tahoe-lafs/src/allmydata/util/rrefutil.py

from foolscap.api import Violation, RemoteException, DeadReferenceError

def add_version_to_remote_reference(rref, default):
    """I try to add a .version attribute to the given RemoteReference. I call
    the remote get_version() method to learn its version. I'll add the
    default value if the remote side doesn't appear to have a get_version()
    method."""
    d = rref.callRemote("get_version")
    def _got_version(version):
        rref.version = version
        return rref
    def _no_get_version(f):
        f.trap(Violation, RemoteException)
        rref.version = default
        return rref
    d.addCallbacks(_got_version, _no_get_version)
    return d

def trap_and_discard(f, *errorTypes):
    f.trap(*errorTypes)
    pass

def trap_deadref(f):
    f.trap(DeadReferenceError)
    pass