Scala script runner crashes on a file with no statements

[scabug]

When scala script compiler/runner is invoked on an empty file,
or on a file with lines of code commented out, it fails to create the Main class (entry point into the script application),
but still decides to run the thing, so it promptly crashes.

{code:title=Script.scala|borderStyle=solid}
import sys.process._
import java.io.File

// "gzip" #< new File("Script.scala") #> new File("Script.scala.gz")!
// "zip" #< new File("Script.scala") #> new File("Script.zip")!
{code}

{panel}
C:>scala Script.scala
java.lang.ClassNotFoundException: Main (args = , classpath = ...)
at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:103)
at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:33)
at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:40)
at scala.tools.nsc.ScriptRunner.scala$tools$nsc$ScriptRunner$$runCompiled(ScriptRunner.scala:171)
at scala.tools.nsc.ScriptRunner$$anonfun$runScript$1.apply(ScriptRunner.scala:188)
at scala.tools.nsc.ScriptRunner$$anonfun$runScript$1.apply(ScriptRunner.scala:188)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1.apply$mcZ$sp(ScriptRunner.scala:157)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1.apply(ScriptRunner.scala:131)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1.apply(ScriptRunner.scala:131)
at scala.tools.nsc.util.package$.waitingForThreads(package.scala:26)
at scala.tools.nsc.ScriptRunner.withCompiledScript(ScriptRunner.scala:130)
at scala.tools.nsc.ScriptRunner.runScript(ScriptRunner.scala:188)
at scala.tools.nsc.ScriptRunner.runScriptAndCatch(ScriptRunner.scala:201)
at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:58)
at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:80)
at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:89)
at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
{panel}

This doesn't look like the proper way, the compiler should either

• create an empty Main procedure and run it, providing a valid error level 0 output in case this script was chained somewhere
• output something like "Nothing to compile", etc....

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-5254?orig=1
Reporter: @melezov
Affected Versions: 2.9.1, 2.11.2

[scabug]

Stas Shevchenko (stasimus) said:
Actually good place to fix is ScriptRunner, while for compiler it is OK to compile nothing, ScriptRunner should detect no classes to run, place for fix is mentioned bellow. In the details - we can implement def hasScriptMain(compiledPath:Directory, scriptMain:String), that will return true if {mainClassName}.class is inside compiled tmp directory. May be there is a better way - for example ask the compiler is scriptMain(settings: Settings) was compiled into class file.

private def withCompiledScript(
settings: GenericRunnerSettings,
scriptFile: String)
(handler: String => Boolean): Boolean =
{
...

def compile: Option[Directory] = {

...        
    if (reporter.hasErrors) None 
    else if (!hasScriptMain(compiledPath, scriptMain(settings))) throw new IOException("Nothing to compile")
    Some(compiledPath)
  }
  ...
}

[scabug]

@gourlaysama said:
scala/scala#3946