pass out the main module directly as top scope and make sure it is writable

Author: timfel

CHANGELOG.md

@@ -6,6 +6,7 @@ language runtime. The main focus is on user-observable behavior of the engine.
 ## Version 20.0.0 beta 2
 
 * Add `java.add_to_classpath` API to dynamically extend the host class path
+* Allow write access to main module bindings for embedder
 
 ## Version 20.0.0 beta 1
 

graalpython/com.oracle.graal.python.test/src/com/oracle/graal/python/test/interop/JavaInteropTest.java

@@ -501,6 +501,14 @@ public void accessJavaObjectGetters() throws IOException {
                             "True <class 'bool'>\n" +
                             "c <class 'str'>\n", out.toString("UTF-8"));
         }
+
+        @Test
+        public void writableBindings() {
+            context.getBindings("python").putMember("javaObj", 42);
+            Value javaObj = context.eval("python", "javaObj");
+            assertTrue(javaObj.isNumber());
+            assertEquals(javaObj.asInt(), 42);
+        }
     }
 
     @RunWith(Parameterized.class)

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/PythonLanguage.java

@@ -458,7 +458,7 @@ protected Iterable<Scope> findTopScopes(PythonContext context) {
         ArrayList<Scope> scopes = new ArrayList<>();
         if (context.getBuiltins() != null) {
             // false during initialization
-            scopes.add(Scope.newBuilder("__main__", scopeFromObject(context.getMainModule())).build());
+            scopes.add(Scope.newBuilder("__main__", context.getMainModule()).build());
             scopes.add(Scope.newBuilder("builtins", scopeFromObject(context.getBuiltins())).build());
         }
         return scopes;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/PythonAbstractObject.java

@@ -56,6 +56,7 @@
 import com.oracle.graal.python.builtins.objects.function.PKeyword;
 import com.oracle.graal.python.builtins.objects.ints.PInt;
 import com.oracle.graal.python.builtins.objects.list.PList;
+import com.oracle.graal.python.builtins.objects.module.PythonModule;
 import com.oracle.graal.python.builtins.objects.object.PythonBuiltinObject;
 import com.oracle.graal.python.builtins.objects.object.PythonObject;
 import com.oracle.graal.python.builtins.objects.str.PString;
@@ -675,7 +676,7 @@ public boolean isImmutable(Object object,
             // 'type'
             if (object instanceof PythonBuiltinClass || object instanceof PythonBuiltinObject || PGuards.isNativeClass(object) || PGuards.isNativeObject(object)) {
                 return true;
-            } else if (object instanceof PythonClass) {
+            } else if (object instanceof PythonClass || object instanceof PythonModule) {
                 return false;
             } else {
                 LazyPythonClass klass = getClass.execute(object);