bug#41956: [PATCH] ice-9: exceptions: Properly format the error message.

[Bengt Richter <bokr@bokr.com>]

Hi Maxim,

tl;dr:
Does module/ice-9/exceptions.scm use the default format?
Maybe (use-modules (ice-9) format) will help get to the next bug ?? :)

On +2020-06-20 01:46:13 -0400, maxim.cournoyer@gmail.com wrote:
> Maxim Cournoyer <maxim.cournoyer@gmail.com> writes:
> 
> > Hello,
> >
> > I had this problem in Guix where 'guix deploy my-config.scm' would
> > unhelpfully report an error like:
> >
> > guix deploy: error: failed to deploy my-host: ~A: ~S
> >
> > Digging a bit, I could reproduce at the REPL with:
> >
> > (guard (c ((message-condition? c)
> >            (format #t "error: ~a~%" (condition-message c))))
> >   ;; This is what (canonicalize-path "/do/not/exist) ends up doing:
> >   (throw 'system-error "canonicalize-path" "~A" '("No such file or directory")))
> >
> > --> error: ~A
> 
> [...]
> 
> Unfortunately the previous patch breaks the tests, with errors like:
> 
> ERROR: bytevectors.test: Datum Syntax: incorrect prefix - arguments: ((wrong-type-arg "apply" "Apply to non-list: ~S" (#\i) (#\i)))
> 
> I'm out of ideas for now, I last tried:
> 
> --8<---------------cut here---------------start------------->8---
> modified   module/ice-9/exceptions.scm
> @@ -189,7 +189,10 @@
>            ((subr msg margs . _)
>             (make-exception
>              (make-exception-with-origin subr)
> -            (make-exception-with-message msg)
> +            (let ((msg (if (null? margs)
> +                           msg
> +                           (apply simple-format #f msg margs))))
> +                (make-exception-with-message msg))
>              (make-exception-with-irritants margs)))
>            (_ (make-exception-with-irritants args)))
>           args))
> --8<---------------cut here---------------end--------------->8---
> 
> To the same effect.
> 
> Maxim
> 
> 
> 

HTH
-- 
Regards,
Bengt Richter