Check if Task(Future) is canceled. (backport #1377)

rclpy/rclpy/executors.py

@@ -299,15 +299,25 @@ def spin_until_future_complete(self, future: Future, timeout_sec: float = None)
         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:
-                self.spin_once_until_future_complete(future, timeout_sec)
+            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:
-                self.spin_once_until_future_complete(future, timeout_left)
+            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()
 
                 if now >= end:
@@ -500,6 +510,8 @@ 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 Enum
 import inspect
 import sys
 import threading
@@ -24,14 +25,19 @@ def _fake_weakref():
     return None
 
 
+class FutureState(Enum):
+    """States defining the lifecycle of a future."""
+
+    PENDING = 'PENDING'
+    CANCELLED = 'CANCELLED'
+    FINISHED = 'FINISHED'
+
+
 class Future:
     """Represent the outcome of a task in the future."""
 
     def __init__(self, *, executor=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 = None
         # An exception raised by the handler when called
@@ -53,15 +59,20 @@ def __del__(self):
 
     def __await__(self):
         # Yield if the task is not finished
-        while not self._done:
+        while self._pending():
             yield
         return self.result()
 
+    def _pending(self):
+        return self._state == FutureState.PENDING
+
     def cancel(self):
         """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):
@@ -71,7 +82,7 @@ def cancelled(self):
         :return: True if the task was cancelled
         :rtype: bool
         """
-        return self._cancelled
+        return self._state == FutureState.CANCELLED
 
     def done(self):
         """
@@ -80,7 +91,7 @@ def done(self):
         :return: True if the task is finished or raised while it was executing
         :rtype: bool
         """
-        return self._done
+        return self._state == FutureState.FINISHED
 
     def result(self):
         """
@@ -111,8 +122,8 @@ def set_result(self, result):
         """
         with self._lock:
             self._result = result
-            self._done = True
-            self._cancelled = False
+            self._state = FutureState.FINISHED
+
         self._schedule_or_invoke_done_callbacks()
 
     def set_exception(self, exception):
@@ -124,8 +135,8 @@ def set_exception(self, exception):
         with self._lock:
             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):
@@ -173,7 +184,7 @@ def add_done_callback(self, callback):
         """
         invoke = False
         with self._lock:
-            if self._done:
+            if not self._pending():
                 executor = self._executor()
                 if executor is not None:
                     executor.create_task(callback, self)
@@ -226,10 +237,14 @@ def __call__(self):
 
         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
 
@@ -239,7 +254,6 @@ def __call__(self):
                     self._handler.send(None)
                 except StopIteration as e:
                     # The coroutine finished; store the result
-                    self._handler.close()
                     self.set_result(e.value)
                     self._complete_task()
                 except Exception as e:
@@ -271,3 +285,9 @@ def executing(self):
         :rtype: bool
         """
         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

@@ -225,6 +225,26 @@ 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):
         self.assertIsNotNone(self.node.handle)
         executor = SingleThreadedExecutor(context=self.context)

rclpy/test/test_task.py

@@ -322,6 +322,39 @@ def cb(fut):
         f.add_done_callback(cb)
         assert called
 
+    def test_set_result_on_done_future_without_exception(self) -> None:
+        f = Future()
+        f.set_result(None)
+        self.assertTrue(f.done())
+        self.assertFalse(f.cancelled())
+        f.set_result(None)
+        self.assertTrue(f.done())
+        self.assertFalse(f.cancelled())
+
+    def test_set_result_on_cancelled_future_without_exception(self) -> None:
+        f = Future()
+        f.cancel()
+        self.assertTrue(f.cancelled())
+        self.assertFalse(f.done())
+        f.set_result(None)
+        self.assertTrue(f.done())
+
+    def test_set_exception_on_done_future_without_exception(self) -> None:
+        f = Future()
+        f.set_result(None)
+        self.assertIsNone(f.exception())
+        f.set_exception(Exception())
+        f.set_result(None)
+        self.assertIsNotNone(f.exception())
+
+    def test_set_exception_on_cancelled_future_without_exception(self) -> None:
+        f = Future()
+        f.cancel()
+        self.assertTrue(f.cancelled())
+        self.assertIsNone(f.exception())
+        f.set_exception(Exception())
+        self.assertIsNotNone(f.exception())
+
 
 if __name__ == '__main__':
     unittest.main()