Enable same linters as the Prometheus repo itself (#1056)

* Add gofumpt to github workflow & fix all files for it

Signed-off-by: sazary <soroosh@azary.ir>

* Add goimports to golangci & fix it's issues

Signed-off-by: sazary <soroosh@azary.ir>

* Add revive to golangci & fix it's issues

Signed-off-by: sazary <soroosh@azary.ir>

* Add errcheck & misspell to golangci and fix their issues

Signed-off-by: sazary <soroosh@azary.ir>

* Add govet & gosimple to golangci and fix their issues

Signed-off-by: sazary <soroosh@azary.ir>

* Enable all default linters of golangci

Signed-off-by: sazary <soroosh@azary.ir>

.github/workflows/golangci-lint.yml

@@ -1,3 +1,4 @@
+---
 name: golangci-lint
 on:
   push:

.golangci.yml

@@ -1,5 +1,31 @@
-# Run only staticcheck for now. Additional linters will be enabled one-by-one.
+---
+
+run:
+  deadline: 5m
+
+output:
+  sort-results: true
+
 linters:
   enable:
-  - staticcheck
+    - gofumpt
-  disable-all: true
+    - goimports
+    - revive
+    - misspell
+
+issues:
+  max-same-issues: 0
+  exclude-rules:
+    - path: _test.go
+      linters:
+        - errcheck
+        - govet
+        - structcheck
+
+linters-settings:
+  errcheck:
+    exclude: scripts/errcheck_excludes.txt
+  goimports:
+    local-prefixes: github.com/prometheus/client_golang
+  gofumpt:
+    extra-rules: true

api/client_test.go

@@ -134,7 +134,6 @@ func BenchmarkClient(b *testing.B) {
 
 	for _, sizeKB := range []int{4, 50, 1000, 2000} {
 		b.Run(fmt.Sprintf("%dKB", sizeKB), func(b *testing.B) {
-
 			testServer := httptest.NewServer(serveSpaces{sizeKB})
 			defer testServer.Close()
 

api/prometheus/v1/api.go

@@ -109,7 +109,6 @@ func marshalPointJSON(ptr unsafe.Pointer, stream *json.Stream) {
 
 	stream.WriteRaw(`"`)
 	stream.WriteArrayEnd()
-
 }
 
 func marshalPointJSONIsEmpty(ptr unsafe.Pointer) bool {
@@ -230,25 +229,25 @@ type API interface {
 	// Config returns the current Prometheus configuration.
 	Config(ctx context.Context) (ConfigResult, error)
 	// DeleteSeries deletes data for a selection of series in a time range.
-	DeleteSeries(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) error
+	DeleteSeries(ctx context.Context, matches []string, startTime, endTime time.Time) error
 	// Flags returns the flag values that Prometheus was launched with.
 	Flags(ctx context.Context) (FlagsResult, error)
 	// LabelNames returns the unique label names present in the block in sorted order by given time range and matchers.
-	LabelNames(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]string, Warnings, error)
+	LabelNames(ctx context.Context, matches []string, startTime, endTime time.Time) ([]string, Warnings, error)
 	// LabelValues performs a query for the values of the given label, time range and matchers.
-	LabelValues(ctx context.Context, label string, matches []string, startTime time.Time, endTime time.Time) (model.LabelValues, Warnings, error)
+	LabelValues(ctx context.Context, label string, matches []string, startTime, endTime time.Time) (model.LabelValues, Warnings, error)
 	// Query performs a query for the given time.
 	Query(ctx context.Context, query string, ts time.Time, opts ...Option) (model.Value, Warnings, error)
 	// QueryRange performs a query for the given range.
 	QueryRange(ctx context.Context, query string, r Range, opts ...Option) (model.Value, Warnings, error)
 	// QueryExemplars performs a query for exemplars by the given query and time range.
-	QueryExemplars(ctx context.Context, query string, startTime time.Time, endTime time.Time) ([]ExemplarQueryResult, error)
+	QueryExemplars(ctx context.Context, query string, startTime, endTime time.Time) ([]ExemplarQueryResult, error)
 	// Buildinfo returns various build information properties about the Prometheus server
 	Buildinfo(ctx context.Context) (BuildinfoResult, error)
 	// Runtimeinfo returns the various runtime information properties about the Prometheus server.
 	Runtimeinfo(ctx context.Context) (RuntimeinfoResult, error)
 	// Series finds series by label matchers.
-	Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, Warnings, error)
+	Series(ctx context.Context, matches []string, startTime, endTime time.Time) ([]model.LabelSet, Warnings, error)
 	// Snapshot creates a snapshot of all current data into snapshots/<datetime>-<rand>
 	// under the TSDB's data directory and returns the directory as response.
 	Snapshot(ctx context.Context, skipHead bool) (SnapshotResult, error)
@@ -257,9 +256,9 @@ type API interface {
 	// Targets returns an overview of the current state of the Prometheus target discovery.
 	Targets(ctx context.Context) (TargetsResult, error)
 	// TargetsMetadata returns metadata about metrics currently scraped by the target.
-	TargetsMetadata(ctx context.Context, matchTarget string, metric string, limit string) ([]MetricMetadata, error)
+	TargetsMetadata(ctx context.Context, matchTarget, metric, limit string) ([]MetricMetadata, error)
 	// Metadata returns metadata about metrics currently scraped by the metric name.
-	Metadata(ctx context.Context, metric string, limit string) (map[string][]Metadata, error)
+	Metadata(ctx context.Context, metric, limit string) (map[string][]Metadata, error)
 	// TSDB returns the cardinality statistics.
 	TSDB(ctx context.Context) (TSDBResult, error)
 	// WalReplay returns the current replay status of the wal.
@@ -699,7 +698,7 @@ func (h *httpAPI) Config(ctx context.Context) (ConfigResult, error) {
 	return res, json.Unmarshal(body, &res)
 }
 
-func (h *httpAPI) DeleteSeries(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) error {
+func (h *httpAPI) DeleteSeries(ctx context.Context, matches []string, startTime, endTime time.Time) error {
 	u := h.client.URL(epDeleteSeries, nil)
 	q := u.Query()
 
@@ -772,7 +771,7 @@ func (h *httpAPI) Runtimeinfo(ctx context.Context) (RuntimeinfoResult, error) {
 	return res, json.Unmarshal(body, &res)
 }
 
-func (h *httpAPI) LabelNames(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]string, Warnings, error) {
+func (h *httpAPI) LabelNames(ctx context.Context, matches []string, startTime, endTime time.Time) ([]string, Warnings, error) {
 	u := h.client.URL(epLabels, nil)
 	q := u.Query()
 	q.Set("start", formatTime(startTime))
@@ -795,7 +794,7 @@ func (h *httpAPI) LabelNames(ctx context.Context, matches []string, startTime ti
 	return labelNames, w, json.Unmarshal(body, &labelNames)
 }
 
-func (h *httpAPI) LabelValues(ctx context.Context, label string, matches []string, startTime time.Time, endTime time.Time) (model.LabelValues, Warnings, error) {
+func (h *httpAPI) LabelValues(ctx context.Context, label string, matches []string, startTime, endTime time.Time) (model.LabelValues, Warnings, error) {
 	u := h.client.URL(epLabelValues, map[string]string{"name": label})
 	q := u.Query()
 	q.Set("start", formatTime(startTime))
@@ -833,7 +832,6 @@ func WithTimeout(timeout time.Duration) Option {
 }
 
 func (h *httpAPI) Query(ctx context.Context, query string, ts time.Time, opts ...Option) (model.Value, Warnings, error) {
-
 	u := h.client.URL(epQuery, nil)
 	q := u.Query()
 
@@ -890,7 +888,7 @@ func (h *httpAPI) QueryRange(ctx context.Context, query string, r Range, opts ..
 	return model.Value(qres.v), warnings, json.Unmarshal(body, &qres)
 }
 
-func (h *httpAPI) Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, Warnings, error) {
+func (h *httpAPI) Series(ctx context.Context, matches []string, startTime, endTime time.Time) ([]model.LabelSet, Warnings, error) {
 	u := h.client.URL(epSeries, nil)
 	q := u.Query()
 
@@ -973,7 +971,7 @@ func (h *httpAPI) Targets(ctx context.Context) (TargetsResult, error) {
 	return res, json.Unmarshal(body, &res)
 }
 
-func (h *httpAPI) TargetsMetadata(ctx context.Context, matchTarget string, metric string, limit string) ([]MetricMetadata, error) {
+func (h *httpAPI) TargetsMetadata(ctx context.Context, matchTarget, metric, limit string) ([]MetricMetadata, error) {
 	u := h.client.URL(epTargetsMetadata, nil)
 	q := u.Query()
 
@@ -997,7 +995,7 @@ func (h *httpAPI) TargetsMetadata(ctx context.Context, matchTarget string, metri
 	return res, json.Unmarshal(body, &res)
 }
 
-func (h *httpAPI) Metadata(ctx context.Context, metric string, limit string) (map[string][]Metadata, error) {
+func (h *httpAPI) Metadata(ctx context.Context, metric, limit string) (map[string][]Metadata, error) {
 	u := h.client.URL(epMetadata, nil)
 	q := u.Query()
 
@@ -1054,7 +1052,7 @@ func (h *httpAPI) WalReplay(ctx context.Context) (WalReplayStatus, error) {
 	return res, json.Unmarshal(body, &res)
 }
 
-func (h *httpAPI) QueryExemplars(ctx context.Context, query string, startTime time.Time, endTime time.Time) ([]ExemplarQueryResult, error) {
+func (h *httpAPI) QueryExemplars(ctx context.Context, query string, startTime, endTime time.Time) ([]ExemplarQueryResult, error) {
 	u := h.client.URL(epQueryExemplars, nil)
 	q := u.Query()
 
@@ -1162,7 +1160,6 @@ func (h *apiClientImpl) Do(ctx context.Context, req *http.Request) (*http.Respon
 	}
 
 	return resp, []byte(result.Data), result.Warnings, err
-
 }
 
 // DoGetFallback will attempt to do the request as-is, and on a 405 or 501 it

api/prometheus/v1/api_test.go

@@ -65,7 +65,6 @@ func (c *apiTestClient) URL(ep string, args map[string]string) *url.URL {
 }
 
 func (c *apiTestClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, Warnings, error) {
-
 	test := c.curTest
 
 	if req.URL.Path != test.reqPath {
@@ -101,7 +100,6 @@ func (c *apiTestClient) DoGetFallback(ctx context.Context, u *url.URL, args url.
 }
 
 func TestAPIs(t *testing.T) {
-
 	testTime := time.Now()
 
 	tc := &apiTestClient{
@@ -131,7 +129,7 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
-	doDeleteSeries := func(matcher string, startTime time.Time, endTime time.Time) func() (interface{}, Warnings, error) {
+	doDeleteSeries := func(matcher string, startTime, endTime time.Time) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
 			return nil, nil, promAPI.DeleteSeries(context.Background(), []string{matcher}, startTime, endTime)
 		}
@@ -182,7 +180,7 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
-	doSeries := func(matcher string, startTime time.Time, endTime time.Time) func() (interface{}, Warnings, error) {
+	doSeries := func(matcher string, startTime, endTime time.Time) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
 			return promAPI.Series(context.Background(), []string{matcher}, startTime, endTime)
 		}
@@ -209,14 +207,14 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
-	doTargetsMetadata := func(matchTarget string, metric string, limit string) func() (interface{}, Warnings, error) {
+	doTargetsMetadata := func(matchTarget, metric, limit string) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
 			v, err := promAPI.TargetsMetadata(context.Background(), matchTarget, metric, limit)
 			return v, nil, err
 		}
 	}
 
-	doMetadata := func(metric string, limit string) func() (interface{}, Warnings, error) {
+	doMetadata := func(metric, limit string) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
 			v, err := promAPI.Metadata(context.Background(), metric, limit)
 			return v, nil, err
@@ -237,7 +235,7 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
-	doQueryExemplars := func(query string, startTime time.Time, endTime time.Time) func() (interface{}, Warnings, error) {
+	doQueryExemplars := func(query string, startTime, endTime time.Time) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
 			v, err := promAPI.QueryExemplars(context.Background(), query, startTime, endTime)
 			return v, nil, err
@@ -471,7 +469,8 @@ func TestAPIs(t *testing.T) {
 				{
 					"__name__": "up",
 					"job":      "prometheus",
-					"instance": "localhost:9090"},
+					"instance": "localhost:9090",
+				},
 			},
 			reqMethod: "GET",
 			reqPath:   "/api/v1/series",
@@ -495,7 +494,8 @@ func TestAPIs(t *testing.T) {
 				{
 					"__name__": "up",
 					"job":      "prometheus",
-					"instance": "localhost:9090"},
+					"instance": "localhost:9090",
+				},
 			},
 			inWarnings: []string{"a"},
 			reqMethod:  "GET",
@@ -586,7 +586,8 @@ func TestAPIs(t *testing.T) {
 				{
 					"__name__": "up",
 					"job":      "prometheus",
-					"instance": "localhost:9090"},
+					"instance": "localhost:9090",
+				},
 			},
 			reqMethod: "POST",
 			reqPath:   "/api/v1/admin/tsdb/delete_series",
@@ -1115,7 +1116,7 @@ func TestAPIs(t *testing.T) {
 				"limit":  []string{"1"},
 			},
 			res: map[string][]Metadata{
-				"go_goroutines": []Metadata{
+				"go_goroutines": {
 					{
 						Type: "gauge",
 						Help: "Number of goroutines that currently exist.",
@@ -1523,7 +1524,6 @@ func TestAPIClientDo(t *testing.T) {
 
 	for i, test := range tests {
 		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
-
 			tc.ch <- test
 
 			_, body, warnings, err := client.Do(context.Background(), tc.req)
@@ -1564,7 +1564,6 @@ func TestAPIClientDo(t *testing.T) {
 				t.Fatalf("expected body :%v, but got:%v", test.expectedBody, string(body))
 			}
 		})
-
 	}
 }
 

api/prometheus/v1/example_test.go

@@ -22,9 +22,10 @@ import (
 	"os"
 	"time"
 
+	"github.com/prometheus/common/config"
+
 	"github.com/prometheus/client_golang/api"
 	v1 "github.com/prometheus/client_golang/api/prometheus/v1"
-	"github.com/prometheus/common/config"
 )
 
 func ExampleAPI_query() {

prometheus/collector_test.go

@@ -30,7 +30,6 @@ func (c collectorDescribedByCollect) Describe(ch chan<- *Desc) {
 }
 
 func TestDescribeByCollect(t *testing.T) {
-
 	goodCollector := collectorDescribedByCollect{
 		cnt: NewCounter(CounterOpts{Name: "c1", Help: "help c1"}),
 		gge: NewGauge(GaugeOpts{Name: "g1", Help: "help g1"}),

prometheus/collectors/go_collector_latest.go

@@ -72,7 +72,8 @@ const (
 //
 // The current default is GoRuntimeMemStatsCollection, so the compatibility mode with
 // client_golang pre v1.12 (move to runtime/metrics).
-func WithGoCollections(flags GoCollectionOption) goOption {
+//nolint:staticcheck // Ignore SA1019 until v2.
+func WithGoCollections(flags GoCollectionOption) func(options *prometheus.GoCollectorOptions) {
 	return func(o *goOptions) {
 		o.EnabledCollections = uint32(flags)
 	}

prometheus/counter_test.go

@@ -231,7 +231,7 @@ func TestCounterExemplar(t *testing.T) {
 	}
 	expectedExemplar := &dto.Exemplar{
 		Label: []*dto.LabelPair{
-			&dto.LabelPair{Name: proto.String("foo"), Value: proto.String("bar")},
+			{Name: proto.String("foo"), Value: proto.String("bar")},
 		},
 		Value:     proto.Float64(42),
 		Timestamp: ts,

prometheus/desc.go

@@ -20,6 +20,7 @@ import (
 	"strings"
 
 	"github.com/cespare/xxhash/v2"
+
 	"github.com/prometheus/client_golang/prometheus/internal"
 
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.

prometheus/example_metricvec_test.go

@@ -108,7 +108,6 @@ func (v *InfoVec) MustCurryWith(labels prometheus.Labels) *InfoVec {
 }
 
 func ExampleMetricVec() {
-
 	infoVec := NewInfoVec(
 		"library_version_info",
 		"Versions of the libraries used in this binary.",

prometheus/example_timer_complex_test.go

@@ -19,27 +19,25 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-var (
+// apiRequestDuration tracks the duration separate for each HTTP status
-	// apiRequestDuration tracks the duration separate for each HTTP status
+// class (1xx, 2xx, ...). This creates a fair amount of time series on
-	// class (1xx, 2xx, ...). This creates a fair amount of time series on
+// the Prometheus server. Usually, you would track the duration of
-	// the Prometheus server. Usually, you would track the duration of
+// serving HTTP request without partitioning by outcome. Do something
-	// serving HTTP request without partitioning by outcome. Do something
+// like this only if needed. Also note how only status classes are
-	// like this only if needed. Also note how only status classes are
+// tracked, not every single status code. The latter would create an
-	// tracked, not every single status code. The latter would create an
+// even larger amount of time series. Request counters partitioned by
-	// even larger amount of time series. Request counters partitioned by
+// status code are usually OK as each counter only creates one time
-	// status code are usually OK as each counter only creates one time
+// series. Histograms are way more expensive, so partition with care and
-	// series. Histograms are way more expensive, so partition with care and
+// only where you really need separate latency tracking. Partitioning by
-	// only where you really need separate latency tracking. Partitioning by
+// status class is only an example. In concrete cases, other partitions
-	// status class is only an example. In concrete cases, other partitions
+// might make more sense.
-	// might make more sense.
+var apiRequestDuration = prometheus.NewHistogramVec(
-	apiRequestDuration = prometheus.NewHistogramVec(
+	prometheus.HistogramOpts{
-		prometheus.HistogramOpts{
+		Name:    "api_request_duration_seconds",
-			Name:    "api_request_duration_seconds",
+		Help:    "Histogram for the request duration of the public API, partitioned by status class.",
-			Help:    "Histogram for the request duration of the public API, partitioned by status class.",
+		Buckets: prometheus.ExponentialBuckets(0.1, 1.5, 5),
-			Buckets: prometheus.ExponentialBuckets(0.1, 1.5, 5),
+	},
-		},
+	[]string{"status_class"},
-		[]string{"status_class"},
-	)
 )
 
 func handler(w http.ResponseWriter, r *http.Request) {

prometheus/example_timer_gauge_test.go

@@ -19,17 +19,15 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-var (
+// If a function is called rarely (i.e. not more often than scrapes
-	// If a function is called rarely (i.e. not more often than scrapes
+// happen) or ideally only once (like in a batch job), it can make sense
-	// happen) or ideally only once (like in a batch job), it can make sense
+// to use a Gauge for timing the function call. For timing a batch job
-	// to use a Gauge for timing the function call. For timing a batch job
+// and pushing the result to a Pushgateway, see also the comprehensive
-	// and pushing the result to a Pushgateway, see also the comprehensive
+// example in the push package.
-	// example in the push package.
+var funcDuration = prometheus.NewGauge(prometheus.GaugeOpts{
-	funcDuration = prometheus.NewGauge(prometheus.GaugeOpts{
+	Name: "example_function_duration_seconds",
-		Name: "example_function_duration_seconds",
+	Help: "Duration of the last call of an example function.",
-		Help: "Duration of the last call of an example function.",
+})
-	})
-)
 
 func run() error {
 	// The Set method of the Gauge is used to observe the duration.

prometheus/example_timer_test.go

@@ -20,13 +20,11 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-var (
+var requestDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
-	requestDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
+	Name:    "example_request_duration_seconds",
-		Name:    "example_request_duration_seconds",
+	Help:    "Histogram for the runtime of a simple example function.",
-		Help:    "Histogram for the runtime of a simple example function.",
+	Buckets: prometheus.LinearBuckets(0.01, 0.01, 10),
-		Buckets: prometheus.LinearBuckets(0.01, 0.01, 10),
+})
-	})
-)
 
 func ExampleTimer() {
 	// timer times this example function. It uses a Histogram, but a Summary

prometheus/go_collector_latest.go

@@ -54,7 +54,8 @@ const (
 )
 
 // runtime/metrics names required for runtimeMemStats like logic.
-var rmForMemStats = []string{goGCHeapTinyAllocsObjects,
+var rmForMemStats = []string{
+	goGCHeapTinyAllocsObjects,
 	goGCHeapAllocsObjects,
 	goGCHeapFreesObjects,
 	goGCHeapAllocsBytes,

prometheus/graphite/bridge.go

@@ -240,9 +240,8 @@ func writeMetric(buf *bufio.Writer, m model.Metric, useTags bool) error {
 		}
 		if useTags {
 			return writeTags(buf, m)
-		} else {
-			return writeLabels(buf, m, numLabels)
 		}
+		return writeLabels(buf, m, numLabels)
 	}
 	return nil
 }

prometheus/histogram_test.go

@@ -354,7 +354,8 @@ func TestBuckets(t *testing.T) {
 	}
 
 	got = ExponentialBucketsRange(1, 100, 10)
-	want = []float64{1.0, 1.6681005372000588, 2.782559402207125,
+	want = []float64{
+		1.0, 1.6681005372000588, 2.782559402207125,
 		4.641588833612779, 7.742636826811273, 12.915496650148842,
 		21.544346900318846, 35.93813663804629, 59.94842503189414,
 		100.00000000000007,

prometheus/internal/difflib.go

@@ -106,8 +106,8 @@ func NewMatcher(a, b []string) *SequenceMatcher {
 }
 
 func NewMatcherWithJunk(a, b []string, autoJunk bool,
-	isJunk func(string) bool) *SequenceMatcher {
+	isJunk func(string) bool,
-
+) *SequenceMatcher {
 	m := SequenceMatcher{IsJunk: isJunk, autoJunk: autoJunk}
 	m.SetSeqs(a, b)
 	return &m
@@ -163,12 +163,12 @@ func (m *SequenceMatcher) chainB() {
 	m.bJunk = map[string]struct{}{}
 	if m.IsJunk != nil {
 		junk := m.bJunk
-		for s, _ := range b2j {
+		for s := range b2j {
 			if m.IsJunk(s) {
 				junk[s] = struct{}{}
 			}
 		}
-		for s, _ := range junk {
+		for s := range junk {
 			delete(b2j, s)
 		}
 	}
@@ -183,7 +183,7 @@ func (m *SequenceMatcher) chainB() {
 				popular[s] = struct{}{}
 			}
 		}
-		for s, _ := range popular {
+		for s := range popular {
 			delete(b2j, s)
 		}
 	}
@@ -270,7 +270,7 @@ func (m *SequenceMatcher) findLongestMatch(alo, ahi, blo, bhi int) Match {
 	for besti+bestsize < ahi && bestj+bestsize < bhi &&
 		!m.isBJunk(m.b[bestj+bestsize]) &&
 		m.a[besti+bestsize] == m.b[bestj+bestsize] {
-		bestsize += 1
+		bestsize++
 	}
 
 	// Now that we have a wholly interesting match (albeit possibly
@@ -287,7 +287,7 @@ func (m *SequenceMatcher) findLongestMatch(alo, ahi, blo, bhi int) Match {
 	for besti+bestsize < ahi && bestj+bestsize < bhi &&
 		m.isBJunk(m.b[bestj+bestsize]) &&
 		m.a[besti+bestsize] == m.b[bestj+bestsize] {
-		bestsize += 1
+		bestsize++
 	}
 
 	return Match{A: besti, B: bestj, Size: bestsize}
@@ -439,8 +439,10 @@ func (m *SequenceMatcher) GetGroupedOpCodes(n int) [][]OpCode {
 		// End the current group and start a new one whenever
 		// there is a large range with no changes.
 		if c.Tag == 'e' && i2-i1 > nn {
-			group = append(group, OpCode{c.Tag, i1, min(i2, i1+n),
+			group = append(group, OpCode{
-				j1, min(j2, j1+n)})
+				c.Tag, i1, min(i2, i1+n),
+				j1, min(j2, j1+n),
+			})
 			groups = append(groups, group)
 			group = []OpCode{}
 			i1, j1 = max(i1, i2-n), max(j1, j2-n)
@@ -498,7 +500,7 @@ func (m *SequenceMatcher) QuickRatio() float64 {
 		}
 		avail[s] = n - 1
 		if n > 0 {
-			matches += 1
+			matches++
 		}
 	}
 	return calculateRatio(matches, len(m.a)+len(m.b))
@@ -522,7 +524,7 @@ func formatRangeUnified(start, stop int) string {
 		return fmt.Sprintf("%d", beginning)
 	}
 	if length == 0 {
-		beginning -= 1 // empty ranges begin at line just before the range
+		beginning-- // empty ranges begin at line just before the range
 	}
 	return fmt.Sprintf("%d,%d", beginning, length)
 }
@@ -637,7 +639,7 @@ func WriteUnifiedDiff(writer io.Writer, diff UnifiedDiff) error {
 func GetUnifiedDiffString(diff UnifiedDiff) (string, error) {
 	w := &bytes.Buffer{}
 	err := WriteUnifiedDiff(w, diff)
-	return string(w.Bytes()), err
+	return w.String(), err
 }
 
 // Split a string on "\n" while preserving them. The output can be used

prometheus/internal/difflib_test.go

@@ -58,7 +58,7 @@ func TestGetOptCodes(t *testing.T) {
 		fmt.Fprintf(w, "%s a[%d:%d], (%s) b[%d:%d] (%s)\n", string(op.Tag),
 			op.I1, op.I2, a[op.I1:op.I2], op.J1, op.J2, b[op.J1:op.J2])
 	}
-	result := string(w.Bytes())
+	result := w.String()
 	expected := `d a[0:1], (q) b[0:0] ()
 e a[1:3], (ab) b[0:2] (ab)
 r a[3:4], (x) b[2:3] (y)
@@ -93,7 +93,7 @@ func TestGroupedOpCodes(t *testing.T) {
 				op.I1, op.I2, op.J1, op.J2)
 		}
 	}
-	result := string(w.Bytes())
+	result := w.String()
 	expected := `group
   e, 5, 8, 5, 8
   i, 8, 8, 8, 9
@@ -185,14 +185,14 @@ func TestWithAsciiBJunk(t *testing.T) {
 
 	sm = NewMatcherWithJunk(splitChars(rep("a", 40)+rep("b", 40)),
 		splitChars(rep("a", 44)+rep("b", 40)+rep(" ", 20)), false, isJunk)
-	assertEqual(t, sm.bJunk, map[string]struct{}{" ": struct{}{}})
+	assertEqual(t, sm.bJunk, map[string]struct{}{" ": {}})
 
 	isJunk = func(s string) bool {
 		return s == " " || s == "b"
 	}
 	sm = NewMatcherWithJunk(splitChars(rep("a", 40)+rep("b", 40)),
 		splitChars(rep("a", 44)+rep("b", 40)+rep(" ", 20)), false, isJunk)
-	assertEqual(t, sm.bJunk, map[string]struct{}{" ": struct{}{}, "b": struct{}{}})
+	assertEqual(t, sm.bJunk, map[string]struct{}{" ": {}, "b": {}})
 }
 
 func TestSFBugsRatioForNullSeqn(t *testing.T) {

prometheus/metric_test.go

@@ -75,5 +75,4 @@ func TestWithExemplarsMetric(t *testing.T) {
 			}
 		}
 	})
-
 }

prometheus/promhttp/delegator.go

@@ -76,16 +76,19 @@ func (r *responseWriterDelegator) Write(b []byte) (int, error) {
 	return n, err
 }
 
-type closeNotifierDelegator struct{ *responseWriterDelegator }
+type (
-type flusherDelegator struct{ *responseWriterDelegator }
+	closeNotifierDelegator struct{ *responseWriterDelegator }
-type hijackerDelegator struct{ *responseWriterDelegator }
+	flusherDelegator       struct{ *responseWriterDelegator }
-type readerFromDelegator struct{ *responseWriterDelegator }
+	hijackerDelegator      struct{ *responseWriterDelegator }
-type pusherDelegator struct{ *responseWriterDelegator }
+	readerFromDelegator    struct{ *responseWriterDelegator }
+	pusherDelegator        struct{ *responseWriterDelegator }
+)
 
 func (d closeNotifierDelegator) CloseNotify() <-chan bool {
 	//nolint:staticcheck // Ignore SA1019. http.CloseNotifier is deprecated but we keep it here to not break existing users.
 	return d.ResponseWriter.(http.CloseNotifier).CloseNotify()
 }
+
 func (d flusherDelegator) Flush() {
 	// If applicable, call WriteHeader here so that observeWriteHeader is
 	// handled appropriately.
@@ -94,9 +97,11 @@ func (d flusherDelegator) Flush() {
 	}
 	d.ResponseWriter.(http.Flusher).Flush()
 }
+
 func (d hijackerDelegator) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	return d.ResponseWriter.(http.Hijacker).Hijack()
 }
+
 func (d readerFromDelegator) ReadFrom(re io.Reader) (int64, error) {
 	// If applicable, call WriteHeader here so that observeWriteHeader is
 	// handled appropriately.
@@ -107,6 +112,7 @@ func (d readerFromDelegator) ReadFrom(re io.Reader) (int64, error) {
 	d.written += n
 	return n, err
 }
+
 func (d pusherDelegator) Push(target string, opts *http.PushOptions) error {
 	return d.ResponseWriter.(http.Pusher).Push(target, opts)
 }
@@ -261,7 +267,7 @@ func init() {
 			http.Flusher
 		}{d, pusherDelegator{d}, hijackerDelegator{d}, flusherDelegator{d}}
 	}
-	pickDelegator[pusher+hijacker+flusher+closeNotifier] = func(d *responseWriterDelegator) delegator { //23
+	pickDelegator[pusher+hijacker+flusher+closeNotifier] = func(d *responseWriterDelegator) delegator { // 23
 		return struct {
 			*responseWriterDelegator
 			http.Pusher

prometheus/promhttp/http_test.go

@@ -24,8 +24,9 @@ import (
 	"testing"
 	"time"
 
-	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 type errorCollector struct{}

prometheus/promhttp/instrument_server.go

@@ -246,7 +246,7 @@ func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler
 // Collector does not have a Desc or has more than one Desc or its Desc is
 // invalid. It also panics if the Collector has any non-const, non-curried
 // labels that are not named "code" or "method".
-func checkLabels(c prometheus.Collector) (code bool, method bool) {
+func checkLabels(c prometheus.Collector) (code, method bool) {
 	// TODO(beorn7): Remove this hacky way to check for instance labels
 	// once Descriptors can have their dimensionality queried.
 	var (

prometheus/promhttp/instrument_server_test.go

@@ -279,7 +279,7 @@ func TestLabels(t *testing.T) {
 			ok:         false,
 		},
 	}
-	checkLabels := func(labels []string) (gotCode bool, gotMethod bool) {
+	checkLabels := func(labels []string) (gotCode, gotMethod bool) {
 		for _, label := range labels {
 			switch label {
 			case "code":

prometheus/promhttp/option_test.go

@@ -50,11 +50,10 @@ func ExampleInstrumentHandlerWithExtraMethods() {
 
 	// Instrument the handlers with all the metrics, injecting the "handler"
 	// label by currying.
-	pullChain :=
+	pullChain := InstrumentHandlerDuration(duration.MustCurryWith(prometheus.Labels{"handler": "pull"}),
-		InstrumentHandlerDuration(duration.MustCurryWith(prometheus.Labels{"handler": "pull"}),
+		InstrumentHandlerCounter(counter, pullHandler, opts),
-			InstrumentHandlerCounter(counter, pullHandler, opts),
+		opts,
-			opts,
+	)
-		)
 
 	http.Handle("/metrics", Handler())
 	http.Handle("/pull", pullChain)

prometheus/push/push.go

@@ -98,9 +98,7 @@ func New(url, job string) *Pusher {
 	if !strings.Contains(url, "://") {
 		url = "http://" + url
 	}
-	if strings.HasSuffix(url, "/") {
+	url = strings.TrimSuffix(url, "/")
-		url = url[:len(url)-1]
-	}
 
 	return &Pusher{
 		error:      err,
@@ -273,7 +271,11 @@ func (p *Pusher) push(ctx context.Context, method string) error {
 				}
 			}
 		}
-		enc.Encode(mf)
+		if err := enc.Encode(mf); err != nil {
+			return fmt.Errorf(
+				"failed to encode metric familty %s, error is %w",
+				mf.GetName(), err)
+		}
 	}
 	req, err := http.NewRequestWithContext(ctx, method, p.fullURL(), buf)
 	if err != nil {

prometheus/push/push_test.go

@@ -26,7 +26,6 @@ import (
 )
 
 func TestPush(t *testing.T) {
-
 	var (
 		lastMethod string
 		lastBody   []byte

prometheus/registry.go

@@ -582,7 +582,7 @@ func WriteToTextfile(filename string, g Gatherer) error {
 		return err
 	}
 
-	if err := os.Chmod(tmp.Name(), 0644); err != nil {
+	if err := os.Chmod(tmp.Name(), 0o644); err != nil {
 		return err
 	}
 	return os.Rename(tmp.Name(), filename)

prometheus/registry_test.go

@@ -349,7 +349,7 @@ collected metric "broken_metric" { label:<name:"foo" value:"bar" > label:<name:"
 		body    []byte
 	}
 
-	var scenarios = []struct {
+	scenarios := []struct {
 		headers    map[string]string
 		out        output
 		collector  prometheus.Collector
@@ -1118,7 +1118,6 @@ func (m *collidingCollector) Collect(metric chan<- prometheus.Metric) {
 // TestAlreadyRegistered will fail with the old, weaker hash function.  It is
 // taken from https://play.golang.org/p/HpV7YE6LI_4 , authored by @awilliams.
 func TestAlreadyRegisteredCollision(t *testing.T) {
-
 	reg := prometheus.NewRegistry()
 
 	for i := 0; i < 10000; i++ {

prometheus/testutil/promlint/promlint.go

@@ -283,7 +283,7 @@ func lintUnitAbbreviations(mf *dto.MetricFamily) []Problem {
 
 // metricUnits attempts to detect known unit types used as part of a metric name,
 // e.g. "foo_bytes_total" or "bar_baz_milligrams".
-func metricUnits(m string) (unit string, base string, ok bool) {
+func metricUnits(m string) (unit, base string, ok bool) {
 	ss := strings.Split(m, "_")
 
 	for unit, base := range units {

prometheus/testutil/promlint/promlint_test.go

@@ -330,7 +330,8 @@ thermometers_rankine 10
 				Metric: "thermometers_rankine",
 				Text:   `use base unit "celsius" instead of "rankine"`,
 			}},
-		}, {
+		},
+		{
 			name: "inches",
 			in: `
 # HELP x_inches Test metric.
@@ -341,7 +342,8 @@ x_inches 10
 				Metric: "x_inches",
 				Text:   `use base unit "meters" instead of "inches"`,
 			}},
-		}, {
+		},
+		{
 			name: "yards",
 			in: `
 # HELP x_yards Test metric.
@@ -352,7 +354,8 @@ x_yards 10
 				Metric: "x_yards",
 				Text:   `use base unit "meters" instead of "yards"`,
 			}},
-		}, {
+		},
+		{
 			name: "miles",
 			in: `
 # HELP x_miles Test metric.
@@ -363,7 +366,8 @@ x_miles 10
 				Metric: "x_miles",
 				Text:   `use base unit "meters" instead of "miles"`,
 			}},
-		}, {
+		},
+		{
 			name: "bits",
 			in: `
 # HELP x_bits Test metric.

prometheus/testutil/testutil.go

@@ -101,7 +101,9 @@ func ToFloat64(c prometheus.Collector) float64 {
 	}
 
 	pb := &dto.Metric{}
-	m.Write(pb)
+	if err := m.Write(pb); err != nil {
+		panic(fmt.Errorf("error happened while collecting metrics: %w", err))
+	}
 	if pb.Gauge != nil {
 		return pb.Gauge.GetValue()
 	}
@@ -221,7 +223,7 @@ func compare(got, want []*dto.MetricFamily) error {
 
 // diff returns a diff of both values as long as both are of the same type and
 // are a struct, map, slice, array or string. Otherwise it returns an empty string.
-func diff(expected interface{}, actual interface{}) string {
+func diff(expected, actual interface{}) string {
 	if expected == nil || actual == nil {
 		return ""
 	}

prometheus/timer_test.go

@@ -148,5 +148,4 @@ func TestTimerByOutcome(t *testing.T) {
 	if want, got := uint64(2), m.GetHistogram().GetSampleCount(); want != got {
 		t.Errorf("want %d observations for 'bar' histogram, got %d", want, got)
 	}
-
 }

prometheus/value.go

@@ -21,9 +21,10 @@ import (
 
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/client_golang/prometheus/internal"
 	"google.golang.org/protobuf/types/known/timestamppb"
 
+	"github.com/prometheus/client_golang/prometheus/internal"
+
 	dto "github.com/prometheus/client_model/go"
 )
 

prometheus/vec.go

@@ -571,7 +571,7 @@ func findMetricWithLabels(
 	return len(metrics)
 }
 
-func matchLabelValues(values []string, lvs []string, curry []curriedLabelValue) bool {
+func matchLabelValues(values, lvs []string, curry []curriedLabelValue) bool {
 	if len(values) != len(lvs)+len(curry) {
 		return false
 	}

prometheus/vec_test.go

@@ -49,7 +49,7 @@ func testDelete(t *testing.T, vec *GaugeVec) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 
-	vec.With(Labels{"l1": "v1", "l2": "v2"}).(Gauge).Set(42)
+	vec.With(Labels{"l1": "v1", "l2": "v2"}).Set(42)
 	if got, want := vec.Delete(Labels{"l1": "v1", "l2": "v2"}), true; got != want {
 		t.Errorf("got %v, want %v", got, want)
 	}
@@ -57,7 +57,7 @@ func testDelete(t *testing.T, vec *GaugeVec) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 
-	vec.With(Labels{"l1": "v1", "l2": "v2"}).(Gauge).Set(42)
+	vec.With(Labels{"l1": "v1", "l2": "v2"}).Set(42)
 	if got, want := vec.Delete(Labels{"l2": "v2", "l1": "v1"}), true; got != want {
 		t.Errorf("got %v, want %v", got, want)
 	}
@@ -65,7 +65,7 @@ func testDelete(t *testing.T, vec *GaugeVec) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 
-	vec.With(Labels{"l1": "v1", "l2": "v2"}).(Gauge).Set(42)
+	vec.With(Labels{"l1": "v1", "l2": "v2"}).Set(42)
 	if got, want := vec.Delete(Labels{"l2": "v1", "l1": "v2"}), false; got != want {
 		t.Errorf("got %v, want %v", got, want)
 	}
@@ -103,8 +103,8 @@ func testDeleteLabelValues(t *testing.T, vec *GaugeVec) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 
-	vec.With(Labels{"l1": "v1", "l2": "v2"}).(Gauge).Set(42)
+	vec.With(Labels{"l1": "v1", "l2": "v2"}).Set(42)
-	vec.With(Labels{"l1": "v1", "l2": "v3"}).(Gauge).Set(42) // Add junk data for collision.
+	vec.With(Labels{"l1": "v1", "l2": "v3"}).Set(42) // Add junk data for collision.
 	if got, want := vec.DeleteLabelValues("v1", "v2"), true; got != want {
 		t.Errorf("got %v, want %v", got, want)
 	}
@@ -115,7 +115,7 @@ func testDeleteLabelValues(t *testing.T, vec *GaugeVec) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 
-	vec.With(Labels{"l1": "v1", "l2": "v2"}).(Gauge).Set(42)
+	vec.With(Labels{"l1": "v1", "l2": "v2"}).Set(42)
 	// Delete out of order.
 	if got, want := vec.DeleteLabelValues("v2", "v1"), false; got != want {
 		t.Errorf("got %v, want %v", got, want)
@@ -146,9 +146,9 @@ func TestDeletePartialMatch(t *testing.T) {
 	}
 
 	baseVec.With(Labels{"l1": "baseValue1", "l2": "baseValue2", "l3": "baseValue3"}).Inc()
-	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff1BaseValue2", "l3": "v3"}).(Gauge).Set(42)
+	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff1BaseValue2", "l3": "v3"}).Set(42)
-	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff2BaseValue2", "l3": "v3"}).(Gauge).Set(84)
+	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff2BaseValue2", "l3": "v3"}).Set(84)
-	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff3BaseValue2", "l3": "v3"}).(Gauge).Set(168)
+	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff3BaseValue2", "l3": "v3"}).Set(168)
 
 	curriedVec := baseVec.MustCurryWith(Labels{"l2": "curriedValue2"})
 	curriedVec.WithLabelValues("curriedValue1", "curriedValue3").Inc()
@@ -249,7 +249,7 @@ func testMetricVec(t *testing.T, vec *GaugeVec) {
 		vec.WithLabelValues(pair[0], pair[1]).Inc()
 
 		expected[[2]string{"v1", "v2"}]++
-		vec.WithLabelValues("v1", "v2").(Gauge).Inc()
+		vec.WithLabelValues("v1", "v2").Inc()
 	}
 
 	var total int
@@ -351,7 +351,6 @@ func TestCurryVecWithCollisions(t *testing.T) {
 }
 
 func testCurryVec(t *testing.T, vec *CounterVec) {
-
 	assertMetrics := func(t *testing.T) {
 		n := 0
 		for _, m := range vec.metricMap.metrics {
@@ -538,7 +537,6 @@ func testCurryVec(t *testing.T, vec *CounterVec) {
 		} else if err.Error() != `label name "three" is already curried` {
 			t.Error("currying returned unexpected error:", err)
 		}
-
 	})
 	t.Run("unknown label", func(t *testing.T) {
 		if _, err := vec.CurryWith(Labels{"foo": "bar"}); err == nil {

prometheus/wrap.go

@@ -20,8 +20,9 @@ import (
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
-	"github.com/prometheus/client_golang/prometheus/internal"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus/internal"
 )
 
 // WrapRegistererWith returns a Registerer wrapping the provided

prometheus/wrap_test.go

@@ -46,7 +46,6 @@ func toMetricFamilies(cs ...Collector) []*dto.MetricFamily {
 }
 
 func TestWrap(t *testing.T) {
-
 	simpleCnt := NewCounter(CounterOpts{
 		Name: "simpleCnt",
 		Help: "helpSimpleCnt",
@@ -319,7 +318,6 @@ func TestWrap(t *testing.T) {
 			}
 		})
 	}
-
 }
 
 func TestNil(t *testing.T) {

scripts/errcheck_excludes.txt

@@ -0,0 +1,5 @@
+// The following 2 methods always return nil as the error
+(*github.com/cespare/xxhash/v2.Digest).Write
+(*github.com/cespare/xxhash/v2.Digest).WriteString
+
+(*bufio.Writer).WriteRune