future_try_join_all.rs

use futures::executor::block_on;
use futures::future::{err, ok, try_join_all, Future, TryJoinAll};
use futures::pin_mut;
use std::fmt::Debug;

#[track_caller]
fn assert_done<T>(actual_fut: impl Future<Output = T>, expected: T)
where
    T: PartialEq + Debug,
{
    pin_mut!(actual_fut);
    let output = block_on(actual_fut);
    assert_eq!(output, expected);
}

#[test]
fn collect_collects() {
    assert_done(try_join_all(vec![ok(1), ok(2)]), Ok::<_, usize>(vec![1, 2]));
    assert_done(try_join_all(vec![ok(1), err(2)]), Err(2));
    assert_done(try_join_all(vec![ok(1)]), Ok::<_, usize>(vec![1]));
    // REVIEW: should this be implemented?
    // assert_done(try_join_all(Vec::<i32>::new()), Ok(vec![]));

    // TODO: needs more tests
}

#[test]
fn try_join_all_iter_lifetime() {
    // In futures-rs version 0.1, this function would fail to typecheck due to an overly
    // conservative type parameterization of `TryJoinAll`.
    fn sizes(bufs: Vec<&[u8]>) -> impl Future<Output = Result<Vec<usize>, ()>> {
        let iter = bufs.into_iter().map(|b| ok::<usize, ()>(b.len()));
        try_join_all(iter)
    }

    assert_done(sizes(vec![&[1, 2, 3], &[], &[0]]), Ok(vec![3_usize, 0, 1]));
}

#[test]
fn try_join_all_from_iter() {
    assert_done(
        vec![ok(1), ok(2)].into_iter().collect::<TryJoinAll<_>>(),
        Ok::<_, usize>(vec![1, 2]),
    )
}