In NumPy we had to vendor Meson in order to include a major new feature (for SIMD support) that is not yet available in Meson itself. That is fine, that's how it's supposed to work, since Meson isn't extensible by design - the point is to keep things simple and upstream your needed features/changes.

However, using that vendored Meson also forced us to vendor meson-python. The only reason for that was to be able to point at the correct meson executable. So ideally meson-python would have a way for a package to point at that custom Meson instead. This could be done via a MESON environment variable (similar to the NINJA one), and/or in some other way (a setting in pyproject.toml perhaps.

Part of what's needed here is being able to point at a meson.py (as shipped with Meson itself), and have meson-python translate that to [sys.executable, 'path/to/meson.py']. This has to do with it being a problem on Windows to ship an executable file meson and have it recognized. See numpy/numpy#24379 (comment) and following comments for details.

This idea was also touched upon in gh-323. It's related but not the same, so I thought I'd open a separate issue instead. The implementation is probably quite simply, the main thing to decide is what the UX for this should look like.