What is the ruling regarding someone who swore by Allah not to do something, then did it under duress?

Whoever swears an oath and then breaks it must offer an expiation (kaffarat yameen), which is: feeding ten poor persons, or clothing them, or freeing a slave. If unable to do so, then fasting for three days. Breaking the oath may sometimes be better. Whoever is compelled to do something they swore not to do, and the conditions for compulsion (ikrah) are met, then there is no expiation upon them. If the conditions for compulsion are not met, then they must offer an expiation.