Re: [PATCH] _hdiutil: run candidate-collecting loops outside the pipeline subshell

[Mikael Magnusson <mikachu@xxxxxxxxx>]

On Fri, May 29, 2026 at 7:40 PM Clay Caviness <clay@xxxxxxxxxx> wrote:
>
> The `_hdiutil_disk` and `_hdiutil_device` helpers each use the following pattern:
>
> _call_program ... hdiutil ... | while read; do
>   arr+=( ... )
> done
> # ... use $arr ...
>
> Because every component of a zsh pipeline runs in its own subshell, the array assignments  happen in the right-hand subshell and are lost by the time the subsequent `_describe` / `_wanted` call runs in the parent shell. The practical effect is that `hdiutil eject <TAB>` (which dispatches to _hdiutil_disk via the detach|eject branch) never offers any candidates, even when disk images are attached. _hdiutil_device has the same shape and the same problem for `hdiutil burn -device <TAB>`.

% echo hello | read; echo $REPLY
hello

> The fix involves feeding the loop via process substitution so the loop body runs in the parent shell, allowing the array to persist. I also made REPLY local and switched to `read -r` so backslashes in the output are not mangled.

I guess local REPLY and read -r changes make sense, but there
shouldn't be any need to use < <() syntax here. Did you also stop to
wonder why one of the sites uses a bare "hdiutil" while the other
hardcodes "/usr/bin/hdiutil"? That seems quite odd to me.

> Patch follows.
> ---
> From 2026acc22c87dc98cb985748133f7fee24ebbab5 Mon Sep 17 00:00:00 2001
> From: Clay Caviness <clay@xxxxxxxxxx>
> Date: Fri, 29 May 2026 13:33:39 -0400
> Subject: [PATCH] _hdiutil: run candidate-collecting loops outside the pipeline
>  subshell
>
> Signed-off-by: Clay Caviness <clay@xxxxxxxxxx>
> ---
>  Completion/Darwin/Command/_hdiutil | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/Completion/Darwin/Command/_hdiutil b/Completion/Darwin/Command/_hdiutil
> index 20e69cbc5..ada55bf1d 100644
> --- a/Completion/Darwin/Command/_hdiutil
> +++ b/Completion/Darwin/Command/_hdiutil
> @@ -4,22 +4,24 @@
>  #
>  _hdiutil_disk() {
>    local -a disk_desc
> -  _call_program devices hdiutil info | while read; do
> +  local REPLY
> +  while read -r REPLY; do
>      local disk_name="${${(M)REPLY[(w)1]%/dev/disk*}#/dev/}"
>      if (( #disk_name )); then
>        disk_desc+=( "$disk_name:${${(M)REPLY% *}#?}" )
>      fi
> -  done
> +  done < <(_call_program devices hdiutil info)
>    _describe -t devices disk disk_desc
>  }
>
>  _hdiutil_device() {
>    local -a device_desc
> -  _call_program devices /usr/bin/hdiutil burn -list | while read; do
> +  local REPLY
> +  while read -r REPLY; do
>      if [[ "$REPLY" == [:space:]#IOService:* ]]; then
>        device_desc+=( "$REPLY" )
>      fi
> -  done
> +  done < <(_call_program devices /usr/bin/hdiutil burn -list)
>    local expl
>    _wanted devices expl device compadd "$device_desc[@]"
>  }
> --
> 2.50.1 (Apple Git-155)
>


-- 
Mikael Magnusson