Can I Have Subfolders in a Rust "bin" project?

[Jam]

Hi, I have a project that is structured like this:

Here is my code for main.rs:

mod mod1;
use crate::mod1::fn1;
mod mod2;
use crate::mod2::fn2;

fn main() {
    let sum = fn1() + fn2();

    println!("{}", sum);
}

mod1.rs

pub fn fn1() -> u8 {
    1
}

and mod2.rs

pub fn fn2() -> u8 {
    2
}

this above code works when I run it... the modules get created automatically for mod1 and mod2.

This is cool, but I am having issues when I try to make a subfolder to group related files together.

For example, if I create a folder named "nested_mod" inside of "one_plus_two" with a mod3.rs file I would expect it to create another module with the subfolder's name be able to somehow import it into main, but I don't seem to be able to do that...

Not working code:

mod mod1;
use crate::mod1::fn1;
mod mod2;
use crate::mod2::fn2;
mod nested_mod::mod3;
use crate::nested_mod::mod3::fn3;

fn main() {
    let sum = fn1() + fn2() + fn3();

    println!("{}", sum);
}

Is there some obvious proper way to do this that I'm just missing here?

[cuviper]

You need to create nested_mod, then pub mod mod3 within that, but you can do this inline:

mod nested_mod {
    pub(super) mod mod3; // loads nested_mod/mod3.rs
}

I showed pub(super) for just one level of exposure, but you can go further if you want.

[Jam]

Huzzaaaahhhhh!!!! thank you!

[dponyatov]

Also, you can look at cargo workspaces: Cargo Workspaces - The Rust Programming Language

It will let you to have mutiple binaries and build for different platforms sharing some common code.