NotificationTestCase.test_multiline_header failing with Python 3.12.4

[Jun Omae]

The test failure occurs with Python 3.12.4 but not with 3.12.3. I think something wrong is introduced in 3.12.4.

  Package        Version
  ---------------------------------------------------------------
  Python       : 3.12.4 (main, Jun  8 2024, 18:29:57) [GCC 9.4.0]
  Setuptools   : 70.0.0
  Pip          : 24.0
  Wheel        : 0.43.0
  Jinja2       : 3.1.4
  multipart    : 0.2.4
  Babel        : 2.15.0
  sqlite3      : 2.6.0 (3.31.1)
  PySqlite3    : 0.5.2 (3.35.5)
  PyMySQL      : 1.4.6
  Psycopg2     : 2.9.9 (dt dec pq3 ext lo64)
  SVN bindings : 1.14.2 (r1899510)
  Mercurial    : 6.7.3
  Pygments     : 2.18.0
  Textile      : 4.0.2
  Pytz         : 2024.1
  Docutils     : 0.21.2
  aiosmtpd     : 1.4.6
  Selenium     : 4.21.0
  PyTidyLib    : 0.3.2 (5.6.0 libtidy.so.5deb1)
  LXML         : not installed
  coverage     : 7.5.3

Variables:
  PATH=/home/jun66j5/venv/py312/bin:/home/jun66j5/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
  PYTHONPATH=.
  TRAC_TEST_DB_URI=
  server-options= -p 3000  --basic-auth='*,/home/jun66j5/src/trac/htpasswd.txt,auth' -e

External dependencies:
  Git version: git version 2.45.2
  Subversion version: 1.14.2

SKIP_FUNCTIONAL_TESTS=1 python -Wdefault -m unittest  trac.test.test_suite
................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................F..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................sss....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................s.................................................................s.......................................................................................................................
======================================================================
FAIL: test_multiline_header (trac.ticket.tests.notification.NotificationTestCase.test_multiline_header)
Encoded headers split into multiple lines
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jun66j5/src/tracdev/svn/1.6-stable/trac/ticket/tests/notification.py", line 730, in test_multiline_header
    self.assertEqual(ticket['summary'], summary)
AssertionError: 'A_ve[49 chars]ong long long long long long long long long long long súmmäry' != 'A_ve[49 chars]ong long long long long long long long long long long súmm äry'
- A_very long long long long long long long long long long long long long long long long long long long long súmmäry
+ A_very long long long long long long long long long long long long long long long long long long long long súmm äry
?                                                                                                                +


----------------------------------------------------------------------
Ran 2804 tests in 32.683s

FAILED (failures=1, skipped=5)

[Jun Omae]

Minimal reproducible example:

Python 3.12.3 (main, May 23 2024, 00:56:56) [GCC 13.2.1 20240309] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from email import message_from_string
>>> from email.message import EmailMessage
>>> from email.header import decode_header, make_header
>>> msg = EmailMessage()
>>> msg.set_content(u'Body text.\n', cte='quoted-printable')
>>> subject = 'A_very' + ' long' * 23 + ' súmmäry'
>>> subject
'A_very long long long long long long long long long long long long long long long long long long long long long long long súmmäry'
>>> msg['Subject'] = subject
>>> print(msg.as_string())
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Subject: A_very long long long long long long long long long long long long
 long long long long long long long long long long long =?utf-8?q?s=C3=BAmm?=
 =?utf-8?q?=C3=A4ry?=

Body text.

>>> parsed_msg = message_from_string(msg.as_string())
>>> parsed_subject = str(make_header(decode_header(parsed_msg['Subject'])))
>>> parsed_subject
'A_very long long long long long long long long long long long long long long long long long long long long long long long súmmäry'
>>> subject == parsed_subject
True
>>>

Python 3.12.4 (main, Jun 20 2024, 23:12:11) [GCC 13.2.1 20240309] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from email import message_from_string
>>> from email.message import EmailMessage
>>> from email.header import decode_header, make_header
>>> msg = EmailMessage()
>>> msg.set_content(u'Body text.\n', cte='quoted-printable')
>>> subject = 'A_very' + ' long' * 23 + ' súmmäry'
>>> subject
'A_very long long long long long long long long long long long long long long long long long long long long long long long súmmäry'
>>> msg['Subject'] = subject
>>> print(msg.as_string())
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Subject: A_very long long long long long long long long long long long long
 long long long long long long long long long long long =?utf-8?q?s=C3=BAmm?=
 =?utf-8?q?_?==?utf-8?q?=C3=A4ry?=

Body text.

>>> parsed_msg = message_from_string(msg.as_string())
>>> parsed_subject = str(make_header(decode_header(parsed_msg['Subject'])))
>>> parsed_subject
'A_very long long long long long long long long long long long long long long long long long long long long long long long súmm äry'
>>> subject == parsed_subject
False
>>>

[Jun Omae]

I've submitted the issue at ​https://github.com/python/cpython/issues/120930.

[Jun Omae]

Skipped this test with Python 3.12.4 in [17827].

[Jun Omae]

The root cause has been fixed in Python 3.12 branch (​https://github.com/python/cpython/pull/121964).