+pub struct SnowbridgeExportFee<Balance, ExportFeeBalance, FeeAssetLocation, EthereumLocation>(
+	PhantomData<(Balance, ExportFeeBalance, FeeAssetLocation, EthereumLocation)>,
+);
+
+impl<Balance, ExportFeeBalance, FeeAssetLocation, EthereumLocation> HandleFee
+	for SnowbridgeExportFee<Balance, ExportFeeBalance, FeeAssetLocation, EthereumLocation>
+where
+	Balance: From<u128> + Into<u128>,
+	ExportFeeBalance: Get<Balance>,
+	FeeAssetLocation: Get<Location>,
+	EthereumLocation: Get<Location>,
+{
+	fn handle_fee(
+		fees: xcm::prelude::Assets,
+		_context: Option<&XcmContext>,
+		reason: FeeReason,
+	) -> xcm::prelude::Assets {
+		// Check the reason to see if this export is for snowbridge.
+		if !matches!(reason, FeeReason::InitiateReserveWithdraw { destination }
+			if destination == EthereumLocation::get()
+		) || fees.len() != 1
+		{
+			return fees
+		}
+
+		let fee = fees.get(0);
+
+		if let Some(Asset { id: location, .. }) = fee {
+			if location.0 != FeeAssetLocation::get() {
+				return fees
+			}
+		}
+
+		let fee_amount: Option<u128> = if let Some(Asset { fun: Fungible(amount), .. }) = fee {
+			Some(amount.clone())
+		} else {
+			None
+		};
+
+		if fee_amount.is_none() {
+			return fees
+		}
+
+		let export_fee_balance = ExportFeeBalance::get();
+
+		let delivery_fee =
+			fee_amount.unwrap().saturating_sub(export_fee_balance.saturated_into::<u128>());
+
+		return Asset::from((FeeAssetLocation::get(), delivery_fee)).into()
+	}
+}
+
 /// The means for routing XCM messages which are not for local execution into the right message
 /// queues.
 pub type XcmRouter = WithUniqueTopic<(
@@ -735,6 +798,8 @@ pub mod bridging {
 					PalletInstance(INBOUND_QUEUE_PALLET_INDEX)
 				]
 			);
+			pub EthereumLocation: Location = Location::new(2, [GlobalConsensus(EthereumNetwork::get())]);
+
 
 			/// Set up exporters configuration.
 			/// `Option<Asset>` represents static "base fee" which is used for total delivery fee calculation.

polkadot/xcm/pallet-xcm-benchmarks/src/fungible/benchmarking.rs

@@ -150,8 +150,8 @@ benchmarks_instance_pallet! {
 
 		let (expected_fees_mode, expected_assets_in_holding) = T::DeliveryHelper::ensure_successful_delivery(
 			&sender_location,
-			&reserve,
-			FeeReason::InitiateReserveWithdraw,
+			&reserve.clone(),
+			FeeReason::InitiateReserveWithdraw{ destination:reserve.clone() },
 		);
 		let sender_account_balance_before = T::TransactAsset::balance(&sender_account);
 
@@ -175,7 +175,7 @@ benchmarks_instance_pallet! {
 		let instruction = Instruction::InitiateReserveWithdraw {
 			// Worst case is looking through all holdings for every asset explicitly - respecting the limit `MAX_ITEMS_IN_ASSETS`.
 			assets: Definite(holding.into_inner().into_iter().take(MAX_ITEMS_IN_ASSETS).collect::<Vec<_>>().into()),
-			reserve,
+			reserve: reserve.clone(),
 			xcm: Xcm(vec![])
 		};
 		let xcm = Xcm(vec![instruction]);

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

@@ -901,7 +901,11 @@ impl<Config: config::Config> XcmExecutor<Config> {
 					message.extend(xcm.0.into_iter());
 					// put back transport_fee in holding register to be charged by XcmSender
 					self.holding.subsume_assets(transport_fee);
-					self.send(dest, Xcm(message), FeeReason::DepositReserveAsset)?;
+					self.send(
+						dest.clone(),
+						Xcm(message),
+						FeeReason::DepositReserveAsset { destination: dest },
+					)?;
 					Ok(())
 				});
 				if Config::TransactionalProcessor::IS_TRANSACTIONAL && result.is_err() {
@@ -921,7 +925,11 @@ impl<Config: config::Config> XcmExecutor<Config> {
 					);
 					let mut message = vec![WithdrawAsset(assets), ClearOrigin];
 					message.extend(xcm.0.into_iter());
-					self.send(reserve, Xcm(message), FeeReason::InitiateReserveWithdraw)?;
+					self.send(
+						reserve.clone(),
+						Xcm(message),
+						FeeReason::InitiateReserveWithdraw { destination: reserve },
+					)?;
 					Ok(())
 				});
 				if Config::TransactionalProcessor::IS_TRANSACTIONAL && result.is_err() {

polkadot/xcm/xcm-executor/src/traits/fee_manager.rs

@@ -34,9 +34,9 @@ pub enum FeeReason {
 	/// When the `TransferReserveAsset` instruction is called.
 	TransferReserveAsset,
 	/// When the `DepositReserveAsset` instruction is called.
-	DepositReserveAsset,
+	DepositReserveAsset { destination: Location },
 	/// When the `InitiateReserveWithdraw` instruction is called.
-	InitiateReserveWithdraw,
+	InitiateReserveWithdraw { destination: Location },
 	/// When the `InitiateTeleport` instruction is called.
 	InitiateTeleport,
 	/// When the `QueryPallet` instruction is called.