https://github.com/python/cpython/commit/aa4f541a9742fa1de1008d13cbf23b2eb3799e3a
commit: aa4f541a9742fa1de1008d13cbf23b2eb3799e3a
branch: main
author: Gregory P. Smith <[email protected]>
committer: gpshead <[email protected]>
date: 2026-11-01T06:44:02Z
summary:
gh-160185: Fix CJK StreamWriter.reset() not returning to ASCII (GH-160186)
reset() returned early when nothing was pending, so the shift-back
sequence of hz and iso2022_* was never written (regression from
gh-67436). Also fix a reference leak of the stream.write() result.
files:
A Misc/NEWS.d/next/Library/2026-10-22-00-29-55.gh-issue-160185.BPz40E.rst
M Lib/codecs.py
M Lib/test/test_multibytecodec.py
M Modules/cjkcodecs/multibytecodec.c
diff --git a/Lib/codecs.py b/Lib/codecs.py
index af6ab031157e79..b789009ace5bbd 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -402,9 +402,10 @@ def reset(self):
pass
def seek(self, offset, whence=0):
- self.stream.seek(offset, whence)
+ # reset() may write to the stream: call it at the old position.
if whence == 0 and offset == 0:
self.reset()
+ self.stream.seek(offset, whence)
def __getattr__(self, name,
getattr=getattr):
@@ -741,10 +742,11 @@ def reset(self):
self.writer.reset()
def seek(self, offset, whence=0):
- self.stream.seek(offset, whence)
- self.reader.reset()
+ # writer.reset() may write to the stream: call it at the old position.
if whence == 0 and offset == 0:
self.writer.reset()
+ self.stream.seek(offset, whence)
+ self.reader.reset()
def __getattr__(self, name,
getattr=getattr):
@@ -864,8 +866,8 @@ def reset(self):
def seek(self, offset, whence=0):
# Seeks must be propagated to both the readers and writers
# as they might need to reset their internal buffers.
- self.reader.seek(offset, whence)
self.writer.seek(offset, whence)
+ self.reader.seek(offset, whence)
def __getattr__(self, name,
getattr=getattr):
diff --git a/Lib/test/test_multibytecodec.py b/Lib/test/test_multibytecodec.py
index 39d00d8df3c3d3..b863e0f1edeba6 100644
--- a/Lib/test/test_multibytecodec.py
+++ b/Lib/test/test_multibytecodec.py
@@ -461,6 +461,42 @@ def test_incrementalencoder_final(self):
self.assertEqual(output, self.expected_reset)
self.assertEqual(encoder.encode('', final=True), b'')
+ def test_streamwriter_reset(self):
+ stream = io.BytesIO()
+ writer = codecs.getwriter(self.encoding)(stream)
+ writer.reset()
+ self.assertEqual(stream.getvalue(), b'')
+ writer.write(self.text)
+ self.assertEqual(stream.getvalue(), self.expected)
+ writer.reset()
+ self.assertEqual(stream.getvalue(), self.expected_reset)
+ writer.reset()
+ self.assertEqual(stream.getvalue(), self.expected_reset)
+ writer.write(self.text)
+ writer.reset()
+ self.assertEqual(stream.getvalue(), self.expected_reset * 2)
+
+ def test_streamwriter_seek0(self):
+ # The reset sequence is written before the stream is rewound.
+ info = codecs.lookup(self.encoding)
+ for wrap in (
+ info.streamwriter,
+ lambda stream: codecs.StreamReaderWriter(
+ stream, info.streamreader, info.streamwriter),
+ lambda stream: codecs.EncodedFile(stream, 'utf-8', self.encoding),
+ ):
+ stream = io.BytesIO()
+ writer = wrap(stream)
+ text = self.text
+ if isinstance(writer, codecs.StreamRecoder):
+ text = text.encode()
+ writer.write(text)
+ writer.seek(0)
+ self.assertEqual(stream.tell(), 0)
+ self.assertEqual(stream.getvalue(), self.expected_reset)
+ writer.write(text)
+ self.assertEqual(stream.getvalue(), self.expected_reset)
+
def test_incrementalencoder_error(self):
# The output of a failed encode() is lost, so the shift state
# must not be changed.
diff --git
a/Misc/NEWS.d/next/Library/2026-10-22-00-29-55.gh-issue-160185.BPz40E.rst
b/Misc/NEWS.d/next/Library/2026-10-22-00-29-55.gh-issue-160185.BPz40E.rst
new file mode 100644
index 00000000000000..a9d7aef03214a3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-22-00-29-55.gh-issue-160185.BPz40E.rst
@@ -0,0 +1,5 @@
+Fix :meth:`codecs.StreamWriter.reset` of the stateful CJK codecs (``hz`` and
+the ``iso2022_*`` family) not writing the sequence that returns the output to
+ASCII. ``seek(0)`` of :class:`codecs.StreamWriter`,
+:class:`codecs.StreamReaderWriter` and :class:`codecs.StreamRecoder` now
+resets the writer before moving the stream position.
diff --git a/Modules/cjkcodecs/multibytecodec.c
b/Modules/cjkcodecs/multibytecodec.c
index 39ea624a2766af..ba3c70c998f6a9 100644
--- a/Modules/cjkcodecs/multibytecodec.c
+++ b/Modules/cjkcodecs/multibytecodec.c
@@ -1875,13 +1875,17 @@
_multibytecodec_MultibyteStreamWriter_reset_impl(MultibyteStreamWriterObject *se
PyTypeObject *cls)
/*[clinic end generated code: output=32ef224c2a38aa3d input=28af6a9cd38d1979]*/
{
- PyObject *pwrt;
+ PyObject *pwrt, *pending;
- if (!self->pending)
- Py_RETURN_NONE;
+ /* even without pending characters, a stateful codec may have to
+ * write a sequence that returns the output to its initial state */
+ pending = self->pending;
+ if (pending == NULL) {
+ pending = Py_GetConstantBorrowed(Py_CONSTANT_EMPTY_STR);
+ }
pwrt = multibytecodec_encode(self->codec, &self->state,
- self->pending, NULL, self->errors,
+ pending, NULL, self->errors,
MBENC_FLUSH | MBENC_RESET);
/* some pending buffer can be truncated when UnicodeEncodeError is
* raised on 'strict' mode. but, 'reset' method is designed to
@@ -1904,6 +1908,7 @@
_multibytecodec_MultibyteStreamWriter_reset_impl(MultibyteStreamWriterObject *se
Py_DECREF(pwrt);
return NULL;
}
+ Py_DECREF(wr);
}
Py_DECREF(pwrt);
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