Considering this bug (or a very similar variant) was reported before and
the issue just died a silent death, I think it's a good idea to create a
Github repo for tracking zsh issues. Github issue tracker is a lot better
than mailing lists, as things have a dichotomy of being  open/closed, and
can be labeled. It is harder for issues to die a silent death there. It is
also easier to contribute to that, and easier to unsubscribe (I don't think
one can unsubscribe from a mailing list post one participated in, as people
(wisely) use reply-all.).

On Wed, May 13, 2020 at 10:59 AM Stephane Chazelas <stephane@chazelas.org>
wrote:

> 2020-05-12 10:38:38 -0700, Bart Schaefer:
> > On Tue, May 12, 2020 at 12:03 AM Rudi C <rudiwillalwaysloveyou@gmail.com>
> wrote:
> > >
> > > mdoc-test () {
> > >
> > >     sleep 0 | sleep 0
> > >     cat}
> > >
> > > echo start |VISUAL=vim command vipe|mdoc-test
> > >
> > > # zsh: suspended (tty output)
> >
> > Putting an interactive command in the middle of a pipeline is
> > generally not going to work.  Vim in particular is pretty aggressive
> > about trying to grab a terminal, which will result in processes
> > getting SIGTT* because they don't have foreground control of the
> > terminal they're trying to use.
> [...]
>
> The thing is vim *should* be in the foreground, all the
> processes started in pipeline should be in the same process
> group which should be in foreground (so it gets
> SIGINT/SIGQUIT/SIGTSTP upon ^C/^\/^Z, so it can read the
> terminal, etc) but under some circumstances, zsh fails to put
> some processes in that group, which is a bug.
>
> $ </proc/self/stat awk '{print $5, $8}' >&2
> 127235 127235
> $ </proc/self/stat awk '{print $5, $8; system("exec sleep 1")}'  >&2 | ps
> -o pid,pgid,comm
> 131569 131569
>     PID    PGID COMMAND
>  124948  124948 zsh
>  131569  131569 awk
>  131570  131569 ps
>  131571  131569 sleep
> $ </proc/self/stat awk '{print $5, $8}' >&2 | { :; }
> 127410 127410
> $ </proc/self/stat awk '{print $5, $8}' >&2 | { : | :; }
> 127496 124948
>
> In that latter case, awk is in a different process group
> (127496) from the terminal foreground process group (124948
> which here is the process group of the main shell process!).
>
> --
> Stephane
>