(address . bug-guix@gnu.org)
$ guix build --no-grafts --derivations -e \
'(begin
(use-modules (guix packages) (gnu packages gtk))
((package-mapping identity) cairo-sans-poppler))' \
-e '(@ (gnu packages gtk) cairo-sans-poppler)'
=>
/gnu/store/51hwf2mc2ig76a3nm86msv4z9az3s0j3-cairo-1.16.0.drv
/gnu/store/q78ziqcg2dvi2lzj18hzdld85bcydzwk-cairo-1.16.0.drv
Some interesting notes:
1. (package-mapping identity #:deep? #t) *does* produce the same
derivation.
2. bag->derivation's `delete-duplicates' call uses `input=?', but its
input objects in the second tuple position are all <gexp-input>s
produced by `expand-input'. Consequently, `input=?' will fall back
to using `equal?' instead of `derivation=?'. I don't know to what
extent this has to do with the observed bug.
- ulfvonbelow
-----BEGIN PGP SIGNATURE-----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=G53s
-----END PGP SIGNATURE-----