feat(error_handling): Add Result<T, E> alias and macros to enable ergonomic Rust-style error handling. (#47)

Co-authored-by: Lin Zhihao <59785146+LinZhihao-723@users.noreply.github.com>

Author: Bill-hbrhbr

src/ystdlib/error_handling/CMakeLists.txt

@@ -4,10 +4,14 @@ cpp_library(
     PUBLIC_HEADERS
         ErrorCode.hpp
         TraceableException.hpp
+        Result.hpp
         utils.hpp
+    PUBLIC_LINK_LIBRARIES
+        outcome::hl
     TESTS_SOURCES
         test/constants.hpp
         test/test_ErrorCode.cpp
+        test/test_Result.cpp
         test/test_TraceableException.cpp
         test/types.cpp
         test/types.hpp

src/ystdlib/error_handling/Result.hpp

@@ -0,0 +1,66 @@
+#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>
+#include <outcome/try.hpp>
+
+namespace ystdlib::error_handling {
+/**
+ * A Rust-style `Result<T, E>` type for standardized, exception-free error handling.
+ *
+ * This alias standardizes error handling across the codebase by defaulting the error type to
+ * `std::error_code`, which interoperates with the `ystdlib::error_handling::ErrorCode`, making it
+ * easier to compose errors and propagate them across different modules and libraries.
+ *
+ * @tparam ReturnType The type returned on success.
+ * @tparam ErrorType The type used to represent errors.
+ */
+template <typename ReturnType, typename ErrorType = std::error_code>
+using Result = OUTCOME_V2_NAMESPACE::std_result<ReturnType, ErrorType>;
+
+/**
+ * @return A value indicating successful completion of a function that returns a void result (i.e.,
+ * `Result<void, E>`).
+ */
+[[nodiscard]] inline auto success() -> OUTCOME_V2_NAMESPACE::success_type<void> {
+    return OUTCOME_V2_NAMESPACE::success();
+}
+
+/**
+ * A function-style macro that emulates Rust’s try (`?`) operator for error propagation.
+ *
+ * @param expr An expression that evaluates to a `Result` object.
+ *
+ * Behavior:
+ * - If `expr` represents an error (i.e., `expr.has_error()` returns true), the macro performs an
+ *   early return from the enclosing function with the contained error.
+ * - Otherwise, it unwraps and yields the successful value as an rvalue reference (`expr.value()`).
+ *
+ * NOTE: This macro is only supported on GCC and Clang due to reliance on compiler-specific
+ * extensions.
+ */
+#ifdef OUTCOME_TRYX
+    // NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+    #define YSTDLIB_ERROR_HANDLING_TRYX(expr) OUTCOME_TRYX(expr)
+#endif
+
+/**
+ * A function-style macro for propagating errors from expressions that evaluate to a void result
+ * (`Result<void, E>`).
+ *
+ * @param expr An expression that evaluates to a `Result<void, E>` object.
+ *
+ * Behavior:
+ * - If `expr` represents an error (i.e., `expr.has_error()` returns true), the macro performs an
+ *   early return from the enclosing function with the contained error.
+ * - Otherwise, execution continues normally.
+ */
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define YSTDLIB_ERROR_HANDLING_TRYV(expr) OUTCOME_TRYV(expr)
+}  // namespace ystdlib::error_handling
+
+#endif  // YSTDLIB_ERROR_HANDLING_RESULT_HPP

src/ystdlib/error_handling/test/test_Result.cpp

@@ -0,0 +1,139 @@
+#include <memory>
+#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::AlwaysSuccessErrorCode;
+using ystdlib::error_handling::test::AlwaysSuccessErrorCodeEnum;
+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;
+};
+constexpr auto cUniquePtrFunc = [](bool is_error) -> Result<std::unique_ptr<int>> {
+    if (is_error) {
+        return AlwaysSuccessErrorCode{AlwaysSuccessErrorCodeEnum::Success};
+    }
+    return std::make_unique<int>(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_ERROR_HANDLING_TRYV(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_ERROR_HANDLING_TRYV(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_ERROR_HANDLING_TRYX(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());
+}
+
+TEST_CASE("test_result_unique_ptr", "[error_handling][Result]") {
+    auto const result_no_error{cUniquePtrFunc(false)};
+    REQUIRE_FALSE(result_no_error.has_error());
+    REQUIRE(cTestInt == *(result_no_error.value()));
+
+    auto const result_has_error{cUniquePtrFunc(true)};
+    REQUIRE(result_has_error.has_error());
+    REQUIRE(AlwaysSuccessErrorCode{AlwaysSuccessErrorCodeEnum::Success} == result_has_error.error()
+    );
+}
+
+TEST_CASE("test_result_unique_ptr_in_main", "[error_handling][Result]") {
+    auto main_func = [&](bool is_error) -> Result<void> {
+        YSTDLIB_ERROR_HANDLING_TRYV(cUniquePtrFunc(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(AlwaysSuccessErrorCode{AlwaysSuccessErrorCodeEnum::Success} == main_has_error.error());
+}
+
+TEST_CASE("test_result_unique_ptr_propagate", "[error_handling][Result]") {
+    auto main_func = [&](bool is_error) -> Result<std::unique_ptr<int>> {
+        return YSTDLIB_ERROR_HANDLING_TRYX(cUniquePtrFunc(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(AlwaysSuccessErrorCode{AlwaysSuccessErrorCodeEnum::Success} == main_has_error.error());
+}
+}  // namespace ystdlib::error_handling::test