convert the metrics reporter to an option

dial_sync_test.go

@@ -241,7 +241,7 @@ func TestDialSelf(t *testing.T) {
 	defer cancel()
 
 	self := peer.ID("ABC")
-	s := NewSwarm(self, nil, nil)
+	s := NewSwarm(self, nil)
 	defer s.Close()
 
 	// this should fail

swarm.go

@@ -50,6 +50,13 @@ func WithConnectionGater(gater connmgr.ConnectionGater) Option {
 	}
 }
 
+// WithMetrics sets a metrics reporter
+func WithMetrics(reporter metrics.Reporter) Option {
+	return func(s *Swarm) {
+		s.bwc = reporter
+	}
+}
+
 // Swarm is a connection muxer, allowing connections to other peers to
 // be opened and closed, while still using the same Chan for all
 // communication. The Chan sends/receives Messages, which note the
@@ -107,12 +114,11 @@ type Swarm struct {
 }
 
 // NewSwarm constructs a Swarm.
-func NewSwarm(local peer.ID, peers peerstore.Peerstore, bwc metrics.Reporter, opts ...Option) *Swarm {
+func NewSwarm(local peer.ID, peers peerstore.Peerstore, opts ...Option) *Swarm {
 	ctx, cancel := context.WithCancel(context.Background())
 	s := &Swarm{
 		local:     local,
 		peers:     peers,
-		bwc:       bwc,
 		ctx:       ctx,
 		ctxCancel: cancel,
 	}

testing/testing.go

@@ -113,11 +113,11 @@ func GenSwarm(t *testing.T, opts ...Option) *swarm.Swarm {
 	ps.AddPrivKey(p.ID, p.PrivKey)
 	t.Cleanup(func() { ps.Close() })
 
-	var swarmOpts []swarm.Option
+	swarmOpts := []swarm.Option{swarm.WithMetrics(metrics.NewBandwidthCounter())}
 	if cfg.connectionGater != nil {
 		swarmOpts = append(swarmOpts, swarm.WithConnectionGater(cfg.connectionGater))
 	}
-	s := swarm.NewSwarm(p.ID, ps, metrics.NewBandwidthCounter(), swarmOpts...)
+	s := swarm.NewSwarm(p.ID, ps, swarmOpts...)
 
 	upgrader := GenUpgrader(s)
 	upgrader.ConnGater = cfg.connectionGater