Fix completions (#2004)

modules/cli/src/main/scala/scala/cli/commands/ScalaCommand.scala

@@ -315,13 +315,9 @@ abstract class ScalaCommand[T <: HasGlobalOptions](implicit myParser: Parser[T],
       sys.exit(1)
     }
 
-  private val globalOptionsAtomic: AtomicReference[Option[GlobalOptions]] =
-    new AtomicReference(None)
-  private def globalOptions: GlobalOptions = globalOptionsAtomic.get() match
-    case Some(opts) => opts
-    case None => // should never happen
-      System.err.println("Failed to initialize the global options.")
-      sys.exit(1)
+  private val globalOptionsAtomic: AtomicReference[GlobalOptions] =
+    new AtomicReference(GlobalOptions.default)
+  private def globalOptions: GlobalOptions = globalOptionsAtomic.get()
   override def shouldSuppressExperimentalFeatureWarnings: Boolean =
     globalOptions.globalSuppress.suppressExperimentalFeatureWarning
       .orElse {
@@ -333,7 +329,7 @@ abstract class ScalaCommand[T <: HasGlobalOptions](implicit myParser: Parser[T],
   override def logger: Logger = globalOptions.logging.logger
 
   final override def main(progName: String, args: Array[String]): Unit = {
-    globalOptionsAtomic.set(GlobalOptions.get(args.toList))
+    globalOptionsAtomic.set(GlobalOptions.get(args.toList).getOrElse(GlobalOptions.default))
     super.main(progName, args)
   }
 

modules/cli/src/main/scala/scala/cli/commands/shared/GlobalOptions.scala

@@ -13,6 +13,8 @@ object GlobalOptions {
   implicit lazy val parser: Parser[GlobalOptions] = Parser.derive
   implicit lazy val help: Help[GlobalOptions]     = Help.derive
 
+  lazy val default: GlobalOptions = GlobalOptions()
+
   def get(args: List[String]): Option[GlobalOptions] =
     parser
       .detailedParse(args, stopAtFirstUnrecognized = false, ignoreUnrecognized = true)

modules/integration/src/test/scala/scala/cli/integration/CompleteTests.scala

@@ -0,0 +1,20 @@
+package scala.cli.integration
+
+import com.eed3si9n.expecty.Expecty.expect
+
+import scala.util.Properties
+
+class CompleteTests extends ScalaCliSuite {
+
+  test("simple") {
+    TestInputs.empty.fromRoot { root =>
+      val res = os.proc(TestUtil.cli, "complete", shellFormat, "2", "com").call(cwd = root)
+      expect(res.exitCode == 0)
+      expect(res.out.trim().nonEmpty)
+    }
+  }
+
+  def shellFormat: String =
+    if (Properties.isMac) "zsh-v1"
+    else "bash-v1"
+}