That's neat! I'll play around with it later, thanks for the tip.

On Fri, 01 Jun 2018 22:35:26 +0200
ludo@gnu.org (Ludovic Courtès) wrote:

> 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
> 5594370> libressl) substitute: updating list of substitutes from
> 5594370> 'https://berlin.guixsd.org'... 100.0% $6 =
> 5594370> #<derivation /gnu/store/2wds8bdyl25iqx63p2vv7fy05rbmq4s5-libressl-2.7.3.drv
> 5594370> => /gnu/store/d9askfqx719bv3610kd6s3jqjh5rnfsh-libressl-2.7.3
> 5594370> 538b1e0> scheme@(guile-user)> (define s (open-connection))
> 5594370> 538b1e0> scheme@(guile-user)> (map-derivation s $4
> 5594370> 538b1e0> `((,$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’.