gh-149595: Remove the `sys._enablelegacywindowsfsencoding()` function (#149596)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

diff --git a/Doc/deprecations/pending-removal-in-3.16.rst b/Doc/deprecations/pending-removal-in-3.16.rst
index 50450658d31440ec88c4882674a58570edf8a022..7606daba16dcf82aa13390f52cfbbf431219c8ce 100644 (file)
--- a/Doc/deprecations/pending-removal-in-3.16.rst
+++ b/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:`!_enablelegacywindowsfsencoding` function
     has been deprecated since Python 3.13.
     Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
 

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 6946eb6eeaa5fae0e737973dda004fd06b8d7326..21de31383d425b7acd5458652e785ef0af3fa54e 100644 (file)
--- a/Doc/library/sys.rst
+++ b/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

diff --git a/Doc/tools/removed-ids.txt b/Doc/tools/removed-ids.txt
index adac1b993047bc8ab3649a160d480429a2d01112..ebcd1874e24b3f809483e7b1773ed40dfe7ee7b5 100644 (file)
--- a/Doc/tools/removed-ids.txt
+++ b/Doc/tools/removed-ids.txt
@@ -7,4 +7,5 @@ c-api/file.html: deprecated-api
 library/asyncio-task.html: terminating-a-task-group
 
 # Removed APIs
-library/symtable.html: symtable.Class.get_methods
\ No newline at end of file
+library/symtable.html: symtable.Class.get_methods
+library/sys.html: sys._enablelegacywindowsfsencoding
\ No newline at end of file

diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 59e8f4f9f5a3e47785416156e32d53072be455cc..c4a431a471a546e604d67b2d4773739a89939f4c 100644 (file)
--- a/Doc/using/cmdline.rst
+++ b/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

diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
index de5a37042a9203b71fd9ef495bb893531eef46dd..f09b5c90232e33542ae73b7f8e76fc07eef39904 100644 (file)
--- a/Doc/whatsnew/3.13.rst
+++ b/Doc/whatsnew/3.13.rst
@@ -1958,7 +1958,7 @@ New Deprecations
 
 * :mod:`sys`:
 
-  * Deprecate the :func:`~sys._enablelegacywindowsfsencoding` function,
+  * Deprecate the :func:`!_enablelegacywindowsfsencoding` function,
     to be removed in Python 3.16.
     Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
     (Contributed by Inada Naoki in :gh:`73427`.)

diff --git a/Doc/whatsnew/3.16.rst b/Doc/whatsnew/3.16.rst
index f79f976ee55cfa1e36ea06bb66ba0084dc08d6ba..3c29bda7d1fb862cc0dadb05dea602a40524014e 100644 (file)
--- a/Doc/whatsnew/3.16.rst
+++ b/Doc/whatsnew/3.16.rst
@@ -140,6 +140,14 @@ symtable
 * The :meth:`!symtable.Class.get_methods` method
   which has been deprecated since Python 3.14.
 
+sys
+---
+
+* The :func:`!_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
 ---------
 

diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
index bdd35d39e361949b2bfe257e49708785696154fd..b0382dd8215bc0005dd21a1de4309ed545aef76b 100644 (file)
--- a/Doc/whatsnew/3.6.rst
+++ b/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.

diff --git a/Include/internal/pycore_pylifecycle.h b/Include/internal/pycore_pylifecycle.h
index 8faf7a4d403f846c9afc7cf5d448e1380331f232..12e1e78526db35aa2e3dd0af6077055b820eecfc 100644 (file)
--- a/Include/internal/pycore_pylifecycle.h
+++ b/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);
 

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 3002fa528eab17b7f16b6588b9aff7a46ef9b5ac..02c70403185f60d8fdfa24aa9f18735474729dad 100644 (file)
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -1283,16 +1283,6 @@ class SysModuleTest(unittest.TestCase):
     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('''

diff --git a/Misc/NEWS.d/3.13.0a3.rst b/Misc/NEWS.d/3.13.0a3.rst
index 0f8dee261c6589620a9cd0ce9dc8abecd720246a..3d3b414c9d46af908522bafe6fd9d0faded9fd9e 100644 (file)
--- a/Misc/NEWS.d/3.13.0a3.rst
+++ b/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.
 
 ..

diff --git a/Misc/NEWS.d/next/Library/2026-05-09-11-22-29.gh-issue-149595.1nuYXw.rst b/Misc/NEWS.d/next/Library/2026-05-09-11-22-29.gh-issue-149595.1nuYXw.rst
new file mode 100644 (file)
index 0000000..f397155
--- /dev/null
+++ b/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.

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 5c97efd6838ef3fb70f9cf84a8625e93371c238f..b92743a884a708ecee33c4c52a0bd17dbe811261 100644 (file)
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14928,33 +14928,6 @@ _PyUnicode_FiniEncodings(struct _Py_unicode_fs_codec *fs_codec)
 }
 
 
-#ifdef MS_WINDOWS
-int
-_PyUnicode_EnableLegacyWindowsFSEncoding(void)
-{
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    PyConfig *config = (PyConfig *)_PyInterpreterState_GetConfig(interp);
-
-    /* Set the filesystem encoding to mbcs/replace (PEP 529) */
-    wchar_t *encoding = _PyMem_RawWcsdup(L"mbcs");
-    wchar_t *errors = _PyMem_RawWcsdup(L"replace");
-    if (encoding == NULL || errors == NULL) {
-        PyMem_RawFree(encoding);
-        PyMem_RawFree(errors);
-        PyErr_NoMemory();
-        return -1;
-    }
-
-    PyMem_RawFree(config->filesystem_encoding);
-    config->filesystem_encoding = encoding;
-    PyMem_RawFree(config->filesystem_errors);
-    config->filesystem_errors = errors;
-
-    return init_fs_codec(interp);
-}
-#endif
-
-
 #ifdef Py_DEBUG
 static inline int
 unicode_is_finalizing(void)

diff --git a/Python/clinic/sysmodule.c.h b/Python/clinic/sysmodule.c.h
index 86e942ec2b8afbc60551c7c7f0c78669e0dadda0..6609a88c1a9d58d728dbddbb38a6968e43dcb495 100644 (file)
--- a/Python/clinic/sysmodule.c.h
+++ b/Python/clinic/sysmodule.c.h
@@ -761,34 +761,6 @@ sys_getwindowsversion(PyObject *module, PyObject *Py_UNUSED(ignored))
 
 #endif /* defined(MS_WINDOWS) */
 
-#if defined(MS_WINDOWS)
-
-PyDoc_STRVAR(sys__enablelegacywindowsfsencoding__doc__,
-"_enablelegacywindowsfsencoding($module, /)\n"
-"--\n"
-"\n"
-"Changes the default filesystem encoding to mbcs:replace.\n"
-"\n"
-"This is done for consistency with earlier versions of Python. See PEP\n"
-"529 for more information.\n"
-"\n"
-"This is equivalent to defining the PYTHONLEGACYWINDOWSFSENCODING\n"
-"environment variable before launching Python.");
-
-#define SYS__ENABLELEGACYWINDOWSFSENCODING_METHODDEF    \
-    {"_enablelegacywindowsfsencoding", (PyCFunction)sys__enablelegacywindowsfsencoding, METH_NOARGS, sys__enablelegacywindowsfsencoding__doc__},
-
-static PyObject *
-sys__enablelegacywindowsfsencoding_impl(PyObject *module);
-
-static PyObject *
-sys__enablelegacywindowsfsencoding(PyObject *module, PyObject *Py_UNUSED(ignored))
-{
-    return sys__enablelegacywindowsfsencoding_impl(module);
-}
-
-#endif /* defined(MS_WINDOWS) */
-
 #if defined(HAVE_DLOPEN)
 
 PyDoc_STRVAR(sys_setdlopenflags__doc__,
@@ -2082,10 +2054,6 @@ exit:
     #define SYS_GETWINDOWSVERSION_METHODDEF
 #endif /* !defined(SYS_GETWINDOWSVERSION_METHODDEF) */
 
-#ifndef SYS__ENABLELEGACYWINDOWSFSENCODING_METHODDEF
-    #define SYS__ENABLELEGACYWINDOWSFSENCODING_METHODDEF
-#endif /* !defined(SYS__ENABLELEGACYWINDOWSFSENCODING_METHODDEF) */
-
 #ifndef SYS_SETDLOPENFLAGS_METHODDEF
     #define SYS_SETDLOPENFLAGS_METHODDEF
 #endif /* !defined(SYS_SETDLOPENFLAGS_METHODDEF) */
@@ -2121,4 +2089,4 @@ exit:
 #ifndef SYS_GETANDROIDAPILEVEL_METHODDEF
     #define SYS_GETANDROIDAPILEVEL_METHODDEF
 #endif /* !defined(SYS_GETANDROIDAPILEVEL_METHODDEF) */
-/*[clinic end generated code: output=e8333fe10c01ae66 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=ba849b6e4b9f1ba3 input=a9049054013a1b77]*/

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index c6447d03369a9492ab4768a06a09315f7d54a23d..b75d9e864a18dcb00bce49e4690b1ec54b0c1bc7 100644 (file)
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1790,36 +1790,6 @@ error:
 }
 
 #pragma warning(pop)
-
-/*[clinic input]
-sys._enablelegacywindowsfsencoding
-
-Changes the default filesystem encoding to mbcs:replace.
-
-This is done for consistency with earlier versions of Python. See PEP
-529 for more information.
-
-This is equivalent to defining the PYTHONLEGACYWINDOWSFSENCODING
-environment variable before launching Python.
-[clinic start generated code]*/
-
-static PyObject *
-sys__enablelegacywindowsfsencoding_impl(PyObject *module)
-/*[clinic end generated code: output=f5c3855b45e24fe9 input=2bfa931a20704492]*/
-{
-    if (PyErr_WarnEx(PyExc_DeprecationWarning,
-        "sys._enablelegacywindowsfsencoding() is deprecated and will be "
-        "removed in Python 3.16. Use PYTHONLEGACYWINDOWSFSENCODING "
-        "instead.", 1))
-    {
-        return NULL;
-    }
-    if (_PyUnicode_EnableLegacyWindowsFSEncoding() < 0) {
-        return NULL;
-    }
-    Py_RETURN_NONE;
-}
-
 #endif /* MS_WINDOWS */
 
 #ifdef HAVE_DLOPEN
@@ -2941,7 +2911,6 @@ static PyMethodDef sys_methods[] = {
     SYS__GETFRAME_METHODDEF
     SYS__GETFRAMEMODULENAME_METHODDEF
     SYS_GETWINDOWSVERSION_METHODDEF
-    SYS__ENABLELEGACYWINDOWSFSENCODING_METHODDEF
     SYS__IS_IMMORTAL_METHODDEF
     SYS_INTERN_METHODDEF
     SYS__IS_INTERNED_METHODDEF
@@ -3436,13 +3405,6 @@ winver -- [Windows only] version number of the Python DLL\n\
 "
 )
 #endif /* MS_COREDLL */
-#ifdef MS_WINDOWS
-/* concatenating string here */
-PyDoc_STR(
-"_enablelegacywindowsfsencoding -- [Windows only]\n\
-"
-)
-#endif
 PyDoc_STR(
 "__stdin__ -- the original stdin; don't touch!\n\
 __stdout__ -- the original stdout; don't touch!\n\