Allow use of non-vendored Zenoh if present

[oysstu]

Description

Uses zenoh-c and zenoh-cpp if found by cmake. It's easier to handle distributing and patching of Zenoh on non-standard platforms if the rust build can be handled externally.

Is this user-facing behavior change?

Should not affect any users, unless they are building from source and have installed the libraries to the cmake search path.

Did you use Generative AI?

No

Additional Information

There's also #695 but it seems to have stalled. Would appreciate if this could be considered in the meantime.

[ahcorde]

Pulls: #908
Gist: https://gist.githubusercontent.com/ahcorde/4a89ff63bbd4d0605513a0531b729473/raw/c804702c650470234b0499c77d5d9dd09464593f/ros2.repos
BUILD args: --packages-above-and-dependencies zenoh_cpp_vendor
TEST args: --packages-above zenoh_cpp_vendor
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18209

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[JEnoch]

I believe using non-vendored Zenoh is useful but should be an option, and possibly not the default behaviour. Imagine a host where a version of zenoh-c is installed for non-ROS applications, but rmw_zenoh requires another version. How to deal with that ?

The commit ids which are set in zenoh_cpp_vendor/CMakeLists.txt are the ones that maintainers ensure rmw_zenoh will work as expected. I think using another version should be made on purpose with an explicit flag.

And it might be useful to log (info or warning) whenever another zenoh-c or zenoh-cpp version than the vendor one is used.

[oysstu]

I believe using non-vendored Zenoh is useful but should be an option, and possibly not the default behaviour. Imagine a host where a version of zenoh-c is installed for non-ROS applications, but rmw_zenoh requires another version. How to deal with that ?

The commit ids which are set in zenoh_cpp_vendor/CMakeLists.txt are the ones that maintainers ensure rmw_zenoh will work as expected. I think using another version should be made on purpose with an explicit flag.

And it might be useful to log (info or warning) whenever another zenoh-c or zenoh-cpp version than the vendor one is used.

That seems reasonable, I've updated the PR.

I decided to make it fail if USE_SYSTEM_ZENOH is set and it does not find the system installation instead of falling back on the vendored libraries.

[JEnoch]

A last comment: could you please also add a note in the README (in "Source Installation") wrt. this new USE_SYSTEM_ZENOH flag.

[JEnoch]

Pulls: #908
Gist: https://gist.githubusercontent.com/JEnoch/7bba8c32677d4dce5a5f3c6a8b1ca1a1/raw/c804702c650470234b0499c77d5d9dd09464593f/ros2.repos
BUILD args: "--continue-on-error" --packages-above-and-dependencies zenoh_cpp_vendor zenoh_security_tools rmw_zenoh_cpp
TEST args: --packages-above zenoh_cpp_vendor zenoh_security_tools rmw_zenoh_cpp
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18214

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[JEnoch]

https://github.com/Mergifyio backport kilted jazzy humble

[mergify]

backport kilted jazzy humble

✅ Backports have been created

Details

• #909 Allow use of non-vendored Zenoh if present (backport #908) has been created for branch kilted
• #910 Allow use of non-vendored Zenoh if present (backport #908) has been created for branch jazzy
• #911 Allow use of non-vendored Zenoh if present (backport #908) has been created for branch humble