Weird behavior and potential project corruption if you copy a scene with sliders

[TheRealSoloLeo]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Copying a scene with a slider in it and pasting it in a different project can corrupt the project.

Steps to reproduce

1. Create a new project
2. Click on "Add a new object"
3. Select "slider"
4. This happened with "Square White Slider", I haven't tested if it works with the other ones
5. Copy the scene
6. Create a new project and paste the scene with the slider in it
7. The slider is now a corrupted object
8. If you don't delete the object before closing the project GDevelop will refuse to open it and say it's corrupted

GDevelop platform

Desktop, Web, Mobile

GDevelop version

5.4.209

Platform info

Windows

Windows 11

Additional context

I also put an instance of the object in the scene before copying it, I don't know if this is necessary to reproduce the bug.

The only way to recover the project is by manually deleting the slider in the json.

[ClementPasteau]

Thanks for the report @TheRealSoloLeo

@D8H is looking into it.

[D8H]

The issue happens when:

• the project with the custom object and its extension is open
• the project with the copied custom object but where the extension is missing is open (letting GDevelop close the other project automatically)

The error message is "Error: Event-based objects don't have blueprint. This method should not never be called.".

As a workaround :

• the project with the missing extension can be open if the other project is closed manually beforehand.
• the missing extension can then be installed, the project needs to be closed and open back to see the custom object configuration
• then the resources must be added to the new project.

[4ian]

@D8H What can we do to fix the issue?