Fix default value of enum(int) in json_util with proto2 (#8835)

src/google/protobuf/util/internal/default_value_objectwriter.cc

@@ -411,16 +411,33 @@ void DefaultValueObjectWriter::MaybePopulateChildrenOfAny(Node* node) {
 DataPiece DefaultValueObjectWriter::FindEnumDefault(
     const google::protobuf::Field& field, const TypeInfo* typeinfo,
     bool use_ints_for_enums) {
-  if (!field.default_value().empty())
-    return DataPiece(field.default_value(), true);
-
   const google::protobuf::Enum* enum_type =
       typeinfo->GetEnumByTypeUrl(field.type_url());
   if (!enum_type) {
     GOOGLE_LOG(WARNING) << "Could not find enum with type '" << field.type_url()
                  << "'";
     return DataPiece::NullData();
   }
+  if (!field.default_value().empty()) {
+    if (!use_ints_for_enums) {
+      return DataPiece(field.default_value(), true);
+    } else {
+      const std::string& enum_default_value_name = field.default_value();
+      for (int enum_index = 0;
+          enum_index < enum_type->enumvalue_size();
+          ++enum_index) {
+        auto& enum_value = enum_type->enumvalue(enum_index);
+        if (enum_value.name() == enum_default_value_name)
+          return DataPiece(enum_value.number());
+      }
+      GOOGLE_LOG(WARNING) << "Could not find enum value '"
+                          << enum_default_value_name
+                          << "' with type '"
+                          << field.type_url()
+                          << "'";
+      return DataPiece::NullData();
+    }
+  }
   // We treat the first value as the default if none is specified.
   return enum_type->enumvalue_size() > 0
              ? (use_ints_for_enums

src/google/protobuf/util/json_format.proto

@@ -128,3 +128,13 @@ message TestExtension {
   }
   optional string value = 1;
 }
+
+enum EnumValue {
+  PROTOCOL = 0;
+  BUFFER = 1;
+  DEFAULT = 2;
+}
+
+message TestDefaultEnumValue {
+  optional EnumValue enum_value = 1 [default = DEFAULT];
+}

src/google/protobuf/util/json_util_test.cc

@@ -241,6 +241,25 @@ TEST_F(JsonUtilTest, TestPrintEnumsAsIntsWithDefaultValue) {
   EXPECT_EQ(proto3::BAR, parsed.enum_value3());
 }
 
+TEST_F(JsonUtilTest, TestPrintProto2EnumAsIntWithDefaultValue) {
+  protobuf_unittest::TestDefaultEnumValue orig;
+
+  JsonPrintOptions print_options;
+  // use enum as int
+  print_options.always_print_enums_as_ints = true;
+  print_options.always_print_primitive_fields = true;
+
+  // result should be int rather than string
+  std::string expected_json = "{\"enumValue\":2}";
+  EXPECT_EQ(expected_json, ToJson(orig, print_options));
+
+  protobuf_unittest::TestDefaultEnumValue parsed;
+  JsonParseOptions parse_options;
+  ASSERT_TRUE(FromJson(expected_json, &parsed, parse_options));
+
+  EXPECT_EQ(protobuf_unittest::DEFAULT, parsed.enum_value());
+}
+
 TEST_F(JsonUtilTest, ParseMessage) {
   // Some random message but good enough to verify that the parsing wrapper
   // functions are working properly.