From 17c8e261418577982700b829f1eeca6bc77d0513 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 27 Feb 2024 19:13:28 +0200
Subject: [PATCH] gh-115892: Fix ntpath.splitext() with UNC paths

os.path.splitext() on Windows no longer splits an "extension" from
the server or share name in the UNC path.
---
 Lib/ntpath.py                                  | 10 ++++++++--
 Lib/test/test_ntpath.py                        | 18 ++++++++++++++++++
 ...4-02-27-19-13-25.gh-issue-115892.JouB3p.rst |  2 ++
 3 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2024-02-27-19-13-25.gh-issue-115892.JouB3p.rst

diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index e7cbfe17ecb3c8..33317a1c693ac3 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -249,9 +249,15 @@ def split(p):
 def splitext(p):
     p = os.fspath(p)
     if isinstance(p, bytes):
-        return genericpath._splitext(p, b'\\', b'/', b'.')
+        seps = (b'\\', b'/')
+        root, ext = genericpath._splitext(p, b'\\', b'/', b'.')
     else:
-        return genericpath._splitext(p, '\\', '/', '.')
+        seps = ('\\', '/')
+        root, ext = genericpath._splitext(p, '\\', '/', '.')
+    if (ext and root[:1] in seps and root[1:2] in seps and
+        root.count(seps[0], 2) + root.count(seps[1], 2) <= 1):
+        return p, p[:0]
+    return root, ext
 splitext.__doc__ = genericpath._splitext.__doc__
 
 
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 9cb03e3cd5de8d..1732489d4c17f7 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -100,6 +100,24 @@ def test_splitext(self):
         tester('ntpath.splitext("xx\\foo.bar.ext")', ('xx\\foo.bar', '.ext'))
         tester('ntpath.splitext("c:a/b\\c.d")', ('c:a/b\\c', '.d'))
 
+        tester(r'ntpath.splitext("\\server\share.ext")',
+               (r'\\server\share.ext', ''))
+        tester(r'ntpath.splitext("//server/share.ext")',
+               (r'//server/share.ext', ''))
+        tester(r'ntpath.splitext("\\server.ext")',
+               (r'\\server.ext', ''))
+        tester(r'ntpath.splitext("//server.ext")',
+               (r'//server.ext', ''))
+
+        tester(r'ntpath.splitext("\\server\share\file.ext")',
+               (r'\\server\share\file', '.ext'))
+        tester(r'ntpath.splitext("//server/share/file.ext")',
+               (r'//server/share/file', '.ext'))
+        tester(r'ntpath.splitext("\\server\share/file.ext")',
+               (r'\\server\share/file', '.ext'))
+        tester(r'ntpath.splitext("//server/share\file.ext")',
+               (r'//server/share\file', '.ext'))
+
     def test_splitdrive(self):
         tester("ntpath.splitdrive('')", ('', ''))
         tester("ntpath.splitdrive('foo')", ('', 'foo'))
diff --git a/Misc/NEWS.d/next/Library/2024-02-27-19-13-25.gh-issue-115892.JouB3p.rst b/Misc/NEWS.d/next/Library/2024-02-27-19-13-25.gh-issue-115892.JouB3p.rst
new file mode 100644
index 00000000000000..c0ad89a4b0c11c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-02-27-19-13-25.gh-issue-115892.JouB3p.rst
@@ -0,0 +1,2 @@
+:func:`os.path.splitext` on Windows no longer splits an "extension" from the
+server or share name in the UNC path.