(Case 1108041) AddComponent to Prefab in AssetPostprocessor causes assertion

Adding a Component to a Prefab in an AssetPostprocessor, causes the editor to trigger an assertion. This used to work in Unity prior 2018.3.

Reproduce
1) Open attached user project
2) Click "GameObject > 3D Object > Cube"
3) Drag&drop "Cube" from Hierarchy to Project to create a prefab of it

Actual
The editor outputs Assertion failed on expression: '!go.TestHideFlag(Object::kNotEditable)'

Expected
No error.

Code (CSharp):

1. Assertion failed on expression: '!go.TestHideFlag(Object::kNotEditable)'
2.  
3. UnityEngine.GameObject:Internal_AddComponentWithType()
4. UnityEngine.GameObject:AddComponent(Type) (at C:\buildslave\unity\build\Runtime\Export\GameObject.bindings.cs:221)
5. UnityEngine.GameObject:AddComponent() (at C:\buildslave\unity\build\Runtime\Export\GameObject.bindings.cs:226)
6. PrefabReferenceProcessor:OnPostprocessInternal(String) (at Assets\Editor\PrefabReferenceProcessor.cs:48)
7. PrefabReferenceProcessor:OnPostprocessAllAssets(String[], String[], String[], String[]) (at Assets\Editor\PrefabReferenceProcessor.cs:33)
8. System.Reflection.MonoMethod:InternalInvoke()
9. System.Reflection.MonoMethod:Invoke(Object, BindingFlags, Binder, Object[], CultureInfo)
10. System.Reflection.MethodBase:Invoke(Object, Object[])
11. UnityEditor.AssetPostprocessingInternal:PostprocessAllAssets(String[], String[], String[], String[], String[]) (at C:\buildslave\unity\build\Editor\Mono\AssetPostprocessor.cs:141)
12. UnityEditorInternal.InternalEditorUtility:ProjectWindowDrag()
13. UnityEditor.LocalGroup:DoDrag(Int32, Boolean) (at C:\buildslave\unity\build\Editor\Mono\ObjectListLocalGroup.cs:1247)
14. UnityEditor.LocalGroup:HandleUnusedDragEvents(Single) (at C:\buildslave\unity\build\Editor\Mono\ObjectListLocalGroup.cs:270)
15. UnityEditor.Group:Draw(Single, Vector2, Int32&) (at C:\buildslave\unity\build\Editor\Mono\ObjectListGroup.cs:161)
16. UnityEditor.ObjectListArea:HandleListArea() (at C:\buildslave\unity\build\Editor\Mono\ObjectListArea.cs:1330)
17. UnityEditor.ObjectListArea:OnGUI(Rect, Int32) (at C:\buildslave\unity\build\Editor\Mono\ObjectListArea.cs:541)
18. UnityEditor.ProjectBrowser:OnGUI() (at C:\buildslave\unity\build\Editor\Mono\ProjectBrowser.cs:1965)
19. System.Reflection.MonoMethod:InternalInvoke()
20. System.Reflection.MonoMethod:Invoke(Object, BindingFlags, Binder, Object[], CultureInfo)
21. System.Reflection.MethodBase:Invoke(Object, Object[])
22. UnityEditor.HostView:Invoke(String, Object) (at C:\buildslave\unity\build\Editor\Mono\HostView.cs:342)
23. UnityEditor.HostView:Invoke(String) (at C:\buildslave\unity\build\Editor\Mono\HostView.cs:336)
24. UnityEditor.HostView:InvokeOnGUI(Rect, Rect) (at C:\buildslave\unity\build\Editor\Mono\HostView.cs:302)
25. UnityEditor.DockArea:DrawView(Rect, Rect, Boolean, Boolean, Boolean) (at C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:363)
26. UnityEditor.DockArea:OldOnGUI() (at C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:322)
27. UnityEngine.Experimental.UIElements.IMGUIContainer:DoOnGUI(Event, Matrix4x4, Rect, Boolean) (at C:\buildslave\unity\build\Modules\UIElements\IMGUIContainer.cs:244)
28. UnityEngine.Experimental.UIElements.IMGUIContainer:HandleIMGUIEvent(Event, Matrix4x4, Rect) (at C:\buildslave\unity\build\Modules\UIElements\IMGUIContainer.cs:438)
29. UnityEngine.Experimental.UIElements.IMGUIContainer:HandleIMGUIEvent(Event) (at C:\buildslave\unity\build\Modules\UIElements\IMGUIContainer.cs:421)
30. UnityEngine.Experimental.UIElements.IMGUIContainer:HandleEvent(EventBase) (at C:\buildslave\unity\build\Modules\UIElements\IMGUIContainer.cs:401)
31. UnityEngine.Experimental.UIElements.EventDispatcher:PropagateEvent(EventBase) (at C:\buildslave\unity\build\Modules\UIElements\EventDispatcher.cs:754)
32. UnityEngine.Experimental.UIElements.EventDispatcher:ProcessEvent(EventBase, IPanel) (at C:\buildslave\unity\build\Modules\UIElements\EventDispatcher.cs:599)
33. UnityEngine.Experimental.UIElements.EventDispatcher:Dispatch(EventBase, IPanel, DispatchMode) (at C:\buildslave\unity\build\Modules\UIElements\EventDispatcher.cs:307)
34. UnityEngine.Experimental.UIElements.BaseVisualElementPanel:SendEvent(EventBase, DispatchMode) (at C:\buildslave\unity\build\Modules\UIElements\Panel.cs:176)
35. UnityEngine.Experimental.UIElements.UIElementsUtility:DoDispatch(BaseVisualElementPanel) (at C:\buildslave\unity\build\Modules\UIElements\UIElementsUtility.cs:245)
36. UnityEngine.Experimental.UIElements.UIElementsUtility:ProcessEvent(Int32, IntPtr) (at C:\buildslave\unity\build\Modules\UIElements\UIElementsUtility.cs:68)
37. UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr) (at C:\buildslave\unity\build\Modules\IMGUI\GUIUtility.cs:179)

 

I get this same error--in this case playmaker is causing it somehow.

Code (CSharp):

1. Assertion failed on expression: '!go.TestHideFlag(Object::kNotEditable)'
2. UnityEngine.GameObject:AddComponent()
3. PlayMakerFSM:GetEventHandlerComponent(GameObject) (at C:/Projects/Playmaker_1.9.0/Projects/Playmaker.source.unity/Assets/PlayMaker/PlayMakerFSM.cs:469)
4. PlayMakerFSM:AddEventHandlerComponent() (at C:/Projects/Playmaker_1.9.0/Projects/Playmaker.source.unity/Assets/PlayMaker/PlayMakerFSM.cs:447)
5. PlayMakerFSM:AddEventHandlerComponents() (at C:/Projects/Playmaker_1.9.0/Projects/Playmaker.source.unity/Assets/PlayMaker/PlayMakerFSM.cs:385)
6. PlayMakerFSM:Preprocess() (at C:/Projects/Playmaker_1.9.0/Projects/Playmaker.source.unity/Assets/PlayMaker/PlayMakerFSM.cs:225)
7. HutongGames.PlayMakerEditor.PlayMakerBuildCallbacks:OnPostprocessScene() (at C:/Projects/Playmaker_1.9.0/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/PlayMakerBuildCallbacks.cs:34)
8. UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

 

2018.3.5f1
same question