Re: PATCH: edit-command-line: disable `monitor' option locally

[Frank Terbeck <ft@bewatermyfriend.org>]

Bart Schaefer wrote:
> On Mar 16,  9:16pm, Frank Terbeck wrote:
> } Subject: PATCH: edit-command-line: disable `monitor' option locally
> }
> } I was just told, that suspending an editor while using
> } `edit-command-line' will cause the command line to be lost, yielding
> } this:
> } 
> } edit-command-line:zle:17: widgets can only be called when ZLE is active
> } 
> } Which makes sense.
>
> Hmm.  I don't have this problem.

Hm. I had trouble reproducing this, too. So, I asked the guys for
precise instructions and they came up with something I could reproduce
as well.

> If I suspend from edit-command-line I get brought back to the prompt
> and the previous input is all still there.  I can resume the editor
> with "fg" (at which point vim gives me an error about the file no
> longer existing); if I write, exit, and then repeat the
> edit-command-line keystroke, I'm back in the editor looking at the
> stuff I wrote out a minute before, and if I now exit again that stuff
> is loaded onto the command line.

Here is how to get the error:

a) Start a new shell. The error seems to only appear the first time the
   `edit-command-line' widget is called.
b) Enter something into the command line buffer.
c) Strike your `edit-command-line' shortcut.
d) "C-z" to suspend.
e) Run another command while being suspended.
f) "fg" to get the editor back.
g) Exit the editor.

This leads to the error I mentioned.

Later attempts don't yield the error, but the command line buffer's
content is *gone* every time. Which to me is quite a grave problem, as
this may lead to rather huge multi-line commands to be gone.

> } So, in order to shield users from accidential dataloss, this patch
> } unsets the `monitor' option temporarily. That does the trick for me and
> } I don't think there is anything this would break.
>
> On the other hand if I put in this patch, then when I try to resume the
> backgrounded editor

Um. How do you end up with a backgrounded editor with this patch?
Shouldn't it be impossible to background the editor if `monitor' is
unset? I can't seem to get that to happen on my linux-based laptop.

> I end up in a *very* strange state where the shell is not responding
> to anything, and I have to go off to another window and kill -CONT the
> editor before I can proceed.  In that case vim dies almost immediately
> with "Vim: Error reading input, exiting..."
>  
> } If I'm missing something, yell.
>
> I think perhaps this behaves very differently in different contexts.
> Restartable system calls may be the difference, I don't know which
> platform has the trouble that you described.

This happens for me on various linux systems with different kernel
versions. I may be able to try OpenBSD later today, unless someone beats
me to it.


In any case, I think the widget should protect the user from losing the
command line. And disallowing the editor from backgrounding should do
that (and in fact does for me).

Regards, Frank

-- 
In protocol design, perfection has been reached not when there is
nothing left to add, but when there is nothing left to take away.
                                                  -- RFC 1925