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// Copyright 2012 Jesse van den Kieboom. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package flags
import (
"errors"
"reflect"
"strings"
"unicode/utf8"
)
// ErrNotPointerToStruct indicates that a provided data container is not
// a pointer to a struct. Only pointers to structs are valid data containers
// for options.
var ErrNotPointerToStruct = errors.New("provided data is not a pointer to struct")
// Group represents an option group. Option groups can be used to logically
// group options together under a description. Groups are only used to provide
// more structure to options both for the user (as displayed in the help message)
// and for you, since groups can be nested.
type Group struct {
// A short description of the group. The
// short description is primarily used in the built-in generated help
// message
ShortDescription string
// A long description of the group. The long
// description is primarily used to present information on commands
// (Command embeds Group) in the built-in generated help and man pages.
LongDescription string
// The namespace of the group
Namespace string
// If true, the group is not displayed in the help or man page
Hidden bool
// The parent of the group or nil if it has no parent
parent interface{}
// All the options in the group
options []*Option
// All the subgroups
groups []*Group
// Whether the group represents the built-in help group
isBuiltinHelp bool
data interface{}
}
type scanHandler func(reflect.Value, *reflect.StructField) (bool, error)
// AddGroup adds a new group to the command with the given name and data. The
// data needs to be a pointer to a struct from which the fields indicate which
// options are in the group.
func (g *Group) AddGroup(shortDescription string, longDescription string, data interface{}) (*Group, error) {
group := newGroup(shortDescription, longDescription, data)
group.parent = g
if err := group.scan(); err != nil {
return nil, err
}
g.groups = append(g.groups, group)
return group, nil
}
// Groups returns the list of groups embedded in this group.
func (g *Group) Groups() []*Group {
return g.groups
}
// Options returns the list of options in this group.
func (g *Group) Options() []*Option {
return g.options
}
// Find locates the subgroup with the given short description and returns it.
// If no such group can be found Find will return nil. Note that the description
// is matched case insensitively.
func (g *Group) Find(shortDescription string) *Group {
lshortDescription := strings.ToLower(shortDescription)
var ret *Group
g.eachGroup(func(gg *Group) {
if gg != g && strings.ToLower(gg.ShortDescription) == lshortDescription {
ret = gg
}
})
return ret
}
func (g *Group) findOption(matcher func(*Option) bool) (option *Option) {
g.eachGroup(func(g *Group) {
for _, opt := range g.options {
if option == nil && matcher(opt) {
option = opt
}
}
})
return option
}
// FindOptionByLongName finds an option that is part of the group, or any of its
// subgroups, by matching its long name (including the option namespace).
func (g *Group) FindOptionByLongName(longName string) *Option {
return g.findOption(func(option *Option) bool {
return option.LongNameWithNamespace() == longName
})
}
// FindOptionByShortName finds an option that is part of the group, or any of
// its subgroups, by matching its short name.
func (g *Group) FindOptionByShortName(shortName rune) *Option {
return g.findOption(func(option *Option) bool {
return option.ShortName == shortName
})
}
func newGroup(shortDescription string, longDescription string, data interface{}) *Group {
return &Group{
ShortDescription: shortDescription,
LongDescription: longDescription,
data: data,
}
}
func (g *Group) optionByName(name string, namematch func(*Option, string) bool) *Option {
prio := 0
var retopt *Option
g.eachGroup(func(g *Group) {
for _, opt := range g.options {
if namematch != nil && namematch(opt, name) && prio < 4 {
retopt = opt
prio = 4
}
if name == opt.field.Name && prio < 3 {
retopt = opt
prio = 3
}
if name == opt.LongNameWithNamespace() && prio < 2 {
retopt = opt
prio = 2
}
if opt.ShortName != 0 && name == string(opt.ShortName) && prio < 1 {
retopt = opt
prio = 1
}
}
})
return retopt
}
func (g *Group) eachGroup(f func(*Group)) {
f(g)
for _, gg := range g.groups {
gg.eachGroup(f)
}
}
func isStringFalsy(s string) bool {
return s == "" || s == "false" || s == "no" || s == "0"
}
func (g *Group) scanStruct(realval reflect.Value, sfield *reflect.StructField, handler scanHandler) error {
stype := realval.Type()
if sfield != nil {
if ok, err := handler(realval, sfield); err != nil {
return err
} else if ok {
return nil
}
}
for i := 0; i < stype.NumField(); i++ {
field := stype.Field(i)
// PkgName is set only for non-exported fields, which we ignore
if field.PkgPath != "" && !field.Anonymous {
continue
}
mtag := newMultiTag(string(field.Tag))
if err := mtag.Parse(); err != nil {
return err
}
// Skip fields with the no-flag tag
if mtag.Get("no-flag") != "" {
continue
}
// Dive deep into structs or pointers to structs
kind := field.Type.Kind()
fld := realval.Field(i)
if kind == reflect.Struct {
if err := g.scanStruct(fld, &field, handler); err != nil {
return err
}
} else if kind == reflect.Ptr && field.Type.Elem().Kind() == reflect.Struct {
flagCountBefore := len(g.options) + len(g.groups)
if fld.IsNil() {
fld = reflect.New(fld.Type().Elem())
}
if err := g.scanStruct(reflect.Indirect(fld), &field, handler); err != nil {
return err
}
if len(g.options)+len(g.groups) != flagCountBefore {
realval.Field(i).Set(fld)
}
}
longname := mtag.Get("long")
shortname := mtag.Get("short")
// Need at least either a short or long name
if longname == "" && shortname == "" && mtag.Get("ini-name") == "" {
continue
}
short := rune(0)
rc := utf8.RuneCountInString(shortname)
if rc > 1 {
return newErrorf(ErrShortNameTooLong,
"short names can only be 1 character long, not `%s'",
shortname)
} else if rc == 1 {
short, _ = utf8.DecodeRuneInString(shortname)
}
description := mtag.Get("description")
def := mtag.GetMany("default")
optionalValue := mtag.GetMany("optional-value")
valueName := mtag.Get("value-name")
defaultMask := mtag.Get("default-mask")
optional := !isStringFalsy(mtag.Get("optional"))
required := !isStringFalsy(mtag.Get("required"))
choices := mtag.GetMany("choice")
hidden := !isStringFalsy(mtag.Get("hidden"))
option := &Option{
Description: description,
ShortName: short,
LongName: longname,
Default: def,
EnvDefaultKey: mtag.Get("env"),
EnvDefaultDelim: mtag.Get("env-delim"),
OptionalArgument: optional,
OptionalValue: optionalValue,
Required: required,
ValueName: valueName,
DefaultMask: defaultMask,
Choices: choices,
Hidden: hidden,
group: g,
field: field,
value: realval.Field(i),
tag: mtag,
}
if option.isBool() && option.Default != nil {
return newErrorf(ErrInvalidTag,
"boolean flag `%s' may not have default values, they always default to `false' and can only be turned on",
option.shortAndLongName())
}
g.options = append(g.options, option)
}
return nil
}
func (g *Group) checkForDuplicateFlags() *Error {
shortNames := make(map[rune]*Option)
longNames := make(map[string]*Option)
var duplicateError *Error
g.eachGroup(func(g *Group) {
for _, option := range g.options {
if option.LongName != "" {
longName := option.LongNameWithNamespace()
if otherOption, ok := longNames[longName]; ok {
duplicateError = newErrorf(ErrDuplicatedFlag, "option `%s' uses the same long name as option `%s'", option, otherOption)
return
}
longNames[longName] = option
}
if option.ShortName != 0 {
if otherOption, ok := shortNames[option.ShortName]; ok {
duplicateError = newErrorf(ErrDuplicatedFlag, "option `%s' uses the same short name as option `%s'", option, otherOption)
return
}
shortNames[option.ShortName] = option
}
}
})
return duplicateError
}
func (g *Group) scanSubGroupHandler(realval reflect.Value, sfield *reflect.StructField) (bool, error) {
mtag := newMultiTag(string(sfield.Tag))
if err := mtag.Parse(); err != nil {
return true, err
}
subgroup := mtag.Get("group")
if len(subgroup) != 0 {
var ptrval reflect.Value
if realval.Kind() == reflect.Ptr {
ptrval = realval
if ptrval.IsNil() {
ptrval.Set(reflect.New(ptrval.Type()))
}
} else {
ptrval = realval.Addr()
}
description := mtag.Get("description")
group, err := g.AddGroup(subgroup, description, ptrval.Interface())
if err != nil {
return true, err
}
group.Namespace = mtag.Get("namespace")
group.Hidden = mtag.Get("hidden") != ""
return true, nil
}
return false, nil
}
func (g *Group) scanType(handler scanHandler) error {
// Get all the public fields in the data struct
ptrval := reflect.ValueOf(g.data)
if ptrval.Type().Kind() != reflect.Ptr {
panic(ErrNotPointerToStruct)
}
stype := ptrval.Type().Elem()
if stype.Kind() != reflect.Struct {
panic(ErrNotPointerToStruct)
}
realval := reflect.Indirect(ptrval)
if err := g.scanStruct(realval, nil, handler); err != nil {
return err
}
if err := g.checkForDuplicateFlags(); err != nil {
return err
}
return nil
}
func (g *Group) scan() error {
return g.scanType(g.scanSubGroupHandler)
}
func (g *Group) groupByName(name string) *Group {
if len(name) == 0 {
return g
}
return g.Find(name)
}