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/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

@@ -17,7 +17,7 @@ func BenchmarkAssign40BytesStruct(b *testing.B) {
 		c int
 	}
 
-	s := S{}
+	s := S{b: "", c: 0}
 
 	for i := 0; i != b.N; i++ {
 		s = S{a: "hello"}
@@ -31,7 +31,7 @@ func BenchmarkAssign32BytesStruct(b *testing.B) {
 		b string
 	}
 
-	s := S{}
+	var s S
 
 	for i := 0; i != b.N; i++ {
 		s = S{a: "hello"}

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_test.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -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_test.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -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) {}

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/metrics.go

@@ -58,14 +58,14 @@ type nullBody struct{}
 
 func (n *nullBody) Close() error { return nil }
 
-func (n *nullBody) Read(b []byte) (int, error) { return 0, io.EOF }
+func (n *nullBody) Read([]byte) (int, error) { return 0, io.EOF }
 
 type requestBody struct {
 	body    io.ReadCloser
 	eng     *stats.Engine
-	req     *http.Request
 	metrics *metrics
 	bytes   int
+	req     *http.Request
 	op      string
 	once    sync.Once
 }

procstats/delaystats_linux.go

@@ -2,20 +2,20 @@ package procstats
 
 import (
 	"errors"
-	"syscall"
 
 	"github.com/mdlayher/taskstats"
+	"golang.org/x/sys/unix"
 )
 
 func collectDelayInfo(pid int) DelayInfo {
 	client, err := taskstats.New()
-	if err == syscall.ENOENT {
+	if err == unix.ENOENT {
 		err = errors.New("failed to communicate with taskstats Netlink family, ensure this program is not running in a network namespace")
 	}
 	check(err)
 
 	stats, err := client.TGID(pid)
-	if err == syscall.EPERM {
+	if err == unix.EPERM {
 		err = errors.New("failed to open Netlink socket: permission denied, ensure CAP_NET_RAW is enabled for this process, or run it with root privileges")
 	}
 	check(err)

procstats/linux/memory_linux.go

@@ -5,7 +5,8 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
-	"syscall"
+
+	"golang.org/x/sys/unix"
 )
 
 func readMemoryLimit(pid int) (limit uint64, err error) {
@@ -54,10 +55,10 @@ func readMemoryCGroupMemoryLimitFilePath(cgroupPath string) string {
 }
 
 func readSysinfoMemoryLimit() (limit uint64, err error) {
-	var sysinfo syscall.Sysinfo_t
+	var sysinfo unix.Sysinfo_t
 
-	if err = syscall.Sysinfo(&sysinfo); err == nil {
-		// syscall.Sysinfo returns an uint32 on linux/arm, but uint64 otherwise
+	if err = unix.Sysinfo(&sysinfo); err == nil {
+		// unix.Sysinfo returns an uint32 on linux/arm, but uint64 otherwise
 		limit = uint64(sysinfo.Unit) * uint64(sysinfo.Totalram)
 	}
 

procstats/linux/stat.go

@@ -15,9 +15,10 @@ const (
 	TracingStop                     ProcState = 't'
 	Paging                          ProcState = 'P'
 	Dead                            ProcState = 'X'
-	Dead_                           ProcState = 'x'
-	Wakekill                        ProcState = 'W'
-	Parked                          ProcState = 'P'
+	//revive:disable-next-line
+	Dead_    ProcState = 'x'
+	Wakekill ProcState = 'W'
+	Parked   ProcState = 'P'
 )
 
 // Scan updates the ProcState for a process.

procstats/proc.go

@@ -134,7 +134,7 @@ func (p *ProcMetrics) Collect() {
 		now := time.Now()
 
 		if !p.lastTime.IsZero() {
-			ratio := 1.0
+			var ratio float64
 			switch {
 			case m.CPU.Period > 0 && m.CPU.Quota > 0:
 				ratio = float64(m.CPU.Quota) / float64(m.CPU.Period)