Okay to use unwrap() when I'm sure variable is Some?

help
1

I know using unwrap() is considered bad practice but is it okay to use in this code?

    let path_str = "some/path/to/file.txt";
    let path = std::path::Path::new(path_str);
    std::fs::create_dir_all(path.parent().unwrap())?;

Because path_str is hard-coded I am sure it has a parent() and won't be None. Is unwrap() okay here?

2

Personally I think that is fine, but if it bothers you, you could do this instead:

let dir = Path::new("some/path/to");
std::fs::create_dir_all(dir)?;
let path = dir.join("file.txt");
4 Likes
3

Yes. It's even preferable to ?, in my opinion.

It's basically this case, from Using unwrap() in Rust is Okay - Andrew Gallant's Blog

Is it a bug if the program couldn’t build a regular expression from a static string literal? Yup. The programmer typed that regex. It should be correct. So a panic is appropriate.

7 Likes
4

I still find this ugly.

The only time I find unwrapping tolerable is when I personally put a literal Some in an optional just before the unwrap, so that it's blatantly obvious there will be no possibility for panic.

In the above case, you are instead relying on a computation (getting the parent of a path) behaving in a particular way and returning a particular value. That's pretty fragile.

You should indeed invert the dependency and compute the child from the parent, not the other way around.

5

This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.