Check if Task(Future) is canceled.

rclpy/rclpy/executors.py

@@ -321,14 +321,24 @@ def spin_until_future_complete(
         future.add_done_callback(lambda x: self.wake())
 
         if timeout_sec is None or timeout_sec < 0:
-            while self._context.ok() and not future.done() and not self._is_shutdown:
+            while (
+                self._context.ok() and
+                not future.done() and
+                not future.cancelled()
+                and not self._is_shutdown
+            ):
                 self._spin_once_until_future_complete(future, timeout_sec)
         else:
             start = time.monotonic()
             end = start + timeout_sec
             timeout_left = TimeoutObject(timeout_sec)
 
-            while self._context.ok() and not future.done() and not self._is_shutdown:
+            while (
+                self._context.ok() and
+                not future.done() and
+                not future.cancelled()
+                and not self._is_shutdown
+            ):
                 self._spin_once_until_future_complete(future, timeout_left)
                 now = time.monotonic()
 
@@ -610,6 +620,8 @@ def _wait_for_ready_callbacks(
                 with self._tasks_lock:
                     # Get rid of any tasks that are done
                     self._tasks = list(filter(lambda t_e_n: not t_e_n[0].done(), self._tasks))
+                    # Get rid of any tasks that are cancelled
+                    self._tasks = list(filter(lambda t_e_n: not t_e_n[0].cancelled(), self._tasks))
 
             # Gather entities that can be waited on
             subscriptions: List[Subscription] = []

rclpy/rclpy/task.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from enum import auto, StrEnum
 import inspect
 import sys
 import threading
@@ -31,14 +32,19 @@ def _fake_weakref() -> None:
     return None
 
 
+class FutureState(StrEnum):
+    """States defining the lifecycle of a future."""
+
+    PENDING = auto()
+    CANCELLED = auto()
+    FINISHED = auto()
+
+
 class Future(Generic[T]):
     """Represent the outcome of a task in the future."""
 
     def __init__(self, *, executor: Optional['Executor'] = None) -> None:
-        # true if the task is done or cancelled
-        self._done = False
-        # true if the task is cancelled
-        self._cancelled = False
+        self._state = FutureState.PENDING
         # the final return value of the handler
         self._result: Optional[T] = None
         # An exception raised by the handler when called
@@ -61,15 +67,20 @@ def __del__(self) -> None:
 
     def __await__(self) -> Generator[None, None, Optional[T]]:
         # Yield if the task is not finished
-        while not self._done:
+        while self._pending():
             yield
         return self.result()
-
+
+    def _pending(self) -> bool:
+        return self._state == FutureState.PENDING
+
     def cancel(self) -> None:
         """Request cancellation of the running task if it is not done already."""
         with self._lock:
-            if not self._done:
-                self._cancelled = True
+            if not self._pending():
+                return
+
+        self._state = FutureState.CANCELLED
         self._schedule_or_invoke_done_callbacks()
 
     def cancelled(self) -> bool:
@@ -78,15 +89,15 @@ def cancelled(self) -> bool:
 
         :return: True if the task was cancelled
         """
-        return self._cancelled
+        return self._state == FutureState.CANCELLED
 
     def done(self) -> bool:
         """
-        Indicate if the task has finished executing.
+        Indicate if the task has finished or cancelled executing.
 
-        :return: True if the task is finished or raised while it was executing
+        :return: True if the task is finished, cancelled or raised while it was executing
         """
-        return self._done
+        return self._state == FutureState.FINISHED
 
     def result(self) -> Optional[T]:
         """
@@ -114,12 +125,17 @@ def set_result(self, result: T) -> None:
         """
         Set the result returned by a task.
 
+        :raises: RuntimeError if future state is not pending
+
         :param result: The output of a long running task.
         """
         with self._lock:
+            if not self._pending():
+                raise RuntimeError(f"Cannot set result from state: {self._state}")
+
             self._result = result
-            self._done = True
-            self._cancelled = False
+            self._state = FutureState.FINISHED
+
         self._schedule_or_invoke_done_callbacks()
 
     def set_exception(self, exception: Exception) -> None:
@@ -129,10 +145,13 @@ def set_exception(self, exception: Exception) -> None:
         :param result: The output of a long running task.
         """
         with self._lock:
+            if not self._pending():
+                raise RuntimeError(f"Cannot set exception from state: {self._state}")
+
             self._exception = exception
             self._exception_fetched = False
-            self._done = True
-            self._cancelled = False
+            self._state = FutureState.FINISHED
+
         self._schedule_or_invoke_done_callbacks()
 
     def _schedule_or_invoke_done_callbacks(self) -> None:
@@ -181,7 +200,7 @@ def add_done_callback(self, callback: Callable[['Future[T]'], None]) -> None:
         """
         invoke = False
         with self._lock:
-            if self._done:
+            if not self._pending():
                 assert self._executor is not None
                 executor = self._executor()
                 if executor is not None:
@@ -239,10 +258,14 @@ def __call__(self) -> None:
 
         The return value of the handler is stored as the task result.
         """
-        if self._done or self._executing or not self._task_lock.acquire(blocking=False):
+        if (
+            not self._pending() or
+            self._executing or
+            not self._task_lock.acquire(blocking=False)
+        ):
             return
         try:
-            if self._done:
+            if not self._pending():
                 return
             self._executing = True
 
@@ -253,7 +276,6 @@ def __call__(self) -> None:
                     handler.send(None)
                 except StopIteration as e:
                     # The coroutine finished; store the result
-                    handler.close()
                     self.set_result(e.value)
                     self._complete_task()
                 except Exception as e:
@@ -285,3 +307,9 @@ def executing(self) -> bool:
         :return: True if the task is currently executing.
         """
         return self._executing
+
+    def cancel(self) -> None:
+        if self._pending() and inspect.iscoroutine(self._handler):
+            self._handler.close()
+
+        super().cancel()

rclpy/test/test_executor.py

@@ -273,6 +273,26 @@ async def coroutine():
         self.assertTrue(future.done())
         self.assertEqual('Sentinel Result', future.result())
 
+    def test_create_task_coroutine_cancel(self) -> None:
+        self.assertIsNotNone(self.node.handle)
+        executor = SingleThreadedExecutor(context=self.context)
+        executor.add_node(self.node)
+
+        async def coroutine():
+            return 'Sentinel Result'
+
+        future = executor.create_task(coroutine)
+        self.assertFalse(future.done())
+        self.assertFalse(future.cancelled())
+
+        future.cancel()
+        self.assertTrue(future.cancelled())
+
+        executor.spin_until_future_complete(future)
+        self.assertFalse(future.done())
+        self.assertTrue(future.cancelled())
+        self.assertEqual(None, future.result())
+
     def test_create_task_normal_function(self) -> None:
         self.assertIsNotNone(self.node.handle)
         executor = SingleThreadedExecutor(context=self.context)

rclpy/test/test_task.py

@@ -322,6 +322,29 @@ def cb(fut):
         f.add_done_callback(cb)
         assert called
 
+    def test_set_result_on_done_future_raises_exception(self) -> None:
+        f = Future()
+        f.set_result(None)
+        with self.assertRaises(RuntimeError):
+            f.set_result(None)
+
+    def test_set_result_on_cancelled_future_raises_exception(self) -> None:
+        f = Future()
+        f.cancel()
+        with self.assertRaises(RuntimeError):
+            f.set_result(None)
+
+    def test_set_exception_on_done_future_raises_exception(self) -> None:
+        f = Future()
+        f.set_result(None)
+        with self.assertRaises(RuntimeError):
+            f.set_exception(Exception())
+
+    def test_set_exception_on_cancelled_future_raises_exception(self) -> None:
+        f = Future()
+        f.cancel()
+        with self.assertRaises(RuntimeError):
+            f.set_exception(Exception())
 
 if __name__ == '__main__':
     unittest.main()