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// SPDX-FileCopyrightText: 2020 Ethel Morgan
//
// SPDX-License-Identifier: MIT
package flag
import (
"flag"
"fmt"
"os"
)
type (
ErrorHandling = flag.ErrorHandling
ParseFunc func(string) (interface{}, error)
FlagSet struct {
flag.FlagSet
customFlags []func() error
}
)
const (
ContinueOnError = flag.ContinueOnError
ExitOnError = flag.ExitOnError
PanicOnError = flag.PanicOnError
)
func (f *FlagSet) Parse(arguments []string) error {
if err := f.FlagSet.Parse(arguments); err != nil {
return err
}
for _, customFlag := range f.customFlags {
if err := customFlag(); err != nil {
switch f.FlagSet.ErrorHandling() {
case flag.ContinueOnError:
return err
case flag.ExitOnError:
fmt.Fprintf(os.Stdout, "%v\n\n", err)
f.Usage()
os.Exit(2)
case flag.PanicOnError:
panic(err)
}
}
}
return nil
}
func NewFlagSet(name string, handling ErrorHandling) *FlagSet {
return &FlagSet{
FlagSet: *flag.NewFlagSet(name, handling),
}
}
func (f *FlagSet) Custom(flagName, defaultValue, description string, parser ParseFunc) *interface{} {
rawFlag := f.String(flagName, defaultValue, description)
var value interface{}
f.customFlags = append(f.customFlags, func() error {
var err error
value, err = parser(*rawFlag)
if err != nil {
return fmt.Errorf("invalid value %q for flag -%s: %w", *rawFlag, flagName, err)
}
return nil
})
return &value
}
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