Allow to use object as a script wrapper

[dacr]

Version(s)
Only from 1.0.0-RC2, everything is fine with previous releases.

Describe the bug
The script compile, then a *** RUN ABORTED*** message is printed
.

(Of course I could use the new test.dep and scl test myscript.sc approach but it should run as before the old way)

To Reproduce

• KO script :
  • https://gist.github.com/dacr/fa515384be730103dbd37e7b3815b58f

// ---------------------
//> using scala  "3.2.2"
//> using dep "org.scalatest::scalatest:3.2.15"
// ---------------------

import org.scalatest.*, flatspec.*, matchers.*

class PiTest extends AnyFlatSpec with should.Matchers {
  "pi calculus" should "return a precise enough pi value" in {
    math.Pi shouldBe 3.14158d +- 0.001d
  }
}
org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[PiTest].getName))

• OK script :
  • https://gist.github.com/dacr/78bb969a26d7394900396fd8ebd0142b

Expected behaviour
running fine without this error message and with this output :

[dacr]

In the KO script, if I change the way the test is started, it runs as expected :

//org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[PiTest].getName))
(new PiTest).execute()

[dacr]

This has probably a link with the classOf Operation, If I use the REPL I get :

$ scl --dep "org.scalatest::scalatest:3.2.15"
Welcome to Scala 3.2.2 (17.0.6, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                                                                                                                                                                       
scala> import org.scalatest.*, flatspec.*, matchers.*
     | 
                                                                                                                                                                                                                                                                                       
scala> class PiTest extends AnyFlatSpec with should.Matchers {
     |   "pi calculus" should "return a precise enough pi value" in {
     |     math.Pi shouldBe 3.14158d +- 0.001d
     |   }
     | }
     | 
// defined class PiTest
                                                                                                                                                                                                                                                                                       
scala> (new PiTest).execute()
rs$line$2$PiTest:
pi calculus
- should return a precise enough pi value
                                                                                                                                                                                                                                                                                       
scala> org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[PiTest].getName))
*** RUN ABORTED ***
  java.lang.ClassNotFoundException: rs$line$2$PiTest
  at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)

So using the REPL we can see that we got RUN ABORTED because of a ClassNotFoundException issue.

May be a classloader issue ? wrong parent classloader ? Something scalatest is doing that is no longer compatible with the new behavior of scala-cli ?

[dacr]

For your information I've automated the execution of most of my scripts using scala-cli, and with the latest release the failure has increased quite a lot :

results :

• 1.0.0-RC1 : 19 scripts KO (which requires some work at my side)
• 1.0.0-RC2 : 58 scripts KO, amount them
  • 36 RUN ABORTED message
    • all of them are using the org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[TestClass].getName)) :)

So the good news is that 264 scala-cli scripts are running fine, and I didn't see any other issue related to the scala-cli 1.0.0-RC2, all new failures are only related to the RUN ABORTED message.

Depending on your feedback on this issue, I'll keep them as they are or rewrite them to use the test.dep and scala-cli test xxx.sc.

I'll make more checks next week as I've some other specialized scripts I'm using at work...

[Gedochao]

It seems that the reason for this issue is the new script wrapper for Scala 3 scripts introduced in #2033.
The following replicates the problem on earlier versions:

Main.scala

//> using scala  "3.2.2"
//> using dep "org.scalatest::scalatest:3.2.16"

import org.scalatest.*, flatspec.*, matchers.*

class Outer {
  class PiTest extends AnyFlatSpec with should.Matchers {
    "pi calculus" should "return a precise enough pi value" in {
      math.Pi shouldBe 3.14158d +- 0.001d
    }
  }
}

object Main extends App {
  org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[Outer#PiTest].getName))
}

The problem seems to be the loading of the inner class.

scala-cli --cli-version 1.0.0-RC1 Main.scala
# *** RUN ABORTED ***

Needs further investigation on how can we address this.
We need the new wrapper to avoid deadlocks in scripts (see #532 & #1933).

BTW. the example in the REPL (given in #2117 (comment)) is actually replicable in earlier versions of Scala CLI and may be a separate issue.

[tgodzik]

Ok, so it seems there is no way around it unless we go back to the old behaviour (but that has issues with deadlocks, so I think it's more problematic) or we provide an additional using directive to use object. Neither approach is great but I would stay with the current approach.

In the meantime, I would however suggest using a normal Scala file in this case, sorry about the inconvenience.

We can leave this open to see if more people need this fixed (please react with +1).

[SethTisue]

fwiw, I agree that these deadlocks are so common and so pernicious that it's worth prioritizing avoiding them, even if it means compromising a bit elsewhere. the deadlock-proneness of the Scala 2 REPL, before we similarly switched to class-based wrappers in Scala 2.13.2, was reported on scala/bug and elsewhere about a million times over the years, and it was often language newcomers reporting it and getting a bad impression of Scala

(for evidence, see scala/bug#8119 and the various similar/duplicate tickets that are a link or two away)

cc @som-snytt

[MaciejG604]

You can now use --object-wrapper or using objectWrapper as a workaround for the mentioned problems.

[dacr]

Thanks for all, I've made all the necessary changes, and the results are good, the only remaining errors I have, are not related to scala-cli anymore, just some work in progress or networking issues :