bpo-47000: Make `io.text_encoding()` respects UTF-8 mode (GH-32003)

Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index fd00d65..e3ff59e 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -44,8 +44,9 @@ def text_encoding(encoding, stacklevel=2):
     """
     A helper function to choose the text encoding.
 
-    When encoding is not None, just return it.
-    Otherwise, return the default text encoding (i.e. "locale").
+    When encoding is not None, this function returns it.
+    Otherwise, this function returns the default text encoding
+    (i.e. "locale" or "utf-8" depends on UTF-8 mode).
 
     This function emits an EncodingWarning if *encoding* is None and
     sys.flags.warn_default_encoding is true.
@@ -55,7 +56,10 @@ def text_encoding(encoding, stacklevel=2):
     However, please consider using encoding="utf-8" for new APIs.
     """
     if encoding is None:
-        encoding = "locale"
+        if sys.flags.utf8_mode:
+            encoding = "utf-8"
+        else:
+            encoding = "locale"
         if sys.flags.warn_default_encoding:
             import warnings
             warnings.warn("'encoding' argument not specified.",