[PATCH xserver 7/7] meson: An empty array is not a dependency object

[Eric Anholt]

Jon Turney <jon.turney at dronecode.org.uk> writes:

> Using the meson idiom of initializing a variaible to an empty array to
> represent a null value does not work well for a variable expected to hold a
> dependency object, as trying to apply found() to it will fail (currently).
>
> I think this can be demonstrated by configuing with Dglamor=no, then gbm_dep
> is set to [] in meson.build, and then tested with found() in
> include/meson.build.
>
> Use dependency('') to create an empty dependency.
>
> Future work: In the autotools build GBM is required if build_xorg &
> build_glamor.  I suspect that it was also required for build_xwayland &
> build_glamor, but that was never checked.  That test seems to have gone
> missing in meson.build, the required:false when checking for gbm should
> possibly be dropped?
>
> Signed-off-by: Jon Turney <jon.turney at dronecode.org.uk>
> ---
>  meson.build | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/meson.build b/meson.build
> index d3e0685bd..bc2323641 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -177,7 +177,7 @@ endif
>  
>  build_dbus = build_hal or build_systemd_logind
>  
> -udev_dep = []
> +udev_dep = dependency('', required:false)
>  if build_udev
>      udev_dep = dependency('libudev', version: '>= 143')
>  endif
> @@ -198,7 +198,7 @@ else
>      build_glamor = get_option('glamor') == 'yes'
>  endif

Could we just do the gbm_dep hunk and not the udev one, if the udev hunk
isn't needed?

>  
> -gbm_dep = []
> +gbm_dep = dependency('', required:false)
>  if build_glamor
>      gbm_dep = dependency('gbm', version: '>= 10.2', required: false)
>      if gbm_dep.found()

We've certainly got a cleanup of gbm_dep to do, but I'm fine with this
for now.  Meson folks agreed that this was the best workaround, though
"[].found() == false" may be available in the future.

Reviewed-by: Eric Anholt <eric at anholt.net>
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