Return target_hash for finality_target instead of an Option (#9867)

* .

cargo +nightly fmt --all

* Fix test

* Simplify test

* They are already imported

* Needless clone()

client/consensus/common/src/longest_chain.rs

@@ -91,11 +91,12 @@ where
 		&self,
 		target_hash: Block::Hash,
 		maybe_max_number: Option<NumberFor<Block>>,
-	) -> Result<Option<Block::Hash>, ConsensusError> {
+	) -> Result<Block::Hash, ConsensusError> {
 		let import_lock = self.backend.get_import_lock();
 		self.backend
 			.blockchain()
 			.best_containing(target_hash, maybe_max_number, import_lock)
+			.map(|maybe_hash| maybe_hash.unwrap_or(target_hash))
 			.map_err(|e| ConsensusError::ChainLookup(e.to_string()).into())
 	}
 }

client/finality-grandpa/src/environment.rs

@@ -1165,7 +1165,7 @@ where
 	debug!(target: "afg", "Finding best chain containing block {:?} with number limit {:?}", block, limit);
 
 	let result = match select_chain.finality_target(block, None).await {
-		Ok(Some(best_hash)) => {
+		Ok(best_hash) => {
 			let best_header = client
 				.header(BlockId::Hash(best_hash))?
 				.expect("Header known to exist after `finality_target` call; qed");
@@ -1223,10 +1223,6 @@ where
 				})
 				.or_else(|| Some((target_header.hash(), *target_header.number())))
 		},
-		Ok(None) => {
-			debug!(target: "afg", "Encountered error finding best chain containing {:?}: couldn't find target block", block);
-			None
-		},
 		Err(e) => {
 			debug!(target: "afg", "Encountered error finding best chain containing {:?}: {:?}", block, e);
 			None

client/finality-grandpa/src/import.rs

@@ -118,10 +118,10 @@ where
 						)
 						.await
 				} else {
-					Ok(Some(pending_change.canon_hash))
+					Ok(pending_change.canon_hash)
 				};
 
-				if let Ok(Some(hash)) = effective_block_hash {
+				if let Ok(hash) = effective_block_hash {
 					if let Ok(Some(header)) = self.inner.header(BlockId::Hash(hash)) {
 						if *header.number() == pending_change.effective_number() {
 							out.push((header.hash(), *header.number()));