legacy_extension.go raw
1 // Copyright 2018 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 package impl
6
7 import (
8 "reflect"
9
10 "google.golang.org/protobuf/internal/descopts"
11 "google.golang.org/protobuf/internal/encoding/messageset"
12 ptag "google.golang.org/protobuf/internal/encoding/tag"
13 "google.golang.org/protobuf/internal/filedesc"
14 "google.golang.org/protobuf/internal/pragma"
15 "google.golang.org/protobuf/reflect/protoreflect"
16 "google.golang.org/protobuf/reflect/protoregistry"
17 "google.golang.org/protobuf/runtime/protoiface"
18 )
19
20 func (xi *ExtensionInfo) initToLegacy() {
21 xd := xi.desc
22 var parent protoiface.MessageV1
23 messageName := xd.ContainingMessage().FullName()
24 if mt, _ := protoregistry.GlobalTypes.FindMessageByName(messageName); mt != nil {
25 // Create a new parent message and unwrap it if possible.
26 mv := mt.New().Interface()
27 t := reflect.TypeOf(mv)
28 if mv, ok := mv.(unwrapper); ok {
29 t = reflect.TypeOf(mv.protoUnwrap())
30 }
31
32 // Check whether the message implements the legacy v1 Message interface.
33 mz := reflect.Zero(t).Interface()
34 if mz, ok := mz.(protoiface.MessageV1); ok {
35 parent = mz
36 }
37 }
38
39 // Determine the v1 extension type, which is unfortunately not the same as
40 // the v2 ExtensionType.GoType.
41 extType := xi.goType
42 switch extType.Kind() {
43 case reflect.Bool, reflect.Int32, reflect.Int64, reflect.Uint32, reflect.Uint64, reflect.Float32, reflect.Float64, reflect.String:
44 extType = reflect.PtrTo(extType) // T -> *T for singular scalar fields
45 }
46
47 // Reconstruct the legacy enum full name.
48 var enumName string
49 if xd.Kind() == protoreflect.EnumKind {
50 enumName = legacyEnumName(xd.Enum())
51 }
52
53 // Derive the proto file that the extension was declared within.
54 var filename string
55 if fd := xd.ParentFile(); fd != nil {
56 filename = fd.Path()
57 }
58
59 // For MessageSet extensions, the name used is the parent message.
60 name := xd.FullName()
61 if messageset.IsMessageSetExtension(xd) {
62 name = name.Parent()
63 }
64
65 xi.ExtendedType = parent
66 xi.ExtensionType = reflect.Zero(extType).Interface()
67 xi.Field = int32(xd.Number())
68 xi.Name = string(name)
69 xi.Tag = ptag.Marshal(xd, enumName)
70 xi.Filename = filename
71 }
72
73 // initFromLegacy initializes an ExtensionInfo from
74 // the contents of the deprecated exported fields of the type.
75 func (xi *ExtensionInfo) initFromLegacy() {
76 // The v1 API returns "type incomplete" descriptors where only the
77 // field number is specified. In such a case, use a placeholder.
78 if xi.ExtendedType == nil || xi.ExtensionType == nil {
79 xd := placeholderExtension{
80 name: protoreflect.FullName(xi.Name),
81 number: protoreflect.FieldNumber(xi.Field),
82 }
83 xi.desc = extensionTypeDescriptor{xd, xi}
84 return
85 }
86
87 // Resolve enum or message dependencies.
88 var ed protoreflect.EnumDescriptor
89 var md protoreflect.MessageDescriptor
90 t := reflect.TypeOf(xi.ExtensionType)
91 isOptional := t.Kind() == reflect.Ptr && t.Elem().Kind() != reflect.Struct
92 isRepeated := t.Kind() == reflect.Slice && t.Elem().Kind() != reflect.Uint8
93 if isOptional || isRepeated {
94 t = t.Elem()
95 }
96 switch v := reflect.Zero(t).Interface().(type) {
97 case protoreflect.Enum:
98 ed = v.Descriptor()
99 case enumV1:
100 ed = LegacyLoadEnumDesc(t)
101 case protoreflect.ProtoMessage:
102 md = v.ProtoReflect().Descriptor()
103 case messageV1:
104 md = LegacyLoadMessageDesc(t)
105 }
106
107 // Derive basic field information from the struct tag.
108 var evs protoreflect.EnumValueDescriptors
109 if ed != nil {
110 evs = ed.Values()
111 }
112 fd := ptag.Unmarshal(xi.Tag, t, evs).(*filedesc.Field)
113
114 // Construct a v2 ExtensionType.
115 xd := &filedesc.Extension{L2: new(filedesc.ExtensionL2)}
116 xd.L0.ParentFile = filedesc.SurrogateProto2
117 xd.L0.FullName = protoreflect.FullName(xi.Name)
118 xd.L1.Number = protoreflect.FieldNumber(xi.Field)
119 xd.L1.Cardinality = fd.L1.Cardinality
120 xd.L1.Kind = fd.L1.Kind
121 xd.L1.EditionFeatures = fd.L1.EditionFeatures
122 xd.L2.Default = fd.L1.Default
123 xd.L1.Extendee = Export{}.MessageDescriptorOf(xi.ExtendedType)
124 xd.L2.Enum = ed
125 xd.L2.Message = md
126
127 // Derive real extension field name for MessageSets.
128 if messageset.IsMessageSet(xd.L1.Extendee) && md.FullName() == xd.L0.FullName {
129 xd.L0.FullName = xd.L0.FullName.Append(messageset.ExtensionName)
130 }
131
132 tt := reflect.TypeOf(xi.ExtensionType)
133 if isOptional {
134 tt = tt.Elem()
135 }
136 xi.goType = tt
137 xi.desc = extensionTypeDescriptor{xd, xi}
138 }
139
140 type placeholderExtension struct {
141 name protoreflect.FullName
142 number protoreflect.FieldNumber
143 }
144
145 func (x placeholderExtension) ParentFile() protoreflect.FileDescriptor { return nil }
146 func (x placeholderExtension) Parent() protoreflect.Descriptor { return nil }
147 func (x placeholderExtension) Index() int { return 0 }
148 func (x placeholderExtension) Syntax() protoreflect.Syntax { return 0 }
149 func (x placeholderExtension) Name() protoreflect.Name { return x.name.Name() }
150 func (x placeholderExtension) FullName() protoreflect.FullName { return x.name }
151 func (x placeholderExtension) IsPlaceholder() bool { return true }
152 func (x placeholderExtension) Options() protoreflect.ProtoMessage { return descopts.Field }
153 func (x placeholderExtension) Number() protoreflect.FieldNumber { return x.number }
154 func (x placeholderExtension) Cardinality() protoreflect.Cardinality { return 0 }
155 func (x placeholderExtension) Kind() protoreflect.Kind { return 0 }
156 func (x placeholderExtension) HasJSONName() bool { return false }
157 func (x placeholderExtension) JSONName() string { return "[" + string(x.name) + "]" }
158 func (x placeholderExtension) TextName() string { return "[" + string(x.name) + "]" }
159 func (x placeholderExtension) HasPresence() bool { return false }
160 func (x placeholderExtension) HasOptionalKeyword() bool { return false }
161 func (x placeholderExtension) IsExtension() bool { return true }
162 func (x placeholderExtension) IsWeak() bool { return false }
163 func (x placeholderExtension) IsLazy() bool { return false }
164 func (x placeholderExtension) IsPacked() bool { return false }
165 func (x placeholderExtension) IsList() bool { return false }
166 func (x placeholderExtension) IsMap() bool { return false }
167 func (x placeholderExtension) MapKey() protoreflect.FieldDescriptor { return nil }
168 func (x placeholderExtension) MapValue() protoreflect.FieldDescriptor { return nil }
169 func (x placeholderExtension) HasDefault() bool { return false }
170 func (x placeholderExtension) Default() protoreflect.Value { return protoreflect.Value{} }
171 func (x placeholderExtension) DefaultEnumValue() protoreflect.EnumValueDescriptor { return nil }
172 func (x placeholderExtension) ContainingOneof() protoreflect.OneofDescriptor { return nil }
173 func (x placeholderExtension) ContainingMessage() protoreflect.MessageDescriptor { return nil }
174 func (x placeholderExtension) Enum() protoreflect.EnumDescriptor { return nil }
175 func (x placeholderExtension) Message() protoreflect.MessageDescriptor { return nil }
176 func (x placeholderExtension) ProtoType(protoreflect.FieldDescriptor) { return }
177 func (x placeholderExtension) ProtoInternal(pragma.DoNotImplement) { return }
178