add a flag so we can easily test in multi-context mode

Author: timfel

graalpython/com.oracle.graal.python.shell/src/com/oracle/graal/python/shell/GraalPythonMain.java

@@ -44,6 +44,7 @@
 import org.graalvm.options.OptionCategory;
 import org.graalvm.polyglot.Context;
 import org.graalvm.polyglot.Context.Builder;
+import org.graalvm.polyglot.Engine;
 import org.graalvm.polyglot.PolyglotException;
 import org.graalvm.polyglot.PolyglotException.StackFrame;
 import org.graalvm.polyglot.Source;
@@ -73,14 +74,14 @@ public static void main(String[] args) {
     private boolean stdinIsInteractive = System.console() != null;
     private boolean runLLI = false;
     private boolean unbufferedIO = false;
+    private boolean multiContext = false;
     private VersionAction versionAction = VersionAction.None;
     private String sulongLibraryPath = null;
     private List<String> givenArguments;
     private boolean wantsExperimental = false;
 
     @Override
     protected List<String> preprocessArguments(List<String> givenArgs, Map<String, String> polyglotOptions) {
-
         ArrayList<String> unrecognized = new ArrayList<>();
         ArrayList<String> inputArgs = new ArrayList<>();
         inputArgs.addAll(givenArgs);
@@ -197,6 +198,13 @@ protected List<String> preprocessArguments(List<String> givenArgs, Map<String, S
                         unrecognized.add(arg);
                     }
                     break;
+                case "-multi-context":
+                    if (wantsExperimental) {
+                        multiContext = true;
+                    } else {
+                        unrecognized.add(arg);
+                    }
+                    break;
                 case "-dump":
                     if (wantsExperimental) {
                         subprocessArgs.add("Dgraal.Dump=");
@@ -374,6 +382,10 @@ protected void launch(Builder contextBuilder) {
         contextBuilder.option("python.TerminalWidth", Integer.toString(consoleHandler.getTerminalWidth()));
         contextBuilder.option("python.TerminalHeight", Integer.toString(consoleHandler.getTerminalHeight()));
 
+        if (multiContext) {
+            contextBuilder.engine(Engine.create());
+        }
+
         int rc = 1;
         try (Context context = contextBuilder.build()) {
             runVersionAction(versionAction, context.getEngine());