From 5bfacd26e84c2f2b09e06634954970781dfc3c35 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Sun, 24 Nov 2024 19:13:23 +0100
Subject: [PATCH] [3.12] gh-127217: Fix pathname2url() for paths starting with
 multiple slashes on Posix (GH-127218) (GH-127231)

(cherry picked from commit 97b2ceaaaf88a73a45254912a0e972412879ccbf)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
---
 Lib/test/test_urllib.py                                       | 3 +++
 Lib/urllib/request.py                                         | 4 ++++
 .../Library/2024-11-24-12-41-31.gh-issue-127217.UAXGFr.rst    | 2 ++
 3 files changed, 9 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2024-11-24-12-41-31.gh-issue-127217.UAXGFr.rst

diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index 4bdbc19c1ffb7a..0710950e25a7cd 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -1565,6 +1565,9 @@ def test_pathname2url_posix(self):
         fn = urllib.request.pathname2url
         self.assertEqual(fn('/'), '/')
         self.assertEqual(fn('/a/b.c'), '/a/b.c')
+        self.assertEqual(fn('//a/b.c'), '////a/b.c')
+        self.assertEqual(fn('///a/b.c'), '/////a/b.c')
+        self.assertEqual(fn('////a/b.c'), '//////a/b.c')
         self.assertEqual(fn('/a/b%#c'), '/a/b%25%23c')
 
     @unittest.skipUnless(os_helper.FS_NONASCII, 'need os_helper.FS_NONASCII')
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index c521d96d953883..9a559f44152be5 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1695,6 +1695,10 @@ def url2pathname(pathname):
     def pathname2url(pathname):
         """OS-specific conversion from a file system path to a relative URL
         of the 'file' scheme; not recommended for general use."""
+        if pathname[:2] == '//':
+            # Add explicitly empty authority to avoid interpreting the path
+            # as authority.
+            pathname = '//' + pathname
         encoding = sys.getfilesystemencoding()
         errors = sys.getfilesystemencodeerrors()
         return quote(pathname, encoding=encoding, errors=errors)
diff --git a/Misc/NEWS.d/next/Library/2024-11-24-12-41-31.gh-issue-127217.UAXGFr.rst b/Misc/NEWS.d/next/Library/2024-11-24-12-41-31.gh-issue-127217.UAXGFr.rst
new file mode 100644
index 00000000000000..3139e33302f378
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-11-24-12-41-31.gh-issue-127217.UAXGFr.rst
@@ -0,0 +1,2 @@
+Fix :func:`urllib.request.pathname2url` for paths starting with multiple
+slashes on Posix.