Merge pull request prometheus#14715 from prometheus/beorn7/lint

lint: Revamp our linting rules, mostly around doc comments

.golangci.yml

@@ -25,15 +25,34 @@ linters:
     - loggercheck
 
 issues:
+  max-issues-per-linter: 0
   max-same-issues: 0
+  # The default exclusions are too aggressive. For one, they
+  # essentially disable any linting on doc comments. We disable
+  # default exclusions here and add exclusions fitting our codebase
+  # further down.
+  exclude-use-default: false
   exclude-files:
     # Skip autogenerated files.
     - ^.*\.(pb|y)\.go$
   exclude-dirs:
-    # Copied it from a different source
+    # Copied it from a different source.
     - storage/remote/otlptranslator/prometheusremotewrite
     - storage/remote/otlptranslator/prometheus
   exclude-rules:
+    - linters:
+        - errcheck
+      # Taken from the default exclusions (that are otherwise disabled above).
+      text: Error return value of .((os\.)?std(out|err)\..*|.*Close|.*Flush|os\.Remove(All)?|.*print(f|ln)?|os\.(Un)?Setenv). is not checked
+    - linters:
+        - govet
+      # We use many Seek methods that do not follow the usual pattern.
+      text: "stdmethods: method Seek.* should have signature Seek"
+    - linters:
+        - revive
+      # We have stopped at some point to write doc comments on exported symbols.
+      # TODO(beorn7): Maybe we should enforce this again? There are ~500 offenders right now.
+      text: exported (.+) should have comment( \(or a comment on this block\))? or be unexported
     - linters:
         - gocritic
       text: "appendAssign"
@@ -94,15 +113,14 @@ linters-settings:
     errorf: false
   revive:
     # By default, revive will enable only the linting rules that are named in the configuration file.
-    # So, it's needed to explicitly set in configuration all required rules.
-    # The following configuration enables all the rules from the defaults.toml
-    # https://github.com/mgechev/revive/blob/master/defaults.toml
+    # So, it's needed to explicitly enable all required rules here.
     rules:
       # https://github.com/mgechev/revive/blob/master/RULES_DESCRIPTIONS.md
       - name: blank-imports
+      - name: comment-spacings
       - name: context-as-argument
         arguments:
-          # allow functions with test or bench signatures
+          # Allow functions with test or bench signatures.
           - allowTypesBefore: "*testing.T,testing.TB"
       - name: context-keys-type
       - name: dot-imports
@@ -118,6 +136,8 @@ linters-settings:
       - name: increment-decrement
       - name: indent-error-flow
       - name: package-comments
+        # TODO(beorn7): Currently, we have a lot of missing package doc comments. Maybe we should have them.
+        disabled: true
       - name: range
       - name: receiver-naming
       - name: redefines-builtin-id

cmd/promtool/main.go

@@ -471,7 +471,7 @@ func (ls lintConfig) lintDuplicateRules() bool {
 	return ls.all || ls.duplicateRules
 }
 
-// Check server status - healthy & ready.
+// CheckServerStatus - healthy & ready.
 func CheckServerStatus(serverURL *url.URL, checkEndpoint string, roundTripper http.RoundTripper) error {
 	if serverURL.Scheme == "" {
 		serverURL.Scheme = "http"

cmd/promtool/metrics.go

@@ -31,7 +31,7 @@ import (
 	"github.com/prometheus/prometheus/util/fmtutil"
 )
 
-// Push metrics to a prometheus remote write (for testing purpose only).
+// PushMetrics to a prometheus remote write (for testing purpose only).
 func PushMetrics(url *url.URL, roundTripper http.RoundTripper, headers map[string]string, timeout time.Duration, labels map[string]string, files ...string) int {
 	addressURL, err := url.Parse(url.String())
 	if err != nil {

discovery/discoverer_metrics_noop.go

@@ -13,7 +13,7 @@
 
 package discovery
 
-// Create a dummy metrics struct, because this SD doesn't have any metrics.
+// NoopDiscovererMetrics creates a dummy metrics struct, because this SD doesn't have any metrics.
 type NoopDiscovererMetrics struct{}
 
 var _ DiscovererMetrics = (*NoopDiscovererMetrics)(nil)

discovery/discovery.go

@@ -39,7 +39,7 @@ type Discoverer interface {
 	Run(ctx context.Context, up chan<- []*targetgroup.Group)
 }
 
-// Internal metrics of service discovery mechanisms.
+// DiscovererMetrics are internal metrics of service discovery mechanisms.
 type DiscovererMetrics interface {
 	Register() error
 	Unregister()
@@ -56,25 +56,26 @@ type DiscovererOptions struct {
 	HTTPClientOptions []config.HTTPClientOption
 }
 
-// Metrics used by the "refresh" package.
+// RefreshMetrics are used by the "refresh" package.
 // We define them here in the "discovery" package in order to avoid a cyclic dependency between
 // "discovery" and "refresh".
 type RefreshMetrics struct {
 	Failures prometheus.Counter
 	Duration prometheus.Observer
 }
 
-// Instantiate the metrics used by the "refresh" package.
+// RefreshMetricsInstantiator instantiates the metrics used by the "refresh" package.
 type RefreshMetricsInstantiator interface {
 	Instantiate(mech string) *RefreshMetrics
 }
 
-// An interface for registering, unregistering, and instantiating metrics for the "refresh" package.
-// Refresh metrics are registered and unregistered outside of the service discovery mechanism.
-// This is so that the same metrics can be reused across different service discovery mechanisms.
-// To manage refresh metrics inside the SD mechanism, we'd need to use const labels which are
-// specific to that SD. However, doing so would also expose too many unused metrics on
-// the Prometheus /metrics endpoint.
+// RefreshMetricsManager is an interface for registering, unregistering, and
+// instantiating metrics for the "refresh" package. Refresh metrics are
+// registered and unregistered outside of the service discovery mechanism. This
+// is so that the same metrics can be reused across different service discovery
+// mechanisms. To manage refresh metrics inside the SD mechanism, we'd need to
+// use const labels which are specific to that SD. However, doing so would also
+// expose too many unused metrics on the Prometheus /metrics endpoint.
 type RefreshMetricsManager interface {
 	DiscovererMetrics
 	RefreshMetricsInstantiator
@@ -145,7 +146,8 @@ func (c StaticConfig) NewDiscoverer(DiscovererOptions) (Discoverer, error) {
 	return staticDiscoverer(c), nil
 }
 
-// No metrics are needed for this service discovery mechanism.
+// NewDiscovererMetrics returns NoopDiscovererMetrics because no metrics are
+// needed for this service discovery mechanism.
 func (c StaticConfig) NewDiscovererMetrics(prometheus.Registerer, RefreshMetricsInstantiator) DiscovererMetrics {
 	return &NoopDiscovererMetrics{}
 }

discovery/manager.go

@@ -64,7 +64,7 @@ func (p *Provider) Config() interface{} {
 	return p.config
 }
 
-// Registers the metrics needed for SD mechanisms.
+// CreateAndRegisterSDMetrics registers the metrics needed for SD mechanisms.
 // Does not register the metrics for the Discovery Manager.
 // TODO(ptodev): Add ability to unregister the metrics?
 func CreateAndRegisterSDMetrics(reg prometheus.Registerer) (map[string]DiscovererMetrics, error) {

discovery/metrics_refresh.go

@@ -17,7 +17,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-// Metric vectors for the "refresh" package.
+// RefreshMetricsVecs are metric vectors for the "refresh" package.
 // We define them here in the "discovery" package in order to avoid a cyclic dependency between
 // "discovery" and "refresh".
 type RefreshMetricsVecs struct {

discovery/util.go

@@ -19,8 +19,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-// A utility to be used by implementations of discovery.Discoverer
-// which need to manage the lifetime of their metrics.
+// MetricRegisterer is used by implementations of discovery.Discoverer that need
+// to manage the lifetime of their metrics.
 type MetricRegisterer interface {
 	RegisterMetrics() error
 	UnregisterMetrics()
@@ -34,7 +34,7 @@ type metricRegistererImpl struct {
 
 var _ MetricRegisterer = &metricRegistererImpl{}
 
-// Creates an instance of a MetricRegisterer.
+// NewMetricRegisterer creates an instance of a MetricRegisterer.
 // Typically called inside the implementation of the NewDiscoverer() method.
 func NewMetricRegisterer(reg prometheus.Registerer, metrics []prometheus.Collector) MetricRegisterer {
 	return &metricRegistererImpl{

model/exemplar/exemplar.go

@@ -15,7 +15,9 @@ package exemplar
 
 import "github.com/prometheus/prometheus/model/labels"
 
-// The combined length of the label names and values of an Exemplar's LabelSet MUST NOT exceed 128 UTF-8 characters
+// ExemplarMaxLabelSetLength is defined by OpenMetrics: "The combined length of
+// the label names and values of an Exemplar's LabelSet MUST NOT exceed 128
+// UTF-8 characters."
 // https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#exemplars
 const ExemplarMaxLabelSetLength = 128
 
@@ -49,7 +51,7 @@ func (e Exemplar) Equals(e2 Exemplar) bool {
 	return e.Value == e2.Value
 }
 
-// Sort first by timestamp, then value, then labels.
+// Compare first timestamps, then values, then labels.
 func Compare(a, b Exemplar) int {
 	if a.Ts < b.Ts {
 		return -1

model/labels/labels.go

@@ -315,7 +315,8 @@ func Compare(a, b Labels) int {
 	return len(a) - len(b)
 }
 
-// Copy labels from b on top of whatever was in ls previously, reusing memory or expanding if needed.
+// CopyFrom copies labels from b on top of whatever was in ls previously,
+// reusing memory or expanding if needed.
 func (ls *Labels) CopyFrom(b Labels) {
 	(*ls) = append((*ls)[:0], b...)
 }
@@ -422,7 +423,7 @@ type ScratchBuilder struct {
 	add Labels
 }
 
-// Symbol-table is no-op, just for api parity with dedupelabels.
+// SymbolTable is no-op, just for api parity with dedupelabels.
 type SymbolTable struct{}
 
 func NewSymbolTable() *SymbolTable { return nil }
@@ -458,7 +459,7 @@ func (b *ScratchBuilder) Add(name, value string) {
 	b.add = append(b.add, Label{Name: name, Value: value})
 }
 
-// Add a name/value pair, using []byte instead of string.
+// UnsafeAddBytes adds a name/value pair, using []byte instead of string.
 // The '-tags stringlabels' version of this function is unsafe, hence the name.
 // This version is safe - it copies the strings immediately - but we keep the same name so everything compiles.
 func (b *ScratchBuilder) UnsafeAddBytes(name, value []byte) {
@@ -475,14 +476,14 @@ func (b *ScratchBuilder) Assign(ls Labels) {
 	b.add = append(b.add[:0], ls...) // Copy on top of our slice, so we don't retain the input slice.
 }
 
-// Return the name/value pairs added so far as a Labels object.
+// Labels returns the name/value pairs added so far as a Labels object.
 // Note: if you want them sorted, call Sort() first.
 func (b *ScratchBuilder) Labels() Labels {
 	// Copy the slice, so the next use of ScratchBuilder doesn't overwrite.
 	return append([]Label{}, b.add...)
 }
 
-// Write the newly-built Labels out to ls.
+// Overwrite the newly-built Labels out to ls.
 // Callers must ensure that there are no other references to ls, or any strings fetched from it.
 func (b *ScratchBuilder) Overwrite(ls *Labels) {
 	*ls = append((*ls)[:0], b.add...)

model/textparse/interface.go

@@ -106,8 +106,8 @@ const (
 	EntryInvalid   Entry = -1
 	EntryType      Entry = 0
 	EntryHelp      Entry = 1
-	EntrySeries    Entry = 2 // A series with a simple float64 as value.
+	EntrySeries    Entry = 2 // EntrySeries marks a series with a simple float64 as value.
 	EntryComment   Entry = 3
 	EntryUnit      Entry = 4
-	EntryHistogram Entry = 5 // A series with a native histogram as a value.
+	EntryHistogram Entry = 5 // EntryHistogram marks a series with a native histogram as a value.
 )

promql/engine.go

@@ -573,7 +573,7 @@ func (ng *Engine) validateOpts(expr parser.Expr) error {
 	return validationErr
 }
 
-// NewTestQuery: inject special behaviour into Query for testing.
+// NewTestQuery injects special behaviour into Query for testing.
 func (ng *Engine) NewTestQuery(f func(context.Context) error) Query {
 	qry := &query{
 		q:           "test statement",
@@ -3531,14 +3531,14 @@ func makeInt64Pointer(val int64) *int64 {
 	return valp
 }
 
-// Add RatioSampler interface to allow unit-testing (previously: Randomizer).
+// RatioSampler allows unit-testing (previously: Randomizer).
 type RatioSampler interface {
 	// Return this sample "offset" between [0.0, 1.0]
 	sampleOffset(ts int64, sample *Sample) float64
 	AddRatioSample(r float64, sample *Sample) bool
 }
 
-// Use Hash(labels.String()) / maxUint64 as a "deterministic"
+// HashRatioSampler uses Hash(labels.String()) / maxUint64 as a "deterministic"
 // value in [0.0, 1.0].
 type HashRatioSampler struct{}
 

promql/parser/ast.go

@@ -352,8 +352,7 @@ func (f inspector) Visit(node Node, path []Node) (Visitor, error) {
 // f(node, path); node must not be nil. If f returns a nil error, Inspect invokes f
 // for all the non-nil children of node, recursively.
 func Inspect(node Node, f inspector) {
-	//nolint: errcheck
-	Walk(f, node, nil)
+	Walk(f, node, nil) //nolint:errcheck
 }
 
 // Children returns a list of all child nodes of a syntax tree node.
@@ -419,7 +418,7 @@ func mergeRanges(first, last Node) posrange.PositionRange {
 	}
 }
 
-// Item implements the Node interface.
+// PositionRange implements the Node interface.
 // This makes it possible to call mergeRanges on them.
 func (i *Item) PositionRange() posrange.PositionRange {
 	return posrange.PositionRange{

scrape/clientprotobuf.go

@@ -23,7 +23,7 @@ import (
 	dto "github.com/prometheus/client_model/go"
 )
 
-// Write a MetricFamily into a protobuf.
+// MetricFamilyToProtobuf writes a MetricFamily into a protobuf.
 // This function is intended for testing scraping by providing protobuf serialized input.
 func MetricFamilyToProtobuf(metricFamily *dto.MetricFamily) ([]byte, error) {
 	buffer := &bytes.Buffer{}
@@ -34,7 +34,7 @@ func MetricFamilyToProtobuf(metricFamily *dto.MetricFamily) ([]byte, error) {
 	return buffer.Bytes(), nil
 }
 
-// Append a MetricFamily protobuf representation to a buffer.
+// AddMetricFamilyToProtobuf appends a MetricFamily protobuf representation to a buffer.
 // This function is intended for testing scraping by providing protobuf serialized input.
 func AddMetricFamilyToProtobuf(buffer *bytes.Buffer, metricFamily *dto.MetricFamily) error {
 	protoBuf, err := proto.Marshal(metricFamily)

storage/interface.go

@@ -227,9 +227,9 @@ type LabelHints struct {
 	Limit int
 }
 
-// TODO(bwplotka): Move to promql/engine_test.go?
 // QueryableFunc is an adapter to allow the use of ordinary functions as
 // Queryables. It follows the idea of http.HandlerFunc.
+// TODO(bwplotka): Move to promql/engine_test.go?
 type QueryableFunc func(mint, maxt int64) (Querier, error)
 
 // Querier calls f() with the given parameters.

storage/remote/azuread/azuread.go

@@ -31,13 +31,15 @@ import (
 	"github.com/google/uuid"
 )
 
+// Clouds.
 const (
-	// Clouds.
 	AzureChina      = "AzureChina"
 	AzureGovernment = "AzureGovernment"
 	AzurePublic     = "AzurePublic"
+)
 
-	// Audiences.
+// Audiences.
+const (
 	IngestionChinaAudience      = "https://monitor.azure.cn//.default"
 	IngestionGovernmentAudience = "https://monitor.azure.us//.default"
 	IngestionPublicAudience     = "https://monitor.azure.com//.default"

template/template.go

@@ -166,7 +166,7 @@ func NewTemplateExpander(
 				return html_template.HTML(text)
 			},
 			"match":     regexp.MatchString,
-			"title":     strings.Title, //nolint:staticcheck
+			"title":     strings.Title, //nolint:staticcheck // TODO(beorn7): Need to come up with a replacement using the cases package.
 			"toUpper":   strings.ToUpper,
 			"toLower":   strings.ToLower,
 			"graphLink": strutil.GraphLinkForExpression,

tsdb/chunks/head_chunks.go

@@ -191,7 +191,7 @@ func (f *chunkPos) bytesToWriteForChunk(chkLen uint64) uint64 {
 // ChunkDiskMapper is for writing the Head block chunks to disk
 // and access chunks via mmapped files.
 type ChunkDiskMapper struct {
-	/// Writer.
+	// Writer.
 	dir             *os.File
 	writeBufferSize int
 
@@ -210,7 +210,7 @@ type ChunkDiskMapper struct {
 	crc32        hash.Hash
 	writePathMtx sync.Mutex
 
-	/// Reader.
+	// Reader.
 	// The int key in the map is the file number on the disk.
 	mmappedChunkFiles map[int]*mmappedChunkFile // Contains the m-mapped files for each chunk file mapped with its index.
 	closers           map[int]io.Closer         // Closers for resources behind the byte slices.

tsdb/db.go

@@ -49,7 +49,7 @@ import (
 )
 
 const (
-	// Default duration of a block in milliseconds.
+	// DefaultBlockDuration in milliseconds.
 	DefaultBlockDuration = int64(2 * time.Hour / time.Millisecond)
 
 	// Block dir suffixes to make deletion and creation operations atomic.

tsdb/encoding/encoding.go

@@ -201,8 +201,8 @@ func (d *Decbuf) UvarintStr() string {
 	return string(d.UvarintBytes())
 }
 
-// The return value becomes invalid if the byte slice goes away.
-// Compared to UvarintStr, this avoid allocations.
+// UvarintBytes returns invalid values if the byte slice goes away.
+// Compared to UvarintStr, it avoid allocations.
 func (d *Decbuf) UvarintBytes() []byte {
 	l := d.Uvarint64()
 	if d.E != nil {