Rust: How to join_all a dynamic number of async

dynamic-join-all-for-async.rs

/**

The macro `join!` cannot be used in this context
because we need to add any number of asyncs,
not known at compile time.

Here we provide a list: Vec<FutureWrapper>,
and this list is used to call the function `join_all`.

Playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=eb3732a22a43ada448e35eebbd1e188a

*/
    
extern crate futures; // v0.3.30

use std::{
    task::{Context, Poll},
    future::Future,
    pin::Pin
};

struct FutureWrapper {
    future: Pin<Box<dyn Future<Output = ()>>>,
}

impl FutureWrapper {
    fn new<F: Future<Output = ()> + 'static>(f: F) -> Self {
        FutureWrapper {
            future: Box::pin(f),
        }
    }
}

impl Future for FutureWrapper {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        self.future.as_mut().poll(cx)
    }
}

async fn f1() {
    println!("f1");
}

async fn f2() {
    println!("f2");
}

async fn all() {
    let list = vec![
        FutureWrapper::new(f1()),
        FutureWrapper::new(f2()),
    ];

    futures::future::join_all(list).await;
}

fn main() {
    futures::executor::block_on(all());
}