package.xml, CMakeLists.txt, and Python Package Structure

Source: ros2-copilot-skills package configuration skill

Why This Matters

Many ROS 2 debugging sessions start in the wrong place because the real problem is packaging. If a package does not declare dependencies correctly or does not install launch, config, URDF, or Python entry points properly, the runtime failure often looks unrelated to the actual mistake.

Distilled Takeaways

• package.xml and the build file are part of the package API, not ceremony.
• Installation rules matter as much as compilation rules because ROS 2 tools find runtime assets in the install space.
• ament_cmake and ament_python packages have different failure modes, but both need careful asset installation.
• Interface packages deserve explicit structure because generated messages, services, and actions affect downstream builds.
• A surprising number of launch-time file lookup errors are packaging errors in disguise.

Practical Guidance

• Install launch, config, URDF, and related data directories deliberately.
• Use the narrowest dependency tags that remain readable.
• Keep Python package entry points and installed script locations aligned with ROS 2 expectations.
• Treat package structure as an onboarding surface for future contributors.

Corroborating References

• ROS 2 package creation tutorial
• ament_cmake documentation

When to Read the Original Source

Go to the original skill when you want complete example files for C++ packages, Python packages, and interface packages, including install rules and dependency-tag guidance.