LifecycleNode publishes a null timestamp in `transition_event` topics

[Myzhar]

Required Info:

• Operating System:
  • Ubuntu 16.04
• Installation type:
  • Source
• Version or commit hash:
  • eb439dd
• DDS implementation:
  • Fast-RTPS
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

1. start a lifecycle talker node:
   $ ros2 run lifecycle lifecycle_talker
2. subscribe to the transition_event topic:
   $ ros2 topic echo /lc_talker/transition_event
3. require some transitions:
   $ ros2 lifecycle set /lc_talker configure
$ ros2 lifecycle set /lc_talker activate

I noticed the issue with my own lifecycle node and I tested it with the provided example to be sure that the issue is generic.

Expected behavior

current timestamp for the messages

Actual behavior

The timestamp is null as you can see in the following screenshoot

[Myzhar]

I noticed that also the transition field is empty.
Only the ßtart-state and the goal-state fields are filled

[clalancette]

Yeah, this is because the low-level publisher only fills in start-state and goal-state here: https://github.com/ros2/rcl/blob/master/rcl_lifecycle/src/com_interface.c#L229 . This could probably be improved, so I'm going to mark this as an enhancement.

[SuperJappie08]

This is still the case in Jazzy. Related (ros2/rcl#1019, ros2/rcl#1140)

[LastStarDust]

I just came here to say that this

I noticed that also the transition field is empty.
Only the ßtart-state and the goal-state fields are filled

is still the case in Jazzy but @SuperJappie08 beat me to it