Get rid of make(X, 0)

This can be replaced by one of several different, shorter constructs
depending on context.

This fixes some lint output.

bench/bench_writer/bench_writer.go

@@ -31,9 +31,9 @@ func main() {
 	log.SetPrefix("[bench_writer] ")
 
 	msg := make([]byte, *size)
-	batch := make([][]byte, 0)
-	for i := 0; i < *batchSize; i++ {
-		batch = append(batch, msg)
+	batch := make([][]byte, *batchSize)
+	for i := range batch {
+		batch[i] = msg
 	}
 
 	goChan := make(chan int)

nsqd/http_test.go

@@ -72,9 +72,9 @@ func TestHTTPmput(t *testing.T) {
 	topic := nsqd.GetTopic(topicName)
 
 	msg := []byte("test message")
-	msgs := make([][]byte, 0)
-	for i := 0; i < 4; i++ {
-		msgs = append(msgs, msg)
+	msgs := make([][]byte, 4)
+	for i := range msgs {
+		msgs[i] = msg
 	}
 	buf := bytes.NewBuffer(bytes.Join(msgs, []byte("\n")))
 
@@ -100,9 +100,9 @@ func TestHTTPmputEmpty(t *testing.T) {
 	topic := nsqd.GetTopic(topicName)
 
 	msg := []byte("test message")
-	msgs := make([][]byte, 0)
-	for i := 0; i < 4; i++ {
-		msgs = append(msgs, msg)
+	msgs := make([][]byte, 4)
+	for i := range msgs {
+		msgs[i] = msg
 	}
 	buf := bytes.NewBuffer(bytes.Join(msgs, []byte("\n")))
 	_, err := buf.Write([]byte("\n"))
@@ -129,9 +129,9 @@ func TestHTTPmputBinary(t *testing.T) {
 	topicName := "test_http_mput_bin" + strconv.Itoa(int(time.Now().Unix()))
 	topic := nsqd.GetTopic(topicName)
 
-	mpub := make([][]byte, 0)
-	for i := 0; i < 5; i++ {
-		mpub = append(mpub, make([]byte, 100))
+	mpub := make([][]byte, 5)
+	for i := range mpub {
+		mpub[i] = make([]byte, 100)
 	}
 	cmd, _ := nsq.MultiPublish(topicName, mpub)
 	buf := bytes.NewBuffer(cmd.Body)

nsqd/lookup.go

@@ -105,7 +105,7 @@ func (n *NSQD) lookupLoop() {
 				}
 			}
 		case lookupPeer := <-syncTopicChan:
-			commands := make([]*nsq.Command, 0)
+			var commands []*nsq.Command
 			// build all the commands first so we exit the lock(s) as fast as possible
 			n.RLock()
 			for _, topic := range n.topicMap {

nsqd/nsqd.go

@@ -307,15 +307,15 @@ func (n *NSQD) PersistMetadata() error {
 	n.logf("NSQ: persisting topic/channel metadata to %s", fileName)
 
 	js := make(map[string]interface{})
-	topics := make([]interface{}, 0)
+	topics := []interface{}{}
 	for _, topic := range n.topicMap {
 		if topic.ephemeral {
 			continue
 		}
 		topicData := make(map[string]interface{})
 		topicData["name"] = topic.name
 		topicData["paused"] = topic.IsPaused()
-		channels := make([]interface{}, 0)
+		channels := []interface{}{}
 		topic.Lock()
 		for _, channel := range topic.channelMap {
 			channel.Lock()

nsqd/protocol_v2_test.go

@@ -460,7 +460,7 @@ func TestSizeLimits(t *testing.T) {
 	defer conn.Close()
 
 	// PUB thats empty
-	nsq.Publish(topicName, make([]byte, 0)).WriteTo(conn)
+	nsq.Publish(topicName, []byte{}).WriteTo(conn)
 	resp, _ = nsq.ReadResponse(conn)
 	frameType, data, _ = nsq.UnpackResponse(resp)
 	t.Logf("frameType: %d, data: %s", frameType, data)
@@ -473,9 +473,9 @@ func TestSizeLimits(t *testing.T) {
 	defer conn.Close()
 
 	// MPUB body that's valid
-	mpub := make([][]byte, 0)
-	for i := 0; i < 5; i++ {
-		mpub = append(mpub, make([]byte, 100))
+	mpub := make([][]byte, 5)
+	for i := range mpub {
+		mpub[i] = make([]byte, 100)
 	}
 	cmd, _ := nsq.MultiPublish(topicName, mpub)
 	cmd.WriteTo(conn)
@@ -486,9 +486,9 @@ func TestSizeLimits(t *testing.T) {
 	equal(t, data, []byte("OK"))
 
 	// MPUB body that's invalid (body too big)
-	mpub = make([][]byte, 0)
-	for i := 0; i < 11; i++ {
-		mpub = append(mpub, make([]byte, 100))
+	mpub = make([][]byte, 11)
+	for i := range mpub {
+		mpub[i] = make([]byte, 100)
 	}
 	cmd, _ = nsq.MultiPublish(topicName, mpub)
 	cmd.WriteTo(conn)
@@ -504,11 +504,11 @@ func TestSizeLimits(t *testing.T) {
 	defer conn.Close()
 
 	// MPUB that's invalid (one message empty)
-	mpub = make([][]byte, 0)
-	for i := 0; i < 5; i++ {
-		mpub = append(mpub, make([]byte, 100))
+	mpub = make([][]byte, 5)
+	for i := range mpub {
+		mpub[i] = make([]byte, 100)
 	}
-	mpub = append(mpub, make([]byte, 0))
+	mpub = append(mpub, []byte{})
 	cmd, _ = nsq.MultiPublish(topicName, mpub)
 	cmd.WriteTo(conn)
 	resp, _ = nsq.ReadResponse(conn)
@@ -523,9 +523,9 @@ func TestSizeLimits(t *testing.T) {
 	defer conn.Close()
 
 	// MPUB body that's invalid (one of the messages is too big)
-	mpub = make([][]byte, 0)
-	for i := 0; i < 5; i++ {
-		mpub = append(mpub, make([]byte, 101))
+	mpub = make([][]byte, 5)
+	for i := range mpub {
+		mpub[i] = make([]byte, 101)
 	}
 	cmd, _ = nsq.MultiPublish(topicName, mpub)
 	cmd.WriteTo(conn)
@@ -1402,9 +1402,9 @@ func benchmarkProtocolV2Pub(b *testing.B, size int) {
 	tcpAddr, _, nsqd := mustStartNSQD(opts)
 	msg := make([]byte, size)
 	batchSize := 200
-	batch := make([][]byte, 0)
-	for i := 0; i < batchSize; i++ {
-		batch = append(batch, msg)
+	batch := make([][]byte, batchSize)
+	for i := range batch {
+		batch[i] = msg
 	}
 	topicName := "bench_v2_pub" + strconv.Itoa(int(time.Now().Unix()))
 	b.SetBytes(int64(len(msg)))

nsqd/statsd.go

@@ -26,7 +26,7 @@ func (s Uint64Slice) Less(i, j int) bool {
 
 func (n *NSQD) statsdLoop() {
 	var lastMemStats runtime.MemStats
-	lastStats := make([]TopicStats, 0)
+	var lastStats []TopicStats
 	ticker := time.NewTicker(n.opts.StatsdInterval)
 	for {
 		select {

nsqd/topic.go

@@ -233,7 +233,7 @@ func (t *Topic) messagePump() {
 				continue
 			}
 		case <-t.channelUpdateChan:
-			chans = make([]*Channel, 0)
+			chans = chans[:0]
 			t.RLock()
 			for _, c := range t.channelMap {
 				chans = append(chans, c)

nsqlookupd/registration_db.go

@@ -63,7 +63,7 @@ func (r *RegistrationDB) AddRegistration(k Registration) {
 	defer r.Unlock()
 	_, ok := r.registrationMap[k]
 	if !ok {
-		r.registrationMap[k] = make(Producers, 0)
+		r.registrationMap[k] = Producers{}
 	}
 }
 
@@ -93,7 +93,7 @@ func (r *RegistrationDB) RemoveProducer(k Registration, id string) (bool, int) {
 		return false, 0
 	}
 	removed := false
-	cleaned := make(Producers, 0)
+	cleaned := Producers{}
 	for _, producer := range producers {
 		if producer.peerInfo.id != id {
 			cleaned = append(cleaned, producer)
@@ -116,7 +116,7 @@ func (r *RegistrationDB) RemoveRegistration(k Registration) {
 func (r *RegistrationDB) FindRegistrations(category string, key string, subkey string) Registrations {
 	r.RLock()
 	defer r.RUnlock()
-	results := make(Registrations, 0)
+	results := Registrations{}
 	for k := range r.registrationMap {
 		if !k.IsMatch(category, key, subkey) {
 			continue
@@ -129,7 +129,7 @@ func (r *RegistrationDB) FindRegistrations(category string, key string, subkey s
 func (r *RegistrationDB) FindProducers(category string, key string, subkey string) Producers {
 	r.RLock()
 	defer r.RUnlock()
-	results := make(Producers, 0)
+	results := Producers{}
 	for k, producers := range r.registrationMap {
 		if !k.IsMatch(category, key, subkey) {
 			continue
@@ -152,7 +152,7 @@ func (r *RegistrationDB) FindProducers(category string, key string, subkey strin
 func (r *RegistrationDB) LookupRegistrations(id string) Registrations {
 	r.RLock()
 	defer r.RUnlock()
-	results := make(Registrations, 0)
+	results := Registrations{}
 	for k, producers := range r.registrationMap {
 		for _, p := range producers {
 			if p.peerInfo.id == id {
@@ -178,7 +178,7 @@ func (k Registration) IsMatch(category string, key string, subkey string) bool {
 }
 
 func (rr Registrations) Filter(category string, key string, subkey string) Registrations {
-	output := make(Registrations, 0)
+	output := Registrations{}
 	for _, k := range rr {
 		if k.IsMatch(category, key, subkey) {
 			output = append(output, k)
@@ -205,7 +205,7 @@ func (rr Registrations) SubKeys() []string {
 
 func (pp Producers) FilterByActive(inactivityTimeout time.Duration, tombstoneLifetime time.Duration) Producers {
 	now := time.Now()
-	results := make(Producers, 0)
+	results := Producers{}
 	for _, p := range pp {
 		cur := time.Unix(0, atomic.LoadInt64(&p.peerInfo.lastUpdate))
 		if now.Sub(cur) > inactivityTimeout || p.IsTombstoned(tombstoneLifetime) {
@@ -217,7 +217,7 @@ func (pp Producers) FilterByActive(inactivityTimeout time.Duration, tombstoneLif
 }
 
 func (pp Producers) PeerInfo() []*PeerInfo {
-	results := make([]*PeerInfo, 0)
+	results := []*PeerInfo{}
 	for _, p := range pp {
 		results = append(results, p.peerInfo)
 	}

util/lookupd/lookupd.go

@@ -33,7 +33,7 @@ func GetVersion(addr string) (*semver.Version, error) {
 // from all the given lookupd
 func GetLookupdTopics(lookupdHTTPAddrs []string) ([]string, error) {
 	success := false
-	allTopics := make([]string, 0)
+	var allTopics []string
 	var lock sync.Mutex
 	var wg sync.WaitGroup
 	for _, addr := range lookupdHTTPAddrs {
@@ -67,7 +67,7 @@ func GetLookupdTopics(lookupdHTTPAddrs []string) ([]string, error) {
 // from all the given lookupd for the given topic
 func GetLookupdTopicChannels(topic string, lookupdHTTPAddrs []string) ([]string, error) {
 	success := false
-	allChannels := make([]string, 0)
+	var allChannels []string
 	var lock sync.Mutex
 	var wg sync.WaitGroup
 	for _, addr := range lookupdHTTPAddrs {
@@ -101,8 +101,8 @@ func GetLookupdTopicChannels(topic string, lookupdHTTPAddrs []string) ([]string,
 // containing metadata for each node connected to given lookupds
 func GetLookupdProducers(lookupdHTTPAddrs []string) ([]*Producer, error) {
 	success := false
-	allProducers := make(map[string]*Producer, 0)
-	output := make([]*Producer, 0)
+	allProducers := make(map[string]*Producer)
+	var output []*Producer
 	maxVersion, _ := semver.Parse("0.0.0")
 	var lock sync.Mutex
 	var wg sync.WaitGroup
@@ -202,7 +202,7 @@ func GetLookupdProducers(lookupdHTTPAddrs []string) ([]*Producer, error) {
 // producers for a given topic by unioning the results returned from the given lookupd
 func GetLookupdTopicProducers(topic string, lookupdHTTPAddrs []string) ([]string, error) {
 	success := false
-	allSources := make([]string, 0)
+	var allSources []string
 	var lock sync.Mutex
 	var wg sync.WaitGroup
 
@@ -243,7 +243,7 @@ func GetLookupdTopicProducers(topic string, lookupdHTTPAddrs []string) ([]string
 // GetNSQDTopics returns a []string containing all the topics
 // produced by the given nsqd
 func GetNSQDTopics(nsqdHTTPAddrs []string) ([]string, error) {
-	topics := make([]string, 0)
+	var topics []string
 	var lock sync.Mutex
 	var wg sync.WaitGroup
 	success := false
@@ -280,7 +280,7 @@ func GetNSQDTopics(nsqdHTTPAddrs []string) ([]string, error) {
 // GetNSQDTopicProducers returns a []string containing the addresses of all the nsqd
 // that produce the given topic out of the given nsqd
 func GetNSQDTopicProducers(topic string, nsqdHTTPAddrs []string) ([]string, error) {
-	addresses := make([]string, 0)
+	var addresses []string
 	var lock sync.Mutex
 	var wg sync.WaitGroup
 	success := false
@@ -324,7 +324,7 @@ func GetNSQDStats(nsqdHTTPAddrs []string, selectedTopic string) ([]*TopicStats,
 	var lock sync.Mutex
 	var wg sync.WaitGroup
 
-	topicStatsList := make(TopicStatsList, 0)
+	var topicStatsList TopicStatsList
 	channelStatsMap := make(map[string]*ChannelStats)
 
 	success := false