BUG: generate_f2py mod is called by the wrong interpreter about scipy

[lucascolley]

are you aware of a good alternative? What is there, other than removing the shebang and forcing people to use the python command?

[bnavigator]

I guess it is okay for people to use the shebang instead of using python generate_f2pymod.py. But the meson build should not do that on it's own.

Ideas:

• Using a #!/usr/bin/env python3 shebang so that at least builds inside a venv do not use the system python3
• reverting part of #20121 so that meson always uses the current runtime interpreter for the python script
• having meson generate the script with the correct shebang from a generate_f2pymod.py.src and tempita.py (But that's a bit convoluted isn't it?

[lucascolley]

cc @rgommers

[bnavigator]

Hmm, when omitting the --no-build-isolation, meson actually does the right thing:

python3.12 -m pip -v wheel .
...
  Installing collected packages: ply, setuptools, pybind11, packaging, numpy, meson, gast, Cython, pyproject-metadata, beniget, pythran, meson-python
  Successfully installed Cython-3.0.10 beniget-0.4.1 gast-0.5.4 meson-1.4.0 meson-python-0.16.0 numpy-2.0.0rc1 packaging-24.0 ply-3.11 pybind11-2.12.0 pyproject-metadata-0.8.0 pythran-0.15.0 setuptools-69.5.1
...
  Running command Preparing metadata (pyproject.toml)
  + meson setup /scipy-1.13.0 /scipy-1.13.0/.mesonpy-wrowlhu5 -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --native-file=/scipy-1.13.0/.mesonpy-wrowlhu5/meson-python-native-file.ini
...
  Program python found: YES (/usr/bin/python3.12)
...
  Program tools/generate_f2pymod.py found: YES (/usr/bin/python3.12 /scipy-1.13.0/tools/generate_f2pymod.py)

Related: mesonbuild/meson-python#23

[rgommers]

Ah, sorry about that - that's a regression indeed. For code generation scripts that don't need numpy/cython, the shebang is preferred. But for these cases that's wrong indeed.

That part of gh-20121 should be reverted. I'd like to think a bit more about:

• whether to add a generator for f2py, so that the py3 doesn't need to be copied everywhere,
• if it's possible to use the build (native) Python with f2py/cython rather than the host (cross) Python. Perhaps by invoking f2py rather than python -m f2py.