If the value wrapped in `value class` is `null`, it is not excluded from serialization

[lukaszsuski]

Describe the bug
If a Dto contains fields of value class type and the value is null, it is not excluded from serialization with @JsonInclude(JsonInclude.Include.NON_NULL).
The only working workaround I've found is to use JsonInclude.Include.CUSTOM with valueFilter { object == null }

Version information
2.14.2

To Reproduce

@JvmInline
value class Wrapped(val rawValue: String)

@JsonInclude(JsonInclude.Include.NON_NULL)
data class NonNullDto (
    val string: String? = null,
    val wrapped: Wrapped? = null,
)

@JsonInclude(JsonInclude.Include.CUSTOM, valueFilter = NullFilter::class)
data class CustomDto (
    val string: String? = null,
    val wrapped: Wrapped? = null,
)

class NullFilter {
    override fun equals(other: Any?) = other == null
}

@Test
fun `should not serialize null values with NonNull`() {
    println(jackson.writeValueAsString(NonNullDto()))
    println(jackson.writeValueAsString(CustomDto()))
}

Result for NonNullDto:
{"wrapped":null}
Result for CustomDto:
{}

Expected behavior
JsonInclude.Include.NON_NULL should exclude null values for kotlin value classes.

Additional context
Kotlin version: 1.8.10

[cowtowncoder]

Wrong issue tracker, will transfer.

[k163377]

@tmdgusya
Could you please check if jackson-module-kogera fixes the problem?
https://github.com/ProjectMapK/jackson-module-kogera

If it seems to be fixed, I will introduce the changes to jackosn-module-kotlin.

[tmdgusya]

@k163377 oh thank you

[cowtowncoder]

@tmdgusya Does this mean that Kogera does fix the issue?

[tmdgusya]

@cowtowncoder I haven't checked yet.

[k163377]

I checked with kogera and it seems to work to some extent.
However, there was a problem when the value wrapped in value class was null.

import com.fasterxml.jackson.annotation.JsonInclude
import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper

class JsonIncludeNonNullTest {
    @JvmInline
    value class Primitive(val v: Int)

    @JvmInline
    value class NonNullObject(val v: String)

    @JvmInline
    value class NullableObject(val v: String?)

    @JsonInclude(value = JsonInclude.Include.NON_NULL, content = JsonInclude.Include.NON_NULL)
    data class Dto(
        val pN: Primitive? = null,
        val nnoN: NonNullObject? = null,
        val noNn: NullableObject = NullableObject(null),
        val noN1: NullableObject? = null,
        val noN2: NullableObject? = NullableObject(null),
        val map: Map<Any, Any?> = mapOf("no" to NullableObject(null))
    )

    @Test
    fun test() {
        val mapper = jacksonObjectMapper()
        val dto = Dto()
        println(mapper.writeValueAsString(dto)) // -> {"noNn":null,"noN2":null,"map":{"no":null}}
    }
}

This problem is caused by JsonInclude being ignored when getting and writing findNullValueSerializer with JsonSerializer::serialize.
Unfortunately, I have not found a solution to this problem.

Alternatively, there may be room to interpret this as "the value on Kotlin is serialized because it is nonnull".