proto: ignore unknown fields in map entries (#561)

A proto map entry is conceptually a message with two fields.
In the same way that unknown fields don't cause a parsing error,
map parsing should ignore unknown fields and tags.
Similarly, it treats a missing field as the zero value.

Fixes #403

proto/map_test.go

@@ -2,12 +2,36 @@ package proto_test
 
 import (
 	"fmt"
+	"reflect"
 	"testing"
 
 	"github.com/golang/protobuf/proto"
 	ppb "github.com/golang/protobuf/proto/proto3_proto"
 )
 
+func TestMap(t *testing.T) {
+	var b []byte
+	fmt.Sscanf("a2010c0a044b657931120456616c31a201130a044b657932120556616c3261120456616c32a201240a044b6579330d05000000120556616c33621a0556616c3361120456616c331505000000a20100a201260a044b657934130a07536f6d6555524c1209536f6d655469746c651a08536e69707065743114", "%x", &b)
+
+	var m ppb.Message
+	if err := proto.Unmarshal(b, &m); err != nil {
+		t.Fatalf("proto.Unmarshal error: %v", err)
+	}
+
+	got := m.StringMap
+	want := map[string]string{
+		"":     "",
+		"Key1": "Val1",
+		"Key2": "Val2",
+		"Key3": "Val3",
+		"Key4": "",
+	}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("maps differ:\ngot  %#v\nwant %#v", got, want)
+	}
+}
+
 func marshalled() []byte {
 	m := &ppb.IntMaps{}
 	for i := 0; i < 1000; i++ {

proto/proto3_proto/proto3.pb.go

@@ -46,7 +46,7 @@ func (x Message_Humour) String() string {
 	return proto.EnumName(Message_Humour_name, int32(x))
 }
 func (Message_Humour) EnumDescriptor() ([]byte, []int) {
-	return fileDescriptor_proto3_ef797ec3431c4aaa, []int{0, 0}
+	return fileDescriptor_proto3_e706e4ff19a5dbea, []int{0, 0}
 }
 
 type Message struct {
@@ -68,6 +68,7 @@ type Message struct {
 	ManyThings           []*any.Any                         `protobuf:"bytes,15,rep,name=many_things,json=manyThings" json:"many_things,omitempty"`
 	Submessage           *Message                           `protobuf:"bytes,17,opt,name=submessage" json:"submessage,omitempty"`
 	Children             []*Message                         `protobuf:"bytes,18,rep,name=children" json:"children,omitempty"`
+	StringMap            map[string]string                  `protobuf:"bytes,20,rep,name=string_map,json=stringMap" json:"string_map,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
 	XXX_NoUnkeyedLiteral struct{}                           `json:"-"`
 	XXX_unrecognized     []byte                             `json:"-"`
 	XXX_sizecache        int32                              `json:"-"`
@@ -77,7 +78,7 @@ func (m *Message) Reset()         { *m = Message{} }
 func (m *Message) String() string { return proto.CompactTextString(m) }
 func (*Message) ProtoMessage()    {}
 func (*Message) Descriptor() ([]byte, []int) {
-	return fileDescriptor_proto3_ef797ec3431c4aaa, []int{0}
+	return fileDescriptor_proto3_e706e4ff19a5dbea, []int{0}
 }
 func (m *Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message.Unmarshal(m, b)
@@ -223,6 +224,13 @@ func (m *Message) GetChildren() []*Message {
 	return nil
 }
 
+func (m *Message) GetStringMap() map[string]string {
+	if m != nil {
+		return m.StringMap
+	}
+	return nil
+}
+
 type Nested struct {
 	Bunny                string   `protobuf:"bytes,1,opt,name=bunny" json:"bunny,omitempty"`
 	Cute                 bool     `protobuf:"varint,2,opt,name=cute" json:"cute,omitempty"`
@@ -235,7 +243,7 @@ func (m *Nested) Reset()         { *m = Nested{} }
 func (m *Nested) String() string { return proto.CompactTextString(m) }
 func (*Nested) ProtoMessage()    {}
 func (*Nested) Descriptor() ([]byte, []int) {
-	return fileDescriptor_proto3_ef797ec3431c4aaa, []int{1}
+	return fileDescriptor_proto3_e706e4ff19a5dbea, []int{1}
 }
 func (m *Nested) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Nested.Unmarshal(m, b)
@@ -280,7 +288,7 @@ func (m *MessageWithMap) Reset()         { *m = MessageWithMap{} }
 func (m *MessageWithMap) String() string { return proto.CompactTextString(m) }
 func (*MessageWithMap) ProtoMessage()    {}
 func (*MessageWithMap) Descriptor() ([]byte, []int) {
-	return fileDescriptor_proto3_ef797ec3431c4aaa, []int{2}
+	return fileDescriptor_proto3_e706e4ff19a5dbea, []int{2}
 }
 func (m *MessageWithMap) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_MessageWithMap.Unmarshal(m, b)
@@ -318,7 +326,7 @@ func (m *IntMap) Reset()         { *m = IntMap{} }
 func (m *IntMap) String() string { return proto.CompactTextString(m) }
 func (*IntMap) ProtoMessage()    {}
 func (*IntMap) Descriptor() ([]byte, []int) {
-	return fileDescriptor_proto3_ef797ec3431c4aaa, []int{3}
+	return fileDescriptor_proto3_e706e4ff19a5dbea, []int{3}
 }
 func (m *IntMap) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_IntMap.Unmarshal(m, b)
@@ -356,7 +364,7 @@ func (m *IntMaps) Reset()         { *m = IntMaps{} }
 func (m *IntMaps) String() string { return proto.CompactTextString(m) }
 func (*IntMaps) ProtoMessage()    {}
 func (*IntMaps) Descriptor() ([]byte, []int) {
-	return fileDescriptor_proto3_ef797ec3431c4aaa, []int{4}
+	return fileDescriptor_proto3_e706e4ff19a5dbea, []int{4}
 }
 func (m *IntMaps) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_IntMaps.Unmarshal(m, b)
@@ -386,6 +394,7 @@ func (m *IntMaps) GetMaps() []*IntMap {
 func init() {
 	proto.RegisterType((*Message)(nil), "proto3_proto.Message")
 	proto.RegisterMapType((map[string]*test_proto.SubDefaults)(nil), "proto3_proto.Message.Proto2ValueEntry")
+	proto.RegisterMapType((map[string]string)(nil), "proto3_proto.Message.StringMapEntry")
 	proto.RegisterMapType((map[string]*Nested)(nil), "proto3_proto.Message.TerrainEntry")
 	proto.RegisterType((*Nested)(nil), "proto3_proto.Nested")
 	proto.RegisterType((*MessageWithMap)(nil), "proto3_proto.MessageWithMap")
@@ -396,54 +405,57 @@ func init() {
 	proto.RegisterEnum("proto3_proto.Message_Humour", Message_Humour_name, Message_Humour_value)
 }
 
-func init() { proto.RegisterFile("proto3_proto/proto3.proto", fileDescriptor_proto3_ef797ec3431c4aaa) }
-
-var fileDescriptor_proto3_ef797ec3431c4aaa = []byte{
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+func init() { proto.RegisterFile("proto3_proto/proto3.proto", fileDescriptor_proto3_e706e4ff19a5dbea) }
+
+var fileDescriptor_proto3_e706e4ff19a5dbea = []byte{
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+	0x9d, 0xe9, 0x8b, 0xfd, 0x7d, 0x38, 0x03, 0xaf, 0x3e, 0xb7, 0xfd, 0x02, 0x9a, 0x2f, 0x4c, 0x2f,
+	0xe0, 0xb7, 0xd0, 0x31, 0xdd, 0x6f, 0xfd, 0xcf, 0x8a, 0x19, 0xe4, 0x45, 0xeb, 0xb9, 0x35, 0xbc,
+	0x07, 0xff, 0xdd, 0x51, 0x34, 0x64, 0x7d, 0x7a, 0x9c, 0xf5, 0xbd, 0xfb, 0x50, 0x4b, 0xfc, 0x12,
+	0x4e, 0x8f, 0xdf, 0xa3, 0x21, 0xed, 0xa0, 0x9e, 0xb6, 0x5f, 0x8b, 0x1e, 0xfd, 0x0c, 0x5d, 0xb3,
+	0xd7, 0xc8, 0x85, 0xde, 0x9b, 0xe9, 0xf5, 0xf4, 0xb7, 0xfb, 0xa9, 0xff, 0x11, 0x72, 0xa0, 0x3d,
+	0x7b, 0x33, 0x9d, 0xfb, 0x16, 0x3a, 0x81, 0xfe, 0xfc, 0xe6, 0x62, 0x36, 0xbf, 0x9b, 0x5c, 0x5d,
+	0xfb, 0x2d, 0xf4, 0x08, 0xdc, 0xcb, 0xc9, 0xcd, 0x4d, 0x7c, 0x79, 0x31, 0xb9, 0x79, 0xf5, 0x87,
+	0x6f, 0x8f, 0xc6, 0xd0, 0x35, 0x2f, 0xab, 0x4c, 0x16, 0xfa, 0x2b, 0x32, 0xc6, 0xe6, 0xa2, 0xfe,
+	0x2c, 0x96, 0x85, 0x34, 0xce, 0x0e, 0xd1, 0xe7, 0xd1, 0xbf, 0x16, 0x9c, 0x56, 0x33, 0xb8, 0x4f,
+	0xe4, 0xe6, 0x96, 0xee, 0xd0, 0x0c, 0xbc, 0x45, 0x29, 0x99, 0x9a, 0xd9, 0x4e, 0x2d, 0xa3, 0xa5,
+	0xe7, 0xf6, 0xb4, 0x71, 0x6e, 0x55, 0x4c, 0x74, 0x59, 0x4a, 0x76, 0x6b, 0xf8, 0x6a, 0xb5, 0x17,
+	0x6f, 0x95, 0xe1, 0x4f, 0xe0, 0xbf, 0x0b, 0xd4, 0x3b, 0xe3, 0x34, 0x74, 0xc6, 0xab, 0x77, 0xe6,
+	0x2f, 0xe8, 0x4e, 0xb8, 0x54, 0xb5, 0x9d, 0x81, 0x9d, 0x4b, 0x59, 0x95, 0xf4, 0xc5, 0x71, 0x49,
+	0x06, 0x89, 0x88, 0x94, 0xa6, 0x04, 0x45, 0x0e, 0x7f, 0x04, 0x67, 0x2f, 0xd4, 0x2d, 0x3b, 0x0d,
+	0x96, 0x9d, 0xba, 0xe5, 0x33, 0xe8, 0x99, 0x7c, 0x02, 0x85, 0xd0, 0x4e, 0xe9, 0x4e, 0x54, 0xa6,
+	0x83, 0x26, 0x53, 0xa2, 0x89, 0x45, 0xd7, 0x3c, 0xfa, 0x2f, 0x00, 0x00, 0xff, 0xff, 0x99, 0x24,
+	0x6b, 0x12, 0x6d, 0x06, 0x00, 0x00,
 }

proto/proto3_proto/proto3.proto

@@ -66,6 +66,8 @@ message Message {
 
   Message submessage = 17;
   repeated Message children = 18;
+
+  map<string, string> string_map = 20;
 }
 
 message Nested {

proto/table_unmarshal.go

@@ -188,40 +188,10 @@ func (u *unmarshalInfo) unmarshal(m pointer, b []byte) error {
 		// Unknown tag.
 		if !u.unrecognized.IsValid() {
 			// Don't keep unrecognized data; just skip it.
-			// Use wire type to skip data.
-			switch wire {
-			case WireVarint:
-				_, k := decodeVarint(b)
-				if k == 0 {
-					return io.ErrUnexpectedEOF
-				}
-				b = b[k:]
-			case WireFixed32:
-				if len(b) < 4 {
-					return io.ErrUnexpectedEOF
-				}
-				b = b[4:]
-			case WireFixed64:
-				if len(b) < 8 {
-					return io.ErrUnexpectedEOF
-				}
-				b = b[8:]
-			case WireBytes:
-				m, k := decodeVarint(b)
-				if k == 0 || uint64(len(b)-k) < m {
-					return io.ErrUnexpectedEOF
-				}
-				b = b[uint64(k)+m:]
-			case WireStartGroup:
-				// Proto3 doesn't have groups. But the data may have
-				// been encoded with proto2.
-				_, i := findEndGroup(b)
-				if i == -1 {
-					return io.ErrUnexpectedEOF
-				}
-				b = b[i:]
-			default:
-				return fmt.Errorf("proto: can't skip unknown wire type %d for %s", wire, u.typ)
+			var err error
+			b, err = skipField(b, wire)
+			if err != nil {
+				return err
 			}
 			continue
 		}
@@ -253,49 +223,17 @@ func (u *unmarshalInfo) unmarshal(m pointer, b []byte) error {
 				panic("no extensions field available")
 			}
 		}
+
 		// Use wire type to skip data.
-		switch wire {
-		case WireVarint:
-			_, k := decodeVarint(b)
-			if k == 0 {
-				return io.ErrUnexpectedEOF
-			}
-			*z = encodeVarint(*z, tag<<3|uint64(wire))
-			*z = append(*z, b[:k]...)
-			b = b[k:]
-		case WireFixed32:
-			if len(b) < 4 {
-				return io.ErrUnexpectedEOF
-			}
-			*z = encodeVarint(*z, tag<<3|uint64(wire))
-			*z = append(*z, b[:4]...)
-			b = b[4:]
-		case WireFixed64:
-			if len(b) < 8 {
-				return io.ErrUnexpectedEOF
-			}
-			*z = encodeVarint(*z, tag<<3|uint64(wire))
-			*z = append(*z, b[:8]...)
-			b = b[8:]
-		case WireBytes:
-			m, k := decodeVarint(b)
-			if k == 0 || uint64(len(b)) < uint64(k)+m {
-				return io.ErrUnexpectedEOF
-			}
-			*z = encodeVarint(*z, tag<<3|uint64(wire))
-			*z = append(*z, b[:uint64(k)+m]...)
-			b = b[uint64(k)+m:]
-		case WireStartGroup:
-			_, i := findEndGroup(b)
-			if i == -1 {
-				return io.ErrUnexpectedEOF
-			}
-			*z = encodeVarint(*z, tag<<3|uint64(wire))
-			*z = append(*z, b[:i]...)
-			b = b[i:]
-		default:
-			return fmt.Errorf("proto: can't skip unknown wire type %d for %s", wire, u.typ)
+		var err error
+		b0 := b
+		b, err = skipField(b, wire)
+		if err != nil {
+			return err
 		}
+		*z = encodeVarint(*z, tag<<3|uint64(wire))
+		*z = append(*z, b0[:len(b0)-len(b)]...)
+
 		if emap != nil {
 			emap[int32(tag)] = e
 		}
@@ -1742,26 +1680,30 @@ func makeUnmarshalMap(f *reflect.StructField) unmarshaler {
 			if n == 0 {
 				return nil, io.ErrUnexpectedEOF
 			}
+			wire := int(x) & 7
 			b = b[n:]
+
+			var err error
 			switch x >> 3 {
 			case 1:
-				var err error
-				b, err = unmarshalKey(b, valToPointer(k), int(x)&7)
-				if err != nil {
-					return nil, err
-				}
+				b, err = unmarshalKey(b, valToPointer(k), wire)
 			case 2:
-				var err error
-				b, err = unmarshalVal(b, valToPointer(v), int(x)&7)
-				if err != nil {
-					return nil, err
-				}
+				b, err = unmarshalVal(b, valToPointer(v), wire)
 			default:
-				// Unknown tag.  Technically we could skip this
-				// entry and be ok.  But it's much more likely
-				// to be error somewhere - map entries shouldn't
-				// have additional tags.
-				return nil, io.ErrUnexpectedEOF
+				err = errInternalBadWireType // skip unknown tag
+			}
+
+			if err == nil {
+				continue
+			}
+			if err != errInternalBadWireType {
+				return nil, err
+			}
+
+			// Skip past unknown fields.
+			b, err = skipField(b, wire)
+			if err != nil {
+				return nil, err
 			}
 		}
 
@@ -1815,6 +1757,43 @@ func makeUnmarshalOneof(typ, ityp reflect.Type, unmarshal unmarshaler) unmarshal
 // Error used by decode internally.
 var errInternalBadWireType = errors.New("proto: internal error: bad wiretype")
 
+// skipField skips past a field of type wire and returns the remaining bytes.
+func skipField(b []byte, wire int) ([]byte, error) {
+	switch wire {
+	case WireVarint:
+		_, k := decodeVarint(b)
+		if k == 0 {
+			return b, io.ErrUnexpectedEOF
+		}
+		b = b[k:]
+	case WireFixed32:
+		if len(b) < 4 {
+			return b, io.ErrUnexpectedEOF
+		}
+		b = b[4:]
+	case WireFixed64:
+		if len(b) < 8 {
+			return b, io.ErrUnexpectedEOF
+		}
+		b = b[8:]
+	case WireBytes:
+		m, k := decodeVarint(b)
+		if k == 0 || uint64(len(b)-k) < m {
+			return b, io.ErrUnexpectedEOF
+		}
+		b = b[uint64(k)+m:]
+	case WireStartGroup:
+		_, i := findEndGroup(b)
+		if i == -1 {
+			return b, io.ErrUnexpectedEOF
+		}
+		b = b[i:]
+	default:
+		return b, fmt.Errorf("proto: can't skip unknown wire type %d", wire)
+	}
+	return b, nil
+}
+
 // findEndGroup finds the index of the next EndGroup tag.
 // Groups may be nested, so the "next" EndGroup tag is the first
 // unpaired EndGroup.