This sounds perfect to me.

On Thu, Aug 10, 2017 at 8:50 PM, <npostavs@users.sourceforge.net> wrote:

> Gary Oberbrunner <garyo@genarts.com> writes:
>
> > If a user (such as myself) has an implementation of this function in his
> .emacs today, like so:
> >
> > (defun process-error-filename (filename)
> >   ;;; do stuff with filename
> >   filename)
> > (setq compilation-parse-errors-filename-function
> 'process-error-filename)
> >
> > and we add a new argument that gets passed to that function, it'll throw
> an error. *Users* will have to add
> >   &optional spec-dir
> > to their implementations of it to avoid the error.
>
> We could do something like
>
>     (condition-case err
>         (funcall compilation-parse-errors-filename-function filename
> spec-dir)
>       (wrong-number-of-arguments
>        ;; Try again with single arg for backwards compatibility.
>        (funcall compilation-parse-errors-filename-function filename)))
>



-- 
Gary Oberbrunner *--* CTO *--* Boris FX