Issue with JSFuture::from(promise) imported from local source js file

[CallumJHays]

WASM-bindgen-futures aint workin' for me

This repo exemplifies my issue.

Clone & Run it

git clone https://github.com/CallumJHays/wasm-bindgen-futures-test
cd wasm-bindgen-futures-test
yarn # install
rimraf dist pkg && webpack-dev-server --open -d # run

The Code

src/lib.rs:

use wasm_bindgen::prelude::*;
use js_sys::Promise;
use wasm_bindgen_futures::JsFuture;

// This is like the `main` function, except for JavaScript.
#[wasm_bindgen(start)]
pub fn main_js() -> Result<(), JsValue> {
    // This provides better error messages in debug mode.
    // It's disabled in release mode so it doesn't bloat up the file size.
    #[cfg(debug_assertions)]
    console_error_panic_hook::set_once();


    // Your code goes here!
    JsFuture::from(promise_true());

    Ok(())
}

#[wasm_bindgen(module = "/src/promise_true.js")]
extern "C" {
    fn promise_true() -> Promise;
}

src/promise_true.js:

export const promise_true = async () => {
  console.log("promise_true() successfully called from Rust");
  return true;
};

It all compiles fine.

Output

This is the runtime error I experience:

Help? 🐱

[alexcrichton]

Thanks for the report! THe exception here is actually benign, but it's a good one for us to fix and should be fixed in #1649

[CallumJHays]

Awesome! That's good to hear, thanks