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Flags: add user-defined flag types. The change is really no code; it's just publishing

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the set() method and add() functions.  But we rename add() to Var() for consistency.
Also rename FlagValue to Value for simplicity.

Also, delete the check for multiple settings for a flag.  This makes it possible to
define a flag that collects values, such as into a slice of strings.

type flagVar []string

func (f *flagVar) String() string {
	return fmt.Sprint(v)
}

func (f *flagVar) Set(value string) bool {
	if v == nil {
		v = make(flagVar, 1)
	} else {
		nv := make(flagVar, len(v)+1)
		copy(nv, v)
		v = nv
	}
	v[len(v)-1] = value
	return true
}

var v flagVar

func main() {
	flag.Var(&v, "testV", "multiple values build []string")
	flag.Parse()
	fmt.Printf("v = %v\n", v)
}

R=rsc
CC=golang-dev
https://golang.org/cl/842041
This commit is contained in:
Rob Pike 2010-03-29 17:37:22 -07:00
parent d99a3da7b2
commit 570af81e19
2 changed files with 64 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

84
src/pkg/flag/flag.go
View File

@ -15,6 +15,10 @@
func init() {
flag.IntVar(&flagvar, "flagname", 1234, "help message for flagname")
}
Or you can create custom flags that satisfy the Value interface (with
pointer receivers) and couple them to flag parsing by
flag.Var(&flagVal, "name", "help message for flagname")
For such flags, the default value is just the initial value of the variable.
2) After all flags are defined, call
flag.Parse()
@ -63,7 +67,7 @@ func newBoolValue(val bool, p *bool) *boolValue {
return &boolValue{p}
}
func (b *boolValue) set(s string) bool {
func (b *boolValue) Set(s string) bool {
v, err := strconv.Atob(s)
*b.p = v
return err == nil
@ -81,7 +85,7 @@ func newIntValue(val int, p *int) *intValue {
return &intValue{p}
}
func (i *intValue) set(s string) bool {
func (i *intValue) Set(s string) bool {
v, err := strconv.Atoi(s)
*i.p = int(v)
return err == nil
@ -99,7 +103,7 @@ func newInt64Value(val int64, p *int64) *int64Value {
return &int64Value{p}
}
func (i *int64Value) set(s string) bool {
func (i *int64Value) Set(s string) bool {
v, err := strconv.Atoi64(s)
*i.p = v
return err == nil
@ -117,7 +121,7 @@ func newUintValue(val uint, p *uint) *uintValue {
return &uintValue{p}
}
func (i *uintValue) set(s string) bool {
func (i *uintValue) Set(s string) bool {
v, err := strconv.Atoui(s)
*i.p = uint(v)
return err == nil
@ -135,7 +139,7 @@ func newUint64Value(val uint64, p *uint64) *uint64Value {
return &uint64Value{p}
}
func (i *uint64Value) set(s string) bool {
func (i *uint64Value) Set(s string) bool {
v, err := strconv.Atoui64(s)
*i.p = uint64(v)
return err == nil
@ -153,7 +157,7 @@ func newStringValue(val string, p *string) *stringValue {
return &stringValue{p}
}
func (s *stringValue) set(val string) bool {
func (s *stringValue) Set(val string) bool {
*s.p = val
return true
}
@ -170,7 +174,7 @@ func newFloatValue(val float, p *float) *floatValue {
return &floatValue{p}
}
func (f *floatValue) set(s string) bool {
func (f *floatValue) Set(s string) bool {
v, err := strconv.Atof(s)
*f.p = v
return err == nil
@ -188,7 +192,7 @@ func newFloat64Value(val float64, p *float64) *float64Value {
return &float64Value{p}
}
func (f *float64Value) set(s string) bool {
func (f *float64Value) Set(s string) bool {
v, err := strconv.Atof64(s)
*f.p = v
return err == nil
@ -196,18 +200,18 @@ func (f *float64Value) set(s string) bool {
func (f *float64Value) String() string { return fmt.Sprintf("%v", *f.p) }
// FlagValue is the interface to the dynamic value stored in a flag.
// Value is the interface to the dynamic value stored in a flag.
// (The default value is represented as a string.)
type FlagValue interface {
type Value interface {
String() string
set(string) bool
Set(string) bool
}
// A Flag represents the state of a flag.
type Flag struct {
Name string // name as it appears on command line
Usage string // help message
Value FlagValue // value as set
Value Value // value as set
DefValue string // default value (as text); for usage message
}
@ -249,7 +253,7 @@ func Set(name, value string) bool {
if !ok {
return false
}
ok = f.Value.set(value)
ok = f.Value.Set(value)
if !ok {
return false
}
@ -294,21 +298,10 @@ func NArg() int { return len(os.Args) - flags.first_arg }
// Args returns the non-flag command-line arguments.
func Args() []string { return os.Args[flags.first_arg:] }
func add(name string, value FlagValue, usage string) {
// Remember the default value as a string; it won't change.
f := &Flag{name, usage, value, value.String()}
_, alreadythere := flags.formal[name]
if alreadythere {
fmt.Fprintln(os.Stderr, "flag redefined:", name)
panic("flag redefinition") // Happens only if flags are declared with identical names
}
flags.formal[name] = f
}
// BoolVar defines a bool flag with specified name, default value, and usage string.
// The argument p points to a bool variable in which to store the value of the flag.
func BoolVar(p *bool, name string, value bool, usage string) {
add(name, newBoolValue(value, p), usage)
Var(newBoolValue(value, p), name, usage)
}
// Bool defines a bool flag with specified name, default value, and usage string.
@ -322,7 +315,7 @@ func Bool(name string, value bool, usage string) *bool {
// IntVar defines an int flag with specified name, default value, and usage string.
// The argument p points to an int variable in which to store the value of the flag.
func IntVar(p *int, name string, value int, usage string) {
add(name, newIntValue(value, p), usage)
Var(newIntValue(value, p), name, usage)
}
// Int defines an int flag with specified name, default value, and usage string.
@ -336,7 +329,7 @@ func Int(name string, value int, usage string) *int {
// Int64Var defines an int64 flag with specified name, default value, and usage string.
// The argument p points to an int64 variable in which to store the value of the flag.
func Int64Var(p *int64, name string, value int64, usage string) {
add(name, newInt64Value(value, p), usage)
Var(newInt64Value(value, p), name, usage)
}
// Int64 defines an int64 flag with specified name, default value, and usage string.
@ -350,7 +343,7 @@ func Int64(name string, value int64, usage string) *int64 {
// UintVar defines a uint flag with specified name, default value, and usage string.
// The argument p points to a uint variable in which to store the value of the flag.
func UintVar(p *uint, name string, value uint, usage string) {
add(name, newUintValue(value, p), usage)
Var(newUintValue(value, p), name, usage)
}
// Uint defines a uint flag with specified name, default value, and usage string.
@ -364,7 +357,7 @@ func Uint(name string, value uint, usage string) *uint {
// Uint64Var defines a uint64 flag with specified name, default value, and usage string.
// The argument p points to a uint64 variable in which to store the value of the flag.
func Uint64Var(p *uint64, name string, value uint64, usage string) {
add(name, newUint64Value(value, p), usage)
Var(newUint64Value(value, p), name, usage)
}
// Uint64 defines a uint64 flag with specified name, default value, and usage string.
@ -378,7 +371,7 @@ func Uint64(name string, value uint64, usage string) *uint64 {
// StringVar defines a string flag with specified name, default value, and usage string.
// The argument p points to a string variable in which to store the value of the flag.
func StringVar(p *string, name, value string, usage string) {
add(name, newStringValue(value, p), usage)
Var(newStringValue(value, p), name, usage)
}
// String defines a string flag with specified name, default value, and usage string.
@ -392,7 +385,7 @@ func String(name, value string, usage string) *string {
// FloatVar defines a float flag with specified name, default value, and usage string.
// The argument p points to a float variable in which to store the value of the flag.
func FloatVar(p *float, name string, value float, usage string) {
add(name, newFloatValue(value, p), usage)
Var(newFloatValue(value, p), name, usage)
}
// Float defines a float flag with specified name, default value, and usage string.
@ -406,7 +399,7 @@ func Float(name string, value float, usage string) *float {
// Float64Var defines a float64 flag with specified name, default value, and usage string.
// The argument p points to a float64 variable in which to store the value of the flag.
func Float64Var(p *float64, name string, value float64, usage string) {
add(name, newFloat64Value(value, p), usage)
Var(newFloat64Value(value, p), name, usage)
}
// Float64 defines a float64 flag with specified name, default value, and usage string.
@ -417,6 +410,19 @@ func Float64(name string, value float64, usage string) *float64 {
return p
}
// Var defines a user-typed flag with specified name, default value, and usage string.
// The argument p points to a Value variable in which to store the value of the flag.
func Var(value Value, name string, usage string) {
// Remember the default value as a string; it won't change.
f := &Flag{name, usage, value, value.String()}
_, alreadythere := flags.formal[name]
if alreadythere {
fmt.Fprintln(os.Stderr, "flag redefined:", name)
panic("flag redefinition") // Happens only if flags are declared with identical names
}
flags.formal[name] = f
}
func (f *allFlags) parseOne(index int) (ok bool, next int) {
s := os.Args[index]
@ -455,14 +461,8 @@ func (f *allFlags) parseOne(index int) (ok bool, next int) {
break
}
}
flag, alreadythere := flags.actual[name]
if alreadythere {
fmt.Fprintf(os.Stderr, "flag specified twice: -%s\n", name)
Usage()
os.Exit(2)
}
m := flags.formal
flag, alreadythere = m[name] // BUG
flag, alreadythere := m[name] // BUG
if !alreadythere {
fmt.Fprintf(os.Stderr, "flag provided but not defined: -%s\n", name)
Usage()
@ -470,13 +470,13 @@ func (f *allFlags) parseOne(index int) (ok bool, next int) {
}
if f, ok := flag.Value.(*boolValue); ok { // special case: doesn't need an arg
if has_value {
if !f.set(value) {
if !f.Set(value) {
fmt.Fprintf(os.Stderr, "invalid boolean value %t for flag: -%s\n", value, name)
Usage()
os.Exit(2)
}
} else {
f.set("true")
f.Set("true")
}
} else {
// It must have a value, which might be the next argument.
@ -491,7 +491,7 @@ func (f *allFlags) parseOne(index int) (ok bool, next int) {
Usage()
os.Exit(2)
}
ok = flag.Value.set(value)
ok = flag.Value.Set(value)
if !ok {
fmt.Fprintf(os.Stderr, "invalid value %s for flag: -%s\n", value, name)
Usage()

19
src/pkg/flag/flag_test.go
View File

@ -78,3 +78,22 @@ func TestEverything(t *testing.T) {
}
}
}
// Declare a user-defined flag.
// TODO: do the work to make this test better by resetting flag state
// and manipulating os.Args.
type flagVar []string
func (f *flagVar) String() string {
return "foo"
}
func (f *flagVar) Set(value string) bool {
return true
}
var v flagVar
func init() {
Var(&v, "testV", "usage")
}