fix(yggctl): prefer system bus when run as root

[subpop]

yggctl will attempt to connect to the session bus only if
DBUS_SESSION_BUS_ADDRESS is non-empty and the effective UID of the
process is greater than zero. This results in root invocations of yggctl
preferring the system bus over the session bus.

Fixes: #142

[jirihnidek]

I think that refactoring is quite good. I would like to know why the environment variable DBUS_SESSION_BUS_ADDRESS was not empty in your case. I think that it is not normal situation. I was not able to reproduce this. See my comments in #142 Thus I'm not sure if os.Geteuid() > 0 is necessary.

[jirihnidek]

I have some request and suggestion.

[jirihnidek]

This line should be changed to:

if os.Getenv("DBUS_SESSION_BUS_ADDRESS") != "" && os.Geteuid() > 0 {

otherwise this function will return incorrect error messages for the case you are trying to solve.

[jirihnidek]

But I have better proposal to avoid checking conditions twice. What about this:

func connectBus() (*dbus.Conn, error) {
	var connect func(...dbus.ConnOption) (*dbus.Conn, error)
	var conn *dbus.Conn
	var err error
	var errMsg string
	if os.Getenv("DBUS_SESSION_BUS_ADDRESS") != "" && os.Geteuid() > 0 {
		connect = dbus.ConnectSessionBus
		errMsg = "cannot connect to session bus (" + os.Getenv("DBUS_SESSION_BUS_ADDRESS") + "): %w"
	} else {
		connect = dbus.ConnectSystemBus
		errMsg = "cannot connect to system bus: %w"
	}
	conn, err = connect()
	if err != nil {
		return nil, fmt.Errorf(errMsg, err)
	}
	return conn, nil
}

[subpop]

Nice. Yea. This should work. And I completely forgot my Geteuid check when I rewrote the function. 🤦

[jirihnidek]

LGTM, Thanks for updates 👍