Subject: Re: bug#41140: “guix system” suggests wrong module import when using “remove”

From: Ludovic Courtès <[email-masked]>
Date: Mon, 11 May 2020 22:22:36 +0200

Hi,

Ricardo Wurmus <[email-masked]> skribis:

>>>From 40c1208cbe9cbfa58ee385ef6ee06b775d309753 Mon Sep 17 00:00:00 2001
> From: Ricardo Wurmus <[email-masked]>
> Date: Sun, 10 May 2020 23:29:38 +0200
> Subject: [PATCH] services: Support DELETE in MODIFY-SERVICES macro.
>
> * gnu/services.scm (%modify-service): Add clause for DELETE syntax.
> (modify-services): Use FILTER-MAP; adjust docstring.
> * doc/guix.texi (System Services): Mention alternative syntax.
> (X Window): Use MODIFY-SERVICES syntax.

I like it!

> -  #:use-module (srfi srfi-1)
> +  #:use-module ((srfi srfi-1) #:hide (delete))
>    #:use-module (srfi srfi-9)
>    #:use-module (srfi srfi-9 gnu)
>    #:use-module (srfi srfi-26)
> @@ -272,7 +273,11 @@ singleton service type NAME, of which the returned service is an instance."
>      (service type value)))
>  
>  (define-syntax %modify-service
> -  (syntax-rules (=>)
> +  (syntax-rules (=> delete)
> +    ((_ svc (delete kind) clauses ...)
> +     (if (eq? (service-kind svc) kind)
> +         #f
> +         (%modify-service svc clauses ...)))

Best practice suggests that ‘delete’ should be bound (info "(guile)
Syntax Rules"):

--8<---------------cut here---------------start------------->8---
   Although literals can be unbound, usually they are bound to allow
them to be imported, exported, and renamed.  *Note Modules::, for more
information on imports and exports.  In Guile there are a few standard
auxiliary syntax definitions, as specified by R6RS and R7RS:
--8<---------------cut here---------------end--------------->8---

Now, if we export a new ‘delete’ binding from here, it’ll annoy
everyone.  So perhaps we can keep the srfi-1 ‘delete’ and re-export it,
as done in (guix build utils)… though that situation is also annoying
because we get warnings saying that it collides with core ‘delete’.

Dunno, give it a try!

Ludo’.