allow rmw event callback to be NULL to unset them

rcl/include/rcl/client.h

@@ -427,10 +427,10 @@ rcl_client_is_valid(const rcl_client_t * client);
  * <i>[1] rmw implementation defined</i>
  *
  * \param[in] client The client on which to set the callback
- * \param[in] callback The callback to be called when new responses arrive
+ * \param[in] callback The callback to be called when new responses arrive, may be NULL
  * \param[in] user_data Given to the callback when called later, may be NULL
  * \return `RCL_RET_OK` if callback was set to the listener, or
- * \return `RCL_RET_INVALID_ARGUMENT` if `client` or `callback` is NULL, or
+ * \return `RCL_RET_INVALID_ARGUMENT` if `client` is NULL, or
  * \return `RCL_RET_UNSUPPORTED` if the API is not implemented in the dds implementation
  */
 RCL_PUBLIC

rcl/include/rcl/event.h

@@ -217,10 +217,10 @@ rcl_event_is_valid(const rcl_event_t * event);
  * <i>[1] rmw implementation defined</i>
  *
  * \param[in] event The event on which to set the callback
- * \param[in] callback The callback to be called when new events occur
+ * \param[in] callback The callback to be called when new events occur, may be NULL
  * \param[in] user_data Given to the callback when called later, may be NULL
  * \return `RCL_RET_OK` if callback was set to the listener, or
- * \return `RCL_RET_INVALID_ARGUMENT` if `event` or `callback` is NULL, or
+ * \return `RCL_RET_INVALID_ARGUMENT` if `event` is NULL, or
  * \return `RCL_RET_UNSUPPORTED` if the API is not implemented in the dds implementation
  */
 RCL_PUBLIC

rcl/include/rcl/service.h

@@ -458,10 +458,10 @@ rcl_service_is_valid(const rcl_service_t * service);
  * <i>[1] rmw implementation defined</i>
  *
  * \param[in] service The service on which to set the callback
- * \param[in] callback The callback to be called when new requests arrive
+ * \param[in] callback The callback to be called when new requests arrive, may be NULL
  * \param[in] user_data Given to the callback when called later, may be NULL
  * \return `RCL_RET_OK` if callback was set to the listener, or
- * \return `RCL_RET_INVALID_ARGUMENT` if `service` or `callback` is NULL, or
+ * \return `RCL_RET_INVALID_ARGUMENT` if `service` is NULL, or
  * \return `RCL_RET_UNSUPPORTED` if the API is not implemented in the dds implementation
  */
 RCL_PUBLIC

rcl/include/rcl/subscription.h

@@ -630,10 +630,10 @@ rcl_subscription_can_loan_messages(const rcl_subscription_t * subscription);
  * <i>[1] rmw implementation defined</i>
  *
  * \param[in] subscription The subscription on which to set the callback
- * \param[in] callback The callback to be called when new messages arrive
+ * \param[in] callback The callback to be called when new messages arrive, may be NULL
  * \param[in] user_data Given to the callback when called later, may be NULL
  * \return `RCL_RET_OK` if successful, or
- * \return `RCL_RET_INVALID_ARGUMENT` if `subscription` or `callback` is NULL, or
+ * \return `RCL_RET_INVALID_ARGUMENT` if `subscription` is NULL, or
  * \return `RCL_RET_UNSUPPORTED` if the API is not implemented in the dds implementation
  */
 RCL_PUBLIC

rcl/src/rcl/client.c

@@ -291,7 +291,7 @@ rcl_client_set_on_new_response_callback(
     // error state already set
     return RCL_RET_INVALID_ARGUMENT;
   }
-  RCL_CHECK_FOR_NULL_WITH_MSG(callback, "callback is invalid", return RCL_RET_INVALID_ARGUMENT);
+
   return rmw_client_set_on_new_response_callback(
     client->impl->rmw_handle,
     callback,

rcl/src/rcl/event.c

@@ -228,7 +228,7 @@ rcl_event_set_callback(
     // error state already set
     return RCL_RET_INVALID_ARGUMENT;
   }
-  RCL_CHECK_FOR_NULL_WITH_MSG(callback, "callback is invalid", return RCL_RET_INVALID_ARGUMENT);
+
   return rmw_event_set_callback(
     &event->impl->rmw_handle,
     callback,

rcl/src/rcl/service.c

@@ -311,7 +311,7 @@ rcl_service_set_on_new_request_callback(
     // error state already set
     return RCL_RET_INVALID_ARGUMENT;
   }
-  RCL_CHECK_FOR_NULL_WITH_MSG(callback, "callback is invalid", return RCL_RET_INVALID_ARGUMENT);
+
   return rmw_service_set_on_new_request_callback(
     service->impl->rmw_handle,
     callback,

rcl/src/rcl/subscription.c

@@ -447,7 +447,7 @@ rcl_subscription_set_on_new_message_callback(
     // error state already set
     return RCL_RET_INVALID_ARGUMENT;
   }
-  RCL_CHECK_FOR_NULL_WITH_MSG(callback, "callback is invalid", return RCL_RET_INVALID_ARGUMENT);
+
   return rmw_subscription_set_on_new_message_callback(
     subscription->impl->rmw_handle,
     callback,