bug#21054: 25.0.50; Can't edit SES documents: Not at cell

[Óscar Fuentes]

Eli Zaretskii <eliz@gnu.org> writes:

> The changeset you identified as the one to blame is huge, even if we
> look only at changes in ses.el.  Would it be possible for you to try
> to locate the code that specifically caused this misbehavior?

I tried for a bit and located the specific call chain that throws the
error, but not why it is thrown.

> Or maybe you already know that?
>
> Armed with that knowledge, we could see how to fix this annoying
> problem, which IMO should block Emacs 25.1 release, unless we fix it
> soon.

This bug renders ses.el unusable, so it is a release blocker indeed. The
right approach would be to revert the omnibus change that introduced the
problem as soon as it was reported, but that was rejected by Stephan and
now possibly other changes rely on the parts covered by the problematic
one.

Anyways, I have the intention of delving into this issue as soon as
possible (before the year's end) and it is very likely that I find a
"fix", but I have no enough knowledge about ses.el to guarantee its
soundness, so if anyone has a proper understanding of what's going on,
please go ahead and fix it. (The fact that Stephan didn't fix the bug
himself is an indication that it is far from being a trivial one.)