Why I cannot debug a code in async block in intellij

[lahirug]

Anybody noticed this and found a workaround ?

[efiko12]

Yes I have the same problem, but It doesn't happen every time.

[pkolaczk]

I noticed this. Annoying as hell. Actually this is probably number 1 on my priority list. This and error handling.

[worldofprasanna]

Yes. Its very annoying. We used Play framework and everything is written within async block. It happens always for me.

[retronym]

I see that the IntelliJ Scala Plugin team has just added some support for scala-async to the debugger.

JetBrains/intellij-scala@64774de
JetBrains/intellij-scala@ff04b9f

The bug report, SCL-9039, seems the be reporting the same problem you're discussing here.

As a nice bonus, @niktrop seems to have added special support in "evaluate expression" so that local variables in the user-written code are retrieved from the corresponidng name-mangled fields of the state machine class. Thanks!

@niktrop Let me know if there is anything we can do in the macro to make your life easier here..

@lahirug @efiko12 @pkolaczk @worldofprasanna Thanks for your patience with this problem. Could I ask you to test out the latest nightly of the Scala Plugin (this requires use of IDEA 15) and report whether the situation is improved?

[niktrop]

There are some problems with availability of local variables and fields. Try this example:

object AsyncBugs {
  def main(args: Array[String]) {
    val future = async {
      val f1 = async { false }
      val f2 = async { 42 }
      if (await(f1))
        await(f2)
      else {
        "Hi" //breakpoint here
      }
    }

    Await.result(future, Duration.Inf)
  }
}

Field, generated for f2 is already null. And local variable f1 is not visible from the breakpoint location. I suppose wrong debug info for local variable table is generated.

[pkolaczk]

With the recent plugin I can put a breakpoint inside of async block and now it properly stops there. However, I noticed I can't step over await calls. Much better than before, but still needs more work.