Flushing stdout with a binary protocol does not work

[jothan]

I'm having trouble with a binary protocol that does not use newlines as line separators. stdout seems to flush immediately only when there is a newline in the output.

I have included a snippet to reproduce this issue.

Flushing the underlying std stream works, but only when the async stream was flushed first.

stderr has the expected behaviour of flushing immediately correctly.

Version

0.2.0-alpha.4

Platform

Linux 4.19.0-5-amd64 #1 SMP Debian 4.19.37-5+deb10u2 (2019-08-08) x86_64 GNU/Linux

Subcrates

Description

use std::io::Write;
use std::time::Duration;

use tokio::prelude::*;
use tokio::timer::delay;
use tokio::io::{stdout};

async fn works() -> Result<(), Box<dyn std::error::Error>> {
    let mut output = stdout();
    output.write_all(b"hello").await?;
    output.flush().await?;
    std::io::stdout().flush()?;

    Ok(())
}

async fn should_work() -> Result<(), Box<dyn std::error::Error>> {
    let mut output = stdout();
    output.write_all(b"hello").await?;
    output.flush().await?;

    Ok(())
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Both calls should output "hello" without a newline immediately
    //works().await?;
    should_work().await?;

    let when = tokio::clock::now() + Duration::from_secs(5);
    delay(when).await;
    
    Ok(())
}

[jothan]

Adding inner.flush() in Blocking::poll_flush() seems to fix the behaviour. I am not sure where to call the lower layer flush.

[carllerche]

Fixed by #1528