Expose moon_getLatestSyncedBlock RPC endpoint (#2858)

* Expose RPC endpoint
* add test
* apply review suggestions

client/rpc/finality/src/lib.rs

@@ -14,10 +14,13 @@
 // You should have received a copy of the GNU General Public License
 // along with Moonbeam.  If not, see <http://www.gnu.org/licenses/>.
 use fc_rpc::frontier_backend_client::{self, is_canon};
+
+use jsonrpsee::types::error::ErrorObject;
 use jsonrpsee::{core::RpcResult, proc_macros::rpc};
 use sp_blockchain::HeaderBackend;
 use sp_core::H256;
 use sp_runtime::traits::Block;
+use std::ops::Deref;
 use std::{marker::PhantomData, sync::Arc};
 
 /// An RPC endpoint to check for finality of blocks and transactions in Moonbeam
@@ -33,6 +36,10 @@ pub trait MoonbeamFinalityApi {
 	/// Returns false if the transaction is not found
 	#[method(name = "moon_isTxFinalized")]
 	async fn is_tx_finalized(&self, tx_hash: H256) -> RpcResult<bool>;
+
+	/// Gets the latest block hash that is fully indexed in frontier's backend.
+	#[method(name = "moon_getLatestBlockHash")]
+	async fn get_latest_block_hash(&self) -> RpcResult<H256>;
 }
 
 pub struct MoonbeamFinality<B: Block, C> {
@@ -80,6 +87,18 @@ where
 			Ok(false)
 		}
 	}
+
+	async fn get_latest_block_hash(&self) -> RpcResult<H256> {
+		let res = self.backend.deref().latest_block_hash().await;
+		match res {
+			Ok(val) => Ok(val),
+			Err(e) => Err(ErrorObject::owned(
+				jsonrpsee::types::error::UNKNOWN_ERROR_CODE,
+				"No synced block",
+				Some(e),
+			)),
+		}
+	}
 }
 
 async fn is_block_finalized_inner<B: Block<Hash = H256>, C: HeaderBackend<B> + 'static>(

moonbeam-types-bundle/index.ts

@@ -88,6 +88,11 @@ export const rpcDefinitions: Record<string, Record<string, DefinitionRpc | Defin
       params: [{ name: "txHash", type: "Hash" }],
       type: "bool",
     },
+    getLatestSyncedBlock: {
+      description: "Returns the latest synced block from frontier's backend",
+      params: [],
+      type: "u32",
+    },
   },
 };
 

test/suites/dev/moonbase/test-moon/test-moon-rpc.ts

@@ -155,5 +155,15 @@ describeSuite({
         expect(resp, "Transaction finalization status mismatch").toBe(true);
       },
     });
+
+    it({
+      id: "T11",
+      title: "should return latest synced block",
+      test: async function () {
+        const expected = await context.createBlock([], { finalize: true });
+        const resp = await customDevRpcRequest("moon_getLatestBlockHash", []);
+        expect(resp, "Latest block hash").toBe(expected.block.hash);
+      },
+    });
   },
 });

typescript-api/src/moonbase/interfaces/augment-api-rpc.ts

@@ -618,6 +618,8 @@ declare module "@polkadot/rpc-core/types/jsonrpc" {
       isBlockFinalized: AugmentedRpc<(blockHash: Hash | string | Uint8Array) => Observable<bool>>;
       /** Returns whether an Ethereum transaction is finalized */
       isTxFinalized: AugmentedRpc<(txHash: Hash | string | Uint8Array) => Observable<bool>>;
+      /** Returns the latest synced block from Frontier's backend */
+      getLatestSyncedBlock: AugmentedRpc<() => Observable<u32>>;
     };
     net: {
       /** Returns true if client is actively listening for network connections. Otherwise false. */

typescript-api/src/moonbase/interfaces/moon/definitions.ts

@@ -11,5 +11,10 @@ export default {
       params: [{ name: "txHash", type: "Hash" }],
       type: "bool",
     },
+    getLatestSyncedBlock: {
+      description: "Returns the latest synced block from Frontier's backend",
+      params: [],
+      type: "u32",
+    },
   },
 };