Snowbridge Inbound Queue V2 relayer tip payout fix

bridges/snowbridge/pallets/inbound-queue-v2/src/lib.rs

@@ -258,12 +258,10 @@ pub mod pallet {
 				})?;
 
 			// Pay relayer reward
-			if !relayer_fee.is_zero() {
-				T::RewardPayment::register_reward(
-					&relayer,
-					T::DefaultRewardKind::get(),
-					relayer_fee,
-				);
+			let tip = Tips::<T>::take(nonce).unwrap_or_default();
+			let total_tip = relayer_fee.saturating_add(tip);
+			if total_tip > 0 {
+				T::RewardPayment::register_reward(&relayer, T::DefaultRewardKind::get(), total_tip);
 			}
 
 			Self::deposit_event(Event::MessageReceived { nonce, message_id });

bridges/snowbridge/pallets/inbound-queue-v2/src/test.rs

@@ -7,7 +7,7 @@ use codec::Encode;
 use frame_support::{assert_noop, assert_ok};
 use snowbridge_inbound_queue_primitives::{v2::XcmPayload, EventProof, Proof};
 use snowbridge_test_utils::{
-	mock_rewards::RegisteredRewardsCount,
+	mock_rewards::{RegisteredRewardAmount, RegisteredRewardsCount},
 	mock_xcm::{set_charge_fees_override, set_sender_override},
 };
 use sp_keyring::sr25519::Keyring;
@@ -389,3 +389,141 @@ fn test_add_tip_amount_zero() {
 		assert_eq!(Tips::<Test>::get(nonce), None);
 	});
 }
+
+#[test]
+fn inbound_tip_is_paid_out_to_relayer() {
+	new_tester().execute_with(|| {
+		let nonce: u64 = 77;
+		let tip: u128 = 12_345;
+		let relayer_fee: u128 = 2_000;
+
+		// Add tip for nonce before message is processed
+		assert_ok!(InboundQueue::add_tip(nonce, tip));
+		assert_eq!(Tips::<Test>::get(nonce), Some(tip));
+
+		// Process inbound message with relayer_fee
+		let relayer: AccountId = Keyring::Bob.into();
+		assert_ok!(InboundQueue::process_message(
+			relayer,
+			Message {
+				nonce,
+				assets: vec![],
+				xcm: XcmPayload::Raw(vec![]),
+				claimer: None,
+				execution_fee: 1_000_000_000,
+				relayer_fee,
+				gateway: mock::GatewayAddress::get(),
+				origin: H160::random(),
+				value: 3_000_000_000,
+			},
+		));
+
+		// Reward should be registered from relayer_fee + tip
+		assert_eq!(
+			RegisteredRewardsCount::get(),
+			1,
+			"Reward should be registered from relayer_fee + tip"
+		);
+
+		// Check the actual reward amount paid out (should be relayer_fee + tip)
+		assert_eq!(
+			RegisteredRewardAmount::get(),
+			relayer_fee + tip,
+			"Reward amount should equal relayer_fee + tip"
+		);
+
+		// Tip should be consumed from storage
+		assert_eq!(Tips::<Test>::get(nonce), None);
+	});
+}
+
+#[test]
+fn relayer_fee_paid_out_when_no_tip_exists() {
+	new_tester().execute_with(|| {
+		let nonce: u64 = 88;
+		let relayer_fee: u128 = 5_000;
+
+		// Ensure no tip exists for this nonce
+		assert_eq!(Tips::<Test>::get(nonce), None);
+
+		// Process inbound message with relayer_fee but no tip
+		let relayer: AccountId = Keyring::Bob.into();
+		assert_ok!(InboundQueue::process_message(
+			relayer,
+			Message {
+				nonce,
+				assets: vec![],
+				xcm: XcmPayload::Raw(vec![]),
+				claimer: None,
+				execution_fee: 1_000_000_000,
+				relayer_fee,
+				gateway: mock::GatewayAddress::get(),
+				origin: H160::random(),
+				value: 3_000_000_000,
+			},
+		));
+
+		// Relayer fee should be paid out even without tip
+		assert_eq!(
+			RegisteredRewardsCount::get(),
+			1,
+			"Relayer fee should be paid out even when no tip exists"
+		);
+
+		// Check the actual reward amount paid out
+		assert_eq!(
+			RegisteredRewardAmount::get(),
+			relayer_fee,
+			"Reward amount should equal relayer_fee when no tip exists"
+		);
+
+		// Confirm no tip storage was affected
+		assert_eq!(Tips::<Test>::get(nonce), None);
+	});
+}
+
+#[test]
+fn tip_paid_out_when_no_relayer_fee() {
+	new_tester().execute_with(|| {
+		let nonce: u64 = 99;
+		let tip: u128 = 8_500;
+
+		// Add tip for nonce before message is processed
+		assert_ok!(InboundQueue::add_tip(nonce, tip));
+		assert_eq!(Tips::<Test>::get(nonce), Some(tip));
+
+		// Process inbound message with zero relayer_fee but with tip
+		let relayer: AccountId = Keyring::Bob.into();
+		assert_ok!(InboundQueue::process_message(
+			relayer,
+			Message {
+				nonce,
+				assets: vec![],
+				xcm: XcmPayload::Raw(vec![]),
+				claimer: None,
+				execution_fee: 1_000_000_000,
+				relayer_fee: 0,
+				gateway: mock::GatewayAddress::get(),
+				origin: H160::random(),
+				value: 3_000_000_000,
+			},
+		));
+
+		// Tip should be paid out even without relayer fee
+		assert_eq!(
+			RegisteredRewardsCount::get(),
+			1,
+			"Tip should be paid out even when relayer_fee is 0"
+		);
+
+		// Check the actual reward amount paid out (should be just the tip)
+		assert_eq!(
+			RegisteredRewardAmount::get(),
+			tip,
+			"Reward amount should equal tip when relayer_fee is 0"
+		);
+
+		// Tip should be consumed from storage
+		assert_eq!(Tips::<Test>::get(nonce), None);
+	});
+}

bridges/snowbridge/test-utils/src/mock_rewards.rs

@@ -50,6 +50,7 @@ impl From<BridgeReward> for RewardsAccountParams<u64> {
 
 parameter_types! {
 	pub static RegisteredRewardsCount: u128 = 0;
+	pub static RegisteredRewardAmount: u128 = 0;
 }
 
 pub struct MockRewardLedger;
@@ -58,8 +59,9 @@ impl RewardLedger<sp_runtime::AccountId32, BridgeReward, u128> for MockRewardLed
 	fn register_reward(
 		_relayer: &sp_runtime::AccountId32,
 		_reward: BridgeReward,
-		_reward_balance: u128,
+		reward_balance: u128,
 	) {
 		RegisteredRewardsCount::set(RegisteredRewardsCount::get().saturating_add(1));
+		RegisteredRewardAmount::set(reward_balance);
 	}
 }

prdoc/pr_9746.prdoc

@@ -0,0 +1,13 @@
+title: Snowbridge Inbound Queue V2 relayer tip payout fix
+
+doc:
+- audience: Runtime Dev
+  description: |
+    Fixes a bug where relayer tips were not properly paid out, causing the tips to be lost since it had already been
+    burnt.
+
+crates:
+- name: snowbridge-pallet-inbound-queue-v2
+  bump: patch
+- name: snowbridge-test-utils
+  bump: minor