Hello Pierre,

Good catch!  I prepared a patch in the attachement bellow to fix this.

Also the patch changes behavior of '--format=channels' for
'GUIX_PACKAGE_PATH' warning.  It will print to STDERR instead of STDOUT.

Pierre Neidhardt <mail@ambrevar.xyz> writes:

>> guix describe --format=json
> [{"name":"guix","url":"https://git.savannah.gnu.org/git/guix.git","commit":"77f3d3036406b1d1ceaeba8017ae5f597f2a0fb4"}]
> Backtrace:
>            4 (primitive-load "/home/ambrevar/.config/guix/current/bin/guix")
> In guix/ui.scm:
>   1654:12  3 (run-guix-command _ . _)
> In ice-9/boot-9.scm:
>     829:9  2 (catch srfi-34 #<procedure 2ff58a0 at guix/ui.scm:624:2 ()> #<procedure 7f711b6c39b8 at guix/ui.scm:624:2 (key c)> _)
>     829:9  1 (catch system-error #<procedure 2ff5940 at guix/scripts/describe.scm:203:4 ()> #<procedure 7f711b6c39d0 at guix/ui.scm:750:6 (key proc format-string format-args . rest)> _)
> In guix/scripts/describe.scm:
>      83:5  0 (display-package-search-path json)
>
> guix/scripts/describe.scm:83:5: In procedure display-package-search-path:
> Throw to key `match-error' with args `("match" "no matching pattern" json)'.

JSON format:
--8<---------------cut here---------------start------------->8---
oleg@guixsd ~/src/guix$ ./pre-inst-env env GUIX_PACKAGE_PATH=$HOME/src/guix-wigust:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist guix describe -p ~/.config/guix/current --format=json
[{"name":"guix","url":"https://gitlab.wugi.info/guix/guix.git","commit":"4161deb4549c39b7d4801cc8aa63c365d19fc649"},{"name":"guix-wigust","url":"https://gitlab.wugi.info/guix/guix-wigust.git","commit":"f6dfa5fc08824ebe5bdc42ea35ff0e040245c8c0"}]
{"name":"GUIX_PACKAGE_PATH","paths":["/home/oleg/src/guix-wigust","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist","/tmp/noexist"]}
--8<---------------cut here---------------end--------------->8---

>> guix describe -f recutils
> name: guix
> url: https://git.savannah.gnu.org/git/guix.git
> commit: 77f3d3036406b1d1ceaeba8017ae5f597f2a0fb4
>
> Backtrace:
>            4 (primitive-load "/home/ambrevar/.config/guix/current/bin/guix")
> In guix/ui.scm:
>   1654:12  3 (run-guix-command _ . _)
> In ice-9/boot-9.scm:
>     829:9  2 (catch srfi-34 #<procedure 2ac1d20 at guix/ui.scm:624:2 ()> #<procedure 7fa6695719b8 at guix/ui.scm:624:2 (key c)> _)
>     829:9  1 (catch system-error #<procedure 2ac1dc0 at guix/scripts/describe.scm:203:4 ()> #<procedure 7fa6695719d0 at guix/ui.scm:750:6 (key proc format-string format-args . rest)> _)
> In guix/scripts/describe.scm:
>      83:5  0 (display-package-search-path recutils)
>
> guix/scripts/describe.scm:83:5: In procedure display-package-search-path:
> Throw to key `match-error' with args `("match" "no matching pattern" recutils)'.

recutils format:
--8<---------------cut here---------------start------------->8---
oleg@guixsd ~/src/guix$ ./pre-inst-env env GUIX_PACKAGE_PATH=$HOME/src/guix-wigust:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist:/tmp/noexist guix describe -p ~/.config/guix/current --format=recutils
name: guix
url: https://gitlab.wugi.info/guix/guix.git
commit: 4161deb4549c39b7d4801cc8aa63c365d19fc649

name: guix-wigust
url: https://gitlab.wugi.info/guix/guix-wigust.git
commit: f6dfa5fc08824ebe5bdc42ea35ff0e040245c8c0

name: GUIX_PACKAGE_PATH
paths: /home/oleg/src/guix-wigust /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist
+ /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist
+ /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist /tmp/noexist

--8<---------------cut here---------------end--------------->8---