Re: Syntactic Diabetes (was Re: A friendlier API for operating-system declarations)

[Liliana Marie Prikler <liliana.prikler@gmail.com>]

Am Sonntag, dem 26.11.2023 um 17:49 +0100 schrieb Edouard Klein:
> Thank you Liliana and Attila for the swift and actionable feedback :)
> 
> Below is a revised proposition.
> 
> Here is a minimal working example of an os declaration:
> ------------------mwe.scm---------------
> (use-modules
>  (beaver system)
>  (beaver functional-services)
>  (gnu packages version-control)
>  (gnu services web)
>  (gnu services telephony)
>  (gnu services ssh)
>  (gnu services base)
>  (guix gexp))
> 
> (-> (minimal-ovh "osef")
>     (instantiate nginx)
I do wish you spelled out service.  Also, instantiate takes as much
characters to type as add-service.
>     (instantiate mumble-server
>                  (welcome-text "coucou")
>                  (port 64738))
>     (extend openssh `(("alice" ,(local-file
> "/home/edouard/.ssh/id_rsa.pub"))))
>     (modify openssh
>             (password-authentication? #f)
>             (allow-empty-passwords? #t))
>     (remove guix))
> -------------------------------------------------------
> 
> To see the value of this syntactic sugar, try to replicate this MWE
> with the standard syntax. It's not horrendous, but it *is* off-
> putting to many newcomers to git, whereas this sugary piece is more
> readable for them (sample size of 1, p=0.00000005).
Well, that'd be 
  (let ((base (minimal-ovh "osef")))
    (operating-system
      (inherit base)
      (services
        (cons*
         (service nginx-service-type)
         (service mumble-service-type
                  (mumble-configuration
                   (welcome-text "couocu")
                   (port 64738)))
         (service openssh-service-type
                  (openssh-configuation
                   (password-authentication? #f)
                   (allow-empty-passwords? #t)
                   (authorized-keys <your-keys)))
         (operating-system-user-services base))
or
  (-> (minimal-ovh "osef")
      (lambda (base) …))

On that note, we also have extend-openssh-authorized-keys for the use
with modify-services.

> Here is the revised functional-services.scm, not yet commited and
> pushed, and only lightly tested in local containers, but not in
> production:
> 
> Advice and comments welcome :)
> 
> 
> ------------functional-services.scm--------------
> 
> 
> (define-module (beaver functional-services)
>    #:use-module (gnu system)
>    #:use-module (gnu services)
>    #:export (instantiate extend modify remove))
> 
> (define syntax->string (compose symbol->string syntax->datum))
> 
> (define (service-configuration stx service)
>   "Return the syntax one can use to refer to xxx-configuration for
> the given
> service"
>   (datum->syntax stx (string->symbol
>                       (string-append
>                        (syntax->string service)
>                        "-configuration"))))
> 
> (define (service-type stx service)
>   "Return the syntax one can use to refer to xxx-service-type for the
> given
> service"
>   (datum->syntax stx (string->symbol
>                       (string-append
>                        (syntax->string service)
>                        "-service-type"))))
> 
> (define-syntax instantiate
>   (lambda (stx)
>     (syntax-case stx ()
>       [(_ os service-name)
>        (with-syntax
>         ([service-type (service-type stx #'service-name)])
>         #'(begin
>             ((lambda (x)  ;; It is wrapped in a lamba to make sure os
> is
>                ;; evaluated once only. It it wasn't in a labmda,
> whatever
>                ;; form os is in the calling code would be repeated
>                ;; multiple times, and so if the form was e.g. (some-
> func
>                ;; os), then some-func would be called multiple times,
>                ;; which may not be desirable.
Isn't it also wrapped in a lambda, because -> is a threading macro that
takes functions rather than syntax?


Cheers