TransactionPool API uses async_trait (paritytech#6528)

This PR refactors `TransactionPool` API to use `async_trait`, replacing
the` Pin<Box<...>>` pattern. This should improve readability and
maintainability.

The change is not altering any functionality.

---------

Co-authored-by: GitHub Action <action@github.com>

prdoc/pr_6528.prdoc

@@ -0,0 +1,18 @@
+title: 'TransactionPool API uses async_trait'
+doc:
+- audience: Node Dev
+  description: |-
+    This PR refactors `TransactionPool` API to use `async_trait`, replacing the` Pin<Box<...>>` pattern. This should improve readability and maintainability.
+
+    The change is not altering any functionality.
+crates:
+- name: sc-rpc-spec-v2
+  bump: minor
+- name: sc-service
+  bump: minor
+- name: sc-transaction-pool-api
+  bump: major
+- name: sc-transaction-pool
+  bump: major
+- name: sc-rpc
+  bump: minor

substrate/bin/node/bench/Cargo.toml

@@ -15,6 +15,7 @@ workspace = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+async-trait = { workspace = true }
 array-bytes = { workspace = true, default-features = true }
 clap = { features = ["derive"], workspace = true }
 log = { workspace = true, default-features = true }

substrate/bin/node/bench/src/construct.rs

@@ -24,14 +24,14 @@
 //! DO NOT depend on user input). Thus transaction generation should be
 //! based on randomized data.
 
-use futures::Future;
 use std::{borrow::Cow, collections::HashMap, pin::Pin, sync::Arc};
 
+use async_trait::async_trait;
 use node_primitives::Block;
 use node_testing::bench::{BenchDb, BlockType, DatabaseType, KeyTypes};
 use sc_transaction_pool_api::{
-	ImportNotificationStream, PoolFuture, PoolStatus, ReadyTransactions, TransactionFor,
-	TransactionSource, TransactionStatusStreamFor, TxHash,
+	ImportNotificationStream, PoolStatus, ReadyTransactions, TransactionFor, TransactionSource,
+	TransactionStatusStreamFor, TxHash,
 };
 use sp_consensus::{Environment, Proposer};
 use sp_inherents::InherentDataProvider;
@@ -224,54 +224,47 @@ impl ReadyTransactions for TransactionsIterator {
 	fn report_invalid(&mut self, _tx: &Self::Item) {}
 }
 
+#[async_trait]
 impl sc_transaction_pool_api::TransactionPool for Transactions {
 	type Block = Block;
 	type Hash = node_primitives::Hash;
 	type InPoolTransaction = PoolTransaction;
 	type Error = sc_transaction_pool_api::error::Error;
 
-	/// Returns a future that imports a bunch of unverified transactions to the pool.
-	fn submit_at(
+	/// Asynchronously imports a bunch of unverified transactions to the pool.
+	async fn submit_at(
 		&self,
 		_at: Self::Hash,
 		_source: TransactionSource,
 		_xts: Vec<TransactionFor<Self>>,
-	) -> PoolFuture<Vec<Result<node_primitives::Hash, Self::Error>>, Self::Error> {
+	) -> Result<Vec<Result<node_primitives::Hash, Self::Error>>, Self::Error> {
 		unimplemented!()
 	}
 
-	/// Returns a future that imports one unverified transaction to the pool.
-	fn submit_one(
+	/// Asynchronously imports one unverified transaction to the pool.
+	async fn submit_one(
 		&self,
 		_at: Self::Hash,
 		_source: TransactionSource,
 		_xt: TransactionFor<Self>,
-	) -> PoolFuture<TxHash<Self>, Self::Error> {
+	) -> Result<TxHash<Self>, Self::Error> {
 		unimplemented!()
 	}
 
-	fn submit_and_watch(
+	async fn submit_and_watch(
 		&self,
 		_at: Self::Hash,
 		_source: TransactionSource,
 		_xt: TransactionFor<Self>,
-	) -> PoolFuture<Pin<Box<TransactionStatusStreamFor<Self>>>, Self::Error> {
+	) -> Result<Pin<Box<TransactionStatusStreamFor<Self>>>, Self::Error> {
 		unimplemented!()
 	}
 
-	fn ready_at(
+	async fn ready_at(
 		&self,
 		_at: Self::Hash,
-	) -> Pin<
-		Box<
-			dyn Future<
-					Output = Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send>,
-				> + Send,
-		>,
-	> {
-		let iter: Box<dyn ReadyTransactions<Item = Arc<PoolTransaction>> + Send> =
-			Box::new(TransactionsIterator(self.0.clone().into_iter()));
-		Box::pin(futures::future::ready(iter))
+	) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send> {
+		Box::new(TransactionsIterator(self.0.clone().into_iter()))
 	}
 
 	fn ready(&self) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send> {
@@ -306,18 +299,11 @@ impl sc_transaction_pool_api::TransactionPool for Transactions {
 		unimplemented!()
 	}
 
-	fn ready_at_with_timeout(
+	async fn ready_at_with_timeout(
 		&self,
 		_at: Self::Hash,
 		_timeout: std::time::Duration,
-	) -> Pin<
-		Box<
-			dyn Future<
-					Output = Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send>,
-				> + Send
-				+ '_,
-		>,
-	> {
+	) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send> {
 		unimplemented!()
 	}
 }

substrate/client/rpc-spec-v2/Cargo.toml

@@ -44,6 +44,7 @@ rand = { workspace = true, default-features = true }
 schnellru = { workspace = true }
 
 [dev-dependencies]
+async-trait = { workspace = true }
 jsonrpsee = { workspace = true, features = ["server", "ws-client"] }
 serde_json = { workspace = true, default-features = true }
 tokio = { features = ["macros"], workspace = true, default-features = true }

substrate/client/rpc-spec-v2/src/transaction/tests/middleware_pool.rs

@@ -16,16 +16,16 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+use async_trait::async_trait;
 use codec::Encode;
-use futures::Future;
 use sc_transaction_pool::BasicPool;
 use sc_transaction_pool_api::{
-	ImportNotificationStream, PoolFuture, PoolStatus, ReadyTransactions, TransactionFor,
-	TransactionPool, TransactionSource, TransactionStatusStreamFor, TxHash,
+	ImportNotificationStream, PoolStatus, ReadyTransactions, TransactionFor, TransactionPool,
+	TransactionSource, TransactionStatusStreamFor, TxHash,
 };
 
 use crate::hex_string;
-use futures::{FutureExt, StreamExt};
+use futures::StreamExt;
 
 use sp_runtime::traits::Block as BlockT;
 use std::{collections::HashMap, pin::Pin, sync::Arc};
@@ -77,67 +77,64 @@ impl MiddlewarePool {
 	}
 }
 
+#[async_trait]
 impl TransactionPool for MiddlewarePool {
 	type Block = <BasicPool<TestApi, Block> as TransactionPool>::Block;
 	type Hash = <BasicPool<TestApi, Block> as TransactionPool>::Hash;
 	type InPoolTransaction = <BasicPool<TestApi, Block> as TransactionPool>::InPoolTransaction;
 	type Error = <BasicPool<TestApi, Block> as TransactionPool>::Error;
 
-	fn submit_at(
+	async fn submit_at(
 		&self,
 		at: <Self::Block as BlockT>::Hash,
 		source: TransactionSource,
 		xts: Vec<TransactionFor<Self>>,
-	) -> PoolFuture<Vec<Result<TxHash<Self>, Self::Error>>, Self::Error> {
-		self.inner_pool.submit_at(at, source, xts)
+	) -> Result<Vec<Result<TxHash<Self>, Self::Error>>, Self::Error> {
+		self.inner_pool.submit_at(at, source, xts).await
 	}
 
-	fn submit_one(
+	async fn submit_one(
 		&self,
 		at: <Self::Block as BlockT>::Hash,
 		source: TransactionSource,
 		xt: TransactionFor<Self>,
-	) -> PoolFuture<TxHash<Self>, Self::Error> {
-		self.inner_pool.submit_one(at, source, xt)
+	) -> Result<TxHash<Self>, Self::Error> {
+		self.inner_pool.submit_one(at, source, xt).await
 	}
 
-	fn submit_and_watch(
+	async fn submit_and_watch(
 		&self,
 		at: <Self::Block as BlockT>::Hash,
 		source: TransactionSource,
 		xt: TransactionFor<Self>,
-	) -> PoolFuture<Pin<Box<TransactionStatusStreamFor<Self>>>, Self::Error> {
-		let pool = self.inner_pool.clone();
-		let sender = self.sender.clone();
+	) -> Result<Pin<Box<TransactionStatusStreamFor<Self>>>, Self::Error> {
 		let transaction = hex_string(&xt.encode());
+		let sender = self.sender.clone();
 
-		async move {
-			let watcher = match pool.submit_and_watch(at, source, xt).await {
-				Ok(watcher) => watcher,
-				Err(err) => {
-					let _ = sender.send(MiddlewarePoolEvent::PoolError {
-						transaction: transaction.clone(),
-						err: err.to_string(),
-					});
-					return Err(err);
-				},
-			};
-
-			let watcher = watcher.map(move |status| {
-				let sender = sender.clone();
-				let transaction = transaction.clone();
-
-				let _ = sender.send(MiddlewarePoolEvent::TransactionStatus {
-					transaction,
-					status: status.clone(),
+		let watcher = match self.inner_pool.submit_and_watch(at, source, xt).await {
+			Ok(watcher) => watcher,
+			Err(err) => {
+				let _ = sender.send(MiddlewarePoolEvent::PoolError {
+					transaction: transaction.clone(),
+					err: err.to_string(),
 				});
+				return Err(err);
+			},
+		};
+
+		let watcher = watcher.map(move |status| {
+			let sender = sender.clone();
+			let transaction = transaction.clone();
 
-				status
+			let _ = sender.send(MiddlewarePoolEvent::TransactionStatus {
+				transaction,
+				status: status.clone(),
 			});
 
-			Ok(watcher.boxed())
-		}
-		.boxed()
+			status
+		});
+
+		Ok(watcher.boxed())
 	}
 
 	fn remove_invalid(&self, hashes: &[TxHash<Self>]) -> Vec<Arc<Self::InPoolTransaction>> {
@@ -164,17 +161,11 @@ impl TransactionPool for MiddlewarePool {
 		self.inner_pool.ready_transaction(hash)
 	}
 
-	fn ready_at(
+	async fn ready_at(
 		&self,
 		at: <Self::Block as BlockT>::Hash,
-	) -> Pin<
-		Box<
-			dyn Future<
-					Output = Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send>,
-				> + Send,
-		>,
-	> {
-		self.inner_pool.ready_at(at)
+	) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send> {
+		self.inner_pool.ready_at(at).await
 	}
 
 	fn ready(&self) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send> {
@@ -185,18 +176,11 @@ impl TransactionPool for MiddlewarePool {
 		self.inner_pool.futures()
 	}
 
-	fn ready_at_with_timeout(
+	async fn ready_at_with_timeout(
 		&self,
 		at: <Self::Block as BlockT>::Hash,
 		_timeout: std::time::Duration,
-	) -> Pin<
-		Box<
-			dyn Future<
-					Output = Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send>,
-				> + Send
-				+ '_,
-		>,
-	> {
-		self.inner_pool.ready_at(at)
+	) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send> {
+		self.inner_pool.ready_at(at).await
 	}
 }

substrate/client/rpc/src/author/mod.rs

@@ -29,7 +29,6 @@ use crate::{
 };
 
 use codec::{Decode, Encode};
-use futures::TryFutureExt;
 use jsonrpsee::{core::async_trait, types::ErrorObject, Extensions, PendingSubscriptionSink};
 use sc_rpc_api::check_if_safe;
 use sc_transaction_pool_api::{
@@ -191,14 +190,16 @@ where
 			},
 		};
 
-		let submit = self.pool.submit_and_watch(best_block_hash, TX_SOURCE, dxt).map_err(|e| {
-			e.into_pool_error()
-				.map(error::Error::from)
-				.unwrap_or_else(|e| error::Error::Verification(Box::new(e)))
-		});
-
+		let pool = self.pool.clone();
 		let fut = async move {
-			let stream = match submit.await {
+			let submit =
+				pool.submit_and_watch(best_block_hash, TX_SOURCE, dxt).await.map_err(|e| {
+					e.into_pool_error()
+						.map(error::Error::from)
+						.unwrap_or_else(|e| error::Error::Verification(Box::new(e)))
+				});
+
+			let stream = match submit {
 				Ok(stream) => stream,
 				Err(err) => {
 					let _ = pending.reject(ErrorObject::from(err)).await;

substrate/client/service/src/lib.rs

@@ -528,13 +528,17 @@ where
 		};
 
 		let start = std::time::Instant::now();
-		let import_future = self.pool.submit_one(
-			self.client.info().best_hash,
-			sc_transaction_pool_api::TransactionSource::External,
-			uxt,
-		);
+		let pool = self.pool.clone();
+		let client = self.client.clone();
 		Box::pin(async move {
-			match import_future.await {
+			match pool
+				.submit_one(
+					client.info().best_hash,
+					sc_transaction_pool_api::TransactionSource::External,
+					uxt,
+				)
+				.await
+			{
 				Ok(_) => {
 					let elapsed = start.elapsed();
 					debug!(target: sc_transaction_pool::LOG_TARGET, "import transaction: {elapsed:?}");