Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/io_write_all_buf.rs

@@ -0,0 +1,96 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use tokio::io::{AsyncWrite, AsyncWriteExt};
+use tokio_test::{assert_err, assert_ok};
+
+use bytes::{Buf, Bytes, BytesMut};
+use std::cmp;
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+#[tokio::test]
+async fn write_all_buf() {
+    struct Wr {
+        buf: BytesMut,
+        cnt: usize,
+    }
+
+    impl AsyncWrite for Wr {
+        fn poll_write(
+            mut self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+            buf: &[u8],
+        ) -> Poll<io::Result<usize>> {
+            let n = cmp::min(4, buf.len());
+            dbg!(buf);
+            let buf = &buf[0..n];
+
+            self.cnt += 1;
+            self.buf.extend(buf);
+            Ok(buf.len()).into()
+        }
+
+        fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+            Ok(()).into()
+        }
+
+        fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+            Ok(()).into()
+        }
+    }
+
+    let mut wr = Wr {
+        buf: BytesMut::with_capacity(64),
+        cnt: 0,
+    };
+
+    let mut buf = Bytes::from_static(b"hello").chain(Bytes::from_static(b"world"));
+
+    assert_ok!(wr.write_all_buf(&mut buf).await);
+    assert_eq!(wr.buf, b"helloworld"[..]);
+    // expect 4 writes, [hell],[o],[worl],[d]
+    assert_eq!(wr.cnt, 4);
+    assert!(!buf.has_remaining());
+}
+
+#[tokio::test]
+async fn write_buf_err() {
+    /// Error out after writing the first 4 bytes
+    struct Wr {
+        cnt: usize,
+    }
+
+    impl AsyncWrite for Wr {
+        fn poll_write(
+            mut self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+            _buf: &[u8],
+        ) -> Poll<io::Result<usize>> {
+            self.cnt += 1;
+            if self.cnt == 2 {
+                return Poll::Ready(Err(io::Error::new(io::ErrorKind::Other, "whoops")));
+            }
+            Poll::Ready(Ok(4))
+        }
+
+        fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+            Ok(()).into()
+        }
+
+        fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+            Ok(()).into()
+        }
+    }
+
+    let mut wr = Wr { cnt: 0 };
+
+    let mut buf = Bytes::from_static(b"hello").chain(Bytes::from_static(b"world"));
+
+    assert_err!(wr.write_all_buf(&mut buf).await);
+    assert_eq!(
+        buf.copy_to_bytes(buf.remaining()),
+        Bytes::from_static(b"oworld")
+    );
+}