Ktor: GSON deserialization with non-nullable Kotlin type

[scorsi]

Ktor Version

1.0.1 but I think this bug also exists in 1.1.2

Only tested with GSON, may be Jackson is also affected.

Feedback

Already noticed in #157. The nullable Kotlin type is not taken into account by the GSON deserialization.
Kotlin Data class:

data class Something(val value: String)

Data in HTTP:

{}

Result:

Something(value=null)

Actual workaround:

We have to add the nullable property on all data class fields.

Expecting result:

If any non-nullable field is not fulfilled, the deserialization should return null (or throw if <T> receiveOrNull() is not used).

[e5l]

Hi @scorsi, thanks for the report.
It's obviously a bug and we'll fix it in the next release.

[e5l]

It looks like we need this done to perform the null check: https://github.com/google/gson/issues/445
You also could add zero argument constructor as a workaround.

[abubics]

Just fyi, also affects Jackson :)

Current workaround:

suspend inline fun <reified T : Any> ApplicationCall.safeReceiveOrNull(): T? = try {
  receiveOrNull()
} catch (e: Exception) {
  null
}

[oleg-larshin]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.