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gh-136702: Deprecate passing non-ascii *encoding* (str) to encodings.normalize_encoding #140030

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Merged
malemburg merged 11 commits into from
Nov 9, 2025
+42 −6
Merged

gh-136702: Deprecate passing non-ascii *encoding* (str) to encodings.normalize_encoding #140030

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c8fc658
deprecate non-ascii
StanFromIreland Oct 13, 2025
5b50daa
Relocate import
StanFromIreland Oct 13, 2025
95f2e65
sanitize charset names in email
StanFromIreland Oct 13, 2025
fad52cd
Use table, replace with 'ascii'
StanFromIreland Oct 16, 2025
3ac0804
Merge branch 'main' into encodings/non-ascii
StanFromIreland Oct 31, 2025
9d6f06e
Review
StanFromIreland Nov 1, 2025
16697dc
Fix second warning
StanFromIreland Nov 1, 2025
e4036f8
Convert to asserts
StanFromIreland Nov 1, 2025
b8fc5f4
Fix for platforms with ordered tests
StanFromIreland Nov 1, 2025
7592af8
!fixup
StanFromIreland Nov 1, 2025
8c59899
Fix CI on Android and iOS
StanFromIreland Nov 2, 2025
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6 changes: 6 additions & 0 deletions Doc/deprecations/pending-removal-in-3.17.rst
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Expand Up @@ -23,6 +23,12 @@ Pending removal in Python 3.17
(Contributed by Shantanu Jain in :gh:`91896`.)


* :mod:`encodings`:

- Passing non-ascii *encoding* names to :func:`encodings.normalize_encoding`
is deprecated and scheduled for removal in Python 3.17.
(Contributed by Stan Ulbrych in :gh:`136702`)

* :mod:`typing`:

- Before Python 3.14, old-style unions were implemented using the private class
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8 changes: 7 additions & 1 deletion Lib/encodings/__init__.py
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Expand Up @@ -26,7 +26,7 @@

(c) Copyright CNRI, All Rights Reserved. NO WARRANTY.

"""#"
"""

import codecs
import sys
Expand Down Expand Up @@ -56,6 +56,12 @@ def normalize_encoding(encoding):
if isinstance(encoding, bytes):
encoding = str(encoding, "ascii")

if not encoding.isascii():
import warnings
warnings.warn(
"Support for non-ascii encoding names will be removed in 3.17",
DeprecationWarning, stacklevel=2)

return _normalize_encoding(encoding)

def search_function(encoding):
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10 changes: 7 additions & 3 deletions Lib/test/test_codecs.py
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Expand Up @@ -3886,22 +3886,26 @@ def search_function(encoding):
self.assertEqual(codecs.lookup('TEST.AAA 8'), ('test.aaa-8', 2, 3, 4))
self.assertEqual(codecs.lookup('TEST.AAA---8'), ('test.aaa---8', 2, 3, 4))
self.assertEqual(codecs.lookup('TEST.AAA 8'), ('test.aaa---8', 2, 3, 4))
self.assertEqual(codecs.lookup('TEST.AAA\xe9\u20ac-8'), ('test.aaa\xe9\u20ac-8', 2, 3, 4))
self.assertEqual(codecs.lookup('TEST.AAA.8'), ('test.aaa.8', 2, 3, 4))
self.assertEqual(codecs.lookup('TEST.AAA...8'), ('test.aaa...8', 2, 3, 4))
with self.assertWarns(DeprecationWarning):
self.assertEqual(codecs.lookup('TEST.AAA\xe9\u20ac-8'), ('test.aaa\xe9\u20ac-8', 2, 3, 4))

def test_encodings_normalize_encoding(self):
# encodings.normalize_encoding() ignores non-ASCII characters.
normalize = encodings.normalize_encoding
self.assertEqual(normalize('utf_8'), 'utf_8')
self.assertEqual(normalize('utf\xE9\u20AC\U0010ffff-8'), 'utf_8')
self.assertEqual(normalize('utf 8'), 'utf_8')
# encodings.normalize_encoding() doesn't convert
# characters to lower case.
self.assertEqual(normalize('UTF 8'), 'UTF_8')
self.assertEqual(normalize('utf.8'), 'utf.8')
self.assertEqual(normalize('utf...8'), 'utf...8')

# Non-ASCII *encoding* is deprecated.
with self.assertWarnsRegex(DeprecationWarning,
"Support for non-ascii encoding names will be removed in 3.17"):
self.assertEqual(normalize('utf\xE9\u20AC\U0010ffff-8'), 'utf_8')


if __name__ == "__main__":
unittest.main()
5 changes: 4 additions & 1 deletion Lib/test/test_email/test_email.py
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Expand Up @@ -5717,7 +5717,10 @@ def test_rfc2231_bad_character_in_encoding(self):

"""
msg = email.message_from_string(m)
self.assertEqual(msg.get_filename(), 'myfile.txt')
import warnings
with warnings.catch_warnings():
warnings.simplefilter("ignore", DeprecationWarning)
self.assertEqual(msg.get_filename(), 'myfile.txt')
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@StanFromIreland StanFromIreland Nov 1, 2025

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@bitdancer It was indeed tested.

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@bitdancer bitdancer Nov 1, 2025

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Ah, I missed that. I guess maybe warnings weren't enabled the way I ran the tests, though I thought I was doing so...

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@StanFromIreland StanFromIreland Nov 1, 2025

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What do you want to do, keep it like so or revert to my backwards-compatible approach?

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@bitdancer bitdancer Nov 1, 2025

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I believe I've confirmed that the tests will still pass after lookup starts raising a ValueError, which is what I was hoping would happen. I wonder if we should actually assert the deprecation warning here, though, so that we are reminded to remove the check when the deprecation turns into reality. I'm fine with whatever is standard practice for such cases, though.

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@StanFromIreland StanFromIreland Nov 1, 2025

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Converted to asserts.


def test_rfc2231_single_tick_in_filename_extended(self):
eq = self.assertEqual
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2025-10-13-11-25-41.gh-issue-136702.uvLGK1.rst
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@@ -0,0 +1,3 @@
:mod:`encodings`: Deprecate passing a non-ascii *encoding* name to
:func:`encodings.normalize_encoding` and schedule removal of support for
Python 3.17.
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