Definition: msg_is_number — Allowed: read-only variable inside onmqtt; Not allowed: assignment.
Helper flag inside onmqtt blocks. Set to 1 when the payload parses as a number (JSON number or numeric text). It is 0 for boolean payloads such as true/false.
onmqtt("plc/sp") {
if (msg_is_number) {
setpoint = msg_value;
save(setpoint);
}
}