null value in HttpRequest.sendJson and HttpRequest.sendJsonable should be treated as json null

[gagarski]

Version

• vert.x core: 3.8.3
• vert.x web: 3.8.3

Let's consider the following code:

import io.vertx.core.Vertx
import io.vertx.core.json.JsonObject
import io.vertx.ext.web.client.HttpRequest
import io.vertx.ext.web.client.HttpResponse
import io.vertx.ext.web.client.WebClient
import io.vertx.kotlin.coroutines.awaitResult
import io.vertx.kotlin.coroutines.dispatcher
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch

fun <T> Vertx.runSuspend(block: suspend Vertx.() -> T): Unit =
    run {
        GlobalScope.launch(dispatcher()) {
            block()
        }
    }

/**
 * Actually a workaround. message has non-nullable type in Kotlin.
 */
suspend fun <T, U> HttpRequest<T>.sendJsonAwait(obj: U) =
    awaitResult<HttpResponse<T>> { sendJson(obj, it) }

/**
 * Actually a workaround. message has non-nullable type in Kotlin.
 */
suspend fun <T> HttpRequest<T>.sendJsonObjectAwait(obj: JsonObject?) =
    awaitResult<HttpResponse<T>> { sendJsonObject(obj, it) }

fun main() = Vertx.vertx().runSuspend {
    println(
        WebClient
            .create(this)
            .postAbs("http://example.com/")
            .sendJsonAwait(null)
            .body())
    println(
        WebClient
            .create(this)
            .postAbs("http://example.com/")
            .sendJsonObjectAwait(null)
            .body())
}

The result of both requests is HTTP error 411 (Length Required). Looking through the relevant vertx-web code I found out that there is one point where null values passed to send* methods of HttpRequest are handled: HttpContext.handleSendRequest(). In all cases they are treated as sending a request without body. However it does not seems like a right behavior in terms on JSON. There is null value in JSON which is represented by null Java value (in terms of Jackson and io.vertx.core.json). It seems like the right thing to do here is to send a body with null characters and having content length of 4. Otherwise to do it we need external handling of jsonable null values: creating Buffer.buffer("null"), setting content type manually and calling sendBuffer.

[vietj]

right, we should use a marker object for the body when sending null