allow to close mpsc sender

actix-utils/src/framed.rs

@@ -274,15 +274,11 @@ where
                 State::Error(_) => {
                     // flush write buffer
                     if !self.framed.is_write_buf_empty() {
-                        match self.framed.flush(cx) {
-                            Poll::Pending => Poll::Pending,
-                            Poll::Ready(Ok(_)) | Poll::Ready(Err(_)) => {
-                                Poll::Ready(Err(self.state.take_error()))
-                            }
+                        if let Poll::Pending = self.framed.flush(cx) {
+                            return Poll::Pending;
                         }
-                    } else {
-                        Poll::Ready(Err(self.state.take_error()))
                     }
+                    Poll::Ready(Err(self.state.take_error()))
                 }
                 State::FlushAndStop => {
                     if !this.framed.is_write_buf_empty() {

actix-utils/src/mpsc.rs

@@ -53,6 +53,14 @@ impl<T> Sender<T> {
         shared.blocked_recv.wake();
         Ok(())
     }
+
+    /// Closes the sender half
+    ///
+    /// This prevents any further messages from being sent on the channel while
+    /// still enabling the receiver to drain messages that are buffered.
+    pub fn close(&mut self) {
+        self.shared.get_mut().has_receiver = false;
+    }
 }
 
 impl<T> Clone for Sender<T> {
@@ -104,6 +112,15 @@ pub struct Receiver<T> {
     shared: Cell<Shared<T>>,
 }
 
+impl<T> Receiver<T> {
+    /// Create Sender
+    pub fn sender(&self) -> Sender<T> {
+        Sender {
+            shared: self.shared.clone(),
+        }
+    }
+}
+
 impl<T> Unpin for Receiver<T> {}
 
 impl<T> Stream for Receiver<T> {
@@ -192,5 +209,11 @@ mod tests {
         tx.send("test").unwrap();
         drop(rx);
         assert!(tx.send("test").is_err());
+
+        let (mut tx, _) = channel();
+        let tx2 = tx.clone();
+        tx.close();
+        assert!(tx.send("test").is_err());
+        assert!(tx2.send("test").is_err());
     }
 }