Fix jsonpb to emit zero values for Map, Slice, Ptr when EmitDefaults=true

When jsonpb.Marshaler.EmitDefaults is set to true, marshal zero values of the 
following types accordingly:
Map to {}
Slice to []
Ptr to null

jsonpb/jsonpb.go

@@ -207,7 +207,7 @@ func (m *Marshaler) marshalObject(out *errWriter, v proto.Message, indent, typeU
 
 		// IsNil will panic on most value kinds.
 		switch value.Kind() {
-		case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
+		case reflect.Chan, reflect.Func, reflect.Interface:
 			if value.IsNil() {
 				continue
 			}
@@ -235,6 +235,10 @@ func (m *Marshaler) marshalObject(out *errWriter, v proto.Message, indent, typeU
 				if value.Len() == 0 {
 					continue
 				}
+			case reflect.Map, reflect.Ptr, reflect.Slice:
+				if value.IsNil() {
+					continue
+				}
 			}
 		}
 
@@ -402,6 +406,12 @@ func (m *Marshaler) marshalValue(out *errWriter, prop *proto.Properties, v refle
 	var err error
 	v = reflect.Indirect(v)
 
+	// Handle nil pointer
+	if v.Kind() == reflect.Invalid {
+		out.write("null")
+		return out.err
+	}
+
 	// Handle repeated elements.
 	if v.Kind() == reflect.Slice && v.Type().Elem().Kind() != reflect.Uint8 {
 		out.write("[")

jsonpb/jsonpb_test.go

@@ -350,6 +350,9 @@ var marshalingTests = []struct {
 		`{"rFunny":[1,2]}`},
 	{"empty value", marshaler, &pb.Simple3{}, `{}`},
 	{"empty value emitted", Marshaler{EmitDefaults: true}, &pb.Simple3{}, `{"dub":0}`},
+	{"empty repeated emitted", Marshaler{EmitDefaults: true}, &pb.SimpleSlice3{}, `{"slices":[]}`},
+	{"empty map emitted", Marshaler{EmitDefaults: true}, &pb.SimpleMap3{}, `{"stringy":{}}`},
+	{"nested struct null", Marshaler{EmitDefaults: true}, &pb.SimpleNull3{}, `{"simple":null}`},
 	{"map<int64, int32>", marshaler, &pb.Mappy{Nummy: map[int64]int32{1: 2, 3: 4}}, `{"nummy":{"1":2,"3":4}}`},
 	{"map<int64, int32>", marshalerAllOptions, &pb.Mappy{Nummy: map[int64]int32{1: 2, 3: 4}}, nummyPrettyJSON},
 	{"map<string, string>", marshaler,

jsonpb/jsonpb_test_proto/more_test_objects.pb.go

@@ -10,6 +10,9 @@ It is generated from these files:
 
 It has these top-level messages:
 	Simple3
+	SimpleSlice3
+	SimpleMap3
+	SimpleNull3
 	Mappy
 	Simple
 	Repeats
@@ -77,6 +80,54 @@ func (m *Simple3) GetDub() float64 {
 	return 0
 }
 
+type SimpleSlice3 struct {
+	Slices []string `protobuf:"bytes,1,rep,name=slices" json:"slices,omitempty"`
+}
+
+func (m *SimpleSlice3) Reset()                    { *m = SimpleSlice3{} }
+func (m *SimpleSlice3) String() string            { return proto.CompactTextString(m) }
+func (*SimpleSlice3) ProtoMessage()               {}
+func (*SimpleSlice3) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }
+
+func (m *SimpleSlice3) GetSlices() []string {
+	if m != nil {
+		return m.Slices
+	}
+	return nil
+}
+
+type SimpleMap3 struct {
+	Stringy map[string]string `protobuf:"bytes,1,rep,name=stringy" json:"stringy,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
+}
+
+func (m *SimpleMap3) Reset()                    { *m = SimpleMap3{} }
+func (m *SimpleMap3) String() string            { return proto.CompactTextString(m) }
+func (*SimpleMap3) ProtoMessage()               {}
+func (*SimpleMap3) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{2} }
+
+func (m *SimpleMap3) GetStringy() map[string]string {
+	if m != nil {
+		return m.Stringy
+	}
+	return nil
+}
+
+type SimpleNull3 struct {
+	Simple *Simple3 `protobuf:"bytes,1,opt,name=simple" json:"simple,omitempty"`
+}
+
+func (m *SimpleNull3) Reset()                    { *m = SimpleNull3{} }
+func (m *SimpleNull3) String() string            { return proto.CompactTextString(m) }
+func (*SimpleNull3) ProtoMessage()               {}
+func (*SimpleNull3) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{3} }
+
+func (m *SimpleNull3) GetSimple() *Simple3 {
+	if m != nil {
+		return m.Simple
+	}
+	return nil
+}
+
 type Mappy struct {
 	Nummy    map[int64]int32    `protobuf:"bytes,1,rep,name=nummy" json:"nummy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
 	Strry    map[string]string  `protobuf:"bytes,2,rep,name=strry" json:"strry,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
@@ -93,7 +144,7 @@ type Mappy struct {
 func (m *Mappy) Reset()                    { *m = Mappy{} }
 func (m *Mappy) String() string            { return proto.CompactTextString(m) }
 func (*Mappy) ProtoMessage()               {}
-func (*Mappy) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }
+func (*Mappy) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{4} }
 
 func (m *Mappy) GetNummy() map[int64]int32 {
 	if m != nil {
@@ -167,6 +218,9 @@ func (m *Mappy) GetU64Booly() map[uint64]bool {
 
 func init() {
 	proto.RegisterType((*Simple3)(nil), "jsonpb.Simple3")
+	proto.RegisterType((*SimpleSlice3)(nil), "jsonpb.SimpleSlice3")
+	proto.RegisterType((*SimpleMap3)(nil), "jsonpb.SimpleMap3")
+	proto.RegisterType((*SimpleNull3)(nil), "jsonpb.SimpleNull3")
 	proto.RegisterType((*Mappy)(nil), "jsonpb.Mappy")
 	proto.RegisterEnum("jsonpb.Numeral", Numeral_name, Numeral_value)
 }
@@ -174,33 +228,38 @@ func init() {
 func init() { proto.RegisterFile("more_test_objects.proto", fileDescriptor0) }
 
 var fileDescriptor0 = []byte{
-	// 444 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x8c, 0x94, 0xc1, 0x6b, 0xdb, 0x30,
-	0x14, 0x87, 0xe7, 0xa4, 0x4e, 0xec, 0x17, 0xba, 0x19, 0x31, 0x98, 0x58, 0x2f, 0xa1, 0x30, 0x08,
-	0x83, 0xf9, 0x90, 0x8c, 0xad, 0x6c, 0xa7, 0x74, 0xf4, 0x50, 0x46, 0x1d, 0x70, 0x09, 0x3b, 0x96,
-	0x78, 0x13, 0x65, 0x9e, 0x6d, 0x19, 0xdb, 0x1a, 0xe8, 0x8f, 0x1f, 0x8c, 0x27, 0xcb, 0xb5, 0x6c,
-	0x14, 0xd2, 0x9b, 0xcc, 0xef, 0xfb, 0xf2, 0x9e, 0xf4, 0x1e, 0x81, 0x37, 0x39, 0xaf, 0xd8, 0x43,
-	0xc3, 0xea, 0xe6, 0x81, 0x27, 0x29, 0xfb, 0xd9, 0xd4, 0x61, 0x59, 0xf1, 0x86, 0x93, 0x59, 0x5a,
-	0xf3, 0xa2, 0x4c, 0x2e, 0x2f, 0x60, 0x7e, 0xff, 0x3b, 0x2f, 0x33, 0xb6, 0x21, 0x01, 0x4c, 0x7f,
-	0x89, 0x84, 0x3a, 0x4b, 0x67, 0xe5, 0xc4, 0x78, 0xbc, 0xfc, 0xe7, 0x81, 0x7b, 0x77, 0x28, 0x4b,
-	0x49, 0x42, 0x70, 0x0b, 0x91, 0xe7, 0x92, 0x3a, 0xcb, 0xe9, 0x6a, 0xb1, 0xa6, 0x61, 0xab, 0x87,
-	0x2a, 0x0d, 0x23, 0x8c, 0x6e, 0x8a, 0xa6, 0x92, 0x71, 0x8b, 0x21, 0x5f, 0x37, 0x55, 0x25, 0xe9,
-	0xc4, 0xc6, 0xdf, 0x63, 0xa4, 0x79, 0x85, 0x21, 0xcf, 0x93, 0x34, 0x95, 0x74, 0x6a, 0xe3, 0x77,
-	0x18, 0x69, 0x5e, 0x61, 0xc8, 0x27, 0xe2, 0xf1, 0x51, 0xd2, 0x33, 0x1b, 0x7f, 0x8d, 0x91, 0xe6,
-	0x15, 0xa6, 0x78, 0xce, 0x33, 0x49, 0x5d, 0x2b, 0x8f, 0x51, 0xc7, 0xe3, 0x19, 0x79, 0x56, 0x88,
-	0x5c, 0xd2, 0x99, 0x8d, 0xbf, 0xc1, 0x48, 0xf3, 0x0a, 0x23, 0x9f, 0xc1, 0xab, 0x37, 0xeb, 0xb6,
-	0xc4, 0x5c, 0x29, 0x17, 0xa3, 0x2b, 0xeb, 0xb4, 0xb5, 0x9e, 0x60, 0x25, 0x7e, 0xfa, 0xd8, 0x8a,
-	0x9e, 0x55, 0xd4, 0x69, 0x27, 0xea, 0x4f, 0x14, 0x45, 0x57, 0xd1, 0xb7, 0x89, 0xfb, 0x61, 0x45,
-	0x61, 0x54, 0x14, 0x5d, 0x45, 0xb0, 0x8a, 0xc3, 0x8a, 0x1d, 0xfc, 0xf6, 0x0a, 0xa0, 0x1f, 0x34,
-	0x6e, 0xcb, 0x1f, 0x26, 0xd5, 0xb6, 0x4c, 0x63, 0x3c, 0x92, 0xd7, 0xe0, 0xfe, 0x3d, 0x64, 0x82,
-	0xd1, 0xc9, 0xd2, 0x59, 0xb9, 0x71, 0xfb, 0xf1, 0x65, 0x72, 0xe5, 0xa0, 0xd9, 0x8f, 0xdc, 0x34,
-	0x7d, 0x8b, 0xe9, 0x9b, 0xe6, 0x2d, 0x40, 0x3f, 0x7c, 0xd3, 0x74, 0x5b, 0xf3, 0x9d, 0x69, 0x2e,
-	0xd6, 0xaf, 0xba, 0x9b, 0xe8, 0x9d, 0x1e, 0x35, 0xd1, 0xef, 0xc5, 0xa9, 0xf6, 0xfd, 0xb1, 0xf9,
-	0xf4, 0x20, 0xa6, 0xe9, 0x59, 0x4c, 0x6f, 0xd4, 0x7e, 0xbf, 0x2b, 0x96, 0x8b, 0x0f, 0xda, 0x7f,
-	0xd9, 0xb7, 0x1f, 0x89, 0x9c, 0x55, 0x87, 0xcc, 0xfc, 0xa9, 0xaf, 0x70, 0x3e, 0xd8, 0x21, 0xcb,
-	0x63, 0x1c, 0xef, 0x03, 0x65, 0x73, 0xaa, 0xa7, 0xae, 0x3f, 0x96, 0xf7, 0xc7, 0x2a, 0x9f, 0x3f,
-	0x47, 0x3e, 0x56, 0xf9, 0xec, 0x84, 0xfc, 0xfe, 0x03, 0xcc, 0xf5, 0x4b, 0x90, 0x05, 0xcc, 0xf7,
-	0xd1, 0xf7, 0x68, 0xf7, 0x23, 0x0a, 0x5e, 0x10, 0x80, 0xd9, 0x36, 0xde, 0x5e, 0xdf, 0x7e, 0x0b,
-	0x1c, 0xe2, 0x83, 0x1b, 0xef, 0xee, 0xb6, 0x51, 0x30, 0x49, 0x66, 0xea, 0xaf, 0x6d, 0xf3, 0x3f,
-	0x00, 0x00, 0xff, 0xff, 0xa2, 0x4b, 0xe1, 0x77, 0xf5, 0x04, 0x00, 0x00,
+	// 526 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x94, 0x94, 0xdd, 0x6b, 0xdb, 0x3c,
+	0x14, 0x87, 0x5f, 0x27, 0xf5, 0xd7, 0x49, 0xfb, 0x2e, 0x88, 0xb1, 0x99, 0xf4, 0x62, 0xc5, 0xb0,
+	0xad, 0x0c, 0xe6, 0x8b, 0x78, 0x74, 0x5d, 0x77, 0x95, 0x8e, 0x5e, 0x94, 0x11, 0x07, 0x1c, 0xc2,
+	0x2e, 0x4b, 0xdc, 0x99, 0x90, 0xcc, 0x5f, 0xd8, 0xd6, 0xc0, 0xd7, 0xfb, 0xbb, 0x07, 0xe3, 0x48,
+	0x72, 0x2d, 0x07, 0x85, 0x6c, 0x77, 0x52, 0x7e, 0xcf, 0xe3, 0x73, 0x24, 0x1d, 0x02, 0x2f, 0xd3,
+	0xbc, 0x8c, 0x1f, 0xea, 0xb8, 0xaa, 0x1f, 0xf2, 0x68, 0x17, 0x3f, 0xd6, 0x95, 0x57, 0x94, 0x79,
+	0x9d, 0x13, 0x63, 0x57, 0xe5, 0x59, 0x11, 0xb9, 0xe7, 0x60, 0x2e, 0xb7, 0x69, 0x91, 0xc4, 0x3e,
+	0x19, 0xc3, 0xf0, 0x3b, 0x8d, 0x1c, 0xed, 0x42, 0xbb, 0xd4, 0x42, 0x5c, 0xba, 0x6f, 0xe0, 0x94,
+	0x87, 0xcb, 0x64, 0xfb, 0x18, 0xfb, 0xe4, 0x05, 0x18, 0x15, 0xae, 0x2a, 0x47, 0xbb, 0x18, 0x5e,
+	0xda, 0xa1, 0xd8, 0xb9, 0xbf, 0x34, 0x00, 0x0e, 0xce, 0xd7, 0x85, 0x4f, 0x3e, 0x81, 0x59, 0xd5,
+	0xe5, 0x36, 0xdb, 0x34, 0x8c, 0x1b, 0x4d, 0x5f, 0x79, 0xbc, 0x9a, 0xd7, 0x41, 0xde, 0x92, 0x13,
+	0x77, 0x59, 0x5d, 0x36, 0x61, 0xcb, 0x4f, 0x6e, 0xe0, 0x54, 0x0e, 0xb0, 0xa7, 0x1f, 0x71, 0xc3,
+	0x7a, 0xb2, 0x43, 0x5c, 0x92, 0xe7, 0xa0, 0xff, 0x5c, 0x27, 0x34, 0x76, 0x06, 0xec, 0x37, 0xbe,
+	0xb9, 0x19, 0x5c, 0x6b, 0xee, 0x15, 0x8c, 0xf8, 0xf7, 0x03, 0x9a, 0x24, 0x3e, 0x79, 0x0b, 0x46,
+	0xc5, 0xb6, 0xcc, 0x1e, 0x4d, 0x9f, 0xf5, 0x9b, 0xf0, 0x43, 0x11, 0xbb, 0xbf, 0x2d, 0xd0, 0xe7,
+	0xeb, 0xa2, 0x68, 0x88, 0x07, 0x7a, 0x46, 0xd3, 0xb4, 0x6d, 0xdb, 0x69, 0x0d, 0x96, 0x7a, 0x01,
+	0x46, 0xbc, 0x5f, 0x8e, 0x21, 0x5f, 0xd5, 0x65, 0xd9, 0x38, 0x03, 0x15, 0xbf, 0xc4, 0x48, 0xf0,
+	0x0c, 0x43, 0x3e, 0x8f, 0x76, 0xbb, 0xc6, 0x19, 0xaa, 0xf8, 0x05, 0x46, 0x82, 0x67, 0x18, 0xf2,
+	0x11, 0xdd, 0x6c, 0x1a, 0xe7, 0x44, 0xc5, 0xdf, 0x62, 0x24, 0x78, 0x86, 0x31, 0x3e, 0xcf, 0x93,
+	0xc6, 0xd1, 0x95, 0x3c, 0x46, 0x2d, 0x8f, 0x6b, 0xe4, 0xe3, 0x8c, 0xa6, 0x8d, 0x63, 0xa8, 0xf8,
+	0x3b, 0x8c, 0x04, 0xcf, 0x30, 0xf2, 0x11, 0xac, 0xca, 0x9f, 0xf2, 0x12, 0x26, 0x53, 0xce, 0xf7,
+	0x8e, 0x2c, 0x52, 0x6e, 0x3d, 0xc1, 0x4c, 0xbc, 0xfa, 0xc0, 0x45, 0x4b, 0x29, 0x8a, 0xb4, 0x15,
+	0xc5, 0x16, 0x45, 0xda, 0x56, 0xb4, 0x55, 0xe2, 0xaa, 0x5f, 0x91, 0x4a, 0x15, 0x69, 0x5b, 0x11,
+	0x94, 0x62, 0xbf, 0x62, 0x0b, 0x4f, 0xae, 0x01, 0xba, 0x87, 0x96, 0xe7, 0x6f, 0xa8, 0x98, 0x3f,
+	0x5d, 0x9a, 0x3f, 0x34, 0xbb, 0x27, 0xff, 0x97, 0xc9, 0x9d, 0xdc, 0x03, 0x74, 0x8f, 0x2f, 0x9b,
+	0x3a, 0x37, 0x5f, 0xcb, 0xa6, 0x62, 0x92, 0xfb, 0x4d, 0x74, 0x73, 0x71, 0xac, 0x7d, 0x7b, 0xdf,
+	0x7c, 0xba, 0x10, 0xd9, 0xb4, 0x14, 0xa6, 0xb5, 0xd7, 0x7e, 0x37, 0x2b, 0x8a, 0x83, 0xf7, 0xda,
+	0xff, 0xbf, 0x6b, 0x3f, 0xa0, 0x69, 0x5c, 0xae, 0x13, 0xf9, 0x53, 0x9f, 0xe1, 0xac, 0x37, 0x43,
+	0x8a, 0xcb, 0x38, 0xdc, 0x07, 0xca, 0xf2, 0xab, 0x1e, 0x3b, 0xfe, 0xbe, 0xbc, 0x3a, 0x54, 0xf9,
+	0xec, 0x6f, 0xe4, 0x43, 0x95, 0x4f, 0x8e, 0xc8, 0xef, 0xde, 0x83, 0x29, 0x6e, 0x82, 0x8c, 0xc0,
+	0x5c, 0x05, 0x5f, 0x83, 0xc5, 0xb7, 0x60, 0xfc, 0x1f, 0x01, 0x30, 0x66, 0xe1, 0xec, 0xf6, 0xfe,
+	0xcb, 0x58, 0x23, 0x36, 0xe8, 0xe1, 0x62, 0x3e, 0x0b, 0xc6, 0x83, 0xc8, 0x60, 0x7f, 0xe0, 0xfe,
+	0x9f, 0x00, 0x00, 0x00, 0xff, 0xff, 0xdc, 0x84, 0x34, 0xaf, 0xdb, 0x05, 0x00, 0x00,
 }

jsonpb/jsonpb_test_proto/more_test_objects.proto

@@ -37,6 +37,18 @@ message Simple3 {
   double dub = 1;
 }
 
+message SimpleSlice3 {
+  repeated string slices = 1;
+}
+
+message SimpleMap3 {
+  map<string,string> stringy = 1;
+}
+
+message SimpleNull3 {
+  Simple3 simple = 1;
+}
+
 enum Numeral {
   UNKNOWN = 0;
   ARABIC = 1;