Reserialization (FormerlySerializedAs) a field on MonoBehaviour in a namespace fails on prefab varia

I've posted a bug with as simple as example as I could (Case 1183879) - posting the issue here in case others have struggled with it or have a solution.

When attempting to reserialize (FormerlySerializedAs) a field on a monobehaviour that's defined inside a namespace any prefab variants that have that MonoBehaviour will fail to apply any serialized variant modifications - reverts to prefab source values

Effectively this means any namespace based MonoBehaviour on a prefab variant cannot change any serialized field names without losing the fields variant values invalidating the whole point of the variant.

Code (CSharp):

1.  
2. [Serializable]
3. public class TestObject
4. {
5.     public bool ForceReserialize;
6.     public bool MyValue;
7. }
8. namespace MyNamespace
9. {
10.     // fails on prefab variants
11.     public class TestClassInNamespace : MonoBehaviour
12.     {
13. #if !FORMERLY_SERIALIZED_AS
14.         public TestObject TestObject;
15. #else
16.         [FormerlySerializedAs("TestObject")]
17.         public TestObject TestObjectNewName;
18. #endif
19.     }
20. }

Code (CSharp):

1.  
2. [Serializable]
3. public class TestObject
4. {
5.     public bool ForceReserialize;
6.     public bool MyValue;
7. }
8. public class TestClass : MonoBehaviour
9. {
10. #if !FORMERLY_SERIALIZED_AS
11.     public TestObject TestObject;
12. #else
13.     [FormerlySerializedAs("TestObject")]
14.     public TestObject TestObjectNewName;
15. #endif
16. }

 

QA confirmed the bug (# 1183879) and it seems like a regression that's fairly pervasive affecting all prefab override values (prefab instances and prefab variants)

https://issuetracker.unity3d.com/is...-applied-in-a-class-in-a-nondefault-namespace