blob: d761ab331d1ce86d299e22a6e6a288b73b231979 [file] [log] [blame]
David K. Bainbridgee05cf0c2021-08-19 03:16:50 +00001// Copyright 2019 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
5package proto
6
7import (
8 "fmt"
9
10 "google.golang.org/protobuf/reflect/protoreflect"
11 "google.golang.org/protobuf/runtime/protoiface"
12)
13
14// Merge merges src into dst, which must be a message with the same descriptor.
15//
16// Populated scalar fields in src are copied to dst, while populated
17// singular messages in src are merged into dst by recursively calling Merge.
18// The elements of every list field in src is appended to the corresponded
19// list fields in dst. The entries of every map field in src is copied into
20// the corresponding map field in dst, possibly replacing existing entries.
21// The unknown fields of src are appended to the unknown fields of dst.
22//
23// It is semantically equivalent to unmarshaling the encoded form of src
24// into dst with the UnmarshalOptions.Merge option specified.
25func Merge(dst, src Message) {
26 // TODO: Should nil src be treated as semantically equivalent to a
27 // untyped, read-only, empty message? What about a nil dst?
28
29 dstMsg, srcMsg := dst.ProtoReflect(), src.ProtoReflect()
30 if dstMsg.Descriptor() != srcMsg.Descriptor() {
31 if got, want := dstMsg.Descriptor().FullName(), srcMsg.Descriptor().FullName(); got != want {
32 panic(fmt.Sprintf("descriptor mismatch: %v != %v", got, want))
33 }
34 panic("descriptor mismatch")
35 }
36 mergeOptions{}.mergeMessage(dstMsg, srcMsg)
37}
38
39// Clone returns a deep copy of m.
40// If the top-level message is invalid, it returns an invalid message as well.
41func Clone(m Message) Message {
42 // NOTE: Most usages of Clone assume the following properties:
43 // t := reflect.TypeOf(m)
44 // t == reflect.TypeOf(m.ProtoReflect().New().Interface())
45 // t == reflect.TypeOf(m.ProtoReflect().Type().Zero().Interface())
46 //
47 // Embedding protobuf messages breaks this since the parent type will have
48 // a forwarded ProtoReflect method, but the Interface method will return
49 // the underlying embedded message type.
50 if m == nil {
51 return nil
52 }
53 src := m.ProtoReflect()
54 if !src.IsValid() {
55 return src.Type().Zero().Interface()
56 }
57 dst := src.New()
58 mergeOptions{}.mergeMessage(dst, src)
59 return dst.Interface()
60}
61
62// mergeOptions provides a namespace for merge functions, and can be
63// exported in the future if we add user-visible merge options.
64type mergeOptions struct{}
65
66func (o mergeOptions) mergeMessage(dst, src protoreflect.Message) {
67 methods := protoMethods(dst)
68 if methods != nil && methods.Merge != nil {
69 in := protoiface.MergeInput{
70 Destination: dst,
71 Source: src,
72 }
73 out := methods.Merge(in)
74 if out.Flags&protoiface.MergeComplete != 0 {
75 return
76 }
77 }
78
79 if !dst.IsValid() {
80 panic(fmt.Sprintf("cannot merge into invalid %v message", dst.Descriptor().FullName()))
81 }
82
83 src.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
84 switch {
85 case fd.IsList():
86 o.mergeList(dst.Mutable(fd).List(), v.List(), fd)
87 case fd.IsMap():
88 o.mergeMap(dst.Mutable(fd).Map(), v.Map(), fd.MapValue())
89 case fd.Message() != nil:
90 o.mergeMessage(dst.Mutable(fd).Message(), v.Message())
91 case fd.Kind() == protoreflect.BytesKind:
92 dst.Set(fd, o.cloneBytes(v))
93 default:
94 dst.Set(fd, v)
95 }
96 return true
97 })
98
99 if len(src.GetUnknown()) > 0 {
100 dst.SetUnknown(append(dst.GetUnknown(), src.GetUnknown()...))
101 }
102}
103
104func (o mergeOptions) mergeList(dst, src protoreflect.List, fd protoreflect.FieldDescriptor) {
105 // Merge semantics appends to the end of the existing list.
106 for i, n := 0, src.Len(); i < n; i++ {
107 switch v := src.Get(i); {
108 case fd.Message() != nil:
109 dstv := dst.NewElement()
110 o.mergeMessage(dstv.Message(), v.Message())
111 dst.Append(dstv)
112 case fd.Kind() == protoreflect.BytesKind:
113 dst.Append(o.cloneBytes(v))
114 default:
115 dst.Append(v)
116 }
117 }
118}
119
120func (o mergeOptions) mergeMap(dst, src protoreflect.Map, fd protoreflect.FieldDescriptor) {
121 // Merge semantics replaces, rather than merges into existing entries.
122 src.Range(func(k protoreflect.MapKey, v protoreflect.Value) bool {
123 switch {
124 case fd.Message() != nil:
125 dstv := dst.NewValue()
126 o.mergeMessage(dstv.Message(), v.Message())
127 dst.Set(k, dstv)
128 case fd.Kind() == protoreflect.BytesKind:
129 dst.Set(k, o.cloneBytes(v))
130 default:
131 dst.Set(k, v)
132 }
133 return true
134 })
135}
136
137func (o mergeOptions) cloneBytes(v protoreflect.Value) protoreflect.Value {
138 return protoreflect.ValueOfBytes(append([]byte{}, v.Bytes()...))
139}