Re: Best practices for writing services

[Xinglu Chen]

On Thu, Apr 22 2021, raingloom wrote:

>> One thing that I find a little annoying is that you have to specify a
>> default value for the fields.
>
> Are you sure? If you don't specify a default, won't the user just be
> forced to write
> (service whatever
>       (whatever-configuration
>               (mandatory-field 'bleepbloop)))
>
> instead of the shorter (service whatever)?

If I write something like this

#+begin_src scheme
(use-modules (gnu services configuration))
(define (serialize-list field-name val) "")
(define-configuration test-config
  (config
   (list)
   "configuration for test"))
#+end_src

and evaluate it, I will get an error.  I have to specify a default value
for the ‘config’ field to make it work.

#+begin_src scheme
(use-modules (gnu services configuration))
(define (serialize-list field-name val) "")
(define-configuration test-config
  (config
   (list '())                           ;default to '()
   "configuration for test"))
#+end_src