use functional options to configure the swarm

swarm.go

@@ -41,6 +41,22 @@ var ErrAddrFiltered = errors.New("address filtered")
 // ErrDialTimeout is returned when one a dial times out due to the global timeout
 var ErrDialTimeout = errors.New("dial timed out")
 
+type Option func(*Swarm)
+
+// WithConnectionGater sets a connection gater
+func WithConnectionGater(gater connmgr.ConnectionGater) Option {
+	return func(s *Swarm) {
+		s.gater = gater
+	}
+}
+
+// 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
@@ -98,17 +114,11 @@ type Swarm struct {
 }
 
 // NewSwarm constructs a Swarm.
-//
-// NOTE: go-libp2p will be moving to dependency injection soon. The variadic
-// `extra` interface{} parameter facilitates the future migration. Supported
-// elements are:
-//  - connmgr.ConnectionGater
-func NewSwarm(local peer.ID, peers peerstore.Peerstore, bwc metrics.Reporter, extra ...interface{}) *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,
 	}
@@ -118,11 +128,8 @@ func NewSwarm(local peer.ID, peers peerstore.Peerstore, bwc metrics.Reporter, ex
 	s.transports.m = make(map[int]transport.Transport)
 	s.notifs.m = make(map[network.Notifiee]struct{})
 
-	for _, i := range extra {
-		switch v := i.(type) {
-		case connmgr.ConnectionGater:
-			s.gater = v
-		}
+	for _, opt := range opts {
+		opt(s)
 	}
 
 	s.dsync = newDialSync(s.dialWorkerLoop)

swarm_test.go

@@ -16,7 +16,7 @@ import (
 	"github.com/libp2p/go-libp2p-core/peer"
 	"github.com/libp2p/go-libp2p-core/peerstore"
 
-	. "github.com/libp2p/go-libp2p-swarm"
+	swarm "github.com/libp2p/go-libp2p-swarm"
 	. "github.com/libp2p/go-libp2p-swarm/testing"
 
 	logging "github.com/ipfs/go-log"
@@ -58,14 +58,14 @@ func EchoStreamHandler(stream network.Stream) {
 	}()
 }
 
-func makeDialOnlySwarm(t *testing.T) *Swarm {
+func makeDialOnlySwarm(t *testing.T) *swarm.Swarm {
 	swarm := GenSwarm(t, OptDialOnly)
 	swarm.SetStreamHandler(EchoStreamHandler)
 	return swarm
 }
 
-func makeSwarms(t *testing.T, num int, opts ...Option) []*Swarm {
-	swarms := make([]*Swarm, 0, num)
+func makeSwarms(t *testing.T, num int, opts ...Option) []*swarm.Swarm {
+	swarms := make([]*swarm.Swarm, 0, num)
 	for i := 0; i < num; i++ {
 		swarm := GenSwarm(t, opts...)
 		swarm.SetStreamHandler(EchoStreamHandler)
@@ -74,9 +74,9 @@ func makeSwarms(t *testing.T, num int, opts ...Option) []*Swarm {
 	return swarms
 }
 
-func connectSwarms(t *testing.T, ctx context.Context, swarms []*Swarm) {
+func connectSwarms(t *testing.T, ctx context.Context, swarms []*swarm.Swarm) {
 	var wg sync.WaitGroup
-	connect := func(s *Swarm, dst peer.ID, addr ma.Multiaddr) {
+	connect := func(s *swarm.Swarm, dst peer.ID, addr ma.Multiaddr) {
 		// TODO: make a DialAddr func.
 		s.Peerstore().AddAddr(dst, addr, peerstore.PermanentAddrTTL)
 		if _, err := s.DialPeer(ctx, dst); err != nil {
@@ -455,7 +455,7 @@ func TestPreventDialListenAddr(t *testing.T) {
 	remote := peer.ID("foobar")
 	s.Peerstore().AddAddr(remote, addr, time.Hour)
 	_, err = s.DialPeer(context.Background(), remote)
-	if !errors.Is(err, ErrNoGoodAddresses) {
+	if !errors.Is(err, swarm.ErrNoGoodAddresses) {
 		t.Fatal("expected dial to fail: %w", err)
 	}
 }

testing/testing.go

@@ -113,7 +113,11 @@ func GenSwarm(t *testing.T, opts ...Option) *swarm.Swarm {
 	ps.AddPrivKey(p.ID, p.PrivKey)
 	t.Cleanup(func() { ps.Close() })
 
-	s := swarm.NewSwarm(p.ID, ps, metrics.NewBandwidthCounter(), cfg.connectionGater)
+	swarmOpts := []swarm.Option{swarm.WithMetrics(metrics.NewBandwidthCounter())}
+	if cfg.connectionGater != nil {
+		swarmOpts = append(swarmOpts, swarm.WithConnectionGater(cfg.connectionGater))
+	}
+	s := swarm.NewSwarm(p.ID, ps, swarmOpts...)
 
 	upgrader := GenUpgrader(s)
 	upgrader.ConnGater = cfg.connectionGater