From 19050711f5a68e50b942b3b7f1f4cf398f27efff Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Sun, 5 Dec 2021 13:25:43 -0800 Subject: bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias (GH-29294) (cherry picked from commit 446be166861b2f08f87f74018113dd98ca5fca02) Co-authored-by: Serhiy Storchaka --- Lib/dataclasses.py | 2 +- Lib/test/test_dataclasses.py | 12 ++++++++++++ .../next/Library/2021-10-28-23-11-59.bpo-45663.J90N5R.rst | 2 ++ 3 files changed, 15 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Library/2021-10-28-23-11-59.bpo-45663.J90N5R.rst diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index c98e74d..6890705 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -1047,7 +1047,7 @@ def _is_dataclass_instance(obj): def is_dataclass(obj): """Returns True if obj is a dataclass or an instance of a dataclass.""" - cls = obj if isinstance(obj, type) else type(obj) + cls = obj if isinstance(obj, type) and not isinstance(obj, GenericAlias) else type(obj) return hasattr(cls, _FIELDS) diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py index ad981d1..fa5adfc 100644 --- a/Lib/test/test_dataclasses.py +++ b/Lib/test/test_dataclasses.py @@ -7,6 +7,7 @@ from dataclasses import * import pickle import inspect import builtins +import types import unittest from unittest.mock import Mock from typing import ClassVar, Any, List, Union, Tuple, Dict, Generic, TypeVar, Optional, Protocol @@ -1348,6 +1349,17 @@ class TestCase(unittest.TestCase): with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'): replace(obj, x=0) + def test_is_dataclass_genericalias(self): + @dataclass + class A(types.GenericAlias): + origin: type + args: type + self.assertTrue(is_dataclass(A)) + a = A(list, int) + self.assertTrue(is_dataclass(type(a))) + self.assertTrue(is_dataclass(a)) + + def test_helper_fields_with_class_instance(self): # Check that we can call fields() on either a class or instance, # and get back the same thing. diff --git a/Misc/NEWS.d/next/Library/2021-10-28-23-11-59.bpo-45663.J90N5R.rst b/Misc/NEWS.d/next/Library/2021-10-28-23-11-59.bpo-45663.J90N5R.rst new file mode 100644 index 0000000..f246f67 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-10-28-23-11-59.bpo-45663.J90N5R.rst @@ -0,0 +1,2 @@ +Fix :func:`dataclasses.is_dataclass` for dataclasses which are subclasses of +:class:`types.GenericAlias`. -- cgit v0.12