Support JSON marshal of Resources (#654)

* Support JSON marshal of Resources

* Add a test

* Another test

* Fix arch bug

* Fix other test

api/core/key.go

@@ -276,62 +276,62 @@ func (k Key) Defined() bool {
 }
 
 // Type returns a type of the Value.
-func (v *Value) Type() ValueType {
+func (v Value) Type() ValueType {
 	return v.vtype
 }
 
 // AsBool returns the bool value. Make sure that the Value's type is
 // BOOL.
-func (v *Value) AsBool() bool {
+func (v Value) AsBool() bool {
 	return rawToBool(v.numeric)
 }
 
 // AsInt32 returns the int32 value. Make sure that the Value's type is
 // INT32.
-func (v *Value) AsInt32() int32 {
+func (v Value) AsInt32() int32 {
 	return rawToInt32(v.numeric)
 }
 
 // AsInt64 returns the int64 value. Make sure that the Value's type is
 // INT64.
-func (v *Value) AsInt64() int64 {
+func (v Value) AsInt64() int64 {
 	return rawToInt64(v.numeric)
 }
 
 // AsUint32 returns the uint32 value. Make sure that the Value's type
 // is UINT32.
-func (v *Value) AsUint32() uint32 {
+func (v Value) AsUint32() uint32 {
 	return rawToUint32(v.numeric)
 }
 
 // AsUint64 returns the uint64 value. Make sure that the Value's type is
 // UINT64.
-func (v *Value) AsUint64() uint64 {
+func (v Value) AsUint64() uint64 {
 	return rawToUint64(v.numeric)
 }
 
 // AsFloat32 returns the float32 value. Make sure that the Value's
 // type is FLOAT32.
-func (v *Value) AsFloat32() float32 {
+func (v Value) AsFloat32() float32 {
 	return rawToFloat32(v.numeric)
 }
 
 // AsFloat64 returns the float64 value. Make sure that the Value's
 // type is FLOAT64.
-func (v *Value) AsFloat64() float64 {
+func (v Value) AsFloat64() float64 {
 	return rawToFloat64(v.numeric)
 }
 
 // AsString returns the string value. Make sure that the Value's type
 // is STRING.
-func (v *Value) AsString() string {
+func (v Value) AsString() string {
 	return v.stringly
 }
 
 type unknownValueType struct{}
 
 // AsInterface returns Value's data as interface{}.
-func (v *Value) AsInterface() interface{} {
+func (v Value) AsInterface() interface{} {
 	switch v.Type() {
 	case BOOL:
 		return v.AsBool()
@@ -354,7 +354,7 @@ func (v *Value) AsInterface() interface{} {
 }
 
 // Emit returns a string representation of Value's data.
-func (v *Value) Emit() string {
+func (v Value) Emit() string {
 	switch v.Type() {
 	case BOOL:
 		return strconv.FormatBool(v.AsBool())
@@ -378,7 +378,7 @@ func (v *Value) Emit() string {
 }
 
 // MarshalJSON returns the JSON encoding of the Value.
-func (v *Value) MarshalJSON() ([]byte, error) {
+func (v Value) MarshalJSON() ([]byte, error) {
 	var jsonVal struct {
 		Type  string
 		Value interface{}

api/core/key_test.go

@@ -15,12 +15,15 @@
 package core_test
 
 import (
+	"encoding/json"
 	"testing"
 	"unsafe"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/api/core"
+	"go.opentelemetry.io/otel/api/key"
 )
 
 func TestValue(t *testing.T) {
@@ -161,6 +164,19 @@ func TestDefined(t *testing.T) {
 	}
 }
 
+func TestJSONValue(t *testing.T) {
+	var kvs interface{} = [2]core.KeyValue{
+		key.String("A", "B"),
+		key.Int64("C", 1),
+	}
+
+	data, err := json.Marshal(kvs)
+	require.NoError(t, err)
+	require.Equal(t,
+		`[{"Key":"A","Value":{"Type":"STRING","Value":"B"}},{"Key":"C","Value":{"Type":"INT64","Value":1}}]`,
+		string(data))
+}
+
 func TestEmit(t *testing.T) {
 	for _, testcase := range []struct {
 		name string

exporters/trace/stdout/stdout.go

@@ -51,18 +51,6 @@ func NewExporter(o Options) (*Exporter, error) {
 
 // ExportSpan writes a SpanData in json format to stdout.
 func (e *Exporter) ExportSpan(ctx context.Context, data *export.SpanData) {
-	if data.Resource != nil {
-		dataCopy := *data
-		dataCopy.Attributes = append(data.Attributes, data.Resource.Attributes()...)
-		dataCopy.Resource = nil
-		e.exportSpan(ctx, &dataCopy)
-	} else {
-		e.exportSpan(ctx, data)
-	}
-}
-
-// ExportSpan writes a SpanData in json format to stdout.
-func (e *Exporter) exportSpan(ctx context.Context, data *export.SpanData) {
 	var jsonSpan []byte
 	var err error
 	if e.pretty {

exporters/trace/stdout/stdout_test.go

@@ -88,12 +88,7 @@ func TestExporter_ExportSpan(t *testing.T) {
 		`{` +
 		`"Key":"double",` +
 		`"Value":{"Type":"FLOAT64","Value":123.456}` +
-		`},` +
-		`{` +
-		`"Key":"rk1",` +
-		`"Value":{"Type":"STRING","Value":"rv11"}` +
-		`}` +
-		`],` +
+		`}],` +
 		`"MessageEvents":[` +
 		`{` +
 		`"Name":"foo",` +
@@ -124,7 +119,11 @@ func TestExporter_ExportSpan(t *testing.T) {
 		`"DroppedMessageEventCount":0,` +
 		`"DroppedLinkCount":0,` +
 		`"ChildSpanCount":0,` +
-		`"Resource":null}` + "\n"
+		`"Resource":[` +
+		`{` +
+		`"Key":"rk1",` +
+		`"Value":{"Type":"STRING","Value":"rv11"}` +
+		`}]}` + "\n"
 
 	if got != expectedOutput {
 		t.Errorf("Want: %v but got: %v", expectedOutput, got)

sdk/resource/resource.go

@@ -17,6 +17,7 @@
 package resource
 
 import (
+	"encoding/json"
 	"sort"
 	"strings"
 
@@ -109,3 +110,8 @@ func Merge(a, b *Resource) *Resource {
 	kvs = append(kvs, b.sorted...)
 	return New(kvs...)
 }
+
+// MarshalJSON prints the resource attributes in sorted order.
+func (r Resource) MarshalJSON() ([]byte, error) {
+	return json.Marshal(r.sorted)
+}

sdk/resource/resource_test.go

@@ -15,10 +15,12 @@
 package resource_test
 
 import (
+	"encoding/json"
 	"fmt"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/api/core"
 	"go.opentelemetry.io/otel/api/key"
@@ -211,3 +213,12 @@ func TestString(t *testing.T) {
 		}
 	}
 }
+
+func TestMarshalJSON(t *testing.T) {
+	r := resource.New(key.Int64("A", 1), key.String("C", "D"))
+	data, err := json.Marshal(r)
+	require.NoError(t, err)
+	require.Equal(t,
+		`[{"Key":"A","Value":{"Type":"INT64","Value":1}},{"Key":"C","Value":{"Type":"STRING","Value":"D"}}]`,
+		string(data))
+}