Re: [PATCH] improve nginx-service

["Clément Lassieur" <clement@lassieur.org>]

> I've been rethinking it, and I would like to use define-configuration 
> (from cups and dovecot) because it looks really good. But I don't want 
> to define the same config option for each possible block it can appear 
> in, and that's why I used (option). So I'm looking for a way to 
> dynamically define records for each block type, so they can be used more 
> consistently with what we have. Unfortunately, I don't see how I could 
> do that, if that is possible at all... Ludo, any idea? I'd like to be 
> able to write:
>
> (define-record-type* <nginx-option>
>    ...)
>
> (define-syntax option
>    (syntax-rule ()
>      (option mname mtype mdef mdoc mblocks))
>      (nginx-option (name mname) (type mtype) ...)))
>
> (define option-list (list
>    (option 'server-name server-name 'default "the name of the server that 
> is served by the http block" (list 'http))
>    ...))
>
> and then be able to create the block records by filtering that list:
>
> (define-nginx-configuration nginx-http-block
>    (filter ... option-list))
>
> (define-nginx-configuration nginx-events-block
>    (filter ... option-list))
>
> (define-nginx-configuration nginx-server-block
>    (filter ... option-list))
>
> So the user would then be able to write the service configuration as 
> they would for any other service we have. What I don't know is how to 
> write define-nginx-configuration (ideally it would call 
> define-configuration). With it, I can probably do the rest just fine. Or 
> maybe there is a better way I don't see yet?

I think you are looking for "eval".

(define (list->define-configuration stem fields)
  (eval `(define-configuration ,stem ,@fields) (current-module)))

(list->define-configuration 'some-configuration filtered-list)

I use it in a service I'm working on (Prosody), to handle virtualhosts.