stream: add `empty()` and `pending()` (#2092)

`stream::empty()` is the asynchronous equivalent to
`std::iter::empty()`. `pending()` provides a stream that never becomes
ready.

1 files changed, 14 insertions, 0 deletions

diff --git a/tokio/tests/stream_pending.rs b/tokio/tests/stream_pending.rs
new file mode 100644
index 00000000..f4d3080d
--- /dev/null
+++ b/tokio/tests/stream_pending.rs
@@ -0,0 +1,14 @@
+use tokio::stream::{self, Stream, StreamExt};
+use tokio_test::{assert_pending, task};
+
+#[tokio::test]
+async fn basic_usage() {
+    let mut stream = stream::pending::<i32>();
+
+    for _ in 0..2 {
+        assert_eq!(stream.size_hint(), (0, None));
+
+        let mut next = task::spawn(async { stream.next().await });
+        assert_pending!(next.poll());
+    }
+}