setup.py + cython == chicken and the egg problem

[Dan Stromberg]

Hi folks.

I'm attempting to package up a python package that uses Cython.

Rather than build binaries for everything under the sun, I've been focusing
on including the .pyx file and running cython on it at install time.  This
requires a C compiler, but I'm OK with that.

However, when I try to install the package from test.pypi.org, I get:
$ python3 -m pip install -i https://test.pypi.org/simple/ pyx-treap
below cmd output started 2022 Tue Aug 16 01:55:16 PM PDT
Looking in indexes: https://test.pypi.org/simple/
Collecting pyx-treap
  Downloading
https://test-files.pythonhosted.org/packages/3a/41/af5360934adccfc086a39e1f720323895144b53454ff6dacc0f06267db55/pyx_treap-2.0.15.tar.gz
(125 kB)

 ????????????????????????????????????????????????????????????????????????????????
125.9/125.9 kB 1.9 MB/s eta 0:00:00
  Installing build dependencies ... error
  error: subprocess-exited-with-error

  ×? pip subprocess to install build dependencies did not run successfully.
  ?? exit code: 1
  ????> [3 lines of output]
      Looking in indexes: https://test.pypi.org/simple/
      ERROR: Could not find a version that satisfies the requirement
setuptools (from versions: none)
      ERROR: No matching distribution found for setuptools
      [end of output]

  note: This error originates from a subprocess, and is likely not a
problem with pip.
error: subprocess-exited-with-error

×? pip subprocess to install build dependencies did not run successfully.
?? exit code: 1
????> See above for output.

note: This error originates from a subprocess, and is likely not a problem
with pip.

But I analyzed the pip install with strace, and found no interesting
exec's, and no interesting "= E" patterns.

I've tried quite an assortment of things to get past this, including most
of those at:
https://stackoverflow.com/questions/4996589/in-setup-py-or-pip-requirements-file-how-to-control-order-of-installing-package
Except the one at:
https://stackoverflow.com/a/54269307/1084684
...because I was having a "there must be a better way" reaction to it.

/Is/ there a better way?

There're all these newer ways of doing packaging - surely one of them
addresses this problem?

The code I'm trying to package is at:
https://stromberg.dnsalias.org/svn/treap/trunk/cython

BTW, the pure python version works fine, and the cython version works too
as long as you preinstall cython - but I don't want users to have to know
that :)

Thanks!