cmd/go: add check for unknown godebug setting

A //go:debug line mentioning an unknown or retired setting
should be diagnosed as making the program invalid. Do that.
We agreed on this in the proposal but I forgot to implement it.

Change-Id: Ie69072a1682d4eeb6866c02adbbb426f608567c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/476280
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

misc/cgo/testshared/shared_test.go

@@ -219,7 +219,7 @@ func cloneGOROOTDeps(goroot string) error {
 	for _, pkg := range pkgs {
 		parentFound := false
 		for _, prev := range pkgRoots {
-			if strings.HasPrefix(pkg, prev) {
+			if pkg == prev || strings.HasPrefix(pkg, prev+"/") {
 				// We will copy in the source for pkg when we copy in prev.
 				parentFound = true
 				break

src/cmd/dist/buildtool.go

@@ -65,6 +65,7 @@ var bootstrapDirs = []string{
 	"internal/coverage",
 	"internal/buildcfg",
 	"internal/goarch",
+	"internal/godebugs",
 	"internal/goexperiment",
 	"internal/goroot",
 	"internal/goversion",

src/cmd/go/gotoolchain.go

@@ -187,7 +187,7 @@ func execGoToolchain(gotoolchain, dir, exe string) {
 	// propagate signals and such, but there are no signals on Windows.
 	// We also use the exec case when GODEBUG=gotoolchainexec=0,
 	// to allow testing this code even when not on Windows.
-	if godebug.New("gotoolchainexec").Value() == "0" || runtime.GOOS == "windows" {
+	if godebug.New("#gotoolchainexec").Value() == "0" || runtime.GOOS == "windows" {
 		cmd := exec.Command(exe, os.Args[1:]...)
 		if runtime.GOOS == "windows" && strings.Contains(exe, "go1.999test") {
 			// See testdata/script/gotoolchain.txt.

src/cmd/go/internal/fsys/fsys.go

@@ -48,9 +48,9 @@ var (
 	traceFile *os.File
 	traceMu   sync.Mutex
 
-	gofsystrace      = godebug.New("gofsystrace")
+	gofsystrace      = godebug.New("#gofsystrace")
-	gofsystracelog   = godebug.New("gofsystracelog")
+	gofsystracelog   = godebug.New("#gofsystracelog")
-	gofsystracestack = godebug.New("gofsystracestack")
+	gofsystracestack = godebug.New("#gofsystracestack")
 )
 
 func init() {

src/cmd/go/internal/load/godebug.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"go/build"
+	"internal/godebugs"
 	"sort"
 	"strconv"
 	"strings"
@@ -43,7 +44,13 @@ func ParseGoDebug(text string) (key, value string, err error) {
 	if strings.ContainsAny(v, ",") {
 		return "", "", fmt.Errorf("value contains comma")
 	}
-	return k, v, nil
+
+	for _, info := range godebugs.All {
+		if k == info.Name {
+			return k, v, nil
+		}
+	}
+	return "", "", fmt.Errorf("unknown //go:debug setting %q", k)
 }
 
 // defaultGODEBUG returns the default GODEBUG setting for the main package p.
@@ -110,19 +117,10 @@ func godebugForGoVersion(v string) map[string]string {
 	}
 
 	def := make(map[string]string)
-	for _, d := range defaultGodebugs {
+	for _, info := range godebugs.All {
-		if (d.before != 0 && n < d.before) || (d.first != 0 && n >= d.first) {
+		if n < info.Changed {
-			def[d.name] = d.value
+			def[info.Name] = info.Old
 		}
 	}
 	return def
 }
-
-var defaultGodebugs = []struct {
-	before int // applies to Go versions up until this one (21 for Go 1.21)
-	first  int // applies to Go versions starting at this one (21 for Go 1.21)
-	name   string
-	value  string
-}{
-	{before: 21, name: "panicnil", value: "1"},
-}

src/cmd/go/internal/modindex/read.go

@@ -37,7 +37,7 @@ import (
 // It will be removed before the release.
 // TODO(matloob): Remove enabled once we have more confidence on the
 // module index.
-var enabled = godebug.New("goindex").Value() != "0"
+var enabled = godebug.New("#goindex").Value() != "0"
 
 // Module represents and encoded module index file. It is used to
 // do the equivalent of build.Import of packages in the module and answer other

src/cmd/go/testdata/script/godebug_unknown.txt

@@ -0,0 +1,9 @@
+! go build
+stderr 'p.go:1:1: invalid //go:debug: unknown //go:debug setting "x"'
+
+-- go.mod --
+module m
+-- p.go --
+//go:debug x=y
+package main
+func main() {}

src/go/build/deps_test.go

@@ -42,7 +42,7 @@ var depsRules = `
 	< constraints, container/list, container/ring,
 	  internal/cfg, internal/coverage, internal/coverage/rtcov,
 	  internal/coverage/uleb128, internal/coverage/calloc,
-	  internal/cpu, internal/goarch,
+	  internal/cpu, internal/goarch, internal/godebugs,
 	  internal/goexperiment, internal/goos,
 	  internal/goversion, internal/nettrace, internal/platform,
 	  log/internal,
@@ -55,7 +55,7 @@ var depsRules = `
 
 	# RUNTIME is the core runtime group of packages, all of them very light-weight.
 	internal/abi, internal/cpu, internal/goarch,
-	internal/coverage/rtcov, internal/goexperiment,
+	internal/coverage/rtcov, internal/godebugs, internal/goexperiment,
 	internal/goos, unsafe
 	< internal/bytealg
 	< internal/itoa

src/internal/cpu/cpu_test.go

@@ -48,7 +48,7 @@ func TestDisableAllCapabilities(t *testing.T) {
 func TestAllCapabilitiesDisabled(t *testing.T) {
 	MustHaveDebugOptionsSupport(t)
 
-	if godebug.New("cpu.all").Value() != "off" {
+	if godebug.New("#cpu.all").Value() != "off" {
 		t.Skipf("skipping test: GODEBUG=cpu.all=off not set")
 	}
 

src/internal/cpu/cpu_x86_test.go

@@ -28,7 +28,7 @@ func TestDisableSSE3(t *testing.T) {
 func TestSSE3DebugOption(t *testing.T) {
 	MustHaveDebugOptionsSupport(t)
 
-	if godebug.New("cpu.sse3").Value() != "off" {
+	if godebug.New("#cpu.sse3").Value() != "off" {
 		t.Skipf("skipping test: GODEBUG=cpu.sse3=off not set")
 	}
 

src/internal/fuzz/fuzz.go

@@ -1090,7 +1090,7 @@ var zeroVals []any = []any{
 	uint64(0),
 }
 
-var debugInfo = godebug.New("fuzzdebug").Value() == "1"
+var debugInfo = godebug.New("#fuzzdebug").Value() == "1"
 
 func shouldPrintDebugInfo() bool {
 	return debugInfo

src/internal/godebug/godebug.go

@@ -30,6 +30,7 @@
 package godebug
 
 import (
+	"internal/godebugs"
 	"sync"
 	"sync/atomic"
 	_ "unsafe" // go:linkname
@@ -46,21 +47,38 @@ type setting struct {
 	value          atomic.Pointer[string]
 	nonDefaultOnce sync.Once
 	nonDefault     atomic.Uint64
+	info           *godebugs.Info
 }
 
 // New returns a new Setting for the $GODEBUG setting with the given name.
+//
+// GODEBUGs meant for use by end users must be listed in ../godebugs/table.go,
+// which is used for generating and checking various documentation.
+// If the name is not listed in that table, New will succeed but calling Value
+// on the returned Setting will panic.
+// To disable that panic for access to an undocumented setting,
+// prefix the name with a #, as in godebug.New("#gofsystrace").
+// The # is a signal to New but not part of the key used in $GODEBUG.
 func New(name string) *Setting {
 	return &Setting{name: name}
 }
 
 // Name returns the name of the setting.
 func (s *Setting) Name() string {
+	if s.name != "" && s.name[0] == '#' {
+		return s.name[1:]
+	}
 	return s.name
 }
 
+// Undocumented reports whether this is an undocumented setting.
+func (s *Setting) Undocumented() bool {
+	return s.name != "" && s.name[0] == '#'
+}
+
 // String returns a printable form for the setting: name=value.
 func (s *Setting) String() string {
-	return s.name + "=" + s.Value()
+	return s.Name() + "=" + s.Value()
 }
 
 // IncNonDefault increments the non-default behavior counter
@@ -69,20 +87,16 @@ func (s *Setting) String() string {
 // /godebug/non-default-behavior/<name>:events.
 //
 // Note that Value must be called at least once before IncNonDefault.
-//
-// Any GODEBUG setting that can call IncNonDefault must be listed
-// in three more places:
-//
-//   - the table in ../runtime/metrics.go (search for non-default-behavior)
-//   - the table in ../../runtime/metrics/description.go (search for non-default-behavior; run 'go generate' afterward)
-//   - the table in ../../cmd/go/internal/load/godebug.go (search for defaultGodebugs)
 func (s *Setting) IncNonDefault() {
 	s.nonDefaultOnce.Do(s.register)
 	s.nonDefault.Add(1)
 }
 
 func (s *Setting) register() {
-	registerMetric("/godebug/non-default-behavior/"+s.name+":events", s.nonDefault.Load)
+	if s.info == nil || s.info.Opaque {
+		panic("godebug: unexpected IncNonDefault of " + s.name)
+	}
+	registerMetric("/godebug/non-default-behavior/"+s.Name()+":events", s.nonDefault.Load)
 }
 
 // cache is a cache of all the GODEBUG settings,
@@ -111,7 +125,10 @@ var empty string
 // caching of Value's result.
 func (s *Setting) Value() string {
 	s.once.Do(func() {
-		s.setting = lookup(s.name)
+		s.setting = lookup(s.Name())
+		if s.info == nil && !s.Undocumented() {
+			panic("godebug: Value of name not listed in godebugs.All: " + s.name)
+		}
 	})
 	return *s.value.Load()
 }
@@ -122,6 +139,7 @@ func lookup(name string) *setting {
 		return v.(*setting)
 	}
 	s := new(setting)
+	s.info = godebugs.Lookup(name)
 	s.value.Store(&empty)
 	if v, loaded := cache.LoadOrStore(name, s); loaded {
 		// Lost race: someone else created it. Use theirs.

src/internal/godebug/godebug_test.go

@@ -11,13 +11,13 @@ import (
 )
 
 func TestGet(t *testing.T) {
-	foo := New("foo")
+	foo := New("#foo")
 	tests := []struct {
 		godebug string
 		setting *Setting
 		want    string
 	}{
-		{"", New(""), ""},
+		{"", New("#"), ""},
 		{"", foo, ""},
 		{"foo=bar", foo, "bar"},
 		{"foo=bar,after=x", foo, "bar"},
@@ -28,7 +28,7 @@ func TestGet(t *testing.T) {
 		{"foo=", foo, ""},
 		{"foo", foo, ""},
 		{",foo", foo, ""},
-		{"foo=bar,baz", New("loooooooong"), ""},
+		{"foo=bar,baz", New("#loooooooong"), ""},
 	}
 	for _, tt := range tests {
 		t.Setenv("GODEBUG", tt.godebug)

src/internal/godebugs/godebugs_test.go

@@ -0,0 +1,41 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package godebugs_test
+
+import (
+	"internal/godebugs"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestAll(t *testing.T) {
+	data, err := os.ReadFile("../../../doc/godebug.md")
+	if err != nil {
+		t.Fatal(err)
+	}
+	doc := string(data)
+
+	last := ""
+	for _, info := range godebugs.All {
+		if info.Name <= last {
+			t.Errorf("All not sorted: %s then %s", last, info.Name)
+		}
+		last = info.Name
+
+		if info.Package == "" {
+			t.Errorf("Name=%s missing Package", info.Name)
+		}
+		if info.Changed != 0 && info.Old == "" {
+			t.Errorf("Name=%s has Changed, missing Old", info.Name)
+		}
+		if info.Old != "" && info.Changed == 0 {
+			t.Errorf("Name=%s has Old, missing Changed", info.Name)
+		}
+		if !strings.Contains(doc, "`"+info.Name+"`") {
+			t.Errorf("Name=%s not documented in doc/godebug.md", info.Name)
+		}
+	}
+}

src/internal/godebugs/table.go

@@ -0,0 +1,64 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package godebugs provides a table of known GODEBUG settings,
+// for use by a variety of other packages, including internal/godebug,
+// runtime, runtime/metrics, and cmd/go/internal/load.
+package godebugs
+
+// An Info describes a single known GODEBUG setting.
+type Info struct {
+	Name    string // name of the setting ("panicnil")
+	Package string // package that uses the setting ("runtime")
+	Changed int    // minor version when default changed, if any; 21 means Go 1.21
+	Old     string // value that restores behavior prior to Changed
+	Opaque  bool   // setting does not export information to runtime/metrics using [internal/godebug.Setting.IncNonDefault]
+}
+
+// All is the table of known settings, sorted by Name.
+//
+// Note: After adding entries to this table, run 'go generate runtime/metrics'
+// to update the runtime/metrics doc comment.
+// (Otherwise the runtime/metrics test will fail.)
+//
+// Note: After adding entries to this table, update the list in doc/godebug.md as well.
+// (Otherwise the test in this package will fail.)
+var All = []Info{
+	{Name: "execerrdot", Package: "os/exec"},
+	{Name: "http2client", Package: "net/http"},
+	{Name: "http2debug", Package: "net/http", Opaque: true},
+	{Name: "http2server", Package: "net/http"},
+	{Name: "installgoroot", Package: "go/build"},
+	{Name: "jstmpllitinterp", Package: "html/template"},
+	//{Name: "multipartfiles", Package: "mime/multipart"},
+	{Name: "multipartmaxheaders", Package: "mime/multipart"},
+	{Name: "multipartmaxparts", Package: "mime/multipart"},
+	{Name: "netdns", Package: "net", Opaque: true},
+	{Name: "panicnil", Package: "runtime", Changed: 21, Old: "1"},
+	{Name: "randautoseed", Package: "math/rand"},
+	{Name: "tarinsecurepath", Package: "archive/tar"},
+	{Name: "x509sha1", Package: "crypto/x509"},
+	{Name: "x509usefallbackroots", Package: "crypto/x509"},
+	{Name: "zipinsecurepath", Package: "archive/zip"},
+}
+
+// Lookup returns the Info with the given name.
+func Lookup(name string) *Info {
+	// binary search, avoiding import of sort.
+	lo := 0
+	hi := len(All)
+	for lo < hi {
+		m := lo + (hi-lo)>>1
+		mid := All[m].Name
+		if name == mid {
+			return &All[m]
+		}
+		if name < mid {
+			hi = m
+		} else {
+			lo = m + 1
+		}
+	}
+	return nil
+}

src/internal/intern/intern.go

@@ -66,7 +66,7 @@ var (
 	valSafe = safeMap()         // non-nil in safe+leaky mode
 )
 
-var intern = godebug.New("intern")
+var intern = godebug.New("#intern")
 
 // safeMap returns a non-nil map if we're in safe-but-leaky mode,
 // as controlled by GODEBUG=intern=leaky

src/mime/multipart/formdata.go

@@ -34,7 +34,7 @@ func (r *Reader) ReadForm(maxMemory int64) (*Form, error) {
 }
 
 var (
-	multipartFiles    = godebug.New("multipartfiles")
+	multipartFiles    = godebug.New("#multipartfiles") // TODO: document and remove #
 	multipartMaxParts = godebug.New("multipartmaxparts")
 )
 
@@ -48,7 +48,7 @@ func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) {
 	combineFiles := true
 	if multipartFiles.Value() == "distinct" {
 		combineFiles = false
-		multipartFiles.IncNonDefault()
+		// multipartFiles.IncNonDefault() // TODO: uncomment after documenting
 	}
 	maxParts := 1000
 	if s := multipartMaxParts.Value(); s != "" {

src/os/exec/exec.go

@@ -348,7 +348,7 @@ type ctxResult struct {
 	timer *time.Timer
 }
 
-var execwait = godebug.New("execwait")
+var execwait = godebug.New("#execwait")
 var execerrdot = godebug.New("execerrdot")
 
 // Command returns the Cmd struct to execute the named program with

src/runtime/metrics.go

@@ -7,6 +7,7 @@ package runtime
 // Metrics implementation exported to runtime/metrics.
 
 import (
+	"internal/godebugs"
 	"unsafe"
 )
 
@@ -286,20 +287,6 @@ func initMetrics() {
 				out.scalar = uint64(startingStackSize)
 			},
 		},
-		"/godebug/non-default-behavior/execerrdot:events":           {compute: compute0},
-		"/godebug/non-default-behavior/http2client:events":          {compute: compute0},
-		"/godebug/non-default-behavior/http2server:events":          {compute: compute0},
-		"/godebug/non-default-behavior/installgoroot:events":        {compute: compute0},
-		"/godebug/non-default-behavior/jstmpllitinterp:events":      {compute: compute0},
-		"/godebug/non-default-behavior/multipartfiles:events":       {compute: compute0},
-		"/godebug/non-default-behavior/multipartmaxheaders:events":  {compute: compute0},
-		"/godebug/non-default-behavior/multipartmaxparts:events":    {compute: compute0},
-		"/godebug/non-default-behavior/panicnil:events":             {compute: compute0},
-		"/godebug/non-default-behavior/randautoseed:events":         {compute: compute0},
-		"/godebug/non-default-behavior/tarinsecurepath:events":      {compute: compute0},
-		"/godebug/non-default-behavior/x509sha1:events":             {compute: compute0},
-		"/godebug/non-default-behavior/x509usefallbackroots:events": {compute: compute0},
-		"/godebug/non-default-behavior/zipinsecurepath:events":      {compute: compute0},
 		"/memory/classes/heap/free:bytes": {
 			deps: makeStatDepSet(heapStatsDep),
 			compute: func(in *statAggregate, out *metricValue) {
@@ -432,6 +419,13 @@ func initMetrics() {
 			},
 		},
 	}
+
+	for _, info := range godebugs.All {
+		if !info.Opaque {
+			metrics["/godebug/non-default-behavior/"+info.Name+":events"] = metricData{compute: compute0}
+		}
+	}
+
 	metricsInit = true
 }
 
@@ -447,10 +441,6 @@ func (f metricReader) compute(_ *statAggregate, out *metricValue) {
 	out.scalar = f()
 }
 
-var godebugNonDefaults = []string{
-	"panicnil",
-}
-
 //go:linkname godebug_registerMetric internal/godebug.registerMetric
 func godebug_registerMetric(name string, read func() uint64) {
 	metricsLock()

src/runtime/metrics/description.go

@@ -4,6 +4,8 @@
 
 package metrics
 
+import "internal/godebugs"
+
 // Description describes a runtime metric.
 type Description struct {
 	// Name is the full name of the metric which includes the unit.
@@ -49,7 +51,7 @@ type Description struct {
 }
 
 // The English language descriptions below must be kept in sync with the
-// descriptions of each metric in doc.go.
+// descriptions of each metric in doc.go by running 'go generate'.
 var allDesc = []Description{
 	{
 		Name:        "/cgo/go-to-c-calls:calls",
@@ -277,104 +279,6 @@ var allDesc = []Description{
 		Kind:        KindUint64,
 		Cumulative:  false,
 	},
-	{
-		Name: "/godebug/non-default-behavior/execerrdot:events",
-		Description: "The number of non-default behaviors executed by the os/exec package " +
-			"due to a non-default GODEBUG=execerrdot=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/http2client:events",
-		Description: "The number of non-default behaviors executed by the net/http package " +
-			"due to a non-default GODEBUG=http2client=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/http2server:events",
-		Description: "The number of non-default behaviors executed by the net/http package " +
-			"due to a non-default GODEBUG=http2server=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/installgoroot:events",
-		Description: "The number of non-default behaviors executed by the go/build package " +
-			"due to a non-default GODEBUG=installgoroot=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/jstmpllitinterp:events",
-		Description: "The number of non-default behaviors executed by the html/template" +
-			"package due to a non-default GODEBUG=jstmpllitinterp=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/multipartfiles:events",
-		Description: "The number of non-default behaviors executed by the mime/multipart package " +
-			"due to a non-default GODEBUG=multipartfiles=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/multipartmaxheaders:events",
-		Description: "The number of non-default behaviors executed by the mime/multipart package " +
-			"due to a non-default GODEBUG=multipartmaxheaders=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/multipartmaxparts:events",
-		Description: "The number of non-default behaviors executed by the mime/multipart package " +
-			"due to a non-default GODEBUG=multipartmaxparts=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/panicnil:events",
-		Description: "The number of non-default behaviors executed by the runtime package " +
-			"due to a non-default GODEBUG=panicnil=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/randautoseed:events",
-		Description: "The number of non-default behaviors executed by the math/rand package " +
-			"due to a non-default GODEBUG=randautoseed=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/tarinsecurepath:events",
-		Description: "The number of non-default behaviors executed by the archive/tar package " +
-			"due to a non-default GODEBUG=tarinsecurepath=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/x509sha1:events",
-		Description: "The number of non-default behaviors executed by the crypto/x509 package " +
-			"due to a non-default GODEBUG=x509sha1=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/x509usefallbackroots:events",
-		Description: "The number of non-default behaviors executed by the crypto/x509 package " +
-			"due to a non-default GODEBUG=x509usefallbackroots=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
-	{
-		Name: "/godebug/non-default-behavior/zipinsecurepath:events",
-		Description: "The number of non-default behaviors executed by the archive/zip package " +
-			"due to a non-default GODEBUG=zipinsecurepath=... setting.",
-		Kind:       KindUint64,
-		Cumulative: true,
-	},
 	{
 		Name: "/memory/classes/heap/free:bytes",
 		Description: "Memory that is completely free and eligible to be returned to the underlying system, " +
@@ -472,6 +376,30 @@ var allDesc = []Description{
 	},
 }
 
+func init() {
+	// Insert all the the non-default-reporting GODEBUGs into the table,
+	// preserving the overall sort order.
+	i := 0
+	for i < len(allDesc) && allDesc[i].Name < "/godebug/" {
+		i++
+	}
+	more := make([]Description, i, len(allDesc)+len(godebugs.All))
+	copy(more, allDesc)
+	for _, info := range godebugs.All {
+		if !info.Opaque {
+			more = append(more, Description{
+				Name: "/godebug/non-default-behavior/" + info.Name + ":events",
+				Description: "The number of non-default behaviors executed by the " +
+					info.Package + " package " + "due to a non-default " +
+					"GODEBUG=" + info.Name + "=... setting.",
+				Kind:       KindUint64,
+				Cumulative: true,
+			})
+		}
+	}
+	allDesc = append(more, allDesc[i:]...)
+}
+
 // All returns a slice of containing metric descriptions for all supported metrics.
 func All() []Description {
 	return allDesc

src/runtime/metrics/doc.go

@@ -221,14 +221,9 @@ Below is the full list of supported metrics, ordered lexicographically.
 
 	/godebug/non-default-behavior/jstmpllitinterp:events
 		The number of non-default behaviors executed by
-		the html/templatepackage due to a non-default
+		the html/template package due to a non-default
 		GODEBUG=jstmpllitinterp=... setting.
 
-	/godebug/non-default-behavior/multipartfiles:events
-		The number of non-default behaviors executed by
-		the mime/multipart package due to a non-default
-		GODEBUG=multipartfiles=... setting.
-
 	/godebug/non-default-behavior/multipartmaxheaders:events
 		The number of non-default behaviors executed by
 		the mime/multipart package due to a non-default