fix: Handle action rejection and server timeout (backport #1139) (#1156)

* add server timeout exception

* forward rejected goal handles

The goal_response_cb should not throw an exception, so the exception is passed in the result and then raised in  send_goal

* return an empty result when result was None due to cancellation/abortion

* fix lint error

---------

Co-authored-by: Spir0u <28966599+Spir0u@users.noreply.github.com>

Author: bjsowa

rosbridge_library/src/rosbridge_library/capabilities/advertise_action.py

@@ -97,10 +97,6 @@ def done_callback(fut: Future) -> None:
             if fut.cancelled():
                 goal.abort()
                 self.protocol.log("info", f"Aborted goal {goal_id}")
-                # Send an empty result to avoid stack traces
-                fut.set_result(
-                    cast("ROSActionResultT", get_action_class(self.action_type).Result())
-                )
             else:
                 if goal_id not in self.goal_statuses:
                     goal.abort()
@@ -132,7 +128,9 @@ def done_callback(fut: Future) -> None:
 
         try:
             result = await future
-            assert result is not None, "Action result cannot be None"
+            if result is None:
+                # Return empty result when cancelled/aborted
+                return cast("ROSActionResultT", get_action_class(self.action_type).Result())
             return result
         finally:
             del self.goal_futures[goal_id]

rosbridge_library/src/rosbridge_library/internal/actions.py

@@ -148,7 +148,7 @@ def args_to_action_goal_instance(inst: ROSMessage, args: list | dict[str, Any] |
 class SendGoal(Generic[ROSActionGoalT, ROSActionResultT, ROSActionFeedbackT]):
     """Helper class to send action goals."""
 
-    result: GetResultServiceResponse[ROSActionResultT] | None = None
+    result: GetResultServiceResponse[ROSActionResultT] | Exception | None = None
 
     def __init__(self, server_timeout_time: float = 1.0, sleep_time: float = 0.001) -> None:
         self.server_timeout_time = server_timeout_time
@@ -164,7 +164,8 @@ def goal_response_cb(self, future: Future) -> None:
         assert self.goal_handle is not None
         if not self.goal_handle.accepted:
             msg = "Action goal was rejected"
-            raise Exception(msg)
+            self.result = Exception(msg)
+            return
         result_future: Future = self.goal_handle.get_result_async()
         result_future.add_done_callback(self.get_result_cb)
 
@@ -189,14 +190,20 @@ def send_goal(
 
         self.result = None
         client = ActionClient(node_handle, action_class, action_name)
-        client.wait_for_server(timeout_sec=self.server_timeout_time)
+        if not client.wait_for_server(timeout_sec=self.server_timeout_time):
+            msg = "No action server available"
+            raise Exception(msg)
         send_goal_future = client.send_goal_async(inst, feedback_callback=feedback_cb)  # type: ignore[arg-type]
         send_goal_future.add_done_callback(self.goal_response_cb)
 
         while self.result is None:
             time.sleep(self.sleep_time)
 
         client.destroy()
+
+        if isinstance(self.result, Exception):
+            raise self.result
+
         if self.result is not None:
             # Turn the response into JSON and pass to the callback
             json_response = extract_values(self.result)