Re: [BUG] Crash when accessing WIDGETSTYLE from SIGINT trap

[Roman Perepelitsa <roman.perepelitsa@xxxxxxxxx>]

On Mon, Nov 11, 2019 at 3:58 PM Peter Stephenson
<p.stephenson@xxxxxxxxxxx> wrote:
>
> On Mon, 2019-11-11 at 15:38 +0100, Roman Perepelitsa wrote:
> > Crash at zle_params.c:436 due to bindk being null:
> >
> >     Widget widget = bindk->widget;
>
> Looks to me like returning the empty string in that case would be fine?

I don't know. I haven't sent a patch because I'm not sure whether the
fix should be right there in get_widgetstyle or somewhere earlier so
that bindk is not null to begin with.

I should've explained what I'm trying to do. I want to use a long
prompt for the current command line and a short prompt for complete
commands. Sort of like transient_rprompt option but instead of hiding
just right prompt I want to hide most of left prompt too. Here's a
short demo: https://raw.githubusercontent.com/romkatv/powerlevel10k-media/master/transient-prompt.gif.

Here's how I'm doing it:

- Set long prompt in precmd.
- Set short prompt in zle-line-finish and on SIGINT.

The code:

    set-long-prompt() { PROMPT='%~%# ' }
    precmd_functions=(set-long-prompt)

    set-short-prompt() {
      if [[ $PROMPT != '%# ' ]]; then
        PROMPT='%# '
        zle .reset-prompt
      fi
    }

    zle-line-finish() { set-short-prompt }
    zle -N zle-line-finish

    trap 'set-short-prompt; return 130' INT

One issue with this code is that after hitting Ctrl-C, set-long-prompt
doesn't get called, so I end up with a short current prompt. I don't
know why this happens but apparently I can work around this by adding
another precmd hook before set-current-prompt. This extra hook won't
be called after Ctrl-C but set-current-prompt will.

    do-nothing() {}
    precmd_functions=(do-nothing set-current-prompt)

Unfortunately, there are a few other cases where hitting Ctrl-C will
result in the current prompt ending up short rather than long. For
example, if I this Ctrl-C after typing this:

    autoload -U compinit
    compinit
    zstyle ':completion:*' menu select
    grep -i<TAB>

If I didn't trap SIGINT, Ctrl-C would simply close the completion menu
here without reexpanding prompt. But now prompt will become short. To
deal with this issue I tried changing my trap so that it doesn't reset
prompt if SIGINT arrives during completions:

    trap '[[ $WIDGETSTYLE == .expand-or-complete ]] || set-complete-prompt
          return 130' INT

Unfortunately it crashes zsh as I've described in the original email.
It also doesn't really solve the problem. If I press Ctrl-S to trigger
fwd-i-search and then hit Ctrl-C, I'll end up with short prompt, too.
fwd-i-search is not a completion widget, so the condition in my trap
doesn't help.

What I really want is to follow the same logic as transient_rprompt
but instead of hiding right prompt I want to change left prompt. Any
hints on how I should do this? I feel like I'm digging in the wrong
direction.

Roman.