ros2 topic pub auto header

[CourchesneA]

Feature request

Feature description

ROS1 allowed automatic filling of header and timestamp using keywords 'now' and 'auto'. It would be great to have that functionality in ROS2

Implementation considerations

ex.

ros2 topic pub my_topic geometry_msgs/TwistStamped '{header: auto}'

Expected behavior

geometry_msgs.msg.TwistStamped(header=std_msgs.msg.Header(stamp=builtin_interfaces.msg.Time(sec=1646834300, nanosec=280516750), frame_id=''), twist=geometry_msgs.msg.Twist(linear=geometry_msgs.msg.Vector3(x=0.0, y=0.0, z=0.0), angular=geometry_msgs.msg.Vector3(x=0.0, y=0.0, z=0.0)))

Actual behavior

Failed to populate field: Value 'auto' is expected to be a dictionary but is a str

[fujitatomoya]

ROS 1 wiki: http://wiki.ros.org/ROS/YAMLCommandLine#Headers.2Ftimestamps, this sounds reasonable to me. I would like to hear from others.

[clalancette]

@ivanpauno @esteve Could you add a note to the Iron Irwini release page? That way we'll have it queued up for release time.

[esteve]

@clalancette I just submitted ros2/ros2_documentation#2998

[clalancette]

@clalancette I just submitted ros2/ros2_documentation#2998

Thank you!