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parser.go
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parser.go
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// Copyright 2017-2021 The Usacloud Authors
//
// 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 clitag
import (
"errors"
"fmt"
"reflect"
"github.com/sacloud/usacloud/pkg/naming"
)
// DefaultTagName ftagのデフォルト名
const DefaultTagName = "cli"
// ParserConfig パーサ設定
type ParserConfig struct {
TagName string
OptionsMap map[string][]string // 指定可能な値(オプション)参照用のマップ
}
// Parser ftagのパーサー
type Parser struct {
Config *ParserConfig
}
var DefaultParser = &Parser{Config: &ParserConfig{TagName: DefaultTagName}}
// Parse デフォルトのParser(タグ名:cli)でftagをパースする
func Parse(v interface{}) ([]StructField, error) {
return DefaultParser.Parse(v)
}
// Parse ftagをパースする
func (p *Parser) Parse(v interface{}) ([]StructField, error) {
if v == nil {
return nil, errors.New("value required")
}
rv := reflect.ValueOf(v)
switch rv.Kind() {
case reflect.Ptr:
return p.Parse(rv.Elem().Interface()) // dereference pointer
case reflect.Struct:
return p.ParseFields(StructField{}, reflect.TypeOf(v))
default:
return nil, fmt.Errorf("unsupported value: %#v", v)
}
}
func (p *Parser) ParseFields(parent StructField, tp reflect.Type) ([]StructField, error) {
var fields []StructField
for i := 0; i < tp.NumField(); i++ {
f := tp.Field(i)
if f.PkgPath == "" { // exported?
parsed, err := p.ParseField(parent, f)
if err != nil {
return nil, err
}
fields = append(fields, parsed...)
}
}
return fields, nil
}
func (p *Parser) ParseField(parent StructField, f reflect.StructField) ([]StructField, error) {
tag, err := p.parseTag(f.Tag.Get(p.Config.TagName))
if err != nil {
return nil, err
}
if tag.Ignore {
return nil, err
}
// handle tag values
if tag.FlagName == "" {
tag.FlagName = naming.ToKebabCase(f.Name)
}
if tag.FieldName == "" {
tag.FieldName = f.Name
}
if !tag.Squash {
if parent.FlagName != "" && tag.FlagName != "" {
tag.FlagName = fmt.Sprintf("%s-%s", parent.FlagName, tag.FlagName)
}
parent.FlagName = tag.FlagName
}
if !f.Anonymous {
if parent.FieldName != "" && tag.FieldName != "" {
tag.FieldName = fmt.Sprintf("%s.%s", parent.FieldName, tag.FieldName)
}
parent.FieldName = tag.FieldName
}
// inherits parent category if empty
if tag.Category == "" {
tag.Category = parent.Category
}
parent.Category = tag.Category
kind := f.Type.Kind()
switch kind {
case reflect.Ptr:
if f.Type.Elem().Kind() == reflect.Struct {
return p.ParseFields(parent, f.Type.Elem())
}
case reflect.Struct:
return p.ParseFields(parent, f.Type)
}
return []StructField{{StructField: f, Tag: tag}}, nil
}