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gh-126845: Some edge cases in email.utils.parsedate_to_datetime seem to differ from RFC2822 spec #134438

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gh-126845: Some edge cases in email.utils.parsedate_to_datetime seem to differ from RFC2822 spec #134438

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a84d66c
added digit check to prevent forced 4-digit year evaluation
GGyll May 21, 2025
df899ea
added tests for obscure year inputs to parsedate_to_datetime
GGyll May 21, 2025
6112424
updated test_email to correctly assert 1 digit year
GGyll May 21, 2025
639514f
📜🤖 Added by blurb_it.
blurb-it[bot] May 21, 2025
5dccaeb
Added newline at end of test_parsedate_to_datetime.py
GGyll May 21, 2025
83bdc71
removed trailing whitespace in parsedate_to_datetime
GGyll May 21, 2025
1575dc3
Merge branch 'main' into bugfix/parsedate_to_datetime
GGyll May 30, 2025
3cba685
fixed 3-digit year edge case
GGyll Jul 17, 2025
da6ff70
reset year check to previous value
GGyll Jul 17, 2025
693bce3
moved ParsedateToDatetimeTest
GGyll Jul 17, 2025
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2 changes: 1 addition & 1 deletion Lib/email/_parseaddr.py
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Expand Up @@ -149,7 +149,7 @@ def _parsedate_tz(data):
# calls for a two-digit yy, but RFC 2822 (which obsoletes RFC 822)
# mandates a 4-digit yy. For more information, see the documentation for
# the time module.
if yy < 100:
if len(str(yy)) >= 2 and yy < 100:
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yy is now a number, so if yy < 100 (and it's positive), len(str(yy)) >= 2 is never true.
You need to keep the original year string for this check.

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I was able to remove this check following what @bitdancer said below

# The year is between 1969 and 1999 (inclusive).
if yy > 68:
yy += 1900
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2 changes: 1 addition & 1 deletion Lib/test/test_email/test_email.py
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Expand Up @@ -3227,7 +3227,7 @@ def test_parsedate_y2k(self):

"""
self.assertEqual(utils.parsedate_tz('25 Feb 03 13:47:26 -0800'),
utils.parsedate_tz('25 Feb 2003 13:47:26 -0800'))
utils.parsedate_tz('25 Feb 3 13:47:26 -0800'))
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This makes the test ineffective.

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reverted this

self.assertEqual(utils.parsedate_tz('25 Feb 71 13:47:26 -0800'),
utils.parsedate_tz('25 Feb 1971 13:47:26 -0800'))

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17 changes: 17 additions & 0 deletions Lib/test/test_email/test_parsedate_to_datetime.py
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@@ -0,0 +1,17 @@
# Test to see if parsedate_to_datetime returns the correct year for different digit numbers, adhering to the RFC2822 spec

import unittest
from email.utils import parsedate_to_datetime

class ParsedateToDatetimeTest(unittest.TestCase):
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parsedate_to_datetime tests belong in test_utils in DateTimeTests. (Those tests could maybe use some refactoring, but let's ignore that ;)

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Just moved it :)

def test(self):
expectations = {
"Sat, 15 Aug 0001 23:12:09 +0500": "0001",
"Thu, 1 Sep 1 23:12:09 +0800": "0001",
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Logically when doing a Postel "be generous in what you accept" recovery here, a single digit year should be treated as if it were a two digit year, which means the result here should 2001, which is what the current code produces.

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@GGyll GGyll Jul 16, 2025 •
edited
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This contradicts what @encukou said in the issue #126845. But I agree with you

"Thu, 7 Oct 123 23:12:09 +0500": "0123",
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And this result should be 2023, per the rfc text you quoted (three digit years get 1900 added). I have no idea why that settled on that logic, it makes no sense to me, but that's what the RFC says.

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Fixed!

}
for input_string, output_string in expectations.items():
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subTest would be good here.

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Fixed!

self.assertEqual(str(parsedate_to_datetime(input_string))[:4], output_string)

if __name__ == '__main__':
unittest.main()
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-05-21-15-32-04.gh-issue-126845.QhEGg6.rst
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@@ -0,0 +1,2 @@
Fixed _parsedate_tz to not evaluate 1 digit years as as 4-digit years, adhering to RFC 2855 4.3
Contributed by Gustaf Gyllensporre.
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