source: code/trunk/vendor/github.com/golang/protobuf/proto/defaults.go@ 823

// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package proto

import (
        "google.golang.org/protobuf/reflect/protoreflect"
)

// SetDefaults sets unpopulated scalar fields to their default values.
// Fields within a oneof are not set even if they have a default value.
// SetDefaults is recursively called upon any populated message fields.
func SetDefaults(m Message) {
        if m != nil {
                setDefaults(MessageReflect(m))
        }
}

func setDefaults(m protoreflect.Message) {
        fds := m.Descriptor().Fields()
        for i := 0; i < fds.Len(); i++ {
                fd := fds.Get(i)
                if !m.Has(fd) {
                        if fd.HasDefault() && fd.ContainingOneof() == nil {
                                v := fd.Default()
                                if fd.Kind() == protoreflect.BytesKind {
                                        v = protoreflect.ValueOf(append([]byte(nil), v.Bytes()...)) // copy the default bytes
                                }
                                m.Set(fd, v)
                        }
                        continue
                }
        }

        m.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
                switch {
                // Handle singular message.
                case fd.Cardinality() != protoreflect.Repeated:
                        if fd.Message() != nil {
                                setDefaults(m.Get(fd).Message())
                        }
                // Handle list of messages.
                case fd.IsList():
                        if fd.Message() != nil {
                                ls := m.Get(fd).List()
                                for i := 0; i < ls.Len(); i++ {
                                        setDefaults(ls.Get(i).Message())
                                }
                        }
                // Handle map of messages.
                case fd.IsMap():
                        if fd.MapValue().Message() != nil {
                                ms := m.Get(fd).Map()
                                ms.Range(func(_ protoreflect.MapKey, v protoreflect.Value) bool {
                                        setDefaults(v.Message())
                                        return true
                                })
                        }
                }
                return true
        })
}