bpo-43510: Implement PEP 597 opt-in EncodingWarning. (GH-19481)
See [PEP 597](https://www.python.org/dev/peps/pep-0597/).
* Add `-X warn_default_encoding` and `PYTHONWARNDEFAULTENCODING`.
* Add EncodingWarning
* Add io.text_encoding()
* open(), TextIOWrapper() emits EncodingWarning when encoding is omitted and warn_default_encoding is enabled.
* _pyio.TextIOWrapper() uses UTF-8 as fallback default encoding used when failed to import locale module. (used during building Python)
* bz2, configparser, gzip, lzma, pathlib, tempfile modules use io.text_encoding().
* What's new entry
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 03001ec..6f89a87 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -1124,6 +1124,17 @@ _io_TextIOWrapper___init___impl(textio *self, PyObject *buffer,
self->b2cratio = 0.0;
if (encoding == NULL) {
+ PyInterpreterState *interp = _PyInterpreterState_GET();
+ if (_PyInterpreterState_GetConfig(interp)->warn_default_encoding) {
+ PyErr_WarnEx(PyExc_EncodingWarning,
+ "'encoding' argument not specified", 1);
+ }
+ }
+ else if (strcmp(encoding, "locale") == 0) {
+ encoding = NULL;
+ }
+
+ if (encoding == NULL) {
/* Try os.device_encoding(fileno) */
PyObject *fileno;
state = IO_STATE();