napi-rs/test_module/src/lib.rs

#[macro_use]
extern crate napi_rs as napi;

extern crate futures;

use napi::{Any, Env, Error, Object, Result, Status, Value, CallContext};
use napi_derive::js_function;

register_module!(test_module, init);

fn init<'env>(
  env: &'env Env,
  exports: &'env mut Value<'env, Object>,
) -> Result<Option<Value<'env, Object>>> {
  exports.set_named_property(
    "testSpawn",
    env.create_function("testSpawn", test_spawn)?,
  )?;
  exports.set_named_property(
    "testThrow",
    env.create_function("testThrow", test_throw)?,
  )?;
  Ok(None)
}

#[js_function]
fn test_spawn<'a>(
  ctx: CallContext<'a>
) -> Result<Value<'a, Object>> {
  use futures::executor::ThreadPool;
  use futures::StreamExt;
  let env = ctx.env;
  let async_context = env.async_init(None, "test_spawn")?;
  let pool = ThreadPool::new().expect("Failed to build pool");
  let (promise, deferred) = env.create_promise()?;
  let (tx, rx) = futures::channel::mpsc::unbounded::<i32>();
  let fut_values = async move {
    let fut_tx_result = async move {
      (0..100).for_each(|v| {
        tx.unbounded_send(v).expect("Failed to send");
      })
    };
    pool.spawn_ok(fut_tx_result);
    let fut_values = rx.map(|v| v * 2).collect::<Vec<i32>>();
    let results = fut_values.await;
    if !cfg!(windows) {
      println!("Collected result lenght {}", results.len());
    };
    async_context.enter(|env| {
      env
        .resolve_deferred(deferred, env.get_undefined().unwrap())
        .unwrap();
    });
  };

  env.create_executor().execute(fut_values);

  Ok(promise)
}

#[js_function]
fn test_throw<'a>(
  _ctx: CallContext<'a>,
) -> Result<Value<'a, Any>> {
  Err(Error::new(Status::GenericFailure))
}