[openstack-dev] Nova style cleanups with associated hacking check addition

Andreas Jaeger aj at suse.com
Wed Jan 29 18:40:33 UTC 2014

On 01/29/2014 07:22 PM, Joe Gordon wrote:
> On Tue, Jan 28, 2014 at 4:45 AM, John Garbutt <john at johngarbutt.com> wrote:
>> On 27 January 2014 10:10, Daniel P. Berrange <berrange at redhat.com> wrote:
>>> On Fri, Jan 24, 2014 at 11:42:54AM -0500, Joe Gordon wrote:
>>>> On Fri, Jan 24, 2014 at 7:24 AM, Daniel P. Berrange <berrange at redhat.com>wrote:
>>>>> Periodically I've seen people submit big coding style cleanups to Nova
>>>>> code. These are typically all good ideas / beneficial, however, I have
>>>>> rarely (perhaps even never?) seen the changes accompanied by new hacking
>>>>> check rules.
>>>>> The problem with not having a hacking check added *in the same commit*
>>>>> as the cleanup is two-fold
>>>>>  - No guarantee that the cleanup has actually fixed all violations
>>>>>    in the codebase. Have to trust the thoroughness of the submitter
>>>>>    or do a manual code analysis yourself as reviewer. Both suffer
>>>>>    from human error.
>>>>>  - Future patches will almost certainly re-introduce the same style
>>>>>    problems again and again and again and again and again and again
>>>>>    and again and again and again.... I could go on :-)
>>>>> I don't mean to pick on one particular person, since it isn't their
>>>>> fault that reviewers have rarely/never encouraged people to write
>>>>> hacking rules, but to show one example.... The following recent change
>>>>> updates all the nova config parameter declarations cfg.XXXOpt(...) to
>>>>> ensure that the help text was consistently styled:
>>>>>   https://review.openstack.org/#/c/67647/
>>>>> One of the things it did was to ensure that the help text always started
>>>>> with a capital letter. Some of the other things it did were more subtle
>>>>> and hard to automate a check for, but an 'initial capital letter' rule
>>>>> is really straightforward.
>>>>> By updating nova/hacking/checks.py to add a new rule for this, it was
>>>>> found that there were another 9 files which had incorrect capitalization
>>>>> of their config parameter help. So the hacking rule addition clearly
>>>>> demonstrates its value here.
>>>> This sounds like a rule that we should add to
>>>> https://github.com/openstack-dev/hacking.git.
>>> Yep, it could well be added there. I figure rules added to Nova can
>>> be "upstreamed" to the shared module periodically.
>> +1
>> I worry about diverging, but I guess thats always going to happen here.
>>>>> I will concede that documentation about /how/ to write hacking checks
>>>>> is not entirely awesome. My current best advice is to look at how some
>>>>> of the existing hacking checks are done - find one that is checking
>>>>> something that is similar to what you need and adapt it. There are a
>>>>> handful of Nova specific rules in nova/hacking/checks.py, and quite a
>>>>> few examples in the shared repo
>>>>> https://github.com/openstack-dev/hacking.git
>>>>> see the file hacking/core.py. There's some very minimal documentation
>>>>> about variables your hacking check method can receive as input
>>>>> parameters
>>>>> https://github.com/jcrocholl/pep8/blob/master/docs/developer.rst
>>>>> In summary, if you are doing a global coding style cleanup in Nova for
>>>>> something which isn't already validated by pep8 checks, then I strongly
>>>>> encourage additions to nova/hacking/checks.py to validate the cleanup
>>>>> correctness. Obviously with some style cleanups, it will be too complex
>>>>> to write logic rules to reliably validate code, so this isn't a code
>>>>> review point that must be applied 100% of the time. Reasonable personal
>>>>> judgement should apply. I will try comment on any style cleanups I see
>>>>> where I think it is pratical to write a hacking check.
>>>> I would take this even further, I don't think we should accept any style
>>>> cleanup patches that can be enforced with a hacking rule and aren't.
>>> IMHO that would mostly just serve to discourage people from submitting
>>> style cleanup patches because it is too much stick, not enough carrot.
>>> Realistically for some types of style cleanup, the effort involved in
>>> writing a style checker that does not have unacceptable false positives
>>> will be too high to justify. So I think a pragmatic approach to enforcement
>>> is more suitable.
>> +1
>> I would love to enforce it 100% of the time, but sometimes its hard to
>> write the rules, but still a useful cleanup. Lets see how it goes I
>> guess.
> I am weary of adding any new style rules that have to manually
> enforced by human reviewers, we already have a lot of other items to
> cover in a review.

Based on the feedback I got on IRC, I've written such a style guide a
few days ago for the config help strings:


Even if you do not notice these during a review, it's easy for somebody
else to cleanup - and then it's important to have a style guide that
explains how things should be written. I'd like to have consistency
across OpenStack on how these help strings are written.

 Andreas Jaeger aj@{suse.com,opensuse.org} Twitter/Identica: jaegerandi
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