allow walking not-yet-classloaded java packages during import

Author: timfel

graalpython/lib-graalpython/java.py

@@ -65,7 +65,8 @@ def __getattr__(key, default=None):
                         try:
                             return type(modname + key)
                         except KeyError:
-                            pass
+                            # allow walking through not-yet-classloaded packages
+                            return JavaPackageLoader._create_module(loadname)
                 raise AttributeError(key)
             return __getattr__
     else:
@@ -132,12 +133,20 @@ class JavaImportFinder:
         def find_spec(fullname, path, target=None):
             if JavaPackageLoader.is_java_package(fullname):
                 return _frozen_importlib.ModuleSpec(fullname, JavaPackageLoader, is_package=True)
+            elif path == __path__:
+                try:
+                    # do not rely on name conventions. check if it's a type,
+                    # otherwise treat it as a not-yet-classloaded package
+                    type(fullname)
+                    return _frozen_importlib.ModuleSpec(fullname, JavaTypeLoader, is_package=False)
+                except KeyError:
+                    return _frozen_importlib.ModuleSpec(fullname, JavaPackageLoader, is_package=True)
             else:
                 try:
                     type(fullname)
                     return _frozen_importlib.ModuleSpec(fullname, JavaTypeLoader, is_package=False)
                 except KeyError:
-                    pass
+                    pass # when importing from the implicit top-level java module, we only allow types
     else:
         @staticmethod
         def find_spec(fullname, path, target=None):