bug#43747: Spurious Guile warnings when working on a channel

[Ludovic Courtès]

Hello Guix!

When someone’s working on a channel, it’s typical to have that channel
already in your ‘guix’ and to use ‘guix build -L /path/to/checkout PKG’
to test a package from a working copy of the channel.  Here’s what it
looks like:

--8<---------------cut here---------------start------------->8---
$ cat ~/.config/guix/past-channels.scm 
(cons (channel
        (name 'guix-past)
        (url "https://gitlab.inria.fr/guix-hpc/guix-past";)
        (introduction
         (make-channel-introduction
          "0c119db2ea86a389769f4d2b9c6f5c41c027e336"
          (openpgp-fingerprint
           "3CE4 6455 8A84 FDC6 9DB4  0CFB 090B 1199 3D9A EBB5"))))
      %default-channels)
$ guix pull -p /tmp/test -C ~/.config/guix/past-channels.scm

[...]

$ /tmp/test/bin/guix build -L ~/src/guix-past/modules autoconf@2.59 -n
;;; note: source file 
/home/ludo/src/guix-past/modules/past/packages/assembly.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/assembly.go
;;; note: source file 
/home/ludo/src/guix-past/modules/past/packages/autotools.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/autotools.go
;;; found fresh local cache at 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/autotools.scm.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/backup.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/backup.go
;;; found fresh local cache at 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/backup.scm.go
;;; note: source file 
/home/ludo/src/guix-past/modules/past/packages/guile-xyz.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/guile-xyz.go
;;; found fresh local cache at 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/guile-xyz.scm.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/boost.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/boost.go
;;; found fresh local cache at 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/boost.scm.go
;;; note: source file 
/home/ludo/src/guix-past/modules/past/packages/graphviz.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/graphviz.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/maths.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/maths.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/maths.scm
;;;       newer than compiled 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/maths.scm.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/perl.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/perl.go
;;; found fresh local cache at 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/perl.scm.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/python.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/python.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/python.scm
;;;       newer than compiled 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/python.scm.go
;;; note: source file 
/home/ludo/src/guix-past/modules/past/packages/statistics.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/statistics.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/simgrid.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/simgrid.go
;;; found fresh local cache at 
/home/ludo/.cache/guile/ccache/3.0-LE-8-4.3/home/ludo/src/guix-past/modules/past/packages/simgrid.scm.go
;;; note: source file /home/ludo/src/guix-past/modules/past/packages/web.scm
;;;       newer than compiled 
/gnu/store/6b0ww9dxvfig7wdxqcyjs0hlw331la4z-guix-past/lib/guile/3.0/site-ccache/past/packages/web.go
/gnu/store/nah91czddjcb72ghx9kh2z6jwad0kh4d-autoconf-2.59
--8<---------------cut here---------------end--------------->8---

The problem as can be seen above is that all these Guile warnings are
confusing at best and useless: there’s nothing the user can do about
them.

Ludo’.