--skip-python when a conda forge Python dependency is not in PyPI

[eriknw]

First off: hooray for trying to create an "easy button" for making wheels for those of us using conda forge!

Using conda-press version 0.0.6 on Python 3.7.

So. I have a new Python package on conda forge that has C dependencies, and I want an easy way to make wheels. Enter: conda press. Things almost worked perfectly the first try, but, alas, almost did not create a usable wheel.

Specifics. I want to build wheels for grblas. When I try to make a fat wheel without Python dependencies,

conda press --subdir osx-64 --skip-python --fatten --dont-strip-symbols grblas=1.2.6=py37h9bfed18_0

it includes python_abi as a dependency in METADATA. python_abi (which I think is only metadata) is on conda-forge, but not on PyPI. Hence, when I try to pip install the wheel I created, pip complains that it can't find python_abi.

Next, I created skinny wheels of everything, and then I tried to merge the original fat wheel with the wheel of python_abi

conda press --merge \
../press-fat/grblas-1.2.6-0_py37h9bfed18-cp37-cp37m-macosx_10_9_x86_64.whl \
../press-skinny/python_abi-3.7-1_1_cp37m-cp37-cp37m-macosx_10_9_x86_64.whl \
--output grblas-1.2.6-0_py37h9bfed18-cp37-cp37m-macosx_10_9_x86_64.whl

This failed:

Traceback (most recent call last):
  File "/Users/ewelch/miniconda3/envs/build-grblas/bin/conda-press", line 4, in <module>
    main()
  File "/Users/ewelch/miniconda3/envs/build-grblas/lib/python3.7/site-packages/conda_press/main.xsh", line 74, in main
    merge(wheels, output=output)
  File "/Users/ewelch/miniconda3/envs/build-grblas/lib/python3.7/site-packages/conda_press/wheel.xsh", line 779, in merge
    whl.write()
  File "/Users/ewelch/miniconda3/envs/build-grblas/lib/python3.7/site-packages/conda_press/wheel.xsh", line 373, in write
    skip_python=skip_python,
  File "/Users/ewelch/miniconda3/envs/build-grblas/lib/python3.7/site-packages/conda_press/wheel.xsh", line 393, in write_metadata
    return meth(**kwargs)
  File "/Users/ewelch/miniconda3/envs/build-grblas/lib/python3.7/site-packages/conda_press/wheel.xsh", line 400, in write_metadata_from_wheel
    if w is not None and getattr(w, "_top", False)][0]
IndexError: list index out of range

Next I tried to merge the skinny wheels together, selecting only what I need, so something like this

conda press --merge \
../libcxx-10.0.0-2_h1af66ff-py2.py3-none-macosx_10_9_x86_64.whl \
../llvm_openmp-10.0.0-0_h28b9765-py2.py3-none-macosx_10_9_x86_64.whl \
../graphblas-3.2.2-1_h4a8c4bd-py2.py3-none-macosx_10_9_x86_64.whl \
../grblas-1.2.6-0_py38h64e0658-cp38-cp38m-macosx_10_9_x86_64.whl \
../python_abi-3.8-1_1_cp38-cp38-cp38m-macosx_10_9_x86_64.whl \
--output grblas-1.2.6-0_py38h64e0658-cp38-cp38m-macosx_10_9_x86_64.whl

but this also fails.

Finally, I tried this:

conda press --subdir osx-64 --skip-python --fatten --dont-strip-symbols grblas=1.2.6=py37h9bfed18_0 --exclude-deps python_abi

which appears to work! It didn't build python_abi, but neither was it included as a dependency in METADATA. I suspect it's fine to ignore python_abi here. Am I going about things correctly here? If so, feel free to close!

[scopatz]

Thanks for reporting! PRs very welcome for fixing these issues.