Support new jackson feature @JsonMerge

[deblockt]

I have test @JsonMerge on a scala Map.
The merge doesn't work.
did you work on a merge support?

[nbauernfeind]

Can you provide a code snippet, describe what happens and what you expect to happen?

Thanks!

[deblockt]

I have write a code sample who perform same action with Scala Map and Java Map to show differences.

import java.util

import com.fasterxml.jackson.annotation.JsonMerge
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.scala.DefaultScalaModule

import scala.collection.mutable
import scala.collection.JavaConverters._

object Main extends App {

  class MergeJavaTest(inputMap: java.util.Map[String, String]) {
    @JsonMerge var map: java.util.Map[String, String] = inputMap
  }

  class MergeScalaTest(inputMap: mutable.Map[String, String]) {
    @JsonMerge var map: mutable.Map[String, String] = inputMap
  }

  val inputTest =
    """
      |{
      | "map": {
      |   "foo": "test"
      | }
      |}
    """.stripMargin

  val map = mutable.Map("bar" -> "test")
  val existingJavaMap = new MergeJavaTest(map.asJava)
  val existingScalaMap = new MergeScalaTest(map)

  val objectMapper = new ObjectMapper().registerModule(DefaultScalaModule)

  val updatedJavaMap: MergeJavaTest = objectMapper.readerForUpdating(existingJavaMap).readValue(inputTest)
  val updatedScalaMap: MergeScalaTest = objectMapper.readerForUpdating(existingScalaMap).readValue(inputTest)

  println(existingJavaMap.map) // {foo=test, bar=test}
  println(existingScalaMap.map) // Map(foo -> test) expected Map(foo -> test, bar -> test)
}