bpo-39899: os.path.expanduser(): don't guess other Windows users' home directories if the basename of the current user's home directory doesn't match their username. (GH-18841)
This makes `ntpath.expanduser()` match `pathlib.Path.expanduser()` in this regard, and is more in line with `posixpath.expanduser()`'s cautious approach.
Also remove the near-duplicate implementation of `expanduser()` in pathlib, and by doing so fix a bug where KeyError could be raised when expanding another user's home directory.
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index 6f77177..421db50 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -312,12 +312,24 @@ def expanduser(path):
drive = ''
userhome = join(drive, os.environ['HOMEPATH'])
+ if i != 1: #~user
+ # Try to guess user home directory. By default all users directories
+ # are located in the same place and are named by corresponding
+ # usernames. If current user home directory points to nonstandard
+ # place, this guess is likely wrong, and so we bail out.
+ current_user = os.environ.get('USERNAME')
+ if current_user != basename(userhome):
+ return path
+
+ target_user = path[1:i]
+ if isinstance(target_user, bytes):
+ target_user = os.fsdecode(target_user)
+ if target_user != current_user:
+ userhome = join(dirname(userhome), target_user)
+
if isinstance(path, bytes):
userhome = os.fsencode(userhome)
- if i != 1: #~user
- userhome = join(dirname(userhome), path[1:i])
-
return userhome + path[i:]