add new function to all RelayChainInterface implementations

client/consensus/common/src/tests.rs

@@ -186,7 +186,6 @@ impl RelayChainInterface for Relaychain {
 	}
 
 	async fn wait_for_block(&self, _: PHash) -> RelayChainResult<()> {
-		unimplemented!("Not needed for test")
 	}
 
 	async fn new_best_notification_stream(
@@ -207,6 +206,10 @@ impl RelayChainInterface for Relaychain {
 			})
 			.boxed())
 	}
+
+	async fn header(&self, block_id: PHash) -> RelayChainResult<Option<PHeader>> {
+		unimplemented!("Not needed for test")
+	}
 }
 
 fn build_block<B: InitBlockBuilder>(

client/network/src/tests.rs

@@ -237,6 +237,10 @@ impl RelayChainInterface for DummyRelayChainInterface {
 				});
 		Ok(Box::pin(notifications_stream))
 	}
+
+	async fn header(&self, block_id: PHash) -> RelayChainResult<Option<PHeader>> {
+		unimplemented!("Not needed for test")
+	}
 }
 
 fn make_validator_and_api(

client/relay-chain-inprocess-interface/src/lib.rs

@@ -171,6 +171,10 @@ where
 		Ok(self.sync_oracle.is_major_syncing())
 	}
 
+	async fn header(&self, block_id: PHash) -> RelayChainResult<Option<PHeader>> {
+		Ok(self.backend.header(block_hash)?)
+	}
+
 	fn overseer_handle(&self) -> RelayChainResult<Handle> {
 		Ok(self.overseer_handle.clone())
 	}

client/relay-chain-rpc-interface/src/lib.rs

@@ -132,6 +132,10 @@ impl RelayChainInterface for RelayChainRpcInterface {
 		self.rpc_client.system_health().await.map(|h| h.is_syncing)
 	}
 
+	async fn header(&self, block_id: RelayHash) -> RelayChainResult<Option<RelayHeader>> {
+		self.rpc_client.chain_get_header(Some(block_id)).await
+	}
+
 	fn overseer_handle(&self) -> RelayChainResult<Handle> {
 		Ok(self.overseer_handle.clone())
 	}