Remove deprecated sys._enablelegacywindowsfsencoding function

Author: StanFromIreland

Doc/deprecations/pending-removal-in-3.16.rst

@@ -89,7 +89,7 @@ Pending removal in Python 3.16
 
 * :mod:`sys`:
 
-  * The :func:`~sys._enablelegacywindowsfsencoding` function
+  * The :func:`!sys._enablelegacywindowsfsencoding` function
     has been deprecated since Python 3.13.
     Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
 

Doc/library/sys.rst

@@ -879,7 +879,7 @@ always available. Unless explicitly noted otherwise, all variables are read-only
 
    .. versionchanged:: 3.6
       Windows is no longer guaranteed to return ``'mbcs'``. See :pep:`529`
-      and :func:`_enablelegacywindowsfsencoding` for more information.
+      for more information.
 
    .. versionchanged:: 3.7
       Return ``'utf-8'`` if the :ref:`Python UTF-8 Mode <utf8-mode>` is
@@ -2107,31 +2107,6 @@ always available. Unless explicitly noted otherwise, all variables are read-only
       See :pep:`768` for more details.
 
 
-.. function:: _enablelegacywindowsfsencoding()
-
-   Changes the :term:`filesystem encoding and error handler` to 'mbcs' and
-   'replace' respectively, for consistency with versions of Python prior to
-   3.6.
-
-   This is equivalent to defining the :envvar:`PYTHONLEGACYWINDOWSFSENCODING`
-   environment variable before launching Python.
-
-   See also :func:`sys.getfilesystemencoding` and
-   :func:`sys.getfilesystemencodeerrors`.
-
-   .. availability:: Windows.
-
-   .. note::
-      Changing the filesystem encoding after Python startup is risky because
-      the old fsencoding or paths encoded by the old fsencoding may be cached
-      somewhere. Use :envvar:`PYTHONLEGACYWINDOWSFSENCODING` instead.
-
-   .. versionadded:: 3.6
-      See :pep:`529` for more details.
-
-   .. deprecated-removed:: 3.13 3.16
-      Use :envvar:`PYTHONLEGACYWINDOWSFSENCODING` instead.
-
 .. data:: stdin
           stdout
           stderr

Doc/using/cmdline.rst

@@ -1154,9 +1154,6 @@ conflict.
    'replace', respectively.  Otherwise, the new defaults 'utf-8' and
    'surrogatepass' are used.
 
-   This may also be enabled at runtime with
-   :func:`sys._enablelegacywindowsfsencoding`.
-
    .. availability:: Windows.
 
    .. versionadded:: 3.6

Doc/whatsnew/3.13.rst

@@ -1958,7 +1958,7 @@ New Deprecations
 
 * :mod:`sys`:
 
-  * Deprecate the :func:`~sys._enablelegacywindowsfsencoding` function,
+  * Deprecate the :func:`!sys._enablelegacywindowsfsencoding` function,
     to be removed in Python 3.16.
     Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
     (Contributed by Inada Naoki in :gh:`73427`.)

Doc/whatsnew/3.16.rst

@@ -126,6 +126,14 @@ symtable
 * The :meth:`!symtable.Class.get_methods` method
   which has been deprecated since Python 3.14.
 
+sys
+---
+
+* The :func:`!sys._enablelegacywindowsfsencoding` function
+  which has been deprecated since Python 3.13.
+  Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
+  (Contributed by Stan Ulbrych in :gh:`149595`.)
+
 sysconfig
 ---------
 

Doc/whatsnew/3.6.rst

@@ -517,7 +517,7 @@ Applications that do not use str to represent paths should use
 :func:`os.fsencode` and :func:`os.fsdecode` to ensure their bytes are
 correctly encoded. To revert to the previous behaviour, set
 :envvar:`PYTHONLEGACYWINDOWSFSENCODING` or call
-:func:`sys._enablelegacywindowsfsencoding`.
+:func:`!sys._enablelegacywindowsfsencoding`.
 
 See :pep:`529` for more information and discussion of code modifications that
 may be required.

Include/internal/pycore_pylifecycle.h

@@ -18,9 +18,6 @@ extern int _Py_SetFileSystemEncoding(
     const char *errors);
 extern void _Py_ClearFileSystemEncoding(void);
 extern PyStatus _PyUnicode_InitEncodings(PyThreadState *tstate);
-#ifdef MS_WINDOWS
-extern int _PyUnicode_EnableLegacyWindowsFSEncoding(void);
-#endif
 
 extern int _Py_IsLocaleCoercionTarget(const char *ctype_loc);
 

Lib/test/test_sys.py

@@ -1283,16 +1283,6 @@ def check(tracebacklimit, expected):
     def test_no_duplicates_in_meta_path(self):
         self.assertEqual(len(sys.meta_path), len(set(sys.meta_path)))
 
-    @unittest.skipUnless(hasattr(sys, "_enablelegacywindowsfsencoding"),
-                         'needs sys._enablelegacywindowsfsencoding()')
-    def test__enablelegacywindowsfsencoding(self):
-        code = ('import sys',
-                'sys._enablelegacywindowsfsencoding()',
-                'print(sys.getfilesystemencoding(), sys.getfilesystemencodeerrors())')
-        rc, out, err = assert_python_ok('-c', '; '.join(code))
-        out = out.decode('ascii', 'replace').rstrip()
-        self.assertEqual(out, 'mbcs replace')
-
     @support.requires_subprocess()
     def test_orig_argv(self):
         code = textwrap.dedent('''

Misc/NEWS.d/3.13.0a3.rst

@@ -2166,7 +2166,7 @@ current user has no permission to the WMI.
 .. nonce: WOpiNt
 .. section: Windows
 
-Deprecate :func:`sys._enablelegacywindowsfsencoding`. Use
+Deprecate :func:`!sys._enablelegacywindowsfsencoding`. Use
 :envvar:`PYTHONLEGACYWINDOWSFSENCODING` instead. Patch by Inada Naoki.
 
 ..

Misc/NEWS.d/next/Library/2026-05-09-11-22-29.gh-issue-149595.1nuYXw.rst

@@ -0,0 +1,2 @@
+Remove the :func:`!sys._enablelegacywindowsfsencoding` function which has
+been deprecated since Python 3.13.