Roslaunch not able to detect launch file packages

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The way your package was set up is likely incorrect for use with a catkin workspace. Try the following:

1. Make sure your catkin workspace is configured properly, and that you can build and source it
2. Ensure you can build other packages from your catkin workspace and can run nodes of those packages
3. Assuming your test_nav is a package, not a metapackage, configure CMakeLists.txt and package.xml (see details)
4. I would advise you create a folder called launch/ inside test_nav and move the launch files there (just to keep your package tidy)

The first two steps are to ensure the problem is not with your workspace. The third step is to ensure your package is catkin-compliant.

In the worst case scenario, move the test_nav folder out of your catkin workspace, then create a new package with the same name in your workspace with catkin_create_pkg, configure the CMakeLists.txt and package.xml files, copy the header/source/launch files to their corresponding folders and try to build your workspace again.

Remember to source your workspace after building it. Sometimes, I need to run rospack profile even after sourcing my workspace so that the newly built nodes get indexed. I don't know why, and never bothered looking into it, as it's a minor issue to me and happens very rarely.

I hope it helps.

Does your test_nav package have a package.xml and a CMakeLists.txt ?