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defaulter.go
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defaulter.go
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// Copyright 2021 Chaos Mesh 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 genericwebhook
import (
"reflect"
"strings"
"k8s.io/apimachinery/pkg/util/validation/field"
)
type Defaulter interface {
Default(root interface{}, field *reflect.StructField)
}
// Default would walk through all the fields of target struct recursively, and set the default value which declared with struct tag "default".
//
// Parameter obj should be a pointer to a data struct.
//
// Default should return an empty field.ErrorList.
func Default(obj interface{}) field.ErrorList {
// TODO: how to resolve invalid input, for example: obj is a pointer to pointer
errorList := field.ErrorList{}
root := obj
walker := NewFieldWalker(obj, func(path *field.Path, obj interface{}, field *reflect.StructField) bool {
webhookAttr := ""
if field != nil {
webhookAttr = field.Tag.Get("webhook")
}
attributes := strings.Split(webhookAttr, ",")
webhook := ""
nilable := false
if len(attributes) > 0 {
webhook = attributes[0]
}
if len(attributes) > 1 {
nilable = attributes[1] == "nilable"
}
defaulter := getDefaulter(obj, webhook, nilable)
if defaulter != nil {
defaulter.Default(root, field)
}
return true
})
walker.Walk()
return errorList
}
func getDefaulter(obj interface{}, webhook string, nilable bool) Defaulter {
// There are two possible situations:
// 1. The field is a value (int, string, normal struct, etc), and the obj is the reference of it.
// 2. The field is a pointer to a value or a slice, then the obj is itself.
val := reflect.ValueOf(obj)
if defaulter, ok := obj.(Defaulter); ok {
if nilable || !val.IsZero() {
return defaulter
}
}
if webhook != "" {
webhookImpl := webhooks[webhook]
v := val.Convert(webhookImpl).Interface()
if defaulter, ok := v.(Defaulter); ok {
if nilable || !val.IsZero() {
return defaulter
}
}
}
return nil
}