Why is pip install called with --ignore-installed

[cpaulik]

This makes it hard to prepare an environment with conda and have pip packages with C dependencies in the requirements.txt

Details

• Project URL: https://github.com/TUW-GEO/gldas
• Build URL (if applicable): https://readthedocs.org/projects/gldas/builds/5774270/
• Read the Docs username (if applicable): cpaulik

Expected Result

pygrib should not be installed with pip since it is already installed via conda

Actual Result

pygrib installation failed because of missing system libraries for compiling the c code.

[cpaulik]

I worked around it by using python setup.py install instead.

[goerz]

Using setup_py_install: true and pip_install: false in readthedocs.yml works, but it requires that the conda environment file lists all dependency packages that should be installed through pip. As an example:

name: py36
channels:
  - defaults
  - conda-forge
dependencies:
  - python=3.6
  - anaconda
  - pytest-cov
  - pytest-xdist
  - coverage
  - pip:
      - better-apidoc
      - trajectorydata
      - sphinx-autobuild
      - git+https://github.com/mabuchilab/QNET.git@develop#egg=QNET-2.0.0-dev

[agjohnson]

This seems it can be closed. Our yaml config might soon have more options to configure these steps, but currently this case is a bit of an edge case.