Net::DBus and qdbus disagreement

[Daniel P. Berrange]

On Wed, Jan 04, 2012 at 12:10:05PM +0000, Simon McVittie wrote:
> On Sun, 18 Dec 2011 at 21:29:42 +0000, Daniel P. Berrange wrote:
> > Ok, so this is showing that there are 3 methods exported in the same
> > interface, all with the same name.  I did not realize that this is
> > allowed by DBus.
> 
> D-Bus is both a message passing system, and an object model built on that
> message passing system. I've been trying to make the layering clearer in the
> spec, but am still rather held up by lack of reviews for my queue of pending
> patches - reviews on Bugzilla welcome, even from non-committers!
> 
> Any call is allowed by the message passing system, which operates at a
> considerably lower level than the object model used by most bindings.

Yes, my bad terminology in the quoted text above. What I meant to say
was that I did not realize this allowed by /the DBus Introspection XML/
format.

> It's ambiguous whether the object model is meant to allow overloading (two
> methods with the same name and different "in" arguments) or not. In my opinion,
> there is a "portable subset" of D-Bus that interface designers
> should use, and that portable subset doesn't include overloading.

That sounds reasonable. None the less, I am aiming to make it possible
to use Net::DBus as a client, in two methods with same name scenario.

> 
> > The Net::DBus code is assuming that method names
> > are unique within the scope of a single interface, so it is only
> > able to show you a single method. 
> 
> Many other bindings, particularly those that try to "hide" D-Bus signatures
> (at least dbus-glib and dbus-python), have the same problem. I believe the
> only "signature-hiding" binding that supports method overloading like this
> is Qt.
> 
> GDBus avoids this by having the signature appear explicitly in every method
> call. I think dbus-python might also cope if you use an explicit signature.

Interesting, I'll take a look at the python binding for inspiration in how
to solve it most effectively for Perl.

Regards,
Daniel
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