Toot

Written by BB_C@programming.dev on 2024-09-06 at 00:59

but futures only execute when polled.

The most interesting part here is the polling only has to take place on the scope itself. That was actually what I wanted to check, but got distracted because all spawns are awaited in the scope in moro’s README example.

tokio::time::sleep(std::time::Duration::from_millis(1)).await

}

async fn _main() {

let result_fut = moro::async_scope!(|scope| {

    dbg!("d1");

    scope.spawn(async { 

        dbg!("f1a");

        slp().await;

        slp().await;

        slp().await;

        dbg!("f1b");

    });

    dbg!("d2"); // 11

    scope.spawn(async {

        dbg!("f2a");

        slp().await;

        slp().await;

        dbg!("f2b");

    });

    dbg!("d3"); // 14

    scope.spawn(async {

        dbg!("f3a");

        slp().await;

        dbg!("f3b");

    });

    dbg!("d4");

    async { dbg!("b1"); } // never executes

});

slp().await;

dbg!("o1");

let _ = result_fut.await;

}

fn main() {

let rt = tokio::runtime::Builder::new_multi_thread()

    .enable_all()

    .build()

    .unwrap();

rt.block_on(_main())

}

[src/main.rs:7:9] "d1" = "d1"

[src/main.rs:15:9] "d2" = "d2"

[src/main.rs:22:9] "d3" = "d3"

[src/main.rs:28:9] "d4" = "d4"

[src/main.rs:9:13] "f1a" = "f1a"

[src/main.rs:17:13] "f2a" = "f2a"

[src/main.rs:24:13] "f3a" = "f3a"

[src/main.rs:26:13] "f3b" = "f3b"

[src/main.rs:20:13] "f2b" = "f2b"

[src/main.rs:13:13] "f1b" = "f1b"

The non-awaited jobs are run concurrently as the moro docs say. But what if we immediately await f2?

[src/main.rs:7:9] "d1" = "d1"

[src/main.rs:15:9] "d2" = "d2"

[src/main.rs:9:13] "f1a" = "f1a"

[src/main.rs:17:13] "f2a" = "f2a"

[src/main.rs:20:13] "f2b" = "f2b"

[src/main.rs:22:9] "d3" = "d3"

[src/main.rs:28:9] "d4" = "d4"

[src/main.rs:24:13] "f3a" = "f3a"

[src/main.rs:13:13] "f1b" = "f1b"

[src/main.rs:26:13] "f3b" = "f3b"

f1 and f2 are run concurrently, f3 is run after f2 finishes, but doesn’t have to wait for f1 to finish, which is maybe obvious, but… (see below).

So two things here:

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