add FeeManager to pallet xcm

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

@@ -66,6 +66,7 @@ use xcm_builder::{
 use xcm_executor::XcmExecutor;
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const TokenLocation: Location = Location::parent();
 	pub const RelayNetwork: NetworkId = NetworkId::ByGenesis(ROCOCO_GENESIS_HASH);
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
@@ -315,6 +316,7 @@ pub type ForeignAssetFeeAsExistentialDepositMultiplierFeeCharger =
 /// either execution or delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 );

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

@@ -63,6 +63,7 @@ use xcm_builder::{
 use xcm_executor::XcmExecutor;
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const WestendLocation: Location = Location::parent();
 	pub const RelayNetwork: Option<NetworkId> = Some(NetworkId::ByGenesis(WESTEND_GENESIS_HASH));
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
@@ -336,6 +337,7 @@ pub type ForeignAssetFeeAsExistentialDepositMultiplierFeeCharger =
 /// either execution or delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 	FellowshipEntities,

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/xcm_config.rs

@@ -57,6 +57,7 @@ use xcm_executor::{
 };
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const TokenLocation: Location = Location::parent();
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
 	pub RelayNetwork: NetworkId = NetworkId::ByGenesis(ROCOCO_GENESIS_HASH);
@@ -164,6 +165,7 @@ pub type Barrier = TrailingSetTopicAsId<
 /// either execution or delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 );

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/xcm_config.rs

@@ -56,6 +56,7 @@ use xcm_executor::{
 };
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const WestendLocation: Location = Location::parent();
 	pub const RelayNetwork: NetworkId = NetworkId::ByGenesis(WESTEND_GENESIS_HASH);
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
@@ -161,6 +162,7 @@ pub type Barrier = TrailingSetTopicAsId<
 /// either execution or delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 );

cumulus/parachains/runtimes/contracts/contracts-rococo/src/xcm_config.rs

@@ -51,6 +51,7 @@ use xcm_builder::{
 use xcm_executor::XcmExecutor;
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const RelayLocation: Location = Location::parent();
 	pub const RelayNetwork: NetworkId = NetworkId::ByGenesis(ROCOCO_GENESIS_HASH);
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
@@ -166,6 +167,7 @@ pub type Barrier = TrailingSetTopicAsId<
 /// either execution or delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 );

cumulus/parachains/runtimes/coretime/coretime-rococo/src/xcm_config.rs

@@ -52,6 +52,7 @@ use xcm_builder::{
 use xcm_executor::XcmExecutor;
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const RocRelayLocation: Location = Location::parent();
 	pub const RelayNetwork: Option<NetworkId> = Some(NetworkId::ByGenesis(ROCOCO_GENESIS_HASH));
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
@@ -177,6 +178,7 @@ parameter_types! {
 /// Locations that will not be charged fees in the executor, neither for execution nor delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 );

cumulus/parachains/runtimes/coretime/coretime-westend/src/xcm_config.rs

@@ -52,6 +52,7 @@ use xcm_builder::{
 use xcm_executor::XcmExecutor;
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	pub const TokenRelayLocation: Location = Location::parent();
 	pub const RelayNetwork: Option<NetworkId> = Some(NetworkId::ByGenesis(WESTEND_GENESIS_HASH));
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
@@ -185,6 +186,7 @@ parameter_types! {
 /// Locations that will not be charged fees in the executor, neither for execution nor delivery.
 /// We only waive fees for system functions, which these locations represent.
 pub type WaivedLocations = (
+	Equals<RootLocation>,
 	RelayOrOtherSystemParachains<AllSiblingSystemParachains, Runtime>,
 	Equals<RelayTreasuryLocation>,
 );

cumulus/parachains/runtimes/testing/penpal/src/xcm_config.rs

@@ -39,6 +39,7 @@ use frame_support::{
 	},
 	weights::Weight,
 };
+use frame_support::traits::Equals;
 use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{xcm_config::AssetFeeAsExistentialDepositMultiplier, TREASURY_PALLET_ID};
@@ -210,6 +211,7 @@ pub type XcmOriginToTransactDispatchOrigin = (
 );
 
 parameter_types! {
+	pub const RootLocation: Location = Location::here();
 	// One XCM operation is 1_000_000_000 weight - almost certainly a conservative estimate.
 	pub UnitWeightCost: Weight = Weight::from_parts(1_000_000_000, 64 * 1024);
 	pub const MaxInstructions: u32 = 100;
@@ -336,6 +338,7 @@ pub type TrustedReserves = (
 pub type TrustedTeleporters =
 	(AssetFromChain<LocalTeleportableToAssetHub, SystemAssetHubLocation>,);
 
+pub type WaivedLocations = Equals<RootLocation>;
 /// `AssetId`/`Balance` converter for `TrustBackedAssets`.
 pub type TrustBackedAssetsConvertedConcreteId =
 	assets_common::TrustBackedAssetsConvertedConcreteId<AssetsPalletLocation, Balance>;
@@ -399,7 +402,7 @@ impl xcm_executor::Config for XcmConfig {
 	type AssetLocker = ();
 	type AssetExchanger = PoolAssetsExchanger;
 	type FeeManager = XcmFeeManagerFromComponents<
-		(),
+		WaivedLocations,
 		SendXcmFeeToAccount<Self::AssetTransactor, TreasuryAccount>,
 	>;
 	type MessageExporter = ();

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

@@ -75,6 +75,7 @@
 
 #[cfg(any(feature = "try-runtime", test))]
 use sp_runtime::TryRuntimeError;
+use xcm_executor::traits::{FeeManager, FeeReason};
 
 pub trait WeightInfo {
 	fn send() -> Weight;
@@ -240,7 +241,7 @@
 		type XcmExecuteFilter: Contains<(Location, Xcm<<Self as Config>::RuntimeCall>)>;
 
 		/// Something to execute an XCM message.
-		type XcmExecutor: ExecuteXcm<<Self as Config>::RuntimeCall> + XcmAssetTransfers;
+		type XcmExecutor: ExecuteXcm<<Self as Config>::RuntimeCall> + XcmAssetTransfers + FeeManager;
 
 		/// Our XCM filter which messages to be teleported using the dedicated extrinsic must pass.
 		type XcmTeleportFilter: Contains<(Location, Vec<Asset>)>;
@@ -2468,17 +2469,16 @@
 		mut message: Xcm<()>,
 	) -> Result<XcmHash, SendError> {
 		let interior = interior.into();
+		let local_origin = interior.clone().into();
 		let dest = dest.into();
-		let maybe_fee_payer = if interior != Junctions::Here {
+        let is_waived = <T::XcmExecutor as FeeManager>::is_waived(Some(&origin_dest), FeeReason::ChargeFees);
+		if interior != Junctions::Here {
 			message.0.insert(0, DescendOrigin(interior.clone()));
-			Some(interior.into())
-		} else {
-			None
-		};
+		}
 		tracing::debug!(target: "xcm::send_xcm", "{:?}, {:?}", dest.clone(), message.clone());
 		let (ticket, price) = validate_send::<T::XcmRouter>(dest, message)?;
-		if let Some(fee_payer) = maybe_fee_payer {
-			Self::charge_fees(fee_payer, price).map_err(|e| {
+		if !is_waived {
+			Self::charge_fees(local_origin, price).map_err(|e| {
 				tracing::error!(
 					target: "xcm::pallet_xcm::send_xcm",
 					?e,

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

@@ -304,6 +304,16 @@ impl<Config: config::Config> XcmAssetTransfers for XcmExecutor<Config> {
 	type AssetTransactor = Config::AssetTransactor;
 }
 
+impl <Config: config::Config> FeeManager for XcmExecutor<Config> {
+	fn is_waived(origin: Option<&Location>, r: FeeReason) -> bool {
+		Config::FeeManager::is_waived(origin, r)
+	}
+
+	fn handle_fee(fee: Assets, context: Option<&XcmContext>, r: FeeReason) {
+		Config::FeeManager::handle_fee(fee, context, r)
+	}
+}
+
 #[derive(Debug)]
 pub struct ExecutorError {
 	pub index: u32,

prdoc/pr_5363.prdoc

@@ -0,0 +1,14 @@
+title: "[pallet-xcm] waive transport fees based on XcmConfig"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      pallet-xcm::send() no longer implicitly waives transport fees for the local root location,
+      but instead relies on xcm_executor::Config::FeeManager to determine whether certain locations have free transport.
+
+      🚨 Warning: 🚨 If your chain relies on free transport for local root, please make
+      sure to add Location::here() to the waived-fee locations in your configured xcm_executor::Config::FeeManager.
+
+crates:
+  - name: pallet-xcm
+    bump: major