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)
(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).
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.
(operating-system
(inherit x)
(services
(cons
(service service-type)
(operating-system-user-services x)))))
os)))]
[(_ os service-name forms ...)
(with-syntax
([service-type (service-type stx #'service-name)]
[service-configuration (service-configuration stx #'service-name)])
#'(begin
((lambda (x) ;; Wrapping in a lambda for the same reasons as above
(operating-system
(inherit x)
(services
(cons
(service service-type
(service-configuration forms ...))
(operating-system-user-services x)))))
os)))])))
(define-syntax extend
(lambda (stx)
(syntax-case stx ()
[(_ os service-name forms ...)
(with-syntax
([service-type (service-type stx #'service-name)])
#'(begin
((lambda (x)
(operating-system
(inherit x)
(services
(cons
(simple-service (format #f "A ~a extension" (syntax->string
#'service-name))
service-type
forms ...)
(operating-system-user-services x)))))
os)))])))
(define-syntax modify
(lambda (stx)
(syntax-case stx ()
[(_ os service-name forms ...)
(with-syntax
([service-type (service-type stx #'service-name)]
[service-configuration (service-configuration stx #'service-name)])
#'(begin
((lambda (x)
(operating-system
(inherit x)
(services
(modify-services (operating-system-user-services x)
(service-type
config =>
(service-configuration
(inherit config)
forms ...))))))
os)))])))
(define-syntax remove
(lambda (stx)
(syntax-case stx ()
[(_ os service-name forms ...)
(with-syntax
([service-type (service-type stx #'service-name)])
#'(begin
((lambda (x)
(operating-system
(inherit x)
(services
(modify-services (operating-system-user-services x)
(delete service-type)))))
os)))])))
-------------------------
Attila Lendvai <[email protected]> writes:
>> (service+ OS SERVICE [CONF])
>> (service- OS SERVICE)
>> (modify-service OS SERVICE UPDATE)
>
>
> what would the benefit of generating multiple macros for each service
> compared to the above functional API (with 3-4 elements altogether)?
>
> i could be missing something here, but it seems to be precious little to me
> while it costs some extra complexity.
>
> if i were to add a syntactic abstraction for this, i'd generate a full DSL in
> the form of a (modify-operating-system OS [fictional DSL to describe desired
> changes]).
>
> but i don't think the extra complexity justifies any macrology here.
>
> --
> • attila lendvai
> • PGP: 963F 5D5F 45C7 DFCD 0A39
