Re: Priority & metainfo

[Gustavo Niemeyer <niemeyer conectiva com>]

> Here's the problems I have putting Priority: *in* a package header:
> 
> 1) Who determines what the priority should be? Me and rpm? No thanks ...

The packager/distribution...

> 2) What is rpm supposed to do with a priority tag? "Nothing." as an answer
> will only work until someone does some Neat! Cool! Wow! thing with the tag,
> then rpm from the CLI will be expected to do the same, sigh.

Nothing. :-)

The idea behind this tag is to inform some automated packaging tool
(apt, up2date, whatever) how important a package is to the system.
Depending on this information, the update algorithm will treat the
package differently. This "Neat! Cool! Wow!" thing would be done right
from the start, otherwise I wouldn't be asking for it. If somebody does
something different than what it was expected, well.. there are other
tags which could be used as well.

> 3) What happens when -- just like the current Distribution: and Vendor:
> tags -- the tag values rot?

I'm not sure what you're talking about here.

> 4) What about legacy packages that don't have the tag?

No problems. There should be a "standard" priority anyway. If there's
no tag, the priority should be that one.

> OTOH, I have no problems at all with adding a headerSprintfExtension
> (see lib/formats.c) in order to associate RPMTAG_PRIORITY *with* a package.
> The easiest way to illustrate headerSprintfExtension is
> 
> 	bash$ rpm -q --qf '[%{fsnames}: %{fssizes}\n]' <any-package>
> 	/: 9870213
> 	/proc: 0
> 	/proc/bus/usb: 0
> 	/dev/shm: 0
> 	/dev/pts: 0
> 
> A better example is specspo, which associates Group: et al i18n info
> by doing a lookup with the package name as a primary key.

I've had a look in the code, and I'm a little bit confused with your
suggestion. This system seems to allow rpm to ask for information at
runtime, isn't it? How would that priority be associated with the
package? Maybe a tag in the header which is preprocessed? Sorry, I
missed your suggestion, probably for not understanding this system.

> > This also makes me wonder, wouldn't it be interesting to include a macro
> > which allowed one to include metainformation in a package? Something
> > like:
> > 
> > Meta(Priority): Standard
> > 
> > This would include a pair "Priority" -> "Standard" in an array like
> > RPMTAG_METAINFO. This would be a nice way to append metainformation to
> > a header and still keep this package "cross-distribution".
> 
> I don't mean to pop you balloon, but macros ain't sufficiently well wired
> on the install side of rpm to do more than dream. What is needed is a
> hard and reliable definition of exactly when, where, and how macro expansions
> would occur.

I don't think that could be used in the case explained. But then, maybe
you have some tricks in your pocket I'm not aware of.

Thanks for the patience.

-- 
Gustavo Niemeyer

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