Add tests for AsyncBufRead::read_line and AsyncBufReadExt::lines …

…corner cases.

futures/tests/io_lines.rs

@@ -1,6 +1,6 @@
 use futures::executor::block_on;
 use futures::future::{Future, FutureExt};
-use futures::io::{AsyncBufReadExt, Cursor};
+use futures::io::{AsyncBufReadExt, AsyncRead, Cursor};
 use futures::stream::{self, StreamExt, TryStreamExt};
 use futures::task::Poll;
 use futures_test::io::AsyncReadTestExt;
@@ -27,6 +27,24 @@ macro_rules! run_next {
     };
 }
 
+struct IOErrorRead(bool);
+
+impl AsyncRead for IOErrorRead {
+    fn poll_read(
+        mut self: std::pin::Pin<&mut Self>,
+        _cx: &mut std::task::Context<'_>,
+        b: &mut [u8],
+    ) -> Poll<std::io::Result<usize>> {
+        if self.0 {
+            Poll::Ready(Err(std::io::ErrorKind::InvalidInput.into()))
+        } else {
+            self.0 = true;
+            b.fill(b'x');
+            Ok(b.len()).into()
+        }
+    }
+}
+
 #[test]
 fn lines() {
     let buf = Cursor::new(&b"12\r"[..]);
@@ -58,3 +76,9 @@ fn maybe_pending() {
     assert_eq!(run_next!(s), "".to_string());
     assert!(run(s.next()).is_none());
 }
+
+#[test]
+fn issue2862() {
+    let mut lines = futures::io::BufReader::new(IOErrorRead(false)).lines();
+    assert!(block_on(lines.next()).unwrap().is_err())
+}

futures/tests/io_read_line.rs

@@ -3,6 +3,7 @@ use futures::future::{Future, FutureExt};
 use futures::io::{AsyncBufReadExt, Cursor};
 use futures::stream::{self, StreamExt, TryStreamExt};
 use futures::task::Poll;
+use futures::AsyncRead;
 use futures_test::io::AsyncReadTestExt;
 use futures_test::task::noop_context;
 
@@ -15,6 +16,24 @@ fn run<F: Future + Unpin>(mut f: F) -> F::Output {
     }
 }
 
+struct IOErrorRead(bool);
+
+impl AsyncRead for IOErrorRead {
+    fn poll_read(
+        mut self: std::pin::Pin<&mut Self>,
+        _cx: &mut std::task::Context<'_>,
+        b: &mut [u8],
+    ) -> Poll<std::io::Result<usize>> {
+        if self.0 {
+            Poll::Ready(Err(std::io::ErrorKind::InvalidInput.into()))
+        } else {
+            self.0 = true;
+            b.fill(b'x');
+            Ok(b.len()).into()
+        }
+    }
+}
+
 #[test]
 fn read_line() {
     let mut buf = Cursor::new(b"12");
@@ -34,6 +53,30 @@ fn read_line() {
     assert_eq!(v, "");
 }
 
+#[test]
+fn read_line_drop() {
+    // string contents should be preserved if the future is dropped
+    let mut buf = Cursor::new(b"12\n\n");
+    let mut v = String::from("abc");
+    drop(buf.read_line(&mut v));
+    assert_eq!(v, "abc");
+}
+
+#[test]
+fn read_line_io_error() {
+    let mut r = futures::io::BufReader::new(IOErrorRead(false));
+    let _ = block_on(r.read_line(&mut String::new()));
+}
+
+#[test]
+fn read_line_utf8_error() {
+    let mut buf = Cursor::new(b"12\xFF\n\n");
+    let mut v = String::from("abc");
+    let res = block_on(buf.read_line(&mut v));
+    assert_eq!(res.unwrap_err().kind(), std::io::ErrorKind::InvalidData);
+    assert_eq!(v, "abc");
+}
+
 #[test]
 fn maybe_pending() {
     let mut buf = b"12".interleave_pending();