That one's not really a spoiler. The heroes set out to do that to win, and it's obviously the type of movie where the heroes win. What's less certain is how exactly they'll get there.
How would I know that if I haven’t seen it
Is a young girl in peril? Don't worry, nothing will happen to her, the audiences won't like it.
Have we been focused on one guy for the first 20 minutes? He definitely won't die, at least until the end. And he will achieve something great regardless; it won't all be for nothing.
Did they show a gun in some scene? That's important for later; some guy called Chekhov wants it back.
Once you see the boundaries in modern storytelling, it definitely makes things rather predictable.
If you want to see a film that breaks some of the rules, watch Brimstone.
Edit: And considering when it was made and who made it, a happy ending was by no means guaranteed. Compare and contrast with the endings of Silent Running or American Graffiti.
Silent Running is a dystopian setting, so the ending is unsurprising, and American Graffiti is a of genre that often has bad outcomes for some characters as cautionary tales.