What is the ruling regarding someone who intended to fast a supererogatory fast, such as Ashura, from the night, then broke their fast intentionally or unintentionally, and what are the consequences of that?

Scholars differ regarding one who intended to observe a supererogatory fast (nafl), then intentionally broke it without an excuse. The Malikis and Hanafis are of the view that it is obligatory for him to make up the fast (qada'), because according to them, a supererogatory fast becomes obligatory once one commences it. As for the Shafi'is and Hanbalis, they hold the view that it is permissible for one observing a voluntary fast to break it, and there is no make-up required of him, and this is the more preponderant opinion. However, regarding breaking the fast forgetfully, there is no make-up required for it by scholarly consensus.