[Note: This concrete package is nonfree/Yoghurt-ware, but it's just
used here for showing the general problem, so I think it is OK to post
it here].

I renamed a package definition from "eclipse-java" to "java-eclipse".
Now upstream seams no longer be availabe:

$> ./pre-inst-env  guix build java-eclipse
[..]
@ build-started /gnu/store/lqfw971srfifgql68ibdgh58vi4d8fq3-java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz.drv - x86_64-linux /var/log/guix/drvs/lq//fw971srfifgql68ibdgh58vi4d8fq3-java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz.drv.bz2
guile: warning: failed to install locale
warning: failed to install locale: Invalid argument

Starting download of /gnu/store/dcjzplbvc27amcdgd9kffmyhskdw80d7-java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz
From https://www.eclipse.org/downloads/download.php?r=1&nf=1&file=/technology/epp/downloads/release/oxygen/3a/java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz...

ERROR: download failed "https://www.eclipse.org/downloads/download.php?r=1&nf=1&file=/technology/epp/downloads/release/oxygen/3a/java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz" 404 "Not Found"

Starting download of /gnu/store/dcjzplbvc27amcdgd9kffmyhskdw80d7-java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz
From http://mirror.hydra.gnu.org/file/java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz/sha256/0m7y7jfm059w01x9j5b5qkinjjmhkyygpjabhjf19fg2smxmwcim...
ERROR: download failed "http://mirror.hydra.gnu.org/file/java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz/sha256/0m7y7jfm059w01x9j5b5qkinjjmhkyygpjabhjf19fg2smxmwcim" 404 "Not Found"

Starting download of /gnu/store/dcjzplbvc27amcdgd9kffmyhskdw80d7-java-eclipse-oxygen-3a-linux-gtk-x86_64.tar.gz
From http://tarballs.nixos.org/sha256/0m7y7jfm059w01x9j5b5qkinjjmhkyygpjabhjf19fg2smxmwcim...
ERROR: download failed "http://tarballs.nixos.org/sha256/0m7y7jfm059w01x9j5b5qkinjjmhkyygpjabhjf19fg2smxmwcim" 404 "Not Found"

[...]

So, what you see here is that Guix is looking for the sources JUST by
hash on remote sites (Hydra, Nix).

But it does NOT search locally. Because I already have:

guix hash /gnu/store/56h6snwcawpzk6rhcwgk442wsx6k86q2-eclipse-java-oxygen-3a-linux-gtk-x86_64.tar.gz
0m7y7jfm059w01x9j5b5qkinjjmhkyygpjabhjf19fg2smxmwcim


If Guix searches remotely by hash, I would find it obvious that Guix
searches beforehand locally by hash. But it does not.

Björn