From 13185f2bc06795be1b84efce7160667656b14094 Mon Sep 17 00:00:00 2001 From: Cody Maloney Date: Thu, 5 Nov 2026 13:40:33 -0800 Subject: [PATCH] gh-160427: Return None from TextIOWrapper.buffer when detached (GH-160802) gh-154523 turned the buffer member descriptor into a getter that raises ValueError when the buffer is NULL, and the backport shipped in 3.14.9 and 3.15.1. That made hasattr(stream, "buffer") raise after detach(). Restore the old member descriptor result (None) while keeping the critical section. (cherry picked from commit 3422197f5481ac1b3134e2633332415a02959ba4) Co-authored-by: Cody Maloney --- Lib/test/test_io/test_textio.py | 6 +++--- .../Library/2026-10-26-16-15-29.gh-issue-160427.9G4EBb.rst | 2 ++ Modules/_io/textio.c | 6 +++++- 3 files changed, 10 insertions(+), 4 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2026-10-26-16-15-29.gh-issue-160427.9G4EBb.rst diff --git a/Lib/test/test_io/test_textio.py b/Lib/test/test_io/test_textio.py index d252514039a6cbd..185a4ef0b4c56fc 100644 --- a/Lib/test/test_io/test_textio.py +++ b/Lib/test/test_io/test_textio.py @@ -243,6 +243,7 @@ def test_detach(self): r = self.BytesIO() b = self.BufferedWriter(r) t = self.TextIOWrapper(b, encoding="ascii") + self.assertIs(t.buffer, b) self.assertIs(t.detach(), b) t = self.TextIOWrapper(b, encoding="ascii") @@ -258,6 +259,7 @@ def test_detach(self): self.assertEqual(t.errors, "strict") self.assertFalse(t.line_buffering) self.assertFalse(t.write_through) + self.assertIsNone(t.buffer) def test_repr(self): raw = self.BytesIO("hello".encode("utf-8")) @@ -1713,9 +1715,7 @@ def readinto(self, b): self.BufferedReader(raw), encoding="utf-8") method = getattr(wrapper, method_name) self.assertEqual(method(), "ab\n") - with self.assertRaisesRegex(ValueError, - "underlying buffer has been detached"): - getattr(wrapper, 'buffer') + self.assertIsNone(wrapper.buffer) class PyTextIOWrapperTest(TextIOWrapperTest, PyTestCase): diff --git a/Misc/NEWS.d/next/Library/2026-10-26-16-15-29.gh-issue-160427.9G4EBb.rst b/Misc/NEWS.d/next/Library/2026-10-26-16-15-29.gh-issue-160427.9G4EBb.rst new file mode 100644 index 000000000000000..d57dd02a6d576f5 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-10-26-16-15-29.gh-issue-160427.9G4EBb.rst @@ -0,0 +1,2 @@ +Fix :attr:`~io.TextIOBase.buffer` of a detached :class:`io.TextIOWrapper` +raising :exc:`ValueError` instead of returning ``None``. diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c index a8e7bef0283f8e3..6641d12848be59a 100644 --- a/Modules/_io/textio.c +++ b/Modules/_io/textio.c @@ -3453,7 +3453,11 @@ static PyObject * _io_TextIOWrapper_buffer_get_impl(textio *self) /*[clinic end generated code: output=d265a34555aa5d4b input=5951cfa148f7350a]*/ { - return buffer_access_safe(self); + /* gh-160427: None once detached, matching the former member descriptor. */ + if (self->buffer == NULL) { + Py_RETURN_NONE; + } + return Py_NewRef(self->buffer); } static PyMethodDef incrementalnewlinedecoder_methods[] = {