Re: Odd behavior with --dry-run and --upgrade

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> I have zero knowledge in grafting, but if I checked it right, the
> attached patch should disable grafting for the emacs interface (when
> dry-run is on).  If you think it should be a part of a bigger
> dry-run+no-grafts patch, please use it.

Two separate patches is fine, IMO.

> From d7747453bf31a616d414dce293fc0556d601abcb Mon Sep 17 00:00:00 2001
> From: Alex Kost <alezost@gmail.com>
> Date: Wed, 27 Jul 2016 14:55:50 +0300
> Subject: [PATCH] emacs: Disable grafts when dry-run is enabled.
>
> * emacs/guix-main.scm (process-package-actions): Set grafting according
> to 'dry-run?'.
> * guix/scripts.scm (build-package): Likewise.

[...]

>  (define-module (guix scripts)
> +  #:use-module (guix grafts)
>    #:use-module (guix utils)
>    #:use-module (guix ui)
>    #:use-module (guix store)
> @@ -106,6 +107,7 @@ true."
>    "Build PACKAGE using BUILD-OPTIONS acceptable by 'set-build-options'.
>  Show what and how will/would be built."
>    (mbegin %store-monad
> +    (set-grafting (not dry-run?))
>      (apply set-build-options*
>             #:use-substitutes? use-substitutes?
>             (strip-keyword-arguments '(#:dry-run?) build-options))

Here it might be best to do something like this:

  (mlet %store-monad ((grafting? ((lift0 %graft? %store-monad))))
    (set-grafting (and (not dry-run?) grafting?))
    …)

This would make sure we don’t enable grafting if it turned out to be
disabled.

WDYT?

Ludo’.