bug#44525: Derivation of computed-file has no outputs

[Stefan]

Hi!

I try to use a computed-file as an input to a bootloader profile hook function. 
Using guix system I get this error message:

guix system: error: reference to invalid output 'out' of derivation 
'/gnu/store/946szbrwn3ja74yjnibbhjisjflvsk73-test.txt.drv'

This is the simple definition of the computed-file:

(computed-file "test.txt" (with-imported-modules '((guix utils)) 
#~(%current-system)))

And this is the content of the generated derivation of it:

Derive([],[("/gnu/store/0hcx4wgpgf1nn4gl3lhnd055vj2y28cj-guile-3.0.2.drv",["out"]),("/gnu/store/2ss1lzy0x0wwayy5n5mvzmsv77dnni39-module-import-compiled.drv",["out"])],["/gnu/store/9lw2pp0hjcjgmq5hx7w6aq92699r6pim-module-import","/gnu/store/plgbvrkkq1ghvph24kf0bdgb4w8glgqb-test.txt-builder"],"aarch64-linux","/gnu/store/x3gq648qnfnla7nppyfjvj62s2i8y7rl-guile-3.0.2/bin/guile",["--no-auto-compile","-L","/gnu/store/9lw2pp0hjcjgmq5hx7w6aq92699r6pim-module-import","-C","/gnu/store/3v6bh2hn62i4qp674d1hqg4ca7hpys3a-module-import-compiled","/gnu/store/plgbvrkkq1ghvph24kf0bdgb4w8glgqb-test.txt-builder"],[("preferLocalBuild","1")])

I think the problem is visible already with this call:

scheme@(guile-user)> (derivation-path->output-paths 
"/gnu/store/946szbrwn3ja74yjnibbhjisjflvsk73-test.txt.drv")
$5 = ()


Bye

Stefan