Bug [2020.2.0b10, case 1290917] Destroyed UI object can be added to raycasts breaking whole UI

New raycastTarget is defined as:

Code (CSharp):

1.  
2. public virtual bool raycastTarget
3. {
4.     get
5.     {
6.         return m_RaycastTarget;
7.     }
8.     set
9.     {
10.         if (value != m_RaycastTarget)
11.         {
12.             if (m_RaycastTarget)
13.                 GraphicRegistry.UnregisterRaycastGraphicForCanvas(canvas, this);
14.             m_RaycastTarget = value;
15.             if (m_RaycastTarget)
16.                 GraphicRegistry.RegisterRaycastGraphicForCanvas(canvas, this);
17.         }
18.     }
19. }
20.  

There's no null check there or in RegisterRaycastGraphicForCanvas so it can be used freely on destroyed object:

Code (CSharp):

1. button.onClick.AddListener( async () =>
2.     {
3.         var graphic = button.targetGraphic;
4.         graphic.raycastTarget = false;
5.         Destroy( button.gameObject );
6.         graphic.raycastTarget = true;
7.     } );

Doing that breaks whole ui input.




Bug doesn't exist in 2020.1

 

A bit better code to reproduce as object is destroyed after update loop:

Code (CSharp):

1. button.onClick.AddListener( async () =>
2.     {
3.         var graphic = button.targetGraphic;
4.         graphic.raycastTarget = false;
5.         Destroy( button.gameObject );
6.         await Task.Delay( 100 );
7.         graphic.raycastTarget = true;
8.     } );

 

I can confirm this happens in our project as well using 2020.2.0f1, although we found an easy work around.

For Unity Devs: Perhaps check if the graphic object is alive when the user sets graphic.raycastTarget to true? Could that do the trick?