fix(cmake): register package via ament_package() in ROS 2 builds

[dakejahl]

Summary

Call ament_package() at the end of the ament-cmake branch so the package registers itself on AMENT_PREFIX_PATH when sourcing the colcon workspace's install/setup.bash.

Problem

The ament branch sets COMPILING_WITH_AMENT, finds ament_cmake/plotjuggler, and installs the .so, but never calls ament_package(). Without it, colcon doesn't emit local_setup.bash and the package never lands on AMENT_PREFIX_PATH. Downstream tools that walk AMENT_PREFIX_PATH to discover plugins (e.g. PlotJuggler #1374) can't find the .so even though it's installed. The catkin branch already calls catkin_package() on line 52; this restores parity.

Solution

Add ament_package() after the install rule, gated on COMPILING_WITH_AMENT so it's a no-op for catkin and bare-cmake builds.

Sponsored by ARK Electronics

[Georacer]

The pattern looks familiar, although I don't know the ament workings by heart.
Have you tested this yourself?

[dakejahl]

Yes — built and sourced locally on a colcon workspace. Before the patch, colcon build installs the .so but doesn't emit local_setup.bash or the share/ament_index/resource_index/packages/plotjuggler_apbin_plugins marker, so the prefix never lands on AMENT_PREFIX_PATH. After adding ament_package() the install tree looks like:

install/plotjuggler_apbin_plugins/
├── lib/plotjuggler_apbin_plugins/libDataAPBin.so
└── share/
    ├── ament_index/resource_index/packages/plotjuggler_apbin_plugins
    ├── plotjuggler_apbin_plugins/local_setup.bash
    └── plotjuggler_apbin_plugins/environment/ament_prefix_path.sh

Sourcing install/setup.bash then prepends the prefix to AMENT_PREFIX_PATH, and PlotJuggler (with PlotJuggler/PlotJuggler#1374) walks it and loads the plugin. Catkin and bare-cmake builds are unaffected since the call is gated on COMPILING_WITH_AMENT.

[Georacer]

Great, thanks!

[Georacer]

Yes — built and sourced locally on a colcon workspace. Before the patch, colcon build installs the .so but doesn't emit local_setup.bash or the share/ament_index/resource_index/packages/plotjuggler_apbin_plugins marker, so the prefix never lands on AMENT_PREFIX_PATH. After adding ament_package() the install tree looks like:

install/plotjuggler_apbin_plugins/
├── lib/plotjuggler_apbin_plugins/libDataAPBin.so
└── share/
    ├── ament_index/resource_index/packages/plotjuggler_apbin_plugins
    ├── plotjuggler_apbin_plugins/local_setup.bash
    └── plotjuggler_apbin_plugins/environment/ament_prefix_path.sh

Sourcing install/setup.bash then prepends the prefix to AMENT_PREFIX_PATH, and PlotJuggler (with PlotJuggler/PlotJuggler#1374) walks it and loads the plugin. Catkin and bare-cmake builds are unaffected since the call is gated on COMPILING_WITH_AMENT.

I do wonder though: You need to compile PlotJuggler first, in order to compile this AP plugin. What you're describing is fixing a dependency that goes the other way, no?

If I read your linked PJ PR, what you're trying to do is to auto-discover plugins, so this is a runtime dependency, correct?

[dakejahl]

Right on both counts:

• Build-time: this plugin depends on PlotJuggler (unchanged — still find_package(plotjuggler)).
• Runtime: PlotJuggler walks AMENT_PREFIX_PATH to discover plugins. That's the edge #1374 adds, and what this PR enables.

It's really packaging hygiene that's independent of #1374 though — without ament_package() the install isn't a valid ament package at all (no local_setup.bash, no ament_index entry), so e.g. ros2 pkg list doesn't see it. The catkin branch already calls catkin_package() on line 52; this restores parity for the ament branch.