ConfigParser._read doesn't join multi-line values collected while reading if a ParsingError occured

[fhoech]

BPO	24142
Nosy	@ned-deily, @ambv, @serhiy-storchaka
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	ConfigParser.py.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/ambv'
closed_at = <Date 2016-11-26.22:06:53.090>
created_at = <Date 2015-05-07.15:54:46.878>
labels = ['3.7', 'type-bug', 'library']
title = "ConfigParser._read doesn't join multi-line values collected while reading if a ParsingError occured"
updated_at = <Date 2017-03-31.16:36:32.996>
user = 'https://bugs.python.org/fhoech'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:32.996>
actor = 'dstufft'
assignee = 'lukasz.langa'
closed = True
closed_date = <Date 2016-11-26.22:06:53.090>
closer = 'lukasz.langa'
components = ['Library (Lib)']
creation = <Date 2015-05-07.15:54:46.878>
creator = 'fhoech'
dependencies = []
files = ['39312']
hgrepos = []
issue_num = 24142
keywords = ['patch']
message_count = 10.0
messages = ['242718', '242719', '242725', '272120', '281802', '281803', '281804', '281809', '281839', '281846']
nosy_count = 5.0
nosy_names = ['ned.deily', 'lukasz.langa', 'python-dev', 'serhiy.storchaka', 'fhoech']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue24142'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7']

[fhoech]

If a ParsingError occurs while reading a config file, the multi-line values collected while reading will never be joined because the error is raised before this can happen. This leads to very unexpected results, e.g. consider the following config.ini:

[DEFAULT]
test = test
invalid

>> cfg = ConfigParser.ConfigParser()
>> cfg.read(['config.ini'])

This will raise a ParsingError as expected. But the option values that were parsed without error are now all lists instead of strings:

>>> cfg.get('DEFAULT', test')
['test']

Patch attached.

[fhoech]

[Btw, you might want to fix the contributor agreement form - I can't sign it because it shows no text, so I don't know what I'm supposed to enter in the fields (Firefox 37.0.2)]

[ned-deily]

[Thanks for the headsup about the contributor agreement form, now reported as https://github.com/python/pythondotorg/issues/747]

[fhoech]

It seems this hasn't landed yet?

[python-dev]

New changeset 40567b8e3478 by Łukasz Langa in branch '3.5':
Fixes bpo-24142: [configparser] always join multiline values to not leave the parser in an invalid state
https://hg.python.org/cpython/rev/40567b8e3478

New changeset 306cfb866399 by Łukasz Langa in branch '3.6':
Merge 3.5, fix for bpo-24142
https://hg.python.org/cpython/rev/306cfb866399

New changeset 876bee0bd0ba by Łukasz Langa in branch 'default':
Merge 3.6, fix for bpo-24142
https://hg.python.org/cpython/rev/876bee0bd0ba

[ambv]

Thanks for your patch! As you can see, 2.7 is no longer touched as the codebases diverged. I'll release a 3.6 backport on PyPI sometime this weekend that you can use.

[serhiy-storchaka]

Is this release critical for 3.6.0?

[ned-deily]

After discussing this offline with Łukasz, I'm going to take the risk of allowing the non-conforming 3.6 checkin to remain in for 3.6.0.

[fhoech]

Thanks for your patch! As you can see, 2.7 is no longer touched as the
codebases diverged.

Thanks, although I have to say it's a little bit unfortunate that Python
2.7 will be left in a worse state than 2.6 where this bug did not exist.

[serhiy-storchaka]

Would be nice to add Misc/NEWS entry for this patch.