bug#31669: 'guix system' enhancements

[ludo@gnu.org (Ludovic Courtès)]

Hello,

Rutger Helling <rhelling@mykolab.com> skribis:

> That might cause confusion like you said, so I'm not sure if that would
> be an improvement.
>
> I guess I was wondering whether there was an easy way to do something
> like build your entire system with a newer Mesa, or use LibreSSL 
> instead of OpenSSL as mentioned. Of course you could change your own
> git checkout, but that's not as elegant as '--with-input/--with-graft'
> etc.

Another option would be to operate at the derivation level rather than
at the package level.  There’s a currently unused procedure called
‘map-derivation’ which is similar to what ‘--with-input’ does, except
that it’s at the derivation level.  Example:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> ,use(guix)
scheme@(guile-user)> ,use(gnu)
scheme@(guile-user)> (getcwd)
$2 = "/home/ludo/src/guix/guix"
scheme@(guile-user)> (define os (load "../gnu/system/examples/bare-bones.tmpl"))
scheme@(guile-user)> ,run-in-store (operating-system-derivation os)
$4 = #<derivation /gnu/store/x0ixll4myzk2s2g0lvq29qr5fx1hsgqi-system.drv => /gnu/store/4igvd1ynxjv3hk8qpf0l9bpb2v157hjf-system 4c209b0>
scheme@(guile-user)> ,use(gnu packages tls)
scheme@(guile-user)> ,run-in-store (package->derivation openssl)
$5 = #<derivation /gnu/store/8d4dim068nky5y8dls3p2nijc79jhhv1-openssl-1.0.2o.drv => /gnu/store/yvy6pj9b3rpb3wr98x0sjlxv5g9p5x5l-openssl-1.0.2o-doc /gnu/store/ggrpw6gh2rnqjwyjf99z8cdw5digc4hb-openssl-1.0.2o /gnu/store/9cdb2xydmm012v81l78jliird4f7dy25-openssl-1.0.2o-static 5594370>
scheme@(guile-user)> ,run-in-store (package->derivation libressl)
substitute: updating list of substitutes from 'https://berlin.guixsd.org'... 100.0%
$6 = #<derivation /gnu/store/2wds8bdyl25iqx63p2vv7fy05rbmq4s5-libressl-2.7.3.drv => /gnu/store/d9askfqx719bv3610kd6s3jqjh5rnfsh-libressl-2.7.3 538b1e0>
scheme@(guile-user)> (define s (open-connection))
scheme@(guile-user)> (map-derivation s $4 `((,$5 . ,$6)))
$7 = #<derivation /gnu/store/g9xxa9fkiaij5i9g8s71b04yswi69cig-system.drv => /gnu/store/x5gyjvmq663jhd1pc1pc5w46hpcghvwd-system 618bf00>
--8<---------------cut here---------------end--------------->8---

It’s a bit of a sledgehammer and ‘map-derivation’ may be buggy on the
edges, but worth exploring.  :-)

HTH,
Ludo’.