meson: copy .py files to build directory

[keszybz]

This seems to do the trick:

$ ninja -C build
$ PYTHONPATH=build/src/ python -c 'from systemd import id128; print(id128)'
<module 'systemd.id128' from '/home/zbyszek/src/python-systemd/build/src/systemd/id128.cpython-313-x86_64-linux-gnu.so'>
$ PYTHONPATH=build/src/ pytest build/src/systemd/test ...
============================ test session starts ============================= platform linux -- Python 3.13.4, pytest-8.3.4, pluggy-1.5.0 rootdir: /home/zbyszek/src/python-systemd
configfile: pyproject.toml
plugins: ...
collected 61 items

build/src/systemd/test/test_daemon.py ........................         [ 39%]
build/src/systemd/test/test_id128.py ....                              [ 45%]
build/src/systemd/test/test_journal.py ............................    [ 91%]
build/src/systemd/test/test_login.py .....                             [100%]

============================= 61 passed in 0.21s =============================

[keszybz]

/cc @jelly

[jelly]

Neat, with this you can also introduce a test target:

build_dir = meson.current_build_dir() / 'src'
test_dir = meson.current_source_dir() / 'test'

test(
  'unit tests', 
  find_program('pytest'),
  args: [test_dir],
  env: { 'PYTHONPATH': build_dir },
)

[behrmann]

Nice! Tested it and it works. I do wonder why it didn't work when we copied in the files manually

[behrmann]

I wanted to propose to not ship the tests in the module, since they are not really useful to users anyway. This way this file would also not be needed.

[keszybz]

Reworked. The new meson file in the subdirectory is dropped, the tests are run from the source directory.
A new commit to add a test() declaration is added. meson test -C build and ninja -C build test now work.

I think we want to rework the sphinx build process to not require an installation, but let's do that in #158.

[behrmann]

Running

meson setup build
meson compile -C build
meson test -C build

fails for me, because the PYTHONPATH gets set up wrong to $PROJECT_ROOT/build/src/systemd

Since I also mentioned moving the tests out of the sources, by moving the tests up to the project root and then adding a new meson.build in src/

test(
        'unit',
        find_program(python.full_path()),
        args: [
                '-m', 'pytest',
                '-v',
                meson.project_source_root() / 'test',
              ],
        env: { 'PYTHONPATH': meson.current_build_dir() },
)

subdir('systemd')

The subdir in the top-level meson.build need to refer to that then, but all the testing related stuff in src/systemd/meson.build can be dropped.

I've not yet thought about how to do it without moving the tests up to the top-level, since python_test_dir only gets defined in src/systemd/meson.build.

[keszybz]

Oh, I messed up the paths. Can you try the current version?
(I think we can move the tests, but I'm not sure if this is wanted.)

[behrmann]

Checked, installation into a venv works with plain python -m venv and uv. Tests run with meson setup, compile, test cycle.