How to use fetchNewObject with update.one ReactiveMongo?

Previously I used findAndUpdate and could add fetchNewObject = true so I was able to do something like this after the query:

.map(_.result[WhicherReport].getOrElse {
  throw new NoSuchElementException
})

but I'm using transaction now and could only perform update.one(...) and there is no option to pass it fetchNewObject, what can I do?

This is my func:

  def someUpdateFunc(collection: BSONCollection, metadata: Metadata, ids: List[String]): Future[UpdateWriteResult] = {
    collection.update.one(
      q = Json.obj("metadata" -> metadata,
        notLocked(now)),
      u =  Json.obj("$set" -> Json.obj("expenses.$[elem].paired" -> true)),
      upsert = false,
      multi = false,
      arrayFilters = Seq(BSONDocument("elem.id" -> BSONDocument( "$in" -> ids))),
      collation = None)
  }

and I want to return the new updated case class using ReactiveMongo.

There is no way to use fetchNewObject with an update command, as it's not an option supported by this command.

You seems to think that findAndModify cannot be used with transaction, which not the case: it can be used with transaction.

for {
  ds <- db.startSession()
  dt <- ds.startTransaction(None)

  coll = dt.collection(colName)
  _ <- coll.findAndUpdate(selector, james, upsert = true)
} yield ...

If you still want to use update for unmentioned reason, then you will need to execute a find after, in the same transaction.

P.S. .getOrElse { throw new NoSuchElementException } is quite a code smell, which should be discouraged (and rather compose).