1 files changed, 25 insertions, 13 deletions
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index 64fe9df..2e3625b 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -49,6 +49,9 @@ def _get_sep(path):
 def normcase(s):
     """Normalize case of pathname.  Has no effect under Posix"""
     # TODO: on Mac OS X, this should really return s.lower().
+    if not isinstance(s, (bytes, str)):
+        raise TypeError("normcase() argument must be str or bytes, "
+                        "not '{}'".format(s.__class__.__name__))
     return s
 
 
@@ -68,16 +71,25 @@ def isabs(s):
 def join(a, *p):
     """Join two or more pathname components, inserting '/' as needed.
     If any component is an absolute path, all previous path components
-    will be discarded."""
+    will be discarded.  An empty last part will result in a path that
+    ends with a separator."""
     sep = _get_sep(a)
     path = a
-    for b in p:
-        if b.startswith(sep):
-            path = b
-        elif not path or path.endswith(sep):
-            path +=  b
-        else:
-            path += sep + b
+    try:
+        for b in p:
+            if b.startswith(sep):
+                path = b
+            elif not path or path.endswith(sep):
+                path += b
+            else:
+                path += sep + b
+    except TypeError:
+        valid_types = all(isinstance(s, (str, bytes, bytearray))
+                          for s in (a, ) + p)
+        if valid_types:
+            # Must have a mixture of text and binary data
+            raise TypeError("Can't mix strings and bytes in path components.")
+        raise
     return path
 
 
@@ -158,7 +170,7 @@ def islink(path):
 def lexists(path):
     """Test whether a path exists.  Returns True for broken symbolic links"""
     try:
-        st = os.lstat(path)
+        os.lstat(path)
     except os.error:
         return False
     return True
@@ -259,12 +271,12 @@ def expanduser(path):
             return path
         userhome = pwent.pw_dir
     if isinstance(path, bytes):
-        userhome = userhome.encode(sys.getfilesystemencoding())
+        userhome = os.fsencode(userhome)
         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.
@@ -424,7 +436,7 @@ def _resolve_link(path):
             path = normpath(resolved)
     return path
 
-supports_unicode_filenames = False
+supports_unicode_filenames = (sys.platform == 'darwin')
 
 def relpath(path, start=None):
     """Return a relative version of a path"""