gh-77782: Deprecate Py_HasFileSystemDefaultEncoding (#106272)

Deprecate Py_HasFileSystemDefaultEncoding variable.

Author: vstinner

Diff for: Doc/whatsnew/3.12.rst

@@ -1858,6 +1858,7 @@ Deprecated
   * :c:var:`Py_LegacyWindowsFSEncodingFlag`: use :c:member:`PyPreConfig.legacy_windows_fs_encoding`
   * :c:var:`Py_LegacyWindowsStdioFlag`: use :c:member:`PyConfig.legacy_windows_stdio`
   * :c:var:`!Py_FileSystemDefaultEncoding`: use :c:member:`PyConfig.filesystem_encoding`
+  * :c:var:`!Py_HasFileSystemDefaultEncoding`: use :c:member:`PyConfig.filesystem_encoding`
   * :c:var:`!Py_FileSystemDefaultEncodeErrors`: use :c:member:`PyConfig.filesystem_errors`
   * :c:var:`!Py_UTF8Mode`: use :c:member:`PyPreConfig.utf8_mode` (see :c:func:`Py_PreInitialize`)
 

Diff for: Include/fileobject.h

@@ -23,7 +23,7 @@ Py_DEPRECATED(3.12) PyAPI_DATA(const char *) Py_FileSystemDefaultEncoding;
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03060000
 Py_DEPRECATED(3.12) PyAPI_DATA(const char *) Py_FileSystemDefaultEncodeErrors;
 #endif
-PyAPI_DATA(int) Py_HasFileSystemDefaultEncoding;
+Py_DEPRECATED(3.12) PyAPI_DATA(int) Py_HasFileSystemDefaultEncoding;
 
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03070000
 Py_DEPRECATED(3.12) PyAPI_DATA(int) Py_UTF8Mode;