Deserialize empty protobuf list on iOS

[webfrea-k]

I have the following data class:

@Serializable
data class Test (
        @Optional @SerialId(1) var events: List<Event> = emptyList(),
        @Optional @SerialId(2) var games: List<Game> = emptyList()
)

Protobuf deserialization (proto3) works correctly on Android and iOS if both values are not empty. If at least one list property is empty (empty list), the deserialization fails on iOS with error: Unexpected EOF.

If empty property is commented out of data class, deserialization works on iOS as well.

[sandwwraith]

Hi, could you please give a sample of protobuf bytes so I could debug this? And definitions of Event and Game classes, too

[webfrea-k]

Unfortunately the only example producing this error has 28k+ bytes in the response (and the entire Test class is way bigger than just events and games too). But maybe my observations can help:

I've implemented custom deserializer for this class and debug the following while loop:

loop@ while (true) {
        when (val i = inp.decodeElementIndex(descriptor)) { ... }
}
inp.endStructure(descriptor)

Is it possible, that decodeElementIndex is somehow not incremented if the repeated field is empty and while loop eventually runs until EOF is thrown?

[sandwwraith]

Hm, do you use ktor client on ios? It could be possibly related to #360 , since errors occur only on big data

[webfrea-k]

You are correct! I managed to make the response shorter and data is indeed handled correctly on iOS as well.

• Max length working on both platforms (that I can re-produce): 96735 bytes
• Length working on android and not on iOS: 128153 bytes

[sandwwraith]

Kotlin/kotlinx-io#36 will fix this