From 9852998440dcaa3eec11377553e996ff9852bb4e Mon Sep 17 00:00:00 2001
From: pechatnov <pechatnov@yandex-team.com>
Date: Thu, 26 Mar 2026 10:11:59 +0300
Subject: Add suggestions on enum parse error
 commit_hash:3b7f35f613737aa92f473877e8b24782f7dfcd2a

---
 library/cpp/yt/string/enum-inl.h            | 26 +++++++++++++++++--
 library/cpp/yt/string/enum.cpp              | 40 ++++++++++++++++++++++++++---
 library/cpp/yt/string/enum.h                |  3 +++
 library/cpp/yt/string/unittests/enum_ut.cpp |  2 --
 4 files changed, 63 insertions(+), 8 deletions(-)

(limited to 'library/cpp')

diff --git a/library/cpp/yt/string/enum-inl.h b/library/cpp/yt/string/enum-inl.h
index 9f8ca893d2f..14d26c61158 100644
--- a/library/cpp/yt/string/enum-inl.h
+++ b/library/cpp/yt/string/enum-inl.h
@@ -13,16 +13,28 @@
 #include <util/string/printf.h>
 #include <util/string/strip.h>
 
+#include <span>
+
 namespace NYT {
 
 ////////////////////////////////////////////////////////////////////////////////
 
 namespace NDetail {
 
+////////////////////////////////////////////////////////////////////////////////
+
+using TEnumSuggestionsCalculator = std::string (*)(
+    TStringBuf value,
+    const std::span<const TStringBuf>& domainNames);
+
+extern "C" TEnumSuggestionsCalculator TryGetEnumSuggestionsCalculator();
+
 [[noreturn]]
 void ThrowMalformedEnumValueException(
     TStringBuf typeName,
-    TStringBuf value);
+    TStringBuf value,
+    const std::span<const TStringBuf>& domainNames = {});
+
 
 void FormatUnknownEnumValue(
     auto* builder,
@@ -32,8 +44,12 @@ void FormatUnknownEnumValue(
     builder->AppendFormat("%v::unknown-%v", name, ToUnderlying(value));
 }
 
+////////////////////////////////////////////////////////////////////////////////
+
 } // namespace NDetail
 
+////////////////////////////////////////////////////////////////////////////////
+
 template <class T>
 std::optional<T> TryParseEnum(TStringBuf str, bool enableUnknown)
 {
@@ -80,7 +96,13 @@ T ParseEnum(TStringBuf str)
     if (auto optionalResult = TryParseEnum<T>(str, /*enableUnkown*/ true)) {
         return *optionalResult;
     }
-    NYT::NDetail::ThrowMalformedEnumValueException(TEnumTraits<T>::GetTypeName(), str);
+
+    std::span<const TStringBuf> domainNames;
+    if constexpr (requires { TEnumTraits<T>::GetDomainNames(); }) {
+        domainNames = TEnumTraits<T>::GetDomainNames();
+    }
+
+    NYT::NDetail::ThrowMalformedEnumValueException(TEnumTraits<T>::GetTypeName(), str, domainNames);
 }
 
 template <class T>
diff --git a/library/cpp/yt/string/enum.cpp b/library/cpp/yt/string/enum.cpp
index 844254faa0f..beeba753daf 100644
--- a/library/cpp/yt/string/enum.cpp
+++ b/library/cpp/yt/string/enum.cpp
@@ -8,11 +8,39 @@ namespace NYT {
 
 namespace NDetail {
 
-void ThrowMalformedEnumValueException(TStringBuf typeName, TStringBuf value)
+////////////////////////////////////////////////////////////////////////////////
+
+#if defined(_MSC_VER)
+
+extern "C" TEnumSuggestionsCalculator TryGetEnumSuggestionsCalculatorWeak()
+{
+    return nullptr;
+}
+
+__pragma(comment(linker, "/alternatename:TryGetEnumSuggestionsCalculator=TryGetEnumSuggestionsCalculatorWeak"))
+
+#else
+
+extern "C" Y_WEAK TEnumSuggestionsCalculator TryGetEnumSuggestionsCalculator()
 {
-    throw TSimpleException(Format("Error parsing %v value %Qv",
-        typeName,
-        value));
+    return nullptr;
+}
+
+#endif
+
+////////////////////////////////////////////////////////////////////////////////
+
+void ThrowMalformedEnumValueException(
+    TStringBuf typeName,
+    TStringBuf value,
+    const std::span<const TStringBuf>& domainNames)
+{
+    auto errorMessage = Format("Error parsing %v value %Qv", typeName, value);
+    auto suggestionsCalculator = TryGetEnumSuggestionsCalculator();
+    if (!domainNames.empty() && suggestionsCalculator) {
+        errorMessage += Format("; closest possible values are %v", suggestionsCalculator(value, domainNames));
+    }
+    throw TSimpleException(errorMessage);
 }
 
 template <bool ThrowOnError>
@@ -32,8 +60,12 @@ std::optional<std::string> DecodeEnumValueImpl(TStringBuf value)
     return camelValue;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+
 } // namespace NDetail
 
+////////////////////////////////////////////////////////////////////////////////
+
 std::optional<std::string> TryDecodeEnumValue(TStringBuf value)
 {
     return NDetail::DecodeEnumValueImpl<false>(value);
diff --git a/library/cpp/yt/string/enum.h b/library/cpp/yt/string/enum.h
index de7d6a52fac..322485a560d 100644
--- a/library/cpp/yt/string/enum.h
+++ b/library/cpp/yt/string/enum.h
@@ -17,6 +17,9 @@ std::string EncodeEnumValue(TStringBuf value);
 template <class T>
 std::optional<T> TryParseEnum(TStringBuf str, bool enableUnknown = false);
 
+//! Parses an enum value from a string.
+//! Link against library/cpp/yt/string/enable_enum_suggestions_on_enum_parse_error
+//! to include suggestions in the exception message on parse failure.
 template <class T>
 T ParseEnum(TStringBuf str);
 
diff --git a/library/cpp/yt/string/unittests/enum_ut.cpp b/library/cpp/yt/string/unittests/enum_ut.cpp
index 39dbdfd2075..b262568565c 100644
--- a/library/cpp/yt/string/unittests/enum_ut.cpp
+++ b/library/cpp/yt/string/unittests/enum_ut.cpp
@@ -126,5 +126,3 @@ TEST(TParseEnumTest, ParseBitEnum)
 
 } // namespace
 } // namespace NYT
-
-
-- 
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