Mongo Integer ClassCastException issue

bug.scala

package the

import org.bson.codecs.configuration.CodecRegistries.fromRegistries
import org.mongodb.scala.MongoClient.DEFAULT_CODEC_REGISTRY
import org.mongodb.scala.bson.BsonInt64
import org.mongodb.scala.{Document, MongoClient}

import scala.concurrent.Await
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._

// SCALA-592
// https://jira.mongodb.org/browse/SCALA-592

object MongoIssue extends App {

  protected val mongoClient: MongoClient = MongoClient(s"mongodb://localhost:27017")

  private val coll =
    mongoClient.getDatabase("MyDB").withCodecRegistry(fromRegistries(DEFAULT_CODEC_REGISTRY)).getCollection[Document]("test_collection")

  //@formatter:off
  val p = for {
    inserted <- coll.insertOne(Document("field" -> BsonInt64(1L))).toFuture()
    _         = println(inserted)
    found    <- coll.find().head()
    _         = println(found)
    _         = println(found.getLong("field"))
  } yield found
  Await.result(p, 10.seconds)
  //@formatter:on

}

// Results in an exception:

/*
AcknowledgedInsertOneResult{insertedId=BsonObjectId{value=5fe089b45e52e211a27dc3a4}}
Document((_id,BsonObjectId{value=5fe089b45e52e211a27dc3a4}), (field,BsonInt64{value=1}))

Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long
	at org.bson.Document.getLong(Document.java:267)
	at the.MongoIssue$.$anonfun$p$4(MongoIssue.scala:25)
	at scala.util.Success.$anonfun$map$1(Try.scala:255)
	at scala.util.Success.map(Try.scala:213)
	at scala.concurrent.Future.$anonfun$map$1(Future.scala:292)
	at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:33)
	at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:33)
	at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
	at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:175)
*/

Root cause is described in the comments: https://jira.mongodb.org/browse/SCALA-592

As a temporary fix, fallback to native scala Document method get[BsonInt64].getValue and its friends. It would also avoid heavy implicit conversions to java Document via JSON