Fix reflection based parser for map entries with closed enum values.

If the value of the parsed enum is unknown, the whole entry has to be moved to
the unknown field set.

PiperOrigin-RevId: 505175979

src/google/protobuf/map_test.inc

@@ -2708,9 +2708,7 @@ TEST(GeneratedMapFieldTest, Proto2UnknownEnum) {
   UNITTEST::TestEnumMap to;
   EXPECT_TRUE(to.ParseFromString(data));
   EXPECT_EQ(0, to.unknown_map_field().size());
-  const UnknownFieldSet& unknown_field_set =
-      to.GetReflection()->GetUnknownFields(to);
-  EXPECT_EQ(1, unknown_field_set.field_count());
+  EXPECT_EQ(1, to.GetReflection()->GetUnknownFields(to).field_count());
   EXPECT_EQ(1, to.known_map_field().size());
   EXPECT_EQ(UNITTEST::PROTO2_MAP_ENUM_FOO, to.known_map_field().at(0));
 
@@ -2723,6 +2721,20 @@ TEST(GeneratedMapFieldTest, Proto2UnknownEnum) {
   EXPECT_EQ(UNITTEST::E_PROTO2_MAP_ENUM_FOO, from.known_map_field().at(0));
   EXPECT_EQ(1, from.unknown_map_field().size());
   EXPECT_EQ(UNITTEST::E_PROTO2_MAP_ENUM_EXTRA, from.unknown_map_field().at(0));
+
+  // Test the same behavior with the reflection based parser.
+  to.Clear();
+  const char* ptr;
+  internal::ParseContext ctx(io::CodedInputStream::GetDefaultRecursionLimit(),
+                             false, &ptr, data);
+  ptr = WireFormat::_InternalParse(&to, ptr, &ctx);
+  ASSERT_TRUE(ptr);
+  ASSERT_TRUE(ctx.EndedAtLimit());
+
+  EXPECT_EQ(0, to.unknown_map_field().size());
+  EXPECT_EQ(1, to.GetReflection()->GetUnknownFields(to).field_count());
+  EXPECT_EQ(1, to.known_map_field().size());
+  EXPECT_EQ(UNITTEST::PROTO2_MAP_ENUM_FOO, to.known_map_field().at(0));
 }
 
 TEST(GeneratedMapFieldTest, StandardWireFormat) {

src/google/protobuf/wire_format.cc

@@ -1030,7 +1030,25 @@ const char* WireFormat::_InternalParseAndMergeField(
         sub_message =
             reflection->MutableMessage(msg, field, ctx->data().factory);
       }
-      return ctx->ParseMessage(sub_message, ptr);
+      ptr = ctx->ParseMessage(sub_message, ptr);
+
+      // For map entries, if the value is an unknown enum we have to push it
+      // into the unknown field set and remove it from the list.
+      if (ptr != nullptr && field->is_map()) {
+        auto* value_field = field->message_type()->map_value();
+        auto* enum_type = value_field->enum_type();
+        if (enum_type != nullptr &&
+            !internal::cpp::HasPreservingUnknownEnumSemantics(value_field) &&
+            enum_type->FindValueByNumber(
+                sub_message->GetReflection()->GetEnumValue(
+                    *sub_message, value_field)) == nullptr) {
+          reflection->MutableUnknownFields(msg)->AddLengthDelimited(
+              field->number(), sub_message->SerializeAsString());
+          reflection->RemoveLast(msg, field);
+        }
+      }
+
+      return ptr;
     }
   }