Don't throw an exception if removing a node not associated with any executor

[skyegalaxy]

Description

This PR changes remove_node in both executor_entities_collector and events_cbg_executor to warn the user that the node they're trying to remove isn't associated with the executor, instead of throwing an exception, as well as updating the existing tests.

An exception will still be thrown if the user tries to remove a node associated with a DIFFERENT executor, as that would be an obvious programmer error. The behavior of remove_node in EventsCBGExecutor has been updated to mirror this behavior from the other executors.

A regression test has also been added to test_component_manager_api in rclcpp_components, which asserts that an exception isn't thrown during the double-removal case as outlined in #3186

Fixes #3186

Is this user-facing behavior change?

• Users will no longer get an exception on shutdown when using component managers with the callback group events executor
• Users will now get a WARNING instead of an exception throw when trying to remove a node not associated with any executor
• Users will now get an exception if they try to add a node already associated with another executor to the callback group events executor

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Claude Opus 4.8

Additional Information

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[ahcorde]

Pulls: #3190
Gist: https://gist.githubusercontent.com/ahcorde/0921923647104ed12128ae08da3c7b80/raw/62b669e2d3ce5aba62ac68d53a57e0c095eb3cfa/ros2.repos
BUILD args: --packages-above-and-dependencies rclcpp rclcpp_components
TEST args: --packages-above rclcpp rclcpp_components
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/19824

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[fujitatomoya]

i have 2 comments.

• rclcpp/rclcpp/include/rclcpp/executor.hpp

  Line 224 in d031217

  * \throw std::runtime_error if the node is not associated with an executor.

  should be also updated align with implementation.
• normal Ctrl+C shutdown will now WARN-spam once per node, every time. the double-remove sequence is still deterministic though. either the coordination should also be fixed (e.g., ~ComponentManager skips nodes whose association flag is already clear, or EventsCBGExecutor's shutdown notifies/clears differently)? warning on every clean shutdown trains users to ignore warnings?

[skyegalaxy]

I appreciate your review and feedback @fujitatomoya ! I updated the docstrings here and also added a check in the component manager destructor for if the node's already associated with an executor before removing. That gets rid of the warning for the test case I added on my end.

[skyegalaxy]

• Linux
• Linux-aarch64
• Linux-rhel
• Windows