bug#71193: Shepherd fails to start a system when given an incorrect form to the start field of any service

[Ludovic Courtès]

Hi Picnoir,

"Picnoir" <picnoir@alternativebit.fr> skribis:

> I think the following snippet is a good minimal reproducer for this. Add
> this service to a guix system configuration:
>
> --8<---------------cut here---------------start------------->8---
> (simple-service
>  'shepherd-bug-repro
>  shepherd-root-service-type
>  (list (shepherd-service
>         (documentation "shepherd hang minimal repro")
>         (provision '(shepherd-bug-repro))
>         (requirement '())
>         (start #~('())))))
> u--8<---------------cut here---------------end--------------->8---
>
> ⚠ DO NOT BOOT ON A CRITICAL SYSTEM WITH THIS SERVICE, IT'LL BRICK IT ⚠
>
> You can create a VM for this system and start it. The VM hangs after the
> log line "creating /etc/machine-id...", before any shepherd service gets
> started.

[...]

> Tested on Shepherd 0.10.4 with the Guix revision
> c5e63e19ac672f9e63fc8ee98fa9a16f978ce19c.

This sounds very much like <https://issues.guix.gnu.org/71144>, which
was fixed in Guix commit cca25a67693bb68a1884a081b415a43fad1e8641,
shortly after the commit you mention.

I tested the reproducer you posted in a VM and it boots fine.  The
problem simply leads to an error message in /var/log/messages:

--8<---------------cut here---------------start------------->8---
Jun 26 15:43:09 localhost vmunix: [    3.574026] shepherd[1]: Exception caught 
while loading 
'/gnu/store/c44hd3gfksalrbsgc3a0ax4v9jmnkzb4-shepherd-shepherd-bug-repro.go': 
#<&compound-exception components: (#<&assertion-failure> #<&origin origin: #f> 
#<&message message: "Wrong type to apply: ~S"> #<&i
Jun 26 15:43:09 localhost vmunix: [    3.574132] rritants irritants: (())> 
#<&exception-with-kind-and-args kind: wrong-type-arg args: (#f "Wrong type to 
apply: ~S" (()) (()))>)>
Jun 26 15:43:09 localhost vmunix: [    3.583838] shepherd[1]: starting 
services...
Jun 26 15:43:09 localhost vmunix: [    3.585444] shepherd[1]: Configuration 
successfully loaded from 
'/gnu/store/8cch4dv5ca1v0hsgyr6d8jay513x7d8g-shepherd.conf'.
--8<---------------cut here---------------end--------------->8---

… and of course the faulty service doesn’t show up at all in ‘herd
status’.

Could you confirm it’s fine for you?

Thanks,
Ludo’.