email.utils.parsedate() and email.utils.parsedate_tz() should return None when date cannot be parsed

[Arfrever]

BPO	15925
Nosy	@warsaw, @birkenfeld, @bitdancer
Files	parsedate_invalid.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/birkenfeld'
closed_at = <Date 2012-09-22.15:35:54.351>
created_at = <Date 2012-09-12.00:37:45.217>
labels = ['type-bug', 'expert-email', 'release-blocker']
title = 'email.utils.parsedate() and email.utils.parsedate_tz() should return None when date cannot be parsed'
updated_at = <Date 2012-09-24.05:46:47.118>
user = 'https://bugs.python.org/Arfrever'

bugs.python.org fields:

activity = <Date 2012-09-24.05:46:47.118>
actor = 'python-dev'
assignee = 'georg.brandl'
closed = True
closed_date = <Date 2012-09-22.15:35:54.351>
closer = 'georg.brandl'
components = ['email']
creation = <Date 2012-09-12.00:37:45.217>
creator = 'Arfrever'
dependencies = []
files = ['27205']
hgrepos = []
issue_num = 15925
keywords = ['patch', '3.3regression']
message_count = 9.0
messages = ['170347', '170556', '170557', '170558', '170626', '170996', '170997', '171002', '171096']
nosy_count = 5.0
nosy_names = ['barry', 'georg.brandl', 'Arfrever', 'r.david.murray', 'python-dev']
pr_nums = []
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue15925'
versions = ['Python 3.3']

[Arfrever]

Documentation (in Python 3.3) says that None is returned when date cannot be parsed.

In Python 3.2:

>> email.utils.parsedate("0")
>> email.utils.parsedate_tz("0")
>>

In Python 3.3:

>>> email.utils.parsedate("0")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python3.3/email/utils.py", line 232, in parsedate
    return _parsedate(data)
  File "/usr/lib64/python3.3/email/_parseaddr.py", line 172, in parsedate
    t = parsedate_tz(data)
  File "/usr/lib64/python3.3/email/_parseaddr.py", line 51, in parsedate_tz
    if res[9] is None:
TypeError: 'NoneType' object is not subscriptable
>>> email.utils.parsedate_tz("0")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python3.3/email/utils.py", line 238, in parsedate_tz
    return _parsedate_tz(data)
  File "/usr/lib64/python3.3/email/_parseaddr.py", line 51, in parsedate_tz
    if res[9] is None:
TypeError: 'NoneType' object is not subscriptable
>>> email.utils.parsedate_to_datetime("0")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python3.3/email/utils.py", line 243, in parsedate_to_datetime
    *dtuple, tz = __parsedate_tz(data)
TypeError: 'NoneType' object is not iterable
>>>

[bitdancer]

Here is a patch.

Georg, this unfortunately represents a regression from 3.2 and should be fixed.

[bitdancer]

Hmm. Not sure why Georg didn't get auto-added.

[bitdancer]

Oh, and I'm purposely allowing parsedate_to_datetime throw exceptions. I suppose that should be documented, but that's a separate issue.

[Arfrever]

I think that email.utils.parsedate_to_datetime("0") should raise ValueError instead of TypeError.

[python-dev]

New changeset 3b03d31f6a79 by R David Murray in branch 'default':
bpo-15925: fix regression: return None for null and non-date strings.
http://hg.python.org/cpython/rev/3b03d31f6a79

[bitdancer]

I don't think it is worth the extra code to convert the TypeError into a ValueError. We aren't very strict about the distinction between those two.

Leaving this open for Georg to transplant it to 3.3.0.

[birkenfeld]

This was committed to the release clone as c1e9a1fc6931.

[python-dev]

New changeset c1e9a1fc6931 by Georg Brandl in branch 'default':
Closes bpo-15925: fix regression in parsedate() and parsedate_tz() that should return None if unable to parse the argument.
http://hg.python.org/cpython/rev/c1e9a1fc6931