XCM Fee Payment Runtime API

Cargo.toml

@@ -214,6 +214,7 @@ members = [
 	"polkadot/xcm/xcm-builder",
 	"polkadot/xcm/xcm-executor",
 	"polkadot/xcm/xcm-executor/integration-tests",
+	"polkadot/xcm/xcm-fee-payment-runtime-api",
 	"polkadot/xcm/xcm-simulator",
 	"polkadot/xcm/xcm-simulator/example",
 	"polkadot/xcm/xcm-simulator/fuzzer",

polkadot/node/service/Cargo.toml

@@ -142,6 +142,9 @@ polkadot-node-core-pvf-checker = { path = "../core/pvf-checker", optional = true
 polkadot-node-core-runtime-api = { path = "../core/runtime-api", optional = true }
 polkadot-statement-distribution = { path = "../network/statement-distribution", optional = true }
 
+xcm = { package = "staging-xcm", path = "../../xcm" }
+xcm-fee-payment-runtime-api = { path = "../../xcm/xcm-fee-payment-runtime-api" }
+
 [dev-dependencies]
 polkadot-test-client = { path = "../test/client" }
 polkadot-node-subsystem-test-helpers = { path = "../subsystem-test-helpers" }
@@ -219,10 +222,7 @@ try-runtime = [
 	"sp-runtime/try-runtime",
 	"westend-runtime?/try-runtime",
 ]
-fast-runtime = [
-	"rococo-runtime?/fast-runtime",
-	"westend-runtime?/fast-runtime",
-]
+fast-runtime = ["rococo-runtime?/fast-runtime", "westend-runtime?/fast-runtime"]
 
 malus = ["full-node"]
 runtime-metrics = [

polkadot/node/service/src/fake_runtime_api.rs

@@ -30,6 +30,7 @@ use polkadot_primitives::{
 	ScrapedOnChainVotes, SessionIndex, SessionInfo, ValidationCode, ValidationCodeHash,
 	ValidatorId, ValidatorIndex, ValidatorSignature,
 };
+
 use sp_core::OpaqueMetadata;
 use sp_runtime::{
 	traits::Block as BlockT,
@@ -39,7 +40,7 @@ use sp_runtime::{
 use sp_version::RuntimeVersion;
 use sp_weights::Weight;
 use std::collections::BTreeMap;
-
+use xcm::{VersionedAssetId, VersionedAssets, VersionedLocation, VersionedXcm};
 sp_api::decl_runtime_apis! {
 	/// This runtime API is only implemented for the test runtime!
 	pub trait GetLastTimestamp {
@@ -396,4 +397,22 @@ sp_api::impl_runtime_apis! {
 			unimplemented!()
 		}
 	}
+
+	impl xcm_fee_payment_runtime_api::XcmPaymentApi<Block> for Runtime {
+		fn query_acceptable_payment_assets(_: xcm::Version) -> Result<Vec<VersionedAssetId>, xcm_fee_payment_runtime_api::Error> {
+			unimplemented!()
+		}
+
+		fn query_weight_to_asset_fee(_: Weight, _: VersionedAssetId) -> Result<u128, xcm_fee_payment_runtime_api::Error> {
+			unimplemented!()
+		}
+
+		fn query_xcm_weight(_: VersionedXcm<()>) -> Result<Weight, xcm_fee_payment_runtime_api::Error> {
+			unimplemented!()
+		}
+
+		fn query_delivery_fees(_: VersionedLocation, _: VersionedXcm<()>) -> Result<VersionedAssets, xcm_fee_payment_runtime_api::Error> {
+			unimplemented!()
+		}
+	}
 }

polkadot/runtime/rococo/Cargo.toml

@@ -104,6 +104,7 @@ polkadot-parachain-primitives = { path = "../../parachain", default-features = f
 xcm = { package = "staging-xcm", path = "../../xcm", default-features = false }
 xcm-executor = { package = "staging-xcm-executor", path = "../../xcm/xcm-executor", default-features = false }
 xcm-builder = { package = "staging-xcm-builder", path = "../../xcm/xcm-builder", default-features = false }
+xcm-fee-payment-runtime-api = { path = "../../xcm/xcm-fee-payment-runtime-api", default-features = false }
 
 [dev-dependencies]
 tiny-keccak = { version = "2.0.2", features = ["keccak"] }
@@ -208,6 +209,7 @@ std = [
 	"tx-pool-api/std",
 	"xcm-builder/std",
 	"xcm-executor/std",
+	"xcm-fee-payment-runtime-api/std",
 	"xcm/std",
 ]
 runtime-benchmarks = [

polkadot/runtime/rococo/src/lib.rs

@@ -75,7 +75,7 @@ use frame_support::{
 		InstanceFilter, KeyOwnerProofSystem, LinearStoragePrice, PrivilegeCmp, ProcessMessage,
 		ProcessMessageError, StorageMapShim, WithdrawReasons,
 	},
-	weights::{ConstantMultiplier, WeightMeter},
+	weights::{ConstantMultiplier, WeightMeter, WeightToFee as _},
 	PalletId,
 };
 use frame_system::{EnsureRoot, EnsureSigned};
@@ -98,7 +98,10 @@ use sp_staking::SessionIndex;
 #[cfg(any(feature = "std", test))]
 use sp_version::NativeVersion;
 use sp_version::RuntimeVersion;
-use xcm::{latest::prelude::*, VersionedLocation};
+use xcm::{
+	latest::prelude::*, IntoVersion, VersionedAssetId, VersionedAssets, VersionedLocation,
+	VersionedXcm,
+};
 use xcm_builder::PayOverXcm;
 
 pub use frame_system::Call as SystemCall;
@@ -123,6 +126,7 @@ use governance::{
 	pallet_custom_origins, AuctionAdmin, Fellows, GeneralAdmin, LeaseAdmin, Treasurer,
 	TreasurySpender,
 };
+use xcm_fee_payment_runtime_api::Error as XcmPaymentApiError;
 
 #[cfg(test)]
 mod tests;
@@ -217,7 +221,7 @@ pub struct OriginPrivilegeCmp;
 impl PrivilegeCmp<OriginCaller> for OriginPrivilegeCmp {
 	fn cmp_privilege(left: &OriginCaller, right: &OriginCaller) -> Option<Ordering> {
 		if left == right {
-			return Some(Ordering::Equal)
+			return Some(Ordering::Equal);
 		}
 
 		match (left, right) {
@@ -1508,11 +1512,11 @@ pub mod migrations {
 			let now = frame_system::Pallet::<Runtime>::block_number();
 			let lease = slots::Pallet::<Runtime>::lease(para);
 			if lease.is_empty() {
-				return None
+				return None;
 			}
 			// Lease not yet started, ignore:
 			if lease.iter().any(Option::is_none) {
-				return None
+				return None;
 			}
 			let (index, _) =
 				<slots::Pallet<Runtime> as Leaser<BlockNumber>>::lease_period_index(now)?;
@@ -1574,7 +1578,7 @@ pub mod migrations {
 		fn pre_upgrade() -> Result<sp_std::vec::Vec<u8>, sp_runtime::TryRuntimeError> {
 			if System::last_runtime_upgrade_spec_version() > UPGRADE_SESSION_KEYS_FROM_SPEC {
 				log::warn!(target: "runtime::session_keys", "Skipping session keys migration pre-upgrade check due to spec version (already applied?)");
-				return Ok(Vec::new())
+				return Ok(Vec::new());
 			}
 
 			log::info!(target: "runtime::session_keys", "Collecting pre-upgrade session keys state");
@@ -1603,7 +1607,7 @@ pub mod migrations {
 		fn on_runtime_upgrade() -> Weight {
 			if System::last_runtime_upgrade_spec_version() > UPGRADE_SESSION_KEYS_FROM_SPEC {
 				log::info!("Skipping session keys upgrade: already applied");
-				return <Runtime as frame_system::Config>::DbWeight::get().reads(1)
+				return <Runtime as frame_system::Config>::DbWeight::get().reads(1);
 			}
 			log::trace!("Upgrading session keys");
 			Session::upgrade_keys::<OldSessionKeys, _>(transform_session_keys);
@@ -1616,7 +1620,7 @@ pub mod migrations {
 		) -> Result<(), sp_runtime::TryRuntimeError> {
 			if System::last_runtime_upgrade_spec_version() > UPGRADE_SESSION_KEYS_FROM_SPEC {
 				log::warn!(target: "runtime::session_keys", "Skipping session keys migration post-upgrade check due to spec version (already applied?)");
-				return Ok(())
+				return Ok(());
 			}
 
 			let key_ids = SessionKeys::key_ids();
@@ -1799,6 +1803,37 @@ sp_api::impl_runtime_apis! {
 		}
 	}
 
+	impl xcm_fee_payment_runtime_api::XcmPaymentApi<Block> for Runtime {
+		fn query_acceptable_payment_assets(xcm_version: xcm::Version) -> Result<Vec<VersionedAssetId>, XcmPaymentApiError> {
+			if !matches!(xcm_version, 3 | 4) {
+				return Err(XcmPaymentApiError::UnhandledXcmVersion);
+			}
+			Ok([VersionedAssetId::V4(xcm_config::TokenLocation::get().into())]
+				.into_iter()
+				.filter_map(|asset| asset.into_version(xcm_version).ok())
+				.collect())
+		}
+
+		fn query_weight_to_asset_fee(weight: Weight, asset: VersionedAssetId) -> Result<u128, XcmPaymentApiError> {
+			let local_asset = VersionedAssetId::V4(xcm_config::TokenLocation::get().into());
+			let asset = asset
+				.into_version(4)
+				.map_err(|_| XcmPaymentApiError::VersionedConversionFailed)?;
+
+			if  asset != local_asset { return Err(XcmPaymentApiError::AssetNotFound); }
+
+			Ok(WeightToFee::weight_to_fee(&weight))
+		}
+
+		fn query_xcm_weight(message: VersionedXcm<()>) -> Result<Weight, XcmPaymentApiError> {
+			XcmPallet::query_xcm_weight(message)
+		}
+
+		fn query_delivery_fees(destination: VersionedLocation, message: VersionedXcm<()>) -> Result<VersionedAssets, XcmPaymentApiError> {
+			XcmPallet::query_delivery_fees(destination, message)
+		}
+	}
+
 	impl sp_api::Metadata<Block> for Runtime {
 		fn metadata() -> OpaqueMetadata {
 			OpaqueMetadata::new(Runtime::metadata().into())
@@ -2509,7 +2544,7 @@ mod remote_tests {
 	#[tokio::test]
 	async fn run_migrations() {
 		if var("RUN_MIGRATION_TESTS").is_err() {
-			return
+			return;
 		}
 
 		sp_tracing::try_init_simple();

polkadot/runtime/westend/Cargo.toml

@@ -114,6 +114,7 @@ runtime-parachains = { package = "polkadot-runtime-parachains", path = "../parac
 xcm = { package = "staging-xcm", path = "../../xcm", default-features = false }
 xcm-executor = { package = "staging-xcm-executor", path = "../../xcm/xcm-executor", default-features = false }
 xcm-builder = { package = "staging-xcm-builder", path = "../../xcm/xcm-builder", default-features = false }
+xcm-fee-payment-runtime-api = { path = "../../xcm/xcm-fee-payment-runtime-api", default-features = false }
 
 [dev-dependencies]
 hex-literal = "0.4.1"
@@ -227,6 +228,7 @@ std = [
 	"westend-runtime-constants/std",
 	"xcm-builder/std",
 	"xcm-executor/std",
+	"xcm-fee-payment-runtime-api/std",
 	"xcm/std",
 ]
 runtime-benchmarks = [