LuaItemStack: Add __tostring metamethod (#8785)

* LuaItemStack: Add __tostring metamethod

* Clean up LuaItemStack::checkobject

2 files changed, 21 insertions, 7 deletions

diff --git a/src/script/lua_api/l_item.cpp b/src/script/lua_api/l_item.cpp
index 0a403acbd..d67cab76f 100644
--- a/src/script/lua_api/l_item.cpp
+++ b/src/script/lua_api/l_item.cpp
@@ -37,6 +37,15 @@ int LuaItemStack::gc_object(lua_State *L)
 	return 0;
 }
 
+// __tostring metamethod
+int LuaItemStack::mt_tostring(lua_State *L)
+{
+	LuaItemStack *o = checkobject(L, 1);
+	std::string itemstring = o->m_stack.getItemString(false);
+	lua_pushfstring(L, "ItemStack(\"%s\")", itemstring.c_str());
+	return 1;
+}
+
 // is_empty(self) -> true/false
 int LuaItemStack::l_is_empty(lua_State *L)
 {
@@ -433,12 +442,9 @@ int LuaItemStack::create(lua_State *L, const ItemStack &item)
 	return 1;
 }
 
-LuaItemStack* LuaItemStack::checkobject(lua_State *L, int narg)
+LuaItemStack *LuaItemStack::checkobject(lua_State *L, int narg)
 {
-	luaL_checktype(L, narg, LUA_TUSERDATA);
-	void *ud = luaL_checkudata(L, narg, className);
-	if(!ud) luaL_typerror(L, narg, className);
-	return *(LuaItemStack**)ud;  // unbox pointer
+	return *(LuaItemStack **)luaL_checkudata(L, narg, className);
 }
 
 void LuaItemStack::Register(lua_State *L)
@@ -448,9 +454,10 @@ void LuaItemStack::Register(lua_State *L)
 	luaL_newmetatable(L, className);
 	int metatable = lua_gettop(L);
 
+	// hide metatable from Lua getmetatable()
 	lua_pushliteral(L, "__metatable");
 	lua_pushvalue(L, methodtable);
-	lua_settable(L, metatable);  // hide metatable from Lua getmetatable()
+	lua_settable(L, metatable);
 
 	lua_pushliteral(L, "__index");
 	lua_pushvalue(L, methodtable);
@@ -460,12 +467,16 @@ void LuaItemStack::Register(lua_State *L)
 	lua_pushcfunction(L, gc_object);
 	lua_settable(L, metatable);
 
+	lua_pushliteral(L, "__tostring");
+	lua_pushcfunction(L, mt_tostring);
+	lua_settable(L, metatable);
+
 	lua_pop(L, 1);  // drop metatable
 
 	luaL_openlib(L, 0, methods, 0);  // fill methodtable
 	lua_pop(L, 1);  // drop methodtable
 
-	// Can be created from Lua (LuaItemStack(itemstack or itemstring or table or nil))
+	// Can be created from Lua (ItemStack(itemstack or itemstring or table or nil))
 	lua_register(L, className, create_object);
 }
 
diff --git a/src/script/lua_api/l_item.h b/src/script/lua_api/l_item.h
index 6fab58045..98744c071 100644
--- a/src/script/lua_api/l_item.h
+++ b/src/script/lua_api/l_item.h
@@ -34,6 +34,9 @@ private:
 	// garbage collector
 	static int gc_object(lua_State *L);
 
+	// __tostring metamethod
+	static int mt_tostring(lua_State *L);
+
 	// is_empty(self) -> true/false
 	static int l_is_empty(lua_State *L);