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Modify optional flag to use generics #14645

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Modify optional flag to use generics #14645

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5271832
modify optional flag to use generics
Its-Maniaco Nov 30, 2023
686ad20
Update go/flagutil/optional.go
Its-Maniaco Dec 26, 2023
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100 changes: 29 additions & 71 deletions go/flagutil/optional.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@ package flagutil

import (
"errors"
"fmt"
"reflect"
"strconv"

"github.com/spf13/pflag"
Expand All @@ -37,101 +39,57 @@ type OptionalFlag interface {
IsSet() bool
}

var (
_ OptionalFlag = (*OptionalFloat64)(nil)
_ OptionalFlag = (*OptionalString)(nil)
)

// OptionalFloat64 implements OptionalFlag for float64 values.
type OptionalFloat64 struct {
val float64
type Optional[T any] struct {
val T
set bool
}

// NewOptionalFloat64 returns an OptionalFloat64 with the specified value as its
// starting value.
func NewOptionalFloat64(val float64) *OptionalFloat64 {
return &OptionalFloat64{
func (Optional[T]) NewOptionalType(val T) *Optional[T] {
return &Optional[T]{
val: val,
set: false,
}
}

// Set is part of the pflag.Value interface.
func (f *OptionalFloat64) Set(arg string) error {
v, err := strconv.ParseFloat(arg, 64)
if err != nil {
return numError(err)
func (t *Optional[T]) Set(arg string) error {
var val any
switch kind := reflect.TypeOf(t.val).Kind(); kind {
case reflect.Float64:
num, err := strconv.ParseFloat(arg, 64)
if err != nil {
return numError(err)
}
val = num
case reflect.String:
val = arg
default:
panic(fmt.Sprintf("%v not supported", kind))
}

f.val = v
f.set = true

t.val = val.(T)
t.set = true
return nil
}

// String is part of the pflag.Value interface.
func (f *OptionalFloat64) String() string {
return strconv.FormatFloat(f.val, 'g', -1, 64)
func (t *Optional[T]) String() string {
return fmt.Sprintf("%v", t.val)
}

// Type is part of the pflag.Value interface.
func (f *OptionalFloat64) Type() string {
return "float64"
func (t *Optional[T]) Type() string {
return fmt.Sprintf("%T", t.val)
}

// Get returns the underlying float64 value of this flag. If the flag was not
// explicitly set, this will be the initial value passed to the constructor.
func (f *OptionalFloat64) Get() float64 {
return f.val
}

// IsSet is part of the OptionalFlag interface.
func (f *OptionalFloat64) IsSet() bool {
return f.set
}

// OptionalString implements OptionalFlag for string values.
type OptionalString struct {
val string
set bool
}

// NewOptionalString returns an OptionalString with the specified value as its
// starting value.
func NewOptionalString(val string) *OptionalString {
return &OptionalString{
val: val,
set: false,
}
}

// Set is part of the pflag.Value interface.
func (f *OptionalString) Set(arg string) error {
f.val = arg
f.set = true
return nil
}

// String is part of the pflag.Value interface.
func (f *OptionalString) String() string {
return f.val
}

// Type is part of the pflag.Value interface.
func (f *OptionalString) Type() string {
return "string"
}

// Get returns the underlying string value of this flag. If the flag was not
// explicitly set, this will be the initial value passed to the constructor.
func (f *OptionalString) Get() string {
return f.val
func (t *Optional[T]) Get() T {
return t.val
}

// IsSet is part of the OptionalFlag interface.
func (f *OptionalString) IsSet() bool {
return f.set
func (t *Optional[T]) IsSet() bool {
return t.set
}

// lifted directly from package flag to make the behavior of numeric parsing
Expand Down