reaction: add package (#6921)

* reaction: add package

* add check

packages/r/reaction/xmake.lua

@@ -0,0 +1,49 @@
+package("reaction")
+    set_kind("library", {headeronly = true})
+    set_homepage("https://github.com/lumia431/reaction")
+    set_description("A lightweight, header-only reactive programming framework leveraging modern C++20 features for building efficient dataflow applications.")
+    set_license("MIT")
+
+    add_urls("https://github.com/lumia431/reaction.git")
+    add_versions("2025.04.16", "424f1956f2215b0817fd1b3b4217ee04b0c45e2a")
+
+    add_deps("cmake")
+
+    on_check(function (package)
+        if package:is_plat("android") then
+            local ndk = package:toolchain("ndk"):config("ndkver")
+            assert(ndk and tonumber(ndk) > 22, "package(ada >=3.0.0) require ndk version > 22")
+        elseif package:is_plat("macosx") then
+            assert(package:check_cxxsnippets({test = [[#include <format>
+                    #include <iostream>
+                    
+                    template<typename... Args>
+                    inline void println(const std::format_string<Args...> fmt, Args&&... args)
+                    {
+                        std::cout << std::vformat(fmt.get(), std::make_format_args(args...)) << '\n';
+                    }
+                void test() {
+                    println("{}{} {}{}", "Hello", ',', "C++", -1 + 2 * 3 * 4);
+                }
+            ]]}, {configs = {languages = "c++20"}}))
+        end
+    end)
+
+    on_install(function (package)
+        io.replace("CMakeLists.txt", "if(GTest_FOUND)", "if(0)", {plain = true})
+        os.tryrm("example")
+
+        local configs = {}
+        table.insert(configs, "-DCMAKE_BUILD_TYPE=" .. (package:is_debug() and "Debug" or "Release"))
+        import("package.tools.cmake").install(package, configs)
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            #include <algorithm>
+            #include <reaction/reaction.h>
+            void test() {
+                auto buyPrice = reaction::var(100.0);
+            }
+        ]]}, {configs = {languages = "c++20"}}))
+    end)