AIRO-1707 Implement latching in Publisher

[DLu]

Proposed change(s)

Resolves TODO in code, by reading latch parameter and setting QoS accordingly.

Types of change(s)

• [ ] Bug fix
• [x] New feature
• [ ] Code refactor
• [ ] Documentation update
• [ ] Other (please describe)

Testing and Verification

I created a publisher in Unity with latch=true

        ros.RegisterPublisher<OccupancyGridMsg>("static_map", 1, true); // queue_size=1, latch=true
        static_map = getOccupancyGrid();
        static_map.header.stamp = new TimeStamp(Clock.time);
        ros.Publish("static_map", static_map);

Without the fix, a latched subscriber will not recieve the message if it joins after the message is first published.

Test Configuration:

• Unity Version: 2021.1.12f1
• Unity machine Ubuntu 20.04
• ROS machine OS + version: Ubuntu 20.04 / Foxy
• ROS–Unity communication: From source?

Checklist

• [x] Ensured this PR is up-to-date with the dev branch
• [x] Created this PR to target the dev branch
• [x] Followed the style guidelines as described in the Contribution Guidelines
• [ ] Added tests that prove my fix is effective or that my feature works
• [ ] Updated the Changelog and described changes in the Unreleased section
• [ ] Updated the documentation as appropriate

Other comments

[unity-cla-assistant]

All committers have signed the CLA.

[at669]

Hi, thanks for the submission! I've created an internal ticket to follow this contribution, and the team will get back to you with updates.

As an FYI, I'm updating the name of this PR to match our internal ticket number to pass the jira-link Github Action.

[DLu]

Is there anything I can do to assist in the review process?

[LaurieCheers-unity]

Is there anything I can do to assist in the review process?

Hi, sorry for the delay, I will be reviewing this today.

[LaurieCheers-unity]

Even with this fix, I'm not receiving the latched message. How are you testing it?

[LaurieCheers-unity]

Let's just implement custom QoS settings per publisher, instead of trying to translate ROS1 concepts.

[DLu]

• Do you have a public issue that you're tracking for custom QoS?
• It seems like it will be tricky to unify the Unity API to handle both ROS 1 and ROS 2. What is your plan for that?

[DLu]

Is this project still active within Unity?