Re: [PATCH] modutils completion: Fix FHS assumption

[Doron Behar <doron.behar@gmail.com>]

This Patch has been previously discussed at
https://gitlab.com/zsh-org/zsh/-/merge_requests/15 but Daniel Shahaf and
I wish to get more feedback as to whether this brakes and `modutils`
related command for anyone.

Basically, the $modules_dir is set just like before, but if
`/run/booted-system/kernel-modules/lib/modules` exists, it's being used
instead of the default `/lib/modules` - the 1st directory is the
directory used on NixOS and Guix.

This patch fixes an ugly error for NixOS and Guix utils which goes like
this:


    $ modinfo <tab> _modutils:102: no such file or directory:
    /lib/modules/5.6.15/modules.alias


On Mon, Jun 01, 2020 at 08:05:19PM +0300, doron.behar@gmail.com wrote:
> From: Doron Behar <doron.behar@gmail.com>
> 
> ---
>  Completion/Linux/Command/_modutils | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Completion/Linux/Command/_modutils b/Completion/Linux/Command/_modutils
> index ff6844f41..a0ed7b210 100644
> --- a/Completion/Linux/Command/_modutils
> +++ b/Completion/Linux/Command/_modutils
> @@ -12,7 +12,18 @@ _modules_caching_policy()
>  _modutils() {
>    local curcontext="$curcontext" expl state line modules modaliases ign args ret=1
>    local -A opt_args
> -  local -r modules_dir=/lib/modules
> +  local -a possible_modules_dirs=(
> +    # NixOS & possibly Guix
> +    /run/booted-system/kernel-modules/lib/modules
> +    # Mostly every other distro
> +    /lib/modules
> +  )
> +  local modules_dir tested_modules_dir
> +  for tested_modules_dir in "${possible_modules_dirs[@]}"; do
> +    if [[ -d "$tested_modules_dir" ]]; then
> +      modules_dir="$tested_modules_dir"
> +    fi
> +  done
>  
>    local update_policy
>    zstyle -s ":completion:*:*:$service:*" cache-policy update_policy
> @@ -108,6 +119,9 @@ _modutils() {
>      all-modules)
>        local kver=${opt_args[(i)(-S|-k|--set-version)]:-$(uname -r)}
>  
> +      if [[ -z "$modules_dir" ]]; then
> +        return
> +      fi

I _think_ this addition will also gracefully catch the edge case of a
modules directory not found at all.

>        if _cache_invalid modules-$kver || ! _retrieve_cache modules-$kver;
>        then
>  	modules=( $modules_dir/$kver/(*~(source|build))/**/*.(o|ko|ko.gz|ko.xz)(.:t:r:r) )
> -- 
> 2.26.2
>