[Distutils] Upcoming changes to PEP 426/440

Nick Coghlan ncoghlan at gmail.com
Sat Jul 20 08:18:15 CEST 2013

On 20 July 2013 03:18, Daniel Holth <dholth at gmail.com> wrote:
> On Fri, Jul 19, 2013 at 11:23 AM, Vinay Sajip <vinay_sajip at yahoo.co.uk> wrote:
>>> I would really like to see one more level of nesting:
>>> requires : { run : [ ... ], test : [ ... ] }
>> I've already changed distlib's code several times as the spec has evolved, and would like not to see any more changes so that I can concentrate on some real work ;-)
>> Seriously, what's currently there now works OK, and the code is fairly simple. I had suggested a variant with even less nesting - one single "requires" list with each entry as it is currently, but having an additional "kind" key with value ":run:", ":test:" etc. This has the merit that you can add additional kinds without major changes, while processing code can filter the list according to its needs at the time. This was shot down by Donald on the basis that it would make things too complicated, or something. Seems a simpler organisation, to me; any argument about additional time to process is unlikely to be a problem in practice, and there are no numbers to point to any performance problems. Currently, with pip, you have to download whole archives while doing dependency resolution, which takes of the order of *seconds* - *minutes* if you're working with Zope/Plone. Doing it in tens/hundreds of milliseconds is sheer luxury :-)
> Either your proposal or mine would work out to be about the same. The
> advantage is that it helps people to conceptualize them as four
> instances of the same thing instead of four different kinds of things
> and it makes it easier to write a forwards-compatible implementation
> without looking for keys ending in _requires. It would also make the
> documentation significantly shorter.

Yeah, I'm mostly interested in being able to *explain* the new
metadata easily. Previously, merging the requirements wasn't
especially practical, due to the requires/may_require split. Now,
though, it's possible to merge them and have the keys match exactly
with the names used in ":run:", etc.

However, I don't think it's enough of a win to duplicate the
"requires" key at two different levels (inside the dependency
specifiers and as a top level field), so I'm happy with sticking to
"Flat is better than nested" on this one :)


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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