Add function LuaUtil::cast

apps/openmw_test_suite/lua/test_lua.cpp

@@ -100,6 +100,23 @@ return {
         EXPECT_EQ(LuaUtil::toString(sol::make_object(mLua.sol(), "something")), "\"something\"");
     }
 
+    TEST_F(LuaStateTest, Cast)
+    {
+        EXPECT_EQ(LuaUtil::cast<int>(sol::make_object(mLua.sol(), 3.14)), 3);
+        EXPECT_ERROR(
+            LuaUtil::cast<int>(sol::make_object(mLua.sol(), "3.14")), "Value \"\"3.14\"\" can not be casted to int");
+        EXPECT_ERROR(LuaUtil::cast<std::string_view>(sol::make_object(mLua.sol(), sol::nil)),
+            "Value \"nil\" can not be casted to string");
+        EXPECT_ERROR(LuaUtil::cast<std::string>(sol::make_object(mLua.sol(), sol::nil)),
+            "Value \"nil\" can not be casted to string");
+        EXPECT_ERROR(LuaUtil::cast<sol::table>(sol::make_object(mLua.sol(), sol::nil)),
+            "Value \"nil\" can not be casted to sol::table");
+        EXPECT_ERROR(LuaUtil::cast<sol::function>(sol::make_object(mLua.sol(), "3.14")),
+            "Value \"\"3.14\"\" can not be casted to sol::function");
+        EXPECT_ERROR(LuaUtil::cast<sol::protected_function>(sol::make_object(mLua.sol(), "3.14")),
+            "Value \"\"3.14\"\" can not be casted to sol::function");
+    }
+
     TEST_F(LuaStateTest, ErrorHandling)
     {
         EXPECT_ERROR(mLua.runInNewSandbox("invalid.lua"), "[string \"invalid.lua\"]:1:");

components/lua/luastate.cpp

@@ -420,4 +420,25 @@ namespace LuaUtil
             return call(sol::state_view(obj.lua_state())["tostring"], obj);
     }
 
+    std::string internal::formatCastingError(const sol::object& obj, const std::type_info& t)
+    {
+        const char* typeName = t.name();
+        if (t == typeid(int))
+            typeName = "int";
+        else if (t == typeid(unsigned))
+            typeName = "uint32";
+        else if (t == typeid(size_t))
+            typeName = "size_t";
+        else if (t == typeid(float))
+            typeName = "float";
+        else if (t == typeid(double))
+            typeName = "double";
+        else if (t == typeid(sol::table))
+            typeName = "sol::table";
+        else if (t == typeid(sol::function) || t == typeid(sol::protected_function))
+            typeName = "sol::function";
+        else if (t == typeid(std::string) || t == typeid(std::string_view))
+            typeName = "string";
+        return std::string("Value \"") + toString(obj) + std::string("\" can not be casted to ") + typeName;
+    }
 }

components/lua/luastate.hpp

@@ -1,12 +1,12 @@
 #ifndef COMPONENTS_LUA_LUASTATE_H
 #define COMPONENTS_LUA_LUASTATE_H
 
+#include <filesystem>
 #include <map>
+#include <typeinfo>
 
 #include <sol/sol.hpp>
 
-#include <filesystem>
-
 #include "configuration.hpp"
 
 namespace VFS
@@ -247,15 +247,25 @@ namespace LuaUtil
     // String representation of a Lua object. Should be used for debugging/logging purposes only.
     std::string toString(const sol::object&);
 
+    namespace internal
+    {
+        std::string formatCastingError(const sol::object& obj, const std::type_info&);
+    }
+
+    template <class T>
+    decltype(auto) cast(const sol::object& obj)
+    {
+        if (!obj.is<T>())
+            throw std::runtime_error(internal::formatCastingError(obj, typeid(T)));
+        return obj.as<T>();
+    }
+
     template <class T>
     T getValueOrDefault(const sol::object& obj, const T& defaultValue)
     {
         if (obj == sol::nil)
             return defaultValue;
-        if (obj.is<T>())
+        return cast<T>(obj);
-            return obj.as<T>();
-        else
-            throw std::logic_error(std::string("Value \"") + toString(obj) + std::string("\" has unexpected type"));
     }
 
     // Makes a table read only (when accessed from Lua) by wrapping it with an empty userdata.