Fix non-zero exit code on error (#338)

build.sbt

@@ -121,6 +121,8 @@ lazy val effekt: CrossProject = crossProject(JSPlatform, JVMPlatform).in(file("e
 
     Compile / unmanagedResourceDirectories += (ThisBuild / baseDirectory).value / "licenses",
 
+    // cli flag so sbt doesn't crash when effekt does
+    addCommandAlias("run", "runMain effekt.Server --noexit-on-error"),
 
     assembleBinary := {
       val jarfile = assembly.value

effekt/jvm/src/main/scala/effekt/Driver.scala

@@ -35,7 +35,7 @@ trait Driver extends kiama.util.Compiler[EffektConfig, EffektError] { outer =>
    * If no file names are given, run the REPL
    */
   override def run(config: EffektConfig): Unit =
-    if (config.filenames().isEmpty && !config.server() && !config.compile()) {
+    if (config.repl()) {
       new Repl(this).run(config)
     // This is overridden by kiama.Server to launch the LSP server.
     // TODO: remove dynamic dispatch here and consider replacing inheritance by composition.
@@ -100,5 +100,9 @@ trait Driver extends kiama.util.Compiler[EffektConfig, EffektError] { outer =>
   def afterCompilation(source: Source, config: EffektConfig)(implicit C: Context): Unit = {
     // report messages
     report(source, C.messaging.buffer, config)
+
+    // exit with non-zero code if not in repl/server mode and messaging buffer contains errors
+    if (config.exitOnError() && C.messaging.hasErrors)
+      sys.exit(1)
   }
 }

effekt/jvm/src/main/scala/effekt/EffektConfig.scala

@@ -64,6 +64,13 @@ class EffektConfig(args: Seq[String]) extends REPLConfig(args) {
     noshort = true
   )
 
+  val exitOnError: ScallopOption[Boolean] = toggle(
+    "exit-on-error",
+    descrYes = "Exit with non-zero exit code on error",
+    default = Some(!repl() && !server()),
+    noshort = true
+  )
+
   /**
    * Tries to find the path to the standard library. Proceeds in the following
    * order:
@@ -121,6 +128,8 @@ class EffektConfig(args: Seq[String]) extends REPLConfig(args) {
 
   def interpret(): Boolean = !server() && !compile() && !build()
 
+  def repl(): Boolean = filenames().isEmpty && !server() && !compile()
+
   validateFilesIsDirectory(includePath)
 
   // force some other configs manually to initialize them when compiling with native-image