gh-91526: io: Remove device encoding support from TextIOWrapper (GH-91529)

`TextIOWrapper.__init__()` called `os.device_encoding(file.fileno())` if fileno is 0-2 and encoding=None.
But it is very rarely works, and never documented behavior.

2 files changed, 0 insertions, 20 deletions

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 0f33ed5..380a7a7 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -2021,14 +2021,6 @@ class TextIOWrapper(TextIOBase):
         self._check_newline(newline)
         encoding = text_encoding(encoding)
 
-        if encoding == "locale" and sys.platform == "win32":
-            # On Unix, os.device_encoding() returns "utf-8" instead of locale encoding
-            # in the UTF-8 mode. So we use os.device_encoding() only on Windows.
-            try:
-                encoding = os.device_encoding(buffer.fileno()) or "locale"
-            except (AttributeError, UnsupportedOperation):
-                pass
-
         if encoding == "locale":
             try:
                 import locale
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index c86251d..45bf81b 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2736,18 +2736,6 @@ class TextIOWrapperTest(unittest.TestCase):
             os.environ.clear()
             os.environ.update(old_environ)
 
-    @support.cpython_only
-    @unittest.skipIf(sys.platform != "win32", "Windows-only test")
-    @unittest.skipIf(sys.flags.utf8_mode, "utf-8 mode is enabled")
-    def test_device_encoding(self):
-        # Issue 15989
-        import _testcapi
-        b = self.BytesIO()
-        b.fileno = lambda: _testcapi.INT_MAX + 1
-        self.assertRaises(OverflowError, self.TextIOWrapper, b, encoding="locale")
-        b.fileno = lambda: _testcapi.UINT_MAX + 1
-        self.assertRaises(OverflowError, self.TextIOWrapper, b, encoding="locale")
-
     def test_encoding(self):
         # Check the encoding attribute is always set, and valid
         b = self.BytesIO()