"Recent" changes to compilation-mode?

[David Abrahams]

Sometime in the past year or so compilation-mode started acting very
strangely for me with a CVS-built emacs.  First, if I use next-error
while compilation is still going on, I will often, after a moment or
two, see the point jump unpredictably in the file it takes me to.

Second, next-error used to cause the error in question to scroll to
the top of the *compilation* buffer's window, which made it very easy
to see what was going on.  Now emacs just moves that buffer's point
without scrolling.  Since the active point ends up in the source
file's buffer where the error is, all I see change in the
*compilation* buffer is that an unfilled rectangle with super-thin
borders moves.  It's extremely hard to see; if the window isn't going
to scroll, IMO something else needs to be done (e.g. with
highlighting) to emphasize the error in question.

Finally, many of my carefully-constructed error regexps seem no longer
to be recognized.  I had been doing:

  (require 'compile)

  (setq compilation-error-regexp-alist
        (append
         '(...regexps...)
         compilation-error-regexp-alist))

   (if (fboundp 'compilation-file-regexp-alist) ; in case of XEmacs,
                                                ; which doesn't support
                                                ; 'compilation-file-regexp-alist
    (setq compilation-file-regexp-alist
      (append
       '(... regexps ...)
           compilation-file-regexp-alist)))

I note that now there appears to be a two-layer scheme with
compilation-error-regexp-alist-alist that renders my old settings
invalid.  I can adjust what I'm doing, but discovering what to do was
a struggle.  Is there a way to provide a better transition experience
for people who upgrade?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com