Scala 3: Exception returning Future values from GraphQL Endpoint

[PsyfireX]

When attempting to return values from a GraphQL endpoint using Sangria and Scala 3, I get the following exception:

    @GraphQLField
    def ping(in: String): Future[String] = {
      implicit val ec: scala.concurrent.ExecutionContext = scala.concurrent.ExecutionContext.global
      Future.apply(in)
    }

"class scala.concurrent.impl.Promise$Transformation cannot be cast to class java.lang.String (scala.concurrent.impl.Promise$Transformation is in unnamed module of loader 'app'; java.lang.String is in module java.base of loader 'bootstrap') 
 java.lang.ClassCastException: class scala.concurrent.impl.Promise$Transformation cannot be cast to class java.lang.String (scala.concurrent.impl.Promise$Transformation is in unnamed module of loader 'app'; java.lang.String is in module java.base of loader 'bootstrap') 
 sangria.execution.Resolver.resolveValue(Resolver.scala:1274) 
 sangria.execution.Resolver.$anonfun$20(Resolver.scala:813) 
 scala.collection.immutable.Vector1.map(Vector.scala:1872) 
 scala.collection.immutable.Vector1.map(Vector.scala:375) 
 sangria.execution.Resolver.resolveActionsPar(Resolver.scala:1113) 
 sangria.execution.Resolver.resolveFieldsPar(Resolver.scala:49) 
 sangria.execution.Executor.executeOperation(Executor.scala:275) 
 sangria.execution.Executor.$anonfun$5$$anonfun$2$$anonfun$1$$anonfun$1$$anonfun$1(Executor.scala:206) 
 scala.concurrent.impl.Promise$Transformation.run(Promise.scala:470) 
 java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) 
 java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) 
 java.base/java.lang.Thread.run(Thread.java:834)"

I am able to successfully get a schema from the running GraphQL server.

Since this particular error relies on having a running GraphQL server, it'll be a little difficult for me to create a miniature isolated code sample. I might make an attempt at creating an isolated sample, but that would take some time. If you cannot reproduce, let me know here on the ticket. (I'll try to monitor the ticket).

---

It appears to only happen when returning a Future. The following returns just fine.

    @GraphQLField
    def ping2(in: String): String = {
      in
    }

[muuki88]

Error messages sound aweful familiar to #449

[mprevel]

Hi,

Is there a known cause or a workaround for this issue? I guess I'm encountering it on a project that I am upgrading to Scala 3.
The issue seems to appear when the returned value is inside a Future (returning the String directly is OK).

On a case class body I add:

  @GraphQLField
  @GraphQLName("myString")
  def graphqlMyString: Future[String] = Future.successful("Hello World")

A unit test breaks with:

java.lang.ClassCastException: class scala.concurrent.impl.Promise$DefaultPromise cannot be cast to class java.lang.String (scala.concurrent.impl.Promise$DefaultPromise is in unnamed module of loader 'app'; java.lang.String is in module java.base of loader 'bootstrap')
      at sangria.execution.FutureResolver.resolveValue(FutureResolver.scala:1423)
      at sangria.execution.FutureResolver.resolveValue(FutureResolver.scala:960)
      at sangria.execution.FutureResolver.resolveStandardLeafAction(FutureResolver.scala:925)
      at sangria.execution.FutureResolver.resolveLeafAction(FutureResolver.scala:903)
      at sangria.execution.FutureResolver.$anonfun$20(FutureResolver.scala:831)
      at scala.collection.immutable.Vector1.map(Vector.scala:2140)
      at scala.collection.immutable.Vector1.map(Vector.scala:385)
      at sangria.execution.FutureResolver.resolveActionsPar(FutureResolver.scala:827)
      at sangria.execution.FutureResolver.resolveValue(FutureResolver.scala:1482)
      at sangria.execution.FutureResolver.$anonfun$28(FutureResolver.scala:1156)
      at scala.concurrent.impl.Promise$Transformation.run(Promise.scala:467)
      at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1395)
      at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373)
      at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
      at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
      at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
      at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)

[yanns]

I'm not aware of any fixes for this issue for now.
Would you want to invest some time on it?
You could first open a PR with a test reproducing the issue.
Then we could discuss how to fix this.

[robberthcz]

I encountered the same error today while migrating our project to Scala 3.

[yanns]

I'd encourage all people having this issue to try helping on the PR #1168