Use a temporary build directory for Python module output

[bjsowa]

The generate_parameter_module macro outputs the Python module to CMAKE_INSTALL_DIR during the build phase. This results in build failures on the ROS buildfarm due to permission errors (example here)

This PR modifies the macro to output the module to a temporary directory in CMAKE_CURRENT_BINARY_DIR and install it to CMAKE_INSTALL_DIR during the install phase.

[christophfroehlich]

If the current setup fails on the buildfarm, why haven't that failed earlier? Or is it that simple, nobody released a python node using this library?

[bjsowa]

If the current setup fails on the buildfarm, why haven't that failed earlier? Or is it that simple, nobody released a python node using this library?

From what I see, we are the first 😎

[christophfroehlich]

The result looks good, just not sure if there is a more cmake-native way in fixing this. So, waiting for another review.

btw: I remembered that we had an issue about python install location, but it was in setup.py configs #206.

[bjsowa]

@christophfroehlich Any chance this gets merged and released soon? I'm getting a lot of spam from ROS buildfarm about failing jobs...

[sea-bass]

This looks good at a glance!

My only question (from limited experience working in this package): how does this change affect symlink-install and/or merge-install workflows, if at all? Maybe worth a quick test

[bjsowa]

This looks good at a glance!

My only question (from limited experience working in this package): how does this change affect symlink-install and/or merge-install workflows, if at all? Maybe worth a quick test

In symlink-install, the generator python module in install directory will be symlinked to the one created in the temp build directory. The merge-install is not affected at all.

[christophfroehlich]

I've tested the three options now with generate_parameter_module_example, I don't see any downsides.

[christophfroehlich]

@bjsowa Now our example_module fails on the buildfarm
https://build.ros2.org/view/Rdev/job/Rdev__generate_parameter_library__ubuntu_noble_amd64/43/console#console-section-33

00:10:32 test/test_load_modules.py:35: in <module>
00:10:32     import generate_parameter_module_example.admittance_parameters  # noqa: E402
00:10:32 E   ModuleNotFoundError: No module named 'generate_parameter_module_example.admittance_parameters'

Any idea how to fix this?

[bjsowa]

@bjsowa Now our example_module fails on the buildfarm https://build.ros2.org/view/Rdev/job/Rdev__generate_parameter_library__ubuntu_noble_amd64/43/console#console-section-33

00:10:32 test/test_load_modules.py:35: in <module>
00:10:32     import generate_parameter_module_example.admittance_parameters  # noqa: E402
00:10:32 E   ModuleNotFoundError: No module named 'generate_parameter_module_example.admittance_parameters'

Any idea how to fix this?

It doesn't seem related as example_module is not using cmake.

[christophfroehlich]

Oh my bad, I have tested the options with the wrong package above 🙈 Just tested now also successfully with cmake_generate_parameter_module_example.
I'll dig into the build farm error.