metadata: switch value encoding to json.RawMessage

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

cache/metadata/metadata.go

@@ -261,8 +261,8 @@ func (s *StorageItem) SetValue(b *bolt.Bucket, key string, v Value) error {
 }
 
 type Value struct {
-	Data  []byte
-	Index string
+	Value json.RawMessage `json:"value,omitempty"`
+	Index string          `json:"index,omitempty"`
 	// External bool
 }
 
@@ -271,11 +271,11 @@ func NewValue(v interface{}) (*Value, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &Value{Data: dt}, nil
+	return &Value{Value: json.RawMessage(dt)}, nil
 }
 
 func (v *Value) Unmarshal(target interface{}) error {
-	err := json.Unmarshal(v.Data, target)
+	err := json.Unmarshal(v.Value, target)
 	return err
 }
 

cmd/buildctl/debug/dumpmetadata.go

@@ -1,11 +1,9 @@
 package debug
 
 import (
-	"encoding/json"
 	"fmt"
 	"path/filepath"
 
-	"github.com/moby/buildkit/cache/metadata"
 	"github.com/urfave/cli"
 )
 
@@ -22,15 +20,7 @@ var DumpMetadataCommand = cli.Command{
 	Action: func(clicontext *cli.Context) error {
 		dbFile := filepath.Join(clicontext.String("root"), "metadata.db")
 		return dumpBolt(dbFile, func(k, v []byte) string {
-			raw := fmt.Sprintf("%q: %q", string(k), string(v))
-			if len(v) == 0 {
-				return raw
-			}
-			var mv metadata.Value
-			if err := json.Unmarshal(v, &mv); err != nil {
-				return raw
-			}
-			return fmt.Sprintf("%q: {\"Data\":%q, \"Index\":%q}", string(k), string(mv.Data), mv.Index)
+			return fmt.Sprintf("%q: %s", string(k), string(v))
 		})
 	},
 }