Errors related to SerializeReference after upgrading from 2020.3 to 2021.3

Hi! We don't have current bug reports exactly matching what you describe. However I suspect that your project might have field names that happen to conflict, at the serialization level, with the field names we use to record information about SerializeReference objects. The assert and error you indicate might mean that Unity is confused as it thought it found a SerializeReference reference, but then cannot match that to the association object information stored at the end of the object's serialized data.

The file format has changed in 2021, so assets that might have worked before might hit this situation at upgrade time. For example previously "id" was used and now "rid" is used instead (but we maintain code to read the old format as well). The string "references" also has special meaning so might conflict if there is a field of that name.

Does that seem like a possibility in any of the scripting objects in your project?

 

I would suggest looking at the YAML format for a MonoBehaviour and ScriptableObject that has at least one SerializeReference field, that is one way to see all the internal fields and the names that Unity uses. E.g inside a .unity or .asset file. There are the internal fields which don't change very much, and then there is the structure that only appears when SerializeReference is being serialized and which i think only involves "id", "rid" and "references" as possibly conflicting names. It is that second part that changed a bit for this version and seems to be causing you upgrade trouble.

We do have some errors/warnings that try to catch conflicts with internal field names, but I'm not sure your case is being detected and warned about. Its possible that "id" was working ok before, despite being also used internally, but has now started to cause confusion for the code that is trying to upgrade the class to the new format. Please let us know how things go.

 

BTW Jake_Card, i was curious if you ever pinpointed any further detail about the Serialization errors you hit. I've tried to see if i could reproduce those errors by creating objects in 2020 with "id" and "rid" fields. But those seem to load fine between 2020 and 2021 (with YAML format ScriptableObject assets). The closest we have seen to that error was with JSONUtility in the past, which was why I suggested it might be a possible conflict. Hopefully you have found a workaround, one way or another, but we are always on the lookout for compatibility or upgrade issues. Thanks