Re: Package inputs in manifests

[Bengt Richter]

Hi Ludo, Guix,

On +2019-11-17 11:35:07 +0100, Ludovic Courtès wrote:
> Hi Simon!
> 
> zimoun <address@hidden> skribis:
> 
> >> Ah, that no.  But (guix scripts environment) has
> >> ‘package-environment-inputs’, which does exactly that, and I guess we
> >> could expose it and document it.
> >
> > Maybe I am doing wrong but I get:
> >
> > $ ./pre-inst-env guix package -p /tmp/guix-dev -m ~/tmp/manif-dep.scm
> >
> > installing new manifest from '/home/simon/tmp/manif-dep.scm' with 53 entries
> > guix package: error: profile contains conflicting entries for gzip
> > guix package: error:   first entry: gzip@1.10
> > /gnu/store/py3k9zla9fj3z7430v4crqj5pyrsd3qj-gzip-1.10
> > guix package: error:   second entry: gzip@1.10
> > /gnu/store/i2cdl0hvrml8hjdqplqln8didnvxkgp5-gzip-1.10
> > hint: You cannot have two different versions or variants of `gzip' in
> > the same profile.
> >
> >
> > where I tweak guix/scripts/environment.scm to export
> > `package-environment-inputs' and ~/tmp/manif-dep.scm contains:
> >
> > (use-modules (guix)
> >              (guix profiles)
> >              (guix scripts environment)
> >              (gnu packages package-management))
> >
> > (make-manifest (package-environment-inputs guix))
> 
> You’re doing it right!  It turns out that two different variants of
> “gzip” appear: one in ‘%final-inputs’ (the implicit inputs of
> ‘gnu-build-system’) and another one somewhere else, hence the collision.
> 
> The solution is to pass ‘--allow-collisions’, which is what ‘guix
> environment’ does by default precisely for that reason (see commit
> afd06f605bf88a796acefc7ed598b43879346a6b).
> 
> We could check exactly why we end up with several ‘gzip’ instances, but
> overall I think this kind of thing is hard to avoid for package inputs.
> 
> Thanks,
> Ludo’.
> 

Can "collisions" be collisions even if the targets are bit-identical?

E.g.

find /gnu -name '*gzip'|xargs sha1sum|gxsnip
--8<---------------cut here---------------start------------->8---
3a69ba705f2a8674fe6f0dfbdbf47de95bf72438  
/gnu/store/h0c398zan9ibhk4w0c944vp5pwgzkfpd-gzip-1.9/bin/gzip
3a69ba705f2a8674fe6f0dfbdbf47de95bf72438  
/gnu/store/q09sy224qnxrp982z4xfaxi19721mjx8-gzip-1.9/bin/gzip
c944319913ed9006b819abceda783ceee0985972  
/gnu/store/c6z3v1s9ky7h3wsc6da470s35iiciidd-profile/bin/gzip
c944319913ed9006b819abceda783ceee0985972  
/gnu/store/i2cdl0hvrml8hjdqplqln8didnvxkgp5-gzip-1.10/bin/gzip
c944319913ed9006b819abceda783ceee0985972  
/gnu/store/py3k9zla9fj3z7430v4crqj5pyrsd3qj-gzip-1.10/bin/gzip
--8<---------------cut here---------------end--------------->8---

It seems like it would be possible to automate an item-specific 
--allow-collisions
where the "collision" is really an aliasing?

(IOW, why use different names for the same thing, except for local convenience 
abbreviations?)

I see the de-duping gc does when it converts to hard links, and wonder there 
too.
What am I missing?

RFE:
(request for enlightenment :)
Exactly how are the /gnu/store prefixes computed? What _exactly_ is/are the 
input(s) that get hashed??

TIA
-- 
Regards,
Bengt Richter