From 76025e0779a5e3bd34cdbf08dbd9a138bf42150a Mon Sep 17 00:00:00 2001
From: barneygale <barney.gale@gmail.com>
Date: Wed, 30 Oct 2024 20:47:32 +0000
Subject: [PATCH] GH-126205: Fix conversion of UNC paths to file URIs

File URIs for Windows UNC paths should begin with two slashes, not four.
---
 Lib/nturl2path.py                                    |  7 +------
 Lib/test/test_urllib.py                              | 12 ++++++------
 .../2024-10-30-20-45-17.gh-issue-126205.CHEmtx.rst   |  2 ++
 3 files changed, 9 insertions(+), 12 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2024-10-30-20-45-17.gh-issue-126205.CHEmtx.rst

diff --git a/Lib/nturl2path.py b/Lib/nturl2path.py
index 61852aff58912d..6453f202c26d14 100644
--- a/Lib/nturl2path.py
+++ b/Lib/nturl2path.py
@@ -55,16 +55,11 @@ def pathname2url(p):
     if p[:4] == '\\\\?\\':
         p = p[4:]
         if p[:4].upper() == 'UNC\\':
-            p = '\\' + p[4:]
+            p = '\\\\' + p[4:]
         elif p[1:2] != ':':
             raise OSError('Bad path: ' + p)
     if not ':' in p:
         # No drive specifier, just convert slashes and quote the name
-        if p[:2] == '\\\\':
-        # path is something like \\host\path\on\remote\host
-        # convert this to ////host/path/on/remote/host
-        # (notice doubling of slashes at the start of the path)
-            p = '\\\\' + p
         components = p.split('\\')
         return urllib.parse.quote('/'.join(components))
     comp = p.split(':', maxsplit=2)
diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index dc852c8f02758c..4a7993c1627593 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -1524,7 +1524,7 @@ def test_pathname2url_win(self):
         # Test special prefixes are correctly handled in pathname2url()
         fn = urllib.request.pathname2url
         self.assertEqual(fn('\\\\?\\C:\\dir'), '///C:/dir')
-        self.assertEqual(fn('\\\\?\\unc\\server\\share\\dir'), '/server/share/dir')
+        self.assertEqual(fn('\\\\?\\unc\\server\\share\\dir'), '//server/share/dir')
         self.assertEqual(fn("C:"), '///C:')
         self.assertEqual(fn("C:\\"), '///C:')
         self.assertEqual(fn('C:\\a\\b.c'), '///C:/a/b.c')
@@ -1535,11 +1535,11 @@ def test_pathname2url_win(self):
         self.assertRaises(IOError, fn, "XX:\\")
         # No drive letter
         self.assertEqual(fn("\\folder\\test\\"), '/folder/test/')
-        self.assertEqual(fn("\\\\folder\\test\\"), '////folder/test/')
-        self.assertEqual(fn("\\\\\\folder\\test\\"), '/////folder/test/')
-        self.assertEqual(fn('\\\\some\\share\\'), '////some/share/')
-        self.assertEqual(fn('\\\\some\\share\\a\\b.c'), '////some/share/a/b.c')
-        self.assertEqual(fn('\\\\some\\share\\a\\b%#c\xe9'), '////some/share/a/b%25%23c%C3%A9')
+        self.assertEqual(fn("\\\\folder\\test\\"), '//folder/test/')
+        self.assertEqual(fn("\\\\\\folder\\test\\"), '///folder/test/')
+        self.assertEqual(fn('\\\\some\\share\\'), '//some/share/')
+        self.assertEqual(fn('\\\\some\\share\\a\\b.c'), '//some/share/a/b.c')
+        self.assertEqual(fn('\\\\some\\share\\a\\b%#c\xe9'), '//some/share/a/b%25%23c%C3%A9')
         # Round-tripping
         urls = ['///C:',
                 '/////folder/test/',
diff --git a/Misc/NEWS.d/next/Library/2024-10-30-20-45-17.gh-issue-126205.CHEmtx.rst b/Misc/NEWS.d/next/Library/2024-10-30-20-45-17.gh-issue-126205.CHEmtx.rst
new file mode 100644
index 00000000000000..c92ffb75056606
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-10-30-20-45-17.gh-issue-126205.CHEmtx.rst
@@ -0,0 +1,2 @@
+Fix issue where :func:`urllib.request.pathname2url` generated URLs beginning
+with four slashes (rather than two) when given a Windows UNC path.