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/*
* flag.go - Definitions for flags and associated formatting functions.
*
* Copyright 2017 Google Inc.
* Author: Joe Richey (joerichey@google.com)
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package cmd
import (
"flag"
"fmt"
"strconv"
"time"
)
// Flag represents a flag that can be passed to a command. The Name, ArgName,
// and Usage are used to format and display the flag.
type Flag interface {
// String formats the flag as either "--name" or "--name=<argName>".
fmt.Stringer
// FullUsage is the usage for this flag with an optional default note.
FullUsage() string
// Apply sets up this flag on a flag set.
Apply(*flag.FlagSet)
}
// Formats as "--name" or as "--name=<argName>" if argName is present.
func formatHelper(name, argName string) string {
if argName != "" {
return fmt.Sprintf("--%s=<%s>", name, argName)
}
return fmt.Sprintf("--%s", name)
}
// Appends (default: <default>) to the usage if defaultString is present.
func usageHelper(usage, defaultString string) string {
if defaultString != "" {
usage += fmt.Sprintf(" (default: %s)", defaultString)
}
return usage
}
// BoolFlag is a Flag of type bool.
type BoolFlag struct {
Name string
Usage string
Default bool
Value bool
}
// String always uses the smaller format, as it has no ArgName.
func (f *BoolFlag) String() string { return formatHelper(f.Name, "") }
// FullUsage shows the default if it's true (flag is implicitly passed).
func (f *BoolFlag) FullUsage() string {
if !f.Default {
return usageHelper(f.Usage, "")
}
return usageHelper(f.Usage, "true")
}
// Apply uses BoolFlag's value to set a flag.BoolVar on the FlagSet.
func (f *BoolFlag) Apply(s *flag.FlagSet) { s.BoolVar(&f.Value, f.Name, f.Default, f.Usage) }
// StringFlag is a Flag of type string.
type StringFlag struct {
Name string
ArgName string
Usage string
Default string
Value string
}
func (f *StringFlag) String() string { return formatHelper(f.Name, f.ArgName) }
// FullUsage shows the deafult if the string is non-empty.
func (f *StringFlag) FullUsage() string {
if f.Default == "" {
return usageHelper(f.Usage, "")
}
return usageHelper(f.Usage, strconv.Quote(f.Default))
}
// Apply uses StringFlag's value to set a flag.StringVar on the FlagSet.
func (f *StringFlag) Apply(s *flag.FlagSet) { s.StringVar(&f.Value, f.Name, f.Default, f.Usage) }
// DurationFlag is a Flag of type time.Duration.
type DurationFlag struct {
Name string
ArgName string
Usage string
Default time.Duration
Value time.Duration
}
func (f *DurationFlag) String() string { return formatHelper(f.Name, f.ArgName) }
// FullUsage shows the default if the duration is non-zero.
func (f *DurationFlag) FullUsage() string {
if f.Default == 0 {
return usageHelper(f.Usage, "")
}
return usageHelper(f.Usage, f.Default.String())
}
// Apply uses DurationFlag's value to set a flag.DurationVar on the FlagSet.
func (f *DurationFlag) Apply(s *flag.FlagSet) { s.DurationVar(&f.Value, f.Name, f.Default, f.Usage) }
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