New base object customization point management example, derived directly form @NullCascade. Thanks!

examples/source/customization_base_object_catch.cpp

@@ -0,0 +1,176 @@
+#define SOL_ALL_SAFETIES_ON 1
+#include <sol/sol.hpp>
+#include <iostream>
+#include <exception>
+
+// We capture the base objects
+// lifetime style
+// You can add more here,
+// e.g. "Unique" for a unique pointer kind of lifestyle,
+// but you would need to think about how to handle
+// copying / moving in that case
+enum class BaseObjectLifetime { Value, Pointer, Shared };
+
+// The base object
+// that we do inheritance and other work
+// on
+class BaseObject {
+public:
+	BaseObject() {
+		objectType = 0;
+	}
+
+	unsigned int getObjectType() const {
+		return objectType;
+	}
+
+	bool doArmorThing() const {
+		return false;
+	}
+	bool doWeaponThing() const {
+		return false;
+	}
+
+	// helper function defined later after we define all the
+	// base classes we care about
+	sol::object getAsRetyped(lua_State* L, BaseObjectLifetime Lifetime) const;
+
+	// For convenience with the customization points below
+	int pushAsRetyped(lua_State* L, BaseObjectLifetime Lifetime) const {
+		return getAsRetyped(L, Lifetime).push(L);
+	}
+
+protected:
+	unsigned int objectType;
+};
+
+class Armor : public BaseObject {
+public:
+	Armor() {
+		objectType = 1;
+	}
+
+	bool doArmorThing() const {
+		return true;
+	}
+};
+
+class Weapon : public BaseObject {
+public:
+	Weapon() {
+		objectType = 2;
+	}
+
+	bool doWeaponThing() const {
+		return true;
+	}
+};
+
+// Get the most-derived type
+// that we care about from the base object,
+// obeying the lifetime type
+sol::object BaseObject::getAsRetyped(lua_State* L, BaseObjectLifetime Lifetime) const {
+	switch (objectType) {
+	case 1:
+		std::cout << "Retyping as armor." << std::endl;
+		switch (Lifetime) {
+		case BaseObjectLifetime::Value:
+			return sol::make_object(L, *static_cast<const Armor*>(this));
+		case BaseObjectLifetime::Pointer:
+			return sol::make_object(L, static_cast<const Armor*>(this));
+		case BaseObjectLifetime::Shared:
+			return sol::make_object(L, std::make_shared<Armor>(*static_cast<const Armor*>(this)));
+		}
+	case 2:
+		std::cout << "Retyping as weapon." << std::endl;
+		switch (Lifetime) {
+		case BaseObjectLifetime::Value:
+			return sol::make_object(L, *static_cast<const Weapon*>(this));
+		case BaseObjectLifetime::Pointer:
+			return sol::make_object(L, static_cast<const Weapon*>(this));
+		case BaseObjectLifetime::Shared:
+			return sol::make_object(L, std::make_shared<Weapon>(*static_cast<const Weapon*>(this)));
+		}
+	default:
+		// we have a normal type here, so that means we
+		// must bypass customization points
+		std::cout << "Unknown type: falling back to base object." << std::endl;
+		switch (Lifetime) {
+		case BaseObjectLifetime::Value:
+			return sol::make_object_userdata(L, *this);
+		case BaseObjectLifetime::Shared:
+			return sol::make_object_userdata(L, std::make_shared<BaseObject>(*this));
+		case BaseObjectLifetime::Pointer:
+		default:
+			return sol::make_object_userdata(L, this);
+		}
+	}
+}
+
+//
+// sol customization points
+//
+
+// Defining a customization point that lets us put the correct object type on the stack.
+int sol_lua_push(sol::types<BaseObject>, lua_State* L, const BaseObject& obj) {
+	return obj.pushAsRetyped(L, BaseObjectLifetime::Value);
+}
+int sol_lua_push(sol::types<BaseObject*>, lua_State* L, const BaseObject* obj) {
+	return obj->pushAsRetyped(L, BaseObjectLifetime::Pointer);
+}
+int sol_lua_push(sol::types<std::shared_ptr<BaseObject>>, lua_State* L, const std::shared_ptr<BaseObject>& obj) {
+	return obj->pushAsRetyped(L, BaseObjectLifetime::Shared);
+}
+
+int main() {
+    // test our customization points out
+    std::cout << "=== Base object customization points ===" << std::endl;
+
+	sol::state lua;
+	lua.open_libraries(sol::lib::base, sol::lib::string, sol::lib::table);
+
+	lua["objectCache"] = lua.create_table();
+
+	// Do basic type binding.
+	auto luaBaseObject = lua.new_usertype<BaseObject>("tes3baseObject");
+	luaBaseObject["objectType"] = sol::readonly_property(&BaseObject::getObjectType);
+	luaBaseObject["doArmorThing"] = &BaseObject::doArmorThing;
+	luaBaseObject["doWeaponThing"] = &BaseObject::doWeaponThing;
+	auto luaArmorObject = lua.new_usertype<Armor>("tes3armor");
+	luaArmorObject[sol::base_classes] = sol::bases<BaseObject>();
+	luaArmorObject["doArmorThing"] = &Armor::doArmorThing;
+	auto luaWeaponObject = lua.new_usertype<Weapon>("tes3weapon");
+	luaWeaponObject[sol::base_classes] = sol::bases<BaseObject>();
+	luaWeaponObject["doWeaponThing"] = &Weapon::doWeaponThing;
+
+	// Objects we'll play with.
+	BaseObject base;
+	Armor armor;
+	Weapon weapon;
+
+	// Push some objects to lua.
+	std::cout << "Normal pointers..." << std::endl;
+	lua["ptrBase"] = &base;
+	lua["ptrArmor"] = &armor;
+	lua["ptrWeapon"] = &weapon;
+	std::cout << std::endl;
+
+	// Same objects but as base objects to test mapping.
+	std::cout << "Base-cast pointers..." << std::endl;
+	lua["ptrArmorAsBase"] = static_cast<BaseObject*>(&armor);
+	lua["ptrWeaponAsBase"] = static_cast<BaseObject*>(&weapon);
+	std::cout << std::endl;
+
+	std::cout << "Smart direct pointers..." << std::endl;
+	lua["sharedBase"] = std::make_shared<BaseObject>();
+	lua["sharedArmor"] = std::make_shared<Armor>();
+	lua["sharedArmor"] = std::make_shared<Weapon>();
+	std::cout << std::endl;
+
+	std::cout << "Smart pointers put as the base class..." << std::endl;
+	lua["sharedArmorAsBase"] = (std::shared_ptr<BaseObject>)std::make_shared<Armor>();
+	lua["sharedArmorAsBase"] = (std::shared_ptr<BaseObject>)std::make_shared<Weapon>();
+	std::cout << std::endl;
+
+	return 0;
+}

include/sol/make_reference.hpp

@@ -49,6 +49,26 @@ namespace sol {
 		return r;
 	}
 
+	template <typename R = reference, bool should_pop = !is_stack_based_v<R>, typename T>
+	R make_reference_userdata(lua_State* L, T&& value) {
+		int backpedal = stack::push_userdata(L, std::forward<T>(value));
+		R r = stack::get<R>(L, -backpedal);
+		if (should_pop) {
+			lua_pop(L, backpedal);
+		}
+		return r;
+	}
+
+	template <typename T, typename R = reference, bool should_pop = !is_stack_based_v<R>, typename... Args>
+	R make_reference_userdata(lua_State* L, Args&&... args) {
+		int backpedal = stack::push_userdata<T>(L, std::forward<Args>(args)...);
+		R r = stack::get<R>(L, -backpedal);
+		if (should_pop) {
+			lua_pop(L, backpedal);
+		}
+		return r;
+	}
+
 } // namespace sol
 
 #endif // SOL_MAKE_REFERENCE_HPP

include/sol/object.hpp

@@ -146,6 +146,16 @@ namespace sol {
 	object make_object(lua_State* L, Args&&... args) {
 		return make_reference<T, object, true>(L, std::forward<Args>(args)...);
 	}
+
+	template <typename T>
+	object make_object_userdata(lua_State* L, T&& value) {
+		return make_reference_userdata<object, true>(L, std::forward<T>(value));
+	}
+
+	template <typename T, typename... Args>
+	object make_object_userdata(lua_State* L, Args&&... args) {
+		return make_reference_userdata<T, object, true>(L, std::forward<Args>(args)...);
+	}
 } // namespace sol
 
 #endif // SOL_OBJECT_HPP

include/sol/stack_core.hpp

@@ -55,6 +55,8 @@ namespace sol {
 		template <typename T>
 		struct as_value_tag {};
 		template <typename T>
+		struct as_unique_tag {};
+		template <typename T>
 		struct as_table_tag {};
 
 		using lua_reg_table = luaL_Reg[64];
@@ -921,14 +923,26 @@ namespace sol {
 		template <typename T, typename... Args>
 		int push_userdata(lua_State* L, T&& t, Args&&... args) {
 			using U = meta::unqualified_t<T>;
-			using Tr = meta::conditional_t<std::is_pointer<U>::value, detail::as_pointer_tag<std::remove_pointer_t<U>>, detail::as_value_tag<U>>;
+			using Tr = meta::conditional_t<std::is_pointer_v<U>,
+				detail::as_pointer_tag<std::remove_pointer_t<U>>,
+				meta::conditional_t<is_unique_usertype_v<U>,
+					detail::as_unique_tag<U>,
+					detail::as_value_tag<U>
+				>
+			>;
 			return stack::push<Tr>(L, std::forward<T>(t), std::forward<Args>(args)...);
 		}
 
 		template <typename T, typename Arg, typename... Args>
 		int push_userdata(lua_State* L, Arg&& arg, Args&&... args) {
 			using U = meta::unqualified_t<T>;
-			using Tr = meta::conditional_t<std::is_pointer<U>::value, detail::as_pointer_tag<std::remove_pointer_t<U>>, detail::as_value_tag<U>>;
+			using Tr = meta::conditional_t<std::is_pointer_v<U>,
+				detail::as_pointer_tag<std::remove_pointer_t<U>>,
+				meta::conditional_t<is_unique_usertype_v<U>,
+					detail::as_unique_tag<U>,
+					detail::as_value_tag<U>
+				>
+			>;
 			return stack::push<Tr>(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
 		}
 

include/sol/stack_push.hpp

@@ -189,6 +189,16 @@ namespace sol { namespace stack {
 		}
 	};
 
+	template <typename T>
+	struct unqualified_pusher<detail::as_unique_tag<T>> {
+		template <typename... Args>
+		static int push (lua_State* L, Args&&... args) {
+			stack_detail::uu_pusher<T> p;
+			(void)p;
+			return p.push(L, std::forward<Args>(args)...);
+		}
+	};
+
 	namespace stack_detail {
 		template <typename T>
 		struct uu_pusher {
@@ -293,9 +303,7 @@ namespace sol { namespace stack {
 				return stack::push<detail::as_pointer_tag<std::remove_pointer_t<T>>>(L, std::forward<Args>(args)...);
 			}
 			else if constexpr (is_unique_usertype_v<Tu>) {
-				stack_detail::uu_pusher<T> p;
-				(void)p;
-				return p.push(L, std::forward<Args>(args)...);
+				return stack::push<detail::as_unique_tag<T>>(L, std::forward<Args>(args)...);
 			}
 			else {
 				return stack::push<detail::as_value_tag<T>>(L, std::forward<Args>(args)...);

single/include/sol/forward.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2020-01-17 10:21:31.165776 UTC
-// This header was generated with sol v3.2.0 (revision 1c89390)
+// Generated 2020-01-25 00:57:45.038692 UTC
+// This header was generated with sol v3.2.0 (revision c77b5b4)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_FORWARD_HPP

single/include/sol/sol.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2020-01-17 10:21:30.504542 UTC
-// This header was generated with sol v3.2.0 (revision 1c89390)
+// Generated 2020-01-25 00:57:44.490128 UTC
+// This header was generated with sol v3.2.0 (revision c77b5b4)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_HPP
@@ -9499,6 +9499,8 @@ namespace sol {
 		template <typename T>
 		struct as_value_tag {};
 		template <typename T>
+		struct as_unique_tag {};
+		template <typename T>
 		struct as_table_tag {};
 
 		using lua_reg_table = luaL_Reg[64];
@@ -10364,14 +10366,26 @@ namespace sol {
 		template <typename T, typename... Args>
 		int push_userdata(lua_State* L, T&& t, Args&&... args) {
 			using U = meta::unqualified_t<T>;
-			using Tr = meta::conditional_t<std::is_pointer<U>::value, detail::as_pointer_tag<std::remove_pointer_t<U>>, detail::as_value_tag<U>>;
+			using Tr = meta::conditional_t<std::is_pointer_v<U>,
+				detail::as_pointer_tag<std::remove_pointer_t<U>>,
+				meta::conditional_t<is_unique_usertype_v<U>,
+					detail::as_unique_tag<U>,
+					detail::as_value_tag<U>
+				>
+			>;
 			return stack::push<Tr>(L, std::forward<T>(t), std::forward<Args>(args)...);
 		}
 
 		template <typename T, typename Arg, typename... Args>
 		int push_userdata(lua_State* L, Arg&& arg, Args&&... args) {
 			using U = meta::unqualified_t<T>;
-			using Tr = meta::conditional_t<std::is_pointer<U>::value, detail::as_pointer_tag<std::remove_pointer_t<U>>, detail::as_value_tag<U>>;
+			using Tr = meta::conditional_t<std::is_pointer_v<U>,
+				detail::as_pointer_tag<std::remove_pointer_t<U>>,
+				meta::conditional_t<is_unique_usertype_v<U>,
+					detail::as_unique_tag<U>,
+					detail::as_value_tag<U>
+				>
+			>;
 			return stack::push<Tr>(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
 		}
 
@@ -13262,6 +13276,16 @@ namespace sol { namespace stack {
 		}
 	};
 
+	template <typename T>
+	struct unqualified_pusher<detail::as_unique_tag<T>> {
+		template <typename... Args>
+		static int push (lua_State* L, Args&&... args) {
+			stack_detail::uu_pusher<T> p;
+			(void)p;
+			return p.push(L, std::forward<Args>(args)...);
+		}
+	};
+
 	namespace stack_detail {
 		template <typename T>
 		struct uu_pusher {
@@ -13366,9 +13390,7 @@ namespace sol { namespace stack {
 				return stack::push<detail::as_pointer_tag<std::remove_pointer_t<T>>>(L, std::forward<Args>(args)...);
 			}
 			else if constexpr (is_unique_usertype_v<Tu>) {
-				stack_detail::uu_pusher<T> p;
-				(void)p;
-				return p.push(L, std::forward<Args>(args)...);
+				return stack::push<detail::as_unique_tag<T>>(L, std::forward<Args>(args)...);
 			}
 			else {
 				return stack::push<detail::as_value_tag<T>>(L, std::forward<Args>(args)...);
@@ -14870,6 +14892,26 @@ namespace sol {
 		return r;
 	}
 
+	template <typename R = reference, bool should_pop = !is_stack_based_v<R>, typename T>
+	R make_reference_userdata(lua_State* L, T&& value) {
+		int backpedal = stack::push_userdata(L, std::forward<T>(value));
+		R r = stack::get<R>(L, -backpedal);
+		if (should_pop) {
+			lua_pop(L, backpedal);
+		}
+		return r;
+	}
+
+	template <typename T, typename R = reference, bool should_pop = !is_stack_based_v<R>, typename... Args>
+	R make_reference_userdata(lua_State* L, Args&&... args) {
+		int backpedal = stack::push_userdata<T>(L, std::forward<Args>(args)...);
+		R r = stack::get<R>(L, -backpedal);
+		if (should_pop) {
+			lua_pop(L, backpedal);
+		}
+		return r;
+	}
+
 } // namespace sol
 
 // end of sol/make_reference.hpp
@@ -15052,6 +15094,16 @@ namespace sol {
 	object make_object(lua_State* L, Args&&... args) {
 		return make_reference<T, object, true>(L, std::forward<Args>(args)...);
 	}
+
+	template <typename T>
+	object make_object_userdata(lua_State* L, T&& value) {
+		return make_reference_userdata<object, true>(L, std::forward<T>(value));
+	}
+
+	template <typename T, typename... Args>
+	object make_object_userdata(lua_State* L, Args&&... args) {
+		return make_reference_userdata<T, object, true>(L, std::forward<Args>(args)...);
+	}
 } // namespace sol
 
 // end of sol/object.hpp