Forbid new required fields in config

ydb/core/config/ut/ya.make

@@ -0,0 +1,12 @@
+UNITTEST()
+
+SRCS(
+    main.cpp
+)
+
+PEERDIR(
+    ydb/core/config/utils
+    library/cpp/testing/unittest
+)
+
+END()

ydb/core/config/utils/config_traverse.cpp

@@ -0,0 +1,57 @@
+#include "config_traverse.h"
+
+#include <util/system/compiler.h>
+#include <util/generic/deque.h>
+#include <util/generic/vector.h>
+#include <util/generic/string.h>
+#include <util/generic/map.h>
+#include <util/generic/set.h>
+
+#include <ydb/core/protos/config.pb.h>
+
+namespace NKikimr::NConfig {
+
+ssize_t FindLoop(TDeque<const Descriptor*>& typePath, const Descriptor* child) {
+    for (ssize_t i = 0; i < (ssize_t)typePath.size(); ++i) {
+        if (typePath[i] == child) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+void Traverse(const Descriptor* d, TDeque<const Descriptor*>& typePath, TDeque<const FieldDescriptor*>& fieldPath, const FieldDescriptor* field, TOnEntryFn onEntry) {
+    ssize_t loop = FindLoop(typePath, d);
+
+    Y_ABORT_IF(!d && !field, "Either field or descriptor must be defined");
+
+    onEntry(d, typePath, fieldPath, field, loop);
+
+    if (!d || loop != -1) {
+        return;
+    }
+
+    typePath.push_back(d);
+
+    for (int i = 0; i < d->field_count(); ++i) {
+        const FieldDescriptor* fieldDescriptor = d->field(i);
+        fieldPath.push_back(fieldDescriptor);
+        Traverse(fieldDescriptor->message_type(), typePath, fieldPath, fieldDescriptor, onEntry);
+        fieldPath.pop_back();
+    }
+
+    typePath.pop_back();
+}
+
+void Traverse(TOnEntryFn onEntry) {
+    auto& inst = NKikimrConfig::TAppConfig::default_instance();
+    const Descriptor* descriptor = inst.GetDescriptor();
+
+    TDeque<const Descriptor*> typePath;
+    TDeque<const FieldDescriptor*> fieldPath;
+    fieldPath.push_back(nullptr);
+    Traverse(descriptor, typePath, fieldPath, nullptr, onEntry);
+    fieldPath.pop_back();
+}
+
+} // namespace NKikimr::NConfig

ydb/core/config/utils/config_traverse.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <contrib/libs/protobuf/src/google/protobuf/descriptor.h>
+
+#include <util/generic/deque.h>
+
+#include <functional>
+
+namespace NKikimr::NConfig {
+
+using namespace NProtoBuf;
+
+using TOnEntryFn = std::function<void(const Descriptor*, const TDeque<const Descriptor*>&, const TDeque<const FieldDescriptor*>&, const FieldDescriptor*, ssize_t)>;
+
+void Traverse(TOnEntryFn onEntry);
+
+} // namespace NKikimr::NConfig

ydb/core/config/utils/ya.make

@@ -0,0 +1,12 @@
+LIBRARY()
+
+SRCS(
+    config_traverse.cpp
+)
+
+PEERDIR(
+    ydb/core/protos
+    library/cpp/protobuf/json
+)
+
+END()

ydb/core/config/ya.make

@@ -0,0 +1,4 @@
+RECURSE(
+    utils
+    ut
+)

ydb/core/ya.make

@@ -8,6 +8,7 @@ RECURSE(
     client
     cms
     control
+    config
     debug
     debug_tools
     discovery