Does anyone know how to add a marker based on the PyPy version in a
pyproject.toml file? Or, how else to enforce build dependencies for pip in
the same way that can be done with the pyproject.toml file?
I don't see any marker that would work in the allowed environmental markers [0].
Although implementation_version looks promising, it is defined as "sys.implementation.version" which is an alias to the python version. "implementation" is also not helpful.
Matti
[0] https://www.python.org/dev/peps/pep-0508/#environment-markers