Tokio: Can't install tokio async await ( LocalWaker )

[victordetarragon]

Version

Following this page and from a new cargo init :
https://github.com/tokio-rs/tokio/tree/master/tokio-async-await

testing_tokio v0.1.0 (/root/testing_tokio)
└── tokio v0.1.15
├── tokio-async-await v0.1.5
│ └── tokio-io v0.1.11
├── tokio-codec v0.1.1
│ └── tokio-io v0.1.11 ()
├── tokio-current-thread v0.1.4
│ └── tokio-executor v0.1.6
├── tokio-executor v0.1.6 ()
├── tokio-fs v0.1.5
│ ├── tokio-io v0.1.11 ()
│ └── tokio-threadpool v0.1.11
│ └── tokio-executor v0.1.6 ()
│ └── tokio-io v0.1.11 ()
├── tokio-io v0.1.11 ()
├── tokio-reactor v0.1.8
│ ├── tokio-executor v0.1.6 ()
│ └── tokio-io v0.1.11 ()
├── tokio-sync v0.1.1
├── tokio-tcp v0.1.3
│ ├── tokio-io v0.1.11 ()
│ └── tokio-reactor v0.1.8 ()
├── tokio-threadpool v0.1.11 ()
├── tokio-timer v0.2.10
│ └── tokio-executor v0.1.6 ()
├── tokio-udp v0.1.3
│ ├── tokio-codec v0.1.1 ()
│ ├── tokio-io v0.1.11 ()
│ └── tokio-reactor v0.1.8 ()
└── tokio-uds v0.2.5
├── tokio-codec v0.1.1 ()
├── tokio-io v0.1.11 ()
└── tokio-reactor v0.1.8 ()

Platform

Linux 4.13.0-kali1-amd64 #1 SMP Debian 4.13.10-1kali2 (2017-11-08) x86_64 GNU/Linux

Description

I am simply following the exemple. Nothing more. And I have the following issue during the build :

Compiling tokio-async-await v0.1.5 error[E0432]: unresolved importstd::task::LocalWaker --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-async-await-0.1.5/src/compat/forward.rs:7:17 | 7 | use std::task::{LocalWaker, Poll as StdPoll}; | ^^^^^^^^^^ noLocalWakerintask
Seems to be relate with Future issue about LocalWaker ...
Thank you.

[chocol4te]

LocalWaker was removed in PR https://github.com/rust-lang/rust/pull/57992, as discussed in https://github.com/rust-lang/rfcs/pull/2592.

[victordetarragon]

Exact so I presume Async Await is dead for the moment ? Do you have a work around ?

[chocol4te]

The workaround will be to use an older nightly. We'll need to discuss with tokio-rs members as to what to do (reimplement with the newer API (https://github.com/aturon/rfcs/blob/future/text/0000-futures.md#rationale-drawbacks-and-alternatives-to-the-wakeup-design-waker?), or some other fix).

[dvc94ch]

Using an older nightly breaks other crates. As a work around you can do this:

[dependencies]
futures-preview = { version = "0.3.0-alpha.13", features = ["compat"] }
tokio = "*"

#![features(async_await, await_macro, futures_api)]
use futures::future::FutureObj;
use futures::prelude::*;

fn main() {
  tokio::run(FutureObj::new(Box::new(async move {
    println!("running");
    tokio::spawn(FutureObj::new(Box::new(async move {
       println!("spawned");
       Ok(())
    })).compat());
    Ok(())
  })).compat());
}

[victordetarragon]

Thank you David for the work around. The issue is I can't even build. Do you have a specific .toml according to it ?

@taiki-e seems to be the Real MVP here. I hope your PR will be accepted !

Thanks everyone for your help in this issue.

[dvc94ch]

@victordetarragon tokio-async-await provides a tokio::run_async and tokio::spawn_async which take v3 Futures. By using the compat traits from futures-preview you can roll your own until it builds again. I updated the comment with a Cargo.toml and verified that the code example runs as is.

If you are returning futures from trait functions you need to wrap them in FutureObj<Box<F: Future>> anyway, so you most likely already have FutureObj<Box<F: Future>> anyway. All that is missing is calling compat()

[carllerche]

Pushed out a release w/ the fix. Thanks @taiki-e