Import message and support setting values of complex arrays/sequence

[mikaelarguedas]

Version of #33 not changing the API exposed by message packages.

This is a redo of ros2/ros2cli#197 targetting this repository and updated to match what is returned by get_fields_and_field_types.

I left the tests commented out for now, they were passing about 2 days ago but since the message fixtures have been changed and the rosidl_runtime_py tests were not passing.
Submitting for review without updated tests. Hopefully we can update the tests shortly once the test_msgs situation stabilizes

Tests have been updated, ready for review

tested using command from ros2/ros2cli#191 (comment):

ros2 topic pub some_pose_array geometry_msgs/PoseArray "{header: {stamp: {sec: 1, nanosec: 2}, frame_id: some_frame}, poses: [{position: {x: 0, y: 1, z: 2}, orientation: {x: 3, y: 4, z: 5, w: 6}}]}"

[dirk-thomas]

Once this problem has been addressed the API would not need to take topic_name anymore which would break users. Therefore I don't think this API should added as-is.

[mikaelarguedas]

I would expect in the future the import function to be something like https://github.com/ros2/rosidl_python/pull/33/files#diff-2283820db2117771f9254b0ff5ac87f0 using the abstract types.

What would be an acceptable API in the meantime? a keyword argument for the topic_name that would default to an empty string? (note that it would still break API the day that keyword argument is removed).

Or would you rather keep the original function in ros2topic and make a duplicated function here without this argument at all ?

[dirk-thomas]

I would rather not add API here which is known that it needs to change as soon as something else gets fixed. So for now the API can stay were it is and once a stable API can be created it can land in the rosidl_runtime_py package.

Also I just created #54 which adds the SLOT_TYPES to each message. Maybe that is sufficient for what you want to achieve?

[mikaelarguedas]

Thanks, just to clarify my understanding:
The suggestion is to use the SLOT_TYPES from #54
introduce here the new import_message_from_namespaced_type from #33
and modify set_message to use these 2 new bits in order to fill Nested ROS messages

Is that right ?

[dirk-thomas]

Yeah, that should work.

[mikaelarguedas]

Alright I integrated the changes from #54 and updated #33 accordingly.

[mikaelarguedas]

Superseeded by #33