SERVER-55960 always pass field name to IDL serializer

2 files changed, 10 insertions, 5 deletions

diff --git a/buildscripts/idl/idl/generator.py b/buildscripts/idl/idl/generator.py
index 833004213d4..34747fd6d24 100644
--- a/buildscripts/idl/idl/generator.py
+++ b/buildscripts/idl/idl/generator.py
@@ -1980,7 +1980,11 @@ class _CppSourceFileWriter(_CppFileWriterBase):
                 method_name = writer.get_method_name(field.type.serializer)
                 template_params['method_name'] = method_name
 
-                if field.type.is_array:
+                if field.chained:
+                    # Just directly call the serializer for chained structs without opening up a
+                    # nested document.
+                    self._writer.write_template('${access_member}.${method_name}(builder);')
+                elif field.type.is_array:
                     self._writer.write_template(
                         'BSONArrayBuilder arrayBuilder(builder->subarrayStart(${field_name}));')
                     with self._block('for (const auto& item : ${access_member}) {', '}'):
@@ -1988,7 +1992,8 @@ class _CppSourceFileWriter(_CppFileWriterBase):
                             'BSONObjBuilder subObjBuilder(arrayBuilder.subobjStart());')
                         self._writer.write_template('item.${method_name}(&subObjBuilder);')
                 else:
-                    self._writer.write_template('${access_member}.${method_name}(builder);')
+                    self._writer.write_template(
+                        '${access_member}.${method_name}(${field_name}, builder);')
 
     def _gen_serializer_method_struct(self, field):
         # type: (ast.Field) -> None
diff --git a/src/mongo/idl/basic_types.h b/src/mongo/idl/basic_types.h
index 35516add195..c02366d3c5f 100644
--- a/src/mongo/idl/basic_types.h
+++ b/src/mongo/idl/basic_types.h
@@ -172,14 +172,14 @@ public:
         uasserted(ErrorCodes::FailedToParse, "w has to be a number or string");
     }
 
-    void serializeWriteConcernW(BSONObjBuilder* builder) const {
+    void serializeWriteConcernW(StringData fieldName, BSONObjBuilder* builder) const {
         if (auto stringVal = stdx::get_if<std::string>(&_w)) {
-            builder->append("w", *stringVal);
+            builder->append(fieldName, *stringVal);
             return;
         }
         auto intVal = stdx::get_if<std::int64_t>(&_w);
         invariant(intVal);
-        builder->appendNumber("w", static_cast<long long>(*intVal));
+        builder->appendNumber(fieldName, static_cast<long long>(*intVal));
     }
 
     WriteConcernW() : _w{1}, _usedDefault{true} {};