Custom RPC for Merkle Mountain Range pallet (#8137)

* Add MMR custom RPC.

* Change RuntimeApi to avoid hardcoding leaf type.

* Properly implement the new RuntimeAPI and wire up RPC.

* Extract Offchain DB as separate execution extension.

* Enable offchain DB access for offchain calls.

* Fix offchain_election tests.

* Skip block initialisation for proof generation.

* Fix integration test setup.

* Fix offchain tests. Not sure how I missed them earlier 🤷.

* Fix long line.

* One more test missing.

* Update mock for multi-phase.

* Address review grumbbles.

* Address review grumbles.

* Fix line width of a comment

substrate/client/offchain/src/lib.rs

@@ -46,13 +46,13 @@ use sp_api::{ApiExt, ProvideRuntimeApi};
 use futures::future::Future;
 use log::{debug, warn};
 use sc_network::{ExHashT, NetworkService, NetworkStateInfo, PeerId};
-use sp_core::{offchain::{self, OffchainStorage}, ExecutionContext, traits::SpawnNamed};
+use sp_core::{offchain, ExecutionContext, traits::SpawnNamed};
 use sp_runtime::{generic::BlockId, traits::{self, Header}};
 use futures::{prelude::*, future::ready};
 
 mod api;
-use api::SharedClient;
 
+pub use api::Db as OffchainDb;
 pub use sp_offchain::{OffchainWorkerApi, STORAGE_PREFIX};
 
 /// NetworkProvider provides [`OffchainWorkers`] with all necessary hooks into the
@@ -80,21 +80,19 @@ where
 }
 
 /// An offchain workers manager.
-pub struct OffchainWorkers<Client, Storage, Block: traits::Block> {
+pub struct OffchainWorkers<Client, Block: traits::Block> {
 	client: Arc<Client>,
-	db: Storage,
 	_block: PhantomData<Block>,
 	thread_pool: Mutex<ThreadPool>,
-	shared_client: SharedClient,
+	shared_client: api::SharedClient,
 }
 
-impl<Client, Storage, Block: traits::Block> OffchainWorkers<Client, Storage, Block> {
+impl<Client, Block: traits::Block> OffchainWorkers<Client, Block> {
 	/// Creates new `OffchainWorkers`.
-	pub fn new(client: Arc<Client>, db: Storage) -> Self {
-		let shared_client = SharedClient::new();
+	pub fn new(client: Arc<Client>) -> Self {
+		let shared_client = api::SharedClient::new();
 		Self {
 			client,
-			db,
 			_block: PhantomData,
 			thread_pool: Mutex::new(ThreadPool::new(num_cpus::get())),
 			shared_client,
@@ -102,9 +100,8 @@ impl<Client, Storage, Block: traits::Block> OffchainWorkers<Client, Storage, Blo
 	}
 }
 
-impl<Client, Storage, Block: traits::Block> fmt::Debug for OffchainWorkers<
+impl<Client, Block: traits::Block> fmt::Debug for OffchainWorkers<
 	Client,
-	Storage,
 	Block,
 > {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -112,15 +109,13 @@ impl<Client, Storage, Block: traits::Block> fmt::Debug for OffchainWorkers<
 	}
 }
 
-impl<Client, Storage, Block> OffchainWorkers<
+impl<Client, Block> OffchainWorkers<
 	Client,
-	Storage,
 	Block,
 > where
 	Block: traits::Block,
 	Client: ProvideRuntimeApi<Block> + Send + Sync + 'static,
 	Client::Api: OffchainWorkerApi<Block>,
-	Storage: OffchainStorage + 'static,
 {
 	/// Start the offchain workers after given block.
 	#[must_use]
@@ -150,7 +145,6 @@ impl<Client, Storage, Block> OffchainWorkers<
 		debug!("Checking offchain workers at {:?}: version:{}", at, version);
 		if version > 0 {
 			let (api, runner) = api::AsyncApi::new(
-				self.db.clone(),
 				network_provider,
 				is_validator,
 				self.shared_client.clone(),
@@ -197,10 +191,10 @@ impl<Client, Storage, Block> OffchainWorkers<
 }
 
 /// Inform the offchain worker about new imported blocks
-pub async fn notification_future<Client, Storage, Block, Spawner>(
+pub async fn notification_future<Client, Block, Spawner>(
 	is_validator: bool,
 	client: Arc<Client>,
-	offchain: Arc<OffchainWorkers<Client, Storage, Block>>,
+	offchain: Arc<OffchainWorkers<Client, Block>>,
 	spawner: Spawner,
 	network_provider: Arc<dyn NetworkProvider + Send + Sync>,
 )
@@ -208,7 +202,6 @@ pub async fn notification_future<Client, Storage, Block, Spawner>(
 		Block: traits::Block,
 		Client: ProvideRuntimeApi<Block> + sc_client_api::BlockchainEvents<Block> + Send + Sync + 'static,
 		Client::Api: OffchainWorkerApi<Block>,
-		Storage: OffchainStorage + 'static,
 		Spawner: SpawnNamed
 {
 	client.import_notification_stream().for_each(move |n| {
@@ -300,12 +293,11 @@ mod tests {
 			spawner,
 			client.clone(),
 		));
-		let db = sc_client_db::offchain::LocalStorage::new_test();
 		let network = Arc::new(TestNetwork());
 		let header = client.header(&BlockId::number(0)).unwrap().unwrap();
 
 		// when
-		let offchain = OffchainWorkers::new(client, db);
+		let offchain = OffchainWorkers::new(client);
 		futures::executor::block_on(
 			offchain.on_block_imported(&header, network, false)
 		);
@@ -317,6 +309,8 @@ mod tests {
 
 	#[test]
 	fn offchain_index_set_and_clear_works() {
+		use sp_core::offchain::OffchainStorage;
+
 		sp_tracing::try_init_simple();
 
 		let (client, backend) =