Re: Multiple profiles with Guix Home

[Liliana Marie Prikler <liliana.prikler@gmail.com>]

Hi,

Am Dienstag, dem 24.05.2022 um 14:55 +0300 schrieb Andrew Tropin:
> On 2022-05-23 19:05, Liliana Marie Prikler wrote:
> > [...]
> > I don't think I agree with this choice.  To satisfy both my own use
> > case of serving profiles in different locations from another and
> > another issue being raised w.r.t. configuring the location of the
> > .guix-home profile, I think we should make a triple of location,
> > optional short name, and manifest (which may be generated from
> > packages implicitly).  WDYT?
> > 
> 
> This service is intended for profiles managed by Guix Home, so every
> profile MUST be a part of home-environment (~/.guix-home is a symlink
> to it).  I don't see any meaningful reasons to make it possible to
> customize the path inside home-environment.
Why though?  The decision to restrict Guix Home to dotfiles was already
a bad one that has since been overturned, so I think we should
carefully evaluate why "~/.guix-home" even is special.  In my point of
view, any path that is prefixed with the user's home ought to be fair
game, as should be constructing intermediate per-user profile symlinks
in /var/guix.

> If you want to have profiles like ~/work/my-project/guix-profile or
> ~/.guix/profiles/my-python-environment managed by Guix Home you can
> implement home-external-profiles-service-type, which can extended
> activation service or any other impure tricks, but I would advice
> against it.  I suggest either manage a profile with
> home-[additional-]-profiles or manage them externally and load with
> home-profile-paths/home-profile-loader.
Pardon me if I was confusing, but I meant to have one service defining
the existence of ~/work/my-project/guix-profile (that being home-
profiles-service-type) and another to load it (that being home-profile-
loader-service-type).  Admittedly, the existing way of specifying a
profile that is loaded becomes more work then, so perhaps we can add
some syntactic sugar to that, so that both services get extended at
once.

> > Considering the above, I think a rough roadmap would be:
> > 1. Implementing home-profiles-service-type (to build the profiles)
> > 2. Implementing home-profile-loader-service-type
> 
> This one looks simplier and also independent from #1, so I would
> recommend to start with it.  Also, it's very likely that
> home-profiles-service-type will be extending
> home-profile-loader-service-type
I thought about it for some while, but I really don't think either is
easier than the other, particularly in the way I described it, where
home-profiles-service-type and home-profile-loader-service-type are
orthogonal to each other.

> > 3. ???
> > 4. Deprecate the existing home-profile-service-type in favor of the
> > new profile service type pair and/or implement it in terms of it.
> > where (1) and (2) could be done by two people/teams in parallel.
> 
> The migration should be quite simple here.
> 
> JFYI: The design of Guix Home is flexible, essential services can be
> completely customized, even symlink-manager can be removed or
> substituted with something else (for example to make a read-only home
> workflow proposed by Julien Lepiller in guix-home-manager).  This is
> also used in rde to substitute home-shell-profile-service-type with
> alternative implementation:
> https://git.sr.ht/~abcdw/rde/tree/master/item/rde/features.scm#L234
I'm not sure if I'm that fond of this design choice – it reminds me a
bit about OOP horrors I was forced to learn.  Anyway, I don't think
it's relevant, as...

> This way you can experiment with multi-profile approach even without
> modifying existing code.
I was planning to run guix home from checkout with $HOME in /tmp anyway
for testing purposes.

> > Given that the task has been simplified, I think I might start
> > coding on it, but I can't promise any particular deadline.  At the
> > moments both my day job and review work delay any other
> > contributions towards Guix.
> > 
> > Cheers
> 
> I also advice to treat it as an experiment.  IMO Guix Home should be
> relatively conservative, stable and simple.  Other advanced workflows
> in most cases should be implemented and maintained separately and be
> optionally pluggable in Guix Home by overriding essential services or
> any other way.  In cases such workflows demonstrates their benifits
> without compromising simplicity, they can be included.
I initially planned for the new stuff to be backwards compatible by way
of sanitizers.  That probably still works for the design we have
currently, though YMMV.

Cheers