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use futures::channel::oneshot;
use futures::executor::{block_on, LocalPool};
use futures::future::{self, FutureExt, LocalFutureObj, TryFutureExt};
use futures::task::LocalSpawn;
use std::cell::{Cell, RefCell};
use std::rc::Rc;
use std::task::Poll;
use std::thread;
struct CountClone(Rc<Cell<i32>>);
impl Clone for CountClone {
fn clone(&self) -> Self {
self.0.set(self.0.get() + 1);
Self(self.0.clone())
}
}
fn send_shared_oneshot_and_wait_on_multiple_threads(threads_number: u32) {
let (tx, rx) = oneshot::channel::<i32>();
let f = rx.shared();
let join_handles = (0..threads_number)
.map(|_| {
let cloned_future = f.clone();
thread::spawn(move || {
assert_eq!(block_on(cloned_future).unwrap(), 6);
})
})
.collect::<Vec<_>>();
tx.send(6).unwrap();
assert_eq!(block_on(f).unwrap(), 6);
for join_handle in join_handles {
join_handle.join().unwrap();
}
}
#[test]
fn one_thread() {
send_shared_oneshot_and_wait_on_multiple_threads(1);
}
#[test]
fn two_threads() {
send_shared_oneshot_and_wait_on_multiple_threads(2);
}
#[test]
fn many_threads() {
send_shared_oneshot_and_wait_on_multiple_threads(1000);
}
#[test]
fn drop_on_one_task_ok() {
let (tx, rx) = oneshot::channel::<u32>();
let f1 = rx.shared();
let f2 = f1.clone();
let (tx2, rx2) = oneshot::channel::<u32>();
let t1 = thread::spawn(|| {
let f = future::try_select(f1.map_err(|_| ()), rx2.map_err(|_| ()));
drop(block_on(f));
});
let (tx3, rx3) = oneshot::channel::<u32>();
let t2 = thread::spawn(|| {
let _ = block_on(f2.map_ok(|x| tx3.send(x).unwrap()).map_err(|_| ()));
});
tx2.send(11).unwrap(); // cancel `f1`
t1.join().unwrap();
tx.send(42).unwrap(); // Should cause `f2` and then `rx3` to get resolved.
let result = block_on(rx3).unwrap();
assert_eq!(result, 42);
t2.join().unwrap();
}
#[test]
fn drop_in_poll() {
let slot1 = Rc::new(RefCell::new(None));
let slot2 = slot1.clone();
let future1 = future::lazy(move |_| {
slot2.replace(None); // Drop future
1
})
.shared();
let future2 = LocalFutureObj::new(Box::new(future1.clone()));
slot1.replace(Some(future2));
assert_eq!(block_on(future1), 1);
}
#[test]
fn peek() {
let mut local_pool = LocalPool::new();
let spawn = &mut local_pool.spawner();
let (tx0, rx0) = oneshot::channel::<i32>();
let f1 = rx0.shared();
let f2 = f1.clone();
// Repeated calls on the original or clone do not change the outcome.
for _ in 0..2 {
assert!(f1.peek().is_none());
assert!(f2.peek().is_none());
}
// Completing the underlying future has no effect, because the value has not been `poll`ed in.
tx0.send(42).unwrap();
for _ in 0..2 {
assert!(f1.peek().is_none());
assert!(f2.peek().is_none());
}
// Once the Shared has been polled, the value is peekable on the clone.
spawn.spawn_local_obj(LocalFutureObj::new(Box::new(f1.map(|_| ())))).unwrap();
local_pool.run();
for _ in 0..2 {
assert_eq!(*f2.peek().unwrap(), Ok(42));
}
}
#[test]
fn downgrade() {
let (tx, rx) = oneshot::channel::<i32>();
let shared = rx.shared();
// Since there are outstanding `Shared`s, we can get a `WeakShared`.
let weak = shared.downgrade().unwrap();
// It should upgrade fine right now.
let mut shared2 = weak.upgrade().unwrap();
tx.send(42).unwrap();
assert_eq!(block_on(shared).unwrap(), 42);
// We should still be able to get a new `WeakShared` and upgrade it
// because `shared2` is outstanding.
assert!(shared2.downgrade().is_some());
assert!(weak.upgrade().is_some());
assert_eq!(block_on(&mut shared2).unwrap(), 42);
// Now that all `Shared`s have been exhausted, we should not be able
// to get a new `WeakShared` or upgrade an existing one.
assert!(weak.upgrade().is_none());
assert!(shared2.downgrade().is_none());
}
#[test]
fn dont_clone_in_single_owner_shared_future() {
let counter = CountClone(Rc::new(Cell::new(0)));
let (tx, rx) = oneshot::channel();
let rx = rx.shared();
tx.send(counter).ok().unwrap();
assert_eq!(block_on(rx).unwrap().0.get(), 0);
}
#[test]
fn dont_do_unnecessary_clones_on_output() {
let counter = CountClone(Rc::new(Cell::new(0)));
let (tx, rx) = oneshot::channel();
let rx = rx.shared();
tx.send(counter).ok().unwrap();
assert_eq!(block_on(rx.clone()).unwrap().0.get(), 1);
assert_eq!(block_on(rx.clone()).unwrap().0.get(), 2);
assert_eq!(block_on(rx).unwrap().0.get(), 2);
}
#[test]
fn shared_future_that_wakes_itself_until_pending_is_returned() {
let proceed = Cell::new(false);
let fut = futures::future::poll_fn(|cx| {
if proceed.get() {
Poll::Ready(())
} else {
cx.waker().wake_by_ref();
Poll::Pending
}
})
.shared();
// The join future can only complete if the second future gets a chance to run after the first
// has returned pending
assert_eq!(block_on(futures::future::join(fut, async { proceed.set(true) })), ((), ()));
}
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