Re: Multiple profiles with Guix Home

[Andrew Tropin <andrewtropin@gmail.com>]

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On 2021-10-03 12:50, Liliana Marie Prikler wrote:

> Hi Guix,
>
> it's been a while since the discussion of whether or not to collect
> multiple profiles into a single directory [1].  This suggestion takes
> inspiration from that, but goes a vastly different route.  Instead of
> using environment variables to control Guix, it takes advantage of the
> recently added Guix Home, even if it is still a technical preview.
>
> So, what's the proposition?  I suggest we modify home-profile-service-
> type (or add a new service) such that it takes a list of <home-profile> 
> records instead of a list of packages.  This record would be defined as
>
>   (define-record-type* <home-profile> home-profile
>     make-home-profile home-profile? this-home-profile
>     (location home-profile-location) ; string, e.g. $HOME/.guix-profile
>     (short-name home-profile-short-name) ; string or #f, if given
>                                          ; construct a symlink in
>                                          ; /var/guix/.../per-user/
>     (manifest %home-profile-manifest) ; <manifest> or #f
>     (packages home-profile-packages) ; list of <package> or #f
>                                      ; fallback for manifest
>     (enabled? home-profile-enabled?) ; boolean, default #t
>     [...])
>
>   (define (home-profile-manifest home-profile)
>     (or (%home-profile-manifest home-profile)
>         (and=> (home-profile-packages home-profile) 
>                packages->manifest))))
>
> On init/reconfigure, `guix home' creates/updates all home-profiles
> which have a home-profile-manifest that is not #f and links them to the
> appropriate locations.  It also creates a shell startup script that
> loads those profiles that are enabled?, even if they have no manifest
> (this can be used to e.g. declare a pull profile, which `guix home'
> can't manage).  
>
> Some existing home services would need to be adapted towards this
> multiple profile usage.  For instance, home-fontconfig-service-type
> would need to accept a list of directories, rather than hardcode its
> value.
>
> What do y'all think?
>
> <https://lists.gnu.org/archive/html/guix-devel/2019-12/msg00358.html>
>
>

The discussion seems too heated and bloated, it's hard to reasonably
address arguments mentioned around, so I'll just post some thoughts and
a possible way to somehow proceed.

I suggest to split the bigger idea into smaller pieces, play with the
implementation locally/in fork/branch and see how it goes:

1. home-profiles-paths-service-type.  It will allow to add code for
sourcing profiles in setup-environment script and thus implement
workflows with multiple profiles.  Such profiles can be managed
externally or in the future built as a part of home environment.

2. home-[additional-]profiles-service-type.  It will allow to build
profiles from list of packages, optionally add a profile to
home-profiles-paths.  It will make ~/.guix-home/profiles/{emacs,web,etc}

To make it possible for other service to utilize multiple profiles, this
service will be extandable with values like that:

`((default . ,(list curl wget))
  (web . ,(list browser-ad-block-plugin))
  (emacs . ,(list emacs emacs-cider emacs-modus-themes)))

3. Maybe migrate ~/.guix-home/profile to ~/.guix-home/profiles/default.
  
I still can see a lot of potential problems related to search paths,
however part of them can be solved by duplicating packages in different
profiles or using dummy packages like emacs-consumer:
https://git.sr.ht/~abcdw/rde/tree/master/item/rde/packages/emacs.scm#L56

Also, I can see potential complication of Guix Home in general due to
multiple profiles capabilities and I still not sure that it worth the
benefits mentioned below:

I agree that multiple profiles can be benifitial for both better package
organization/structuring needs and faster build/reconfigure times.

I also see some demand from people requesting such a feature.

Liliana, if you still into it, I suggest to start with something
similiar to what I described above, share the draft implementation and
intermediate results/impression in a separate thread and continue the
further discussion.

-- 
Best regards,
Andrew Tropin

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