Unity does not support SerializeReference in JsonUtility

Hello.

We have been in contact with support since April with issues around SerializeReference (1240887, 1245749, 1275317, 1277193).

Then we got the following message yesterday as part of case "1275317" (originally reported here).

"I just got a reply from the developer. IT turns out that this behavior is actually by design. We do not support SerializeReference in JsonUtility."​

We have invested on this setup and it works 99.999% of the time. Until now it looked more like a bug than a lack of support.

So we would appreciate some further explanation before we rip it out.

1. In the documentation I didn't find a thing explicitly says that SerializeReference is not supported by JsonUtility:

• JsonUtility.FromJson Internally, this method uses the Unity serializer; therefore the type you are creating must be supported by the serializer. [...]
• SerializeReference lists a list of restrictions.
  
• There's a weird note in ISerializationCallbackReceiver about "fields marked with [SerializeReference] that reference managed instances with [SerializeReference] fields" which I am not sure to interpret properly because of the lack of clear definition for "managed instances".

2. In the 4 years or more that JsonUtility has existed, there has to my knowledge not been a difference in support between what is supported by the unity serializer and JsonUtility itself. So it's a bit weird to add this now.

3. in all our conversations with support or on the forum in the 4-5 months we have been reporting issues, no-one has ever raised an issue with the potential incompatibility.

All in all this seems to come against the Principle of Least Astonishment and also a bit late...

If SerializeReference is indeed not supported in JsonUtiity, the consequences are serious for us. We have to change our serialization layer to something more stable and force an update to 8 products on 5 platforms, affecting tens of thousand of users. This is not a small task and we are not taking it lightly.

Can someone with knowledge of the internals

• confirm that JsonUtility doesn't support SerializeReference
• let us know why
• let us know if there are ways to work-around this issue (given that it works most of the time)
• bonus point: let us know if it will be supported one day

Thanks,

Note: we have also asked for paid support several weeks ago and we are still waiting for someone to take contact...

 

Hi,

Is there any news on those topics?
Tried looking into the issues posted above:
(1240887, 1245749, 1275317, 1277193). but only 1245749 seem to exist (or is public?).

Using JSONUtility to create savefiles based on serialized SO containing my savedata. Some of the more complex SO contains ScriptableReferences. Having some issues with loading the save file after reload of the editor. It actually works to save/load in the same session of unity.

 

Hello from the future!

Just chiming in to say this now appears to work Yay!!

Input:

Code (CSharp):

1.     public interface Y { }
2.  
3.     [Serializable]
4.     public class X
5.     {
6.         [SerializeReference] public List<Y> Ys;
7.     }
8.     [Serializable]
9.     public class Z : Y { }
10.     [Serializable]
11.     public class W : Y { }
12.  
13.     ...
14.  
15.         var x = new X
16.         {
17.             Ys = new List<Y>
18.             {
19.                 new Z(),
20.                 new W(),
21.             },
22.         };
23.         var json = JsonUtility.ToJson(x);
24.         UnityEngine.Debug.Log(json);
25.  
26.         var xFromJson = JsonUtility.FromJson<X>(json);
27.         foreach (var y in xFromJson.Ys)
28.             UnityEngine.Debug.Log(y);

Output logs:

Code (CSharp):

1. {"Ys":[{"rid":1000},{"rid":1001}],"references":{"version":2,"RefIds":[{"rid":1000,"type":{"class":"Test/Z","ns":"","asm":"Assembly-CSharp"},"data":{}},{"rid":1001,"type":{"class":"Test/W","ns":"","asm":"Assembly-CSharp"},"data":{}}]}}
2.  
3. Test+Z
4.  
5. Test+W