chore(xcm-executor): test that leftover fees are also trapped

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

@@ -582,6 +582,11 @@ impl<Config: config::Config> XcmExecutor<Config> {
 		self.process(xcm)
 	}
 
+	#[cfg(any(test, feature = "runtime-benchmarks"))]
+	pub fn bench_post_process(self, xcm_weight: Weight) -> Outcome {
+		self.post_process(xcm_weight)
+	}
+
 	fn process(&mut self, xcm: Xcm<Config::RuntimeCall>) -> Result<(), ExecutorError> {
 		tracing::trace!(
 			target: "xcm::process",

polkadot/xcm/xcm-executor/src/tests/mock.rs

@@ -38,11 +38,12 @@ use crate::{
 pub fn instantiate_executor(
 	origin: impl Into<Location>,
 	message: Xcm<<XcmConfig as Config>::RuntimeCall>,
-) -> XcmExecutor<XcmConfig> {
+) -> (XcmExecutor<XcmConfig>, Weight) {
 	let mut vm =
 		XcmExecutor::<XcmConfig>::new(origin, message.using_encoded(sp_io::hashing::blake2_256));
-	vm.message_weight = XcmExecutor::<XcmConfig>::prepare(message.clone()).unwrap().weight_of();
-	vm
+	let weight = XcmExecutor::<XcmConfig>::prepare(message.clone()).unwrap().weight_of();
+	vm.message_weight = weight;
+	(vm, weight)
 }
 
 parameter_types! {
@@ -200,15 +201,15 @@ impl WeightTrader for TestTrader {
 }
 
 /// Account where all dropped assets are deposited.
-pub const VOID_ACCOUNT: [u8; 32] = [255; 32];
+pub const TRAPPED_ASSETS: [u8; 32] = [255; 32];
 
-/// Test asset trap that moves all dropped assets to the `VOID_ACCOUNT` account.
+/// Test asset trap that moves all dropped assets to the `TRAPPED_ASSETS` account.
 pub struct TestAssetTrap;
 impl DropAssets for TestAssetTrap {
 	fn drop_assets(_origin: &Location, assets: AssetsInHolding, _context: &XcmContext) -> Weight {
 		ASSETS.with(|a| {
 			a.borrow_mut()
-				.entry(VOID_ACCOUNT.into())
+				.entry(TRAPPED_ASSETS.into())
 				.or_insert(AssetsInHolding::new())
 				.subsume_assets(assets)
 		});

polkadot/xcm/xcm-executor/src/tests/pay_fees.rs

@@ -44,7 +44,7 @@ fn works_for_execution_fees() {
 		.deposit_asset(All, RECIPIENT.clone())
 		.build();
 
-	let mut vm = instantiate_executor(SENDER, xcm.clone());
+	let (mut vm, weight) = instantiate_executor(SENDER, xcm.clone());
 
 	// Program runs successfully.
 	assert!(vm.bench_process(xcm).is_ok());
@@ -57,6 +57,10 @@ fn works_for_execution_fees() {
 	// The recipient received all the assets in the holding register, so `100` that
 	// were withdrawn, minus the `10` that were destinated for fee payment.
 	assert_eq!(asset_list(RECIPIENT), [(Here, 90u128).into()]);
+
+	// Leftover fees get trapped.
+	assert!(vm.bench_post_process(weight).ensure_complete().is_ok());
+	assert_eq!(asset_list(TRAPPED_ASSETS), [(Here, 6u128).into()])
 }
 
 // This tests the new functionality provided by `PayFees`, being able to pay for
@@ -82,7 +86,7 @@ fn works_for_delivery_fees() {
 		.deposit_asset(All, RECIPIENT.clone())
 		.build();
 
-	let mut vm = instantiate_executor(SENDER.clone(), xcm.clone());
+	let (mut vm, _) = instantiate_executor(SENDER.clone(), xcm.clone());
 
 	// Program runs successfully.
 	assert!(vm.bench_process(xcm).is_ok());
@@ -135,7 +139,7 @@ fn buy_execution_works_as_before() {
 		.deposit_asset(All, RECIPIENT.clone())
 		.build();
 
-	let mut vm = instantiate_executor(SENDER, xcm.clone());
+	let (mut vm, _) = instantiate_executor(SENDER, xcm.clone());
 
 	// Program runs successfully.
 	assert!(vm.bench_process(xcm).is_ok());
@@ -165,7 +169,7 @@ fn fees_can_be_refunded() {
 		.deposit_asset(All, SENDER.clone())
 		.build();
 
-	let mut vm = instantiate_executor(SENDER.clone(), xcm.clone());
+	let (mut vm, _) = instantiate_executor(SENDER.clone(), xcm.clone());
 
 	// Program runs successfully.
 	assert!(vm.bench_process(xcm).is_ok());
@@ -197,7 +201,7 @@ fn putting_all_assets_in_pay_fees() {
 		.deposit_asset(All, RECIPIENT.clone())
 		.build();
 
-	let mut vm = instantiate_executor(SENDER.clone(), xcm.clone());
+	let (mut vm, _) = instantiate_executor(SENDER.clone(), xcm.clone());
 
 	// Program runs successfully.
 	assert!(vm.bench_process(xcm).is_ok());
@@ -234,7 +238,7 @@ fn refunding_too_early() {
 		.report_error(query_response_info)
 		.build();
 
-	let mut vm = instantiate_executor(SENDER.clone(), xcm.clone());
+	let (mut vm, _) = instantiate_executor(SENDER.clone(), xcm.clone());
 
 	// Program fails to run.
 	assert!(vm.bench_process(xcm).is_err());