From ca4b741daa0feb0aa65cef886a0de629fe584d78 Mon Sep 17 00:00:00 2001
From: Chris Denton <chris@chrisdenton.dev>
Date: Mon, 3 Feb 2025 14:02:13 +0000
Subject: [PATCH] gh-12933: fix import error over nfs on Windows

On Windows, realpath uses `GetFinalPathNameByHandleW` to resolve paths. This returns paths starting with a `\\?\` prefix, which is usually not what we want.

This change attempts to remove the prefix for \\?\UNC\ paths. A similar thing was already done for drive paths such as \\?\C:\.
---
 Misc/ACKS                                     |  1 +
 ...-02-01-01-30-10.gh-issue-129333.tnKrqz.rst |  1 +
 Modules/getpath.c                             | 21 +++++++++++++++----
 3 files changed, 19 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Windows/2025-02-01-01-30-10.gh-issue-129333.tnKrqz.rst

diff --git a/Misc/ACKS b/Misc/ACKS
index 47c8d2b40aafb7..deb437b99000eb 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -439,6 +439,7 @@ Erik Demaine
 Jeroen Demeyer
 Martin Dengler
 John Dennis
+Chris Denton
 L. Peter Deutsch
 Roger Dev
 Philippe Devalkeneer
diff --git a/Misc/NEWS.d/next/Windows/2025-02-01-01-30-10.gh-issue-129333.tnKrqz.rst b/Misc/NEWS.d/next/Windows/2025-02-01-01-30-10.gh-issue-129333.tnKrqz.rst
new file mode 100644
index 00000000000000..3d4dd1e27f460c
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2025-02-01-01-30-10.gh-issue-129333.tnKrqz.rst
@@ -0,0 +1 @@
+Fixes import error when running Python from a network drive
diff --git a/Modules/getpath.c b/Modules/getpath.c
index e2478da021f511..f22bad9a304954 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -540,11 +540,24 @@ getpath_realpath(PyObject *Py_UNUSED(self) , PyObject *args)
         PyErr_SetFromWindowsErr(err);
         result = NULL;
     } else if (len <= MAXPATHLEN) {
-        const wchar_t *p = resolved;
+        wchar_t *p = resolved;
         if (0 == wcsncmp(p, L"\\\\?\\", 4)) {
-            if (GetFileAttributesW(&p[4]) != INVALID_FILE_ATTRIBUTES) {
-                p += 4;
-                len -= 4;
+            if (0 == wcsncmp(&p[4], L"UNC\\", 4)) {
+                // A \\?\UNC\ path. Try converting to a \\ path.
+                p[6] = L'\\';
+                if (GetFileAttributesW(&p[6]) != INVALID_FILE_ATTRIBUTES) {
+                    p += 6;
+                    len -= 6;
+                } else {
+                    // Change back to a \\?\UNC\ path.
+                    p[6] = L'C';
+                }
+            } else {
+                // Maybe a drive path like \\?\C:\. Try stripping the prefix.
+                if (GetFileAttributesW(&p[4]) != INVALID_FILE_ATTRIBUTES) {
+                    p += 4;
+                    len -= 4;
+                }
             }
         }
         if (CompareStringOrdinal(path, (int)pathlen, p, len, TRUE) == CSTR_EQUAL) {