ConfigParser does not handle options without values

[mkindahl]

BPO	7005
Nosy	@freddrake, @merwok, @ambv
Files	cfgparser-1.patch: Patch Support "bpo-" in Misc/NEWS #1 for allowing ConfigParser to read configuration files containing options without values cfgparser-2.patch: Patch Rename README to README.rst and enhance formatting #2 for allowing ConfigParser to read configuration files containing options without values cpsample.py: Diagnostic script issue-7005.patch: Patch (Python 2)

^{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/freddrake'
closed_at = <Date 2010-09-03.04:24:03.038>
created_at = <Date 2009-09-27.06:14:03.497>
labels = ['type-feature', 'library']
title = 'ConfigParser does not handle options without values'
updated_at = <Date 2010-09-03.04:24:03.037>
user = 'https://bugs.python.org/mkindahl'

bugs.python.org fields:

activity = <Date 2010-09-03.04:24:03.037>
actor = 'fdrake'
assignee = 'fdrake'
closed = True
closed_date = <Date 2010-09-03.04:24:03.038>
closer = 'fdrake'
components = ['Library (Lib)']
creation = <Date 2009-09-27.06:14:03.497>
creator = 'mkindahl'
dependencies = []
files = ['14985', '14993', '18717', '18718']
hgrepos = []
issue_num = 7005
keywords = ['patch']
message_count = 16.0
messages = ['93168', '93183', '93199', '93200', '93259', '93345', '95244', '99454', '99558', '99559', '114965', '114968', '115407', '115414', '115416', '115417']
nosy_count = 5.0
nosy_names = ['fdrake', 'eric.araujo', 'dwayne', 'mkindahl', 'lukasz.langa']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue7005'
versions = ['Python 2.7', 'Python 3.2']

[mkindahl]

When ConfigParser is used to read in a my.cnf file (MySQL Server
Configuration File), it fails for options that do not have value.

ConfigParser is designed to require a value for each option, but some
systems, such as MySQL option file reader, accepts options without
values. Reading a my.cnf file is almost certain to include options
without values. The server can accept options with values even though
the value is not necessary, but there are some tools that do not allow
values for options that do not require them.

There is an attached patch that optionally will allow options to not
have a value. In order to distinguish options with no value from options
with the empty string, None is assigned to options without values.

The default behavior is to not allow options without values.

[freddrake]

The test "value is not None" in line 620 (of the new version) could be
just "value" and get a little more value from less code.

I don't think I've ever run across a sample .ini-style file that used
unspecified values, though it's frequently done in "flat" configuration
files.

Have you come across an existing configuration format that uses the
[section] markers and unspecified values, or is this really a new use-case?

[mkindahl]

I replied to the mail, but I don't know if it is attached to the issue,
so I'll repeat here.

I'll change the "value is not None" to just "value" where I used that idiom.

The style of using options without values is quite common in my.cnf
files used by MySQL programs. For example, in the Debian (Ubuntu)
package I have installed is using several options without values.

[mkindahl]

Fred L. Drake, Jr. wrote:

Fred L. Drake, Jr. <fdrake@acm.org> added the comment:

The test "value is not None" in line 620 (of the new version) could be
just "value" and get a little more value from less code.

OK.

I don't think I've ever run across a sample .ini-style file that used
unspecified values, though it's frequently done in "flat" configuration
files.

Have you come across an existing configuration format that uses the
[section] markers and unspecified values, or is this really a new use-case?

It is very common in my.cnf files for MySQL, and has been so "for ever." For
example, the default my.cnf file that is installed on my Debian (Ubuntu) system
have several options without values (e.g., skip-external-locking, quick, and
quote-names).

Best wishes,
Mats Kindahl

----------

---

Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue7005\>

---

[mkindahl]

Adding patch with the changes requested by Fred.

[freddrake]

I just looked at some MySQL configuration examples, and wonder if the
guys that made that configuration-style choice were on crack.

MySQL's syntax is sufficient justification for this feature (however
abhorrent I consider it).

(I've not read the patch.)

[mkindahl]

So, what is the status on this?
Who needs to review it?
Is there anything I can do to get it accepted?
Do I need to make any changes (in addition to those already suggested
and done by fdrake)?

[freddrake]

Assigning to myself for handling.

Bumping to Python 2.7 / 3.2 since support for this syntax variation is a new feature.

[freddrake]

Patch and documentation committed to the trunk (r78232).

[freddrake]

Patch and documentation merged to the py3k branch (r78233).

Work on this is complete.

[dwayne]

This is causing a regression in our code.

Previously when we write out our INI file for an entry that has a value of None we saw the following:
value = None

These are now stored as:
value

This is now causing a traceback in our code.

But interestingly I haven't changed anything in our initialisation of ConfigParser, I would have assumed that I need to set allow_no_value for this to work in the new way that MySQL expects.

I would have expected everything to work as it currently does in 2.6 unless I specifically request

You can see the traceback of Virtaal under Python 2. in this bug:
https://bugzilla.redhat.com/show_bug.cgi?id=622061

[freddrake]

Re-opening for investigation.

(The previous message really should have been a new issue.)

[ambv]

This one is strange. Trying to set a None value through set() raises 'TypeError: option values must be strings' on both Python 3.2 and 2.7. A string value of 'None' behaves as expected (e.g. correctly).

[freddrake]

I've attached a diagnostic script that I ran with Python 2.4..3.2 (current py3k HEAD); there are two output variants:

"old style":

[section]
option = None

"new style":

[section]
option

This is the output I get when running this script for each of those Python versions:

2.4.6 RawConfigParser: old-style output
2.4.6 SafeConfigParser: raised TypeError on set
2.4.6 ConfigParser: old-style output

2.5.5 RawConfigParser: old-style output
2.5.5 SafeConfigParser: raised TypeError on set
2.5.5 ConfigParser: old-style output

2.6.5 RawConfigParser: old-style output
2.6.5 SafeConfigParser: raised TypeError on set
2.6.5 ConfigParser: old-style output

2.7 RawConfigParser: new-style output
2.7 SafeConfigParser: raised TypeError on set
2.7 ConfigParser: new-style output

3.1.1 RawConfigParser: old-style output
3.1.1 SafeConfigParser: raised TypeError on set
3.1.1 ConfigParser: old-style output

3.2a1+ RawConfigParser: new-style output
3.2a1+ SafeConfigParser: raised TypeError on set
3.2a1+ ConfigParser: new-style output

Essentially: For the RawConfigParser and ConfigParser classes, the output changes in 2.7 and 3.2, and in a way that should be considered incorrect because it conflicts with the allow_no_values setting.

This is a bug and should be fixed in both 2.7 and 3.2.

The TypeError-on-set is consistently raised only for SafeConfigParser, and should remain unchanged. (Why this was handled differently for SafeConfigParser I don't recall offhand.)

[freddrake]

Attached fix & test for Python 2; adjusting to Python 3 is trivial.

The test could be added to 2.6 as well to protect against regressions there, though that's unlikely to be a significant issue.

[freddrake]

Commited as r84443 (release27-maint), r84444 (py3k)