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

[Daniel Colascione <dancol@dancol.org>]

On 02/24/2014 12:37 AM, Michael Albinus wrote:
> Daniel Colascione <dancol@dancol.org> 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.