swarm/: Provide additional default impls on NetworkBehaviour (#2150)

Not all implementations of `NetworkBehaviour` need all callbacks.
We've have been adding new callbacks with default implementations
for a while now. There is no reason the initial ones cannot also
be defaulted, thus making it easier create new implementations.

Co-authored-by: Max Inden <mail@max-inden.de>

swarm/src/behaviour.rs

@@ -80,7 +80,9 @@ pub trait NetworkBehaviour: Send + 'static {
     /// The addresses will be tried in the order returned by this function, which means that they
     /// should be ordered by decreasing likelihood of reachability. In other words, the first
     /// address should be the most likely to be reachable.
-    fn addresses_of_peer(&mut self, peer_id: &PeerId) -> Vec<Multiaddr>;
+    fn addresses_of_peer(&mut self, _: &PeerId) -> Vec<Multiaddr> {
+        vec![]
+    }
 
     /// Indicate to the behaviour that we connected to the node with the given peer id.
     ///
@@ -88,7 +90,7 @@ pub trait NetworkBehaviour: Send + 'static {
     ///
     /// This method is only called when the first connection to the peer is established, preceded by
     /// [`inject_connection_established`](NetworkBehaviour::inject_connection_established).
-    fn inject_connected(&mut self, peer_id: &PeerId);
+    fn inject_connected(&mut self, _: &PeerId) { }
 
     /// Indicates to the behaviour that we disconnected from the node with the given peer id.
     ///
@@ -97,7 +99,7 @@ pub trait NetworkBehaviour: Send + 'static {
     ///
     /// This method is only called when the last established connection to the peer is closed,
     /// preceded by [`inject_connection_closed`](NetworkBehaviour::inject_connection_closed).
-    fn inject_disconnected(&mut self, peer_id: &PeerId);
+    fn inject_disconnected(&mut self, _: &PeerId) { }
 
     /// Informs the behaviour about a newly established connection to a peer.
     fn inject_connection_established(&mut self, _: &PeerId, _: &ConnectionId, _: &ConnectedPoint)

swarm/src/lib.rs

@@ -605,7 +605,7 @@ where TBehaviour: NetworkBehaviour<ProtocolsHandler = THandler>,
                     }
                     this.behaviour.inject_new_listen_addr(listener_id, &listen_addr);
                     return Poll::Ready(SwarmEvent::NewListenAddr {
-                        listener_id, 
+                        listener_id,
                         address: listen_addr
                     });
                 }
@@ -1156,21 +1156,15 @@ impl NetworkBehaviour for DummyBehaviour {
         protocols_handler::DummyProtocolsHandler::default()
     }
 
-    fn addresses_of_peer(&mut self, _: &PeerId) -> Vec<Multiaddr> {
-        Vec::new()
+    fn inject_event(
+        &mut self,
+        _: PeerId,
+        _: ConnectionId,
+        event: <Self::ProtocolsHandler as ProtocolsHandler>::OutEvent
+    ) {
+        void::unreachable(event)
     }
 
-    fn inject_connected(&mut self, _: &PeerId) {}
-
-    fn inject_connection_established(&mut self, _: &PeerId, _: &ConnectionId, _: &ConnectedPoint) {}
-
-    fn inject_disconnected(&mut self, _: &PeerId) {}
-
-    fn inject_connection_closed(&mut self, _: &PeerId, _: &ConnectionId, _: &ConnectedPoint) {}
-
-    fn inject_event(&mut self, _: PeerId, _: ConnectionId,
-        _: <Self::ProtocolsHandler as ProtocolsHandler>::OutEvent) {}
-
     fn poll(&mut self, _: &mut Context<'_>, _: &mut impl PollParameters) ->
         Poll<NetworkBehaviourAction<<Self::ProtocolsHandler as
         ProtocolsHandler>::InEvent, Self::OutEvent>>

swarm/src/test.rs

@@ -82,12 +82,6 @@ where
         self.addresses.get(p).map_or(Vec::new(), |v| v.clone())
     }
 
-    fn inject_connected(&mut self, _: &PeerId) {
-    }
-
-    fn inject_disconnected(&mut self, _: &PeerId) {
-    }
-
     fn inject_event(&mut self, _: PeerId, _: ConnectionId, _: THandler::OutEvent) {
     }