Prepare for asynchronous transaction validation in tx pool (#3650)

* async txpool API

* Update core/rpc/src/author/mod.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update core/transaction-pool/graph/src/pool.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Pool -> Pool + ValidatedPool

* removed lost block_on when importing xt from network

* fix grumbles

* alias for future::Executor in rpc

* removed executor from Author RPCs

* Pool + SharedValidatedPool -> Pool

* fix compilation after merge

* another fix

* another fix

substrate/core/rpc/api/src/author/error.rs

@@ -22,6 +22,9 @@ use jsonrpc_core as rpc;
 /// Author RPC Result type.
 pub type Result<T> = std::result::Result<T, Error>;
 
+/// Author RPC future Result type.
+pub type FutureResult<T> = Box<dyn rpc::futures::Future<Item = T, Error = Error> + Send>;
+
 /// Author RPC errors.
 #[derive(Debug, derive_more::Display, derive_more::From)]
 pub enum Error {

substrate/core/rpc/api/src/author/mod.rs

@@ -24,7 +24,7 @@ use jsonrpc_pubsub::{typed::Subscriber, SubscriptionId};
 use primitives::{
 	Bytes
 };
-use self::error::Result;
+use self::error::{FutureResult, Result};
 use txpool::watcher::Status;
 
 pub use self::gen_client::Client as AuthorClient;
@@ -37,7 +37,7 @@ pub trait AuthorApi<Hash, BlockHash> {
 
 	/// Submit hex-encoded extrinsic for inclusion in block.
 	#[rpc(name = "author_submitExtrinsic")]
-	fn submit_extrinsic(&self, extrinsic: Bytes) -> Result<Hash>;
+	fn submit_extrinsic(&self, extrinsic: Bytes) -> FutureResult<Hash>;
 
 	/// Insert a key into the keystore.
 	#[rpc(name = "author_insertKey")]

substrate/core/rpc/api/src/lib.rs

@@ -25,7 +25,7 @@ mod helpers;
 mod subscriptions;
 
 pub use jsonrpc_core::IoHandlerExtension as RpcExtension;
-pub use subscriptions::Subscriptions;
+pub use subscriptions::{Subscriptions, TaskExecutor};
 pub use helpers::Receiver;
 
 pub mod author;

substrate/core/rpc/api/src/subscriptions.rs

@@ -25,6 +25,9 @@ use jsonrpc_core::futures::{Future, future};
 
 type Id = u64;
 
+/// Alias for a an implementation of `futures::future::Executor`.
+pub type TaskExecutor = Arc<dyn future::Executor<Box<dyn Future<Item = (), Error = ()> + Send>> + Send + Sync>;
+
 /// Generate unique ids for subscriptions.
 #[derive(Clone, Debug)]
 pub struct IdProvider {
@@ -53,12 +56,12 @@ impl IdProvider {
 pub struct Subscriptions {
 	next_id: IdProvider,
 	active_subscriptions: Arc<Mutex<HashMap<Id, oneshot::Sender<()>>>>,
-	executor: Arc<dyn future::Executor<Box<dyn Future<Item = (), Error = ()> + Send>> + Send + Sync>,
+	executor: TaskExecutor,
 }
 
 impl Subscriptions {
 	/// Creates new `Subscriptions` object.
-	pub fn new(executor: Arc<dyn future::Executor<Box<dyn Future<Item = (), Error = ()> + Send>> + Send + Sync>) -> Self {
+	pub fn new(executor: TaskExecutor) -> Self {
 		Subscriptions {
 			next_id: Default::default(),
 			active_subscriptions: Default::default(),