deep merge but respect arrays

deepMergeAndConcatArrays.scala

  private def extractNestedArray(
      json: Json
  ): Option[(NonEmptyList[String], Vector[Json])] = {

    def extractNestedArrayInternal(
        acum: List[String],
        json: Json
    ): Option[(NonEmptyList[String], Vector[Json])] =
      json.arrayOrObject(
        or = None,
        jsonArray = jsons => NonEmptyList.fromList(acum).map(_ -> jsons),
        jsonObject = _.toList.headOption.flatMap {
          case (k, v) =>
            extractNestedArrayInternal(k :: acum, v)
        }
      )

    extractNestedArrayInternal(Nil, json).map {
      case (keys, jsons) =>
        keys.reverse -> jsons
    }
  }

  private def concatArrayValueAtPath(
      json: Json,
      path: NonEmptyList[String],
      newValues: Vector[Json]
  ): Option[Json] =
    path
      .foldLeft[ACursor](
        json.hcursor
      ) {
        case (cursor, fieldName) =>
          cursor.downField(fieldName)
      }
      .withFocusM(
        _.asArray
          .map(_.appendedAll(newValues))
          .map(Json.fromValues)
      )
      .flatMap(_.top)

  implicit class jsonOps(json: Json) {
    def deepMergeAndConcatArrays(that: Json): Json =
      extractNestedArray(that)
        .flatMap {
          case (arrayPath, those) =>
            concatArrayValueAtPath(
              json = json,
              path = arrayPath,
              newValues = those
            )
        }
        .getOrElse(
          json.deepMerge(that)
        )
  }

extracted from https://gist.github.com/ShahOdin/cb16b6989ffc382d9962075fa7dba243 where I was trying to unflatten a json.