foo.diff

diff --git a/go/vt/vtctl/topo.go b/go/vt/vtctl/topo.go
index 547a84baa..f03ab709d 100644
--- a/go/vt/vtctl/topo.go
+++ b/go/vt/vtctl/topo.go
@@ -17,8 +17,10 @@ limitations under the License.
 package vtctl
 
 import (
+	"encoding/json"
 	"flag"
 	"fmt"
+	"github.com/golang/protobuf/jsonpb"
 	"io/ioutil"
 	"path"
 
@@ -42,7 +44,7 @@ func init() {
 	addCommand(topoGroupName, command{
 		"TopoCat",
 		commandTopoCat,
-		"[-cell <cell>] [-decode_proto] [-long] <path> [<path>...]",
+		"[-cell <cell>] [-decode_proto] [-long] [-json] <path> [<path>...]",
 		"Retrieves the file(s) at <path> from the topo service, and displays it. It can resolve wildcards, and decode the proto-encoded data."})
 
 	addCommand(topoGroupName, command{
@@ -54,40 +56,70 @@ func init() {
 
 // DecodeContent uses the filename to imply a type, and proto-decodes
 // the right object, then echoes it as a string.
-func DecodeContent(filename string, data []byte) (string, error) {
+func DecodeContent(filename string, data []byte, json bool) (string, error) {
+	message, err := decodeContentAsMessage(filename, data)
+	if message == nil || err != nil {
+		return string(data), err
+	}
+
+	return proto.MarshalTextString(message), nil
+}
+
+func decodeContentAsInterface(filename string, data []byte) (interface{}, error) {
+	message, err := decodeContentAsMessage(filename, data)
+	if message == nil || err != nil {
+		return data, err
+	}
+
+	jsonText, err := new(jsonpb.Marshaler).MarshalToString(message)
+	if err != nil {
+		return data, err
+	}
+
+	var obj interface{}
+	if err := json.Unmarshal([]byte(jsonString), &obj); err != nil {
+		return data, err
+	}
+
+
+}
+
+func decodeContentAsMessage(filename string, data []byte) (proto.Message, error) {
 	name := path.Base(filename)
 
-	var p proto.Message
+	var message proto.Message
 	switch name {
 	case topo.CellInfoFile:
-		p = new(topodatapb.CellInfo)
+		message = new(topodatapb.CellInfo)
 	case topo.KeyspaceFile:
-		p = new(topodatapb.Keyspace)
+		message = new(topodatapb.Keyspace)
 	case topo.ShardFile:
-		p = new(topodatapb.Shard)
+		message = new(topodatapb.Shard)
 	case topo.VSchemaFile:
-		p = new(vschemapb.Keyspace)
+		message = new(vschemapb.Keyspace)
 	case topo.ShardReplicationFile:
-		p = new(topodatapb.ShardReplication)
+		message = new(topodatapb.ShardReplication)
 	case topo.TabletFile:
-		p = new(topodatapb.Tablet)
+		message = new(topodatapb.Tablet)
 	case topo.SrvVSchemaFile:
-		p = new(vschemapb.SrvVSchema)
+		message = new(vschemapb.SrvVSchema)
 	case topo.SrvKeyspaceFile:
-		p = new(topodatapb.SrvKeyspace)
+		message = new(topodatapb.SrvKeyspace)
 	default:
-		return string(data), nil
+		return nil, nil
 	}
 
-	if err := proto.Unmarshal(data, p); err != nil {
-		return string(data), err
+	if err := proto.Unmarshal(data, message); err != nil {
+		return nil, err
 	}
-	return proto.MarshalTextString(p), nil
+
+	return message, nil
 }
 
 func commandTopoCat(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) error {
 	cell := subFlags.String("cell", topo.GlobalCell, "topology cell to cat the file from. Defaults to global cell.")
 	long := subFlags.Bool("long", false, "long listing.")
+	json := subFlags.Bool("json", false, "json output")
 	decodeProto := subFlags.Bool("decode_proto", false, "decode proto files and display them as text")
 	subFlags.Parse(args)
 	if subFlags.NArg() == 0 {
@@ -107,6 +139,7 @@ func commandTopoCat(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.F
 		return err
 	}
 	hasError := false
+	wr.Logger().Printf("[")
 	for _, arg := range resolved {
 		data, version, err := conn.Get(ctx, arg)
 		if err != nil {
@@ -120,7 +153,7 @@ func commandTopoCat(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.F
 		}
 		decoded := ""
 		if *decodeProto {
-			decoded, err = DecodeContent(arg, data)
+			decoded, err = DecodeContent(arg, data, json)
 			if err != nil {
 				wr.Logger().Warningf("TopoCat: cannot proto decode %v: %v", arg, err)
 				decoded = string(data)
@@ -128,11 +161,12 @@ func commandTopoCat(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.F
 		} else {
 			decoded = string(data)
 		}
-		wr.Logger().Printf(decoded)
+		wr.Logger().Printf(decoded + ",")
 		if len(decoded) > 0 && decoded[len(decoded)-1] != '\n' && *long {
 			wr.Logger().Printf("\n")
 		}
 	}
+	wr.Logger().Printf("]")
 	if hasError {
 		return fmt.Errorf("TopoCat: some paths had errors")
 	}