From 06c62d697a87822690342cd0d99d1cdbeca4ce9d Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Thu, 30 May 2024 03:28:31 +0200 Subject: [PATCH] [3.13] gh-119260: Clarify is_dataclass Behavior for Subclasses in Documentation and Tests (GH-119480) (#119760) gh-119260: Clarify is_dataclass Behavior for Subclasses in Documentation and Tests (GH-119480) (cherry picked from commit bf4ff3ad2e362801e87c85fffd9e140b774cef26) Co-authored-by: Aditya Borikar Co-authored-by: Carl Meyer --- Doc/library/dataclasses.rst | 4 ++-- Lib/test/test_dataclasses/__init__.py | 18 ++++++++++++++++++ 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst index cf707ca5b6802d..fcb5e8bad295a0 100644 --- a/Doc/library/dataclasses.rst +++ b/Doc/library/dataclasses.rst @@ -461,8 +461,8 @@ Module contents .. function:: is_dataclass(obj) - Return ``True`` if its parameter is a dataclass or an instance of one, - otherwise return ``False``. + Return ``True`` if its parameter is a dataclass (including subclasses of a + dataclass) or an instance of one, otherwise return ``False``. If you need to know if a class is an instance of a dataclass (and not a dataclass itself), then add a further check for ``not diff --git a/Lib/test/test_dataclasses/__init__.py b/Lib/test/test_dataclasses/__init__.py index 04dd9f3265bb33..ffb8bbe75c504f 100644 --- a/Lib/test/test_dataclasses/__init__.py +++ b/Lib/test/test_dataclasses/__init__.py @@ -1547,6 +1547,24 @@ class A(types.GenericAlias): self.assertTrue(is_dataclass(type(a))) self.assertTrue(is_dataclass(a)) + def test_is_dataclass_inheritance(self): + @dataclass + class X: + y: int + + class Z(X): + pass + + self.assertTrue(is_dataclass(X), "X should be a dataclass") + self.assertTrue( + is_dataclass(Z), + "Z should be a dataclass because it inherits from X", + ) + z_instance = Z(y=5) + self.assertTrue( + is_dataclass(z_instance), + "z_instance should be a dataclass because it is an instance of Z", + ) def test_helper_fields_with_class_instance(self): # Check that we can call fields() on either a class or instance,