gh-117335: Handle non-iterables for ntpath.commonpath (GH-117336)

Author: nineteendo

Lib/ntpath.py

@@ -831,23 +831,22 @@ def relpath(path, start=None):
         raise
 
 
-# Return the longest common sub-path of the sequence of paths given as input.
+# Return the longest common sub-path of the iterable of paths given as input.
 # The function is case-insensitive and 'separator-insensitive', i.e. if the
 # only difference between two paths is the use of '\' versus '/' as separator,
 # they are deemed to be equal.
 #
 # However, the returned path will have the standard '\' separator (even if the
 # given paths had the alternative '/' separator) and will have the case of the
-# first path given in the sequence. Additionally, any trailing separator is
+# first path given in the iterable. Additionally, any trailing separator is
 # stripped from the returned path.
 
 def commonpath(paths):
-    """Given a sequence of path names, returns the longest common sub-path."""
-
+    """Given an iterable of path names, returns the longest common sub-path."""
+    paths = tuple(map(os.fspath, paths))
     if not paths:
-        raise ValueError('commonpath() arg is an empty sequence')
+        raise ValueError('commonpath() arg is an empty iterable')
 
-    paths = tuple(map(os.fspath, paths))
     if isinstance(paths[0], bytes):
         sep = b'\\'
         altsep = b'/'

Lib/test/test_ntpath.py

@@ -871,11 +871,14 @@ def check_error(exc, paths):
             self.assertRaises(exc, ntpath.commonpath,
                               [os.fsencode(p) for p in paths])
 
+        self.assertRaises(TypeError, ntpath.commonpath, None)
         self.assertRaises(ValueError, ntpath.commonpath, [])
+        self.assertRaises(ValueError, ntpath.commonpath, iter([]))
         check_error(ValueError, ['C:\\Program Files', 'Program Files'])
         check_error(ValueError, ['C:\\Program Files', 'C:Program Files'])
         check_error(ValueError, ['\\Program Files', 'Program Files'])
         check_error(ValueError, ['Program Files', 'C:\\Program Files'])
+
         check(['C:\\Program Files'], 'C:\\Program Files')
         check(['C:\\Program Files', 'C:\\Program Files'], 'C:\\Program Files')
         check(['C:\\Program Files\\', 'C:\\Program Files'],

Misc/NEWS.d/next/Core and Builtins/2024-03-28-19-13-20.gh-issue-117335.d6uKJu.rst

@@ -0,0 +1 @@
+Raise TypeError for non-sequences for :func:`ntpath.commonpath`.