Recover the module of extension-type methods from __self__

Author: tonghuaroot

Lib/annotationlib.py

@@ -1090,10 +1090,17 @@ def type_repr(value):
 
     """
     if isinstance(value, (type, types.FunctionType, types.BuiltinFunctionType)):
-        # Built-in methods have __module__ set to None.
-        if value.__module__ is None or value.__module__ == "builtins":
+        module = value.__module__
+        if module is None:
+            # Built-in methods have __module__ set to None; recover the module
+            # from the bound object (the class itself for class-bound methods).
+            obj = getattr(value, "__self__", None)
+            if obj is not None:
+                cls = obj if isinstance(obj, type) else type(obj)
+                module = cls.__module__
+        if module is None or module == "builtins":
             return value.__qualname__
-        return f"{value.__module__}.{value.__qualname__}"
+        return f"{module}.{value.__qualname__}"
     elif isinstance(value, _Template):
         tree = _template_to_ast(value)
         return ast.unparse(tree)

Lib/test/test_annotationlib.py

@@ -1854,6 +1854,14 @@ def nested():
         self.assertEqual(type_repr([].append), "list.append")
         self.assertEqual(type_repr((1).bit_length), "int.bit_length")
         self.assertEqual(type_repr(dict.fromkeys), "dict.fromkeys")
+        # Methods of extension types also have __module__ set to None, but
+        # are not in the builtins module.
+        import datetime
+        self.assertEqual(
+            type_repr(datetime.datetime(2000, 1, 1).isoformat),
+            "datetime.datetime.isoformat",
+        )
+        self.assertEqual(type_repr(datetime.date.today), "datetime.date.today")
         self.assertEqual(type_repr(type_repr), "annotationlib.type_repr")
         self.assertEqual(type_repr(times_three), f"{__name__}.times_three")
         self.assertEqual(type_repr(...), "...")