[bug#55420] [PATCH 0/2] Add a function to parse emacs elisp's package header

[Ludovic Courtès]

Hi Fredrik,

The patches LGTM modulo cosmetic issues:

Fredrik Salomonsson <plattfot@posteo.net> skribis:

> * guix/build/emacs-utils.scm (emacs-batch-script): New procedure.

[...]

> +(define (emacs-batch-script expr)
> +  "Execute the Elisp code EXPR in Emacs batch mode and return output."
> +  (call-with-port
> +      (open-pipe*
> +       OPEN_READ
> +       (%emacs) "--quick" "--batch"
> +       (string-append "--eval=" (expr->string expr)))
> +    read-string))

I suggest something like:

  (let* ((pipe (open-pipe* …))
         (output (read-string pipe))
         (status (close-pipe pipe)))
    (unless (zero? status)
      ;; Use SRFI-34 + either a &message condition or (better)
      ;; a dedicate SRFI-35 condition type for the error.
      (raise (condition …)))
    output)

That way, execution failures would be caught and reported.

Ludo’.