Package: debian-policy Severity: wishlist X-Debbugs-Cc: debian-de...@lists.debian.org
I propose two new virtual packages: dbus-session-bus: anything providing the D-Bus well-known session bus for user login sessions dbus-default-session-bus: Debian's preferred implementation of dbus-session-bus Currently, many packages that require a D-Bus session bus express that dependency by depending on dbus-x11. Many more packages rely on a session bus without an explicit dependency. I would like to deprecate dbus-x11 (which provides a D-Bus session bus per X11 session to that X11 session) in favour of dbus-user-session (which provides a D-Bus session bus per uid, shared by all concurrent PAM sessions), while keeping dbus-x11 supported as a non-preferred implementation. >From discussion in the related MBF plan <https://lists.debian.org/debian-devel/2016/07/msg00484.html>, I am led to believe that the preferred way to do this is with two virtual packages, analogous to mail-transport-agent and default-mta. dbus-session bus would be provided by dbus-x11, dbus-user-session, and possibly something kdbus-related in future. The intended semantics are: programs in at least graphical login sessions can rely on seeing the $DBUS_SESSION_BUS_ADDRESS environment variable, the $XDG_RUNTIME_DIR/bus Unix socket, or some other way to discover a session bus that is supported by all the major D-Bus client libraries. dbus-default-session-bus would be provided by exactly one package per suite that is the preferred implementation, currently dbus-user-session. Programs and desktop environments that require a D-Bus session bus and cannot work without one should generally declare: Depends: dbus-default-session-bus | dbus-session-bus Programs with weaker dependencies can use a Recommends or a Suggests. Other options ============= If this is not a best-practice use of virtual packages, the other options that I am aware of are: * Add a real (non-virtual) empty package dbus-session-bus built by src:dbus, with Depends: dbus-user-session | dbus-x11 (initially). Other packages depend on dbus-session-bus. (Pro: simpler dependency graph. Con: requires NEW queue.) * Add a virtual package dbus-session-bus, and a real (non-virtual) package dbus-default-session-bus built by src:dbus. (Pro: avoids ambiguity if apt is configured to see more than one suite. Con: requires NEW queue.) * Give packages a direct Depends: dbus-user-session | dbus-x11, and do another MBF if we decide post-stretch that we should actually be preferring a third implementation, kdbus-session-bus or something. (Pro: no proliferation of package names. Con: possible MBF in future.) * MBF asking applications to stop depending on dbus-x11, and just assume that any reasonable desktop environment will pull in dbus-user-session | dbus-x11 anyway, in the same way that applications are not expected to depend on an X11 server. (Pro: simplest possible dependency graph. Con: undeclared dependency.) Regards, S
