SnapshotStore can reply with SnapshotNotFound if it is saving an EntitySnapshot

Author: Taichi Yamakawa

src/main/scala/lerna/akka/entityreplication/raft/snapshot/SnapshotStore.scala

@@ -96,8 +96,11 @@ private[entityreplication] class SnapshotStore(
               cmd.entityId,
             )
         case FetchSnapshot(_, replyTo) =>
-          prevSnapshot.foreach { s =>
-            replyTo ! SnapshotProtocol.SnapshotFound(s)
+          prevSnapshot match {
+            case Some(prevSnapshot) =>
+              replyTo ! SnapshotProtocol.SnapshotFound(prevSnapshot)
+            case None =>
+              replyTo ! SnapshotProtocol.SnapshotNotFound(entityId)
           }
       }
     case _: persistence.SaveSnapshotSuccess =>

src/test/scala/lerna/akka/entityreplication/raft/snapshot/ShardSnapshotStoreFailureSpec.scala

@@ -109,7 +109,6 @@ class ShardSnapshotStoreFailureSpec
     }
 
     "reply with `SnapshotNotFound` to `FetchSnapshot` if it has no EntitySnapshot and is saving an EntitySnapshot" in {
-      // TODO Change SnapshotStore.savingSnapshot such that this test passes.
       val entityId           = generateUniqueEntityId()
       val shardSnapshotStore = createShardSnapshotStore()
       val metadata           = EntitySnapshotMetadata(entityId, LogEntryIndex(1))
@@ -123,7 +122,7 @@ class ShardSnapshotStoreFailureSpec
 
         // Test:
         shardSnapshotStore ! FetchSnapshot(entityId, replyTo = testActor)
-        expectMsg(SnapshotNotFound)
+        expectMsg(SnapshotNotFound(entityId))
       } finally {
         // Cleanup:
         // The succeeding tests will fail unless the promise is fulfilled.