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sm-discuss - Re: [SM-Discuss] [RFC] Compressed filetype detection (Bug #16011)

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  • From: Ismael Luceno <ismael.luceno AT gmail.com>
  • To: Jaka Kranjc <smgl AT lynxlynx.info>
  • Cc: sm-discuss AT lists.ibiblio.org
  • Subject: Re: [SM-Discuss] [RFC] Compressed filetype detection (Bug #16011)
  • Date: Sun, 15 May 2016 17:00:42 -0300

On 15/May/2016 21:23, Jaka Kranjc wrote:
> On Sunday 15 of May 2016 15:45:47 Ismael Luceno wrote:
> > On 15/May/2016 13:29, Jaka Kranjc wrote:
> > > On Saturday 14 of May 2016 16:12:34 Ismael Luceno wrote:
> > > > I would like to hear opinions about this implementation and any ideas
> > > > about how it could be improved.
> > >
> > > Hey,
> > >
> > > maybe I'm missing something, but I don't see an improvement here. When
> > > we
> > > get in the same situation next time, how will we be able to ensure the
> > > user updates this script first? Seems easier with a spell
> > > (force_depends).
> > Good point. However, it seems to me that we're always going to run
> > into this kind of problem
> So what does the script bring to the table then?
>
> > because we don't have any way to force
> > a minimum version, if we could, we may be able to solve this thru
> > the base-system spell, and an upgrade guide with a big warning about
> > making extra sure base-system is up to date, or perhaps a way for a
> > grimoire to have dependencies itself, that might be even better.
> But we do have a way for enforcing minimum versions, it just has to be done
> at
> the spell level. Depend on file in all of the xz-using spells and
> force_depends
> on it if the installed version is not good enough. We already have some
> code
> in grimoire FUNCTIONS for this: is_version_less and
> simple_version_check_force_depends (which should really be using the
> former).
>
> Sorcery could always force an update of basesystem, but that'd be pretty
> disruptive, since it includes the toolchain, potentially starting a
> cascade. A
> subset could work, but what else should be on the list? This is probably
> the
> only chance for a clean solution in the long run. Adding depends on the
> script
> or spell would potentially never end.

That's exactly my concern for those solutions, there's no central
place to define the requirement, the only way is doing it manually
at each place it is used, and it's not truly a build dependency,
plus some upstream projects provide more than one format.

The less disruptive way would be to add file as a dependency for
xz-utils, and force a minimum version, but it's a hack.

By having our own implementation supporting just what we need, we
may avoid those issues to a certain extent, only making mandatory
the upgrade of sorcery in the future, something already needed unless
special support is provided by the spell.

Changes on the supported formats require to accomodate other parts
of sorcery anyway, so it would not be a big deal to update the utility.

And we should consider it seriously because `file` isn't small nor
simple, and depends on zlib. OTOH, our implementation can be very
simple, unlike `file` it doesn't need to look deep into files nor
extract any information, just identifying the file is enough.

> And really, file has supported xz for a long while (late 2011 or earlier),
> so
> I'm surprised you managed to hit the problem at all.

This comes from trying to upgrade an old system, and IMO we should
support upgrades for as many versions as possible if the issue isn't
with the spells themselves, even if only unofficially.




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