python3-dev required?

[sloretz]

While building this on bionic I saw an error building launch_testing_ament_cmake

--- stderr: launch_testing_ament_cmake                                                                                                                                                            
CMake Error at /usr/share/cmake-3.10/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
  Could NOT find PythonLibs (missing: PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS)
  (Required is at least version "3.5")
Call Stack (most recent call first):
  /usr/share/cmake-3.10/Modules/FindPackageHandleStandardArgs.cmake:378 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.10/Modules/FindPythonLibs.cmake:262 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  /ros2_rolling/install/python_cmake_module/share/python_cmake_module/cmake/Modules/FindPythonExtra.cmake:133 (find_package)
  CMakeLists.txt:29 (find_package)


---
Failed   <<< launch_testing_ament_cmake [4.30s, exited with code 1]

It depends on python_cmake_module, but this repo REQUIREs PythonLibs to be found

python_cmake_module/cmake/Modules/FindPythonExtra.cmake

Line 133 in 80f6e54

find_package(PythonLibs 3.5 REQUIRED)

Maybe this package should depend on python3-dev? Or maybe launch_testing_ament_cmake should depend on python3-dev?

[clalancette]

There are actually two parts to this:

1. What provides the FindPythonLibs.cmake file
2. What provides the python libraries to be found

For the first one, it looks like that on Ubuntu, the package cmake-data provides FindPythonLibs.cmake. I think we typically assume that that is installed, so I think we can ignore that one here.

For the second one, it looks like the actual package that installs Python.h and /usr/lib/x86_64-linux-gnu/libpython3.8.so (at least on Ubuntu 20.04) is the libpython3.8-dev package. This in turn is depended on by python3.8-dev, which is depended on by python3-dev. This same pattern holds for Ubuntu 18.04 as well. On Fedora, the situation is a bit simpler in that python3-devel just contains the header files needed.

So that's the long way of saying that I agree with you; any place that calls find_package(PythonLibs) should depend on the python3-dev rosdep key. And since this is one of those places, I think this package should be the one to depend on it.

[mikaelarguedas]

Shouldnt that be covered by

python_cmake_module/package.xml

Line 17 in 80f6e54

<buildtool_export_depend>python3-dev</buildtool_export_depend>

?

If I had to guess the issue comes from the fact that you used rosdep to install your dependencies and that this fix ros-infrastructure/rosdep#753 still hasnt been released.

[sloretz]

If I had to guess the issue comes from the fact that you used rosdep to install your dependencies and that this fix ros-infrastructure/rosdep#753 still hasnt been released.

That's 100% what happened. Thanks for pointing that out! Looks like there's nothing to fix in this repo so I'll close this.