Joe Tsai 387873dd53 all: implement support for proto3 optional semantics
In the upcoming 3.12.x release of protoc, the proto3 language will be
amended to support true presence for scalars. This CL adds support
to both the generator and runtime to support these semantics.

Newly added public API:
	protogen.Plugin.SupportedFeatures
	protoreflect.FieldDescriptor.HasPresence
	protoreflect.FieldDescriptor.HasOptionalKeyword
	protoreflect.OneofDescriptor.IsSynthetic

Change-Id: I7c86bf66d0ae56642109beb5f2132184593747ad
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/230698
Reviewed-by: Damien Neil <dneil@google.com>
2020-04-29 20:02:24 +00:00

705 lines
20 KiB
Go

// 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 filedesc
import (
"reflect"
"sync"
"google.golang.org/protobuf/encoding/protowire"
"google.golang.org/protobuf/internal/descopts"
"google.golang.org/protobuf/internal/fieldnum"
"google.golang.org/protobuf/internal/strs"
"google.golang.org/protobuf/proto"
pref "google.golang.org/protobuf/reflect/protoreflect"
)
func (fd *File) lazyRawInit() {
fd.unmarshalFull(fd.builder.RawDescriptor)
fd.resolveMessages()
fd.resolveExtensions()
fd.resolveServices()
}
func (file *File) resolveMessages() {
var depIdx int32
for i := range file.allMessages {
md := &file.allMessages[i]
// Resolve message field dependencies.
for j := range md.L2.Fields.List {
fd := &md.L2.Fields.List[j]
// Weak fields are resolved upon actual use.
if fd.L1.IsWeak {
continue
}
// Resolve message field dependency.
switch fd.L1.Kind {
case pref.EnumKind:
fd.L1.Enum = file.resolveEnumDependency(fd.L1.Enum, listFieldDeps, depIdx)
depIdx++
case pref.MessageKind, pref.GroupKind:
fd.L1.Message = file.resolveMessageDependency(fd.L1.Message, listFieldDeps, depIdx)
depIdx++
}
// Default is resolved here since it depends on Enum being resolved.
if v := fd.L1.Default.val; v.IsValid() {
fd.L1.Default = unmarshalDefault(v.Bytes(), fd.L1.Kind, file, fd.L1.Enum)
}
}
}
}
func (file *File) resolveExtensions() {
var depIdx int32
for i := range file.allExtensions {
xd := &file.allExtensions[i]
// Resolve extension field dependency.
switch xd.L1.Kind {
case pref.EnumKind:
xd.L2.Enum = file.resolveEnumDependency(xd.L2.Enum, listExtDeps, depIdx)
depIdx++
case pref.MessageKind, pref.GroupKind:
xd.L2.Message = file.resolveMessageDependency(xd.L2.Message, listExtDeps, depIdx)
depIdx++
}
// Default is resolved here since it depends on Enum being resolved.
if v := xd.L2.Default.val; v.IsValid() {
xd.L2.Default = unmarshalDefault(v.Bytes(), xd.L1.Kind, file, xd.L2.Enum)
}
}
}
func (file *File) resolveServices() {
var depIdx int32
for i := range file.allServices {
sd := &file.allServices[i]
// Resolve method dependencies.
for j := range sd.L2.Methods.List {
md := &sd.L2.Methods.List[j]
md.L1.Input = file.resolveMessageDependency(md.L1.Input, listMethInDeps, depIdx)
md.L1.Output = file.resolveMessageDependency(md.L1.Output, listMethOutDeps, depIdx)
depIdx++
}
}
}
func (file *File) resolveEnumDependency(ed pref.EnumDescriptor, i, j int32) pref.EnumDescriptor {
r := file.builder.FileRegistry
if r, ok := r.(resolverByIndex); ok {
if ed2 := r.FindEnumByIndex(i, j, file.allEnums, file.allMessages); ed2 != nil {
return ed2
}
}
for i := range file.allEnums {
if ed2 := &file.allEnums[i]; ed2.L0.FullName == ed.FullName() {
return ed2
}
}
if d, _ := r.FindDescriptorByName(ed.FullName()); d != nil {
return d.(pref.EnumDescriptor)
}
return ed
}
func (file *File) resolveMessageDependency(md pref.MessageDescriptor, i, j int32) pref.MessageDescriptor {
r := file.builder.FileRegistry
if r, ok := r.(resolverByIndex); ok {
if md2 := r.FindMessageByIndex(i, j, file.allEnums, file.allMessages); md2 != nil {
return md2
}
}
for i := range file.allMessages {
if md2 := &file.allMessages[i]; md2.L0.FullName == md.FullName() {
return md2
}
}
if d, _ := r.FindDescriptorByName(md.FullName()); d != nil {
return d.(pref.MessageDescriptor)
}
return md
}
func (fd *File) unmarshalFull(b []byte) {
sb := getBuilder()
defer putBuilder(sb)
var enumIdx, messageIdx, extensionIdx, serviceIdx int
var rawOptions []byte
fd.L2 = new(FileL2)
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.FileDescriptorProto_PublicDependency:
fd.L2.Imports[v].IsPublic = true
case fieldnum.FileDescriptorProto_WeakDependency:
fd.L2.Imports[v].IsWeak = true
}
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.FileDescriptorProto_Dependency:
path := sb.MakeString(v)
imp, _ := fd.builder.FileRegistry.FindFileByPath(path)
if imp == nil {
imp = PlaceholderFile(path)
}
fd.L2.Imports = append(fd.L2.Imports, pref.FileImport{FileDescriptor: imp})
case fieldnum.FileDescriptorProto_EnumType:
fd.L1.Enums.List[enumIdx].unmarshalFull(v, sb)
enumIdx++
case fieldnum.FileDescriptorProto_MessageType:
fd.L1.Messages.List[messageIdx].unmarshalFull(v, sb)
messageIdx++
case fieldnum.FileDescriptorProto_Extension:
fd.L1.Extensions.List[extensionIdx].unmarshalFull(v, sb)
extensionIdx++
case fieldnum.FileDescriptorProto_Service:
fd.L1.Services.List[serviceIdx].unmarshalFull(v, sb)
serviceIdx++
case fieldnum.FileDescriptorProto_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
fd.L2.Options = fd.builder.optionsUnmarshaler(&descopts.File, rawOptions)
}
func (ed *Enum) unmarshalFull(b []byte, sb *strs.Builder) {
var rawValues [][]byte
var rawOptions []byte
if !ed.L1.eagerValues {
ed.L2 = new(EnumL2)
}
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.EnumDescriptorProto_Value:
rawValues = append(rawValues, v)
case fieldnum.EnumDescriptorProto_ReservedName:
ed.L2.ReservedNames.List = append(ed.L2.ReservedNames.List, pref.Name(sb.MakeString(v)))
case fieldnum.EnumDescriptorProto_ReservedRange:
ed.L2.ReservedRanges.List = append(ed.L2.ReservedRanges.List, unmarshalEnumReservedRange(v))
case fieldnum.EnumDescriptorProto_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
if !ed.L1.eagerValues && len(rawValues) > 0 {
ed.L2.Values.List = make([]EnumValue, len(rawValues))
for i, b := range rawValues {
ed.L2.Values.List[i].unmarshalFull(b, sb, ed.L0.ParentFile, ed, i)
}
}
ed.L2.Options = ed.L0.ParentFile.builder.optionsUnmarshaler(&descopts.Enum, rawOptions)
}
func unmarshalEnumReservedRange(b []byte) (r [2]pref.EnumNumber) {
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.EnumDescriptorProto_EnumReservedRange_Start:
r[0] = pref.EnumNumber(v)
case fieldnum.EnumDescriptorProto_EnumReservedRange_End:
r[1] = pref.EnumNumber(v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
return r
}
func (vd *EnumValue) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
vd.L0.ParentFile = pf
vd.L0.Parent = pd
vd.L0.Index = i
var rawOptions []byte
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.EnumValueDescriptorProto_Number:
vd.L1.Number = pref.EnumNumber(v)
}
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.EnumValueDescriptorProto_Name:
// NOTE: Enum values are in the same scope as the enum parent.
vd.L0.FullName = appendFullName(sb, pd.Parent().FullName(), v)
case fieldnum.EnumValueDescriptorProto_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
vd.L1.Options = pf.builder.optionsUnmarshaler(&descopts.EnumValue, rawOptions)
}
func (md *Message) unmarshalFull(b []byte, sb *strs.Builder) {
var rawFields, rawOneofs [][]byte
var enumIdx, messageIdx, extensionIdx int
var rawOptions []byte
md.L2 = new(MessageL2)
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.DescriptorProto_Field:
rawFields = append(rawFields, v)
case fieldnum.DescriptorProto_OneofDecl:
rawOneofs = append(rawOneofs, v)
case fieldnum.DescriptorProto_ReservedName:
md.L2.ReservedNames.List = append(md.L2.ReservedNames.List, pref.Name(sb.MakeString(v)))
case fieldnum.DescriptorProto_ReservedRange:
md.L2.ReservedRanges.List = append(md.L2.ReservedRanges.List, unmarshalMessageReservedRange(v))
case fieldnum.DescriptorProto_ExtensionRange:
r, rawOptions := unmarshalMessageExtensionRange(v)
opts := md.L0.ParentFile.builder.optionsUnmarshaler(&descopts.ExtensionRange, rawOptions)
md.L2.ExtensionRanges.List = append(md.L2.ExtensionRanges.List, r)
md.L2.ExtensionRangeOptions = append(md.L2.ExtensionRangeOptions, opts)
case fieldnum.DescriptorProto_EnumType:
md.L1.Enums.List[enumIdx].unmarshalFull(v, sb)
enumIdx++
case fieldnum.DescriptorProto_NestedType:
md.L1.Messages.List[messageIdx].unmarshalFull(v, sb)
messageIdx++
case fieldnum.DescriptorProto_Extension:
md.L1.Extensions.List[extensionIdx].unmarshalFull(v, sb)
extensionIdx++
case fieldnum.DescriptorProto_Options:
md.unmarshalOptions(v)
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
if len(rawFields) > 0 || len(rawOneofs) > 0 {
md.L2.Fields.List = make([]Field, len(rawFields))
md.L2.Oneofs.List = make([]Oneof, len(rawOneofs))
for i, b := range rawFields {
fd := &md.L2.Fields.List[i]
fd.unmarshalFull(b, sb, md.L0.ParentFile, md, i)
if fd.L1.Cardinality == pref.Required {
md.L2.RequiredNumbers.List = append(md.L2.RequiredNumbers.List, fd.L1.Number)
}
}
for i, b := range rawOneofs {
od := &md.L2.Oneofs.List[i]
od.unmarshalFull(b, sb, md.L0.ParentFile, md, i)
}
}
md.L2.Options = md.L0.ParentFile.builder.optionsUnmarshaler(&descopts.Message, rawOptions)
}
func (md *Message) unmarshalOptions(b []byte) {
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.MessageOptions_MapEntry:
md.L1.IsMapEntry = protowire.DecodeBool(v)
case fieldnum.MessageOptions_MessageSetWireFormat:
md.L1.IsMessageSet = protowire.DecodeBool(v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
}
func unmarshalMessageReservedRange(b []byte) (r [2]pref.FieldNumber) {
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.DescriptorProto_ReservedRange_Start:
r[0] = pref.FieldNumber(v)
case fieldnum.DescriptorProto_ReservedRange_End:
r[1] = pref.FieldNumber(v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
return r
}
func unmarshalMessageExtensionRange(b []byte) (r [2]pref.FieldNumber, rawOptions []byte) {
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.DescriptorProto_ExtensionRange_Start:
r[0] = pref.FieldNumber(v)
case fieldnum.DescriptorProto_ExtensionRange_End:
r[1] = pref.FieldNumber(v)
}
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.DescriptorProto_ExtensionRange_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
return r, rawOptions
}
func (fd *Field) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
fd.L0.ParentFile = pf
fd.L0.Parent = pd
fd.L0.Index = i
var rawTypeName []byte
var rawOptions []byte
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.FieldDescriptorProto_Number:
fd.L1.Number = pref.FieldNumber(v)
case fieldnum.FieldDescriptorProto_Label:
fd.L1.Cardinality = pref.Cardinality(v)
case fieldnum.FieldDescriptorProto_Type:
fd.L1.Kind = pref.Kind(v)
case fieldnum.FieldDescriptorProto_OneofIndex:
// In Message.unmarshalFull, we allocate slices for both
// the field and oneof descriptors before unmarshaling either
// of them. This ensures pointers to slice elements are stable.
od := &pd.(*Message).L2.Oneofs.List[v]
od.L1.Fields.List = append(od.L1.Fields.List, fd)
if fd.L1.ContainingOneof != nil {
panic("oneof type already set")
}
fd.L1.ContainingOneof = od
case fieldnum.FieldDescriptorProto_Proto3Optional:
fd.L1.IsProto3Optional = protowire.DecodeBool(v)
}
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.FieldDescriptorProto_Name:
fd.L0.FullName = appendFullName(sb, pd.FullName(), v)
case fieldnum.FieldDescriptorProto_JsonName:
fd.L1.JSONName.Init(sb.MakeString(v))
case fieldnum.FieldDescriptorProto_DefaultValue:
fd.L1.Default.val = pref.ValueOfBytes(v) // temporarily store as bytes; later resolved in resolveMessages
case fieldnum.FieldDescriptorProto_TypeName:
rawTypeName = v
case fieldnum.FieldDescriptorProto_Options:
fd.unmarshalOptions(v)
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
if rawTypeName != nil {
name := makeFullName(sb, rawTypeName)
switch fd.L1.Kind {
case pref.EnumKind:
fd.L1.Enum = PlaceholderEnum(name)
case pref.MessageKind, pref.GroupKind:
fd.L1.Message = PlaceholderMessage(name)
}
}
fd.L1.Options = pf.builder.optionsUnmarshaler(&descopts.Field, rawOptions)
}
func (fd *Field) unmarshalOptions(b []byte) {
const FieldOptions_EnforceUTF8 = 13
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.FieldOptions_Packed:
fd.L1.HasPacked = true
fd.L1.IsPacked = protowire.DecodeBool(v)
case fieldnum.FieldOptions_Weak:
fd.L1.IsWeak = protowire.DecodeBool(v)
case FieldOptions_EnforceUTF8:
fd.L1.HasEnforceUTF8 = true
fd.L1.EnforceUTF8 = protowire.DecodeBool(v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
}
func (od *Oneof) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
od.L0.ParentFile = pf
od.L0.Parent = pd
od.L0.Index = i
var rawOptions []byte
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.OneofDescriptorProto_Name:
od.L0.FullName = appendFullName(sb, pd.FullName(), v)
case fieldnum.OneofDescriptorProto_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
od.L1.Options = pf.builder.optionsUnmarshaler(&descopts.Oneof, rawOptions)
}
func (xd *Extension) unmarshalFull(b []byte, sb *strs.Builder) {
var rawTypeName []byte
var rawOptions []byte
xd.L2 = new(ExtensionL2)
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.FieldDescriptorProto_Proto3Optional:
xd.L2.IsProto3Optional = protowire.DecodeBool(v)
}
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.FieldDescriptorProto_JsonName:
xd.L2.JSONName.Init(sb.MakeString(v))
case fieldnum.FieldDescriptorProto_DefaultValue:
xd.L2.Default.val = pref.ValueOfBytes(v) // temporarily store as bytes; later resolved in resolveExtensions
case fieldnum.FieldDescriptorProto_TypeName:
rawTypeName = v
case fieldnum.FieldDescriptorProto_Options:
xd.unmarshalOptions(v)
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
if rawTypeName != nil {
name := makeFullName(sb, rawTypeName)
switch xd.L1.Kind {
case pref.EnumKind:
xd.L2.Enum = PlaceholderEnum(name)
case pref.MessageKind, pref.GroupKind:
xd.L2.Message = PlaceholderMessage(name)
}
}
xd.L2.Options = xd.L0.ParentFile.builder.optionsUnmarshaler(&descopts.Field, rawOptions)
}
func (xd *Extension) unmarshalOptions(b []byte) {
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.FieldOptions_Packed:
xd.L2.IsPacked = protowire.DecodeBool(v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
}
func (sd *Service) unmarshalFull(b []byte, sb *strs.Builder) {
var rawMethods [][]byte
var rawOptions []byte
sd.L2 = new(ServiceL2)
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.ServiceDescriptorProto_Method:
rawMethods = append(rawMethods, v)
case fieldnum.ServiceDescriptorProto_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
if len(rawMethods) > 0 {
sd.L2.Methods.List = make([]Method, len(rawMethods))
for i, b := range rawMethods {
sd.L2.Methods.List[i].unmarshalFull(b, sb, sd.L0.ParentFile, sd, i)
}
}
sd.L2.Options = sd.L0.ParentFile.builder.optionsUnmarshaler(&descopts.Service, rawOptions)
}
func (md *Method) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
md.L0.ParentFile = pf
md.L0.Parent = pd
md.L0.Index = i
var rawOptions []byte
for len(b) > 0 {
num, typ, n := protowire.ConsumeTag(b)
b = b[n:]
switch typ {
case protowire.VarintType:
v, m := protowire.ConsumeVarint(b)
b = b[m:]
switch num {
case fieldnum.MethodDescriptorProto_ClientStreaming:
md.L1.IsStreamingClient = protowire.DecodeBool(v)
case fieldnum.MethodDescriptorProto_ServerStreaming:
md.L1.IsStreamingServer = protowire.DecodeBool(v)
}
case protowire.BytesType:
v, m := protowire.ConsumeBytes(b)
b = b[m:]
switch num {
case fieldnum.MethodDescriptorProto_Name:
md.L0.FullName = appendFullName(sb, pd.FullName(), v)
case fieldnum.MethodDescriptorProto_InputType:
md.L1.Input = PlaceholderMessage(makeFullName(sb, v))
case fieldnum.MethodDescriptorProto_OutputType:
md.L1.Output = PlaceholderMessage(makeFullName(sb, v))
case fieldnum.MethodDescriptorProto_Options:
rawOptions = appendOptions(rawOptions, v)
}
default:
m := protowire.ConsumeFieldValue(num, typ, b)
b = b[m:]
}
}
md.L1.Options = pf.builder.optionsUnmarshaler(&descopts.Method, rawOptions)
}
// appendOptions appends src to dst, where the returned slice is never nil.
// This is necessary to distinguish between empty and unpopulated options.
func appendOptions(dst, src []byte) []byte {
if dst == nil {
dst = []byte{}
}
return append(dst, src...)
}
// optionsUnmarshaler constructs a lazy unmarshal function for an options message.
//
// The type of message to unmarshal to is passed as a pointer since the
// vars in descopts may not yet be populated at the time this function is called.
func (db *Builder) optionsUnmarshaler(p *pref.ProtoMessage, b []byte) func() pref.ProtoMessage {
if b == nil {
return nil
}
var opts pref.ProtoMessage
var once sync.Once
return func() pref.ProtoMessage {
once.Do(func() {
if *p == nil {
panic("Descriptor.Options called without importing the descriptor package")
}
opts = reflect.New(reflect.TypeOf(*p).Elem()).Interface().(pref.ProtoMessage)
if err := (proto.UnmarshalOptions{
AllowPartial: true,
Resolver: db.TypeResolver,
}).Unmarshal(b, opts); err != nil {
panic(err)
}
})
return opts
}
}