CompatibleFieldSerializer throws IllegalArgumentException

[dalibegovic]

I assume the underlying problem is same as in: #774, but just to double check.

Version used is 5.0.0.

When we run:

class KryoSerializerDemo {
    public static void main(String[] args) {
        Kryo kryo = new Kryo();

        kryo.setRegistrationRequired(false);
        CompatibleFieldSerializer.CompatibleFieldSerializerConfig config = new CompatibleFieldSerializer.CompatibleFieldSerializerConfig();
        kryo.setDefaultSerializer(new SerializerFactory.CompatibleFieldSerializerFactory(config));

        Output output = new Output(4096, Integer.MAX_VALUE);
        kryo.writeClassAndObject(output, new Car(new Electric()));
        output.reset();
        kryo.writeClassAndObject(output, new Car(new Petrol()));
    }

    static class Car {
        private Motor motor;

        public Car(Motor motor) {
            this.motor = motor;
        }
    }

    interface Motor {

    }

    static class Electric implements Motor {
        private String range = "371km";
    }

    static class Petrol implements Motor {
        private int horsePower = 115;
    }
}

The output is:

Exception in thread "main" com.esotericsoftware.kryo.KryoException: java.lang.IllegalArgumentException: Can not set java.lang.String field KryoSerializerDemo$Electric.range to KryoSerializerDemo$Petrol
Serialization trace:
motor (KryoSerializerDemo$Car)
	at com.esotericsoftware.kryo.serializers.ReflectField.write(ReflectField.java:96)
	at com.esotericsoftware.kryo.serializers.CompatibleFieldSerializer.write(CompatibleFieldSerializer.java:107)
	at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:644)
	at KryoSerializerDemo.main(KryoSerializerDemo.java:17)
Caused by: java.lang.IllegalArgumentException: Can not set java.lang.String field KryoSerializerDemo$Electric.range to KryoSerializerDemo$Petrol
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
Caused by: java.lang.IllegalArgumentException: Can not set java.lang.String field KryoSerializerDemo$Electric.range to KryoSerializerDemo$Petrol

	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
	at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
	at java.base/java.lang.reflect.Field.get(Field.java:419)
	at com.esotericsoftware.kryo.serializers.CompatibleFieldSerializer.write(CompatibleFieldSerializer.java:93)
	at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:575)
	at com.esotericsoftware.kryo.serializers.ReflectField.write(ReflectField.java:86)
	... 3 more

After some debugging, the problem seems to be that when writing Car class with Petrol engine (second call), cached fields from first write call are returned here.

[theigl]

@dalibegovic: Thanks for the report. This is quite definitely a duplicate of #774. I'm still waiting for feedback from Nate and will address it ASAP.