Is the example about the serialiser in the manual correct? Was: Help on writing config serialiser

[Simon Streit <simon@netpanic.org>]

Hello,

I gave up, and thought of starting from scratch.  But my initial attempt
failed right from the beginning.

I'm not so sure now if the example provided in the manual is usable in
its current state.  The following is a (slightly) unedited copy from the
manual:

--8<---------------cut here---------------start------------->8---
(use-modules (gnu services)
             (guix gexp)
             (gnu services configuration)
             (srfi srfi-26)
             (srfi srfi-1))

;; Turn field names, which are Scheme symbols into strings
(define (uglify-field-name field-name)
  (let ((str (symbol->string field-name)))
    ;; field? -> is-field
    (if (string-suffix? "?" str)
        (string-append "is-" (string-drop-right str 1))
      str)))

(define (serialize-string field-name value)
  #~(string-append #$(uglify-field-name field-name) " = " #$value "\n"))

(define (serialize-integer field-name value)
  (serialize-string field-name (number->string value)))

(define (serialize-boolean field-name value)
  (serialize-string field-name (if value "true" "false")))

(define (serialize-contact-name field-name value)
  #~(string-append "\n[" #$value "]\n"))

(define (list-of-contact-configurations? lst)
  (every contact-configuration? lst))

(define (serialize-list-of-contact-configurations field-name value)
  #~(string-append #$@(map (cut serialize-configuration <>
                                contact-configuration-fields)
                           value)))

(define (serialize-contacts-list-configuration configuration)
  (mixed-text-file
   "contactrc"
   #~(string-append "[Owner]\n"
                    #$(serialize-configuration
                       configuration contacts-list-configuration-fields))))

(define-maybe integer)
(define-maybe string)

(define-configuration contact-configuration
  (name
   (string)
   "The name of the contact."
   serialize-contact-name)
  (phone-number
   (maybe-integer 'disabled)
   "The person's phone number.")
  (email
   (maybe-string 'disabled)
   "The person's email address.")
  (married?
   (boolean)
   "Whether the person is married."))

(define-configuration contacts-list-configuration
  (name
   (string)
   "The name of the owner of this contact list.")
  (email
   (string)
   "The owner's email address.")
  (contacts
   (list-of-contact-configurations '())
   "A list of @code{contact-configuation} records which contain
     information about all your contacts."))

;; A contacts list configuration could then be created like this:

(define my-contacts
  (contacts-list-configuration
   (name "Alice")
   (email "alice@example.org")
   (contacts
    (list (contact-configuration
           (name "Bob")
           (phone-number 1234)
           (email "bob@gnu.org")
           (married? #f))
          (contact-configuration
           (name "Charlie")
           (phone-number 0000)
           (married? #t))))))
--8<---------------cut here---------------end--------------->8---


Evaluating it with will result:

--8<---------------cut here---------------start------------->8---
~ $ guile example.scm
;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the --no-auto-compile argument to disable.
;;; compiling /home/ss2/example.scm
;;; compiled /home/ss2/.cache/guile/ccache/3.0-LE-8-4.5/home/ss2/example.scm.go
Backtrace:
In ice-9/boot-9.scm:
  1752:10  9 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
           8 (apply-smob/0 #<thunk 7f3e06d30080>)
In ice-9/boot-9.scm:
    724:2  7 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
In ice-9/eval.scm:
    619:8  6 (_ #(#(#<directory (guile-user) 7f3e06d36c80>)))
In ice-9/boot-9.scm:
   2835:4  5 (save-module-excursion _)
  4380:12  4 (_)
In /home/ss2/example.scm:
     75:2  3 (_)
In srfi/srfi-1.scm:
    634:9  2 (for-each #<procedure 7f3e00139500 at gnu/services/con…> …)
In gnu/services/configuration.scm:
   121:24  1 (_ #<<configuration-field> name: contacts type: list-of…>)
In srfi/srfi-1.scm:
    241:2  0 (every _ _ . _)

srfi/srfi-1.scm:241:2: In procedure every:
In procedure every: Wrong type argument: #<syntax-transformer contact-configuration?>
--8<---------------cut here---------------end--------------->8---

Maybe something is wrong? 


Kind regards
Simon