What s the status on null values in protobuf right now If I | Serialization | Kotlinlang

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#serialization

Paul Woitaschek

Paul Woitaschek

2 years ago

What's the status on null values in protobuf right now? If I get it correctly protobuf 3 is capable of null values?

gildor

gildor

2 years ago

Isn’t all values in protobuf are essentially nullable (the only way to support full backward compatibility)?

they can be non-nullable only if have default value

Paul Woitaschek

Paul Woitaschek

2 years ago

Well it seems null is not supported at all:

@Serializable
data class Test(
    @ProtoId(1)
    val type: String?,
    @ProtoId(2)
    val userId: String
)

fun main() {
    ProtoBuf.dump(Test.serializer(), Test(null, "b"))
}

This immediately throws an exception:

at kotlinx.serialization.internal.TaggedEncoder.encodeTaggedNull(Tagged.kt:37)
	at kotlinx.serialization.internal.TaggedEncoder.encodeNull(Tagged.kt:71)
	at kotlinx.serialization.Encoder$DefaultImpls.encodeNullableSerializableValue(Encoding.kt:260)
	at kotlinx.serialization.internal.TaggedEncoder.encodeNullableSerializableValue(Tagged.kt:22)
	at kotlinx.serialization.internal.TaggedEncoder.encodeNullableSerializableElement(Tagged.kt:124)
	at Test.write$Self(MessagePoly.kt)

gildor

gildor

2 years ago

Is it Proto2 or 3?

Paul Woitaschek

Paul Woitaschek

2 years ago

It's just the serialization library?

gildor

gildor

2 years ago

What do you mean? Null is supported in general

I clearly see proto annotation on data class

So you serialize/desereali3 it into Proto2?

Paul Woitaschek

Paul Woitaschek

2 years ago

Don't get it. How would I specify that?

gildor

gildor

2 years ago

As I know officially it supports Proto2 only

It proto3 may work, just not sure

Could you show whole stacktrace

Paul Woitaschek

Paul Woitaschek

2 years ago

Sure, but its completely self contained so you can just run it yourself:

Exception in thread "main" kotlinx.serialization.SerializationException: null is not supported
	at kotlinx.serialization.internal.TaggedEncoder.encodeTaggedNull(Tagged.kt:37)
	at kotlinx.serialization.internal.TaggedEncoder.encodeNull(Tagged.kt:71)
	at kotlinx.serialization.Encoder$DefaultImpls.encodeNullableSerializableValue(Encoding.kt:260)
	at kotlinx.serialization.internal.TaggedEncoder.encodeNullableSerializableValue(Tagged.kt:22)
	at kotlinx.serialization.internal.TaggedEncoder.encodeNullableSerializableElement(Tagged.kt:124)
	at Test.write$Self(protobug.kt)
	at Test$$serializer.serialize(protobug.kt)
	at Test$$serializer.serialize(protobug.kt:9)
	at kotlinx.serialization.protobuf.ProtoBuf$ProtobufWriter.encodeSerializableValue(ProtoBuf.kt:148)
	at kotlinx.serialization.EncodingKt.encode(Encoding.kt:402)
	at kotlinx.serialization.protobuf.ProtoBuf.dump(ProtoBuf.kt:541)
	at kotlinx.serialization.protobuf.ProtoBuf$Default.dump(ProtoBuf.kt)
	at ProtobugKt.main(protobug.kt:14)
	at ProtobugKt.main(protobug.kt)

gildor

gildor

2 years ago

You should enable nulls:

ProtoBuf(encodeDefaults = false)

Essentially protobuf doesn’t have concept of null, only optional with default value, so this flag just skip serialization of this null value

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