chore: Fix linter findings for `revive:enforce-slice-style` in `plugins/parsers`, `plugins/processors`, `plugins/secretstores` and `plugins/serializers` (#15980)

plugins/parsers/collectd/parser.go

@@ -71,7 +71,7 @@ func (p *Parser) Parse(buf []byte) ([]telegraf.Metric, error) {
 		return nil, fmt.Errorf("collectd parser error: %w", err)
 	}
 
-	metrics := []telegraf.Metric{}
+	metrics := make([]telegraf.Metric, 0, len(valueLists))
 	for _, valueList := range valueLists {
 		metrics = append(metrics, p.unmarshalValueList(valueList)...)
 	}

plugins/parsers/collectd/parser_test.go

@@ -221,7 +221,7 @@ func TestParse_SignSecurityLevel(t *testing.T) {
 
 	metrics, err = parser.Parse(bytes)
 	require.NoError(t, err)
-	require.Equal(t, []telegraf.Metric{}, metrics)
+	require.Empty(t, metrics)
 
 	// Wrong password error
 	buf, err = writeValueList(singleMetric.vl)
@@ -250,7 +250,7 @@ func TestParse_EncryptSecurityLevel(t *testing.T) {
 
 	metrics, err := parser.Parse(bytes)
 	require.NoError(t, err)
-	require.Equal(t, []telegraf.Metric{}, metrics)
+	require.Empty(t, metrics)
 
 	// Encrypted data
 	buf, err = writeValueList(singleMetric.vl)
@@ -271,7 +271,7 @@ func TestParse_EncryptSecurityLevel(t *testing.T) {
 
 	metrics, err = parser.Parse(bytes)
 	require.NoError(t, err)
-	require.Equal(t, []telegraf.Metric{}, metrics)
+	require.Empty(t, metrics)
 
 	// Wrong password error
 	buf, err = writeValueList(singleMetric.vl)

plugins/parsers/csv/parser.go

@@ -84,7 +84,6 @@ func (record metadataPattern) Less(i, j int) bool {
 func (p *Parser) initializeMetadataSeparators() error {
 	// initialize metadata
 	p.metadataTags = map[string]string{}
-	p.metadataSeparatorList = []string{}
 
 	if p.MetadataRows <= 0 {
 		return nil
@@ -94,7 +93,7 @@ func (p *Parser) initializeMetadataSeparators() error {
 		return errors.New("csv_metadata_separators required when specifying csv_metadata_rows")
 	}
 
-	p.metadataSeparatorList = metadataPattern{}
+	p.metadataSeparatorList = make(metadataPattern, 0, len(p.MetadataSeparators))
 	patternList := map[string]bool{}
 	for _, pattern := range p.MetadataSeparators {
 		if patternList[pattern] {

plugins/parsers/csv/parser_test.go

@@ -80,7 +80,7 @@ func TestHeaderOverride(t *testing.T) {
 	require.NoError(t, err)
 	metrics, err = p.Parse([]byte(testCSVRows[0]))
 	require.NoError(t, err)
-	require.Equal(t, []telegraf.Metric{}, metrics)
+	require.Empty(t, metrics)
 	m, err := p.ParseLine(testCSVRows[1])
 	require.NoError(t, err)
 	require.Equal(t, "test_name", m.Name())
@@ -849,14 +849,12 @@ func TestParseMetadataSeparators(t *testing.T) {
 	p := &Parser{
 		ColumnNames:  []string{"a", "b"},
 		MetadataRows: 0,
-		MetadataSeparators: []string{},
 	}
 	err := p.Init()
 	require.NoError(t, err)
 	p = &Parser{
 		ColumnNames:  []string{"a", "b"},
 		MetadataRows: 1,
-		MetadataSeparators: []string{},
 	}
 	err = p.Init()
 	require.Error(t, err)

plugins/parsers/influx/influx_upstream/parser.go

@@ -263,7 +263,7 @@ func (sp *StreamParser) Next() (telegraf.Metric, error) {
 
 	m, err := nextMetric(sp.decoder, sp.precision, sp.defaultTime, false)
 	if err != nil {
-		return nil, convertToParseError([]byte{}, err)
+		return nil, convertToParseError(nil, err)
 	}
 
 	return m, nil

plugins/parsers/influx/influx_upstream/parser_test.go

@@ -685,7 +685,6 @@ func TestSeriesParser(t *testing.T) {
 		{
 			name:  "empty",
 			input: []byte(""),
-			metrics: []telegraf.Metric{},
 		},
 		{
 			name:  "minimal",
@@ -717,7 +716,6 @@ func TestSeriesParser(t *testing.T) {
 		{
 			name:  "missing tag value",
 			input: []byte("cpu,a="),
-			metrics: []telegraf.Metric{},
 			err: &ParseError{
 				DecodeError: &lineprotocol.DecodeError{
 					Line:   1,
@@ -730,7 +728,6 @@ func TestSeriesParser(t *testing.T) {
 		{
 			name:  "error with carriage return in long line",
 			input: []byte("cpu,a=" + strings.Repeat("x", maxErrorBufferSize) + "\rcd,b"),
-			metrics: []telegraf.Metric{},
 			err: &ParseError{
 				DecodeError: &lineprotocol.DecodeError{
 					Line:   1,

plugins/parsers/influx/parser_test.go

@@ -763,7 +763,6 @@ func TestSeriesParser(t *testing.T) {
 		{
 			name:  "empty",
 			input: []byte(""),
-			metrics: []telegraf.Metric{},
 		},
 		{
 			name:  "minimal",
@@ -795,7 +794,6 @@ func TestSeriesParser(t *testing.T) {
 		{
 			name:  "missing tag value",
 			input: []byte("cpu,a="),
-			metrics: []telegraf.Metric{},
 			err: &ParseError{
 				Offset:     6,
 				LineNumber: 1,
@@ -807,7 +805,6 @@ func TestSeriesParser(t *testing.T) {
 		{
 			name:  "error with carriage return in long line",
 			input: []byte("cpu,a=" + strings.Repeat("x", maxErrorBufferSize) + "\rcd,b"),
-			metrics: []telegraf.Metric{},
 			err: &ParseError{
 				Offset:     1031,
 				LineNumber: 1,

plugins/parsers/json/parser_test.go

@@ -602,7 +602,6 @@ func TestJSONQueryErrorOnArray(t *testing.T) {
 
 	parser := &Parser{
 		MetricName: "json_test",
-		TagKeys:    []string{},
 		Query:      "shares.myArr",
 	}
 	require.NoError(t, parser.Init())
@@ -913,19 +912,16 @@ func TestParse(t *testing.T) {
 			name:   "parse empty array",
 			parser: &Parser{},
 			input:  []byte(`[]`),
-			expected: []telegraf.Metric{},
 		},
 		{
 			name:   "parse null",
 			parser: &Parser{},
 			input:  []byte(`null`),
-			expected: []telegraf.Metric{},
 		},
 		{
 			name:   "parse null with query",
 			parser: &Parser{Query: "result.data"},
 			input:  []byte(`{"error":null,"result":{"data":null,"items_per_page":10,"total_items":0,"total_pages":0}}`),
-			expected: []telegraf.Metric{},
 		},
 		{
 			name: "parse simple array",

plugins/parsers/json_v2/parser_test.go

@@ -101,10 +101,7 @@ func TestMultipleConfigs(t *testing.T) {
 }
 
 func TestParserEmptyConfig(t *testing.T) {
-	plugin := &json_v2.Parser{
-		Configs: []json_v2.Config{},
-	}
-
+	plugin := &json_v2.Parser{}
 	require.ErrorContains(t, plugin.Init(), "no configuration provided")
 }
 

plugins/parsers/logfmt/parser_test.go

@@ -21,7 +21,6 @@ func TestParse(t *testing.T) {
 	}{
 		{
 			name: "no bytes returns no metrics",
-			want: []telegraf.Metric{},
 		},
 		{
 			name:        "test without trailing end",
@@ -104,27 +103,23 @@ func TestParse(t *testing.T) {
 		{
 			name:    "keys without = or values are ignored",
 			bytes:   []byte(`i am no data.`),
-			want:    []telegraf.Metric{},
 			wantErr: false,
 		},
 		{
 			name:    "keys without values are ignored",
 			bytes:   []byte(`foo="" bar=`),
-			want:    []telegraf.Metric{},
 			wantErr: false,
 		},
 		{
 			name:        "unterminated quote produces error",
 			measurement: "testlog",
 			bytes:       []byte(`bar=baz foo="bar`),
-			want:        []telegraf.Metric{},
 			wantErr:     true,
 		},
 		{
 			name:        "malformed key",
 			measurement: "testlog",
 			bytes:       []byte(`"foo=" bar=baz`),
-			want:        []telegraf.Metric{},
 			wantErr:     true,
 		},
 	}

plugins/parsers/nagios/parser_test.go

@@ -148,7 +148,7 @@ func TestTryAddState(t *testing.T) {
 			runErrF: func() error {
 				return nil
 			},
-			metrics: []telegraf.Metric{},
+			metrics: make([]telegraf.Metric, 0),
 			assertF: func(t *testing.T, metrics []telegraf.Metric) {
 				require.Len(t, metrics, 1)
 				m := metrics[0]

plugins/parsers/value/parser.go

@@ -53,7 +53,7 @@ func (v *Parser) Parse(buf []byte) ([]telegraf.Metric, error) {
 	if v.DataType != "string" {
 		values := strings.Fields(vStr)
 		if len(values) < 1 {
-			return []telegraf.Metric{}, nil
+			return nil, nil
 		}
 		vStr = values[len(values)-1]
 	}

plugins/parsers/xpath/parser.go

@@ -562,7 +562,7 @@ func splitLastPathElement(query string) []string {
 
 	// Nothing left
 	if query == "" || query == "/" || query == "//" || query == "." {
-		return []string{}
+		return nil
 	}
 
 	separatorIdx := strings.LastIndex(query, "/")

plugins/parsers/xpath/parser_test.go

@@ -1388,7 +1388,6 @@ func TestProtobufImporting(t *testing.T) {
 		ProtobufMessageDef:  "person.proto",
 		ProtobufMessageType: "importtest.Person",
 		ProtobufImportPaths: []string{"testcases/protos"},
-		Configs:             []Config{},
 		Log:                 testutil.Logger{Name: "parsers.protobuf"},
 	}
 	require.NoError(t, parser.Init())

plugins/processors/aws_ec2/ec2_test.go

@@ -65,7 +65,6 @@ func TestBasicStartupWithTagCacheSize(t *testing.T) {
 func TestBasicInitNoTagsReturnAnError(t *testing.T) {
 	p := newAwsEc2Processor()
 	p.Log = &testutil.Logger{}
-	p.ImdsTags = []string{}
 	err := p.Init()
 	require.Error(t, err)
 }

plugins/processors/filter/filter_test.go

@@ -95,7 +95,7 @@ func TestNoMetric(t *testing.T) {
 	}
 	require.NoError(t, plugin.Init())
 
-	input := []telegraf.Metric{}
+	var input []telegraf.Metric
 	require.Empty(t, plugin.Apply(input...))
 }
 

plugins/processors/parser/parser.go

@@ -46,9 +46,9 @@ func (p *Parser) SetParser(parser telegraf.Parser) {
 }
 
 func (p *Parser) Apply(metrics ...telegraf.Metric) []telegraf.Metric {
-	results := []telegraf.Metric{}
+	results := make([]telegraf.Metric, 0, len(metrics))
 	for _, metric := range metrics {
-		newMetrics := []telegraf.Metric{}
+		var newMetrics []telegraf.Metric
 		if !p.DropOriginal {
 			newMetrics = append(newMetrics, metric)
 		} else {

plugins/processors/reverse_dns/rdnscache.go

@@ -69,7 +69,6 @@ func NewReverseDNSCache(ttl, lookupTimeout time.Duration, workerPoolSize int) *R
 		ttl:                 ttl,
 		lookupTimeout:       lookupTimeout,
 		cache:               map[string]*dnslookup{},
-		expireList:          []*dnslookup{},
 		maxWorkers:          workerPoolSize,
 		sem:                 semaphore.NewWeighted(int64(workerPoolSize)),
 		cancelCleanupWorker: cancel,
@@ -272,7 +271,7 @@ func (d *ReverseDNSCache) cleanup() {
 		d.expireListLock.Unlock()
 		return
 	}
-	ipsToDelete := []string{}
+	ipsToDelete := make([]string, 0, len(d.expireList))
 	for i := 0; i < len(d.expireList); i++ {
 		if !d.expireList[i].expiresAt.Before(now) {
 			break // done. Nothing after this point is expired.

plugins/processors/split/split.go

@@ -65,7 +65,7 @@ func (s *Split) Init() error {
 }
 
 func (s *Split) Apply(in ...telegraf.Metric) []telegraf.Metric {
-	newMetrics := []telegraf.Metric{}
+	newMetrics := make([]telegraf.Metric, 0, len(in)*(len(s.Templates)+1))
 
 	for _, point := range in {
 		if s.DropOriginal {

plugins/processors/starlark/starlark_test.go

@@ -113,7 +113,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected: []telegraf.Metric{},
 		},
 		{
 			name: "passthrough",
@@ -185,7 +184,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "append: cannot append to frozen list",
 		},
 		{
@@ -348,7 +346,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "type error",
 		},
 		{
@@ -417,7 +414,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot set tags",
 		},
 		{
@@ -546,7 +542,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: `key "foo" not in Tags`,
 		},
 		{
@@ -661,7 +656,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "tag value must be of type 'str'",
 		},
 		{
@@ -773,7 +767,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "popitem(): tag dictionary is empty",
 		},
 		{
@@ -1238,7 +1231,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "pop: cannot delete during iteration",
 		},
 		{
@@ -1261,7 +1253,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot delete during iteration",
 		},
 		{
@@ -1284,7 +1275,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot delete during iteration",
 		},
 		{
@@ -1307,7 +1297,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot insert during iteration",
 		},
 		{
@@ -1378,7 +1367,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot set fields",
 		},
 		{
@@ -1585,7 +1573,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: `key "foo" not in Fields`,
 		},
 		{
@@ -1771,7 +1758,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "invalid starlark type",
 		},
 		{
@@ -1887,7 +1873,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "popitem(): field dictionary is empty",
 		},
 		{
@@ -2309,7 +2294,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "pop: cannot delete during iteration",
 		},
 		{
@@ -2327,7 +2311,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot delete during iteration",
 		},
 		{
@@ -2345,7 +2328,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot delete during iteration",
 		},
 		{
@@ -2363,7 +2345,6 @@ def apply(metric):
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "cannot insert during iteration",
 		},
 		{
@@ -2435,7 +2416,6 @@ def apply(metric):
 					time.Unix(0, 0).UTC(),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "type error",
 		},
 		{
@@ -2909,7 +2889,6 @@ func TestScript(t *testing.T) {
 					time.Unix(0, 0),
 				),
 			},
-			expected:         []telegraf.Metric{},
 			expectedErrorStr: "fail: The field value should be greater than 1",
 		},
 	}
@@ -3306,7 +3285,7 @@ func TestAllScriptTestData(t *testing.T) {
 				lines := strings.Split(string(b), "\n")
 				inputMetrics := parseMetricsFrom(t, lines, "Example Input:")
 				expectedErrorStr := parseErrorMessage(t, lines, "Example Output Error:")
-				outputMetrics := []telegraf.Metric{}
+				var outputMetrics []telegraf.Metric
 				if expectedErrorStr == "" {
 					outputMetrics = parseMetricsFrom(t, lines, "Example Output:")
 				}

plugins/processors/topk/topk.go

@@ -48,8 +48,6 @@ func New() *TopK {
 	topk.Aggregation = "mean"
 	topk.GroupBy = []string{"*"}
 	topk.AddGroupByTag = ""
-	topk.AddRankFields = []string{}
-	topk.AddAggregateFields = []string{}
 
 	// Initialize cache
 	topk.Reset()
@@ -187,7 +185,7 @@ func (t *TopK) Apply(in ...telegraf.Metric) []telegraf.Metric {
 		return t.push()
 	}
 
-	return []telegraf.Metric{}
+	return nil
 }
 
 func convert(in interface{}) (float64, bool) {
@@ -211,7 +209,7 @@ func (t *TopK) push() []telegraf.Metric {
 		// If we could not generate the aggregation
 		// function, fail hard by dropping all metrics
 		t.Log.Errorf("%v", err)
-		return []telegraf.Metric{}
+		return nil
 	}
 	for k, ms := range t.cache {
 		aggregations = append(aggregations, MetricAggregation{groupbykey: k, values: aggregator(ms, t.Fields)})

plugins/processors/topk/topk_test.go

@@ -55,7 +55,7 @@ type metricChange struct {
 //	they are semantically equal.
 //	Therefore the fields and tags must be in the same order that the processor would add them
 func generateAns(input []telegraf.Metric, changeSet map[int]metricChange) []telegraf.Metric {
-	answer := []telegraf.Metric{}
+	answer := make([]telegraf.Metric, 0, len(input))
 
 	// For every input metric, we check if there is a change we need to apply
 	// If there is no change for a given input metric, the metric is dropped
@@ -411,7 +411,7 @@ func TestTopkGroupbyMetricName1(t *testing.T) {
 	topk.K = 1
 	topk.Aggregation = "sum"
 	topk.AddAggregateFields = []string{"value"}
-	topk.GroupBy = []string{}
+	topk.GroupBy = make([]string, 0)
 
 	// Get the input
 	input := deepCopy(MetricsSet2)

plugins/secretstores/http/decryption_test.go

@@ -14,7 +14,7 @@ func TestCreateAESFail(t *testing.T) {
 }
 
 func TestTrimPKCSFail(t *testing.T) {
-	_, err := PKCS5or7Trimming([]byte{})
+	_, err := PKCS5or7Trimming(nil)
 	require.ErrorContains(t, err, "empty value to trim")
 
 	_, err = PKCS5or7Trimming([]byte{0x00, 0x05})

plugins/serializers/graphite/graphite.go

@@ -84,7 +84,7 @@ func (s *GraphiteSerializer) Init() error {
 }
 
 func (s *GraphiteSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
-	out := []byte{}
+	var out []byte
 
 	// Convert UnixNano to Unix timestamps
 	timestamp := metric.Time().UnixNano() / 1000000000

plugins/serializers/json/json.go

@@ -70,7 +70,7 @@ func (s *Serializer) Serialize(metric telegraf.Metric) ([]byte, error) {
 
 	serialized, err := json.Marshal(obj)
 	if err != nil {
-		return []byte{}, err
+		return nil, err
 	}
 	serialized = append(serialized, '\n')
 
@@ -101,7 +101,7 @@ func (s *Serializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
 
 	serialized, err := json.Marshal(obj)
 	if err != nil {
-		return []byte{}, err
+		return nil, err
 	}
 	serialized = append(serialized, '\n')
 

plugins/serializers/prometheus/collection_test.go

@@ -49,7 +49,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_UNTYPED.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:   []*dto.LabelPair{},
+							Label:   make([]*dto.LabelPair, 0),
 							Untyped: &dto.Untyped{Value: proto.Float64(42.0)},
 						},
 					},
@@ -91,7 +91,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_UNTYPED.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:   []*dto.LabelPair{},
+							Label:   make([]*dto.LabelPair, 0),
 							Untyped: &dto.Untyped{Value: proto.Float64(43.0)},
 						},
 					},
@@ -132,7 +132,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_UNTYPED.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:   []*dto.LabelPair{},
+							Label:   make([]*dto.LabelPair, 0),
 							Untyped: &dto.Untyped{Value: proto.Float64(42.0)},
 						},
 					},
@@ -156,7 +156,7 @@ func TestCollectionExpire(t *testing.T) {
 					addtime: time.Unix(0, 0),
 				},
 			},
-			expected: []*dto.MetricFamily{},
+			expected: make([]*dto.MetricFamily, 0),
 		},
 		{
 			name: "expired one metric in metric family",
@@ -192,7 +192,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_UNTYPED.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:   []*dto.LabelPair{},
+							Label:   make([]*dto.LabelPair, 0),
 							Untyped: &dto.Untyped{Value: proto.Float64(42.0)},
 						},
 					},
@@ -282,7 +282,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_HISTOGRAM.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label: []*dto.LabelPair{},
+							Label: make([]*dto.LabelPair, 0),
 							Histogram: &dto.Histogram{
 								SampleCount: proto.Uint64(4),
 								SampleSum:   proto.Float64(20.0),
@@ -343,7 +343,7 @@ func TestCollectionExpire(t *testing.T) {
 					addtime: time.Unix(0, 0),
 				},
 			},
-			expected: []*dto.MetricFamily{},
+			expected: make([]*dto.MetricFamily, 0),
 		},
 		{
 			name: "histogram does not expire because of addtime from bucket",
@@ -393,7 +393,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_HISTOGRAM.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label: []*dto.LabelPair{},
+							Label: make([]*dto.LabelPair, 0),
 							Histogram: &dto.Histogram{
 								SampleCount: proto.Uint64(2),
 								SampleSum:   proto.Float64(10.0),
@@ -474,7 +474,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_SUMMARY.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label: []*dto.LabelPair{},
+							Label: make([]*dto.LabelPair, 0),
 							Summary: &dto.Summary{
 								SampleCount: proto.Uint64(2),
 								SampleSum:   proto.Float64(2.0),
@@ -520,7 +520,7 @@ func TestCollectionExpire(t *testing.T) {
 					addtime: time.Unix(0, 0),
 				},
 			},
-			expected: []*dto.MetricFamily{},
+			expected: make([]*dto.MetricFamily, 0),
 		},
 		{
 			name: "summary does not expire because of quantile addtime",
@@ -570,7 +570,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_SUMMARY.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label: []*dto.LabelPair{},
+							Label: make([]*dto.LabelPair, 0),
 							Summary: &dto.Summary{
 								SampleSum:   proto.Float64(1),
 								SampleCount: proto.Uint64(1),
@@ -614,7 +614,7 @@ func TestCollectionExpire(t *testing.T) {
 					Type: dto.MetricType_UNTYPED.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:   []*dto.LabelPair{},
+							Label:   make([]*dto.LabelPair, 0),
 							Untyped: &dto.Untyped{Value: proto.Float64(42.0)},
 						},
 					},
@@ -728,7 +728,7 @@ func TestExportTimestamps(t *testing.T) {
 					Type: dto.MetricType_HISTOGRAM.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:       []*dto.LabelPair{},
+							Label:       make([]*dto.LabelPair, 0),
 							TimestampMs: proto.Int64(time.Unix(20, 0).UnixNano() / int64(time.Millisecond)),
 							Histogram: &dto.Histogram{
 								SampleCount: proto.Uint64(4),
@@ -810,7 +810,7 @@ func TestExportTimestamps(t *testing.T) {
 					Type: dto.MetricType_SUMMARY.Enum(),
 					Metric: []*dto.Metric{
 						{
-							Label:       []*dto.LabelPair{},
+							Label:       make([]*dto.LabelPair, 0),
 							TimestampMs: proto.Int64(time.Unix(20, 0).UnixNano() / int64(time.Millisecond)),
 							Summary: &dto.Summary{
 								SampleCount: proto.Uint64(2),