Nested classes in ProtoBuf produce empty array for native release binary

[whyoleg]

Describe the bug

Nested classes in ProtoBuf produce empty array for native release binary.
No such issue with Cbor or with any other target and Native debug binary. (all cases are provided in repository with reproducer)

To Reproduce

@Serializable
data class OuterClass(val data: InnerClass)

@Serializable
data class InnerClass(val data: String)

@OptIn(ExperimentalSerializationApi::class, ExperimentalStdlibApi::class)
class SerializationTest {
    @Test
    fun testProtobufNested() {
        val model = OuterClass(InnerClass("something"))

        val data = ProtoBuf.encodeToByteArray(OuterClass.serializer(), model)
        // `data` is an empty array on Native in release mode
        assertEquals("0a0b0a09736f6d657468696e67", data.toHexString()) 
    }
}

Repository with reproducer: https://github.com/whyoleg/kx-serialization-protobuf-reproducer
To reproduce: ./gradlew macosArm64ReleaseTest or [TARGET_NAME]ReleaseTest for other targets, or just check to run all tests (to compare behaviour)

Expected behavior

Correct serialised value is returned independent to the target or debug/release mode.

Environment

• Kotlin version: 1.9.23 (same for 2.0.0-Beta5)
• Library version: 1.6.3
• Kotlin platforms: Native

Note: I can create the same issue in Kotlin YT, as most likely the issue is there, but thought it would be better to create it here to keep track and may be introduce some kind of tests in repository.

[sandwwraith]

Thanks for report. It happens for me for both linuxX64ReleaseTest on Linux machine and macosArm64ReleaseTest on Apple Silicon machine. Looks like the Native issue though.

[sandwwraith]

Closed in favor of https://youtrack.jetbrains.com/issue/KT-67218/Native-nested-classes-in-kx.serialization-ProtoBuf-produce-empty-array-for-release-binary

[whyoleg]

just in case: does it make sense additionally run tests in RELEASE mode (and possibly in other kotlinx.* libraries), to be proactive with such bugs?
If you think it could be useful, I'm ready to provide PR.

[sandwwraith]

Yes, it makes sense. I'll ask Native team additionally of the best way to do so. We are now refactoring our build scripts (#2654), so you'll have to wait with your PR a little bit :)

[whyoleg]

okay! Thanks, I will wait for #2654.
At my side I have the following build setup for runnings native tests in release mode. (BTW, this is how I've found this issue)
Created tasks will look like macosArm64ReleaseTest in addition to macosArm64Test (same for other targets) and will be automatically registered to run on check/allTests (I haven't looked on TC setup, so not sure what is needed there).