List serialization doesn't work with protobuf

[Aschraf]

Serializing a list of objects succeeds in JSON and fails with Protobuf

fun main(args: Array<String>) {
  val list = listOf(Foo("a"), Foo("b"))

  println(JSON.stringify(Foo.serializer().list, list))
  println(ProtoBuf.dump(Foo.serializer().list, list))
}

@Serializable
data class Foo(@SerialId(1) val foo: String)

With the following error:

Exception in thread "main" java.util.NoSuchElementException: List is empty.
	at kotlin.collections.CollectionsKt___CollectionsKt.last(_Collections.kt:341)
	at kotlinx.serialization.TaggedOutput.getCurrentTag(Tagged.kt:163)
	at kotlinx.serialization.protobuf.ProtoBuf$ProtobufWriter.writeBegin(ProtoBuf.kt:47)
	at kotlinx.serialization.KOutput.writeBegin(Serialization.kt:163)
	at kotlinx.serialization.internal.ListLikeSerializer.save(CollectionSerializers.kt:45)
	at kotlinx.serialization.KOutput.write(Serialization.kt:99)
	at kotlinx.serialization.protobuf.ProtoBuf.dump(ProtoBuf.kt:415)
	at kotlinx.serialization.protobuf.ProtoBuf$Companion.dump(ProtoBuf.kt:403)
	at MainClassKt.main(MainClass.kt:21)

[sandwwraith]

As far as I know, protobuf doesn't have a concept of "root-level list". There are no lists at all, just repeated objects with the same Tag. In your case, tag for Foo is not specified (and can't be). The easiest workaround for that is just wrap your list in some object and specify SerialId for it.

[JakeWharton]

Root-level lists usually refer to delimited messages which are tagless, length-prefixed messages. They're almost always used for streaming, though, and not with buffered data.

[Aschraf]

That's exactly what I'm doing for now (wrapping the list in an object).
I misunderstood the documentation and thought the Protobuf serialization would do that for me.
The exception was a little bit misleading as It gave me the impression of an issue with my list.