bug#47569: ‘qt-build-system’ retains too many references via wrappers

[Ludovic Courtès]

Hi,

For the record, changing ‘qt-build-system’ would trigger a rebuild of
less than 400 packages according to the back-of-the-envelope calculation
below.  In that case, it’s tempting to fix on ‘master’ and include it in
the release.

Thoughts?

Ludo’.

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> ,use(gnu)
scheme@(guile-user)> ,use(guix build-system qt)
scheme@(guile-user)> ,use(guix)
scheme@(guile-user)> (define qtpkgs (fold-packages (lambda (pkg lst)
                                                     (if (eq? 
(package-build-system pkg) qt-build-system)
                                                         (cons pkg lst)
                                                         lst))
                                                   '()))
scheme@(guile-user)> (length qtpkgs)
$78 = 186
scheme@(guile-user)> ,use(guix graph)
scheme@(guile-user)> ,run-in-store (node-edges (@ (guix scripts graph) 
%reverse-package-node-type) (fold-packages cons '()))
$79 = #<procedure 7fe494f11520 at guix/graph.scm:94:17 (node)>
scheme@(guile-user)> (node-reachable-count qtpkgs $79)
$80 = 180
scheme@(guile-user)> (+ 186 180)
$81 = 366
--8<---------------cut here---------------end--------------->8---