[v4.4.1] .NET inherited scene, export node pointing at node error

[Drarch]

Tested versions

• Reproduicable in v4.4.1-stable_mono
• No error at Godot_v4.3-beta1_mono

System information

Windows 11

Issue description

I have a base scene:

• RootNode
  • ToRootNode

ToRootNode has an export variable with the root node assigned to it. ToRootNode.ToRootNode => RootNode

When I create an inherited scene of this and assigned extended script to root, with no changes, then on runtime I got an error from ToRootNode.

void System.ThrowHelper.ThrowObjectDisposedException(object): System.ObjectDisposedException: Cannot access a disposed object.

Only when scripts are in C#, and only when the inherited scene has its own script inheriting from BaseNode script. No new changes in the script are needed.
When using GdScript with the same structure and approach it works fine. Only C# script version loses a connection to its root node.

When updating an engine version I notice in script change after opening a scene that there were some scene optimizations, and the inherited nodes are removed from scene structure. So maybe that is why C# script loses reference to node. Root node in inherited scene changes a name, so it might look for a wrong node that no longer exists.

Steps to reproduce

I added an MRP, where at scene when pushed corresponding button, script tries to access a node via structure I described.

Minimal reproduction project (MRP)

inheritancebug.zip

[raulsntos]

Thanks for the report! It seems like it may be a duplicate of one or both of these issues:

• Inherited scene child node field set to root node through Inspector is not correctly set upon instantiation when the inherited scene extends the base scene's c# script. #86970
• C# Reference in a Inherited Scene breaks (Null or Disposed) #99018

It looks like, because of how inherited scenes are instantiated, the nodes in the scene are referencing an instance that is disposed. The base scene (BaseNode.tscn) is instantiated first which creates an instance of the BaseNode.cs script. Then, the derived scene (InheritedNode.tscn) is instantiated which creates an instance of the InheritedNode.cs script to replace the old one. However, the nodes in the scene are still referencing the BaseNode object that is now disposed.

Your MRP is a little more convoluted because you have the ToRootNode instance in the middle, but I believe it's the same issue. So I'll be closing this issue as a duplicate.