Allow Sufficient Assets for XCM Fee Payment on Statemint #1884

parachains/common/src/xcm_config.rs

@@ -64,7 +64,7 @@ impl ShouldExecute for DenyReserveTransferToRelayChain {
 			message.0.iter().any(|inst| matches!(inst, ReserveAssetDeposited { .. }))
 		{
 			log::warn!(
-				target: "xcm::barrier",
+				target: "xcm::barriers",
 				"Unexpected ReserveAssetDeposited from the Relay Chain",
 			);
 		}

parachains/runtimes/assets/statemine/tests/tests.rs

@@ -302,3 +302,70 @@ fn test_that_buying_ed_refund_does_not_refund() {
 			assert_eq!(Assets::total_supply(1), ExistentialDeposit::get());
 		});
 }
+
+#[test]
+fn test_asset_xcm_trader_not_possible_for_non_sufficient_assets() {
+	ExtBuilder::<Runtime>::default()
+		.with_collators(vec![AccountId::from(ALICE)])
+		.with_session_keys(vec![(
+			AccountId::from(ALICE),
+			AccountId::from(ALICE),
+			SessionKeys { aura: AuraId::from(sp_core::sr25519::Public::from_raw(ALICE)) },
+		)])
+		.build()
+		.execute_with(|| {
+			// Create a non-sufficient asset
+			// We set existential deposit to be identical to the one for Balances first
+			assert_ok!(Assets::force_create(
+				RuntimeHelper::<Runtime>::root_origin(),
+				1,
+				AccountId::from(ALICE).into(),
+				false,
+				ExistentialDeposit::get()
+			));
+
+			// We first mint enough asset for the account to exist for assets
+			assert_ok!(Assets::mint(
+				RuntimeHelper::<Runtime>::origin_of(AccountId::from(ALICE)),
+				1,
+				AccountId::from(ALICE).into(),
+				ExistentialDeposit::get()
+			));
+
+			let mut trader = <XcmConfig as xcm_executor::Config>::Trader::new();
+
+			// Set Alice as block author, who will receive fees
+			RuntimeHelper::<Runtime>::run_to_block(2, Some(AccountId::from(ALICE)));
+
+			// We are going to buy 4e9 weight
+			let bought = 4_000_000_000u64;
+
+			// lets calculate amount needed
+			let amount_needed = WeightToFee::weight_to_fee(&Weight::from_ref_time(bought));
+
+			let asset_multilocation = MultiLocation::new(
+				0,
+				X2(
+					PalletInstance(
+						<Runtime as frame_system::Config>::PalletInfo::index::<Assets>().unwrap()
+							as u8,
+					),
+					GeneralIndex(1),
+				),
+			);
+
+			let asset: MultiAsset = (asset_multilocation, amount_needed).into();
+
+			// Make sure again buy_weight does return an error
+			assert_noop!(trader.buy_weight(bought, asset.into()), XcmError::TooExpensive);
+
+			// Drop trader
+			drop(trader);
+
+			// Make sure author(Alice) has NOT received the amount
+			assert_eq!(Assets::balance(1, AccountId::from(ALICE)), ExistentialDeposit::get());
+
+			// We also need to ensure the total supply NOT increased
+			assert_eq!(Assets::total_supply(1), ExistentialDeposit::get());
+		});
+}

parachains/runtimes/assets/statemint/src/xcm_config.rs

@@ -24,9 +24,12 @@ use frame_support::{
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
 	impls::ToStakingPot,
-	xcm_config::{DenyReserveTransferToRelayChain, DenyThenTry},
+	xcm_config::{
+		AssetFeeAsExistentialDepositMultiplier, DenyReserveTransferToRelayChain, DenyThenTry,
+	},
 };
 use polkadot_parachain::primitives::Sibling;
+use sp_runtime::traits::ConvertInto;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowKnownQueryResponses, AllowSubscriptionsFrom,
@@ -172,8 +175,29 @@ impl xcm_executor::Config for XcmConfig {
 		RuntimeCall,
 		MaxInstructions,
 	>;
-	type Trader =
-		UsingComponents<WeightToFee, DotLocation, AccountId, Balances, ToStakingPot<Runtime>>;
+	type Trader = (
+		UsingComponents<WeightToFee, DotLocation, AccountId, Balances, ToStakingPot<Runtime>>,
+		cumulus_primitives_utility::TakeFirstAssetTrader<
+			AccountId,
+			AssetFeeAsExistentialDepositMultiplier<
+				Runtime,
+				WeightToFee,
+				pallet_assets::BalanceToAssetBalance<Balances, Runtime, ConvertInto>,
+			>,
+			ConvertedConcreteAssetId<
+				AssetId,
+				Balance,
+				AsPrefixedGeneralIndex<AssetsPalletLocation, AssetId, JustTry>,
+				JustTry,
+			>,
+			Assets,
+			cumulus_primitives_utility::XcmFeesTo32ByteAccount<
+				FungiblesTransactor,
+				AccountId,
+				XcmAssetFeesReceiver,
+			>,
+		>,
+	);
 	type ResponseHandler = PolkadotXcm;
 	type AssetTrap = PolkadotXcm;
 	type AssetClaims = PolkadotXcm;