More general initialization of state from command (backport #2294)

[mergify]

Description

When operating a robot which does not always track desired positions accurately (e.g. torque controlled) you may sometimes want the JTC to initialize based on the current/latest command from the hardware interface, rather than the current measured state. This will ensure the "command" is unchanged when activating the controller. Otherwise, if you use measured state, the arm can move unexpectedly (usually, it will droop).

To handle this, JTC has set_last_command_interface_value_as_state_on_activation parameter. However, it's implementation is weird to me. Specifically, bool read_state_from_command_interfaces will return False if you have a velocity state interface but no velocity command interface. For me, this restriction seems unnecessary. You simply should need a state interface for each command interface, but not the other way around. Extra state interfaces are simply ignored.

Explanation of changes

Now, we always first call read_state_from_state_interfaces in on_activate.
Then, if the parameter is set, we update this state from the command interfaces.
Thus, we renamed read_state_from_command_interfaces to update_state_from_command_interface and change its behavior to only update fields that have command interfaces.
To minimize code duplication, I refactored out interface_has_values and assign_point_from_command_interface. This is the reason we have more deletions than additions :)

Also I updated the tests to reflect the desired change in behavior.

Fixes # (issue)

https://discourse.openrobotics.org/t/handling-missing-command-interfaces-in-read-state-from-command-interface/53551

Is this user-facing behavior change?

Yes!

Did you use Generative AI?

A bit of copilot autocompletion.

---

This is an automatic backport of pull request #2294 done by Mergify.

[mergify]

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Changes to be committed:
	modified:   joint_trajectory_controller/include/joint_trajectory_controller/joint_trajectory_controller.hpp
	modified:   joint_trajectory_controller/src/joint_trajectory_controller.cpp
	modified:   joint_trajectory_controller/src/joint_trajectory_controller_parameters.yaml
	modified:   joint_trajectory_controller/test/test_trajectory_controller.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   doc/release_notes.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[codecov]

Codecov Report

❌ Patch coverage is 94.11765% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.81%. Comparing base (df4be38) to head (1a6a120).

Files with missing lines	Patch %	Lines
...ory_controller/src/joint_trajectory_controller.cpp	90.90%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           kilted    #2357      +/-   ##
==========================================
+ Coverage   85.77%   85.81%   +0.03%     
==========================================
  Files         152      152              
  Lines       15073    15060      -13     
  Branches     1293     1293              
==========================================
- Hits        12929    12923       -6     
+ Misses       1685     1682       -3     
+ Partials      459      455       -4     

Flag	Coverage Δ
unittests	85.81% <94.11%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...jectory_controller/joint_trajectory_controller.hpp	50.00% <ø> (ø)
...ory_controller/test/test_trajectory_controller.cpp	99.75% <100.00%> (+<0.01%)	⬆️
...ory_controller/src/joint_trajectory_controller.cpp	83.96% <90.90%> (+0.29%)	⬆️

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