Hi, I'm very new to Rhai/Rust.

Problem

I would like to implement a trait in my Engine declaration code, and not expose functions in Rhai scripts that take the trait as an argument. For example, the implementation would be pub fn hello(arg1: &str, arg2: &str) but in Rhai, I would only want hello(arg2: &str) to be available.

I have a working example (which follows) without using Rhai plugin macros, but I was wondering if there is a better way to do this/something more idiomatic. It also seems like overriding each function that I implement this way with an implementation of the trait might not be the most scalable engine registration code.

Thanks!

Code

Rhai crate

pub trait Policy: Debug {
    fn is_allowed(&self, path: &str) -> bool;
}

pub fn my_fn(
    policy: &impl Policy,
    path: &str,
) -> Result<String, Box<EvalAltResult>> {
    if !policy.is_allowed(path) {
        return Err(format!("not allowed {}!!!", path).into());
    }

   // rest of my code
   ...
}

Engine creation code in a different crate

fn engine_create_and_register() -> Engine {
    let mut engine = Engine::new();

    // implements the trait Policy elsewhere
    let policy = MyImpl::new();

    let fn_overload =
        move |path: &str| -> Result<String, Box<EvalAltResult>> {
            my_fn(&policy, path)
        };

    engine.register_fn("my_fn", fn_overload);
    engine
}

Call my script

Notice that when my Rhai script is written, I do not need to provide the Policy implementation, which is my desired behavior

my_fn("/tmp/hello.txt");