YT-21306: Add EnumHasDefaultValue

d9b67f1778da2d15dd94f7285afe4e3490a233ab

3 files changed, 23 insertions, 0 deletions

diff --git a/library/cpp/yt/misc/cast-inl.h b/library/cpp/yt/misc/cast-inl.h
index a694394f88..795682864f 100644
--- a/library/cpp/yt/misc/cast-inl.h
+++ b/library/cpp/yt/misc/cast-inl.h
@@ -124,6 +124,10 @@ T CheckedEnumCast(S value)
 {
     T result;
     if (!TryEnumCast<T>(value, &result)) {
+        if constexpr (TEnumHasDefaultValue<T>::value) {
+            return GetDefaultValue(T{});
+        }
+
         throw TSimpleException(Sprintf("Error casting %s value \"%d\" to enum %s",
             TypeName<S>().c_str(),
             static_cast<int>(value),
diff --git a/library/cpp/yt/misc/enum.h b/library/cpp/yt/misc/enum.h
index 954b63cbc0..11e168948f 100644
--- a/library/cpp/yt/misc/enum.h
+++ b/library/cpp/yt/misc/enum.h
@@ -197,6 +197,20 @@ constexpr bool None(E value) noexcept;
 
 ////////////////////////////////////////////////////////////////////////////////
 
+template <typename E, typename = void>
+    requires TEnumTraits<E>::IsEnum
+struct TEnumHasDefaultValue
+    : std::false_type
+{ };
+
+template <typename E>
+    requires TEnumTraits<E>::IsEnum
+struct TEnumHasDefaultValue<E, std::void_t<decltype(GetDefaultValue(std::declval<E>()))>>
+    : std::is_same<decltype(GetDefaultValue(std::declval<E>())), E>
+{ };
+
+////////////////////////////////////////////////////////////////////////////////
+
 } // namespace NYT
 
 #define ENUM_INL_H_
diff --git a/library/cpp/yt/string/enum-inl.h b/library/cpp/yt/string/enum-inl.h
index 41f7197d15..19ba1f7fe5 100644
--- a/library/cpp/yt/string/enum-inl.h
+++ b/library/cpp/yt/string/enum-inl.h
@@ -87,6 +87,11 @@ T ParseEnum(TStringBuf value)
     if (auto optionalResult = TryParseEnum<T>(value)) {
         return *optionalResult;
     }
+
+    if constexpr (TEnumHasDefaultValue<T>::value) {
+        return GetDefaultValue(T{});
+    }
+
     NYT::NDetail::ThrowMalformedEnumValueException(TEnumTraits<T>::GetTypeName(), value);
 }