Subject: Re: bug#22295: viper-mode undo bug introduced between Nov 10 and Nov 14

From: Stefan Monnier <[email-masked]>
Date: Wed, 01 Jun 2016 09:06:11 -0400

> different, though. With this fix, viper just disables automatic boundary
> addition and adds it's own as necessary, which seems cleaner.

I see an annoying side-effect of that change, tho:

    % emacs -Q -f viper-mode
    y 5 n                   ;; To get past viper's initial questions.
    i helo C-b k C-/

This last C-/ used to (and should) just undo the insertion of the last
"k", but instead it now completely wipes out the *scratch* buffer.

So I think that completely disabling undo boundaries is not a good idea:
while in many use-cases insertion mode is very transient, it is not so
unusual to spend more time in insertion mode (which is pretty much
"emacs mode") and to expect undo boundaries to properly inserted during
this time.

Have we been able to identify the original problem?  The old code seemed
"simple" enough that the problem was probably simple to fix (once
identified).

        Stefan