org.freedesktop.DBus.Properties.GetAll 返回“g-dbus-error-quark: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: 没有这样的接口”“”

Question

I am writing a python script for search.deb packages on USB-Flash and faced the following problem: when calling the org method.freedesktop.DBus.Properties.GetAll("") I get "g-dbus-error-quark: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: No such interface “”"

Replacing the method argument with any of the existing interfaces gives the same result, only the name of the entered interface is written instead of "". Passing the device as an argument also doesn't help.

When running the same method via d-feet, the result is the same.

A fragment of the script code:

_bus = dbus.SystemBus()
_proxy = _bus.get_object('org.freedesktop.UDisks2','/org/freedesktop/UDisks2')
_iface = dbus.Interface(_proxy, 'org.freedesktop.DBus.ObjectManager')

for _dev in _iface.GetManagedObjects():
    _dev_obj = _bus.get_object('org.freedesktop.UDisks2', _dev)
    _dev_prop = dbus.Interface(_dev_obj, 'org.freedesktop.DBus.Properties')
    print(_dev_prop.GetAll('org.freedesktop.DBus.Properties'))

Screenshot from d-feet

What could be the matter?

Answer 1

Calling gdbus introspect --system --dest org.freedesktop.UDisks2 --object-path /org/freedesktop/UDisks2 results:

node /org/freedesktop/UDisks2 {
  interface org.freedesktop.DBus.Properties {
    methods:
      Get(in  s interface_name,
          in  s property_name,
          out v value);
      GetAll(in  s interface_name,
             out a{sv} properties);
      Set(in  s interface_name,
          in  s property_name,
          in  v value);
    signals:
      PropertiesChanged(s interface_name,
                        a{sv} changed_properties,
                        as invalidated_properties);
    properties:
  };
  interface org.freedesktop.DBus.Introspectable {
    methods:
      Introspect(out s xml_data);
    signals:
    properties:
  };
  interface org.freedesktop.DBus.Peer {
    methods:
      Ping();
      GetMachineId(out s machine_uuid);
    signals:
    properties:
  };
  interface org.freedesktop.DBus.ObjectManager {
    methods:
      GetManagedObjects(out a{oa{sa{sv}}} object_paths_interfaces_and_properties);
    signals:
      InterfacesAdded(o object_path,
                      a{sa{sv}} interfaces_and_properties);
      InterfacesRemoved(o object_path,
                        as interfaces);
    properties:
  };
  node Manager {
  };
  node drives {
  };
  node block_devices {
  };
};

According to D-Bus Specification :

An empty string may be provided for the interface name; in this case, if there are multiple properties on an object with the same name, the results are undefined (picking one by according to an arbitrary deterministic rule, or returning an error, are the reasonable possibilities).

My guess you are facing one of these undefined results .

But my question is, why do you need to call this method? according to the introspection result the requested path doesn't contain any properties!