Dependencies from conda-forge are being removed during sphinx installation due to conda channel priority

Details

• Read the Docs project URL: https://freud.readthedocs.io/en/stable/
• Build URL (if applicable): https://readthedocs.org/projects/freud/builds/12216572/
• Read the Docs username (if applicable): bdice

Expected Result

I have a conda environment yml file:

name: freud-rtd
channels:
  - defaults
  - conda-forge
dependencies:
  - python
  - pip
  - scikit-build
  - cmake
  - cython
  - tbb
  - tbb-devel
  - numpy
  - sphinx
  - sphinx_rtd_theme
  - nbsphinx
  - jupyter_sphinx
  - sphinxcontrib-bibtex

Some of the packages are installed from conda-forge, and then removed during the step: conda install --yes --quiet --name 668 mock pillow sphinx sphinx_rtd_theme

I expected that this step wouldn’t remove my package dependencies.

Actual Result

Dependencies were removed, resulting in a failed build. This appears to be due to channel priority, where main is preferred over conda-forge in the second step even though my conda environment prefers conda-forge over main.

The following packages will be REMOVED:

  jupyter_sphinx-0.3.1-py39hde42818_1
  pybtex-0.23.0-py39hde42818_0
  pybtex-docutils-0.2.2-py39hde42818_2
  python_abi-3.9-1_cp39
  scikit-build-0.11.1-py39hf149a3a_2
  sphinxcontrib-bibtex-1.0.0-py_0

This appears to have changed in the last 2 weeks or so (or at least that’s when my builds started failing).

[stsewd]

Feature flags are experimental options that in time would be default or become an option, if this one becomes an option the config file would be great place, yes.

[stsewd]

Would the CONDA_APPEND_CORE_REQUIREMENTS feature flag help with this? https://docs.readthedocs.io/en/stable/guides/feature-flags.html#available-flags

Append Read the Docs core requirements to environment.yml file Makes Read the Docs to install all the requirements at once on conda create step. This helps users to pin dependencies on conda and to improve build time.