flag: add Duration flag type.

This works in the expected way: flag.Duration returns a *time.Duration,
and uses time.ParseDuration for parsing the input.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5489113

src/pkg/flag/flag.go

@@ -65,12 +65,13 @@ import (
 	"os"
 	"sort"
 	"strconv"
+	"time"
 )
 
 // ErrHelp is the error returned if the flag -help is invoked but no such flag is defined.
 var ErrHelp = errors.New("flag: help requested")
 
-// -- Bool Value
+// -- bool Value
 type boolValue bool
 
 func newBoolValue(val bool, p *bool) *boolValue {
@@ -86,7 +87,7 @@ func (b *boolValue) Set(s string) bool {
 
 func (b *boolValue) String() string { return fmt.Sprintf("%v", *b) }
 
-// -- Int Value
+// -- int Value
 type intValue int
 
 func newIntValue(val int, p *int) *intValue {
@@ -102,7 +103,7 @@ func (i *intValue) Set(s string) bool {
 
 func (i *intValue) String() string { return fmt.Sprintf("%v", *i) }
 
-// -- Int64 Value
+// -- int64 Value
 type int64Value int64
 
 func newInt64Value(val int64, p *int64) *int64Value {
@@ -118,7 +119,7 @@ func (i *int64Value) Set(s string) bool {
 
 func (i *int64Value) String() string { return fmt.Sprintf("%v", *i) }
 
-// -- Uint Value
+// -- uint Value
 type uintValue uint
 
 func newUintValue(val uint, p *uint) *uintValue {
@@ -165,7 +166,7 @@ func (s *stringValue) Set(val string) bool {
 
 func (s *stringValue) String() string { return fmt.Sprintf("%s", *s) }
 
-// -- Float64 Value
+// -- float64 Value
 type float64Value float64
 
 func newFloat64Value(val float64, p *float64) *float64Value {
@@ -181,6 +182,22 @@ func (f *float64Value) Set(s string) bool {
 
 func (f *float64Value) String() string { return fmt.Sprintf("%v", *f) }
 
+// -- time.Duration Value
+type durationValue time.Duration
+
+func newDurationValue(val time.Duration, p *time.Duration) *durationValue {
+	*p = val
+	return (*durationValue)(p)
+}
+
+func (d *durationValue) Set(s string) bool {
+	v, err := time.ParseDuration(s)
+	*d = durationValue(v)
+	return err == nil
+}
+
+func (d *durationValue) String() string { return (*time.Duration)(d).String() }
+
 // Value is the interface to the dynamic value stored in a flag.
 // (The default value is represented as a string.)
 type Value interface {
@@ -543,12 +560,38 @@ func (f *FlagSet) Float64(name string, value float64, usage string) *float64 {
 	return p
 }
 
-// Float64 defines an int flag with specified name, default value, and usage string.
+// Float64 defines a float64 flag with specified name, default value, and usage string.
 // The return value is the address of a float64 variable that stores the value of the flag.
 func Float64(name string, value float64, usage string) *float64 {
 	return commandLine.Float64(name, value, usage)
 }
 
+// DurationVar defines a time.Duration flag with specified name, default value, and usage string.
+// The argument p points to a time.Duration variable in which to store the value of the flag.
+func (f *FlagSet) DurationVar(p *time.Duration, name string, value time.Duration, usage string) {
+	f.Var(newDurationValue(value, p), name, usage)
+}
+
+// DurationVar defines a time.Duration flag with specified name, default value, and usage string.
+// The argument p points to a time.Duration variable in which to store the value of the flag.
+func DurationVar(p *time.Duration, name string, value time.Duration, usage string) {
+	commandLine.Var(newDurationValue(value, p), name, usage)
+}
+
+// Duration defines a time.Duration flag with specified name, default value, and usage string.
+// The return value is the address of a time.Duration variable that stores the value of the flag.
+func (f *FlagSet) Duration(name string, value time.Duration, usage string) *time.Duration {
+	p := new(time.Duration)
+	f.DurationVar(p, name, value, usage)
+	return p
+}
+
+// Duration defines a time.Duration flag with specified name, default value, and usage string.
+// The return value is the address of a time.Duration variable that stores the value of the flag.
+func Duration(name string, value time.Duration, usage string) *time.Duration {
+	return commandLine.Duration(name, value, usage)
+}
+
 // Var defines a flag with the specified name and usage string. The type and
 // value of the flag are represented by the first argument, of type Value, which
 // typically holds a user-defined implementation of Value. For instance, the

src/pkg/flag/flag_test.go

@@ -10,16 +10,18 @@ import (
 	"os"
 	"sort"
 	"testing"
+	"time"
 )
 
 var (
-	test_bool    = Bool("test_bool", false, "bool value")
-	test_int     = Int("test_int", 0, "int value")
-	test_int64   = Int64("test_int64", 0, "int64 value")
-	test_uint    = Uint("test_uint", 0, "uint value")
-	test_uint64  = Uint64("test_uint64", 0, "uint64 value")
-	test_string  = String("test_string", "0", "string value")
-	test_float64 = Float64("test_float64", 0, "float64 value")
+	test_bool     = Bool("test_bool", false, "bool value")
+	test_int      = Int("test_int", 0, "int value")
+	test_int64    = Int64("test_int64", 0, "int64 value")
+	test_uint     = Uint("test_uint", 0, "uint value")
+	test_uint64   = Uint64("test_uint64", 0, "uint64 value")
+	test_string   = String("test_string", "0", "string value")
+	test_float64  = Float64("test_float64", 0, "float64 value")
+	test_duration = Duration("test_duration", 0, "time.Duration value")
 )
 
 func boolString(s string) string {
@@ -41,6 +43,8 @@ func TestEverything(t *testing.T) {
 				ok = true
 			case f.Name == "test_bool" && f.Value.String() == boolString(desired):
 				ok = true
+			case f.Name == "test_duration" && f.Value.String() == desired+"s":
+				ok = true
 			}
 			if !ok {
 				t.Error("Visit: bad value", f.Value.String(), "for", f.Name)
@@ -48,7 +52,7 @@ func TestEverything(t *testing.T) {
 		}
 	}
 	VisitAll(visitor)
-	if len(m) != 7 {
+	if len(m) != 8 {
 		t.Error("VisitAll misses some flags")
 		for k, v := range m {
 			t.Log(k, *v)
@@ -70,9 +74,10 @@ func TestEverything(t *testing.T) {
 	Set("test_uint64", "1")
 	Set("test_string", "1")
 	Set("test_float64", "1")
+	Set("test_duration", "1s")
 	desired = "1"
 	Visit(visitor)
-	if len(m) != 7 {
+	if len(m) != 8 {
 		t.Error("Visit fails after set")
 		for k, v := range m {
 			t.Log(k, *v)
@@ -109,6 +114,7 @@ func testParse(f *FlagSet, t *testing.T) {
 	uint64Flag := f.Uint64("uint64", 0, "uint64 value")
 	stringFlag := f.String("string", "0", "string value")
 	float64Flag := f.Float64("float64", 0, "float64 value")
+	durationFlag := f.Duration("duration", 5*time.Second, "time.Duration value")
 	extra := "one-extra-argument"
 	args := []string{
 		"-bool",
@@ -119,6 +125,7 @@ func testParse(f *FlagSet, t *testing.T) {
 		"--uint64", "25",
 		"-string", "hello",
 		"-float64", "2718e28",
+		"-duration", "2m",
 		extra,
 	}
 	if err := f.Parse(args); err != nil {
@@ -151,6 +158,9 @@ func testParse(f *FlagSet, t *testing.T) {
 	if *float64Flag != 2718e28 {
 		t.Error("float64 flag should be 2718e28, is ", *float64Flag)
 	}
+	if *durationFlag != 2*time.Minute {
+		t.Error("duration flag should be 2m, is ", *durationFlag)
+	}
 	if len(f.Args()) != 1 {
 		t.Error("expected one argument, got", len(f.Args()))
 	} else if f.Args()[0] != extra {