bug#60830: 30.0.50; The *Compilation* buffer does not recognize Lua errors

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> Even if we were to pull off the 'low priority background' part,

I'm counting on you for this part.

> it seems difficult to balance such a mechanism so that it's never
> annoying yet relevant when it needs to be.

I suspect the "never annoying" is not too hard to get: those regexps are
currently matched so if they were annoying we'd know about it.

So just: if there's a match highlight it somehow and put a `help-echo`
(and maybe also a `mouse-2` binding) that tells how to activate it.

> In any case we would benefit from a better way to select rules.

Agreed.

> One problem is that packages (and users) go wild modifying both CERA
> and CERAA.  Here is a patch that I'm not satisfied with but tries to
> make CERA easier to customise interactively.

Looks OK to me, tho it will complain to the user if they have it set to
a shape that doesn't fit your mold :-(

> Its main limitation is assuming that explicit rule specs precede symbols
> that refer to CERAA, which makes some kind of sense (new rules are added for
> a reason so they should take priority) but may not correspond to
> reality.  Not sure what to do about that, but at least it's a start.

I wonder how common it is for people to set it "manually" in their
init file.  It seems more common to set it in ELisp packages.


        Stefan