Ryan Kavanagh <rak@debian.org> writes:

> I use the cleveref package, which allows annotating \label commands with
> an optional argument. Unfortunately, this prevents both AUCTeX and
> RefTeX from detecting those labels.

Hi Ryan,

thanks for your report.  Yes, AUCTeX and RefTeX both get confused with
that optional argument.

> I am not sufficiently familiar with emacs lisp to submit a patch, but I
> think I have found some of the places that should be updated:
>
> * The variable LaTeX-auto-label-regexp-list in latex.el

latex.el provides support for vanilla LaTeX.  Additions by packages
should go into AUCTeX styles.

> * The function reftex-parse-from-file hardcodes the prefix "\\label{".
>   Perhaps this could be a customizable regexp?

RefTeX provides a customizable variable for this purpose called
`reftex-label-regexps'.

> Please add support for cleveref labels to AUCTeX and RefTeX.

This can be done within cleveref.el.  A modified version is attached.