YT-18920: Add `TryDecodeEnumValue()`

3 files changed, 49 insertions, 23 deletions

diff --git a/library/cpp/yt/string/enum-inl.h b/library/cpp/yt/string/enum-inl.h
index 2fa138f52f..205ececae3 100644
--- a/library/cpp/yt/string/enum-inl.h
+++ b/library/cpp/yt/string/enum-inl.h
@@ -4,6 +4,8 @@
 #include "enum.h"
 #endif
 
+#include "format.h"
+
 #include <library/cpp/yt/exception/exception.h>
 
 #include <util/string/printf.h>
@@ -30,29 +32,35 @@ template <class T>
 std::optional<T> TryParseEnum(TStringBuf value)
 {
     auto tryFromString = [] (TStringBuf value) -> std::optional<T> {
-        try {
-            return TEnumTraits<T>::FindValueByLiteral(DecodeEnumValue(value));
-        } catch (const TSimpleException&) {
-            TStringBuf typeName;
-            auto isTypeNameCorrect = value.NextTok('(', typeName) && typeName == TEnumTraits<T>::GetTypeName();
-            if (!isTypeNameCorrect) {
-                throw;
-            }
+        if (auto decodedValue = TryDecodeEnumValue(value)) {
+            return TEnumTraits<T>::FindValueByLiteral(*decodedValue);
+        }
 
-            TStringBuf enumValue;
-            std::underlying_type_t<T> underlyingValue;
-            auto isEnumValueCorrect = value.NextTok(')', enumValue) && TryFromString(enumValue, underlyingValue);
-            if (!isEnumValueCorrect) {
-                throw;
-            }
+        auto reportError = [value] () {
+            throw TSimpleException(Format("Enum value %Qv is neither in a proper underscore case nor in a format \"%v(123)\"",
+                value,
+                TEnumTraits<T>::GetTypeName()));
+        };
 
-            auto isParsingComplete = value.empty();
-            if (!isParsingComplete) {
-                throw;
-            }
+        TStringBuf typeName;
+        auto isTypeNameCorrect = value.NextTok('(', typeName) && typeName == TEnumTraits<T>::GetTypeName();
+        if (!isTypeNameCorrect) {
+            reportError();
+        }
+
+        TStringBuf enumValue;
+        std::underlying_type_t<T> underlyingValue = 0;
+        auto isEnumValueCorrect = value.NextTok(')', enumValue) && TryFromString(enumValue, underlyingValue);
+        if (!isEnumValueCorrect) {
+            reportError();
+        }
 
-            return static_cast<T>(underlyingValue);
+        auto isParsingComplete = value.empty();
+        if (!isParsingComplete) {
+            reportError();
         }
+
+        return static_cast<T>(underlyingValue);
     };
 
     if constexpr (TEnumTraits<T>::IsBitEnum) {
diff --git a/library/cpp/yt/string/enum.cpp b/library/cpp/yt/string/enum.cpp
index 7cb8e5c6b6..e61b813fd2 100644
--- a/library/cpp/yt/string/enum.cpp
+++ b/library/cpp/yt/string/enum.cpp
@@ -6,18 +6,35 @@ namespace NYT {
 
 ////////////////////////////////////////////////////////////////////////////////
 
-TString DecodeEnumValue(TStringBuf value)
+template <bool failOnError>
+std::optional<TString> DecodeEnumValueImpl(TStringBuf value)
 {
     auto camelValue = UnderscoreCaseToCamelCase(value);
     auto underscoreValue = CamelCaseToUnderscoreCase(camelValue);
     if (value != underscoreValue) {
-        throw TSimpleException(Format("Enum value %Qv is not in a proper underscore case; did you mean %Qv?",
-            value,
-            underscoreValue));
+        if constexpr (failOnError) {
+            throw TSimpleException(Format("Enum value %Qv is not in a proper underscore case; did you mean %Qv?",
+                value,
+                underscoreValue));
+        } else {
+            return std::nullopt;
+        }
     }
     return camelValue;
 }
 
+std::optional<TString> TryDecodeEnumValue(TStringBuf value)
+{
+    return DecodeEnumValueImpl<false>(value);
+}
+
+TString DecodeEnumValue(TStringBuf value)
+{
+    auto decodedValue = DecodeEnumValueImpl<true>(value);
+    YT_VERIFY(decodedValue);
+    return *decodedValue;
+}
+
 TString EncodeEnumValue(TStringBuf value)
 {
     return CamelCaseToUnderscoreCase(value);
diff --git a/library/cpp/yt/string/enum.h b/library/cpp/yt/string/enum.h
index caad6f2064..b4b8d59171 100644
--- a/library/cpp/yt/string/enum.h
+++ b/library/cpp/yt/string/enum.h
@@ -10,6 +10,7 @@ namespace NYT {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+std::optional<TString> TryDecodeEnumValue(TStringBuf value);
 TString DecodeEnumValue(TStringBuf value);
 TString EncodeEnumValue(TStringBuf value);