gh-91952: Make TextIOWrapper.reconfigure() supports "locale" encoding (GH-91982)

Author: methane

Doc/library/io.rst

@@ -1038,6 +1038,9 @@ Text I/O
 
       .. versionadded:: 3.7
 
+      .. versionchanged:: 3.11
+         The method supports ``encoding="locale"`` option.
+
 
 .. class:: StringIO(initial_value='', newline='\\n')
 

Lib/_pyio.py

@@ -2161,6 +2161,8 @@ def reconfigure(self, *,
         else:
             if not isinstance(encoding, str):
                 raise TypeError("invalid encoding: %r" % encoding)
+            if encoding == "locale":
+                encoding = locale.getencoding()
 
         if newline is Ellipsis:
             newline = self._readnl

Misc/NEWS.d/next/Library/2022-04-27-18-04-24.gh-issue-91952.9A4RXx.rst

@@ -0,0 +1 @@
+Add ``encoding="locale"`` support to :meth:`TextIOWrapper.reconfigure`.

Modules/_io/textio.c

@@ -1248,8 +1248,16 @@ textiowrapper_change_encoding(textio *self, PyObject *encoding,
             errors = self->errors;
         }
     }
-    else if (errors == Py_None) {
-        errors = &_Py_ID(strict);
+    else {
+        if (_PyUnicode_EqualToASCIIString(encoding, "locale")) {
+            encoding = _Py_GetLocaleEncodingObject();
+            if (encoding == NULL) {
+                return -1;
+            }
+        }
+        if (errors == Py_None) {
+            errors = &_Py_ID(strict);
+        }
     }
 
     const char *c_errors = PyUnicode_AsUTF8(errors);