From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: [PATCH 3/3] gnu: Add CUPS service.
Date: Mon, 10 Oct 2016 23:00:35 +0200
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	<20161007202424.26732-3-wingo@igalia.com>
	<874m4ktxi5.fsf@lassieur.org> <cuch98ktwfc.fsf@igalia.com>
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In-Reply-To: <cuch98ktwfc.fsf@igalia.com> (Andy Wingo's message of "Mon, 10
	Oct 2016 10:55:51 +0200")
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To: Andy Wingo <wingo@igalia.com>
Cc: guix-devel@gnu.org, =?utf-8?Q?Cl=C3=A9ment?= Lassieur <clement@lassieur.org>

Andy Wingo <wingo@igalia.com> skribis:

> On Mon 10 Oct 2016 10:32, Cl=C3=A9ment Lassieur <clement@lassieur.org> wr=
ites:
>
>>> +(define-record-type* <configuration-field>
>>> +  configuration-field make-configuration-field configuration-field?
>>> +  (name configuration-field-name)
>>> +  (type configuration-field-type)
>>> +  (getter configuration-field-getter)
>>> +  (predicate configuration-field-predicate)
>>> +  (serializer configuration-field-serializer)
>>> +  (default-value-thunk configuration-field-default-value-thunk)
>>> +  (documentation configuration-field-documentation))
>>> +
>>> +(define-syntax define-configuration
>>> +  (lambda (stx)
>>> +    (define (id ctx part . parts)
>>> +      (let ((part (syntax->datum part)))
>>> +        (datum->syntax
>>> +         ctx
>>> +         (match parts
>>> +           (() part)
>>> +           (parts (symbol-append part
>>> +                                 (syntax->datum (apply id ctx parts)))=
)))))
>>> +    (syntax-case stx ()
>>> +      ((_ stem (field (field-type def) doc) ...)
>>> +       (with-syntax (((field-getter ...)
>>> +                      (map (lambda (field)
>>> +                             (id #'stem #'stem #'- field))
>>> +                           #'(field ...)))
>>> +                     ((field-predicate ...)
>>> +                      (map (lambda (type)
>>> +                             (id #'stem type #'?))
>>> +                           #'(field-type ...)))
>>> +                     ((field-serializer ...)
>>> +                      (map (lambda (type)
>>> +                             (id #'stem #'serialize- type))
>>> +                           #'(field-type ...))))
>>> +           #`(begin
>>> +               (define-record-type* #,(id #'stem #'< #'stem #'>)
>>> +                 stem #,(id #'stem #'make- #'stem) #,(id #'stem #'stem=
 #'?)
>>> +                 (field field-getter (default def))
>>> +                 ...)
>>> +               (define #,(id #'stem #'stem #'-fields)
>>> +                 (list (configuration-field
>>> +                        (name 'field)
>>> +                        (type 'field-type)
>>> +                        (getter field-getter)
>>> +                        (predicate field-predicate)
>>> +                        (serializer field-serializer)
>>> +                        (default-value-thunk (lambda () def))
>>> +                        (documentation doc))
>>> +                       ...))))))))
>>> +
>>> +(define (serialize-configuration config fields)
>>> +  (for-each (lambda (field)
>>> +              ((configuration-field-serializer field)
>>> +               (configuration-field-name field)
>>> +               ((configuration-field-getter field) config)))
>>> +            fields))
>>> +
>>> +(define (validate-configuration config fields)
>>> +  (for-each (lambda (field)
>>> +              (let ((val ((configuration-field-getter field) config)))
>>> +                (unless ((configuration-field-predicate field) val)
>>> +                  (cups-configuration-field-error
>>> +                   (configuration-field-name field) val))))
>>> +            fields))
>>
>> These definitions are also in the Dovecot service. Would it make sense
>> to put them in a place where they could be accessible from other
>> services as well, thus avoiding code repetition?
>
> Yes, it's a good idea.  I was holding off doing it until the third
> service that used them, though, just to avoid prematurely making an
> abstraction that might be the wrong thing; dunno.  WDYT?

I think Cl=C3=A9ment has a point.  ;-)  Maybe in a subsequent patch it could
be moved as-is to (gnu services configuration) or something along these
lines?

Thanks,
Ludo=E2=80=99.