Issue #16444, #16218: Use TESTFN_UNDECODABLE on UNIX

Check if data is decoded by os.fsdecode() (filesystem encoding with
surrogateescape error handler, PEP 383), not by UTF-8 or the filesystem
encoding in strict mode.

Use TESTFN_UNDECODABLE in test_cmd_line_script.test_non_ascii() on UNIX.

1 files changed, 12 insertions, 2 deletions

diff --git a/Lib/test/test_cmd_line_script.py b/Lib/test/test_cmd_line_script.py
index 77152b3ec9..6051e18edd 100644
--- a/Lib/test/test_cmd_line_script.py
+++ b/Lib/test/test_cmd_line_script.py
@@ -363,11 +363,21 @@ class CmdLineTest(unittest.TestCase):
             self.assertTrue(text[1].startswith('  File '))
             self.assertTrue(text[3].startswith('NameError'))
 
-    @unittest.skipUnless(support.TESTFN_NONASCII, 'need support.TESTFN_NONASCII')
     def test_non_ascii(self):
+        # Mac OS X denies the creation of a file with an invalid UTF-8 name.
+        # Windows allows to create a name with an arbitrary bytes name, but
+        # Python cannot a undecodable bytes argument to a subprocess.
+        if (support.TESTFN_UNDECODABLE
+        and sys.platform not in ('win32', 'darwin')):
+            name = os.fsdecode(support.TESTFN_UNDECODABLE)
+        elif support.TESTFN_NONASCII:
+            name = support.TESTFN_NONASCII
+        else:
+            self.skipTest("need support.TESTFN_NONASCII")
+
         # Issue #16218
         source = 'print(ascii(__file__))\n'
-        script_name = _make_test_script(os.curdir, support.TESTFN_NONASCII, source)
+        script_name = _make_test_script(os.curdir, name, source)
         self.addCleanup(support.unlink, script_name)
         rc, stdout, stderr = assert_python_ok(script_name)
         self.assertEqual(