[RFC] Macro for Native Classes

[redfire75369]

[RFC] Macro for Native Classes

[sagudev]

Here is how wasm-bindgen does this: https://rustwasm.github.io/wasm-bindgen/contributing/design/importing-js-struct.html

Although I think it would be better to have struct with specific trait for that. Something like:

#[js_class]
struct Fields {
    s: String,
    num: u64
}

impl CLASS for Fields {
    fn constructor() -> IonResult<Name> {
        Fields {
            s: "",
            num: 0
        }
    }
    fn get(self) -> IonResult<f64> {
        Ok(self.num)
    }
    
    fn set(&mut self, s: String) -> IonResult<()> {
        self.s = s;
        Ok(())
    }
}

impl Fields {
    fn method(self, num: f64) -> IonResult<()> {
        println!("{}", self.s);
        self.num = num;
    }
}

With the goal to keep as much rust syntax as possible.

[Redfire75369]

Hmm, this way of doing it would require impl's for FromJSValConvertible and ToJSValConvertible to be automatically created.
Also, the attributes for functions will most likely still be needed.

[Redfire75369]

I have a slightly improved idea for this:

#[js_class]
mod class {
    #[class]
    #[extends(OtherClass)]
    struct Class {
        #[convert(EnforceRange)]
        field: u8
    }
    
    impl Class {
        #[constructor]
        fn constructor() -> IonResult<Class> {
            Class { field: 644 }
        }
    
        #[js_fn]
        fn add(&self, #[convert(Clamp)] other: u8) -> IonResult<u8> {
            Ok(self.field + other)
        }
        
        #[js_get]
        fn f(&self) -> IonResult<u8> {
            Ok(self.field)
        }
        
        #[js_set]
        fn f(&mut self, field: u8) -> IonResult<()> {
            self.field = u8;
            Ok(())
        }
    }
}

Putting the attribute macro on the mod instead of one the struct is still required as access to the functions by the macro is required.

[sagudev]

Two functions named f?

And also rjs has some interesting ideas: https://github.com/rjs-team/rjs/blob/master/src/main.rs#L323, but I would like to use more rusty syntax.

[Redfire75369]

You can have both a getter and a setter with the same name, you just can't have a property and (getter and/or setter) with the same name.

[sagudev]

You can have both a getter and a setter with the same name, you just can't have a property and (getter and/or setter) with the same name.

The only problem I have is that it does not look rusty enough. I would do with less attr macros, as the whole mod is already transformed using #[js_class].

I especially like how wasm-bindgen handled this:
https://rustwasm.github.io/wasm-bindgen/reference/attributes/on-rust-exports/constructor.html https://rustwasm.github.io/wasm-bindgen/reference/attributes/on-rust-exports/getter-and-setter.html

If we could make js macro compatible with wasm-bindgen we could ideally just replace all wasm-bindgen to js and it would just work.

[Redfire75369]

This is just a draft PR for now but #22 has the syntax and design I've currently settled on, based on both ease of implementation and use.