Add a consoleScalacOptions target

[mrdziuban]

This will allow users to specify the exact set of scalac options that are used in the console

[mrdziuban]

The CI failure seems unrelated to these changes but let me know if there's something I can do to resolve it

Never mind, there's no CI failure 😄

[lefou]

Should we move the currently hardcoded -usejavacp into the consoleScalacOptions?

[mrdziuban]

I'm not sure -- is it required for the console to work? If so, then I would say no, as it would let users remove it

[lefou]

I couldn't find enough information whether it is always neeed, but at least, there is a -usemanifestcp option in scalac, which looks like an alternative to me. And if someone wants to use it, she needs a way to remove the default.

I also think overriding a target while also re-using the super value is a rather common thing in Mill and would be ok here.

def consoleScalacOptions = super.consoleScalacOptions() ++ scalacOptions().filterNot(o => o == "-Xfatal-warnings")

Lastly, I think you should avoid the distinct, since it may break cli options that accept additional params, which are identical like Seq("-Xmaxerrs", "100", "-Xmaxwarns", "100"). A .distinct will remove the second "100".

[mrdziuban]

Good call on distinct, I've removed that. And your logic about -usejavacp makes sense, I've moved it to consoleScalacOptions

[mrdziuban]

Actually @lefou, it looks like -usejavacp is required. Without it, I get the error below. So do you think it makes sense to keep it hardcoded in the console command?

Welcome to Scala 2.13.12 (OpenJDK 64-Bit Server VM, Java 17.0.8).
Type in expressions for evaluation. Or try :help.

Failed to initialize compiler: object scala in compiler mirror not found.
** Note that as of 2.8 scala does not assume use of the java classpath.
** For the old behavior pass -usejavacp to scala, or if using a Settings
** object programmatically, settings.usejavacp.value = true.
Exception in thread "main" java.lang.NullPointerException: Cannot throw exception because "null" is null
	at scala.tools.nsc.CompilationUnits$CompilationUnit.<init>(CompilationUnits.scala:43)
	at scala.tools.nsc.CompilationUnits$CompilationUnit.<init>(CompilationUnits.scala:44)
	at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.compile(IMain.scala:743)
	at scala.tools.nsc.interpreter.IMain.bind(IMain.scala:562)
	at scala.tools.nsc.interpreter.IMain.bind(IMain.scala:598)
	at scala.tools.nsc.interpreter.IMain.$anonfun$quietBind$1(IMain.scala:597)
	at scala.tools.nsc.interpreter.shell.ReplReporterImpl.withoutPrintingResults(Reporter.scala:63)
	at scala.tools.nsc.interpreter.IMain.quietBind(IMain.scala:597)
	at scala.tools.nsc.interpreter.shell.ILoop.interpretPreamble(ILoop.scala:940)
	at scala.tools.nsc.interpreter.shell.ILoop.$anonfun$run$3(ILoop.scala:981)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
	at scala.tools.nsc.interpreter.shell.ILoop.echoOff(ILoop.scala:94)
	at scala.tools.nsc.interpreter.shell.ILoop.$anonfun$run$2(ILoop.scala:981)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
	at scala.tools.nsc.interpreter.IMain.withSuppressedSettings(IMain.scala:1428)
	at scala.tools.nsc.interpreter.shell.ILoop.$anonfun$run$1(ILoop.scala:972)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
	at scala.tools.nsc.interpreter.shell.ReplReporterImpl.withoutPrintingResults(Reporter.scala:63)
	at scala.tools.nsc.interpreter.shell.ILoop.run(ILoop.scala:972)
	at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:88)
	at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:92)
	at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:105)
	at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:113)
	at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
1 targets failed
predef[2].console java.lang.Exception: Interactive Subprocess Failed (exit code 1)
    mill.util.Jvm$.runSubprocess(Jvm.scala:184)
    mill.util.Jvm$.runSubprocessWithBackgroundOutputs(Jvm.scala:152)
    mill.util.Jvm$.runSubprocess(Jvm.scala:88)
    mill.scalalib.ScalaModule.$anonfun$console$2(ScalaModule.scala:444)
    scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
    scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
    scala.Console$.withErr(Console.scala:193)
    mill.api.SystemStreams$.$anonfun$withStreams$2(SystemStreams.scala:62)
    scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
    scala.Console$.withOut(Console.scala:164)
    mill.api.SystemStreams$.$anonfun$withStreams$1(SystemStreams.scala:61)
    scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
    scala.Console$.withIn(Console.scala:227)
    mill.api.SystemStreams$.withStreams(SystemStreams.scala:60)
    mill.scalalib.ScalaModule.$anonfun$console$1(ScalaModule.scala:449)
    mill.define.Task$TraverseCtx.evaluate(Task.scala:71)

[lefou]

Yeah, let's keep it there, then. We can handle it once there is a real need for it. Thanks for checking!

[mrdziuban]

👍 done!

[lefou]

I noticed the analog repl command accepts it's options via command arguments. Should we follow the same in console?

And if, do we still need a consoleScalacOptions target?

[mrdziuban]

I think having console take command arguments may lead to a worse user experience, at least for the use case I'm trying to solve for. To achieve what I described in the docs -- using all the same scalacOptions except for -Xfatal-warnings -- a user would have to either:

1. Pass all the scalacOptions on the command line
2. Override the console command to call super.console with the correct default set of options

Maybe a hybrid of the two is worth exploring for both repl and console? i.e. something like this:

// `consoleScalacOptions` are ones that are always passed to the console
def consoleScalacOptions: T[Seq[String]] = T(Seq.empty[String])

// `consoleOptions` are ad-hoc options the user can pass on the command line
def console(consoleOptions: String*): Command[Unit] = T.command {
  // ...
  mainArgs = (Seq("-usejavacp") ++ consoleScalacOptions() ++ consoleOptions).distinct
  // ...
}

[lefou]

Looks good to me. Thank you!