From: Łukasz <lukaszlapinski7@gmail.com>
Date: Mon, 13 Jul 2026 02:15:53 +0000 (+0200)
Subject: gh-153037: Make ZstdFile.__next__ raise io.UnsupportedOperation on non-readable files... 
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=ed716551e13d1e46a5cd17955657d64b8824626a;p=thirdparty%2FPython%2Fcpython.git

gh-153037: Make ZstdFile.__next__ raise io.UnsupportedOperation on non-readable files (#153045)

Make `ZstdFile.__next__` raise `io.UnsupportedOperation` on non-readable files, consistent with other compression modules.
---

diff --git a/Lib/compression/zstd/_zstdfile.py b/Lib/compression/zstd/_zstdfile.py
index 8d3358152e9a..c4477244e832 100644
--- a/Lib/compression/zstd/_zstdfile.py
+++ b/Lib/compression/zstd/_zstdfile.py
@@ -246,6 +246,7 @@ class ZstdFile(_streams.BaseStream):
         return self._buffer.peek(size)
 
     def __next__(self):
+        self._check_can_read()
         if ret := self._buffer.readline():
             return ret
         raise StopIteration
diff --git a/Lib/test/test_zstd.py b/Lib/test/test_zstd.py
index 6358cc78739c..9225c42e0e71 100644
--- a/Lib/test/test_zstd.py
+++ b/Lib/test/test_zstd.py
@@ -2373,6 +2373,8 @@ class FileTestCase(unittest.TestCase):
                 f.read(100)
             with self.assertRaises(io.UnsupportedOperation):
                 f.seek(100)
+            with self.assertRaises(io.UnsupportedOperation):
+                next(iter(f))
         self.assertEqual(f.closed, True)
         with self.assertRaises(ValueError):
             f.readable()
diff --git a/Misc/NEWS.d/next/Library/2026-07-04-20-28-51.gh-issue-153037.XUSp_g.rst b/Misc/NEWS.d/next/Library/2026-07-04-20-28-51.gh-issue-153037.XUSp_g.rst
new file mode 100644
index 000000000000..cbfc62f75184
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-07-04-20-28-51.gh-issue-153037.XUSp_g.rst
@@ -0,0 +1,3 @@
+Fix :class:`~compression.zstd.ZstdFile` raising :exc:`AttributeError`
+instead of :exc:`io.UnsupportedOperation` when iterating over a file that
+is not open for reading.