Re: [Buildroot] [PATCH 3/3 v4] docs/manual: use space-separated list for BR2_EXTERNAL

[Thomas Perale via buildroot <buildroot@buildroot.org>]

In reply of:
> Specifying a list of br2-external trees is poorly documented, and the
> only example uses a colon to separate the br2-external paths.
> 
> Adding the support for colon-separated list is the biggest mistake that
> was made when introducing support for multiple br2-external [0]. Indeed,
> both space and colon can be used to separate entries in the list, and it
> is also possible to mix the two. However, internally, the list is stored
> as a space-separated list, and all the code will split on spaces.
> 
> Besides, all other lists in Buildroot are a space-separated:
>     BR2_ROOTFS_DEVICE_TABLE
>     BR2_ROOTFS_STATIC_DEVICE_TABLE
>     BR2_TARGET_TZ_ZONELIST
>     BR2_ROOTFS_USERS_TABLES
>     BR2_ROOTFS_OVERLAY
>     BR2_ROOTFS_PRE_BUILD_SCRIPT
>     BR2_ROOTFS_POST_BUILD_SCRIPT
>     BR2_ROOTFS_POST_FAKEROOT_SCRIPT
>     BR2_ROOTFS_POST_IMAGE_SCRIPT
>     ...
> 
> So, using colons is odd.
> 
> The fact that BR2_EXTERNAL is pqssed on the command line rather than
> being a Kconfig item is not a reason enough to justify that it be
> colon-separated.
> 
> Change the documentation to only mention using a space-separated list.
> 
> Of course, for backward compatibility, we keep the code as-is to accept
> a colon-separated list, but we just do not advertise it.
> 
> Note that keeping the split on colons means that colons are not accepted
> in pathnames of br2-external trees; in practice, this is not a new
> restriction, or one that could lift as usign colons in Makefiles are
> problematic anyway.
> 
> [0] in 20cd49738781 core: add support for multiple br2-external trees
> 
> Reported-by: Fiona Klute (WIWA) <fiona.klute@gmx.de>
> Reported-by: Brandon Maier <Brandon.Maier@collins.com>
> Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
> Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
> 

Applied to 2025.02.x & 2026.02.x. Thanks

> ---
> Note: support/scripts/br2-external has shellcheck issues; this commit
> does not try to address those on purpose, as it only adds a comment.
> 
> ---
> Changes v3 -> v4:
>   - add an extract of all other list variables from [1]
>   - sumarise and include Arnout's comments from [2]
>   - fix typo
> 
> [1] https://patchwork.ozlabs.org/project/buildroot/patch/20240904205354.504964-1-yann.morin.1998@free.fr/#3375145
> [2] https://patchwork.ozlabs.org/project/buildroot/patch/20240904205354.504964-1-yann.morin.1998@free.fr/#3375416
> 
> Changes v2 -> v3:
>   - add comment in support/scripts/br2-external  (Fiona)
> 
> Changes v1 -> v2:
>   - fix typoes
> ---
>  docs/manual/customize-outside-br.adoc | 5 +++--
>  support/scripts/br2-external          | 3 +++
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/manual/customize-outside-br.adoc b/docs/manual/customize-outside-br.adoc
> index 78065489d4..8a76f3a998 100644
> --- a/docs/manual/customize-outside-br.adoc
> +++ b/docs/manual/customize-outside-br.adoc
> @@ -58,10 +58,11 @@ We can switch to another br2-external tree at any time:
>  buildroot/ $ make BR2_EXTERNAL=/where/we/have/bar xconfig
>  ----
>  
> -We can also use multiple br2-external trees:
> +We can also use multiple br2-external trees, by specifying a space-separated
> +list of paths to use:
>  
>  ----
> -buildroot/ $ make BR2_EXTERNAL=/path/to/foo:/where/we/have/bar menuconfig
> +buildroot/ $ make BR2_EXTERNAL="/path/to/foo /where/we/have/bar" menuconfig
>  ----
>  
>  Or disable the usage of any br2-external tree:
> diff --git a/support/scripts/br2-external b/support/scripts/br2-external
> index 474feaded7..641f8e18ae 100755
> --- a/support/scripts/br2-external
> +++ b/support/scripts/br2-external
> @@ -34,6 +34,9 @@ main() {
>          error "Cannot create output directory '%s'\n" "${outputdir}"
>      fi
>  
> +    # Historically, BR2_EXTERNAL could also be colon-separated, so for
> +    # backward compatibility, keep splitting on colons (in addition to
> +    # spaces).
>      # shellcheck disable=SC2068  # We do want to split on spaces
>      do_validate "${outputdir}" ${@//:/ }
>      do_mk "${outputdir}"
> -- 
> 2.52.0
> 
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