Unblock DataCell::get*() as soon as the cell is closed

src/cell/datacell.rs

@@ -94,10 +94,10 @@ where
     /// Retrieves the data from the cell
     pub fn get(&self) -> Result<P> {
         let mut value = self.inner.value.lock();
-        if value.closed {
-            return Err(Error::ChannelClosed);
-        }
         loop {
+            if value.closed {
+                return Err(Error::ChannelClosed);
+            }
             if let Some(current) = value.current.take() {
                 return Ok(current);
             }
@@ -109,10 +109,10 @@ where
     /// Retrieves the data from the cell with the given timeout
     pub fn get_timeout(&self, timeout: Duration) -> Result<P> {
         let mut value = self.inner.value.lock();
-        if value.closed {
-            return Err(Error::ChannelClosed);
-        }
         loop {
+            if value.closed {
+                return Err(Error::ChannelClosed);
+            }
             if let Some(current) = value.current.take() {
                 return Ok(current);
             }
@@ -180,6 +180,19 @@ mod test {
         handle.join().unwrap();
     }
 
+    #[test]
+    fn test_datacell_close_empty() {
+        let cell: DataCell<u8> = DataCell::new();
+        let cell2 = cell.clone();
+        let handle = thread::spawn(
+            move || cell2.get(), // blocks until the cell is closed
+        );
+        thread::sleep(Duration::from_millis(100));
+        cell.close();
+        assert!(matches!(handle.join().unwrap(), Err(Error::ChannelClosed)));
+        assert!(matches!(cell.get().unwrap_err(), Error::ChannelClosed));
+    }
+
     #[test]
     fn test_datacell_try_get() {
         let cell: DataCell<_> = DataCell::new();