fix: pay fees benchmark

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

@@ -2000,7 +2000,7 @@ impl_runtime_apis! {
 				fn fee_asset() -> Result<Asset, BenchmarkError> {
 					Ok(Asset {
 						id: AssetId(WestendLocation::get()),
-						fun: Fungible(1_000_000 * UNITS),
+						fun: Fungible(1_000 * UNITS),
 					})
 				}
 

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

@@ -103,10 +103,10 @@ benchmarks! {
 
 		let mut executor = new_executor::<T>(Default::default());
 		executor.set_holding(holding);
+		// Set some weight to be paid for.
+		executor.set_message_weight(Weight::from_parts(100_000_000, 100_000));
 
-		let fee_asset: Asset = T::fee_asset().unwrap_or(
-			(Here, 100_000_000u128).into()
-		);
+		let fee_asset: Asset = T::fee_asset().unwrap();
 
 		let instruction = Instruction::<XcmCallOf<T>>::PayFees { asset: fee_asset };
 

polkadot/xcm/xcm-builder/src/weight.rs

@@ -231,7 +231,7 @@ impl<
 		log::trace!(target: "xcm::weight", "UsingComponents::buy_weight weight: {:?}, payment: {:?}, context: {:?}", weight, payment, context);
 		let amount = WeightToFee::weight_to_fee(&weight);
 		let u128_amount: u128 = amount.try_into().map_err(|_| XcmError::Overflow)?;
-		let required = (AssetId(AssetIdValue::get()), u128_amount).into();
+		let required = Asset { id: AssetId(AssetIdValue::get()), fun: Fungible(u128_amount) };
 		let unused = payment.checked_sub(required).map_err(|_| XcmError::TooExpensive)?;
 		self.0 = self.0.saturating_add(weight);
 		self.1 = self.1.saturating_add(amount);

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

@@ -197,6 +197,9 @@ impl<Config: config::Config> XcmExecutor<Config> {
 	pub fn asset_claimer(&self) -> Option<Location> {
 		self.asset_claimer.clone()
 	}
+	pub fn set_message_weight(&mut self, weight: Weight) {
+		self.message_weight = weight;
+	}
 }
 
 pub struct WeighedMessage<Call>(Weight, Xcm<Call>);
@@ -1298,9 +1301,22 @@ impl<Config: config::Config> XcmExecutor<Config> {
 				result
 			},
 			PayFees { asset } => {
+				// Message was not weighed, there is nothing to pay.
+				if self.message_weight == Weight::zero() {
+					tracing::warn!(
+						target: "xcm::executor::PayFees",
+						"Message was not weighed or weight was 0. Nothing will be charged.",
+					);
+					return Ok(());
+				}
 				// Record old holding in case we need to rollback.
 				let old_holding = self.holding.clone();
 				// The max we're willing to pay for fees is decided by the `asset` operand.
+				tracing::trace!(
+					target: "xcm::executor::PayFees",
+					asset_for_fees = ?asset,
+					message_weight = ?self.message_weight,
+				);
 				let max_fee =
 					self.holding.try_take(asset.into()).map_err(|_| XcmError::NotHoldingFees)?;
 				// Pay for execution fees.