Tokio 1.0 Signal no longer implements Stream

[djmarcin]

In tokio 0.3.6 tokio::signal::unix::Signal implemented Stream, but in 1.0.2 it does not. This means it can no longer be passed to things like stream::select_all.

How should such code be migrated? Is there a way to wrap a Signal in a Stream?

[Darksonn]

You can turn it into a Stream using the async-stream crate.

let stream = async_stream::stream! {
    loop {
        signal.recv().await;
        yield ();
    }
};

[djmarcin]

It looks like other things also don't implement stream anymore, like tokio::sync::mpsc::Receiver. Is the suggestion that all lines like:

while let Some(element) = rx.next().await {
  ...
}

get converted to:

let rx_stream = async_stream::stream! {
    loop {
        yield rx.recv().await;
    }
};
while let Some(element) = rx_stream.next().await {
  ...
}

[Darksonn]

In some cases you can use tokio_stream::wrappers. Though in your example, you would convert it to calling .recv().

[Darksonn]

If you did want to use async-stream for mpsc, it would look like this:

let stream = async_stream::stream! {
    while let Some(item) = rx.recv().await {
        yield item;
    }
};

unlike your solution, this handles the channle being closed correctly.

[Roguelazer]

Are there any plans to add something to tokio_stream::wrappers that implements Stream for Signal? Would such an addition be an acceptable PR? Using async_stream is problematic because the macro interferes with tokio::select! (and generally complicates code quite a lot).

[Darksonn]

We already have #3383 open, which is necessary for writing the wrapper. If you are just using it in select!, why not just call .recv() on the Signal?