https://github.com/python/cpython/commit/b188ebeca0710a243571e95e650d6a910c26795e commit: b188ebeca0710a243571e95e650d6a910c26795e branch: 3.14 author: Miss Islington (bot) <[email protected]> committer: bitdancer <[email protected]> date: 2025-12-06T16:39:47-05:00 summary:
[3.14] gh-142006: Fix HeaderWriteError in email.policy.default caused by extra newline (GH-142008) (#142361) gh-142006: Fix HeaderWriteError in email.policy.default caused by extra newline (GH-142008) RDM: This fixes a subtle folding error that showed up when a token exactly filled a line and was followed by whitespace and a token with no folding whitespace that was longer than a line. In this particular circumstance the whitespace after the first token got pushed on to the next line, and then stolen to go in front of the next unfoldable token...leaving a completely empty line in the line buffer. That line got turned in to a newline, which is RFC illegal, and the newish security check caught it. The fix is to just delete that empty line from the buffer. (cherry picked from commit 07eff899d8a8ee4c4b1be7cb223fe25687f6216c) Co-authored-by: Paresh Joshi <[email protected]> Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com> files: A Misc/NEWS.d/next/Library/2025-11-27-10-49-13.gh-issue-142006.nzJDG5.rst M Lib/email/_header_value_parser.py M Lib/test/test_email/test__header_value_parser.py diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py index 91243378dc0441..41401f8f8d54da 100644 --- a/Lib/email/_header_value_parser.py +++ b/Lib/email/_header_value_parser.py @@ -2788,6 +2788,9 @@ def _steal_trailing_WSP_if_exists(lines): if lines and lines[-1] and lines[-1][-1] in WSP: wsp = lines[-1][-1] lines[-1] = lines[-1][:-1] + # gh-142006: if the line is now empty, remove it entirely. + if not lines[-1]: + lines.pop() return wsp def _refold_parse_tree(parse_tree, *, policy): diff --git a/Lib/test/test_email/test__header_value_parser.py b/Lib/test/test_email/test__header_value_parser.py index 179e236ecdfd7f..f7f9f9c4e2fbb5 100644 --- a/Lib/test/test_email/test__header_value_parser.py +++ b/Lib/test/test_email/test__header_value_parser.py @@ -3255,5 +3255,15 @@ def test_long_filename_attachment(self): " filename*1*=_TEST_TES.txt\n", ) + def test_fold_unfoldable_element_stealing_whitespace(self): + # gh-142006: When an element is too long to fit on the current line + # the previous line's trailing whitespace should not trigger a double newline. + policy = self.policy.clone(max_line_length=10) + # The non-whitespace text needs to exactly fill the max_line_length (10). + text = ("a" * 9) + ", " + ("b" * 20) + expected = ("a" * 9) + ",\n " + ("b" * 20) + "\n" + token = parser.get_address_list(text)[0] + self._test(token, expected, policy=policy) + if __name__ == '__main__': unittest.main() diff --git a/Misc/NEWS.d/next/Library/2025-11-27-10-49-13.gh-issue-142006.nzJDG5.rst b/Misc/NEWS.d/next/Library/2025-11-27-10-49-13.gh-issue-142006.nzJDG5.rst new file mode 100644 index 00000000000000..49643892ff9ccd --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-11-27-10-49-13.gh-issue-142006.nzJDG5.rst @@ -0,0 +1 @@ +Fix a bug in the :mod:`email.policy.default` folding algorithm which incorrectly resulted in a doubled newline when a line ending at exactly max_line_length was followed by an unfoldable token. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
