Re: Why doesn't dbus-handle-event catch all errors?

[Daniel Colascione]

On 02/24/2014 12:37 AM, Michael Albinus wrote:
> Daniel Colascione <address@hidden> writes:
>
> > > You're free to write a handler which returns any error as dbus error, if
> > > your program logic requires this.
> >
> > The only reasonable implementation of a dbus handler is one that
> > transforms lisp errors to dbus errors, so why not do that
> > automatically in dbus.el? Silently swallowing lisp errors is the less
> > common case, and if a program needs to do that, it can wrap its logic
> > in ignore-errors inside the handler.
>
> There is the special error type `dbus-error'. Any handler could catch
> lisp errors and transform them into something which is understandable to
> another process. You do not want to send "(wrong-type-argument listp
> 42)" or something like this to another process, which isn't aware of Lisp.

Why not? It's more informative than "something went wrong".

> Your handler shall include something like
>
> (defun my-dbus-method-handler (&rest args)
>    (condition-case err
>        (...)
>      (error (signal 'dbus-error (list "Something went wrong, please try it 
> again")))))

Sure. My point is that the framework should provide *something*, even if 
it's just the above, instead of silently dropping lisp errors and not 
telling callers that anything went wrong. Handlers that want to swallow 
errors can do so explicitly.