Synchronize state cache on finalization (#3246)

* Reorg test

* Fixed informant misreporting reorgs

* Update cache when reorg is caused by applying finality

* Test for finality reorg

* Simplified test

* Typo

Co-Authored-By: André Silva <andre.beat@gmail.com>

substrate/core/client/db/src/lib.rs

@@ -1108,21 +1108,24 @@ impl<Block: BlockT<Hash=H256>> Backend<Block> {
 			None
 		};
 
-		if let Some(set_head) = operation.set_head {
+		let cache_update = if let Some(set_head) = operation.set_head {
 			if let Some(header) = ::client::blockchain::HeaderBackend::header(&self.blockchain, set_head)? {
 				let number = header.number();
 				let hash = header.hash();
 
-				self.set_head_with_transaction(
+				let (enacted, retracted) = self.set_head_with_transaction(
 					&mut transaction,
 					hash.clone(),
 					(number.clone(), hash.clone())
 				)?;
 				meta_updates.push((hash, *number, true, false));
+				Some((enacted, retracted))
 			} else {
 				return Err(client::error::Error::UnknownBlock(format!("Cannot set head {:?}", set_head)))
 			}
-		}
+		} else {
+			None
+		};
 
 		let write_result = self.storage.db.write(transaction).map_err(db_err);
 
@@ -1152,6 +1155,10 @@ impl<Block: BlockT<Hash=H256>> Backend<Block> {
 			);
 		}
 
+		if let Some((enacted, retracted)) = cache_update {
+			self.shared_cache.lock().sync(&enacted, &retracted);
+		}
+
 		for (hash, number, is_best, is_finalized) in meta_updates {
 			self.blockchain.update_meta(hash, number, is_best, is_finalized);
 		}