This follows up on this comment from @skirpichev: #23808 (comment) about f2py -c needing meson and ninja for Python 3.12 (or with --backend=meson on older Python versions).

Right now we do not use optional-dependencies at all. It is also the future replacement for test_requirements.txt & co. Here is an example of how it can be used: https://github.com/scipy/scipy/blob/9f7549abcc61f5dc72ca000cef7bc43066c74527/pyproject.toml#L74-L109

In numpy it could have an extra f2py section, and that would allow installing the needed dependencies with pip install numpy[f2py]. Of course you have to know that that's possible, and at that point you can equally well do pip install meson ninja , so this isn't all that urgent. An extra complication is that ninja is a system dependency, and using it from PyPI is a bit hacky. That's for example why meson and meson-python do not have a direct dependency on ninja; meson-python first checks if it's installed on the system and dynamically adds it in non-isolated installs if it's missing.

I'd say we don't want to do this for 1.26.0, but we can consider populating the optional dependencies table for 2.0.