YT-22885: DEFINE_ENUM_UNKNOWN_VALUE, string-related conversions

commit_hash:14c7e42422af750383f04855b4a7ea6b267b92d2

3 files changed, 49 insertions, 15 deletions

diff --git a/library/cpp/yt/misc/enum-inl.h b/library/cpp/yt/misc/enum-inl.h
index 5e1d04da1f..6ad9273293 100644
--- a/library/cpp/yt/misc/enum-inl.h
+++ b/library/cpp/yt/misc/enum-inl.h
@@ -38,6 +38,14 @@ namespace NYT {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+template <class T>
+constexpr std::optional<T> TryGetEnumUnknownValueImpl(T)
+{
+    return std::nullopt;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 namespace NDetail {
 
 template <typename TValues>
@@ -262,6 +270,13 @@ TStringBuf TEnumTraits<T, true>::GetTypeName()
 }
 
 template <class T>
+constexpr std::optional<T> TEnumTraits<T, true>::TryGetUnknownValue()
+{
+    using NYT::TryGetEnumUnknownValueImpl;
+    return TryGetEnumUnknownValueImpl(T());
+}
+
+template <class T>
 std::optional<T> TEnumTraits<T, true>::FindValueByLiteral(TStringBuf literal)
 {
     return TEnumTraitsImpl<T>::FindValueByLiteral(literal);
diff --git a/library/cpp/yt/misc/enum.h b/library/cpp/yt/misc/enum.h
index 4d40ab8ec4..f78d23a06d 100644
--- a/library/cpp/yt/misc/enum.h
+++ b/library/cpp/yt/misc/enum.h
@@ -33,18 +33,11 @@ template <class T>
 using TEnumTraitsImpl = decltype(GetEnumTraitsImpl(T()));
 
 template <class T>
-constexpr bool IsEnumDomainSizeKnown()
-{
-    if constexpr(requires{ TEnumTraitsImpl<T>::DomainSize; }) {
-        return true;
-    } else {
-        return false;
-    }
-}
+constexpr std::optional<T> TryGetEnumUnknownValueImpl(T);
 
 template <
     class T,
-    bool = IsEnumDomainSizeKnown<T>()
+    bool DomainSizeKnown = requires{ TEnumTraitsImpl<T>::DomainSize; }
 >
 struct TEnumTraitsWithKnownDomain
 { };
@@ -62,7 +55,7 @@ struct TEnumTraits
 };
 
 template <class T>
-struct TEnumTraitsWithKnownDomain<T, true>
+struct TEnumTraitsWithKnownDomain<T, /*DomainSizeKnown*/ true>
 {
     static constexpr int GetDomainSize();
 
@@ -91,6 +84,7 @@ struct TEnumTraits<T, true>
 
     static TStringBuf GetTypeName();
 
+    static constexpr std::optional<T> TryGetUnknownValue();
     static std::optional<TStringBuf> FindLiteralByValue(T value);
     static std::optional<T> FindValueByLiteral(TStringBuf literal);
 
@@ -102,7 +96,7 @@ struct TEnumTraits<T, true>
 
 //! Defines a smart enumeration with a specific underlying type.
 /*!
- * \param enumType Enumeration enumType.
+ * \param enumType Enumeration type.
  * \param seq Enumeration domain encoded as a <em>sequence</em>.
  * \param underlyingType Underlying type.
  */
@@ -127,7 +121,7 @@ struct TEnumTraits<T, true>
 
 //! Defines a smart enumeration with a specific underlying type.
 /*!
- * \param enumType Enumeration enumType.
+ * \param enumType Enumeration type.
  * \param seq Enumeration domain encoded as a <em>sequence</em>.
  * \param underlyingType Underlying type.
  */
@@ -142,7 +136,7 @@ struct TEnumTraits<T, true>
 //! Defines a smart enumeration with a specific underlying type.
 //! Duplicate enumeration values are allowed.
 /*!
- * \param enumType Enumeration enumType.
+ * \param enumType Enumeration type.
  * \param seq Enumeration domain encoded as a <em>sequence</em>.
  * \param underlyingType Underlying type.
  */
@@ -155,7 +149,7 @@ struct TEnumTraits<T, true>
 
 //! Defines a smart enumeration with the default |unsigned int| underlying type.
 /*!
- * \param enumType Enumeration enumType.
+ * \param enumType Enumeration type.
  * \param seq Enumeration domain encoded as a <em>sequence</em>.
  */
 #define DEFINE_BIT_ENUM(enumType, seq) \
@@ -163,7 +157,7 @@ struct TEnumTraits<T, true>
 
 //! Defines a smart enumeration with a specific underlying type and IsStringSerializable attribute.
 /*!
- * \param enumType Enumeration enumType.
+ * \param enumType Enumeration type.
  * \param seq Enumeration domain encoded as a <em>sequence</em>.
  * \param underlyingType Underlying type.
  */
@@ -186,6 +180,18 @@ struct TEnumTraits<T, true>
 #define DEFINE_STRING_SERIALIZABLE_ENUM(enumType, seq) \
     DEFINE_STRING_SERIALIZABLE_ENUM_WITH_UNDERLYING_TYPE(enumType, int, seq)
 
+//! When enum from another representation (e.g. string or protobuf integer),
+//! instructs the parser to treat undeclared values as |unknownValue|.
+/*!
+ * \param enumType Enumeration type.
+ * \param unknownValue A sentinel value of #enumType.
+ */
+#define DEFINE_ENUM_UNKNOWN_VALUE(enumType, unknownValue) \
+    [[maybe_unused]] constexpr std::optional<enumType> TryGetEnumUnknownValueImpl(enumType) \
+    { \
+        return enumType::unknownValue; \
+    }
+
 ////////////////////////////////////////////////////////////////////////////////
 
 //! Returns |true| iff the enumeration value is not bitwise zero.
diff --git a/library/cpp/yt/misc/unittests/enum_ut.cpp b/library/cpp/yt/misc/unittests/enum_ut.cpp
index 63b8666ae1..938ab11581 100644
--- a/library/cpp/yt/misc/unittests/enum_ut.cpp
+++ b/library/cpp/yt/misc/unittests/enum_ut.cpp
@@ -50,6 +50,13 @@ DEFINE_ENUM_WITH_UNDERLYING_TYPE(ECardinal, char,
     ((South) (3))
 );
 
+DEFINE_ENUM(EWithUnknown,
+    (First)
+    (Second)
+    (Unknown)
+);
+DEFINE_ENUM_UNKNOWN_VALUE(EWithUnknown, Unknown);
+
 ////////////////////////////////////////////////////////////////////////////////
 
 template <class T, size_t N>
@@ -280,6 +287,12 @@ TEST(TEnumTest, Cast)
     }
 }
 
+TEST(TEnumTest, UnknownValue)
+{
+    EXPECT_EQ(TEnumTraits<EColor>::TryGetUnknownValue(), std::nullopt);
+    EXPECT_EQ(TEnumTraits<EWithUnknown>::TryGetUnknownValue(), EWithUnknown::Unknown);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 } // namespace