Added client function to delete a recent block (#8533)

* Implemented recent block removal

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/client/api/src/backend.rs

@@ -475,6 +475,12 @@ pub trait Backend<Block: BlockT>: AuxStore + Send + Sync {
 		revert_finalized: bool,
 	) -> sp_blockchain::Result<(NumberFor<Block>, HashSet<Block::Hash>)>;
 
+	/// Discard non-best, unfinalized leaf block.
+	fn remove_leaf_block(
+		&self,
+		hash: &Block::Hash,
+	) -> sp_blockchain::Result<()>;
+
 	/// Insert auxiliary data into key-value store.
 	fn insert_aux<
 		'a,

substrate/client/api/src/in_mem.rs

@@ -770,6 +770,13 @@ impl<Block: BlockT> backend::Backend<Block> for Backend<Block> where Block::Hash
 		Ok((Zero::zero(), HashSet::new()))
 	}
 
+	fn remove_leaf_block(
+		&self,
+		_hash: &Block::Hash,
+	) -> sp_blockchain::Result<()> {
+		Ok(())
+	}
+
 	fn get_import_lock(&self) -> &RwLock<()> {
 		&self.import_lock
 	}

substrate/client/api/src/leaves.rs

@@ -216,8 +216,8 @@ impl<H, N> LeafSet<H, N> where
 		self.pending_removed.clear();
 	}
 
-	#[cfg(test)]
-	fn contains(&self, number: N, hash: H) -> bool {
+	/// Check if given block is a leaf.
+	pub fn contains(&self, number: N, hash: H) -> bool {
 		self.storage.get(&Reverse(number)).map_or(false, |hashes| hashes.contains(&hash))
 	}