pkg-config and pythonX.X-config not correctly installed by actions/setup-python?

[jdpipe]

Description:
I have a workflow that required building of shared libraries for OpenModelica that embed the Python interpreter. When using actions/setup-python to test this workflow, I don't seem to have a reliable way of detecting the configuration options for linking to libpython -- neither pkg-config nor python3.8-config (or whatever it is for the version of Python in question) seem to work reliably. What is the suggested approach?

Action version:
I'm using the current actions/setup-python@v2
See https://github.com/SolarTherm/SolarTherm/runs/4515306450?check_suite_focus=true for details.

Platform:

• Ubuntu 20.04 and 18.04

Runner type:

• Hosted

Tools version:
3.8 on 18.04
3.9 on 20.04
(see output at above link)

Repro steps:
See above link.

Expected behavior:
I would expect both pkg-config and python-config scripts to be provided. They don't seem to be.

Actual behavior:
Missing scripts/.pc files results in build errors.

[nikita-bykov]

Hello @jdpipe, thank you for report!
I went through your logs and found the following error: Package 'python-3.8-embed' not found
The error content suggests adding to the PKG_CONFIG_PATH environment variable a directory containing python-3.8-embed.pc.
The python-3.8-embed.pc file on Ubuntu can be found at /opt/hostedtoolcache/Python/3.8.12/x64/lib/pkgconfig, so you should add it to PKG_CONFIG_PATH environment variable:

export PKG_CONFIG_PATH=/opt/hostedtoolcache/Python/3.8.12/x64/lib/pkgconfig

To adapt this path to any OS and any Python version you can use $pythonLocation environment variable and write it like this:

export PKG_CONFIG_PATH=$pythonLocation/lib/pkgconfig

Could you please check and confirm that adding this environment variable works for you?

[jdpipe]

Thanks @nikita-bykov, that sounds like it should work.

However can I suggest that pkg-config, as a developer tool, becomes most useful when library installers put their .pc in a place somewhere that the system already knows to look for them. This is analogous to installing scripts/binaries somewhere that's on the user's PATH. Installing things where the system can't automatically find them just makes things less convenient, and more platform-specific code is needed by the final user.

So I think that setup-python should either be installing the .pc files in a standard place, placing a symlink, or by taking on the job of making system-level changes to the PKG_CONFIG_PATH (via /etc/profile.d or whatever GHA uses). I wonder, how do you handle the PATH for your setup-python action currently, such that calling python just works? Whatever you are doing for the executable, I suspect you can do the same for the .pc files.

Note that you can see what pkg-config is doing by running either pkg-config --debug 2>&1 | grep directory or pkg-config --variable pc_path pkg-config. On my local system, it reports

john@ovo:~/openmodelica$ pkg-config --debug 2>&1 | grep directory
Cannot open directory #1 '/usr/local/lib/x86_64-linux-gnu/pkgconfig' in package search path: No such file or directory
Cannot open directory #2 '/usr/local/lib/pkgconfig' in package search path: No such file or directory
Cannot open directory #3 '/usr/local/share/pkgconfig' in package search path: No such file or directory
Scanning directory #4 '/usr/lib/x86_64-linux-gnu/pkgconfig'
Scanning directory #5 '/usr/lib/pkgconfig'
Scanning directory #6 '/usr/share/pkgconfig'

Another option here is to place Python's python-config (python3.8-config, etc) script on the PATH. Ideally you would do both, since some software links to Python using pkg-config, others use python-config.

[dsame]

@jdpipe
I created the PR to set the PKG_CONFIG_PATH as you've advised, thanks.

[dsame]

@jdpipe setup-python action has been updated to set PKG_CONFIG_PATH, so i believe @marko-zivic-93 can close this issue as resolved, but please feel free to re-open the issue or create another one in case of any problems. Much thanks for your assistance.

[marko-zivic-93]

Hello @jdpipe
As @dsame stated, I will close this issue, but feel free to leave a comment or create new issue if you still experience this problem.