bpo-37609: Add device path support in ntpath splitdrive

Lib/ntpath.py

@@ -134,23 +134,21 @@ def splitdrive(p):
     """
     p = os.fspath(p)
     if len(p) >= 2:
-        if isinstance(p, bytes):
-            sep = b'\\'
-            altsep = b'/'
-            colon = b':'
-        else:
-            sep = '\\'
-            altsep = '/'
-            colon = ':'
+        sep, altsep, colon = get_separator(p)
         normp = p.replace(altsep, sep)
-        if (normp[0:2] == sep*2) and (normp[2:3] != sep):
+        if is_unc_path(normp, sep):
             # is a UNC path:
             # vvvvvvvvvvvvvvvvvvvv drive letter or UNC path
             # \\machine\mountpoint\directory\etc\...
             #           directory ^^^^^^^^^^^^^^^
             index = normp.find(sep, 2)
             if index == -1:
                 return p[:0], p
+            if is_extended_unc(normp, colon):
+                start = normp.find(sep, index + 1)
+                drive_colon = normp.find(colon, index + 1)
+                if drive_colon == -1 or drive_colon > start:
+                    index = normp.find(sep, start + 1)
             index2 = normp.find(sep, index + 1)
             # a UNC path can't have two slashes in a row
             # (after the initial two)
@@ -159,11 +157,30 @@ def splitdrive(p):
             if index2 == -1:
                 index2 = len(p)
             return p[:index2], p[index2:]
-        if normp[1:2] == colon:
+        if is_drive_path(normp, colon):
             return p[:2], p[2:]
     return p[:0], p
 
 
+def is_unc_path(path, sep):
+    return (path[0:2] == sep*2) and (path[2:3] != sep)
+
+
+def is_drive_path(path, colon):
+    return path[1:2] == colon
+
+
+def is_extended_unc(path, colon):
+    return path[2] in ['?', '.'] and path[-2] != colon and path[4:7] == 'UNC'
+
+
+def get_separator(path):
+    sep, altsep, colon = ['\\', '/', ':']
+    if isinstance(path, bytes):
+        sep, altsep, colon = [b'\\', b'/', b':']
+    return sep, altsep, colon
+
+
 # Split a path in head (everything up to the last '/') and tail (the
 # rest).  After the trailing '/' is stripped, the invariant
 # join(head, tail) == p holds.

Lib/test/test_ntpath.py

@@ -84,6 +84,11 @@ def test_splitdrive(self):
         # Issue #19911: UNC part containing U+0130
         self.assertEqual(ntpath.splitdrive('//conky/MOUNTPOİNT/foo/bar'),
                          ('//conky/MOUNTPOİNT', '/foo/bar'))
+        # Issue #37609: UNC device path
+        self.assertEqual(ntpath.splitdrive('//?/UNC/localhost/C$/foo/bar'),
+                         ('//?/UNC/localhost/C$', '/foo/bar'))
+        self.assertEqual(ntpath.splitdrive('//./UNC/localhost/C$/foo/bar'),
+                         ('//./UNC/localhost/C$', '/foo/bar'))
 
     def test_split(self):
         tester('ntpath.split("c:\\foo\\bar")', ('c:\\foo', 'bar'))

Misc/NEWS.d/next/Library/2019-07-18-14-39-59.bpo-37609.1ZYNbG.rst

@@ -0,0 +1 @@
+Add support for unc device path in :func:`ntpath.splitdrive`