How to handle 3rd party types not implementing IntoWasmAbi and FromWasmAbi?

[ChristianIvicevic]

For some precise computations I am using rust_decimal::Decimal in my structs as follows:

#[wasm_bindgen]
pub struct Precise {
    pub value: Decimal,
}

Of couse this doesn't compile as Decimal doesn't implement IntoWasmAbi and FromWasmAbi. Even manually attempting to implement them would not work since it's a type from a foreign crate. One workaround is a mapped struct that can be serialized across the border like this:

pub struct Precise {
    pub value: Decimal,
}

#[wasm_bindgen]
pub struct PreciseJs {
    pub value: f64,
}

But this introduces a lot of cognitive overhead doubling the amount of types just to be able to pass around data back and forth. Is there an idiomatic approach to that?

[daxpedda]

You could ask rust_decimal to implement wasm-bindgen on their types.

This generally seems like a similar problem to implementing Serde on foreign types, but wasm-bindgen doesn't have any nice ways to work around that AFAIK.

[ChristianIvicevic]

Do you know of any existing and possible small implementation in other crates? If it isn't too difficult I would consider contributing myself, but would need guidance to understand how to implement support for wasm-bindgen in general.

[daxpedda]

Do you know of any existing and possible small implementation in other crates?

Unfortunately I am not.

If it isn't too difficult I would consider contributing myself, but would need guidance to understand how to implement support for wasm-bindgen in general.

I honestly have no experience exporting Rust to JS, only the other way around, but generally speaking you only have to add #[wasm_bindgen] at the top as long as all types are supported.
Additionally, there is an issue with exporting symbols from dependencies when the root package is a library itself, so using #[wasm_bindgen] in libraries will only work if the root package is a "binary". I didn't look too deep into this, but it seems to be a Rust issue to me.

[RedstoneWizard08]

What I did for my project was just forking the crate and adding it to the workspace, then manually patching it myself. I did this for anyhow, and it worked perfectly.

[ChristianIvicevic]

Yeah I am maintaining a fork for myself and have attached #[wasm_bindgen] to the relevant struct and methods. Even opened a PR but it seems the original maintainer isn't as active. Having to maintain a fork and possibly pull in upstream changes into it is always really annoying, but there isn't really any other way anyways.