STMRollbackTest.scala

object STMRollbackTest extends App {
  import scala.concurrent.stm._
  val r = Ref(0)

  def trouble() = atomic { implicit tx =>
    println("a: " + r())
    r() = 2
    println("b: " + r())

    Txn.afterRollback { status =>
      println(s"ROLLBACK $status")
    }

    throw new Exception()
  }

  def a() = {
    println("A")
    atomic { implicit tx =>
      println("A ATOMIC")
      r() = 1
      val res = try {
        println("TROUBLE:")
        trouble()
      } catch { case e: Exception =>
        println("CATCH")
        r()
      }
      println("RES")
      res
    }
  }

  println("c: " + a())

  /* observed output:

A
A ATOMIC
TROUBLE:
a: 1
b: 2
ROLLBACK RolledBack(OptimisticFailureCause('restart_to_enable_partial_rollback,Some(java.lang.Exception)))
A ATOMIC
TROUBLE:
a: 1
b: 2
ROLLBACK RolledBack(UncaughtExceptionCause(java.lang.Exception))
CATCH
RES
c: 1
   */
}