gh-117584: Raise TypeError for non-paths in posixpath.relpath() (GH-117585)

Lib/posixpath.py

@@ -502,10 +502,10 @@ supports_unicode_filenames = (sys.platform == 'darwin')
 def relpath(path, start=None):
     """Return a relative version of a path"""
 
+    path = os.fspath(path)
     if not path:
         raise ValueError("no path specified")
 
-    path = os.fspath(path)
     if isinstance(path, bytes):
         curdir = b'.'
         sep = b'/'

Lib/test/test_posixpath.py

@@ -650,6 +650,7 @@ class PosixPathTest(unittest.TestCase):
         (real_getcwd, os.getcwd) = (os.getcwd, lambda: r"/home/user/bar")
         try:
             curdir = os.path.split(os.getcwd())[-1]
+            self.assertRaises(TypeError, posixpath.relpath, None)
             self.assertRaises(ValueError, posixpath.relpath, "")
             self.assertEqual(posixpath.relpath("a"), "a")
             self.assertEqual(posixpath.relpath(posixpath.abspath("a")), "a")

Misc/NEWS.d/next/Core and Builtins/2024-04-06-16-42-34.gh-issue-117584.hqk9Hn.rst

@@ -0,0 +1 @@
+Raise :exc:`TypeError` for non-paths in :func:`posixpath.relpath()`.