Unexport proto.MessageSet, and remove a bunch of its support.

This is a proto1 holdover, which we haven't supported for years.
No-one should be using MessageSet from here.

We still need to support the message set wire format,
so the type is being kept for that. There's probably some more
tidying up that can be done here later.

proto/clone.go

@@ -30,7 +30,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Protocol buffer deep copy and merge.
-// TODO: MessageSet and RawMessage.
+// TODO: RawMessage.
 
 package proto
 

proto/equal.go

@@ -30,7 +30,6 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Protocol buffer comparison.
-// TODO: MessageSet.
 
 package proto
 

proto/message_set.go

@@ -44,11 +44,11 @@ import (
 	"sort"
 )
 
-// ErrNoMessageTypeId occurs when a protocol buffer does not have a message type ID.
+// errNoMessageTypeID occurs when a protocol buffer does not have a message type ID.
 // A message type ID is required for storing a protocol buffer in a message set.
-var ErrNoMessageTypeId = errors.New("proto does not have a message type ID")
+var errNoMessageTypeID = errors.New("proto does not have a message type ID")
 
-// The first two types (_MessageSet_Item and MessageSet)
+// The first two types (_MessageSet_Item and messageSet)
 // model what the protocol compiler produces for the following protocol message:
 //   message MessageSet {
 //     repeated group Item = 1 {
@@ -58,27 +58,20 @@ var ErrNoMessageTypeId = errors.New("proto does not have a message type ID")
 //   }
 // That is the MessageSet wire format. We can't use a proto to generate these
 // because that would introduce a circular dependency between it and this package.
-//
-// When a proto1 proto has a field that looks like:
-//   optional message<MessageSet> info = 3;
-// the protocol compiler produces a field in the generated struct that looks like:
-//   Info *_proto_.MessageSet  `protobuf:"bytes,3,opt,name=info"`
-// The package is automatically inserted so there is no need for that proto file to
-// import this package.
 
 type _MessageSet_Item struct {
 	TypeId  *int32 `protobuf:"varint,2,req,name=type_id"`
 	Message []byte `protobuf:"bytes,3,req,name=message"`
 }
 
-type MessageSet struct {
+type messageSet struct {
 	Item             []*_MessageSet_Item `protobuf:"group,1,rep"`
 	XXX_unrecognized []byte
 	// TODO: caching?
 }
 
-// Make sure MessageSet is a Message.
-var _ Message = (*MessageSet)(nil)
+// Make sure messageSet is a Message.
+var _ Message = (*messageSet)(nil)
 
 // messageTypeIder is an interface satisfied by a protocol buffer type
 // that may be stored in a MessageSet.
@@ -86,7 +79,7 @@ type messageTypeIder interface {
 	MessageTypeId() int32
 }
 
-func (ms *MessageSet) find(pb Message) *_MessageSet_Item {
+func (ms *messageSet) find(pb Message) *_MessageSet_Item {
 	mti, ok := pb.(messageTypeIder)
 	if !ok {
 		return nil
@@ -100,24 +93,24 @@ func (ms *MessageSet) find(pb Message) *_MessageSet_Item {
 	return nil
 }
 
-func (ms *MessageSet) Has(pb Message) bool {
+func (ms *messageSet) Has(pb Message) bool {
 	if ms.find(pb) != nil {
 		return true
 	}
 	return false
 }
 
-func (ms *MessageSet) Unmarshal(pb Message) error {
+func (ms *messageSet) Unmarshal(pb Message) error {
 	if item := ms.find(pb); item != nil {
 		return Unmarshal(item.Message, pb)
 	}
 	if _, ok := pb.(messageTypeIder); !ok {
-		return ErrNoMessageTypeId
+		return errNoMessageTypeID
 	}
 	return nil // TODO: return error instead?
 }
 
-func (ms *MessageSet) Marshal(pb Message) error {
+func (ms *messageSet) Marshal(pb Message) error {
 	msg, err := Marshal(pb)
 	if err != nil {
 		return err
@@ -130,7 +123,7 @@ func (ms *MessageSet) Marshal(pb Message) error {
 
 	mti, ok := pb.(messageTypeIder)
 	if !ok {
-		return ErrNoMessageTypeId
+		return errNoMessageTypeID
 	}
 
 	mtid := mti.MessageTypeId()
@@ -141,9 +134,9 @@ func (ms *MessageSet) Marshal(pb Message) error {
 	return nil
 }
 
-func (ms *MessageSet) Reset()         { *ms = MessageSet{} }
-func (ms *MessageSet) String() string { return CompactTextString(ms) }
-func (*MessageSet) ProtoMessage()     {}
+func (ms *messageSet) Reset()         { *ms = messageSet{} }
+func (ms *messageSet) String() string { return CompactTextString(ms) }
+func (*messageSet) ProtoMessage()     {}
 
 // Support for the message_set_wire_format message option.
 
@@ -169,7 +162,7 @@ func MarshalMessageSet(m map[int32]Extension) ([]byte, error) {
 	}
 	sort.Ints(ids)
 
-	ms := &MessageSet{Item: make([]*_MessageSet_Item, 0, len(m))}
+	ms := &messageSet{Item: make([]*_MessageSet_Item, 0, len(m))}
 	for _, id := range ids {
 		e := m[int32(id)]
 		// Remove the wire type and field number varint, as well as the length varint.
@@ -186,7 +179,7 @@ func MarshalMessageSet(m map[int32]Extension) ([]byte, error) {
 // UnmarshalMessageSet decodes the extension map encoded in buf in the message set wire format.
 // It is called by generated Unmarshal methods on protocol buffer messages with the message_set_wire_format option.
 func UnmarshalMessageSet(buf []byte, m map[int32]Extension) error {
-	ms := new(MessageSet)
+	ms := new(messageSet)
 	if err := Unmarshal(buf, ms); err != nil {
 		return err
 	}

proto/message_set_test.go

@@ -38,7 +38,7 @@ import (
 
 func TestUnmarshalMessageSetWithDuplicate(t *testing.T) {
 	// Check that a repeated message set entry will be concatenated.
-	in := &MessageSet{
+	in := &messageSet{
 		Item: []*_MessageSet_Item{
 			{TypeId: Int32(12345), Message: []byte("hoo")},
 			{TypeId: Int32(12345), Message: []byte("hah")},

proto/text.go

@@ -170,20 +170,12 @@ func writeName(w *textWriter, props *Properties) error {
 	return nil
 }
 
-var (
-	messageSetType = reflect.TypeOf((*MessageSet)(nil)).Elem()
-)
-
 // raw is the interface satisfied by RawMessage.
 type raw interface {
 	Bytes() []byte
 }
 
 func writeStruct(w *textWriter, sv reflect.Value) error {
-	if sv.Type() == messageSetType {
-		return writeMessageSet(w, sv.Addr().Interface().(*MessageSet))
-	}
-
 	st := sv.Type()
 	sprops := GetProperties(st)
 	for i := 0; i < sv.NumField(); i++ {
@@ -525,44 +517,6 @@ func writeString(w *textWriter, s string) error {
 	return w.WriteByte('"')
 }
 
-func writeMessageSet(w *textWriter, ms *MessageSet) error {
-	for _, item := range ms.Item {
-		id := *item.TypeId
-		if msd, ok := messageSetMap[id]; ok {
-			// Known message set type.
-			if _, err := fmt.Fprintf(w, "[%s]: <\n", msd.name); err != nil {
-				return err
-			}
-			w.indent()
-
-			pb := reflect.New(msd.t.Elem())
-			if err := Unmarshal(item.Message, pb.Interface().(Message)); err != nil {
-				if _, err := fmt.Fprintf(w, "/* bad message: %v */\n", err); err != nil {
-					return err
-				}
-			} else {
-				if err := writeStruct(w, pb.Elem()); err != nil {
-					return err
-				}
-			}
-		} else {
-			// Unknown type.
-			if _, err := fmt.Fprintf(w, "[%d]: <\n", id); err != nil {
-				return err
-			}
-			w.indent()
-			if err := writeUnknownStruct(w, item.Message); err != nil {
-				return err
-			}
-		}
-		w.unindent()
-		if _, err := w.Write(gtNewline); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
 func writeUnknownStruct(w *textWriter, data []byte) (err error) {
 	if !w.compact {
 		if _, err := fmt.Fprintf(w, "/* %d unknown bytes */\n", len(data)); err != nil {