all: use Go 1.26 things, run most gofix modernizers

I omitted a lot of the min/max modernizers because they didn't
result in more clear code.

Some of it's older "for x := range 123".

Also: errors.AsType, any, fmt.Appendf, etc.

Updates #18682

Change-Id: I83a451577f33877f962766a5b65ce86f7696471c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

util/dnsname/dnsname.go

@@ -234,7 +234,7 @@ func ValidHostname(hostname string) error {
 		return err
 	}
 
-	for _, label := range strings.Split(fqdn.WithoutTrailingDot(), ".") {
+	for label := range strings.SplitSeq(fqdn.WithoutTrailingDot(), ".") {
 		if err := ValidLabel(label); err != nil {
 			return err
 		}

util/goroutines/goroutines.go

@@ -52,7 +52,7 @@ func scrubHex(buf []byte) []byte {
 			in[0] = '?'
 			return
 		}
-		v := []byte(fmt.Sprintf("v%d%%%d", len(saw)+1, u64%8))
+		v := fmt.Appendf(nil, "v%d%%%d", len(saw)+1, u64%8)
 		saw[inStr] = v
 		copy(in, v)
 	})

util/hashx/block512_test.go

@@ -47,7 +47,7 @@ type hasher interface {
 
 func hashSuite(h hasher) {
 	for i := range 10 {
-		for j := 0; j < 10; j++ {
+		for range 10 {
 			h.HashUint8(0x01)
 			h.HashUint8(0x23)
 			h.HashUint32(0x456789ab)

util/httphdr/httphdr.go

@@ -44,7 +44,7 @@ func ParseRange(hdr string) (ranges []Range, ok bool) {
 	hdr = strings.Trim(hdr, ows) // per RFC 7230, section 3.2
 	units, elems, hasUnits := strings.Cut(hdr, "=")
 	elems = strings.TrimLeft(elems, ","+ows)
-	for _, elem := range strings.Split(elems, ",") {
+	for elem := range strings.SplitSeq(elems, ",") {
 		elem = strings.Trim(elem, ows) // per RFC 7230, section 7
 		switch {
 		case strings.HasPrefix(elem, "-"): // i.e., "-" suffix-length

util/httpm/httpm_test.go

@@ -27,7 +27,7 @@ func TestUsedConsistently(t *testing.T) {
 	cmd := exec.Command("git", "grep", "-l", "-F", "http.Method")
 	cmd.Dir = rootDir
 	matches, _ := cmd.Output()
-	for _, fn := range strings.Split(strings.TrimSpace(string(matches)), "\n") {
+	for fn := range strings.SplitSeq(strings.TrimSpace(string(matches)), "\n") {
 		switch fn {
 		case "util/httpm/httpm.go", "util/httpm/httpm_test.go":
 			continue

util/linuxfw/fake.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"slices"
 	"strconv"
 	"strings"
 )
@@ -60,10 +61,8 @@ func (n *fakeIPTables) Append(table, chain string, args ...string) error {
 func (n *fakeIPTables) Exists(table, chain string, args ...string) (bool, error) {
 	k := table + "/" + chain
 	if rules, ok := n.n[k]; ok {
-		for _, rule := range rules {
-			if rule == strings.Join(args, " ") {
-				return true, nil
-			}
+		if slices.Contains(rules, strings.Join(args, " ")) {
+			return true, nil
 		}
 		return false, nil
 	} else {

util/linuxfw/iptables.go

@@ -21,8 +21,8 @@ import (
 
 func init() {
 	isNotExistError = func(err error) bool {
-		var e *iptables.Error
-		return errors.As(err, &e) && e.IsNotExist()
+		e, ok := errors.AsType[*iptables.Error](err)
+		return ok && e.IsNotExist()
 	}
 }
 

util/linuxfw/nftables_for_svcs.go

@@ -236,7 +236,7 @@ func portMapRule(t *nftables.Table, ch *nftables.Chain, tun string, targetIP net
 // This metadata can then be used to find the rule.
 // https://github.com/google/nftables/issues/48
 func svcPortMapRuleMeta(svcName string, targetIP netip.Addr, pm PortMap) []byte {
-	return []byte(fmt.Sprintf("svc:%s,targetIP:%s:matchPort:%v,targetPort:%v,proto:%v", svcName, targetIP.String(), pm.MatchPort, pm.TargetPort, pm.Protocol))
+	return fmt.Appendf(nil, "svc:%s,targetIP:%s:matchPort:%v,targetPort:%v,proto:%v", svcName, targetIP.String(), pm.MatchPort, pm.TargetPort, pm.Protocol)
 }
 
 func (n *nftablesRunner) findRuleByMetadata(t *nftables.Table, ch *nftables.Chain, meta []byte) (*nftables.Rule, error) {
@@ -305,5 +305,5 @@ func protoFromString(s string) (uint8, error) {
 // This metadata can then be used to find the rule.
 // https://github.com/google/nftables/issues/48
 func svcRuleMeta(svcName string, origDst, dst netip.Addr) []byte {
-	return []byte(fmt.Sprintf("svc:%s,VIP:%s,ClusterIP:%s", svcName, origDst.String(), dst.String()))
+	return fmt.Appendf(nil, "svc:%s,VIP:%s,ClusterIP:%s", svcName, origDst.String(), dst.String())
 }

util/linuxfw/nftables_runner_test.go

@@ -1066,7 +1066,7 @@ func checkSNATRule_nft(t *testing.T, runner *nftablesRunner, fam nftables.TableF
 	if chain == nil {
 		t.Fatal("POSTROUTING chain does not exist")
 	}
-	meta := []byte(fmt.Sprintf("dst:%s,src:%s", dst.String(), src.String()))
+	meta := fmt.Appendf(nil, "dst:%s,src:%s", dst.String(), src.String())
 	wantsRule := snatRule(chain.Table, chain, src, dst, meta)
 	checkRule(t, wantsRule, runner.conn)
 }

util/pool/pool_test.go

@@ -94,12 +94,12 @@ func TestPool(t *testing.T) {
 
 func TestTakeRandom(t *testing.T) {
 	p := Pool[int]{}
-	for i := 0; i < 10; i++ {
+	for i := range 10 {
 		p.Add(i + 100)
 	}
 
 	seen := make(map[int]bool)
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		item, ok := p.TakeRandom()
 		if !ok {
 			t.Errorf("unexpected empty pool")
@@ -116,7 +116,7 @@ func TestTakeRandom(t *testing.T) {
 		t.Errorf("expected empty pool")
 	}
 
-	for i := 0; i < 10; i++ {
+	for i := range 10 {
 		want := 100 + i
 		if !seen[want] {
 			t.Errorf("item %v not seen", want)

util/set/intset.go

@@ -152,7 +152,7 @@ func (s bitSet) values() iter.Seq[uint64] {
 	return func(yield func(uint64) bool) {
 		// Hyrum-proofing: randomly iterate in forwards or reverse.
 		if rand.Uint64()%2 == 0 {
-			for i := 0; i < bits.UintSize; i++ {
+			for i := range bits.UintSize {
 				if s.contains(uint64(i)) && !yield(uint64(i)) {
 					return
 				}

util/singleflight/singleflight.go

@@ -36,7 +36,7 @@ var errGoexit = errors.New("runtime.Goexit was called")
 // A panicError is an arbitrary value recovered from a panic
 // with the stack trace during the execution of given function.
 type panicError struct {
-	value interface{}
+	value any
 	stack []byte
 }
 
@@ -45,7 +45,7 @@ func (p *panicError) Error() string {
 	return fmt.Sprintf("%v\n\n%s", p.value, p.stack)
 }
 
-func newPanicError(v interface{}) error {
+func newPanicError(v any) error {
 	stack := debug.Stack()
 
 	// The first line of the stack trace is of the form "goroutine N [status]:"

util/singleflight/singleflight_test.go

@@ -25,7 +25,7 @@ import (
 
 func TestDo(t *testing.T) {
 	var g Group[string, any]
-	v, err, _ := g.Do("key", func() (interface{}, error) {
+	v, err, _ := g.Do("key", func() (any, error) {
 		return "bar", nil
 	})
 	if got, want := fmt.Sprintf("%v (%T)", v, v), "bar (string)"; got != want {
@@ -39,7 +39,7 @@ func TestDo(t *testing.T) {
 func TestDoErr(t *testing.T) {
 	var g Group[string, any]
 	someErr := errors.New("Some error")
-	v, err, _ := g.Do("key", func() (interface{}, error) {
+	v, err, _ := g.Do("key", func() (any, error) {
 		return nil, someErr
 	})
 	if err != someErr {
@@ -55,7 +55,7 @@ func TestDoDupSuppress(t *testing.T) {
 	var wg1, wg2 sync.WaitGroup
 	c := make(chan string, 1)
 	var calls int32
-	fn := func() (interface{}, error) {
+	fn := func() (any, error) {
 		if atomic.AddInt32(&calls, 1) == 1 {
 			// First invocation.
 			wg1.Done()
@@ -72,9 +72,7 @@ func TestDoDupSuppress(t *testing.T) {
 	wg1.Add(1)
 	for range n {
 		wg1.Add(1)
-		wg2.Add(1)
-		go func() {
-			defer wg2.Done()
+		wg2.Go(func() {
 			wg1.Done()
 			v, err, _ := g.Do("key", fn)
 			if err != nil {
@@ -84,7 +82,7 @@ func TestDoDupSuppress(t *testing.T) {
 			if s, _ := v.(string); s != "bar" {
 				t.Errorf("Do = %T %v; want %q", v, v, "bar")
 			}
-		}()
+		})
 	}
 	wg1.Wait()
 	// At least one goroutine is in fn now and all of them have at
@@ -108,7 +106,7 @@ func TestForget(t *testing.T) {
 	)
 
 	go func() {
-		g.Do("key", func() (i interface{}, e error) {
+		g.Do("key", func() (i any, e error) {
 			close(firstStarted)
 			<-unblockFirst
 			close(firstFinished)
@@ -119,7 +117,7 @@ func TestForget(t *testing.T) {
 	g.Forget("key")
 
 	unblockSecond := make(chan struct{})
-	secondResult := g.DoChan("key", func() (i interface{}, e error) {
+	secondResult := g.DoChan("key", func() (i any, e error) {
 		<-unblockSecond
 		return 2, nil
 	})
@@ -127,7 +125,7 @@ func TestForget(t *testing.T) {
 	close(unblockFirst)
 	<-firstFinished
 
-	thirdResult := g.DoChan("key", func() (i interface{}, e error) {
+	thirdResult := g.DoChan("key", func() (i any, e error) {
 		return 3, nil
 	})
 
@@ -141,7 +139,7 @@ func TestForget(t *testing.T) {
 
 func TestDoChan(t *testing.T) {
 	var g Group[string, any]
-	ch := g.DoChan("key", func() (interface{}, error) {
+	ch := g.DoChan("key", func() (any, error) {
 		return "bar", nil
 	})
 
@@ -160,7 +158,7 @@ func TestDoChan(t *testing.T) {
 // See https://github.com/golang/go/issues/41133
 func TestPanicDo(t *testing.T) {
 	var g Group[string, any]
-	fn := func() (interface{}, error) {
+	fn := func() (any, error) {
 		panic("invalid memory address or nil pointer dereference")
 	}
 
@@ -197,7 +195,7 @@ func TestPanicDo(t *testing.T) {
 
 func TestGoexitDo(t *testing.T) {
 	var g Group[string, any]
-	fn := func() (interface{}, error) {
+	fn := func() (any, error) {
 		runtime.Goexit()
 		return nil, nil
 	}
@@ -238,7 +236,7 @@ func TestPanicDoChan(t *testing.T) {
 		}()
 
 		g := new(Group[string, any])
-		ch := g.DoChan("", func() (interface{}, error) {
+		ch := g.DoChan("", func() (any, error) {
 			panic("Panicking in DoChan")
 		})
 		<-ch
@@ -283,7 +281,7 @@ func TestPanicDoSharedByDoChan(t *testing.T) {
 			defer func() {
 				recover()
 			}()
-			g.Do("", func() (interface{}, error) {
+			g.Do("", func() (any, error) {
 				close(blocked)
 				<-unblock
 				panic("Panicking in Do")
@@ -291,7 +289,7 @@ func TestPanicDoSharedByDoChan(t *testing.T) {
 		}()
 
 		<-blocked
-		ch := g.DoChan("", func() (interface{}, error) {
+		ch := g.DoChan("", func() (any, error) {
 			panic("DoChan unexpectedly executed callback")
 		})
 		close(unblock)
@@ -325,8 +323,7 @@ func TestPanicDoSharedByDoChan(t *testing.T) {
 
 func TestDoChanContext(t *testing.T) {
 	t.Run("Basic", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
+		ctx := t.Context()
 
 		var g Group[string, int]
 		ch := g.DoChanContext(ctx, "key", func(_ context.Context) (int, error) {
@@ -337,8 +334,7 @@ func TestDoChanContext(t *testing.T) {
 	})
 
 	t.Run("DoesNotPropagateValues", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
+		ctx := t.Context()
 
 		key := new(int)
 		const value = "hello world"
@@ -364,8 +360,7 @@ func TestDoChanContext(t *testing.T) {
 
 		ctx1, cancel1 := context.WithCancel(context.Background())
 		defer cancel1()
-		ctx2, cancel2 := context.WithCancel(context.Background())
-		defer cancel2()
+		ctx2 := t.Context()
 
 		fn := func(ctx context.Context) (int, error) {
 			select {

util/slicesx/slicesx_test.go

@@ -53,7 +53,7 @@ func TestShuffle(t *testing.T) {
 	}
 
 	var wasShuffled bool
-	for try := 0; try < 10; try++ {
+	for range 10 {
 		shuffled := slices.Clone(sl)
 		Shuffle(shuffled)
 		if !reflect.DeepEqual(shuffled, sl) {

util/syspolicy/policytest/policytest.go

@@ -89,12 +89,7 @@ func (pc policyChanges) HasChanged(v pkey.Key) bool {
 	return ok
 }
 func (pc policyChanges) HasChangedAnyOf(keys ...pkey.Key) bool {
-	for _, k := range keys {
-		if pc.HasChanged(k) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(keys, pc.HasChanged)
 }
 
 const watchersKey = "_policytest_watchers"

util/topk/topk_test.go

@@ -43,7 +43,7 @@ func TestTopK(t *testing.T) {
 		got  []int
 		want = []int{5, 6, 7, 8, 9}
 	)
-	for try := 0; try < 10; try++ {
+	for range 10 {
 		topk := NewWithParams[int](5, func(in []byte, val int) []byte {
 			return binary.LittleEndian.AppendUint64(in, uint64(val))
 		}, 4, 1000)

util/vizerror/vizerror.go

@@ -77,6 +77,5 @@ func WrapWithMessage(wrapped error, publicMsg string) error {
 
 // As returns the first vizerror.Error in err's chain.
 func As(err error) (e Error, ok bool) {
-	ok = errors.As(err, &e)
-	return
+	return errors.AsType[Error](err)
 }

util/zstdframe/zstd_test.go

@@ -128,7 +128,7 @@ func BenchmarkEncode(b *testing.B) {
 		b.Run(bb.name, func(b *testing.B) {
 			b.ReportAllocs()
 			b.SetBytes(int64(len(src)))
-			for range b.N {
+			for b.Loop() {
 				dst = AppendEncode(dst[:0], src, bb.opts...)
 			}
 		})
@@ -153,7 +153,7 @@ func BenchmarkDecode(b *testing.B) {
 		b.Run(bb.name, func(b *testing.B) {
 			b.ReportAllocs()
 			b.SetBytes(int64(len(src)))
-			for range b.N {
+			for b.Loop() {
 				dst = must.Get(AppendDecode(dst[:0], src, bb.opts...))
 			}
 		})
@@ -169,16 +169,14 @@ func BenchmarkEncodeParallel(b *testing.B) {
 		}
 		b.Run(coder.name, func(b *testing.B) {
 			b.ReportAllocs()
-			for range b.N {
-				var group sync.WaitGroup
-				for j := 0; j < numCPU; j++ {
-					group.Add(1)
-					go func(j int) {
-						defer group.Done()
+			for b.Loop() {
+				var wg sync.WaitGroup
+				for j := range numCPU {
+					wg.Go(func() {
 						dsts[j] = coder.appendEncode(dsts[j][:0], src)
-					}(j)
+					})
 				}
-				group.Wait()
+				wg.Wait()
 			}
 		})
 	}
@@ -194,16 +192,14 @@ func BenchmarkDecodeParallel(b *testing.B) {
 		}
 		b.Run(coder.name, func(b *testing.B) {
 			b.ReportAllocs()
-			for range b.N {
-				var group sync.WaitGroup
-				for j := 0; j < numCPU; j++ {
-					group.Add(1)
-					go func(j int) {
-						defer group.Done()
+			for b.Loop() {
+				var wg sync.WaitGroup
+				for j := range numCPU {
+					wg.Go(func() {
 						dsts[j] = must.Get(coder.appendDecode(dsts[j][:0], src))
-					}(j)
+					})
 				}
-				group.Wait()
+				wg.Wait()
 			}
 		})
 	}