Use dedicated helper functions for map descriptors (#9099)

The Descriptor class now has map_key() and map_value() methods for
accessing the special key and value fields in generated map entry
messages. This commit updates all the relevant code to use these
accessors instead of the clunkier FindFieldByName("key") or
FindFieldByName("value") approach.

python/google/protobuf/pyext/message.cc

@@ -1074,7 +1074,7 @@ int InitAttributes(CMessage* self, PyObject* args, PyObject* kwargs) {
     if (descriptor->is_map()) {
       ScopedPyObjectPtr map(GetFieldValue(self, descriptor));
       const FieldDescriptor* value_descriptor =
-          descriptor->message_type()->FindFieldByName("value");
+          descriptor->message_type()->map_value();
       if (value_descriptor->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
         ScopedPyObjectPtr iter(PyObject_GetIter(value));
         if (iter == NULL) {
@@ -2582,7 +2582,7 @@ PyObject* GetFieldValue(CMessage* self,
   ContainerBase* py_container = nullptr;
   if (field_descriptor->is_map()) {
     const Descriptor* entry_type = field_descriptor->message_type();
-    const FieldDescriptor* value_type = entry_type->FindFieldByName("value");
+    const FieldDescriptor* value_type = entry_type->map_value();
     if (value_type->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
       CMessageClass* value_class = message_factory::GetMessageClass(
           GetFactoryForMessage(self), value_type->message_type());

src/google/protobuf/compiler/cpp/cpp_map_field.cc

@@ -54,9 +54,9 @@ void SetMessageVariables(const FieldDescriptor* descriptor,
   (*variables)["full_name"] = descriptor->full_name();
 
   const FieldDescriptor* key =
-      descriptor->message_type()->FindFieldByName("key");
+      descriptor->message_type()->map_key();
   const FieldDescriptor* val =
-      descriptor->message_type()->FindFieldByName("value");
+      descriptor->message_type()->map_value();
   (*variables)["key_cpp"] = PrimitiveTypeName(options, key->cpp_type());
   switch (val->cpp_type()) {
     case FieldDescriptor::CPPTYPE_MESSAGE:
@@ -207,9 +207,9 @@ void MapFieldGenerator::GenerateSerializeWithCachedSizesToArray(
   format("if (!this->_internal_$name$().empty()) {\n");
   format.Indent();
   const FieldDescriptor* key_field =
-      descriptor_->message_type()->FindFieldByName("key");
+      descriptor_->message_type()->map_key();
   const FieldDescriptor* value_field =
-      descriptor_->message_type()->FindFieldByName("value");
+      descriptor_->message_type()->map_value();
   const bool string_key = key_field->type() == FieldDescriptor::TYPE_STRING;
   const bool string_value = value_field->type() == FieldDescriptor::TYPE_STRING;
 

src/google/protobuf/compiler/cpp/cpp_message.cc

@@ -276,8 +276,8 @@ void CollectMapInfo(const Options& options, const Descriptor* descriptor,
                     std::map<std::string, std::string>* variables) {
   GOOGLE_CHECK(IsMapEntryMessage(descriptor));
   std::map<std::string, std::string>& vars = *variables;
-  const FieldDescriptor* key = descriptor->FindFieldByName("key");
+  const FieldDescriptor* key = descriptor->map_key();
-  const FieldDescriptor* val = descriptor->FindFieldByName("value");
+  const FieldDescriptor* val = descriptor->map_value();
   vars["key_cpp"] = PrimitiveTypeName(options, key->cpp_type());
   switch (val->cpp_type()) {
     case FieldDescriptor::CPPTYPE_MESSAGE:

src/google/protobuf/compiler/cpp/cpp_parse_function_generator.cc

@@ -752,7 +752,7 @@ void ParseFunctionGenerator::GenerateLengthDelim(Formatter& format,
       case FieldDescriptor::TYPE_MESSAGE: {
         if (field->is_map()) {
           const FieldDescriptor* val =
-              field->message_type()->FindFieldByName("value");
+              field->message_type()->map_value();
           GOOGLE_CHECK(val);
           if (val->type() == FieldDescriptor::TYPE_ENUM &&
               !HasPreservingUnknownEnumSemantics(field)) {

src/google/protobuf/compiler/csharp/csharp_map_field.cc

@@ -57,9 +57,9 @@ MapFieldGenerator::~MapFieldGenerator() {
 
 void MapFieldGenerator::GenerateMembers(io::Printer* printer) {
   const FieldDescriptor* key_descriptor =
-      descriptor_->message_type()->FindFieldByName("key");
+      descriptor_->message_type()->map_key();
   const FieldDescriptor* value_descriptor =
-      descriptor_->message_type()->FindFieldByName("value");
+      descriptor_->message_type()->map_value();
   variables_["key_type_name"] = type_name(key_descriptor);
   variables_["value_type_name"] = type_name(value_descriptor);
   std::unique_ptr<FieldGeneratorBase> key_generator(

src/google/protobuf/compiler/java/java_helpers.cc

@@ -1050,7 +1050,7 @@ int GetExperimentalJavaFieldType(const FieldDescriptor* field) {
   if (field->is_map()) {
     if (!SupportUnknownEnumValue(field)) {
       const FieldDescriptor* value =
-          field->message_type()->FindFieldByName("value");
+          field->message_type()->map_value();
       if (GetJavaType(value) == JAVATYPE_ENUM) {
         extra_bits |= kMapWithProto2EnumValue;
       }

src/google/protobuf/compiler/java/java_map_field.cc

@@ -47,14 +47,14 @@ const FieldDescriptor* KeyField(const FieldDescriptor* descriptor) {
   GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, descriptor->type());
   const Descriptor* message = descriptor->message_type();
   GOOGLE_CHECK(message->options().map_entry());
-  return message->FindFieldByName("key");
+  return message->map_key();
 }
 
 const FieldDescriptor* ValueField(const FieldDescriptor* descriptor) {
   GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, descriptor->type());
   const Descriptor* message = descriptor->message_type();
   GOOGLE_CHECK(message->options().map_entry());
-  return message->FindFieldByName("value");
+  return message->map_value();
 }
 
 std::string TypeName(const FieldDescriptor* field,

src/google/protobuf/compiler/java/java_map_field_lite.cc

@@ -49,14 +49,14 @@ const FieldDescriptor* KeyField(const FieldDescriptor* descriptor) {
   GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, descriptor->type());
   const Descriptor* message = descriptor->message_type();
   GOOGLE_CHECK(message->options().map_entry());
-  return message->FindFieldByName("key");
+  return message->map_key();
 }
 
 const FieldDescriptor* ValueField(const FieldDescriptor* descriptor) {
   GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, descriptor->type());
   const Descriptor* message = descriptor->message_type();
   GOOGLE_CHECK(message->options().map_entry());
-  return message->FindFieldByName("value");
+  return message->map_value();
 }
 
 std::string TypeName(const FieldDescriptor* field,

src/google/protobuf/compiler/java/java_message.cc

@@ -67,7 +67,7 @@ using internal::WireFormatLite;
 namespace {
 std::string MapValueImmutableClassdName(const Descriptor* descriptor,
                                         ClassNameResolver* name_resolver) {
-  const FieldDescriptor* value_field = descriptor->FindFieldByName("value");
+  const FieldDescriptor* value_field = descriptor->map_value();
   GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, value_field->type());
   return name_resolver->GetImmutableClassName(value_field->message_type());
 }

src/google/protobuf/compiler/java/java_message_builder.cc

@@ -61,7 +61,7 @@ namespace java {
 namespace {
 std::string MapValueImmutableClassdName(const Descriptor* descriptor,
                                         ClassNameResolver* name_resolver) {
-  const FieldDescriptor* value_field = descriptor->FindFieldByName("value");
+  const FieldDescriptor* value_field = descriptor->map_value();
   GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, value_field->type());
   return name_resolver->GetImmutableClassName(value_field->message_type());
 }

src/google/protobuf/compiler/objectivec/objectivec_map_field.cc

@@ -153,7 +153,7 @@ void MapFieldGenerator::FinishInitialization(void) {
   // Use the array_comment support in RepeatedFieldGenerator to output what the
   // values in the map are.
   const FieldDescriptor* value_descriptor =
-      descriptor_->message_type()->FindFieldByName("value");
+      descriptor_->message_type()->map_value();
   if (GetObjectiveCType(value_descriptor) == OBJECTIVECTYPE_ENUM) {
     variables_["array_comment"] =
         "// |" + variables_["name"] + "| values are |" + value_field_generator_->variable("storage_type") + "|\n";
@@ -164,7 +164,7 @@ void MapFieldGenerator::DetermineForwardDeclarations(
     std::set<std::string>* fwd_decls) const {
   RepeatedFieldGenerator::DetermineForwardDeclarations(fwd_decls);
   const FieldDescriptor* value_descriptor =
-      descriptor_->message_type()->FindFieldByName("value");
+      descriptor_->message_type()->map_value();
   if (GetObjectiveCType(value_descriptor) == OBJECTIVECTYPE_MESSAGE) {
     const std::string& value_storage_type =
         value_field_generator_->variable("storage_type");
@@ -176,7 +176,7 @@ void MapFieldGenerator::DetermineObjectiveCClassDefinitions(
     std::set<std::string>* fwd_decls) const {
   // Class name is already in "storage_type".
   const FieldDescriptor* value_descriptor =
-      descriptor_->message_type()->FindFieldByName("value");
+      descriptor_->message_type()->map_value();
   if (GetObjectiveCType(value_descriptor) == OBJECTIVECTYPE_MESSAGE) {
     fwd_decls->insert(ObjCClassDeclaration(
         value_field_generator_->variable("storage_type")));

src/google/protobuf/compiler/php/php_generator.cc

@@ -741,8 +741,8 @@ void GenerateFieldAccessor(const FieldDescriptor* field, const Options& options,
   // Type check.
   if (field->is_map()) {
     const Descriptor* map_entry = field->message_type();
-    const FieldDescriptor* key = map_entry->FindFieldByName("key");
+    const FieldDescriptor* key = map_entry->map_key();
-    const FieldDescriptor* value = map_entry->FindFieldByName("value");
+    const FieldDescriptor* value = map_entry->map_value();
     printer->Print(
         "$arr = GPBUtil::checkMapField($var, "
         "\\Google\\Protobuf\\Internal\\GPBType::^key_type^, "
@@ -889,9 +889,9 @@ void GenerateMessageToPool(const std::string& name_prefix,
     const FieldDescriptor* field = message->field(i);
     if (field->is_map()) {
       const FieldDescriptor* key =
-          field->message_type()->FindFieldByName("key");
+          field->message_type()->map_key();
       const FieldDescriptor* val =
-          field->message_type()->FindFieldByName("value");
+          field->message_type()->map_value();
       printer->Print(
           "->map('^field^', \\Google\\Protobuf\\Internal\\GPBType::^key^, "
           "\\Google\\Protobuf\\Internal\\GPBType::^value^, ^number^^other^)\n",

src/google/protobuf/generated_message_reflection.cc

@@ -2325,7 +2325,7 @@ bool Reflection::InsertOrLookupMapValue(Message* message,
                                         MapValueRef* val) const {
   USAGE_CHECK(IsMapFieldInApi(field), "InsertOrLookupMapValue",
               "Field is not a map field.");
-  val->SetType(field->message_type()->FindFieldByName("value")->cpp_type());
+  val->SetType(field->message_type()->map_value()->cpp_type());
   return MutableRaw<MapFieldBase>(message, field)
       ->InsertOrLookupMapValue(key, val);
 }
@@ -2335,7 +2335,7 @@ bool Reflection::LookupMapValue(const Message& message,
                                 MapValueConstRef* val) const {
   USAGE_CHECK(IsMapFieldInApi(field), "LookupMapValue",
               "Field is not a map field.");
-  val->SetType(field->message_type()->FindFieldByName("value")->cpp_type());
+  val->SetType(field->message_type()->map_value()->cpp_type());
   return GetRaw<MapFieldBase>(message, field).LookupMapValue(key, val);
 }
 

src/google/protobuf/map_field.h

@@ -855,8 +855,8 @@ class PROTOBUF_EXPORT MapIterator {
   MapIterator(Message* message, const FieldDescriptor* field) {
     const Reflection* reflection = message->GetReflection();
     map_ = reflection->MutableMapData(message, field);
-    key_.SetType(field->message_type()->FindFieldByName("key")->cpp_type());
+    key_.SetType(field->message_type()->map_key()->cpp_type());
-    value_.SetType(field->message_type()->FindFieldByName("value")->cpp_type());
+    value_.SetType(field->message_type()->map_value()->cpp_type());
     map_->InitializeIterator(this);
   }
   MapIterator(const MapIterator& other) {

src/google/protobuf/map_test.inc

@@ -1259,21 +1259,21 @@ TEST_F(MapFieldReflectionTest, RegularFields) {
       desc->FindFieldByName("map_int32_foreign_message");
 
   const FieldDescriptor* fd_map_int32_in32_key =
-      fd_map_int32_int32->message_type()->FindFieldByName("key");
+      fd_map_int32_int32->message_type()->map_key();
   const FieldDescriptor* fd_map_int32_in32_value =
-      fd_map_int32_int32->message_type()->FindFieldByName("value");
+      fd_map_int32_int32->message_type()->map_value();
   const FieldDescriptor* fd_map_int32_double_key =
-      fd_map_int32_double->message_type()->FindFieldByName("key");
+      fd_map_int32_double->message_type()->map_key();
   const FieldDescriptor* fd_map_int32_double_value =
-      fd_map_int32_double->message_type()->FindFieldByName("value");
+      fd_map_int32_double->message_type()->map_value();
   const FieldDescriptor* fd_map_string_string_key =
-      fd_map_string_string->message_type()->FindFieldByName("key");
+      fd_map_string_string->message_type()->map_key();
   const FieldDescriptor* fd_map_string_string_value =
-      fd_map_string_string->message_type()->FindFieldByName("value");
+      fd_map_string_string->message_type()->map_value();
   const FieldDescriptor* fd_map_int32_foreign_message_key =
-      fd_map_int32_foreign_message->message_type()->FindFieldByName("key");
+      fd_map_int32_foreign_message->message_type()->map_key();
   const FieldDescriptor* fd_map_int32_foreign_message_value =
-      fd_map_int32_foreign_message->message_type()->FindFieldByName("value");
+      fd_map_int32_foreign_message->message_type()->map_value();
 
   // Get RepeatedPtrField objects for all fields of interest.
   const RepeatedPtrField<Message>& mf_int32_int32 =
@@ -1446,21 +1446,21 @@ TEST_F(MapFieldReflectionTest, RepeatedFieldRefForRegularFields) {
       desc->FindFieldByName("map_int32_foreign_message");
 
   const FieldDescriptor* fd_map_int32_in32_key =
-      fd_map_int32_int32->message_type()->FindFieldByName("key");
+      fd_map_int32_int32->message_type()->map_key();
   const FieldDescriptor* fd_map_int32_in32_value =
-      fd_map_int32_int32->message_type()->FindFieldByName("value");
+      fd_map_int32_int32->message_type()->map_value();
   const FieldDescriptor* fd_map_int32_double_key =
-      fd_map_int32_double->message_type()->FindFieldByName("key");
+      fd_map_int32_double->message_type()->map_key();
   const FieldDescriptor* fd_map_int32_double_value =
-      fd_map_int32_double->message_type()->FindFieldByName("value");
+      fd_map_int32_double->message_type()->map_value();
   const FieldDescriptor* fd_map_string_string_key =
-      fd_map_string_string->message_type()->FindFieldByName("key");
+      fd_map_string_string->message_type()->map_key();
   const FieldDescriptor* fd_map_string_string_value =
-      fd_map_string_string->message_type()->FindFieldByName("value");
+      fd_map_string_string->message_type()->map_value();
   const FieldDescriptor* fd_map_int32_foreign_message_key =
-      fd_map_int32_foreign_message->message_type()->FindFieldByName("key");
+      fd_map_int32_foreign_message->message_type()->map_key();
   const FieldDescriptor* fd_map_int32_foreign_message_value =
-      fd_map_int32_foreign_message->message_type()->FindFieldByName("value");
+      fd_map_int32_foreign_message->message_type()->map_value();
 
   // Get RepeatedFieldRef objects for all fields of interest.
   const RepeatedFieldRef<Message> mf_int32_int32 =
@@ -2038,7 +2038,7 @@ TEST_F(MapFieldReflectionTest, MapSizeWithDuplicatedKey) {
 
     const Reflection* entry_reflection = entry1->GetReflection();
     const FieldDescriptor* key_field =
-        entry1->GetDescriptor()->FindFieldByName("key");
+        entry1->GetDescriptor()->map_key();
     entry_reflection->SetInt32(entry1, key_field, 1);
     entry_reflection->SetInt32(entry2, key_field, 1);
 
@@ -2059,7 +2059,7 @@ TEST_F(MapFieldReflectionTest, MapSizeWithDuplicatedKey) {
 
     const Reflection* entry_reflection = entry1->GetReflection();
     const FieldDescriptor* key_field =
-        entry1->GetDescriptor()->FindFieldByName("key");
+        entry1->GetDescriptor()->map_key();
     entry_reflection->SetInt32(entry1, key_field, 1);
     entry_reflection->SetInt32(entry2, key_field, 1);
 
@@ -2951,7 +2951,7 @@ TEST(GeneratedMapFieldReflectionTest, EmbedProto2Message) {
       UNITTEST::TestMessageMap::descriptor()->FindFieldByName(
           "map_int32_message");
   const FieldDescriptor* value =
-      map_field->message_type()->FindFieldByName("value");
+      map_field->message_type()->map_value();
 
   Message* entry_message =
       message.GetReflection()->AddMessage(&message, map_field);
@@ -2971,9 +2971,9 @@ TEST(GeneratedMapFieldReflectionTest, MergeFromClearMapEntry) {
   const FieldDescriptor* map_field =
       UNITTEST::TestMap::descriptor()->FindFieldByName("map_int32_int32");
   const FieldDescriptor* key =
-      map_field->message_type()->FindFieldByName("key");
+      map_field->message_type()->map_key();
   const FieldDescriptor* value =
-      map_field->message_type()->FindFieldByName("value");
+      map_field->message_type()->map_value();
 
   Message* entry_message1 =
       message.GetReflection()->AddMessage(&message, map_field);
@@ -3005,7 +3005,7 @@ TEST(GeneratedMapFieldReflectionTest, Proto2MapEntryClear) {
   const FieldDescriptor* field_descriptor =
       descriptor->FindFieldByName("known_map_field");
   const FieldDescriptor* value_descriptor =
-      field_descriptor->message_type()->FindFieldByName("value");
+      field_descriptor->message_type()->map_value();
   Message* sub_message =
       message.GetReflection()->AddMessage(&message, field_descriptor);
   EXPECT_EQ(0, sub_message->GetReflection()->GetEnumValue(*sub_message,
@@ -3133,7 +3133,7 @@ TEST_F(MapFieldInDynamicMessageTest, MapEntryReferernceValidAfterSerialize) {
       message.get(), "map_int32_foreign_message", 0);
   const Reflection* map_entry_reflection = map_entry->GetReflection();
   const Descriptor* map_entry_desc = map_entry->GetDescriptor();
-  const FieldDescriptor* value_field = map_entry_desc->FindFieldByName("value");
+  const FieldDescriptor* value_field = map_entry_desc->map_value();
   Message* submsg =
       map_entry_reflection->MutableMessage(map_entry, value_field);
 
@@ -3696,7 +3696,7 @@ TEST(TextFormatMapTest, NoDisableReflectionIterator) {
   // Modify map via the iterator (invalidated in previous implementation.).
   const Reflection* map_entry_reflection = iter->GetReflection();
   const FieldDescriptor* value_field_desc =
-      iter->GetDescriptor()->FindFieldByName("value");
+      iter->GetDescriptor()->map_value();
   map_entry_reflection->SetInt32(&(*iter), value_field_desc, 2);
   GOOGLE_LOG(INFO) << iter->DebugString();
 

src/google/protobuf/util/message_differencer_unittest.cc

@@ -3408,7 +3408,7 @@ class LengthMapKeyComparator
     const Reflection* reflection1 = message1.GetReflection();
     const Reflection* reflection2 = message2.GetReflection();
     const FieldDescriptor* key_field =
-        message1.GetDescriptor()->FindFieldByName("key");
+        message1.GetDescriptor()->map_key();
     return reflection1->GetString(message1, key_field).size() ==
            reflection2->GetString(message2, key_field).size();
   }