From 89b8933bb537179f81003928786c5cc6183af591 Mon Sep 17 00:00:00 2001
From: Steve Dower <steve.dower@python.org>
Date: Mon, 16 Sep 2019 15:25:11 +0100
Subject: [PATCH] bpo-38081: Add more non-fatal error codes for ntpath.realpath
 (GH-16156)

---
 Lib/ntpath.py | 41 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index 1b5e16f95f1..01f1f423c90 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -530,15 +530,28 @@ else:
         if seen is None:
             seen = set()
 
+        # These error codes indicate that we should stop reading links and
+        # return the path we currently have.
+        # 1: ERROR_INVALID_FUNCTION
+        # 2: ERROR_FILE_NOT_FOUND
+        # 3: ERROR_DIRECTORY_NOT_FOUND
+        # 5: ERROR_ACCESS_DENIED
+        # 21: ERROR_NOT_READY (implies drive with no media)
+        # 32: ERROR_SHARING_VIOLATION (probably an NTFS paging file)
+        # 50: ERROR_NOT_SUPPORTED (implies no support for reparse points)
+        # 67: ERROR_BAD_NET_NAME (implies remote server unavailable)
+        # 87: ERROR_INVALID_PARAMETER
+        # 4390: ERROR_NOT_A_REPARSE_POINT
+        # 4392: ERROR_INVALID_REPARSE_DATA
+        # 4393: ERROR_REPARSE_TAG_INVALID
+        allowed_winerror = 1, 2, 3, 5, 21, 32, 50, 67, 87, 4390, 4392, 4393
+
         while normcase(path) not in seen:
             seen.add(normcase(path))
             try:
                 path = _nt_readlink(path)
             except OSError as ex:
-                # Stop on incorrect function (1), file (2) or
-                # directory (3) not found, or paths that are
-                # not reparse points (4390)
-                if ex.winerror in (1, 2, 3, 4390):
+                if ex.winerror in allowed_winerror:
                     break
                 raise
             except ValueError:
@@ -554,9 +567,20 @@ else:
         except OSError:
             pass
 
-        # Allow file (2) or directory (3) not found, incorrect parameter (87),
-        # invalid syntax (123), and symlinks that cannot be followed (1921)
-        allowed_winerror = 2, 3, 87, 123, 1921
+        # These error codes indicate that we should stop resolving the path
+        # and return the value we currently have.
+        # 1: ERROR_INVALID_FUNCTION
+        # 2: ERROR_FILE_NOT_FOUND
+        # 3: ERROR_DIRECTORY_NOT_FOUND
+        # 5: ERROR_ACCESS_DENIED
+        # 21: ERROR_NOT_READY (implies drive with no media)
+        # 32: ERROR_SHARING_VIOLATION (probably an NTFS paging file)
+        # 50: ERROR_NOT_SUPPORTED
+        # 67: ERROR_BAD_NET_NAME (implies remote server unavailable)
+        # 87: ERROR_INVALID_PARAMETER
+        # 123: ERROR_INVALID_NAME
+        # 1921: ERROR_CANT_RESOLVE_FILENAME (implies unfollowable symlink)
+        allowed_winerror = 1, 2, 3, 5, 21, 32, 50, 67, 87, 123, 1921
 
         # Non-strict algorithm is to find as much of the target directory
         # as we can and join the rest.
@@ -571,6 +595,9 @@ else:
                 if ex.winerror not in allowed_winerror:
                     raise
                 path, name = split(path)
+                # TODO (bpo-38186): Request the real file name from the directory
+                # entry using FindFirstFileW. For now, we will return the path
+                # as best we have it
                 if path and not name:
                     return abspath(path + tail)
                 tail = join(name, tail) if tail else name