util/proto/marshal_test.go

@@ -50,9 +50,6 @@ func TestStableMarshalSingle(t *testing.T) {
 
 			var actualFrostfs generated.Primitives
 			require.NoError(t, actualFrostfs.UnmarshalJSON(r))
-			if len(actualFrostfs.FieldA) == 0 {
-				actualFrostfs.FieldA = nil
-			}
 			require.Equal(t, input, &actualFrostfs)
 
 			primitivesEqual(t, input, &actual)
@@ -110,9 +107,6 @@ func TestStableMarshalSingle(t *testing.T) {
 
 				var actualFrostfs generated.Primitives
 				require.NoError(t, actualFrostfs.UnmarshalJSON(r))
-				if len(actualFrostfs.FieldA) == 0 {
-					actualFrostfs.FieldA = nil
-				}
 				require.Equal(t, tc.input, &actualFrostfs)
 
 				primitivesEqual(t, tc.input, &actual)
@@ -124,9 +118,7 @@ func TestStableMarshalSingle(t *testing.T) {
 func primitivesEqual(t *testing.T, a *generated.Primitives, b *test.Primitives) {
 	// Compare each field directly, because proto-generated code has private fields.
 	require.Equal(t, len(a.FieldA), len(b.FieldA))
-	if len(a.FieldA) != 0 {
-		require.Equal(t, a.FieldA, b.FieldA)
-	}
+	require.Equal(t, a.FieldA, b.FieldA)
 	require.Equal(t, a.FieldB, b.FieldB)
 	require.Equal(t, a.FieldC, b.FieldC)
 	require.Equal(t, a.FieldD, b.FieldD)

util/protogen/internalgengo/json.go

@@ -70,6 +70,24 @@ func emitJSONParseInteger(g *protogen.GeneratedFile, ident string, method string
 	g.P(ident, " := ", typ, "(v)")
 }
 
+func emitJSONReadEnum(g *protogen.GeneratedFile, name string, enumType string) {
+	g.P(`switch v := in.Interface().(type) {
+	case string:
+		if vv, ok := `+enumType+`_value[v]; ok {
+			`+name+` = `+enumType+`(vv)
+			break
+		}
+		vv, err := `, strconvPackage.Ident("ParseInt"), `(v, 10, 32)
+		if err != nil {
+			in.AddError(err)
+			return
+		}
+		`+name+` = `+enumType+`(vv)
+	case float64:
+		`+name+` = `+enumType+`(v)
+	}`)
+}
+
 func emitJSONFieldRead(g *protogen.GeneratedFile, f *protogen.Field, name string) {
 	g.P("{")
 	defer g.P("}")
@@ -94,21 +112,7 @@ func emitJSONFieldRead(g *protogen.GeneratedFile, f *protogen.Field, name string
 
 		enumType := fieldType(g, f).String()
 		g.P("var parsedValue " + enumType)
-		g.P(`switch v := in.Interface().(type) {
-		case string:
-			if vv, ok := `+enumType+`_value[v]; ok {
-				parsedValue = `+enumType+`(vv)
-				break
-			}
-			vv, err := `, strconvPackage.Ident("ParseInt"), `(v, 10, 32)
-			if err != nil {
-				in.AddError(err)
-				return
-			}
-			parsedValue = `+enumType+`(vv)
-		case float64:
-			parsedValue = `+enumType+`(v)
-		}`)
+		emitJSONReadEnum(g, "parsedValue", enumType)
 		template = "%s = parsedValue"
 	case protoreflect.Int32Kind, protoreflect.Sint32Kind, protoreflect.Sfixed32Kind:
 		emitJSONParseInteger(g, "pv", "ParseInt", 32, "int32")
@@ -129,7 +133,17 @@ func emitJSONFieldRead(g *protogen.GeneratedFile, f *protogen.Field, name string
 	case protoreflect.StringKind:
 		template = "%s = in.String()"
 	case protoreflect.BytesKind:
-		template = "%s = in.Bytes()"
+		// Since some time ago proto3 support optional keyword, thus the presence is not tracked by default:
+		// https://github.com/protocolbuffers/protobuf-go/blob/fb995f184a1719ec42b247a3771d1036d92adf67/internal/impl/message_reflect_field.go#L327
+		// We do not explicitly support `optional` keyword, protoc will fail on such fileds.
+		// Thus, treat empty string as `[]byte(nil)`.
+		template = `{
+			tmp := in.Bytes()
+			if len(tmp) == 0 {
+				tmp = nil
+			}
+			%s = tmp
+		}`
 	case protoreflect.MessageKind:
 		if f.Desc.IsList() {
 			g.P("f = ", fieldType(g, f)[2:], "{}")