Build dependency cycle due to pythran/networkx

When I build from source on macOS 11.4 I get the following error:

ImportError while importing test module '/Users/dlindelof/Private/scipy/build/testenv/lib/python3.8/site-packages/scipy/stats/tests/test_tukeylambda_stats.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
scipy/stats/__init__.py:441: in <module>
    from .stats import *
scipy/stats/stats.py:37: in <module>
    from scipy.spatial.distance import cdist
scipy/spatial/__init__.py:102: in <module>
    from ._geometric_slerp import geometric_slerp
scipy/spatial/_geometric_slerp.py:8: in <module>
    from scipy.spatial.distance import euclidean
scipy/spatial/distance.py:124: in <module>
    from ..special import rel_entr
scipy/special/__init__.py:643: in <module>
    from . import _ufuncs
E   ImportError: dlopen(/Users/dlindelof/Private/scipy/build/testenv/lib/python3.8/site-packages/scipy/special/_ufuncs.cpython-38-darwin.so, 2): Symbol not found: _cephes_cosdg
E     Referenced from: /Users/dlindelof/Private/scipy/build/testenv/lib/python3.8/site-packages/scipy/special/_ufuncs.cpython-38-darwin.so
E     Expected in: flat namespace
E    in /Users/dlindelof/Private/scipy/build/testenv/lib/python3.8/site-packages/scipy/special/_ufuncs.cpython-38-darwin.so

Scipy/Numpy/Python version information:

These are the first lines I get when I start the build/tests:

$ python runtests.py -v
Building, see build.log...
Build OK (0:00:12.526099 elapsed)
=================================================== test session starts ===================================================
platform darwin -- Python 3.8.2, pytest-6.2.4, py-1.10.0, pluggy-0.13.1 -- /Users/dlindelof/Private/scipy/.venv/bin/python
cachedir: .pytest_cache
rootdir: /Users/dlindelof/Private/scipy, configfile: pytest.ini

The build seems ok, I installed OpenBLAS via Homebrew and set the path in site.cfg like this:

[openblas]
libraries = openblas
library_dirs = /usr/local/Cellar/openblas/0.3.15_1/lib
include_dirs = /usr/local/Cellar/openblas/0.3.15_1/include
runtime_library_dirs = /usr/local/Cellar/openblas/0.3.15_1/lib

I was able to build and run the tests for numpy in another repository without problems.

[rgommers]

Ah, that’s why I’m confused: networkx 2.6.0 was released yesterday, until yesterday it indeed only depended on decorator and everything else was in extras.

[rgommers]

We had hoped that adding the main scientific Python libraries as dependencies wouldn’t be particularly disruptive with the availability of wheels for most major platforms.

Wheels have indeed made our life better, but unfortunately we have to deal with various from-source build scenarios as well. Both platforms without wheels (AIX, Alpine Linux, PowerPC, even macOS M1 still), and people who use pip install --no-binary for some reason (could be to build optimized binaries, or to work around some bug, or maybe other reasons too).

I do think NetworkX depending on NumPy is reasonable, and should not be too much of a problem (and Pythran depends on NumPy too). Perhaps even SciPy, depending on how important sparse.csgraph and linalg are. Why it should depend on pandas and especially Matplotlib is more questionable I’d think.