Fix invalid batch transaction (#1957)

* fix invalid batch transaction

* RaceState is now trait

* clippy

bridges/relays/lib-substrate-relay/src/lib.rs

@@ -91,18 +91,21 @@ impl<AccountId> TaggedAccount<AccountId> {
 }
 
 /// Batch call builder.
-pub trait BatchCallBuilder<Call>: Send {
+pub trait BatchCallBuilder<Call>: Clone + Send {
 	/// Create batch call from given calls vector.
 	fn build_batch_call(&self, _calls: Vec<Call>) -> Call;
 }
 
 /// Batch call builder constructor.
-pub trait BatchCallBuilderConstructor<Call> {
+pub trait BatchCallBuilderConstructor<Call>: Clone {
+	/// Call builder, used by this constructor.
+	type CallBuilder: BatchCallBuilder<Call>;
 	/// Create a new instance of a batch call builder.
-	fn new_builder() -> Option<Box<dyn BatchCallBuilder<Call>>>;
+	fn new_builder() -> Option<Self::CallBuilder>;
 }
 
 /// Batch call builder based on `pallet-utility`.
+#[derive(Clone)]
 pub struct UtilityPalletBatchCallBuilder<C: Chain>(PhantomData<C>);
 
 impl<C: Chain> BatchCallBuilder<C::Call> for UtilityPalletBatchCallBuilder<C>
@@ -118,14 +121,25 @@ impl<C: Chain> BatchCallBuilderConstructor<C::Call> for UtilityPalletBatchCallBu
 where
 	C: ChainWithUtilityPallet,
 {
-	fn new_builder() -> Option<Box<dyn BatchCallBuilder<C::Call>>> {
-		Some(Box::new(Self(Default::default())))
+	type CallBuilder = Self;
+
+	fn new_builder() -> Option<Self::CallBuilder> {
+		Some(Self(Default::default()))
 	}
 }
 
-/// A `BatchCallBuilderConstructor` that always returns `None`.
+// A `BatchCallBuilderConstructor` that always returns `None`.
 impl<Call> BatchCallBuilderConstructor<Call> for () {
-	fn new_builder() -> Option<Box<dyn BatchCallBuilder<Call>>> {
+	type CallBuilder = ();
+	fn new_builder() -> Option<Self::CallBuilder> {
 		None
 	}
 }
+
+// Dummy `BatchCallBuilder` implementation that must never be used outside
+// of the `impl BatchCallBuilderConstructor for ()` code.
+impl<Call> BatchCallBuilder<Call> for () {
+	fn build_batch_call(&self, _calls: Vec<Call>) -> Call {
+		unreachable!("never called, because ()::new_builder() returns None; qed")
+	}
+}

bridges/relays/lib-substrate-relay/src/messages_lane.rs

@@ -111,8 +111,9 @@ pub struct MessagesRelayParams<P: SubstrateMessageLane> {
 
 /// Batch transaction that brings headers + and messages delivery/receiving confirmations to the
 /// source node.
+#[derive(Clone)]
 pub struct BatchProofTransaction<SC: Chain, TC: Chain, B: BatchCallBuilderConstructor<CallOf<SC>>> {
-	builder: Box<dyn BatchCallBuilder<CallOf<SC>>>,
+	builder: B::CallBuilder,
 	proved_header: HeaderIdOf<TC>,
 	prove_calls: Vec<CallOf<SC>>,
 
@@ -120,6 +121,16 @@ pub struct BatchProofTransaction<SC: Chain, TC: Chain, B: BatchCallBuilderConstr
 	_phantom: PhantomData<fn() -> B>,
 }
 
+impl<SC: Chain, TC: Chain, B: BatchCallBuilderConstructor<CallOf<SC>>> std::fmt::Debug
+	for BatchProofTransaction<SC, TC, B>
+{
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		fmt.debug_struct("BatchProofTransaction")
+			.field("proved_header", &self.proved_header)
+			.finish()
+	}
+}
+
 impl<SC: Chain, TC: Chain, B: BatchCallBuilderConstructor<CallOf<SC>>>
 	BatchProofTransaction<SC, TC, B>
 {

bridges/relays/messages/src/message_lane_loop.rs

@@ -111,7 +111,7 @@ pub struct NoncesSubmitArtifacts<T> {
 
 /// Batch transaction that already submit some headers and needs to be extended with
 /// messages/delivery proof before sending.
-pub trait BatchTransaction<HeaderId>: Send {
+pub trait BatchTransaction<HeaderId>: Debug + Send {
 	/// Header that was required in the original call and which is bundled within this
 	/// batch transaction.
 	fn required_header_id(&self) -> HeaderId;
@@ -121,7 +121,7 @@ pub trait BatchTransaction<HeaderId>: Send {
 #[async_trait]
 pub trait SourceClient<P: MessageLane>: RelayClient {
 	/// Type of batch transaction that submits finality and message receiving proof.
-	type BatchTransaction: BatchTransaction<TargetHeaderIdOf<P>>;
+	type BatchTransaction: BatchTransaction<TargetHeaderIdOf<P>> + Clone;
 	/// Transaction tracker to track submitted transactions.
 	type TransactionTracker: TransactionTracker<HeaderId = SourceHeaderIdOf<P>>;
 
@@ -186,7 +186,7 @@ pub trait SourceClient<P: MessageLane>: RelayClient {
 #[async_trait]
 pub trait TargetClient<P: MessageLane>: RelayClient {
 	/// Type of batch transaction that submits finality and messages proof.
-	type BatchTransaction: BatchTransaction<SourceHeaderIdOf<P>>;
+	type BatchTransaction: BatchTransaction<SourceHeaderIdOf<P>> + Clone;
 	/// Transaction tracker to track submitted transactions.
 	type TransactionTracker: TransactionTracker<HeaderId = TargetHeaderIdOf<P>>;
 
@@ -1212,6 +1212,9 @@ pub(crate) mod tests {
 			original_data,
 			Arc::new(|_| {}),
 			Arc::new(move |data: &mut TestClientData| {
+				data.source_state.best_self =
+					HeaderId(data.source_state.best_self.0 + 1, data.source_state.best_self.1 + 1);
+				data.source_state.best_finalized_self = data.source_state.best_self;
 				if let Some(target_to_source_header_required) =
 					data.target_to_source_header_required.take()
 				{
@@ -1223,6 +1226,10 @@ pub(crate) mod tests {
 			}),
 			Arc::new(|_| {}),
 			Arc::new(move |data: &mut TestClientData| {
+				data.target_state.best_self =
+					HeaderId(data.target_state.best_self.0 + 1, data.target_state.best_self.1 + 1);
+				data.target_state.best_finalized_self = data.target_state.best_self;
+
 				if let Some(source_to_target_header_required) =
 					data.source_to_target_header_required.take()
 				{

bridges/relays/messages/src/message_race_delivery.rs

@@ -322,13 +322,19 @@ where
 		self.strategy.is_empty()
 	}
 
-	fn required_source_header_at_target(
+	fn required_source_header_at_target<RS: RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>>>(
 		&self,
 		current_best: &SourceHeaderIdOf<P>,
+		race_state: RS,
 	) -> Option<SourceHeaderIdOf<P>> {
+		// we have already submitted something - let's wait until it is mined
+		if race_state.nonces_submitted().is_some() {
+			return None
+		}
+
 		let has_nonces_to_deliver = !self.strategy.is_empty();
 		let header_required_for_messages_delivery =
-			self.strategy.required_source_header_at_target(current_best);
+			self.strategy.required_source_header_at_target(current_best, race_state);
 		let header_required_for_reward_confirmations_delivery = self
 			.latest_confirmed_nonces_at_source
 			.back()
@@ -381,10 +387,10 @@ where
 		self.strategy.source_nonces_updated(at_block, nonces)
 	}
 
-	fn best_target_nonces_updated(
+	fn best_target_nonces_updated<RS: RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>>>(
 		&mut self,
 		nonces: TargetClientNonces<DeliveryRaceTargetNoncesData>,
-		race_state: &mut RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::MessagesProof>,
+		race_state: &mut RS,
 	) {
 		// best target nonces must always be ge than finalized target nonces
 		let latest_nonce = nonces.latest_nonce;
@@ -396,13 +402,13 @@ where
 		)
 	}
 
-	fn finalized_target_nonces_updated(
+	fn finalized_target_nonces_updated<RS: RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>>>(
 		&mut self,
 		nonces: TargetClientNonces<DeliveryRaceTargetNoncesData>,
-		race_state: &mut RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::MessagesProof>,
+		race_state: &mut RS,
 	) {
 		if let Some(ref best_finalized_source_header_id_at_best_target) =
-			race_state.best_finalized_source_header_id_at_best_target
+			race_state.best_finalized_source_header_id_at_best_target()
 		{
 			let oldest_header_number_to_keep = best_finalized_source_header_id_at_best_target.0;
 			while self
@@ -426,13 +432,13 @@ where
 		)
 	}
 
-	async fn select_nonces_to_deliver(
+	async fn select_nonces_to_deliver<RS: RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>>>(
 		&self,
-		race_state: RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::MessagesProof>,
+		race_state: RS,
 	) -> Option<(RangeInclusive<MessageNonce>, Self::ProofParameters)> {
 		let best_target_nonce = self.strategy.best_at_target()?;
 		let best_finalized_source_header_id_at_best_target =
-			race_state.best_finalized_source_header_id_at_best_target.clone()?;
+			race_state.best_finalized_source_header_id_at_best_target()?;
 		let latest_confirmed_nonce_at_source = self
 			.latest_confirmed_nonces_at_source
 			.iter()
@@ -576,12 +582,16 @@ impl<SourceChainBalance: std::fmt::Debug> NoncesRange for MessageDetailsMap<Sour
 
 #[cfg(test)]
 mod tests {
-	use crate::message_lane_loop::{
-		tests::{
-			header_id, TestMessageLane, TestMessagesProof, TestSourceChainBalance,
-			TestSourceClient, TestSourceHeaderId, TestTargetClient, TestTargetHeaderId,
+	use crate::{
+		message_lane_loop::{
+			tests::{
+				header_id, TestMessageLane, TestMessagesBatchTransaction, TestMessagesProof,
+				TestSourceChainBalance, TestSourceClient, TestSourceHeaderId, TestTargetClient,
+				TestTargetHeaderId,
+			},
+			MessageDetails,
 		},
-		MessageDetails,
+		message_race_loop::RaceStateImpl,
 	};
 
 	use super::*;
@@ -589,7 +599,12 @@ mod tests {
 	const DEFAULT_DISPATCH_WEIGHT: Weight = Weight::from_parts(1, 0);
 	const DEFAULT_SIZE: u32 = 1;
 
-	type TestRaceState = RaceState<TestSourceHeaderId, TestTargetHeaderId, TestMessagesProof>;
+	type TestRaceState = RaceStateImpl<
+		TestSourceHeaderId,
+		TestTargetHeaderId,
+		TestMessagesProof,
+		TestMessagesBatchTransaction,
+	>;
 	type TestStrategy =
 		MessageDeliveryStrategy<TestMessageLane, TestSourceClient, TestTargetClient>;
 
@@ -617,12 +632,13 @@ mod tests {
 	}
 
 	fn prepare_strategy() -> (TestRaceState, TestStrategy) {
-		let mut race_state = RaceState {
+		let mut race_state = RaceStateImpl {
 			best_finalized_source_header_id_at_source: Some(header_id(1)),
 			best_finalized_source_header_id_at_best_target: Some(header_id(1)),
 			best_target_header_id: Some(header_id(1)),
 			best_finalized_target_header_id: Some(header_id(1)),
 			nonces_to_submit: None,
+			nonces_to_submit_batch: None,
 			nonces_submitted: None,
 		};
 
@@ -964,14 +980,17 @@ mod tests {
 		);
 		// nothing needs to be delivered now and we don't need any new headers
 		assert_eq!(strategy.select_nonces_to_deliver(state.clone()).await, None);
-		assert_eq!(strategy.required_source_header_at_target(&header_id(1)), None);
+		assert_eq!(strategy.required_source_header_at_target(&header_id(1), state.clone()), None);
 
 		// now let's generate two more nonces [24; 25] at the soruce;
 		strategy.source_nonces_updated(header_id(2), source_nonces(24..=25, 19, 0));
 		//
 		// - so now we'll need to relay source block#2 to be able to accept messages [24; 25].
 		assert_eq!(strategy.select_nonces_to_deliver(state.clone()).await, None);
-		assert_eq!(strategy.required_source_header_at_target(&header_id(1)), Some(header_id(2)));
+		assert_eq!(
+			strategy.required_source_header_at_target(&header_id(1), state.clone()),
+			Some(header_id(2))
+		);
 
 		// let's relay source block#2
 		state.best_finalized_source_header_id_at_source = Some(header_id(2));
@@ -982,7 +1001,7 @@ mod tests {
 		// and ask strategy again => still nothing to deliver, because parallel confirmations
 		// race need to be pushed further
 		assert_eq!(strategy.select_nonces_to_deliver(state.clone()).await, None);
-		assert_eq!(strategy.required_source_header_at_target(&header_id(2)), None);
+		assert_eq!(strategy.required_source_header_at_target(&header_id(2), state.clone()), None);
 
 		// let's confirm messages [20; 23]
 		strategy.source_nonces_updated(header_id(2), source_nonces(24..=25, 23, 0));
@@ -990,10 +1009,10 @@ mod tests {
 		// and ask strategy again => now we have everything required to deliver remaining
 		// [24; 25] nonces and proof of [20; 23] confirmation
 		assert_eq!(
-			strategy.select_nonces_to_deliver(state).await,
+			strategy.select_nonces_to_deliver(state.clone()).await,
 			Some(((24..=25), proof_parameters(true, 2))),
 		);
-		assert_eq!(strategy.required_source_header_at_target(&header_id(2)), None);
+		assert_eq!(strategy.required_source_header_at_target(&header_id(2), state), None);
 	}
 
 	#[async_std::test]
@@ -1025,6 +1044,7 @@ mod tests {
 	#[test]
 	#[allow(clippy::reversed_empty_ranges)]
 	fn no_source_headers_required_at_target_if_lanes_are_empty() {
+		let (state, _) = prepare_strategy();
 		let mut strategy = TestStrategy {
 			max_unrewarded_relayer_entries_at_target: 4,
 			max_unconfirmed_nonces_at_target: 4,
@@ -1053,7 +1073,7 @@ mod tests {
 			strategy.latest_confirmed_nonces_at_source,
 			VecDeque::from([(source_header_id, 0)])
 		);
-		assert_eq!(strategy.required_source_header_at_target(&source_header_id), None);
+		assert_eq!(strategy.required_source_header_at_target(&source_header_id, state), None);
 	}
 
 	#[async_std::test]

bridges/relays/messages/src/message_race_loop.rs

@@ -25,7 +25,7 @@ use crate::message_lane_loop::{BatchTransaction, ClientState, NoncesSubmitArtifa
 use async_trait::async_trait;
 use bp_messages::MessageNonce;
 use futures::{
-	future::FutureExt,
+	future::{FutureExt, TryFutureExt},
 	stream::{FusedStream, StreamExt},
 };
 use relay_utils::{
@@ -41,14 +41,14 @@ use std::{
 /// One of races within lane.
 pub trait MessageRace {
 	/// Header id of the race source.
-	type SourceHeaderId: Debug + Clone + PartialEq;
+	type SourceHeaderId: Debug + Clone + PartialEq + Send;
 	/// Header id of the race source.
-	type TargetHeaderId: Debug + Clone + PartialEq;
+	type TargetHeaderId: Debug + Clone + PartialEq + Send;
 
 	/// Message nonce used in the race.
 	type MessageNonce: Debug + Clone;
 	/// Proof that is generated and delivered in this race.
-	type Proof: Debug + Clone;
+	type Proof: Debug + Clone + Send;
 
 	/// Name of the race source.
 	fn source_name() -> String;
@@ -128,7 +128,7 @@ pub trait TargetClient<P: MessageRace> {
 	/// Type of the additional data from the target client, used by the race.
 	type TargetNoncesData: std::fmt::Debug;
 	/// Type of batch transaction that submits finality and proof to the target node.
-	type BatchTransaction: BatchTransaction<P::SourceHeaderId>;
+	type BatchTransaction: BatchTransaction<P::SourceHeaderId> + Clone;
 	/// Transaction tracker to track submitted transactions.
 	type TransactionTracker: TransactionTracker<HeaderId = P::TargetHeaderId>;
 
@@ -175,9 +175,10 @@ pub trait RaceStrategy<SourceHeaderId, TargetHeaderId, Proof>: Debug {
 	/// Should return true if nothing has to be synced.
 	fn is_empty(&self) -> bool;
 	/// Return id of source header that is required to be on target to continue synchronization.
-	fn required_source_header_at_target(
+	fn required_source_header_at_target<RS: RaceState<SourceHeaderId, TargetHeaderId>>(
 		&self,
 		current_best: &SourceHeaderId,
+		race_state: RS,
 	) -> Option<SourceHeaderId>;
 	/// Return the best nonce at source node.
 	///
@@ -196,29 +197,53 @@ pub trait RaceStrategy<SourceHeaderId, TargetHeaderId, Proof>: Debug {
 		nonces: SourceClientNonces<Self::SourceNoncesRange>,
 	);
 	/// Called when best nonces are updated at target node of the race.
-	fn best_target_nonces_updated(
+	fn best_target_nonces_updated<RS: RaceState<SourceHeaderId, TargetHeaderId>>(
 		&mut self,
 		nonces: TargetClientNonces<Self::TargetNoncesData>,
-		race_state: &mut RaceState<SourceHeaderId, TargetHeaderId, Proof>,
+		race_state: &mut RS,
 	);
 	/// Called when finalized nonces are updated at target node of the race.
-	fn finalized_target_nonces_updated(
+	fn finalized_target_nonces_updated<RS: RaceState<SourceHeaderId, TargetHeaderId>>(
 		&mut self,
 		nonces: TargetClientNonces<Self::TargetNoncesData>,
-		race_state: &mut RaceState<SourceHeaderId, TargetHeaderId, Proof>,
+		race_state: &mut RS,
 	);
 	/// Should return `Some(nonces)` if we need to deliver proof of `nonces` (and associated
 	/// data) from source to target node.
 	/// Additionally, parameters required to generate proof are returned.
-	async fn select_nonces_to_deliver(
+	async fn select_nonces_to_deliver<RS: RaceState<SourceHeaderId, TargetHeaderId>>(
 		&self,
-		race_state: RaceState<SourceHeaderId, TargetHeaderId, Proof>,
+		race_state: RS,
 	) -> Option<(RangeInclusive<MessageNonce>, Self::ProofParameters)>;
 }
 
 /// State of the race.
+pub trait RaceState<SourceHeaderId, TargetHeaderId>: Send {
+	/// Best finalized source header id at the source client.
+	fn best_finalized_source_header_id_at_source(&self) -> Option<SourceHeaderId>;
+	/// Best finalized source header id at the best block on the target
+	/// client (at the `best_finalized_source_header_id_at_best_target`).
+	fn best_finalized_source_header_id_at_best_target(&self) -> Option<SourceHeaderId>;
+	/// The best header id at the target client.
+	fn best_target_header_id(&self) -> Option<TargetHeaderId>;
+	/// Best finalized header id at the target client.
+	fn best_finalized_target_header_id(&self) -> Option<TargetHeaderId>;
+
+	/// Returns `true` if we have selected nonces to submit to the target node.
+	fn nonces_to_submit(&self) -> Option<RangeInclusive<MessageNonce>>;
+	/// Reset our nonces selection.
+	fn reset_nonces_to_submit(&mut self);
+
+	/// Returns `true` if we have submitted some nonces to the target node and are
+	/// waiting for them to appear there.
+	fn nonces_submitted(&self) -> Option<RangeInclusive<MessageNonce>>;
+	/// Reset our nonces submission.
+	fn reset_nonces_submitted(&mut self);
+}
+
+/// State of the race and prepared batch transaction (if available).
 #[derive(Debug, Clone)]
-pub struct RaceState<SourceHeaderId, TargetHeaderId, Proof> {
+pub(crate) struct RaceStateImpl<SourceHeaderId, TargetHeaderId, Proof, BatchTx> {
 	/// Best finalized source header id at the source client.
 	pub best_finalized_source_header_id_at_source: Option<SourceHeaderId>,
 	/// Best finalized source header id at the best block on the target
@@ -230,13 +255,67 @@ pub struct RaceState<SourceHeaderId, TargetHeaderId, Proof> {
 	pub best_finalized_target_header_id: Option<TargetHeaderId>,
 	/// Range of nonces that we have selected to submit.
 	pub nonces_to_submit: Option<(SourceHeaderId, RangeInclusive<MessageNonce>, Proof)>,
+	/// Batch transaction ready to include and deliver selected `nonces_to_submit` from the
+	/// `state`.
+	pub nonces_to_submit_batch: Option<BatchTx>,
 	/// Range of nonces that is currently submitted.
 	pub nonces_submitted: Option<RangeInclusive<MessageNonce>>,
 }
 
-impl<SourceHeaderId, TargetHeaderId, Proof> RaceState<SourceHeaderId, TargetHeaderId, Proof> {
-	/// Reset `nonces_submitted` to `None`.
-	fn reset_submitted(&mut self) {
+impl<SourceHeaderId, TargetHeaderId, Proof, BatchTx> Default
+	for RaceStateImpl<SourceHeaderId, TargetHeaderId, Proof, BatchTx>
+{
+	fn default() -> Self {
+		RaceStateImpl {
+			best_finalized_source_header_id_at_source: None,
+			best_finalized_source_header_id_at_best_target: None,
+			best_target_header_id: None,
+			best_finalized_target_header_id: None,
+			nonces_to_submit: None,
+			nonces_to_submit_batch: None,
+			nonces_submitted: None,
+		}
+	}
+}
+
+impl<SourceHeaderId, TargetHeaderId, Proof, BatchTx> RaceState<SourceHeaderId, TargetHeaderId>
+	for RaceStateImpl<SourceHeaderId, TargetHeaderId, Proof, BatchTx>
+where
+	SourceHeaderId: Clone + Send,
+	TargetHeaderId: Clone + Send,
+	Proof: Clone + Send,
+	BatchTx: Clone + Send,
+{
+	fn best_finalized_source_header_id_at_source(&self) -> Option<SourceHeaderId> {
+		self.best_finalized_source_header_id_at_source.clone()
+	}
+
+	fn best_finalized_source_header_id_at_best_target(&self) -> Option<SourceHeaderId> {
+		self.best_finalized_source_header_id_at_best_target.clone()
+	}
+
+	fn best_target_header_id(&self) -> Option<TargetHeaderId> {
+		self.best_target_header_id.clone()
+	}
+
+	fn best_finalized_target_header_id(&self) -> Option<TargetHeaderId> {
+		self.best_finalized_target_header_id.clone()
+	}
+
+	fn nonces_to_submit(&self) -> Option<RangeInclusive<MessageNonce>> {
+		self.nonces_to_submit.as_ref().map(|(_, nonces, _)| nonces.clone())
+	}
+
+	fn reset_nonces_to_submit(&mut self) {
+		self.nonces_to_submit = None;
+		self.nonces_to_submit_batch = None;
+	}
+
+	fn nonces_submitted(&self) -> Option<RangeInclusive<MessageNonce>> {
+		self.nonces_submitted.clone()
+	}
+
+	fn reset_nonces_submitted(&mut self) {
 		self.nonces_submitted = None;
 	}
 }
@@ -257,7 +336,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 	>,
 ) -> Result<(), FailedClient> {
 	let mut progress_context = Instant::now();
-	let mut race_state = RaceState::default();
+	let mut race_state = RaceStateImpl::default();
 
 	let mut source_retry_backoff = retry_backoff();
 	let mut source_client_is_online = true;
@@ -302,7 +381,8 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 						!= Some(&source_state.best_finalized_self);
 					if is_source_state_updated {
 						source_nonces_required = true;
-						race_state.best_finalized_source_header_id_at_source = Some(source_state.best_finalized_self);
+						race_state.best_finalized_source_header_id_at_source
+							= Some(source_state.best_finalized_self);
 					}
 				}
 			},
@@ -353,7 +433,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 				source_required_header = race_state
 					.best_finalized_source_header_id_at_best_target
 					.as_ref()
-					.and_then(|best| strategy.required_source_header_at_target(best));
+					.and_then(|best| strategy.required_source_header_at_target(best, race_state.clone()));
 			},
 			nonces = target_best_nonces => {
 				target_best_nonces_required = false;
@@ -408,10 +488,13 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 					|maybe_batch_transaction: Option<TC::BatchTransaction>| {
 						log::debug!(
 							target: "bridge",
-							"Target {} client has been asked for more {} headers. Batch tx: {:?}",
+							"Target {} client has been asked for more {} headers. Batch tx: {}",
 							P::target_name(),
 							P::source_name(),
-							maybe_batch_transaction.is_some(),
+							maybe_batch_transaction
+								.as_ref()
+								.map(|bt| format!("yes ({:?})", bt.required_header_id()))
+								.unwrap_or_else(|| "no".into()),
 						);
 
 						target_batch_transaction = maybe_batch_transaction;
@@ -425,7 +508,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 				source_client_is_online = process_future_result(
 					proof,
 					&mut source_retry_backoff,
-					|(at_block, nonces_range, proof)| {
+					|(at_block, nonces_range, proof, batch_transaction)| {
 						log::debug!(
 							target: "bridge",
 							"Received proof for nonces in range {:?} from {}",
@@ -434,6 +517,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 						);
 
 						race_state.nonces_to_submit = Some((at_block, nonces_range, proof));
+						race_state.nonces_to_submit_batch = batch_transaction;
 					},
 					&mut source_go_offline_future,
 					async_std::task::sleep,
@@ -452,8 +536,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 							P::target_name(),
 						);
 
-						target_batch_transaction = None;
-						race_state.nonces_to_submit = None;
+						race_state.reset_nonces_to_submit();
 						race_state.nonces_submitted = Some(artifacts.nonces);
 						target_tx_tracker.set(artifacts.tx_tracker.wait().fuse());
 					},
@@ -490,7 +573,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 									e,
 								);
 
-								race_state.reset_submitted();
+								race_state.reset_nonces_submitted();
 							});
 					},
 					(TrackedTransactionStatus::Lost, _) => {
@@ -503,7 +586,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 							strategy,
 						);
 
-						race_state.reset_submitted();
+						race_state.reset_nonces_submitted();
 					},
 					_ => (),
 				}
@@ -524,6 +607,12 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 			source_client_is_online = false;
 
 			// if we've started to submit batch transaction, let's prioritize it
+			//
+			// we're using `take` here, because we don't need batch transaction (i.e. some
+			// underlying finality proof) anymore for our future calls - we were unable to
+			// use it for our current state, so why would we need to keep an obsolete proof
+			// for the future?
+			let target_batch_transaction = target_batch_transaction.take();
 			let expected_race_state =
 				if let Some(ref target_batch_transaction) = target_batch_transaction {
 					// when selecting nonces for the batch transaction, we assume that the required
@@ -551,7 +640,12 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 				);
 
 				source_generate_proof.set(
-					race_source.generate_proof(at_block, nonces_range, proof_parameters).fuse(),
+					race_source
+						.generate_proof(at_block, nonces_range, proof_parameters)
+						.and_then(|(at_source_block, nonces, proof)| async {
+							Ok((at_source_block, nonces, proof, target_batch_transaction))
+						})
+						.fuse(),
 				);
 			} else if source_nonces_required && best_at_source.is_some() {
 				log::debug!(target: "bridge", "Asking {} about message nonces", P::source_name());
@@ -582,7 +676,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 					"Going to submit proof of messages in range {:?} to {} node{}",
 					nonces_range,
 					P::target_name(),
-					target_batch_transaction.as_ref().map(|tx| format!(
+					race_state.nonces_to_submit_batch.as_ref().map(|tx| format!(
 						". This transaction is batched with sending the proof for header {:?}.",
 						tx.required_header_id())
 					).unwrap_or_default(),
@@ -591,7 +685,7 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 				target_submit_proof.set(
 					race_target
 						.submit_proof(
-							target_batch_transaction.take(),
+							race_state.nonces_to_submit_batch.clone(),
 							at_block.clone(),
 							nonces_range.clone(),
 							proof.clone(),
@@ -628,21 +722,6 @@ pub async fn run<P: MessageRace, SC: SourceClient<P>, TC: TargetClient<P>>(
 	}
 }
 
-impl<SourceHeaderId, TargetHeaderId, Proof> Default
-	for RaceState<SourceHeaderId, TargetHeaderId, Proof>
-{
-	fn default() -> Self {
-		RaceState {
-			best_finalized_source_header_id_at_source: None,
-			best_finalized_source_header_id_at_best_target: None,
-			best_target_header_id: None,
-			best_finalized_target_header_id: None,
-			nonces_to_submit: None,
-			nonces_submitted: None,
-		}
-	}
-}
-
 /// Print race progress.
 fn print_race_progress<P, S>(prev_time: Instant, strategy: &S) -> Instant
 where
@@ -670,7 +749,7 @@ where
 }
 
 async fn select_nonces_to_deliver<SourceHeaderId, TargetHeaderId, Proof, Strategy>(
-	race_state: RaceState<SourceHeaderId, TargetHeaderId, Proof>,
+	race_state: impl RaceState<SourceHeaderId, TargetHeaderId>,
 	strategy: &Strategy,
 ) -> Option<(SourceHeaderId, RangeInclusive<MessageNonce>, Strategy::ProofParameters)>
 where
@@ -678,7 +757,7 @@ where
 	Strategy: RaceStrategy<SourceHeaderId, TargetHeaderId, Proof>,
 {
 	let best_finalized_source_header_id_at_best_target =
-		race_state.best_finalized_source_header_id_at_best_target.clone()?;
+		race_state.best_finalized_source_header_id_at_best_target()?;
 	strategy
 		.select_nonces_to_deliver(race_state)
 		.await
@@ -701,7 +780,7 @@ mod tests {
 
 		// target node only knows about source' BEST_AT_TARGET block
 		// source node has BEST_AT_SOURCE > BEST_AT_TARGET block
-		let mut race_state = RaceState::<_, _, ()> {
+		let mut race_state = RaceStateImpl::<_, _, (), ()> {
 			best_finalized_source_header_id_at_source: Some(HeaderId(
 				BEST_AT_SOURCE,
 				BEST_AT_SOURCE,
@@ -713,11 +792,12 @@ mod tests {
 			best_target_header_id: Some(HeaderId(0, 0)),
 			best_finalized_target_header_id: Some(HeaderId(0, 0)),
 			nonces_to_submit: None,
+			nonces_to_submit_batch: None,
 			nonces_submitted: None,
 		};
 
 		// we have some nonces to deliver and they're generated at GENERATED_AT < BEST_AT_SOURCE
-		let mut strategy = BasicStrategy::new();
+		let mut strategy = BasicStrategy::<_, _, _, _, _, ()>::new();
 		strategy.source_nonces_updated(
 			HeaderId(GENERATED_AT, GENERATED_AT),
 			SourceClientNonces { new_nonces: 0..=10, confirmed_nonce: None },

bridges/relays/messages/src/message_race_strategy.rs

@@ -106,24 +106,25 @@ impl<
 	/// at source blocks that are known to be finalized at the target node.
 	///
 	/// Returns `None` if no entries may be delivered.
-	pub fn available_source_queue_indices(
-		&self,
-		race_state: RaceState<
+	pub fn available_source_queue_indices<
+		RS: RaceState<
 			HeaderId<SourceHeaderHash, SourceHeaderNumber>,
 			HeaderId<TargetHeaderHash, TargetHeaderNumber>,
-			Proof,
 		>,
+	>(
+		&self,
+		race_state: RS,
 	) -> Option<RangeInclusive<usize>> {
 		// if we do not know best nonce at target node, we can't select anything
 		let best_target_nonce = self.best_target_nonce?;
 
 		// if we have already selected nonces that we want to submit, do nothing
-		if race_state.nonces_to_submit.is_some() {
+		if race_state.nonces_to_submit().is_some() {
 			return None
 		}
 
 		// if we already submitted some nonces, do nothing
-		if race_state.nonces_submitted.is_some() {
+		if race_state.nonces_submitted().is_some() {
 			return None
 		}
 
@@ -143,7 +144,7 @@ impl<
 		//
 		// => let's first select range of entries inside deque that are already finalized at
 		// the target client and pass this range to the selector
-		let best_header_at_target = race_state.best_finalized_source_header_id_at_best_target?;
+		let best_header_at_target = race_state.best_finalized_source_header_id_at_best_target()?;
 		let end_index = self
 			.source_queue
 			.iter()
@@ -204,9 +205,15 @@ impl<
 		self.source_queue.is_empty()
 	}
 
-	fn required_source_header_at_target(
+	fn required_source_header_at_target<
+		RS: RaceState<
+			HeaderId<SourceHeaderHash, SourceHeaderNumber>,
+			HeaderId<TargetHeaderHash, TargetHeaderNumber>,
+		>,
+	>(
 		&self,
 		current_best: &HeaderId<SourceHeaderHash, SourceHeaderNumber>,
+		_race_state: RS,
 	) -> Option<HeaderId<SourceHeaderHash, SourceHeaderNumber>> {
 		self.source_queue
 			.back()
@@ -247,46 +254,46 @@ impl<
 		)
 	}
 
-	fn best_target_nonces_updated(
-		&mut self,
-		nonces: TargetClientNonces<()>,
-		race_state: &mut RaceState<
+	fn best_target_nonces_updated<
+		RS: RaceState<
 			HeaderId<SourceHeaderHash, SourceHeaderNumber>,
 			HeaderId<TargetHeaderHash, TargetHeaderNumber>,
-			Proof,
 		>,
+	>(
+		&mut self,
+		nonces: TargetClientNonces<()>,
+		race_state: &mut RS,
 	) {
 		let nonce = nonces.latest_nonce;
 
 		let need_to_select_new_nonces = race_state
-			.nonces_to_submit
-			.as_ref()
-			.map(|(_, nonces, _)| *nonces.end() <= nonce)
+			.nonces_to_submit()
+			.map(|nonces| *nonces.end() <= nonce)
 			.unwrap_or(false);
 		if need_to_select_new_nonces {
-			race_state.nonces_to_submit = None;
+			race_state.reset_nonces_to_submit();
 		}
 
 		let need_new_nonces_to_submit = race_state
-			.nonces_submitted
-			.as_ref()
+			.nonces_submitted()
 			.map(|nonces| *nonces.end() <= nonce)
 			.unwrap_or(false);
 		if need_new_nonces_to_submit {
-			race_state.nonces_submitted = None;
+			race_state.reset_nonces_submitted();
 		}
 
 		self.best_target_nonce = Some(nonce);
 	}
 
-	fn finalized_target_nonces_updated(
-		&mut self,
-		nonces: TargetClientNonces<()>,
-		_race_state: &mut RaceState<
+	fn finalized_target_nonces_updated<
+		RS: RaceState<
 			HeaderId<SourceHeaderHash, SourceHeaderNumber>,
 			HeaderId<TargetHeaderHash, TargetHeaderNumber>,
-			Proof,
 		>,
+	>(
+		&mut self,
+		nonces: TargetClientNonces<()>,
+		_race_state: &mut RS,
 	) {
 		self.remove_le_nonces_from_source_queue(nonces.latest_nonce);
 		self.best_target_nonce = Some(std::cmp::max(
@@ -295,13 +302,14 @@ impl<
 		));
 	}
 
-	async fn select_nonces_to_deliver(
-		&self,
-		race_state: RaceState<
+	async fn select_nonces_to_deliver<
+		RS: RaceState<
 			HeaderId<SourceHeaderHash, SourceHeaderNumber>,
 			HeaderId<TargetHeaderHash, TargetHeaderNumber>,
-			Proof,
 		>,
+	>(
+		&self,
+		race_state: RS,
 	) -> Option<(RangeInclusive<MessageNonce>, Self::ProofParameters)> {
 		let available_indices = self.available_source_queue_indices(race_state)?;
 		let range_begin = std::cmp::max(
@@ -317,15 +325,23 @@ impl<
 mod tests {
 	use super::*;
 	use crate::{
-		message_lane::MessageLane,
+		message_lane::{MessageLane, SourceHeaderIdOf, TargetHeaderIdOf},
 		message_lane_loop::tests::{
 			header_id, TestMessageLane, TestMessagesProof, TestSourceHeaderHash,
 			TestSourceHeaderNumber,
 		},
+		message_race_loop::RaceStateImpl,
 	};
 
 	type SourceNoncesRange = RangeInclusive<MessageNonce>;
 
+	type TestRaceStateImpl = RaceStateImpl<
+		SourceHeaderIdOf<TestMessageLane>,
+		TargetHeaderIdOf<TestMessageLane>,
+		TestMessagesProof,
+		(),
+	>;
+
 	type BasicStrategy<P> = super::BasicStrategy<
 		<P as MessageLane>::SourceHeaderNumber,
 		<P as MessageLane>::SourceHeaderHash,
@@ -357,7 +373,7 @@ mod tests {
 		assert_eq!(strategy.best_at_source(), None);
 		strategy.source_nonces_updated(header_id(1), source_nonces(1..=5));
 		assert_eq!(strategy.best_at_source(), None);
-		strategy.best_target_nonces_updated(target_nonces(10), &mut Default::default());
+		strategy.best_target_nonces_updated(target_nonces(10), &mut TestRaceStateImpl::default());
 		assert_eq!(strategy.source_queue, vec![(header_id(1), 1..=5)]);
 		assert_eq!(strategy.best_at_source(), Some(10));
 	}
@@ -365,7 +381,7 @@ mod tests {
 	#[test]
 	fn source_nonce_is_never_lower_than_known_target_nonce() {
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
-		strategy.best_target_nonces_updated(target_nonces(10), &mut Default::default());
+		strategy.best_target_nonces_updated(target_nonces(10), &mut TestRaceStateImpl::default());
 		strategy.source_nonces_updated(header_id(1), source_nonces(1..=5));
 		assert_eq!(strategy.source_queue, vec![]);
 	}
@@ -386,15 +402,17 @@ mod tests {
 		strategy.source_nonces_updated(header_id(2), source_nonces(6..=10));
 		strategy.source_nonces_updated(header_id(3), source_nonces(11..=15));
 		strategy.source_nonces_updated(header_id(4), source_nonces(16..=20));
-		strategy.finalized_target_nonces_updated(target_nonces(15), &mut Default::default());
+		strategy
+			.finalized_target_nonces_updated(target_nonces(15), &mut TestRaceStateImpl::default());
 		assert_eq!(strategy.source_queue, vec![(header_id(4), 16..=20)]);
-		strategy.finalized_target_nonces_updated(target_nonces(17), &mut Default::default());
+		strategy
+			.finalized_target_nonces_updated(target_nonces(17), &mut TestRaceStateImpl::default());
 		assert_eq!(strategy.source_queue, vec![(header_id(4), 18..=20)]);
 	}
 
 	#[test]
 	fn selected_nonces_are_dropped_on_target_nonce_update() {
-		let mut state = RaceState::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		state.nonces_to_submit = Some((header_id(1), 5..=10, (5..=10, None)));
 		strategy.best_target_nonces_updated(target_nonces(7), &mut state);
@@ -405,7 +423,7 @@ mod tests {
 
 	#[test]
 	fn submitted_nonces_are_dropped_on_target_nonce_update() {
-		let mut state = RaceState::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		state.nonces_submitted = Some(5..=10);
 		strategy.best_target_nonces_updated(target_nonces(7), &mut state);
@@ -416,7 +434,7 @@ mod tests {
 
 	#[async_std::test]
 	async fn nothing_is_selected_if_something_is_already_selected() {
-		let mut state = RaceState::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		state.nonces_to_submit = Some((header_id(1), 1..=10, (1..=10, None)));
 		strategy.best_target_nonces_updated(target_nonces(0), &mut state);
@@ -426,7 +444,7 @@ mod tests {
 
 	#[async_std::test]
 	async fn nothing_is_selected_if_something_is_already_submitted() {
-		let mut state = RaceState::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		state.nonces_submitted = Some(1..=10);
 		strategy.best_target_nonces_updated(target_nonces(0), &mut state);
@@ -436,7 +454,7 @@ mod tests {
 
 	#[async_std::test]
 	async fn select_nonces_to_deliver_works() {
-		let mut state = RaceState::<_, _, TestMessagesProof>::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		strategy.best_target_nonces_updated(target_nonces(0), &mut state);
 		strategy.source_nonces_updated(header_id(1), source_nonces(1..=1));
@@ -457,7 +475,7 @@ mod tests {
 
 	#[test]
 	fn available_source_queue_indices_works() {
-		let mut state = RaceState::<_, _, TestMessagesProof>::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		strategy.best_target_nonces_updated(target_nonces(0), &mut state);
 		strategy.source_nonces_updated(header_id(1), source_nonces(1..=3));
@@ -482,7 +500,7 @@ mod tests {
 
 	#[test]
 	fn remove_le_nonces_from_source_queue_works() {
-		let mut state = RaceState::<_, _, TestMessagesProof>::default();
+		let mut state = TestRaceStateImpl::default();
 		let mut strategy = BasicStrategy::<TestMessageLane>::new();
 		strategy.best_target_nonces_updated(target_nonces(0), &mut state);
 		strategy.source_nonces_updated(header_id(1), source_nonces(1..=3));
@@ -518,12 +536,13 @@ mod tests {
 		let target_header_1 = header_id(1);
 
 		// we start in perfec sync state - all headers are synced and finalized on both ends
-		let mut state = RaceState::<_, _, TestMessagesProof> {
+		let mut state = TestRaceStateImpl {
 			best_finalized_source_header_id_at_source: Some(source_header_1),
 			best_finalized_source_header_id_at_best_target: Some(source_header_1),
 			best_target_header_id: Some(target_header_1),
 			best_finalized_target_header_id: Some(target_header_1),
 			nonces_to_submit: None,
+			nonces_to_submit_batch: None,
 			nonces_submitted: None,
 		};