Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/io_copy_bidirectional.rs

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+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support bind()
+
+use std::time::Duration;
+use tokio::io::{self, copy_bidirectional, AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpStream;
+use tokio::task::JoinHandle;
+
+async fn make_socketpair() -> (TcpStream, TcpStream) {
+    let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr = listener.local_addr().unwrap();
+    let connector = TcpStream::connect(addr);
+    let acceptor = listener.accept();
+
+    let (c1, c2) = tokio::join!(connector, acceptor);
+
+    (c1.unwrap(), c2.unwrap().0)
+}
+
+async fn block_write(s: &mut TcpStream) -> usize {
+    static BUF: [u8; 2048] = [0; 2048];
+
+    let mut copied = 0;
+    loop {
+        tokio::select! {
+            result = s.write(&BUF) => {
+                copied += result.expect("write error")
+            },
+            _ = tokio::time::sleep(Duration::from_millis(10)) => {
+                break;
+            }
+        }
+    }
+
+    copied
+}
+
+async fn symmetric<F, Fut>(mut cb: F)
+where
+    F: FnMut(JoinHandle<io::Result<(u64, u64)>>, TcpStream, TcpStream) -> Fut,
+    Fut: std::future::Future<Output = ()>,
+{
+    // We run the test twice, with streams passed to copy_bidirectional in
+    // different orders, in order to ensure that the two arguments are
+    // interchangeable.
+
+    let (a, mut a1) = make_socketpair().await;
+    let (b, mut b1) = make_socketpair().await;
+
+    let handle = tokio::spawn(async move { copy_bidirectional(&mut a1, &mut b1).await });
+    cb(handle, a, b).await;
+
+    let (a, mut a1) = make_socketpair().await;
+    let (b, mut b1) = make_socketpair().await;
+
+    let handle = tokio::spawn(async move { copy_bidirectional(&mut b1, &mut a1).await });
+
+    cb(handle, b, a).await;
+}
+
+#[tokio::test]
+async fn test_basic_transfer() {
+    symmetric(|_handle, mut a, mut b| async move {
+        a.write_all(b"test").await.unwrap();
+        let mut tmp = [0; 4];
+        b.read_exact(&mut tmp).await.unwrap();
+        assert_eq!(&tmp[..], b"test");
+    })
+    .await
+}
+
+#[tokio::test]
+async fn test_transfer_after_close() {
+    symmetric(|handle, mut a, mut b| async move {
+        AsyncWriteExt::shutdown(&mut a).await.unwrap();
+        b.read_to_end(&mut Vec::new()).await.unwrap();
+
+        b.write_all(b"quux").await.unwrap();
+        let mut tmp = [0; 4];
+        a.read_exact(&mut tmp).await.unwrap();
+        assert_eq!(&tmp[..], b"quux");
+
+        // Once both are closed, we should have our handle back
+        drop(b);
+
+        assert_eq!(handle.await.unwrap().unwrap(), (0, 4));
+    })
+    .await
+}
+
+#[tokio::test]
+async fn blocking_one_side_does_not_block_other() {
+    symmetric(|handle, mut a, mut b| async move {
+        block_write(&mut a).await;
+
+        b.write_all(b"quux").await.unwrap();
+        let mut tmp = [0; 4];
+        a.read_exact(&mut tmp).await.unwrap();
+        assert_eq!(&tmp[..], b"quux");
+
+        AsyncWriteExt::shutdown(&mut a).await.unwrap();
+
+        let mut buf = Vec::new();
+        b.read_to_end(&mut buf).await.unwrap();
+
+        drop(b);
+
+        assert_eq!(handle.await.unwrap().unwrap(), (buf.len() as u64, 4));
+    })
+    .await
+}
+
+#[tokio::test]
+async fn immediate_exit_on_write_error() {
+    let payload = b"here, take this";
+    let error = || io::Error::new(io::ErrorKind::Other, "no thanks!");
+
+    let mut a = tokio_test::io::Builder::new()
+        .read(payload)
+        .write_error(error())
+        .build();
+
+    let mut b = tokio_test::io::Builder::new()
+        .read(payload)
+        .write_error(error())
+        .build();
+
+    assert!(copy_bidirectional(&mut a, &mut b).await.is_err());
+}
+
+#[tokio::test]
+async fn immediate_exit_on_read_error() {
+    let error = || io::Error::new(io::ErrorKind::Other, "got nothing!");
+
+    let mut a = tokio_test::io::Builder::new().read_error(error()).build();
+
+    let mut b = tokio_test::io::Builder::new().read_error(error()).build();
+
+    assert!(copy_bidirectional(&mut a, &mut b).await.is_err());
+}