Subject: Re: bug: "C-x z" ("repeat") no longer works correctly with M-x

From: Stefan Monnier <[email-masked]>
Date: Sat, 02 Jun 2012 15:21:51 -0400

> The problem is that the old execute-extended-command sets the
> real_this_command internal variable, which causes the Emacs command loop
> to record the command that was actually executed into real-last-command
> and last-repeatable-command.

Indeed.

> In other words, it's not just the fact that `C-x z' doesn't work
> properly.  Moving execute-extended-command to Lisp produces a
> backward-incompatible change in the values of the real-last-command and
> last-repeatable-command variables for M-x.  I suspect this may break
> things other than `C-x z'.  I guess we could fix this by exposing
> real_this_command to Lisp too, but that kinda defeats the point of that
> variable...

I don't see why this would defeat anything.  Clearly,
execute-extended-command demonstrates that there can be very good
reasons to change real-this-command.
I installed a change that does just that.

> Is there a strong rationale for moving execute-extended-command to Lisp,
> other than the general principle that we want as much functionality
> implemented Lisp as possible?

To me, an important part of moving code to Elisp is to make sure that it
*can* be implemented in Elisp (i.e. that some third-party package can
provide a new implementation of that functionality).

        Stefan