Implement helpful __tostring for all userdata-based classes

Author: appgurueu

src/script/lua_api/l_areastore.cpp

@@ -330,7 +330,7 @@ void LuaAreaStore::Register(lua_State *L)
 		{"__gc", gc_object},
 		{0, 0}
 	};
-	registerClass(L, className, methods, metamethods);
+	registerClass<LuaAreaStore>(L, methods, metamethods);
 
 	// Can be created from Lua (AreaStore())
 	lua_register(L, className, create_object);

src/script/lua_api/l_base.cpp

@@ -90,29 +90,6 @@ bool ModApiBase::registerFunction(lua_State *L, const char *name,
 	return true;
 }
 
-void ModApiBase::registerClass(lua_State *L, const char *name,
-		const luaL_Reg *methods,
-		const luaL_Reg *metamethods)
-{
-	luaL_newmetatable(L, name);
-	luaL_register(L, NULL, metamethods);
-	int metatable = lua_gettop(L);
-
-	lua_newtable(L);
-	luaL_register(L, NULL, methods);
-	int methodtable = lua_gettop(L);
-
-	lua_pushvalue(L, methodtable);
-	lua_setfield(L, metatable, "__index");
-
-	// Protect the real metatable.
-	lua_pushvalue(L, methodtable);
-	lua_setfield(L, metatable, "__metatable");
-
-	// Pop methodtable and metatable.
-	lua_pop(L, 2);
-}
-
 int ModApiBase::l_deprecated_function(lua_State *L, const char *good, const char *bad, lua_CFunction func)
 {
 	thread_local std::vector<u64> deprecated_logged;

src/script/lua_api/l_base.h

@@ -60,9 +60,37 @@ class ModApiBase : protected LuaHelper {
 			lua_CFunction func,
 			int top);
 
-	static void registerClass(lua_State *L, const char *name,
+	template<typename T>
+	static void registerClass(lua_State *L,
 			const luaL_Reg *methods,
-			const luaL_Reg *metamethods);
+			const luaL_Reg *metamethods)
+	{
+		luaL_newmetatable(L, T::className);
+		luaL_register(L, NULL, metamethods);
+		int metatable = lua_gettop(L);
+
+		lua_newtable(L);
+		luaL_register(L, NULL, methods);
+		int methodtable = lua_gettop(L);
+
+		lua_pushvalue(L, methodtable);
+		lua_setfield(L, metatable, "__index");
+
+		lua_getfield(L, metatable, "__tostring");
+		bool default_tostring = lua_isnil(L, -1);
+		lua_pop(L, 1);
+		if (default_tostring) {
+			lua_pushcfunction(L, ModApiBase::defaultToString<T>);
+			lua_setfield(L, metatable, "__tostring");
+		}
+
+		// Protect the real metatable.
+		lua_pushvalue(L, methodtable);
+		lua_setfield(L, metatable, "__metatable");
+
+		// Pop methodtable and metatable.
+		lua_pop(L, 2);
+	}
 
 	template<typename T>
 	static inline T *checkObject(lua_State *L, int narg)
@@ -84,4 +112,14 @@ class ModApiBase : protected LuaHelper {
 	 * @return value from `func`
 	 */
 	static int l_deprecated_function(lua_State *L, const char *good, const char *bad, lua_CFunction func);
+
+private:
+
+	template<typename T>
+	static int defaultToString(lua_State *L)
+	{
+		auto *t = checkObject<T>(L, 1);
+		lua_pushfstring(L, "%s: %p", T::className, t);
+		return 1;
+	}
 };

src/script/lua_api/l_camera.cpp

@@ -175,7 +175,7 @@ void LuaCamera::Register(lua_State *L)
 		{"__gc", gc_object},
 		{0, 0}
 	};
-	registerClass(L, className, methods, metamethods);
+	registerClass<LuaCamera>(L, methods, metamethods);
 }
 
 const char LuaCamera::className[] = "Camera";

src/script/lua_api/l_env.cpp

@@ -124,7 +124,7 @@ void LuaRaycast::Register(lua_State *L)
 		{"__gc", gc_object},
 		{0, 0}
 	};
-	registerClass(L, className, methods, metamethods);
+	registerClass<LuaRaycast>(L, methods, metamethods);
 
 	lua_register(L, className, create_object);
 }

src/script/lua_api/l_inventory.cpp

@@ -410,7 +410,7 @@ void InvRef::Register(lua_State *L)
 		{"__gc", gc_object},
 		{0, 0}
 	};
-	registerClass(L, className, methods, metamethods);
+	registerClass<InvRef>(L, methods, metamethods);
 
 	// Cannot be created from Lua
 	//lua_register(L, className, create_object);

src/script/lua_api/l_item.cpp

@@ -524,7 +524,7 @@ void LuaItemStack::Register(lua_State *L)
 		{"__eq", l_equals},
 		{0, 0}
 	};
-	registerClass(L, className, methods, metamethods);
+	registerClass<LuaItemStack>(L, methods, metamethods);
 
 	// Can be created from Lua (ItemStack(itemstack or itemstring or table or nil))
 	lua_register(L, className, create_object);

src/script/lua_api/l_itemstackmeta.cpp

@@ -81,7 +81,7 @@ void ItemStackMetaRef::create(lua_State *L, LuaItemStack *istack)
 
 void ItemStackMetaRef::Register(lua_State *L)
 {
-	registerMetadataClass(L, className, methods);
+	registerMetadataClass<ItemStackMetaRef>(L, methods);
 }
 
 const char ItemStackMetaRef::className[] = "ItemStackMetaRef";

src/script/lua_api/l_localplayer.cpp

@@ -464,7 +464,7 @@ void LuaLocalPlayer::Register(lua_State *L)
 		{"__gc", gc_object},
 		{0, 0}
 	};
-	registerClass(L, className, methods, metamethods);
+	registerClass<LuaLocalPlayer>(L, methods, metamethods);
 }
 
 const char LuaLocalPlayer::className[] = "LocalPlayer";

src/script/lua_api/l_metadata.cpp

@@ -312,20 +312,3 @@ int MetaDataRef::l_equals(lua_State *L)
 		lua_pushboolean(L, *data1 == *data2);
 	return 1;
 }
-
-void MetaDataRef::registerMetadataClass(lua_State *L, const char *name,
-		const luaL_Reg *methods)
-{
-	const luaL_Reg metamethods[] = {
-		{"__eq", l_equals},
-		{"__gc", gc_object},
-		{0, 0}
-	};
-	registerClass(L, name, methods, metamethods);
-
-	// Set metadata_class in the metatable for MetaDataRef::checkAnyMetadata.
-	luaL_getmetatable(L, name);
-	lua_pushstring(L, name);
-	lua_setfield(L, -2, "metadata_class");
-	lua_pop(L, 1);
-}