Fix error when applying prefab changes with missing (deleted) nested prefabs

#3244

Source/Editor/CustomEditors/Dedicated/ActorEditor.cs

@@ -69,8 +69,7 @@ namespace FlaxEditor.CustomEditors.Dedicated
                         Values.SetReferenceValue(prefabInstance);
 
                         // Display prefab UI (when displaying object inside Prefab Window then display only nested prefabs)
-                        var prefabId = prefab.ID;
+                        prefab.GetNestedObject(ref prefabObjectId, out var nestedPrefabId, out var nestedPrefabObjectId);
-                        Editor.GetPrefabNestedObject(ref prefabId, ref prefabObjectId, out var nestedPrefabId, out var nestedPrefabObjectId);
                         var nestedPrefab = FlaxEngine.Content.Load<Prefab>(nestedPrefabId);
                         var panel = layout.CustomContainer<UniformGridPanel>();
                         panel.CustomControl.Height = 20.0f;

Source/Editor/Managed/ManagedEditor.cpp

@@ -617,21 +617,6 @@ void ManagedEditor::WipeOutLeftoverSceneObjects()
         ObjectsRemovalService::Flush();
 }
 
-void ManagedEditor::GetPrefabNestedObject(const Guid& prefabId, const Guid& prefabObjectId, Guid& outPrefabId, Guid& outPrefabObjectId)
-{
-    outPrefabId = Guid::Empty;
-    outPrefabObjectId = Guid::Empty;
-    const auto prefab = Content::Load<Prefab>(prefabId);
-    if (!prefab)
-        return;
-    const ISerializable::DeserializeStream** prefabObjectDataPtr = prefab->ObjectsDataCache.TryGet(prefabObjectId);
-    if (!prefabObjectDataPtr)
-        return;
-    const ISerializable::DeserializeStream& prefabObjectData = **prefabObjectDataPtr;
-    JsonTools::GetGuidIfValid(outPrefabId, prefabObjectData, "PrefabID");
-    JsonTools::GetGuidIfValid(outPrefabObjectId, prefabObjectData, "PrefabObjectID");
-}
-
 void ManagedEditor::OnEditorAssemblyLoaded(MAssembly* assembly)
 {
     ASSERT(!HasManagedInstance());

Source/Editor/Managed/ManagedEditor.h

@@ -259,7 +259,6 @@ public:
     API_FUNCTION(Internal) static Array<VisualScriptLocal> GetVisualScriptLocals();
     API_FUNCTION(Internal) static bool EvaluateVisualScriptLocal(VisualScript* script, API_PARAM(Ref) VisualScriptLocal& local);
     API_FUNCTION(Internal) static void WipeOutLeftoverSceneObjects();
-    API_FUNCTION(Internal) static void GetPrefabNestedObject(API_PARAM(Ref) const Guid& prefabId, API_PARAM(Ref) const Guid& prefabObjectId, API_PARAM(Out) Guid& outPrefabId, API_PARAM(Out) Guid& outPrefabObjectId);
 
 private:
     void OnEditorAssemblyLoaded(MAssembly* assembly);

Source/Editor/Undo/Actions/BreakPrefabLinkAction.cs

@@ -33,9 +33,14 @@ namespace FlaxEditor.Actions
                     // Check if this object comes from another nested prefab (to break link only from the top-level prefab)
                     Item nested;
                     nested.ID = ID;
-                    Editor.GetPrefabNestedObject(ref PrefabID, ref PrefabObjectID, out nested.PrefabID, out nested.PrefabObjectID);
+                    var prefab = FlaxEngine.Content.Load<Prefab>(PrefabID);
-                    if (nested.PrefabID != Guid.Empty && nested.PrefabObjectID != Guid.Empty)
+                    if (prefab != null && 
+                        prefab.GetNestedObject(ref PrefabObjectID, out nested.PrefabID, out nested.PrefabObjectID) && 
+                        nested.PrefabID != Guid.Empty && 
+                        nested.PrefabObjectID != Guid.Empty)
+                    {
                         nestedPrefabLinks.Add(nested);
+                    }
                 }
             }
         }

Source/Engine/Level/Prefabs/Prefab.Apply.cpp

@@ -707,7 +707,7 @@ bool Prefab::ApplyAll(Actor* targetActor)
         for (int32 i = 0; i < nestedPrefabIds.Count(); i++)
         {
             const auto nestedPrefab = Content::LoadAsync<Prefab>(nestedPrefabIds[i]);
-            if (nestedPrefab && nestedPrefab != this && (nestedPrefab->Flags & ObjectFlags::WasMarkedToDelete) == ObjectFlags::None)
+            if (nestedPrefab && nestedPrefab != this && EnumHasNoneFlags(nestedPrefab->Flags, ObjectFlags::WasMarkedToDelete))
             {
                 allPrefabs.Add(nestedPrefab);
             }
@@ -778,6 +778,29 @@ bool Prefab::ApplyAllInternal(Actor* targetActor, bool linkTargetActorObjectToPr
         for (int32 i = 0; i < targetObjects->Count(); i++)
         {
             SceneObject* obj = targetObjects.Value->At(i);
+
+            // Check the whole chain of prefab references to be valid for this object
+            bool brokenPrefab = false;
+            Guid nestedPrefabId = obj->GetPrefabID(), nestedPrefabObjectId = obj->GetPrefabObjectID();
+            while (!brokenPrefab && nestedPrefabId.IsValid() && nestedPrefabObjectId.IsValid())
+            {
+                auto prefab = Content::Load<Prefab>(nestedPrefabId);
+                if (prefab)
+                {
+                    prefab->GetNestedObject(nestedPrefabObjectId, nestedPrefabId, nestedPrefabObjectId);
+                }
+                else
+                {
+                    LOG(Warning, "Missing prefab {0}.", nestedPrefabId);
+                    brokenPrefab = true;
+                }
+            }
+            if (brokenPrefab)
+            {
+                LOG(Warning, "Broken prefab reference on object {0}. Breaking linkage to inline object inside prefab.", GetObjectName(obj));
+                obj->BreakPrefabLink();
+            }
+
             writer.SceneObject(obj);
         }
         writer.EndArray();
@@ -809,7 +832,7 @@ bool Prefab::ApplyAllInternal(Actor* targetActor, bool linkTargetActorObjectToPr
             SceneObject* obj = targetObjects.Value->At(i);
             auto data = it->GetObject();
 
-            // Check if object is from that prefab
+            // Check if object is from this prefab
             if (obj->GetPrefabID() == prefabId)
             {
                 if (!obj->GetPrefabObjectID().IsValid())
@@ -883,7 +906,7 @@ bool Prefab::ApplyAllInternal(Actor* targetActor, bool linkTargetActorObjectToPr
         {
             const SceneObject* obj = targetObjects->At(i);
 
-            // Check if object is from that prefab
+            // Check if object is from this prefab
             if (obj->GetPrefabID() == prefabId)
             {
                 // Map prefab instance to existing prefab object

Source/Engine/Level/Prefabs/Prefab.cpp

@@ -94,6 +94,24 @@ SceneObject* Prefab::GetDefaultInstance(const Guid& objectId)
     return result;
 }
 
+bool Prefab::GetNestedObject(const Guid& objectId, Guid& outPrefabId, Guid& outObjectId) const
+{
+    if (WaitForLoaded())
+        return false;
+    bool result = false;
+    Guid result1 = Guid::Empty, result2 = Guid::Empty;
+    const ISerializable::DeserializeStream** prefabObjectDataPtr = ObjectsDataCache.TryGet(objectId);
+    if (prefabObjectDataPtr)
+    {
+        const ISerializable::DeserializeStream& prefabObjectData = **prefabObjectDataPtr;
+        result = JsonTools::GetGuidIfValid(result1, prefabObjectData, "PrefabID") &&
+                JsonTools::GetGuidIfValid(result2, prefabObjectData, "PrefabObjectID");
+    }
+    outPrefabId = result1;
+    outObjectId = result2;
+    return result;
+}
+
 void Prefab::DeleteDefaultInstance()
 {
     ScopeLock lock(Locker);

Source/Engine/Level/Prefabs/Prefab.h

@@ -70,6 +70,15 @@ public:
     /// <returns>The object of the prefab loaded from the prefab. Contains the default values. It's not added to gameplay but deserialized with postLoad and init event fired.</returns>
     API_FUNCTION() SceneObject* GetDefaultInstance(API_PARAM(Ref) const Guid& objectId);
 
+    /// <summary>
+    /// Gets the reference to the other nested prefab for a specific prefab object.
+    /// </summary>
+    /// <param name="objectId">The ID of the object in this prefab.</param>
+    /// <param name="outPrefabId">Result ID of the prefab asset referenced by the given object.</param>
+    /// <param name="outObjectId">Result ID of the prefab object referenced by the given object.</param>
+    /// <returns>True if got valid reference, otherwise false.</returns>
+    API_FUNCTION() bool GetNestedObject(API_PARAM(Ref) const Guid& objectId, API_PARAM(Out) Guid& outPrefabId, API_PARAM(Out) Guid& outObjectId) const;
+
 #if USE_EDITOR
     /// <summary>
     /// Applies the difference from the prefab object instance, saves the changes and synchronizes them with the active instances of the prefab asset.

Source/Engine/Tests/TestPrefabs.cpp

@@ -559,7 +559,7 @@ TEST_CASE("Prefabs")
         Content::DeleteAsset(prefabNested1);
         Content::DeleteAsset(prefabBase);
     }
-    SECTION("Test Applying Prefab ChangeTo Object References")
+    SECTION("Test Applying Prefab Change To Object References")
     {
         // https://github.com/FlaxEngine/FlaxEngine/issues/3136
 
@@ -614,4 +614,78 @@ TEST_CASE("Prefabs")
         instanceB->DeleteObject();
         Content::DeleteAsset(prefab);
     }
+    SECTION("Test Applying Prefab With Missing Nested Prefab")
+    {
+        // https://github.com/FlaxEngine/FlaxEngine/issues/3244
+
+        // Create Prefab B with just root object
+        AssetReference<Prefab> prefabB = Content::CreateVirtualAsset<Prefab>();
+        REQUIRE(prefabB);
+        Guid id;
+        Guid::Parse("25dbe4b0416be0777a6ce59e8788b10f", id);
+        prefabB->ChangeID(id);
+        auto prefabBInit = prefabB->Init(Prefab::TypeName,
+                                         "["
+                                         "{"
+                                         "\"ID\": \"aac6b9644492fbca1a6ab0a7904a557e\","
+                                         "\"TypeName\": \"FlaxEngine.ExponentialHeightFog\","
+                                         "\"Name\": \"Prefab B.Root\""
+                                         "}"
+                                         "]");
+        REQUIRE(!prefabBInit);
+
+        // Create Prefab A with nested Prefab B attached to the root
+        AssetReference<Prefab> prefabA = Content::CreateVirtualAsset<Prefab>();
+        REQUIRE(prefabA);
+        Guid::Parse("4cb744714f746e31855f41815612d14b", id);
+        prefabA->ChangeID(id);
+        auto prefabAInit = prefabA->Init(Prefab::TypeName,
+                                         "["
+                                         "{"
+                                         "\"ID\": \"244274a04cc60d56a2f024bfeef5772d\","
+                                         "\"TypeName\": \"FlaxEngine.SpotLight\","
+                                         "\"Name\": \"Prefab A.Root\""
+                                         "},"
+                                         "{"
+                                         "\"ID\": \"1e51f1094f430733333f8280e78dfcc3\","
+                                         "\"PrefabID\": \"25dbe4b0416be0777a6ce59e8788b10f\","
+                                         "\"PrefabObjectID\": \"aac6b9644492fbca1a6ab0a7904a557e\","
+                                         "\"ParentID\": \"244274a04cc60d56a2f024bfeef5772d\""
+                                         "}"
+                                         "]");
+        REQUIRE(!prefabAInit);
+
+        // Spawn test instances of both prefabs
+        ScriptingObjectReference<Actor> instanceA = PrefabManager::SpawnPrefab(prefabA);
+        ScriptingObjectReference<Actor> instanceB = PrefabManager::SpawnPrefab(prefabB);
+
+        // Delete nested prefab
+        Content::DeleteAsset(prefabB);
+        
+        // Apply instance A and verify it's fine even tho prefab B doesn't exist anymore
+        bool applyResult = PrefabManager::ApplyAll(instanceA);
+        REQUIRE(!applyResult);
+
+        // Check state of objects
+        REQUIRE(instanceA);
+        REQUIRE(instanceA->Children.Count() == 1);
+        REQUIRE(instanceA->Children[0] != nullptr);
+        REQUIRE(instanceA->Children[0]->Is<ExponentialHeightFog>());
+        REQUIRE(instanceB);
+        REQUIRE(instanceB->Is<ExponentialHeightFog>());
+
+        // Verify if prefab has new data to properly spawn another prefab
+        ScriptingObjectReference<Actor> instanceC = PrefabManager::SpawnPrefab(prefabA);
+        REQUIRE(instanceC);
+        REQUIRE(instanceC->Children.Count() == 1);
+        REQUIRE(instanceC->Children[0] != nullptr);
+        REQUIRE(instanceC->Children[0]->Is<ExponentialHeightFog>());
+
+        // Cleanup
+        instanceA->DeleteObject();
+        instanceB->DeleteObject();
+        instanceC->DeleteObject();
+        Content::DeleteAsset(prefabA);
+
+    }
 }