Issue #26800: Undocumented support of general bytes-like objects

as paths in os functions is now deprecated.

Doc/whatsnew/3.6.rst

@@ -638,6 +638,11 @@ Deprecated features
   and will be removed in 3.8.
   (Contributed by Serhiy Storchaka in :issue:`21708`.)
 
+* Undocumented support of general :term:`bytes-like objects <bytes-like object>`
+  as paths in :mod:`os` functions is now deprecated.
+  (Contributed by Serhiy Storchaka in :issue:`25791`.)
+
+
 Deprecated Python behavior
 --------------------------
 

Lib/test/test_os.py

@@ -2626,6 +2626,7 @@ class Str(str):
         else:
             encoded = os.fsencode(support.TESTFN)
         self.bytes_filenames.append(encoded)
+        self.bytes_filenames.append(bytearray(encoded))
         self.bytes_filenames.append(memoryview(encoded))
 
         self.filenames = self.bytes_filenames + self.unicode_filenames
@@ -2699,8 +2700,14 @@ def test_oserror_filename(self):
         for filenames, func, *func_args in funcs:
             for name in filenames:
                 try:
+                    if isinstance(name, str):
+                        func(name, *func_args)
+                    elif isinstance(name, bytes):
                         with bytes_filename_warn(False):
                             func(name, *func_args)
+                    else:
+                        with self.assertWarnsRegex(DeprecationWarning, 'should be'):
+                            func(name, *func_args)
                 except OSError as err:
                     self.assertIs(err.filename, name)
                 else:

Lib/test/test_posix.py

@@ -407,8 +407,10 @@ def test_fstat(self):
     def test_stat(self):
         self.assertTrue(posix.stat(support.TESTFN))
         self.assertTrue(posix.stat(os.fsencode(support.TESTFN)))
-        self.assertTrue(posix.stat(bytearray(os.fsencode(support.TESTFN))))
 
+        self.assertWarnsRegex(DeprecationWarning,
+                'should be string, bytes or integer, not',
+                posix.stat, bytearray(os.fsencode(support.TESTFN)))
         self.assertRaisesRegex(TypeError,
                 'should be string, bytes or integer, not',
                 posix.stat, None)

Misc/NEWS

@@ -43,6 +43,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #26800: Undocumented support of general bytes-like objects
+  as paths in os functions is now deprecated.
+
 - Issue #27661: Added tzinfo keyword argument to datetime.combine.
 
 - Issue #27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the

Modules/posixmodule.c

@@ -891,7 +891,28 @@ path_converter(PyObject *o, void *p)
         }
 #endif
     }
+    else if (PyBytes_Check(o)) {
+#ifdef MS_WINDOWS
+        if (win32_warn_bytes_api()) {
+            return 0;
+        }
+#endif
+        bytes = o;
+        Py_INCREF(bytes);
+    }
     else if (PyObject_CheckBuffer(o)) {
+        if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
+            "%s%s%s should be %s, not %.200s",
+            path->function_name ? path->function_name : "",
+            path->function_name ? ": "                : "",
+            path->argument_name ? path->argument_name : "path",
+            path->allow_fd && path->nullable ? "string, bytes, integer or None" :
+            path->allow_fd ? "string, bytes or integer" :
+            path->nullable ? "string, bytes or None" :
+                             "string or bytes",
+            Py_TYPE(o)->tp_name)) {
+            return 0;
+        }
 #ifdef MS_WINDOWS
         if (win32_warn_bytes_api()) {
             return 0;
@@ -946,9 +967,15 @@ path_converter(PyObject *o, void *p)
     path->length = length;
     path->object = o;
     path->fd = -1;
+    if (bytes == o) {
+        Py_DECREF(bytes);
+        return 1;
+    }
+    else {
         path->cleanup = bytes;
         return Py_CLEANUP_SUPPORTED;
     }
+}
 
 static void
 argument_unavailable_error(const char *function_name, const char *argument_name)