From b9622c0ef0ac63a46404b2ead9c8ed2c804626ad Mon Sep 17 00:00:00 2001
From: Artyom Kolpakov <ddvamp007@gmail.com>
Date: Sat, 25 Apr 2026 01:26:09 +0000
Subject: [PATCH 1/2] fix universal: fix initialization of default values in
 FindOrDefault

---
 universal/include/userver/utils/algo.hpp |  6 ++++--
 universal/src/utils/algo_test.cpp        | 17 ++++++++++++++---
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/universal/include/userver/utils/algo.hpp b/universal/include/userver/utils/algo.hpp
index 032fa3a54ec0..f4ad4000da3e 100644
--- a/universal/include/userver/utils/algo.hpp
+++ b/universal/include/userver/utils/algo.hpp
@@ -57,7 +57,8 @@ auto* FindOrNullptr(Container& container, const Key& key) {
 template <typename Container, typename Key, typename Default>
 auto FindOrDefault(Container& container, const Key& key, Default&& def) {
     const auto* ptr = USERVER_NAMESPACE::utils::FindOrNullptr(container, key);
-    return (ptr ? *ptr : decltype(*ptr){std::forward<Default>(def)});
+    using R = std::remove_cvref_t<decltype(*ptr)>;
+    return (ptr ? *ptr : R(std::forward<Default>(def)));
 }
 
 /// @brief Returns default value if no key in associative container, otherwise
@@ -65,7 +66,8 @@ auto FindOrDefault(Container& container, const Key& key, Default&& def) {
 template <typename Container, typename Key>
 auto FindOrDefault(Container& container, const Key& key) {
     const auto* ptr = USERVER_NAMESPACE::utils::FindOrNullptr(container, key);
-    return (ptr ? *ptr : decltype(*ptr){});
+    using R = std::remove_cvref_t<decltype(*ptr)>;
+    return (ptr ? *ptr : R());
 }
 
 /// @brief Returns std::nullopt if no key in associative container, otherwise
diff --git a/universal/src/utils/algo_test.cpp b/universal/src/utils/algo_test.cpp
index 28d1005e9d33..ee5aee3ed516 100644
--- a/universal/src/utils/algo_test.cpp
+++ b/universal/src/utils/algo_test.cpp
@@ -48,21 +48,26 @@ TEST(UtilsAlgo, FindOrNullptrSets) {
 
 TEST(UtilsAlgo, FindOrDefaultMaps) {
     constexpr int kFallback = 42;
+    constexpr int kDefault = int();
     std::map<std::string, int> m = {{"1", 2}};
     std::unordered_map<std::string, int> um = {{"1", 2}};
 
     EXPECT_EQ(utils::FindOrDefault(m, "2", kFallback), kFallback);
     EXPECT_EQ(utils::FindOrDefault(um, "2", kFallback), kFallback);
 
-    ASSERT_EQ(utils::FindOrDefault(m, "1", kFallback), 2);
-    ASSERT_EQ(utils::FindOrDefault(um, "1", kFallback), 2);
-
     EXPECT_EQ(utils::FindOrDefault(m, "1", kFallback), 2);
     EXPECT_EQ(utils::FindOrDefault(um, "1", kFallback), 2);
+
+    EXPECT_EQ(utils::FindOrDefault(m, "2"), kDefault);
+    EXPECT_EQ(utils::FindOrDefault(um, "2"), kDefault);
+
+    EXPECT_EQ(utils::FindOrDefault(m, "1"), 2);
+    EXPECT_EQ(utils::FindOrDefault(um, "1"), 2);
 }
 
 TEST(UtilsAlgo, FindOrDefaultSets) {
     constexpr int kFallback = 42;
+    constexpr int kDefault = int();
     std::set<int> s = {1};
     std::unordered_set<int> us = {1};
 
@@ -71,6 +76,12 @@ TEST(UtilsAlgo, FindOrDefaultSets) {
 
     EXPECT_EQ(utils::FindOrDefault(s, 1, kFallback), 1);
     EXPECT_EQ(utils::FindOrDefault(us, 1, kFallback), 1);
+
+    EXPECT_EQ(utils::FindOrDefault(s, 2), kDefault);
+    EXPECT_EQ(utils::FindOrDefault(us, 2), kDefault);
+
+    EXPECT_EQ(utils::FindOrDefault(s, 1), 1);
+    EXPECT_EQ(utils::FindOrDefault(us, 1), 1);
 }
 
 TEST(UtilsAlgo, FindOptionalMaps) {

From 14f9af8547f53e7708aabdc37e5e4ad906f52b43 Mon Sep 17 00:00:00 2001
From: Artyom Kolpakov <ddvamp007@gmail.com>
Date: Sun, 26 Apr 2026 12:08:50 +0000
Subject: [PATCH 2/2] fix universal: add more tests for FindOrDefault

---
 universal/src/utils/algo_test.cpp | 52 +++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/universal/src/utils/algo_test.cpp b/universal/src/utils/algo_test.cpp
index ee5aee3ed516..e0ac26976154 100644
--- a/universal/src/utils/algo_test.cpp
+++ b/universal/src/utils/algo_test.cpp
@@ -1,6 +1,8 @@
 #include <userver/utils/algo.hpp>
 
+#include <initializer_list>
 #include <map>
+#include <set>
 #include <string>
 #include <string_view>
 #include <unordered_map>
@@ -84,6 +86,56 @@ TEST(UtilsAlgo, FindOrDefaultSets) {
     EXPECT_EQ(utils::FindOrDefault(us, 1), 1);
 }
 
+TEST(UtilsAlgo, FindOrDefaultNoList) {
+    struct List {
+        int val = 0;
+
+        List() = default;
+        List(const List&) = default;
+        explicit List(int v) : val(v) {}
+        List(std::initializer_list<int>) : val(-1) {}
+
+        auto operator<=>(const List&) const = default;
+    };
+
+    constexpr int kFallback = 42;
+    constexpr int kDefault = List().val;
+
+    std::map<int, List> m;
+    std::set<List> s;
+
+    EXPECT_TRUE(m.empty());
+    EXPECT_EQ(utils::FindOrDefault(m, 0, kFallback).val, kFallback);
+    EXPECT_EQ(utils::FindOrDefault(m, 0).val, kDefault);
+
+    EXPECT_TRUE(s.empty());
+    EXPECT_EQ(utils::FindOrDefault(s, List(1), kFallback).val, kFallback);
+    EXPECT_EQ(utils::FindOrDefault(s, List(1)).val, kDefault);
+}
+
+TEST(UtilsAlgo, FindOrDefaultNoExtraCopies) {
+    struct NoCopies {
+        bool copy = false;
+
+        NoCopies() = default;
+        NoCopies(const NoCopies&) : copy(true) {}
+        NoCopies(NoCopies&& that) noexcept : copy(that.copy) {}
+
+        auto operator<=>(const NoCopies&) const = default;
+    };
+
+    std::map<int, NoCopies> m;
+    std::set<NoCopies> s;
+
+    EXPECT_TRUE(m.empty());
+    EXPECT_FALSE(utils::FindOrDefault(m, 0, NoCopies()).copy);
+    EXPECT_FALSE(utils::FindOrDefault(m, 0).copy);
+    
+    EXPECT_TRUE(s.empty());
+    EXPECT_FALSE(utils::FindOrDefault(s, NoCopies(), NoCopies()).copy);
+    EXPECT_FALSE(utils::FindOrDefault(s, NoCopies()).copy);
+}
+
 TEST(UtilsAlgo, FindOptionalMaps) {
     std::map<std::string, int> m = {{"1", 2}};
     std::unordered_map<std::string, int> um = {{"1", 2}};