Updated MessageToJson conversion for FieldMask in CEL C++

common/BUILD

@@ -887,6 +887,7 @@ cc_test(
         "@com_google_absl//absl/types:optional",
         "@com_google_cel_spec//proto/cel/expr/conformance/proto2:test_all_types_cc_proto",
         "@com_google_cel_spec//proto/cel/expr/conformance/proto3:test_all_types_cc_proto",
+        "@com_google_protobuf//:field_mask_cc_proto",
         "@com_google_protobuf//:protobuf",
         "@com_google_protobuf//:struct_cc_proto",
         "@com_google_protobuf//:type_cc_proto",

common/values/parsed_message_value.cc

@@ -34,6 +34,7 @@
 #include "base/attribute.h"
 #include "common/memory.h"
 #include "common/value.h"
+#include "common/values/values.h"
 #include "extensions/protobuf/internal/qualify.h"
 #include "internal/empty_descriptors.h"
 #include "internal/json.h"
@@ -51,8 +52,6 @@ namespace cel {
 
 namespace {
 
-using ::cel::well_known_types::ValueReflection;
-
 template <typename T>
 std::enable_if_t<std::is_base_of_v<google::protobuf::Message, T>,
                  const google::protobuf::Message* absl_nonnull>
@@ -114,12 +113,8 @@ absl::Status ParsedMessageValue::ConvertToJson(
   ABSL_DCHECK_EQ(json->GetDescriptor()->well_known_type(),
                  google::protobuf::Descriptor::WELLKNOWNTYPE_VALUE);
 
-  ValueReflection value_reflection;
-  CEL_RETURN_IF_ERROR(value_reflection.Initialize(json->GetDescriptor()));
-  google::protobuf::Message* json_object = value_reflection.MutableStructValue(json);
-
   return internal::MessageToJson(*value_, descriptor_pool, message_factory,
-                                 json_object);
+                                 json);
 }
 
 absl::Status ParsedMessageValue::ConvertToJsonObject(

common/values/parsed_message_value_test.cc

@@ -14,6 +14,7 @@
 
 #include <utility>
 
+#include "google/protobuf/field_mask.pb.h"
 #include "google/protobuf/struct.pb.h"
 #include "absl/status/status_matchers.h"
 #include "absl/strings/cord.h"
@@ -84,6 +85,19 @@ TEST_F(ParsedMessageValueTest, ConvertToJson) {
                          R"pb(struct_value: {})pb"));
 }
 
+TEST_F(ParsedMessageValueTest, ConvertToJsonFieldMask) {
+  ParsedMessageValue value =
+      MakeParsedMessage<google::protobuf::FieldMask>(R"pb(paths: "foo.bar"
+                                                          paths: "baz")pb");
+  google::protobuf::Message* json =
+      DynamicParseTextProto<google::protobuf::Value>(R"pb()pb");
+  ASSERT_THAT(value.ConvertToJson(descriptor_pool(), message_factory(),
+                                  cel::to_address(json)),
+              IsOk());
+  EXPECT_THAT(*json, EqualsTextProto<google::protobuf::Value>(
+                         R"pb(string_value: "foo.bar,baz")pb"));
+}
+
 TEST_F(ParsedMessageValueTest, Equal) {
   MessageValue value = MakeParsedMessage<TestAllTypesProto3>();
   EXPECT_THAT(

conformance/BUILD

@@ -175,8 +175,6 @@ _TESTS_TO_SKIP = [
     "namespace/namespace/self_eval_container_lookup,self_eval_container_lookup_unchecked",
 
     # Skip until fixed.
-    "wrappers/field_mask/to_json",
-    "wrappers/empty/to_json",
     "fields/qualified_identifier_resolution/map_value_repeat_key_heterogeneous",
 
     # Future features for CEL 1.0

eval/public/structs/BUILD

@@ -71,6 +71,7 @@ cc_library(
         "@com_google_absl//absl/base:nullability",
         "@com_google_absl//absl/functional:overload",
         "@com_google_absl//absl/log:absl_check",
+        "@com_google_absl//absl/log:absl_log",
         "@com_google_absl//absl/status",
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
@@ -111,9 +112,11 @@ cc_test(
         "@com_google_absl//absl/status",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/time",
+        "@com_google_absl//absl/types:span",
         "@com_google_protobuf//:any_cc_proto",
         "@com_google_protobuf//:duration_cc_proto",
         "@com_google_protobuf//:empty_cc_proto",
+        "@com_google_protobuf//:field_mask_cc_proto",
         "@com_google_protobuf//:protobuf",
         "@com_google_protobuf//:struct_cc_proto",
         "@com_google_protobuf//:wrappers_cc_proto",
@@ -218,6 +221,7 @@ cc_test(
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/time",
+        "@com_google_absl//absl/types:span",
         "@com_google_protobuf//:any_cc_proto",
         "@com_google_protobuf//:duration_cc_proto",
         "@com_google_protobuf//:empty_cc_proto",

eval/public/structs/cel_proto_wrap_util.cc

@@ -17,6 +17,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <limits>
+#include <optional>
 #include <string>
 #include <type_traits>
 #include <utility>
@@ -31,6 +32,7 @@
 #include "absl/base/optimization.h"
 #include "absl/functional/overload.h"
 #include "absl/log/absl_check.h"
+#include "absl/log/absl_log.h"
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/cord.h"
@@ -50,6 +52,7 @@
 #include "internal/well_known_types.h"
 #include "google/protobuf/arena.h"
 #include "google/protobuf/descriptor.h"
+#include "google/protobuf/json/json.h"
 #include "google/protobuf/message.h"
 #include "google/protobuf/message_lite.h"
 
@@ -79,6 +82,8 @@ using google::protobuf::Descriptor;
 using google::protobuf::DescriptorPool;
 using google::protobuf::Message;
 using google::protobuf::MessageFactory;
+using google::protobuf::json::MessageToJsonString;
+using google::protobuf::json::PrintOptions;
 
 // kMaxIntJSON is defined as the Number.MAX_SAFE_INTEGER value per EcmaScript 6.
 constexpr int64_t kMaxIntJSON = (1ll << 53) - 1;
@@ -98,6 +103,27 @@ static bool IsJSONSafe(uint64_t i) {
   return i <= static_cast<uint64_t>(kMaxIntJSON);
 }
 
+static std::optional<std::string> GetFieldMaskJsonString(
+    const google::protobuf::Message& message) {
+  // TODO(b/540507668): Refactor to pipe descriptor_pool through
+  // ValueFromValue to use internal::MessageToJson.
+  PrintOptions json_options;
+  std::string json_str;
+  auto status = MessageToJsonString(message, &json_str, json_options);
+  if (!status.ok()) {
+    ABSL_LOG(ERROR) << "Failed to convert FieldMask to JSON: " << status;
+    return std::nullopt;
+  }
+  // If JSON marshalling is correct, we know we'll always get a plain
+  // JSON string value and it shouldn't contain any escapes that we need
+  // to interpret.
+  if (json_str.size() >= 2 && json_str.front() == '"' &&
+      json_str.back() == '"') {
+    return json_str.substr(1, json_str.size() - 2);
+  }
+  return json_str;
+}
+
 // Map implementation wrapping google.protobuf.ListValue
 class DynamicList : public CelList {
  public:
@@ -1079,6 +1105,25 @@ google::protobuf::Message* ValueFromValue(google::protobuf::Message* message, co
         return message;
       }
     } break;
+    case CelValue::Type::kMessage: {
+      const google::protobuf::Message* message_ptr = value.MessageOrDie();
+      if (message_ptr->GetDescriptor()->full_name() ==
+          "google.protobuf.Empty") {
+        reflection.MutableStructValue(message);
+        return message;
+      }
+      if (message_ptr->GetDescriptor()->full_name() ==
+          "google.protobuf.FieldMask") {
+        std::optional<std::string> fm_str =
+            GetFieldMaskJsonString(*message_ptr);
+        if (fm_str.has_value()) {
+          reflection.SetStringValue(message, *fm_str);
+          return message;
+        }
+        return nullptr;
+      }
+      return nullptr;
+    } break;
     case CelValue::Type::kNullType:
       reflection.SetNullValue(message);
       return message;
@@ -1229,6 +1274,25 @@ bool ValueFromValue(Value* json, const CelValue& value, google::protobuf::Arena*
       return ListFromValue(json->mutable_list_value(), value, arena);
     case CelValue::Type::kMap:
       return StructFromValue(json->mutable_struct_value(), value, arena);
+    case CelValue::Type::kMessage: {
+      const google::protobuf::Message* message_ptr = value.MessageOrDie();
+      if (message_ptr->GetDescriptor()->full_name() ==
+          "google.protobuf.Empty") {
+        json->mutable_struct_value();
+        return true;
+      }
+      if (message_ptr->GetDescriptor()->full_name() ==
+          "google.protobuf.FieldMask") {
+        std::optional<std::string> fm_str =
+            GetFieldMaskJsonString(*message_ptr);
+        if (fm_str.has_value()) {
+          json->set_string_value(*fm_str);
+          return true;
+        }
+        return false;
+      }
+      return false;
+    }
     case CelValue::Type::kNullType:
       json->set_null_value(protobuf::NULL_VALUE);
       return true;
@@ -1254,7 +1318,7 @@ google::protobuf::Message* AnyFromValue(const google::protobuf::Message* prototy
     case CelValue::Type::kBytes: {
       BytesValue v;
       type_name = v.GetTypeName();
-      v.set_value(std::string(value.BytesOrDie().value()));
+      v.set_value(value.BytesOrDie().value());
       payload = v.SerializeAsCord();
     } break;
     case CelValue::Type::kDouble: {