What does 1 Samuel 20:12 mean?

Jonathan said to David, I promise, by the Lord, the God of Israel, that I’ll find out how my father feels about you by tomorrow or the next day. If he’s friendly, I’ll let you know. But if he’s planning to hurt you, I’ll warn you so you can get away. May the Lord punish me if I don’t tell you. 1 Samuel 20:12 - Modern Text Bible

(Jonathan swears an oath to God that he’ll find out Saul’s intentions and let David know, even if it means going against his own father.)