Json error parsing into case class, json array

Question

I am trying to parse this json object and I ran a unit test and I got this error Error: Error when parsing result of 'listdescriptors': {"obj":[{"msg":["error.expected.jsarray"],"args":[]}]}! [info] at org.bitcoins.rpc.client.common.Client.parseResult(Client.scala:455). I think the problem may be that I'm parsing the json file into a case class incorectly.

Result:
{                                 (json object)
  "wallet_name" : "str",          (string) Name of wallet this operation was performed on
  "descriptors" : [               (json array) Array of descriptor objects
    {                             (json object)
      "desc" : "str",             (string) Descriptor string representation
      "timestamp" : n,            (numeric) The creation time of the descriptor
      "active" : true|false,      (boolean) Activeness flag
      "internal" : true|false,    (boolean, optional) Whether this is an internal or external descriptor; defined only for active descriptors
      "range" : [                 (json array, optional) Defined only for ranged descriptors
        n,                        (numeric) Range start inclusive
        n                         (numeric) Range end inclusive
      ],
      "next" : n                  (numeric, optional) The next index to generate addresses from; defined only for ranged descriptors
    },
    ...
  ]
}

object JsonSerializers {

implicit val descriptorsClassReads: Reads[descriptorsClass] =
    Json.reads[descriptorsClass]

  implicit val listDescriptorsReads: Reads[listDescriptorsResult] =
    Json.reads[listDescriptorsResult]

sealed abstract class WalletResult

case class listDescriptorsResult(
    wallet_name: String,
    descriptors: Vector[descriptorsClass]
) extends WalletResult

case class descriptorsClass(
    desc: String,
    timestamp: ZonedDateTime,
    active: Boolean,
    internal: Boolean,
    range: Array[(Int, Int)],
    next: Int
) extends WalletResult

You should not use Array as case class field, as it's mutable, and so violate the immutability contract of case class. Class should not be named with an initial lowercase as descriptorClass. Instead of an empty abstract class, rather use a trait. There is no need to violate the Scala naming to support snake_case naming in the JSON representation. — cchantep
– cchantep, Commented Jul 16, 2022 at 11:45

sparker · Accepted Answer · 2022-07-17 09:13:15Z

Here is a working example without the ZonedDateTime. It is probably better to have it represented as a Long in case class and convert it to ZonedDateTime later only when you need to represent it as ZonedDateTime

import play.api.libs.json.{Json, Reads, Writes}

sealed abstract class WalletResult

case class ListDescriptorsResult(
                                  wallet_name: String,
                                  descriptors: Seq[DescriptorsClass]
                                ) extends WalletResult

case class DescriptorsClass(
                             desc: String,
                             timestamp: Long,
                             active: Boolean,
                             internal: Boolean,
                             range: (Int, Int),
                             next: Int
                           ) extends WalletResult


implicit val descriptorsClassReads: Reads[DescriptorsClass] = 
  Json.reads[DescriptorsClass]
implicit val listDescriptorsResultReads: Reads[ListDescriptorsResult] = 
  Json.reads[ListDescriptorsResult]

val jsonString =
  """
    |{
    |  "wallet_name" : "str",
    |  "descriptors" : [
    |    {
    |      "desc" : "desc1",
    |      "timestamp" : 1657920976,
    |      "active" : true,
    |      "internal" : true,
    |      "range" : [
    |        10,
    |        20
    |      ],
    |      "next" : 10
    |    },
    |    {
    |      "desc" : "desc2",
    |      "timestamp" : 1657920976,
    |      "active" : true,
    |      "internal" : false,
    |      "range" : [
    |        30,
    |        40
    |      ],
    |      "next" : 20
    |    }
    |  ]
    |}
    |
""".stripMargin.replaceAll("\n","")

val jsValue = Json.parse(jsonString)

println(Json.fromJson[ListDescriptorsResult] (jsValue).get)

Here is the code in a scastie editor

Think it will be better to paste full answer to SO. Other resources can be unavailable via few months/years. Also it is common practice on SO.

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