1 files changed, 117 insertions, 0 deletions
diff --git a/tests/eager_drop.rs b/tests/eager_drop.rs
new file mode 100644
index 0000000..674e401
--- /dev/null
+++ b/tests/eager_drop.rs
@@ -0,0 +1,117 @@
+use futures::channel::oneshot;
+use futures::future::{self, Future, FutureExt, TryFutureExt};
+use futures::task::{Context, Poll};
+use futures_test::future::FutureTestExt;
+use pin_utils::unsafe_pinned;
+use std::pin::Pin;
+use std::sync::mpsc;
+
+#[test]
+fn map_ok() {
+    // The closure given to `map_ok` should have been dropped by the time `map`
+    // runs.
+    let (tx1, rx1) = mpsc::channel::<()>();
+    let (tx2, rx2) = mpsc::channel::<()>();
+
+    future::ready::<Result<i32, i32>>(Err(1))
+        .map_ok(move |_| { let _tx1 = tx1; panic!("should not run"); })
+        .map(move |_| {
+            assert!(rx1.recv().is_err());
+            tx2.send(()).unwrap()
+        })
+        .run_in_background();
+
+    rx2.recv().unwrap();
+}
+
+#[test]
+fn map_err() {
+    // The closure given to `map_err` should have been dropped by the time `map`
+    // runs.
+    let (tx1, rx1) = mpsc::channel::<()>();
+    let (tx2, rx2) = mpsc::channel::<()>();
+
+    future::ready::<Result<i32, i32>>(Ok(1))
+        .map_err(move |_| { let _tx1 = tx1; panic!("should not run"); })
+        .map(move |_| {
+            assert!(rx1.recv().is_err());
+            tx2.send(()).unwrap()
+        })
+        .run_in_background();
+
+    rx2.recv().unwrap();
+}
+
+struct FutureData<F, T> {
+    _data: T,
+    future: F,
+}
+
+impl<F, T> FutureData<F, T> {
+    unsafe_pinned!(future: F);
+}
+
+impl<F: Future, T: Send + 'static> Future for FutureData<F, T> {
+    type Output = F::Output;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<F::Output> {
+        self.future().poll(cx)
+    }
+}
+
+#[test]
+fn then_drops_eagerly() {
+    let (tx0, rx0) = oneshot::channel::<()>();
+    let (tx1, rx1) = mpsc::channel::<()>();
+    let (tx2, rx2) = mpsc::channel::<()>();
+
+    FutureData { _data: tx1, future: rx0.unwrap_or_else(|_| { panic!() }) }
+        .then(move |_| {
+            assert!(rx1.recv().is_err()); // tx1 should have been dropped
+            tx2.send(()).unwrap();
+            future::ready(())
+        })
+        .run_in_background();
+
+    assert_eq!(Err(mpsc::TryRecvError::Empty), rx2.try_recv());
+    tx0.send(()).unwrap();
+    rx2.recv().unwrap();
+}
+
+#[test]
+fn and_then_drops_eagerly() {
+    let (tx0, rx0) = oneshot::channel::<Result<(), ()>>();
+    let (tx1, rx1) = mpsc::channel::<()>();
+    let (tx2, rx2) = mpsc::channel::<()>();
+
+    FutureData { _data: tx1, future: rx0.unwrap_or_else(|_| { panic!() }) }
+        .and_then(move |_| {
+            assert!(rx1.recv().is_err()); // tx1 should have been dropped
+            tx2.send(()).unwrap();
+            future::ready(Ok(()))
+        })
+        .run_in_background();
+
+    assert_eq!(Err(mpsc::TryRecvError::Empty), rx2.try_recv());
+    tx0.send(Ok(())).unwrap();
+    rx2.recv().unwrap();
+}
+
+#[test]
+fn or_else_drops_eagerly() {
+    let (tx0, rx0) = oneshot::channel::<Result<(), ()>>();
+    let (tx1, rx1) = mpsc::channel::<()>();
+    let (tx2, rx2) = mpsc::channel::<()>();
+
+    FutureData { _data: tx1, future: rx0.unwrap_or_else(|_| { panic!() }) }
+        .or_else(move |_| {
+            assert!(rx1.recv().is_err()); // tx1 should have been dropped
+            tx2.send(()).unwrap();
+            future::ready::<Result<(), ()>>(Ok(()))
+        })
+        .run_in_background();
+
+    assert_eq!(Err(mpsc::TryRecvError::Empty), rx2.try_recv());
+    tx0.send(Err(())).unwrap();
+    rx2.recv().unwrap();
+}