Deprecate prefer_stream of getdefaultencoding

Carreau · Carreau · commit 10c8cbe74d49 · 2025-02-26T12:01:47.000+01:00
Closes #14622
diff --git a/IPython/utils/encoding.py b/IPython/utils/encoding.py
@@ -3,20 +3,21 @@
 Utilities for dealing with text encodings
 """
 
-#-----------------------------------------------------------------------------
+# -----------------------------------------------------------------------------
 #  Copyright (C) 2008-2012  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
-#-----------------------------------------------------------------------------
+# -----------------------------------------------------------------------------
 
-#-----------------------------------------------------------------------------
+# -----------------------------------------------------------------------------
 # Imports
-#-----------------------------------------------------------------------------
+# -----------------------------------------------------------------------------
 import sys
 import locale
 import warnings
 
+
 # to deal with the possibility of sys.std* not being a stream at all
 def get_stream_enc(stream, default=None):
     """Return the given stream's encoding or a default.
@@ -26,16 +27,20 @@ def get_stream_enc(stream, default=None):
     a default if it doesn't exist or evaluates as False. ``default``
     is None if not provided.
     """
-    if not hasattr(stream, 'encoding') or not stream.encoding:
+    if not hasattr(stream, "encoding") or not stream.encoding:
         return default
     else:
         return stream.encoding
 
+
+_sentinel = object()
+
+
 # Less conservative replacement for sys.getdefaultencoding, that will try
 # to match the environment.
 # Defined here as central function, so if we find better choices, we
 # won't need to make changes all over IPython.
-def getdefaultencoding(prefer_stream=True):
+def getdefaultencoding(prefer_stream=_sentinel):
     """Return IPython's guess for the default encoding for bytes as text.
 
     If prefer_stream is True (default), asks for stdin.encoding first,
@@ -46,10 +51,20 @@ def getdefaultencoding(prefer_stream=True):
     and finally to sys.getdefaultencoding() which is the most conservative option,
     and usually UTF8 as of Python 3.
     """
+    if prefer_stream is not _sentinel:
+        warnings.warn(
+            "getpreferredencoding(prefer_stream=) argument is deprecated since "
+            "IPython 9.0, getdefaultencoding() will take no argument in the "
+            "future. If you rely on `prefer_stream`, please open an issue on "
+            "the IPython repo.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        prefer_stream = True
     enc = None
     if prefer_stream:
         enc = get_stream_enc(sys.stdin)
-    if not enc or enc=='ascii':
+    if not enc or enc == "ascii":
         try:
             # There are reports of getpreferredencoding raising errors
             # in some cases, which may well be fixed, but let's be conservative here.
@@ -60,12 +75,15 @@ def getdefaultencoding(prefer_stream=True):
     # On windows `cp0` can be returned to indicate that there is no code page.
     # Since cp0 is an invalid encoding return instead cp1252 which is the
     # Western European default.
-    if enc == 'cp0':
+    if enc == "cp0":
         warnings.warn(
             "Invalid code page cp0 detected - using cp1252 instead."
             "If cp1252 is incorrect please ensure a valid code page "
-            "is defined for the process.", RuntimeWarning)
-        return 'cp1252'
+            "is defined for the process.",
+            RuntimeWarning,
+        )
+        return "cp1252"
     return enc
 
+
 DEFAULT_ENCODING = getdefaultencoding()
