py/modbuiltins: Make built-in hasattr work properly for user types.

It now allows __getattr__ in a user type to raise AttributeError when the
attribute does not exist.

py/modbuiltins.c

@@ -525,14 +525,8 @@ MP_DEFINE_CONST_FUN_OBJ_2(mp_builtin_delattr_obj, mp_builtin_delattr);
 
 STATIC mp_obj_t mp_builtin_hasattr(mp_obj_t object_in, mp_obj_t attr_in) {
     qstr attr = mp_obj_str_get_qstr(attr_in);
-
     mp_obj_t dest[2];
-    // TODO: https://docs.python.org/3/library/functions.html?highlight=hasattr#hasattr
-    // explicitly says "This is implemented by calling getattr(object, name) and seeing
-    // whether it raises an AttributeError or not.", so we should explicitly wrap this
-    // in nlr_push and handle exception.
-    mp_load_method_maybe(object_in, attr, dest);
-
+    mp_load_method_protected(object_in, attr, dest, false);
     return mp_obj_new_bool(dest[0] != MP_OBJ_NULL);
 }
 MP_DEFINE_CONST_FUN_OBJ_2(mp_builtin_hasattr_obj, mp_builtin_hasattr);

tests/basics/builtin_hasattr.py

@@ -21,12 +21,19 @@ class C:
     def __getattr__(self, attr):
         if attr == "exists":
             return attr
+        elif attr == "raise":
+            raise Exception(123)
         raise AttributeError
 
 c = C()
 print(hasattr(c, "exists"))
-# TODO
-#print(hasattr(c, "doesnt_exist"))
+print(hasattr(c, "doesnt_exist"))
+
+# ensure that non-AttributeError exceptions propagate out of hasattr
+try:
+    hasattr(c, "raise")
+except Exception as er:
+    print(er)
 
 try:
     hasattr(1, b'123')