Re: Proposed mass bug filing: use and misuse of dbus-launch (dbus-x11)
On Wed, 27 Jul 2016 at 18:02:32 +0200, Laurent Bigonville wrote:
> Is that really up-to the individual application to declare a dependency
> against dbus-user-session | dbus-x11 ?
At the moment: yes. A dependency on dbus-x11 (in jessie) or on
dbus-user-session | dbus-x11 (now) can be used to signify "this
application or library is useless without a working session bus".
Apps that rely on Telepathy, Tracker or the Evolution servers are
good examples of a legitimate dependency on the session bus.
Depending on dbus is not enough: that only guarantees working D-Bus
binaries (so you have all the right bits to get a session bus, but some
assembly is required) and a working system bus.
The only other ways I can think of right now to express that requirement
are:
* introduce a metapackage "dbus-session" with that dependency, and
ask these apps to depend on it, or on dbus-session | dbus-x11 to be
nice to backports;
* give up on it entirely, and consider a working D-Bus session to be
an essential/assumed part of desktop environments (like a working X11
server is), with a policy that only desktop environment tasks need
to declare the dependency, and random apps can just assume it
(Arguably we already have this situation; I'm sure there are lots of
apps that don't declare this dependency but are unusable without
D-Bus because they rely on GApplication, fd.o Notifications or some
other piece of infrastructure that relies on the session bus.)
> If the package name is changing or if we are dropping dbus-x11 in the future
> that would require modifying again quite some packages.
I currently count 55 direct Depends and 17 Recommends on dbus-x11,
to give you an idea of the number of packages involved.
The last time this changed was the introduction of dbus-x11 in 2007;
twice in a decade isn't bad. I don't think it's necessarily going to
change again any time soon (unless we do a transition to
dbus-x11 | dbus-user-session and then another to
dbus-user-session | dbus-x11, which is why I'd prefer not to do that
two-stage approach).
If we drop dbus-x11 at some point in the future, or even fold
dbus-user-session into dbus, those packages won't need modification:
as long as either dbus-user-session still exists, or dbus Provides it,
those packages are still Policy-compliant (I believe we only require one
branch of an "or"-group to be available in main). In practice I don't
think this is going to happen any time soon, for the reasons mentioned
under "Why should dbus-user-session be optional?" in my original mail.
> Shouldn't this
> dependency only be declared at some other level (libdbus, GDBus,...)?
I think this would have to be a new dbus-session metapackage, unless
I'm missing something. dbus is the wrong place, and so are all the
obvious libraries.
dbus Suggests dbus-user-session | dbus-x11 already. Anything stronger than
Suggests seems inappropriate because it would be a circular dependency
(dbus-user-session and dbus-x11 both need dbus, for dbus-daemon).
libdbus-1-3 shouldn't depend on a session bus, because you might only
be using it to access the system bus; conversely, you might be using
a different implementation like GDBus or sd-bus or dbus-java and you'd
still be missing the dependency. It would also be a circular dependency,
via dbus (dbus Depends libdbus-1-3 Depends (dbus-user-session|dbus-x11)
Depends dbus).
libglib2.0-0 (which contains libgio-2.0.so.0, which contains GDBus) shouldn't
depend on a session bus for reasons analogous to libdbus-1-3's, and also your
uses of GLib might not involve D-Bus at all (perhaps it's just installed
for irssi's benefit).
libsystemd0 (which contains sd-bus) definitely must not depend on dbus,
because dbus depends on it (circular dependencies again), and because it's
transitively Essential (via util-linux).
S
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