Convert wait_set functions to pybind11 (#706)

* Convert wait_set functions to pybind11

Replaces rclpy_destroy_wait_set with pycapsule destructor for the rcl_wait_set_t type.

Signed-off-by: Shane Loretz <sloretz@openrobotics.org>
Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

* Remove unused variable

Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

* pass string by reference

Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

* Document pycontext arg

Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

* Throw bad_alloc if PyMem_Malloc fails

Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

rclpy/CMakeLists.txt

@@ -181,6 +181,7 @@ pybind11_add_module(_rclpy_pybind11 SHARED
   src/rclpy/subscription.cpp
   src/rclpy/time_point.cpp
   src/rclpy/timer.cpp
+  src/rclpy/wait_set.cpp
 )
 target_include_directories(_rclpy_pybind11 PRIVATE
   src/rclpy/

rclpy/rclpy/executors.py

@@ -60,17 +60,6 @@
     from rclpy.node import Node  # noqa: F401
 
 
-class _WaitSet:
-    """Make sure the wait set gets destroyed when a generator exits."""
-
-    def __enter__(self):
-        self.wait_set = _rclpy.rclpy_get_zero_initialized_wait_set()
-        return self.wait_set
-
-    def __exit__(self, t, v, tb):
-        _rclpy.rclpy_destroy_wait_set(self.wait_set)
-
-
 class _WorkTracker:
     """Track the amount of work that is in progress."""
 
@@ -521,7 +510,8 @@ def _wait_for_ready_callbacks(
                 entity_count += waitable.get_num_entities()
 
             # Construct a wait set
-            with _WaitSet() as wait_set, ExitStack() as context_stack:
+            wait_set = _rclpy.rclpy_get_zero_initialized_wait_set()
+            with ExitStack() as context_stack:
                 sub_capsules = []
                 for sub in subscriptions:
                     try: