feat(error_handling): Add Result<T, E> alias and macros to enable ergonomic Rust-style error handling.

src/ystdlib/error_handling/CMakeLists.txt

@@ -3,9 +3,13 @@ cpp_library(
     NAMESPACE ystdlib
     PUBLIC_HEADERS
         ErrorCode.hpp
+        Result.hpp
+    PUBLIC_LINK_LIBRARIES
+        outcome::hl
     TESTS_SOURCES
         test/constants.hpp
         test/test_ErrorCode.cpp
+        test/test_Result.cpp
         test/types.cpp
         test/types.hpp
 )

src/ystdlib/error_handling/Result.hpp

@@ -0,0 +1,50 @@
+#ifndef YSTDLIB_ERROR_HANDLING_RESULT_HPP
+#define YSTDLIB_ERROR_HANDLING_RESULT_HPP
+
+#include <system_error>
+
+#include <outcome/config.hpp>
+#include <outcome/std_result.hpp>
+#include <outcome/success_failure.hpp>
+
+namespace ystdlib::error_handling {
+template <typename ReturnType, typename ErrorType = std::error_code>
+using Result = OUTCOME_V2_NAMESPACE::std_result<ReturnType, ErrorType>;
+
+/**
+ * Default return value for ystdlib::error_handling::Result<void> when function succeeds.
+ */
+[[nodiscard]] inline auto success() -> OUTCOME_V2_NAMESPACE::success_type<void> {
+    return OUTCOME_V2_NAMESPACE::success();
+}
+
+// NOLINTBEGIN(bugprone-macro-parentheses, cppcoreguidelines-macro-usage)
+/**
+ * This macro works the same way as Rust's `?` operator for error propagation.
+ */
+#define YSTDLIB_TRY(expr) \
+    ({ \
+        auto result{(expr)}; \
+        if (result.has_error()) { \
+            return result.error(); \
+        } \
+        using ReturnType = decltype(result.value()); \
+        static_assert(std::is_move_constructible_v<ReturnType>); \
+        std::move(result.value()); \
+    })
+
+/**
+ * This macro works the same way as Rust's `?` operator for error propagation, without returning
+ * any value.
+ */
+#define YSTDLIB_ASSERT_NO_ERROR(expr) \
+    ({ \
+        if (auto const result{(expr)}; result.has_error()) { \
+            return result.error(); \
+        } \
+    })
+// NOLINTEND(bugprone-macro-parentheses, cppcoreguidelines-macro-usage)
+}  // namespace ystdlib::error_handling
+
+#endif  // YSTDLIB_ERROR_HANDLING_RESULT_HPP
+

src/ystdlib/error_handling/test/test_Result.cpp

@@ -0,0 +1,90 @@
+#include <system_error>
+#include <type_traits>
+
+#include <ystdlib/error_handling/Result.hpp>
+
+#include <catch2/catch_test_macros.hpp>
+
+#include "types.hpp"
+
+using ystdlib::error_handling::Result;
+using ystdlib::error_handling::success;
+using ystdlib::error_handling::test::BinaryErrorCode;
+using ystdlib::error_handling::test::BinaryErrorCodeEnum;
+
+namespace {
+constexpr int cTestInt{123};
+constexpr auto cVoidFunc = [](bool is_error) -> Result<void> {
+    if (is_error) {
+        return BinaryErrorCode{BinaryErrorCodeEnum::Failure};
+    }
+    return success();
+};
+constexpr auto cIntFunc = [](bool is_error) -> Result<int> {
+    if (is_error) {
+        return std::errc::bad_message;
+    }
+    return cTestInt;
+};
+}  // namespace
+
+namespace ystdlib::error_handling::test {
+TEST_CASE("test_result_void", "[error_handling][Result]") {
+    auto const result_no_error{cVoidFunc(false)};
+    REQUIRE_FALSE(result_no_error.has_error());
+    REQUIRE(std::is_void_v<decltype(result_no_error.value())>);
+
+    auto const result_has_error{cVoidFunc(true)};
+    REQUIRE(result_has_error.has_error());
+    REQUIRE(BinaryErrorCode{BinaryErrorCodeEnum::Failure} == result_has_error.error());
+}
+
+TEST_CASE("test_result_void_in_main", "[error_handling][Result]") {
+    auto main_func = [&](bool is_error) -> Result<void> {
+        YSTDLIB_ASSERT_NO_ERROR(cVoidFunc(is_error));
+        return success();
+    };
+    auto const main_no_error{main_func(false)};
+    REQUIRE_FALSE(main_no_error.has_error());
+    REQUIRE(std::is_void_v<decltype(main_no_error.value())>);
+
+    auto const main_has_error{main_func(true)};
+    REQUIRE(main_has_error.has_error());
+    REQUIRE((BinaryErrorCode{BinaryErrorCodeEnum::Failure} == main_has_error.error()));
+}
+
+TEST_CASE("test_result_int", "[error_handling][Result]") {
+    auto const result_no_error{cIntFunc(false)};
+    REQUIRE_FALSE(result_no_error.has_error());
+    REQUIRE((cTestInt == result_no_error.value()));
+
+    auto const result_has_error{cIntFunc(true)};
+    REQUIRE(result_has_error.has_error());
+    REQUIRE(std::errc::bad_message == result_has_error.error());
+}
+
+TEST_CASE("test_result_int_in_main", "[error_handling][Result]") {
+    auto main_func = [&](bool is_error) -> Result<void> {
+        YSTDLIB_ASSERT_NO_ERROR(cIntFunc(is_error));
+        return success();
+    };
+    auto const main_no_error{main_func(false)};
+    REQUIRE_FALSE(main_no_error.has_error());
+    REQUIRE(std::is_void_v<decltype(main_no_error.value())>);
+
+    auto const main_has_error{main_func(true)};
+    REQUIRE(main_has_error.has_error());
+    REQUIRE((std::errc::bad_message == main_has_error.error()));
+}
+
+TEST_CASE("test_result_int_propagate", "[error_handling][Result]") {
+    auto main_func = [&](bool is_error) -> Result<int> { return YSTDLIB_TRY(cIntFunc(is_error)); };
+    auto const main_no_error{main_func(false)};
+    REQUIRE_FALSE(main_no_error.has_error());
+    REQUIRE((cTestInt == main_no_error.value()));
+
+    auto const main_has_error{main_func(true)};
+    REQUIRE(main_has_error.has_error());
+    REQUIRE((std::errc::bad_message == main_has_error.error()));
+}
+}  // namespace ystdlib::error_handling::test