Re: Proof of Concept: Import Emacs' use-packaged packages into Guix' manifest.scm

[Andrew Tropin <andrew@trop.in>]

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On 2022-12-20 09:16, Mekeor Melire wrote:

> 2022-12-18 09:11 liliana.prikler@gmail.com:
>
>> I think we should be able to build an Emacs service in Guix Home that can 
>> manage init.el. As a workaround, use-package should also have a :when 
>> clause, so you can use :when (featurep 'some-package-autoloads) if you're 
>> unsure whether 'some-package is actually installed. This makes your init 
>> file a little more resilient and is particularly useful with pure shells.
>
> =guix home import= for init.el is a great idea! (See below for use-cases.)
>
> And yes, =:when (featurep 'some-package-autoloads)= is a workaround that makes 
> init.el files loadable even if respective packages are not available. But the 
> submitted code aims to enable you to install needed emacs-packages so that 
> such a restricting workaround is not needed.
>
>> Given the caveats, I would rather like to see an Emacs Lisp based script 
>> that mocks use-package and generates a manifest by evaluting init.el. This 
>> should give you more correct results. It's not a bad idea per se, but as-is, 
>> I think it would better be maintained in your own channel before 
>> upstreaming.
>
> Problem is that in cases where needed packages are not installed and the user 
> did not add =:when (featurep 'foo)= everywhere, it's possible that evaluating 
> init.el will fail because of some package not being available. Thus, IMHO, we 
> can't rely on Emacs to evaluate the init.el. But we could use Emacs to expand 
> the (use-package) macros inside init.el. But I doubt that it's worth it. I 
> rather think it's easier to use Guile to parse invocations of =require= and 
> =use-package=.
>
>> For upstreaming, I see two potential paths. The first one would be 
>> integration to `guix home import', which Andrew Tropin (CC'd) could probably 
>> tell you more on. The second would be integration into `guix package' as a 
>> callable function/command line argument, but IMHO that's less likely to 
>> pass.
>
> All in all, I think there are three use-cases:
>
> - If you want Guix Home to handle the installation of emacs- packages, there 
>   should be =guix home import= to automatically install those packages, as 
>   resulting from early- and init.el files.

guix home import doesn't install anything, it only generates a configuration.

>
> - If you simply want to install all emacs- packages once per CLI, there should 
>   be =guix package --install-from-elisp-file=~/.emacs.d/init.el= and similar 
>   CLI-arguments or -commands, such as --install-from-elisp-expression, 
>   --install-from-elisp-init-files. There could also be --fit-to-elisp- 
>   variants which not only install packages, but also remove redundant, unused 
>   emacs-* packages.

I don't think we want a separate tricky flags here.  Especially we don't
want some implicit logic removing unused packages.  Just
--8<---------------cut here---------------start------------->8---
guix package --install-from-expression=\
((@ (mekeor emacs-helper) generate-package-from-elisp) \
 #:elisp (local-file "./init.el"))
--8<---------------cut here---------------end--------------->8---
should be enough.  If you want to be sure unused packages are not
installed just don't use imperative guix package and maintain you
configuration in declarative manner.

>
> - If you want to use a manifest.scm for your Guix user-profile and
> import appropriate emacs- therein, there should be Guile modules and
> functions which allow to do so, as the submitted code does. Those
> modules could also be used with =guix package -e=.
>
> And in all three cases, your early- and init.el files might load packages via 
> =require= or =use-package= at least.

-- 
Best regards,
Andrew Tropin

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