From 01e1520414302e4db016d21008fb9f68b5961e56 Mon Sep 17 00:00:00 2001
From: Vitaly Fanaskov <vt4a2h@gmail.com>
Date: Sun, 7 Jan 2024 00:00:16 +0100
Subject: [PATCH] Add a cmake check whether std::expected is supported or not

Note. Perhaps a wrong way. Please let me know if there is something better.
---
 CMakePresets.json                   |  2 +-
 cmake/helpers.cmake                 | 10 ++++++++++
 cmake/try-compile-apps/expected.cpp | 12 ++++++++++++
 test/CMakeLists.txt                 |  5 +++++
 4 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 cmake/helpers.cmake
 create mode 100644 cmake/try-compile-apps/expected.cpp

diff --git a/CMakePresets.json b/CMakePresets.json
index 1c21bb7..390ec07 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -1,5 +1,5 @@
 {
-  "version": 3,
+  "version": 6,
   "cmakeMinimumRequired": {
     "major": 3,
     "minor": 17,
diff --git a/cmake/helpers.cmake b/cmake/helpers.cmake
new file mode 100644
index 0000000..dea7c65
--- /dev/null
+++ b/cmake/helpers.cmake
@@ -0,0 +1,10 @@
+function(has_expected OUT_RESULT)
+    try_compile(COMPILE_RESULT
+        ${CMAKE_BINARY_DIR}/test_apps
+        ${CMAKE_SOURCE_DIR}/cmake/try-compile-apps/expected.cpp
+        CXX_STANDARD 23
+        CXX_STANDARD_REQUIRED TRUE
+        CXX_EXTENSIONS FALSE
+    )
+    set(${OUT_RESULT} ${COMPILE_RESULT} PARENT_SCOPE)
+endfunction()
\ No newline at end of file
diff --git a/cmake/try-compile-apps/expected.cpp b/cmake/try-compile-apps/expected.cpp
new file mode 100644
index 0000000..6fd2579
--- /dev/null
+++ b/cmake/try-compile-apps/expected.cpp
@@ -0,0 +1,12 @@
+#include <expected>
+#include <string>
+
+int main(int /*argc*/, char* /*argv*/[])
+{
+    using Expected = std::expected<int, std::string>;
+
+    Expected result{0};
+    Expected unxepectedResult = std::unexpected(std::string{"foo"});
+
+    return result != unxepectedResult ? *result : -1;
+}
\ No newline at end of file
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c3cdc1f..3d3fcc8 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,3 +1,8 @@
+include(${CMAKE_SOURCE_DIR}/cmake/helpers.cmake)
+
+has_expected(HAS_EXPECTED_RESULT)
+message(STATUS "Has std::expected support: ${HAS_EXPECTED_RESULT}")
+
 find_package(Catch2 CONFIG REQUIRED)
 find_package(fmt CONFIG REQUIRED)
 find_package(spdlog CONFIG REQUIRED)