Allow configuration of worst case buy execution weight

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

@@ -102,11 +102,13 @@ mod benchmarks {
 		let mut executor = new_executor::<T>(Default::default());
 		executor.set_holding(holding);
 
-		let fee_asset = AssetId(Here.into());
+		// The worst case we want for buy execution in terms of
+		// fee asset and weight
+		let (fee_asset, weight_limit) = T::worst_case_buy_execution()?;
 
 		let instruction = Instruction::<XcmCallOf<T>>::BuyExecution {
-			fees: (fee_asset, 100_000_000u128).into(), // should be something inside of holding
-			weight_limit: WeightLimit::Unlimited,
+			fees: fee_asset,
+			weight_limit: weight_limit.into(),
 		};
 
 		let xcm = Xcm(vec![instruction]);

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

@@ -26,7 +26,10 @@ pub mod pallet {
 	use frame_benchmarking::BenchmarkError;
 	use frame_support::{dispatch::GetDispatchInfo, pallet_prelude::Encode};
 	use sp_runtime::traits::Dispatchable;
-	use xcm::latest::{Asset, Assets, InteriorLocation, Junction, Location, NetworkId, Response};
+	use xcm::latest::{
+		Asset, AssetId, Assets, InteriorLocation, Junction, Junctions, Location, NetworkId,
+		Response, WeightLimit,
+	};
 
 	#[pallet::config]
 	pub trait Config<I: 'static = ()>: frame_system::Config + crate::Config {
@@ -104,6 +107,13 @@ pub mod pallet {
 				crate_version: <frame_system::Pallet<Self> as frame_support::traits::PalletInfoAccess>::crate_version(),
 			}
 		}
+
+		/// The worst case buy execution weight limit and
+		/// asset to trigger the Trader::buy_execution in the XCM executor
+		/// By default returns ((AssetId(Here.into()), 100_000_000u128), Unlimited)
+		fn worst_case_buy_execution() -> Result<(Asset, WeightLimit), BenchmarkError> {
+			Ok(((AssetId(Junctions::Here.into()), 100_000_000u128).into(), WeightLimit::Unlimited))
+		}
 	}
 
 	#[pallet::pallet]

prdoc/pr_7944.prdoc

@@ -0,0 +1,11 @@
+title: Allow to set a worst case buy execution fee asset and weight
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Allows to set a worst case for the `BuyExecution` XCM instruction
+      benchmark. Currently the benchmark assumes best case scenario (i.e.)
+      the case where does not even need to go into the Trader. This PR allows
+      developers to set the worst-case scenario as they wish.
+crates:
+  - name: pallet-xcm-benchmarks