From ea42cf1161567eceeed4d088b64bed82d4ffa75e Mon Sep 17 00:00:00 2001
From: Barney Gale <barney.gale@gmail.com>
Date: Fri, 22 Nov 2024 04:12:50 +0000
Subject: [PATCH] GH-127078: `url2pathname()`: handle extra slash before UNC
 drive in URL path (GH-127132)

Decode a file URI like `file://///server/share` as a UNC path like
`\\server\share`. This form of file URI is created by software the simply
prepends `file:///` to any absolute Windows path.
(cherry picked from commit 8c98ed846a7d7e50c4cf06f823d94737144dcf6a)

Co-authored-by: Barney Gale <barney.gale@gmail.com>
---
 Lib/nturl2path.py                                              | 3 +++
 Lib/test/test_urllib.py                                        | 2 +-
 .../Library/2024-11-22-03-40-02.gh-issue-127078.gI_PaP.rst     | 2 ++
 3 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2024-11-22-03-40-02.gh-issue-127078.gI_PaP.rst

diff --git a/Lib/nturl2path.py b/Lib/nturl2path.py
index 6e0d26c129cb99..757fd01bec8223 100644
--- a/Lib/nturl2path.py
+++ b/Lib/nturl2path.py
@@ -22,6 +22,9 @@ def url2pathname(url):
     elif url[:12] == '//localhost/':
         # Skip past 'localhost' authority.
         url = url[11:]
+    if url[:3] == '///':
+        # Skip past extra slash before UNC drive in URL path.
+        url = url[1:]
     # Windows itself uses ":" even in URLs.
     url = url.replace(':', '|')
     if not '|' in url:
diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index 149c3570357d2b..5542d4d2b26ca4 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -1591,7 +1591,7 @@ def test_url2pathname_win(self):
         # UNC paths
         self.assertEqual(fn('//server/path/to/file'), '\\\\server\\path\\to\\file')
         self.assertEqual(fn('////server/path/to/file'), '\\\\server\\path\\to\\file')
-        self.assertEqual(fn('/////server/path/to/file'), '\\\\\\server\\path\\to\\file')
+        self.assertEqual(fn('/////server/path/to/file'), '\\\\server\\path\\to\\file')
         # Localhost paths
         self.assertEqual(fn('//localhost/C:/path/to/file'), 'C:\\path\\to\\file')
         self.assertEqual(fn('//localhost/C|/path/to/file'), 'C:\\path\\to\\file')
diff --git a/Misc/NEWS.d/next/Library/2024-11-22-03-40-02.gh-issue-127078.gI_PaP.rst b/Misc/NEWS.d/next/Library/2024-11-22-03-40-02.gh-issue-127078.gI_PaP.rst
new file mode 100644
index 00000000000000..a84c06f3c7a273
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-11-22-03-40-02.gh-issue-127078.gI_PaP.rst
@@ -0,0 +1,2 @@
+Fix issue where :func:`urllib.request.url2pathname` failed to discard an
+extra slash before a UNC drive in the URL path on Windows.