all: fix lint issues

We turned on the linter to lint the "main" branch and any release
branches, but we never actually fixed any of the issues reported by
the linter. This is an attempt to do so. A lot of red herrings but
some legitimate errors.

Not strictly reported by the linter, but replace "syscall" uses with
"x/sys/unix", as is recommended.

buffer.go

@@ -156,7 +156,7 @@ func (b *buffer) len() int {
 }
 
 func (b *buffer) flush(w io.Writer, n int) {
-	w.Write(b.data[:n])
+	_, _ = w.Write(b.data[:n])
 	n = copy(b.data, b.data[n:])
 	b.data = b.data[:n]
 }

cmd/dogstatsd/main.go

@@ -59,7 +59,7 @@ func client(cmd string, args ...string) {
 	args, extra = split(args, "--")
 	fset.StringVar(&addr, "addr", "localhost:8125", "The network address where a dogstatsd server is listening for incoming UDP datagrams")
 	fset.Var(&tags, "tags", "A comma-separated list of tags to set on the metric")
-	fset.Parse(args)
+	_ = fset.Parse(args)
 	args = fset.Args()
 
 	if len(args) == 0 {
@@ -74,17 +74,13 @@ func client(cmd string, args ...string) {
 			value = 1.0
 		} else if value, err = strconv.ParseFloat(args[0], 64); err != nil {
 			errorf("bad metric value: %s", args[0])
-		} else {
-			args = args[1:]
 		}
 
 	case "set":
 		if len(args) == 0 {
 			errorf("missing metric value")
 		} else if value, err = strconv.ParseFloat(args[0], 64); err != nil {
 			errorf("bad metric value: %s", args[0])
-		} else {
-			args = args[1:]
 		}
 	}
 
@@ -110,19 +106,19 @@ func server(args ...string) {
 	var bind string
 
 	fset.StringVar(&bind, "bind", ":8125", "The network address to listen on for incoming UDP datagrams")
-	fset.Parse(args)
+	_ = fset.Parse(args)
 	log.Printf("listening for incoming UDP datagram on %s", bind)
 
-	datadog.ListenAndServe(bind, handlers{})
+	_ = datadog.ListenAndServe(bind, handlers{})
 }
 
 type handlers struct{}
 
-func (h handlers) HandleMetric(m datadog.Metric, a net.Addr) {
+func (h handlers) HandleMetric(m datadog.Metric, _ net.Addr) {
 	log.Print(m)
 }
 
-func (h handlers) HandleEvent(e datadog.Event, a net.Addr) {
+func (h handlers) HandleEvent(e datadog.Event, _ net.Addr) {
 	log.Print(e)
 }
 

context_test.go

@@ -17,7 +17,8 @@ func TestContextTags(t *testing.T) {
 	assert.Equal(t, 0, len(ContextTags(x)), "Original context should have no tags (because no context with key)")
 
 	// create a child context which creates a child context
-	z := context.WithValue(y, interface{}("not"), "important")
+	type unimportant struct{}
+	z := context.WithValue(y, unimportant{}, "important")
 	assert.Equal(t, 1, len(ContextTags(z)), "We should still be able to see original tags")
 
 	// Add tags to the child context's reference to the original tag slice

datadog/append_test.go

@@ -4,7 +4,7 @@ import "testing"
 
 func TestAppendMetric(t *testing.T) {
 	for _, test := range testMetrics {
-		t.Run(test.m.Name, func(b *testing.T) {
+		t.Run(test.m.Name, func(t *testing.T) {
 			if s := string(appendMetric(nil, test.m)); s != test.s {
 				t.Errorf("\n<<< %#v\n>>> %#v", test.s, s)
 			}

datadog/client.go

@@ -4,10 +4,10 @@ import (
 	"log"
 	"net"
 	"os"
-	"syscall"
 	"time"
 
 	"github.com/segmentio/stats/v4"
+	"golang.org/x/sys/unix"
 )
 
 const (
@@ -158,7 +158,7 @@ func dial(address string, sizehint int) (conn net.Conn, bufsize int, err error)
 	// sent in one batch we attempt to attempt to adjust the kernel buffer size
 	// to accept larger datagrams, or fallback to the default socket buffer size
 	// if it failed.
-	if bufsize, err = syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF); err != nil {
+	if bufsize, err = unix.GetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_SNDBUF); err != nil {
 		conn.Close()
 		return
 	}
@@ -169,7 +169,7 @@ func dial(address string, sizehint int) (conn net.Conn, bufsize int, err error)
 	bufsize /= 2
 
 	for sizehint > bufsize && sizehint > 0 {
-		if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF, sizehint); err == nil {
+		if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_SNDBUF, sizehint); err == nil {
 			bufsize = sizehint
 			break
 		}
@@ -194,6 +194,6 @@ func dial(address string, sizehint int) (conn net.Conn, bufsize int, err error)
 	}
 
 	// Creating the file put the socket in blocking mode, reverting.
-	syscall.SetNonblock(fd, true)
+	_ = unix.SetNonblock(fd, true)
 	return
 }

datadog/client_test.go

@@ -3,17 +3,15 @@ package datadog
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"strings"
 	"sync/atomic"
 	"testing"
 	"time"
 
-	"github.com/stretchr/testify/assert"
-
 	"github.com/segmentio/stats/v4"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestClient(t *testing.T) {
@@ -117,7 +115,7 @@ main.http.rtt.seconds:0.001215296|h|#http_req_content_charset:,http_req_content_
 	count := int32(0)
 	expect := int32(strings.Count(data, "\n"))
 
-	addr, closer := startTestServer(t, HandlerFunc(func(m Metric, _ net.Addr) {
+	addr, closer := startTestServer(t, HandlerFunc(func(_ Metric, _ net.Addr) {
 		atomic.AddInt32(&count, 1)
 	}))
 	defer closer.Close()
@@ -136,7 +134,7 @@ main.http.rtt.seconds:0.001215296|h|#http_req_content_charset:,http_req_content_
 }
 
 func BenchmarkClient(b *testing.B) {
-	log.SetOutput(ioutil.Discard)
+	log.SetOutput(io.Discard)
 
 	for _, N := range []int{1, 10, 100} {
 		b.Run(fmt.Sprintf("write a batch of %d measures to a client", N), func(b *testing.B) {

datadog/event.go

@@ -51,6 +51,6 @@ func (e Event) String() string {
 func (e Event) Format(f fmt.State, _ rune) {
 	buf := bufferPool.Get().(*buffer)
 	buf.b = appendEvent(buf.b[:0], e)
-	f.Write(buf.b)
+	_, _ = f.Write(buf.b)
 	bufferPool.Put(buf)
 }

datadog/metric.go

@@ -39,7 +39,7 @@ func (m Metric) String() string {
 func (m Metric) Format(f fmt.State, _ rune) {
 	buf := bufferPool.Get().(*buffer)
 	buf.b = appendMetric(buf.b[:0], m)
-	f.Write(buf.b)
+	_, _ = f.Write(buf.b)
 	bufferPool.Put(buf)
 }
 

datadog/server.go

@@ -33,9 +33,7 @@ func (f HandlerFunc) HandleMetric(m Metric, a net.Addr) {
 }
 
 // HandleEvent is a no-op for backwards compatibility.
-func (f HandlerFunc) HandleEvent(Event, net.Addr) {
-	return
-}
+func (f HandlerFunc) HandleEvent(Event, net.Addr) {}
 
 // ListenAndServe starts a new dogstatsd server, listening for UDP datagrams on
 // addr and forwarding the metrics to handler.

engine_test.go

@@ -64,6 +64,10 @@ func TestEngine(t *testing.T) {
 			scenario: "calling Engine.Clock produces expected metrics",
 			function: testEngineClock,
 		},
+		{
+			scenario: "calling Engine.WithTags produces expected tags",
+			function: testEngineWithTags,
+		},
 	}
 
 	for _, test := range tests {
@@ -307,6 +311,7 @@ func checkMeasuresEqual(t *testing.T, eng *stats.Engine, expected ...stats.Measu
 }
 
 func measures(t *testing.T, eng *stats.Engine) []stats.Measure {
+	t.Helper()
 	return eng.Handler.(*statstest.Handler).Measures()
 }
 

field_test.go

@@ -17,10 +17,10 @@ func BenchmarkAssign40BytesStruct(b *testing.B) {
 		c int
 	}
 
-	s := S{}
+	var s S
 
 	for i := 0; i != b.N; i++ {
-		s = S{a: "hello"}
+		s = S{a: "hello", b: "", c: 0}
 		_ = s
 	}
 }
@@ -31,10 +31,10 @@ func BenchmarkAssign32BytesStruct(b *testing.B) {
 		b string
 	}
 
-	s := S{}
+	var s S
 
 	for i := 0; i != b.N; i++ {
-		s = S{a: "hello"}
+		s = S{a: "hello", b: ""}
 		_ = s
 	}
 }

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/stretchr/testify v1.8.4
 	golang.org/x/exp v0.0.0-20231206192017-f3f8817b8deb
 	golang.org/x/sync v0.3.0
+	golang.org/x/sys v0.12.0
 )
 
 require github.com/davecgh/go-spew v1.1.1 // indirect
@@ -20,7 +21,6 @@ require (
 	github.com/mdlayher/netlink v0.0.0-20190313131330-258ea9dff42c // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
-	golang.org/x/sys v0.12.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

grafana/annotations.go

@@ -117,7 +117,7 @@ type annotationsResponse struct {
 }
 
 func (res *annotationsResponse) WriteAnnotation(a Annotation) {
-	res.enc.Encode(annotationInfo{
+	_ = res.enc.Encode(annotationInfo{
 		Annotation: annotation{
 			Name:       res.name,
 			Datasource: res.datasource,

grafana/annotations_test.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -28,7 +28,7 @@ func TestAnnotationsHandler(t *testing.T) {
 
 	client := http.Client{}
 	server := httptest.NewServer(NewAnnotationsHandler(
-		AnnotationsHandlerFunc(func(ctx context.Context, res AnnotationsResponse, req *AnnotationsRequest) error {
+		AnnotationsHandlerFunc(func(_ context.Context, res AnnotationsResponse, req *AnnotationsRequest) error {
 			if !req.From.Equal(ar.Range.From) {
 				t.Error("bad 'from' time:", req.From, ar.Range.From)
 			}
@@ -79,7 +79,7 @@ func TestAnnotationsHandler(t *testing.T) {
 	}
 	defer r.Body.Close()
 
-	found, _ := ioutil.ReadAll(r.Body)
+	found, _ := io.ReadAll(r.Body)
 	expect := annotationsResult
 
 	if s := string(found); s != expect {

grafana/handler.go

@@ -47,7 +47,7 @@ func Handle(mux *http.ServeMux, prefix string, handler Handler) {
 	if _, pattern := mux.Handler(&http.Request{
 		URL: &url.URL{Path: root},
 	}); len(pattern) == 0 {
-		mux.HandleFunc(root, func(res http.ResponseWriter, req *http.Request) {
+		mux.HandleFunc(root, func(res http.ResponseWriter, _ *http.Request) {
 			setResponseHeaders(res)
 		})
 	}

grafana/query.go

@@ -191,13 +191,13 @@ func (res *queryResponse) close() error {
 
 func (res *queryResponse) flush() {
 	if res.timeserie != nil {
-		res.enc.Encode(res.timeserie)
+		_ = res.enc.Encode(res.timeserie)
 		res.timeserie.closed = true
 		res.timeserie = nil
 	}
 
 	if res.table != nil {
-		res.enc.Encode(res.table)
+		_ = res.enc.Encode(res.table)
 		res.table.closed = true
 		res.table = nil
 	}

grafana/query_test.go

@@ -32,7 +32,7 @@ func TestQueryHandler(t *testing.T) {
 
 	client := http.Client{}
 	server := httptest.NewServer(NewQueryHandler(
-		QueryHandlerFunc(func(ctx context.Context, res QueryResponse, req *QueryRequest) error {
+		QueryHandlerFunc(func(_ context.Context, res QueryResponse, req *QueryRequest) error {
 			if !req.From.Equal(t0) {
 				t.Error("bad 'from' time:", req.From, "!=", t0)
 			}

grafana/search.go

@@ -81,11 +81,11 @@ type searchResponse struct {
 }
 
 func (res *searchResponse) WriteTarget(target string) {
-	res.enc.Encode(target)
+	_ = res.enc.Encode(target)
 }
 
 func (res *searchResponse) WriteTargetValue(target string, value interface{}) {
-	res.enc.Encode(struct {
+	_ = res.enc.Encode(struct {
 		Target string      `json:"target"`
 		Value  interface{} `json:"value"`
 	}{target, value})

grafana/search_test.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -19,7 +19,7 @@ func TestSearchHandler(t *testing.T) {
 
 	client := http.Client{}
 	server := httptest.NewServer(NewSearchHandler(
-		SearchHandlerFunc(func(ctx context.Context, res SearchResponse, req *SearchRequest) error {
+		SearchHandlerFunc(func(_ context.Context, res SearchResponse, req *SearchRequest) error {
 			if req.Target != sr.Target {
 				t.Error("bad 'from' time:", req.Target, "!=", sr.Target)
 			}
@@ -44,7 +44,7 @@ func TestSearchHandler(t *testing.T) {
 	}
 	defer r.Body.Close()
 
-	found, _ := ioutil.ReadAll(r.Body)
+	found, _ := io.ReadAll(r.Body)
 	expect := searchResult
 
 	if s := string(found); s != expect {

handler.go

@@ -97,4 +97,4 @@ var Discard = &discard{}
 
 type discard struct{}
 
-func (*discard) HandleMeasures(time time.Time, measures ...Measure) {}
+func (*discard) HandleMeasures(time.Time, ...Measure) {}

handler_test.go

@@ -13,7 +13,7 @@ import (
 func TestMultiHandler(t *testing.T) {
 	t.Run("calling HandleMeasures on a multi-handler dispatches to each handler", func(t *testing.T) {
 		n := 0
-		f := stats.HandlerFunc(func(time time.Time, measures ...stats.Measure) { n++ })
+		f := stats.HandlerFunc(func(time.Time, ...stats.Measure) { n++ })
 		m := stats.MultiHandler(f, f, f)
 
 		m.HandleMeasures(time.Now())

httpstats/context_test.go

@@ -27,7 +27,8 @@ func TestRequestContextTagPropegation(t *testing.T) {
 	assert.Equal(t, 0, len(RequestTags(x)), "Original request should have no tags (because no context with key)")
 
 	// create a child request which creates a child context
-	z := y.WithContext(context.WithValue(y.Context(), interface{}("not"), "important"))
+	type contextVal struct{}
+	z := y.WithContext(context.WithValue(y.Context(), contextVal{}, "important"))
 	assert.Equal(t, 1, len(RequestTags(z)), "We should still be able to see original tags")
 
 	// Add tags to the child context's reference to the original tag slice

httpstats/handler_test.go

@@ -68,7 +68,7 @@ func TestHandlerHijack(t *testing.T) {
 	h := &statstest.Handler{}
 	e := stats.NewEngine("", h)
 
-	server := httptest.NewServer(NewHandlerWith(e, http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+	server := httptest.NewServer(NewHandlerWith(e, http.HandlerFunc(func(res http.ResponseWriter, _ *http.Request) {
 		// make sure the response writer supports hijacking
 		conn, _, _ := res.(http.Hijacker).Hijack()
 		conn.Close()