Original code by @JakeWharton, ported to Kotlin. Useful if you want to maintain insertion order of a Map before/after Moshi serialization.

LinkedHashMapAdapterFactory.kt

class LinkedHashMapAdapterFactory : Factory {
  override fun create(type: Type, annotations: MutableSet<out Annotation>,
      moshi: Moshi): JsonAdapter<*>? {
    if (Types.getRawType(type) != LinkedHashMap::class.java) {
      return null
    }
    if (type !is ParameterizedType) {
      throw IllegalStateException("Non-parameterized LinkedHashMap is not supported")
    }
    val keyType = type.actualTypeArguments[0]
    val valType = type.actualTypeArguments[1]
    val mapType = Types.newParameterizedType(Map::class.java, keyType, valType)
    val mapAdapter = moshi.adapter<Map<Any, Any>>(mapType)
    return object : JsonAdapter<LinkedHashMap<Any, Any>>() {
      override fun fromJson(reader: JsonReader): LinkedHashMap<Any, Any>? {
        return LinkedHashMap(mapAdapter.fromJson(reader))
      }

      override fun toJson(writer: JsonWriter, value: LinkedHashMap<Any, Any>?) {
        mapAdapter.toJson(writer, value)
      }
    }
  }
}