MERGE: Closes #14768: os.path.expanduser('~/a') doesn't works correctly when HOME is '/'

Lib/posixpath.py

@@ -266,8 +266,8 @@ def expanduser(path):
         root = b'/'
     else:
         root = '/'
-    userhome = userhome.rstrip(root) or userhome
-    return userhome + path[i:]
+    userhome = userhome.rstrip(root)
+    return (userhome + path[i:]) or root
 
 
 # Expand paths containing shell variable substitutions.

Lib/test/test_posixpath.py

@@ -300,6 +300,7 @@ class PosixPathTest(unittest.TestCase):
             with support.EnvironmentVarGuard() as env:
                 env['HOME'] = '/'
                 self.assertEqual(posixpath.expanduser("~"), "/")
+                self.assertEqual(posixpath.expanduser("~/foo"), "/foo")
                 # expanduser should fall back to using the password database
                 del env['HOME']
                 home = pwd.getpwuid(os.getuid()).pw_dir

Misc/ACKS

@@ -335,6 +335,7 @@ Andrew Francis
 Martin Franklin
 Bruce Frederiksen
 Robin Friedrich
+Bradley Froehle
 Ivan Frohne
 Matthias Fuchs
 Jim Fulton

Misc/NEWS

@@ -139,6 +139,8 @@ Library
 
 - Issue #13815: TarFile.extractfile() now returns io.BufferedReader objects.
 
+- Issue #14768: os.path.expanduser('~/a') doesn't works correctly when HOME is '/'.
+
 - Issue #14371: Support bzip2 in zipfile module.  Patch by Serhiy Storchaka.
 
 - Issue #13183: Fix pdb skipping frames after hitting a breakpoint and running