chore: checkpoint before Python removal

vendor/tokio-stream/tests/mpsc_unbounded_stream.rs

@@ -0,0 +1,63 @@
+use futures::{Stream, StreamExt};
+use tokio::sync::mpsc;
+use tokio_stream::wrappers::UnboundedReceiverStream;
+
+#[tokio::test]
+async fn size_hint_stream_open() {
+    let (tx, rx) = mpsc::unbounded_channel();
+
+    tx.send(1).unwrap();
+    tx.send(2).unwrap();
+
+    let mut stream = UnboundedReceiverStream::new(rx);
+
+    assert_eq!(stream.size_hint(), (2, None));
+    stream.next().await;
+    assert_eq!(stream.size_hint(), (1, None));
+    stream.next().await;
+    assert_eq!(stream.size_hint(), (0, None));
+}
+
+#[tokio::test]
+async fn size_hint_stream_closed() {
+    let (tx, rx) = mpsc::unbounded_channel();
+
+    tx.send(1).unwrap();
+    tx.send(2).unwrap();
+
+    let mut stream = UnboundedReceiverStream::new(rx);
+    stream.close();
+
+    assert_eq!(stream.size_hint(), (2, Some(2)));
+    stream.next().await;
+    assert_eq!(stream.size_hint(), (1, Some(1)));
+    stream.next().await;
+    assert_eq!(stream.size_hint(), (0, Some(0)));
+}
+
+#[tokio::test]
+async fn size_hint_sender_dropped() {
+    let (tx, rx) = mpsc::unbounded_channel();
+
+    tx.send(1).unwrap();
+    tx.send(2).unwrap();
+
+    let mut stream = UnboundedReceiverStream::new(rx);
+    drop(tx);
+
+    assert_eq!(stream.size_hint(), (2, Some(2)));
+    stream.next().await;
+    assert_eq!(stream.size_hint(), (1, Some(1)));
+    stream.next().await;
+    assert_eq!(stream.size_hint(), (0, Some(0)));
+}
+
+#[test]
+fn size_hint_stream_instantly_closed() {
+    let (_tx, rx) = mpsc::unbounded_channel::<i32>();
+
+    let mut stream = UnboundedReceiverStream::new(rx);
+    stream.close();
+
+    assert_eq!(stream.size_hint(), (0, Some(0)));
+}