add an easy way for a state to ignore packets by creating a ReceiveTransition back to itself

tests/state_machine.py

@@ -346,6 +346,24 @@ class State(object):
         """Called with PDU received after match."""
         self.state_machine.after_receive(pdu)
 
+    def ignore(self, pdu_type, **pdu_attrs):
+        """Create a ReceiveTransition from this state to itself, if match
+        is successful the effect is to ignore the PDU.
+
+        :param criteria: PDU to match
+        """
+        if _debug: State._debug("ignore(%s) %r %r", self.doc_string, pdu_type, pdu_attrs)
+
+        # create a bundle of the match criteria
+        criteria = (pdu_type, pdu_attrs)
+        if _debug: State._debug("    - criteria: %r", criteria)
+
+        # add this to the list of transitions
+        self.receive_transitions.append(ReceiveTransition(criteria, self))
+
+        # return this state, no new state is created
+        return self
+
     def unexpected_receive(self, pdu):
         """Called with PDU that did not match.  Unless this is trapped by the
         state, the default behaviour is to fail."""