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From: Zefram <zefram@tao.co.uk>
Message-Id: <199806091801.TAA04656@taos.demon.co.uk>
Subject: Re: User-defined zle widgets and built-in widget failure
To: schaefer@brasslantern.com (Bart Schaefer)
Date: Tue, 9 Jun 1998 19:01:58 +0100 (BST)
Cc: zsh-workers@math.gatech.edu
In-Reply-To: <980609100902.ZM6152@candle.brasslantern.com> from "Bart Schaefer" at Jun 9, 98 10:09:02 am
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Bart Schaefer wrote:
>I'd like to write a widget that modifies BUFFER, calls a built-in widget,
>and then if that built-in widget fails, restores the previous BUFFER and
>CURSOR.
>
>Unfortunately, failure of "zle whatever" isn't detectable; "zle" always
>sets $? to zero.

Failure internally is recorded by the feep flag.  If that is set at
the end of the main loop, a beep is emitted and the flag reset.  All we
need to do is make that flag visible to widgets.  Like a lot of other
ZLE things, this is one of the things I had a fairly concrete plan for
when my spare time suddenly disappeared last year.

The mechanism I planned is that each thingy will include a single-bit
flag, which can be tested and modified using the zle builtin.  Then all
you do to test for error is "if zle -F feep; ...", where the value of
"F" has yet to be determined.  Other thingies would have flags attached
similarly.  Or a more general possibility would be thingy array variables
accessible via thingy names, or possibly by more magic parameter names
(though I'd want to do a proper namespace separation, e.g., ${zle.feep}).

That reminds me, more generally I'd like to move the zsh-specific
parameter names to completely separate names that can't conflict
with POSIX parameter names.  If we have ${zsh.module_path} instead of
$module_path, then this can be available regardless of the name used to
invoke zsh.  What do people think?

-zefram