https://github.com/python/cpython/commit/9106913d96becf2f06be1e312e46877adccfa6e8
commit: 9106913d96becf2f06be1e312e46877adccfa6e8
branch: 3.14
author: Cody Maloney <[email protected]>
committer: cmaloney <[email protected]>
date: 2026-11-05T14:34:50-08:00
summary:
[3.14] gh-160427: Return None from TextIOWrapper.buffer when detached
(GH-160802) (#161450)
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)
files:
A Misc/NEWS.d/next/Library/2026-10-26-16-15-29.gh-issue-160427.9G4EBb.rst
M Lib/test/test_io.py
M Modules/_io/textio.c
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index caf2ae460cf41df..14466086fff348c 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2910,6 +2910,7 @@ 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")
@@ -2925,6 +2926,7 @@ 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"))
@@ -4403,9 +4405,7 @@ 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):
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 6dd51cc3fbc521e..3aeaad0cf789798 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -3467,7 +3467,11 @@ 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[] = {
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