fix(swarm-derive): add bounds to OutEvent on generic fields

[jxs]

Description

This PR isolates the bugfix for the NetworkBehaviour derive implementation for structures with generic fields. When out_event was not provided, the generated enum was missing the NetworkBehaviour impl constraint for the generic variants whilst using the generics for <Generic>::OutEvent.

Meanwhile I also found that the generated poll function loops the sub behaviours and either return's when Poll::Ready or break's when Poll::Pending. This is a relict from when we still had NetworkBehaviourEventProcess which had added a branch within this loop that did not return but consume the event and continue. This trait was removed a while ago meaning this loop is no longer needed.

Notes

code generated by the ping example:

fn poll(
        &mut self,
        cx: &mut std::task::Context,
        poll_params: &mut impl ::libp2p::swarm::derive_prelude::PollParameters,
    ) -> std::task::Poll<
        ::libp2p::swarm::derive_prelude::NetworkBehaviourAction<
            Self::OutEvent,
            Self::ConnectionHandler,
        >,
    > {
        use ::libp2p::swarm::derive_prelude::futures::*;
        loop {
            match ::libp2p::swarm::derive_prelude::NetworkBehaviour::poll(
                &mut self.keep_alive,
                cx,
                poll_params,
            ) {
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::GenerateEvent(
                        event,
                    ),
                ) => {
                    return std::task::Poll::Ready(
                        ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::GenerateEvent(
                            BehaviourEvent::KeepAlive(event),
                        ),
                    );
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::Dial {
                        opts,
                        handler: provided_handler,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::Dial {
                        opts,
                        handler: ::libp2p::swarm::derive_prelude::IntoConnectionHandler::select(
                            provided_handler,
                            self.ping.new_handler(),
                        ),
                    });
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::NotifyHandler {
                        peer_id,
                        handler,
                        event,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::NotifyHandler {
                        peer_id,
                        handler,
                        event: ::libp2p::swarm::derive_prelude::Either::Left(event),
                    });
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::ReportObservedAddr {
                        address,
                        score,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::ReportObservedAddr {
                        address,
                        score,
                    });
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::CloseConnection {
                        peer_id,
                        connection,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::CloseConnection {
                        peer_id,
                        connection,
                    });
                }
                std::task::Poll::Pending => break,
            }
        }
        loop {
            match ::libp2p::swarm::derive_prelude::NetworkBehaviour::poll(
                &mut self.ping,
                cx,
                poll_params,
            ) {
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::GenerateEvent(
                        event,
                    ),
                ) => {
                    return std::task::Poll::Ready(
                        ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::GenerateEvent(
                            BehaviourEvent::Ping(event),
                        ),
                    );
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::Dial {
                        opts,
                        handler: provided_handler,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::Dial {
                        opts,
                        handler: ::libp2p::swarm::derive_prelude::IntoConnectionHandler::select(
                            self.keep_alive.new_handler(),
                            provided_handler,
                        ),
                    });
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::NotifyHandler {
                        peer_id,
                        handler,
                        event,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::NotifyHandler {
                        peer_id,
                        handler,
                        event: ::libp2p::swarm::derive_prelude::Either::Right(event),
                    });
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::ReportObservedAddr {
                        address,
                        score,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::ReportObservedAddr {
                        address,
                        score,
                    });
                }
                std::task::Poll::Ready(
                    ::libp2p::swarm::derive_prelude::NetworkBehaviourAction::CloseConnection {
                        peer_id,
                        connection,
                    },
                ) => {
                    return std::task::Poll::Ready(::libp2p::swarm::derive_prelude::NetworkBehaviourAction::CloseConnection {
                        peer_id,
                        connection,
                    });
                }
                std::task::Poll::Pending => break,
            }
        }
        std::task::Poll::Pending
    }

Links to any relevant issues

Open Questions

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• A changelog entry has been made in the appropriate crates

[thomaseizinger]

I think the loops are a historical left-over from when we had NetworkBehaviourEventProcess which would have consumed an event and then would have to poll the inner behaviour again. Well spotted!

[thomaseizinger]

👍