Trying to understand the safety of using references in Rhai

[gitstashpop]

Hi,

I have the following Rust fn I'm registering in Rhai.

pub fn open(
    dir_state: Rc<DirState>,
    file_name: &str,
) -> Result<Rc<FileState>, Box<EvalAltResult>> {
    match open_helper(&dir_state, file_name) {
        Ok(file_state) => Ok(file_state),
        Err(e) => Err(format!("{e:#}").into()),
    }
}

let mut engine: Engine = Engine::new();
engine.register_fn("open", open);

And an implementation in another crate

pub fn open_helper(dir_state: &Rc<DirState>, file_name: &str) -> Result<Rc<FileState>> {
  ....
}

1. Are there any issues with passing a reference to dir_state to my Rust fn (open_helper) from open()? The current implementation seems to work without any issues in my scripts, but I am wondering if this counts as an external reference. If it is, how would I implement this in a safe way?
2. When I changed open()'s dir_state argument to be a reference, my Rhai scripts had no idea how to handle references.

New fn sig:

pub fn open(
    dir_state: &Rc<DirState>,
    file_name: &str,
) -> Result<Rc<FileState>, Box<EvalAltResult>> {

And the Rhai script:

let dir = open_dir(temp_dir_path);
let file = open_file(&dir, "foo.txt");

Gives this error:

Function not found: open_file (alloc::rc::Rc<DirState>, &str | ImmutableString | String) (line 3, position 28)

Is that functionality not included intentionally? Thanks!

[schungx]

dir_state: &Rc<DirState>,

Rhai does not support references as parameters. All parameters must be Clone and passed in. Except for the first parameter, which may be &mut.

https://rhai.rs/book/rust/methods.html#admonition-no-support-for-references

Are there any issues with passing a reference to dir_state to my Rust fn (open_helper) from open()?

This is absolutely OK. The Rust compiler does not stop you, so it is OK. Your function parameters are all Clone and passed in, inside you can do whatever you want and no references can ever be passed outside of the function.

Rhai doesn't panic by itself (other than documented) so you can do anything you want with it, as long as it is not unsafe and as long as it compiles.

[gitstashpop]

thanks for the detailed reply!