Macro all_some

macro_rules! all_some {
    ($fut0:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr, $fut2:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr, $fut2:expr, $fut3:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr, $fut2:expr, $fut3:expr, $fut4:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr, $fut2:expr, $fut3:expr, $fut4:expr, $fut5:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr, $fut2:expr, $fut3:expr, $fut4:expr, $fut5:expr, $fut6:expr $(,)?) => { ... };
    ($fut0:expr, $fut1:expr, $fut2:expr, $fut3:expr, $fut4:expr, $fut5:expr, $fut6:expr, $fut7:expr $(,)?) => { ... };
    ($($fut:expr),+ $(,)?) => { ... };
}

A future that is ready when all futures are ready with Some(T) or when any is future ready with None.

The macro input is comma separated list of future expressions, the futures must all have the Option<T> output type, but each can have a different T. The macro output is a future that when “.awaited” produces Some<(T0, T1, ..)> if all futures where Some(T) or None if any of the futures where None.

At least one input future is required and any number of futures is accepted. For more than eight futures a proc-macro is used which may cause code auto-complete to stop working in some IDEs.

After one future is ready and None the other futures are not polled again and are dropped. After a future is ready it is also not polled again and dropped.

Each input must implement IntoFuture with the same Output type. Note that each input must be known at compile time, use the all_some async function to await on all futures in a dynamic list of futures.

Examples

Await for the first of three futures to complete with Some:

use zng_task as task;
let r = task::all_some!(
    task::run(async { Some('a') }),
    task::wait(|| Some('b')),
    async { Some('c') }
).await;

assert_eq!(Some(('a', 'b', 'c')), r);

Completes with None if any future completes with None:

let r = task::all_some!(
    task::run(async { Some('a') }),
    task::wait(|| None::<char>),
    async { Some('b') }
).await;

assert_eq!(None, r);