Seralize struct field interface without hash tag

hash/structhash/structhash.go

@@ -91,15 +91,22 @@ func write(buf *bytes.Buffer, v reflect.Value) *bytes.Buffer {
 			buf.WriteString("nil")
 			return buf
 		}
-		if v.CanInterface() {
-			write(buf, v.Elem())
-		}
+		write(buf, v.Elem())
 	case reflect.Struct:
 		vt := v.Type()
 		items := make([]string, 0)
 		for i := 0; i < v.NumField(); i++ {
 			sf := vt.Field(i)
 			to := parseTag(sf)
+
+			// NOTE: structhash will allow to process all interface types.
+			// gogo/protobuf is not able to set tags for directly oneof interface.
+			// see: https://github.com/gogo/protobuf/issues/623
+			if to.name == "" && reflect.Zero(sf.Type).Kind() == reflect.Interface {
+				to.skip = false
+				to.name = sf.Name
+			}
+
 			if to.skip || to.omitempty && isEmptyValue(v.Field(i)) {
 				continue
 			}
@@ -186,10 +193,16 @@ type tagOptions struct {
 // comma-separated options.
 func parseTag(f reflect.StructField) tagOptions {
 	tag := f.Tag.Get("hash")
-	if tag == "" || tag == "-" {
+	if tag == "" {
+		// NOTE: skip - interface with no tags can still be serialzied
 		return tagOptions{skip: true}
 	}
 
+	if tag == "-" {
+		// force skip - set name for "-"
+		return tagOptions{name: "-", skip: true}
+	}
+
 	var to tagOptions
 	options := strings.Split(tag, ",")
 	for _, option := range options {

hash/structhash/structhash_test.go

@@ -69,6 +69,37 @@ func TestDump(t *testing.T) {
 			}{nil},
 			"{a:nil}",
 		},
+		{
+			struct {
+				a interface{} `hash:"name:a"`
+			}{
+				struct {
+					b map[string]int `hash:"name:b"`
+				}{
+					map[string]int{
+						"c": 1,
+					},
+				},
+			},
+			"{a:{b:(\"c\":1)}}",
+		},
+		// NOTE: structhash will allow to process all interface types.
+		// gogo/protobuf is not able to set tags for directly oneof interface.
+		// see: https://github.com/gogo/protobuf/issues/623
+		{
+			struct {
+				a interface{}
+			}{
+				struct {
+					b map[string]int `hash:"name:b"`
+				}{
+					map[string]int{
+						"c": 1,
+					},
+				},
+			},
+			"{a:{b:(\"c\":1)}}",
+		},
 		{
 			struct {
 				A interface{} `hash:"name:A"`
@@ -112,7 +143,7 @@ func TestDump(t *testing.T) {
 
 	for _, tt := range tests {
 		s := Dump(tt.v)
-		assert.Equalf(t, []byte(tt.s), s, "type %s: %v", reflect.TypeOf(tt.v), tt.v)
+		assert.Equalf(t, tt.s, string(s), "type %s: %v", reflect.TypeOf(tt.v), tt.v)
 	}
 }
 
@@ -185,7 +216,7 @@ func TestTag(t *testing.T) {
 	}
 
 	for _, tt := range tests {
-		assert.Equalf(t, []byte(tt.s), serialize(tt.v), "type %s: %v", reflect.TypeOf(tt.v), tt.v)
+		assert.Equalf(t, tt.s, string(serialize(tt.v)), "type %s: %v", reflect.TypeOf(tt.v), tt.v)
 	}
 }