I saw some others threads about it but I did not find a solution in them.

Gson version

2.10.1

Java / Android version

Description

The real context

I have a sealed class (heritance from Throwable) who represent all errors in my app (~80 inner dataclass). Sometime I want to override "message" or "reason" in my "sub dataclass", but when i try to serialize it with, an error occurs.

A simple way to reproduce

    open class MyClass {
        open val a = 22
    }
    open class SubClass : MyClass() {
        override val a = 25
        val b = 12
    }

Expected behavior

When I serialize MyClass, i expect to have { "a" : 22 }
When I serialize SubClass, i expect to have { "a": 25, "b" : 12 }

Actual behavior

It cannot serialize SubClass, "JSON fields named 'a'; conflict is caused by fields ...". Also i tried handmade reflection on "SubClass" and i see "a" only one time. I guess you are using more complex mecanics.

Notes:

I can't change the class Throwable (or use annotation in them)
A can't make an adapter for all the 80 inner data class

I tried with Jackson json serialization and it works as expected

val mapper = ObjectMapper()
val json = mapper.writeValueAsString(SubClass())
println(json)

Output : {"a":25,"b":12}

Reproduction steps

Just run an unit test with the code below and call the methode Builder().toJson(SubClass())

Exception stack trace

Class com.organisation.app.MyUnitTest$SubClass declares multiple JSON fields named 'a'; conflict is caused by fields com.organisation.app.MyUnitTest$SubClass#a and com.organisation.app.MyUnitTest$MyClass#a
java.lang.IllegalArgumentException: Class com.organisation.app.MyUnitTest$SubClass declares multiple JSON fields named 'a'; conflict is caused by fields com.organisation.app.MyUnitTest$SubClass#a and com.organisation.app.MyUnitTest$MyClass#a
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:302)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:130)
    at com.google.gson.Gson.getAdapter(Gson.java:556)
    at com.google.gson.Gson.toJson(Gson.java:834)
    at com.google.gson.Gson.toJson(Gson.java:812)
    at com.google.gson.Gson.toJson(Gson.java:759)

google / gson

Gson cannot serialize subclass who override a field #2638