Replacing PollParameters::supported_protocols

[dariusc93]

Maybe somebody could give me a bit of a push in the right direction. Currently PollParameters::supported_protocols is deprecated with the message stating Use libp2p_swarm::SupportedProtocols in your ConnectionHandler instead., however while writing a small behaviour with a handler to handle the local protocols, it looks like the usage will only work if a single peer connects, but seems to be redundant doing this as it relies on a peer connection. Is this the intended behaviour to replace the deprecated function? Is there a better way to iterate over the current/supported protocols of the node since PollParameters::supported_protocols is deprecated? Below is the code ive quickly written to test things out.

behaviour

use std::{
    collections::VecDeque,
    task::{Context, Poll},
};

use libp2p::{
    core::Endpoint,
    swarm::{
        self, ConnectionDenied, ConnectionId, FromSwarm, NetworkBehaviour, PollParameters,
        THandler, THandlerInEvent, ToSwarm,
    },
    Multiaddr, PeerId, StreamProtocol,
};

mod handler;

#[derive(Default, Debug)]
pub struct Behaviour {
    events: VecDeque<ToSwarm<<Self as NetworkBehaviour>::ToSwarm, THandlerInEvent<Self>>>,
    protocol: Vec<StreamProtocol>,
}

impl Behaviour {
    pub fn iter(&self) -> impl Iterator<Item = &StreamProtocol> {
        self.protocol.iter()
    }
}

impl NetworkBehaviour for Behaviour {
    type ConnectionHandler = handler::Handler;
    type ToSwarm = void::Void;

    fn handle_pending_inbound_connection(
        &mut self,
        _: ConnectionId,
        _: &Multiaddr,
        _: &Multiaddr,
    ) -> Result<(), ConnectionDenied> {
        Ok(())
    }

    fn handle_pending_outbound_connection(
        &mut self,
        _: ConnectionId,
        _: Option<PeerId>,
        _: &[Multiaddr],
        _: Endpoint,
    ) -> Result<Vec<Multiaddr>, ConnectionDenied> {
        Ok(vec![])
    }

    fn handle_established_inbound_connection(
        &mut self,
        _: ConnectionId,
        _: PeerId,
        _: &Multiaddr,
        _: &Multiaddr,
    ) -> Result<THandler<Self>, ConnectionDenied> {
        Ok(handler::Handler::default())
    }

    fn handle_established_outbound_connection(
        &mut self,
        _: ConnectionId,
        _: PeerId,
        _: &Multiaddr,
        _: Endpoint,
    ) -> Result<THandler<Self>, ConnectionDenied> {
        Ok(handler::Handler::default())
    }

    fn on_connection_handler_event(
        &mut self,
        _: PeerId,
        _: ConnectionId,
        event: swarm::THandlerOutEvent<Self>,
    ) {
        match event {
            handler::Out::Protocol(protocol) => self.protocol = protocol,
        }
    }

    fn on_swarm_event(&mut self, event: FromSwarm<Self::ConnectionHandler>) {
        match event {
            FromSwarm::AddressChange(_)
            | FromSwarm::ConnectionEstablished(_)
            | FromSwarm::ConnectionClosed(_)
            | FromSwarm::DialFailure(_)
            | FromSwarm::ListenFailure(_)
            | FromSwarm::NewListener(_)
            | FromSwarm::NewListenAddr(_)
            | FromSwarm::ExpiredListenAddr(_)
            | FromSwarm::ListenerError(_)
            | FromSwarm::ListenerClosed(_)
            | FromSwarm::ExternalAddrConfirmed(_)
            | FromSwarm::ExternalAddrExpired(_)
            | FromSwarm::NewExternalAddrCandidate(_) => {}
        }
    }

    fn poll(
        &mut self,
        _: &mut Context,
        _: &mut impl PollParameters,
    ) -> Poll<ToSwarm<Self::ToSwarm, THandlerInEvent<Self>>> {
        if let Some(event) = self.events.pop_front() {
            return Poll::Ready(event);
        }
        Poll::Pending
    }
}

handler

use std::{
    collections::VecDeque,
    task::{Context, Poll},
};

use libp2p::{
    core::upgrade::DeniedUpgrade,
    swarm::{
        handler::ConnectionEvent, ConnectionHandler, ConnectionHandlerEvent, KeepAlive,
        SubstreamProtocol, SupportedProtocols,
    },
    StreamProtocol,
};
use void::Void;

#[allow(clippy::type_complexity)]
#[derive(Default, Debug)]
pub struct Handler {
    events: VecDeque<
        ConnectionHandlerEvent<
            <Self as ConnectionHandler>::OutboundProtocol,
            <Self as ConnectionHandler>::OutboundOpenInfo,
            <Self as ConnectionHandler>::ToBehaviour,
            <Self as ConnectionHandler>::Error,
        >,
    >,
    supported_protocol: SupportedProtocols,
}

#[derive(Debug, Clone)]
pub enum Out {
    Protocol(Vec<StreamProtocol>),
}

impl ConnectionHandler for Handler {
    type FromBehaviour = Void;
    type ToBehaviour = Out;
    type Error = Void;
    type InboundProtocol = DeniedUpgrade;
    type OutboundProtocol = DeniedUpgrade;
    type InboundOpenInfo = ();
    type OutboundOpenInfo = Void;

    fn listen_protocol(&self) -> SubstreamProtocol<Self::InboundProtocol, Self::InboundOpenInfo> {
        SubstreamProtocol::new(DeniedUpgrade, ())
    }

    fn connection_keep_alive(&self) -> KeepAlive {
        KeepAlive::No
    }

    fn on_behaviour_event(&mut self, _: Self::FromBehaviour) {}

    fn on_connection_event(
        &mut self,
        event: ConnectionEvent<
            Self::InboundProtocol,
            Self::OutboundProtocol,
            Self::InboundOpenInfo,
            Self::OutboundOpenInfo,
        >,
    ) {
        match event {
            ConnectionEvent::LocalProtocolsChange(protocol) => {
                let change = self.supported_protocol.on_protocols_change(protocol);
                if change {
                    self.events
                        .push_back(ConnectionHandlerEvent::NotifyBehaviour(Out::Protocol(
                            self.supported_protocol.iter().cloned().collect(),
                        )));
                }
            }
            ConnectionEvent::RemoteProtocolsChange(_)
            | ConnectionEvent::FullyNegotiatedInbound(_)
            | ConnectionEvent::FullyNegotiatedOutbound(_)
            | ConnectionEvent::AddressChange(_)
            | ConnectionEvent::DialUpgradeError(_)
            | ConnectionEvent::ListenUpgradeError(_) => {}
        }
    }

    fn poll(
        &mut self,
        _: &mut Context<'_>,
    ) -> Poll<
        ConnectionHandlerEvent<
            Self::OutboundProtocol,
            Self::OutboundOpenInfo,
            Self::ToBehaviour,
            Self::Error,
        >,
    > {
        if let Some(event) = self.events.pop_front() {
            return Poll::Ready(event);
        }
        Poll::Pending
    }
}

[thomaseizinger]

seems to be redundant doing this as it relies on a peer connection.

Which protocols are supported is specific to a connection. See libp2p/specs#530.