swarm: deprecate libp2p.DialRanker option (#2430)

* swarm: deprecate libp2p.DialRanker option

* remove whitespace diff

* Apply suggestions from code review

Co-authored-by: Marten Seemann <martenseemann@gmail.com>

---------

Co-authored-by: Marten Seemann <martenseemann@gmail.com>

config/config.go

@@ -178,12 +178,9 @@ func (cfg *Config) makeSwarm(eventBus event.Bus, enableMetrics bool) (*swarm.Swa
 	if cfg.MultiaddrResolver != nil {
 		opts = append(opts, swarm.WithMultiaddrResolver(cfg.MultiaddrResolver))
 	}
-
-	dialRanker := cfg.DialRanker
-	if dialRanker == nil {
-		dialRanker = swarm.DefaultDialRanker
+	if cfg.DialRanker != nil {
+		opts = append(opts, swarm.WithDialRanker(cfg.DialRanker))
 	}
-	opts = append(opts, swarm.WithDialRanker(dialRanker))
 
 	if enableMetrics {
 		opts = append(opts,

options.go

@@ -579,6 +579,7 @@ func PrometheusRegisterer(reg prometheus.Registerer) Option {
 // DialRanker configures libp2p to use d as the dial ranker. To enable smart
 // dialing use `swarm.DefaultDialRanker`. use `swarm.NoDelayDialRanker` to
 // disable smart dialing.
+// Deprecated: use SwarmOpts(swarm.WithDialRanker(d)) instead
 func DialRanker(d network.DialRanker) Option {
 	return func(cfg *Config) error {
 		if cfg.DialRanker != nil {

p2p/net/swarm/swarm.go

@@ -103,6 +103,9 @@ func WithResourceManager(m network.ResourceManager) Option {
 // WithDialRanker configures swarm to use d as the DialRanker
 func WithDialRanker(d network.DialRanker) Option {
 	return func(s *Swarm) error {
+		if d == nil {
+			return errors.New("swarm: dial ranker cannot be nil")
+		}
 		s.dialRanker = d
 		return nil
 	}