Re: [PATCH 3/3] gnu: Add CUPS service.

[Ludovic Courtès]

Andy Wingo <address@hidden> skribis:

> On Mon 10 Oct 2016 10:32, Clément Lassieur <address@hidden> writes:
>
>>> +(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 Clément 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’.