Modernize lua read (part 2 & 3): C++ templating assurance (#7410)

* Modernize lua read (part 2 & 3): C++ templating assurance

Implement the boolean reader
Implement the string reader
Also remove unused & unimplemented script_error_handler
Add a reader with default value

src/script/lua_api/l_util.cpp

@@ -135,7 +135,7 @@ int ModApiUtil::l_write_json(lua_State *L)
 
 	bool styled = false;
 	if (!lua_isnone(L, 2)) {
-		styled = lua_toboolean(L, 2);
+		styled = readParam<bool>(L, 2);
 		lua_pop(L, 1);
 	}
 
@@ -231,7 +231,7 @@ int ModApiUtil::l_is_yes(lua_State *L)
 	lua_getglobal(L, "tostring"); // function to be called
 	lua_pushvalue(L, 1); // 1st argument
 	lua_call(L, 1, 1); // execute function
-	std::string str(lua_tostring(L, -1)); // get result
+	std::string str = readParam<std::string>(L, -1); // get result
 	lua_pop(L, 1);
 
 	bool yes = is_yes(str);
@@ -342,7 +342,7 @@ int ModApiUtil::l_get_dir_list(lua_State *L)
 	NO_MAP_LOCK_REQUIRED;
 	const char *path = luaL_checkstring(L, 1);
 	bool list_all = !lua_isboolean(L, 2); // if its not a boolean list all
-	bool list_dirs = lua_toboolean(L, 2); // true: list dirs, false: list files
+	bool list_dirs = readParam<bool>(L, 2); // true: list dirs, false: list files
 
 	CHECK_SECURE_PATH(L, path, false);
 
@@ -410,7 +410,7 @@ int ModApiUtil::l_request_insecure_environment(lua_State *L)
 	}
 
 	// Check secure.trusted_mods
-	const char *mod_name = lua_tostring(L, -1);
+	std::string mod_name = readParam<std::string>(L, -1);
 	std::string trusted_mods = g_settings->get("secure.trusted_mods");
 	trusted_mods.erase(std::remove_if(trusted_mods.begin(),
 			trusted_mods.end(), static_cast<int(*)(int)>(&std::isspace)),
@@ -451,7 +451,7 @@ int ModApiUtil::l_sha1(lua_State *L)
 	NO_MAP_LOCK_REQUIRED;
 	size_t size;
 	const char *data = luaL_checklstring(L, 1, &size);
-	bool hex = !lua_isboolean(L, 2) || !lua_toboolean(L, 2);
+	bool hex = !lua_isboolean(L, 2) || !readParam<bool>(L, 2);
 
 	// Compute actual checksum of data
 	std::string data_sha1;