vmorarian/scala-npe-value-class

Isolated example of nullable method + value class == NPE

Problem

Nullable method (may return null, for instance Java interop) with return type of value class may cause NullPointerException in specific cases.

NPE

Exception in thread "main" java.lang.NullPointerException
	at example.TestNPE$.$anonfun$main$2(TestNPE.scala:17)
	at example.TestNPE$.$anonfun$main$2$adapted(TestNPE.scala:17)
	at scala.Option.map(Option.scala:146)
	at example.TestNPE$.main(TestNPE.scala:17)
	at example.TestNPE.main(TestNPE.scala)

Generated code

 // TestNPE.scala
package example {
  object TestNPE extends Object {
    def main(args: Array[String]): Unit = {
      val target: npe.Target = new npe.Target();
      val keyO: Option = scala.Option.apply("key");
      keyO.flatMap({
        ((k: String) => TestNPE.this.$anonfun$main$1(target, k))
      });
      {
        keyO.map({
          {
            ((k: String) => TestNPE.this.$anonfun$main$2(target, k))
          }
        }).flatMap({
          {
            ((x: String) => TestNPE.this.$anonfun$main$3(x))
          }
        });
        ()
      }
    };
    final <artifact> private[this] def $anonfun$main$1(target$1: npe.Target, k: String): Option = scala.Option.apply(target$1.operationNullable(k));
    final <artifact> private[this] def $anonfun$main$2(target$1: npe.Target, k: String): String = target$1.operationNullable(k).$asInstanceOf[example.Value]().underlying();
    final <artifact> private[this] def $anonfun$main$3(x: String): Option = scala.Option.apply(new example.Value(x));
    def <init>(): example.TestNPE.type = {
      TestNPE.super.<init>();
      ()
    }
  }
}