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

Lib/posixpath.py

@@ -267,8 +267,8 @@ def expanduser(path):
         except KeyError:
             return path
         userhome = pwent.pw_dir
-    userhome = userhome.rstrip('/') or userhome
-    return userhome + path[i:]
+    userhome = userhome.rstrip('/')
+    return (userhome + path[i:]) or '/'
 
 
 # Expand paths containing shell variable substitutions.

Lib/test/test_posixpath.py

@@ -201,6 +201,7 @@ class PosixPathTest(unittest.TestCase):
             with test_support.EnvironmentVarGuard() as env:
                 env['HOME'] = '/'
                 self.assertEqual(posixpath.expanduser("~"), "/")
+                self.assertEqual(posixpath.expanduser("~/foo"), "/foo")
 
     def test_normpath(self):
         self.assertEqual(posixpath.normpath(""), ".")

Misc/ACKS

@@ -274,6 +274,7 @@ Doug Fort
 John Fouhy
 Martin Franklin
 Robin Friedrich
+Bradley Froehle
 Ivan Frohne
 Jim Fulton
 Tadayoshi Funaba

Misc/NEWS

@@ -60,6 +60,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #14768: os.path.expanduser('~/a') doesn't works correctly when HOME is '/'.
+
 - Issue #13183: Fix pdb skipping frames after hitting a breakpoint and running
   step.  Patch by Xavier de Gaye.