Support pip install inside conda environment

[rgerkin]

Details

• Project URL: https://readthedocs.org/projects/neuronunit
• Build URL (if applicable): https://readthedocs.org/projects/neuronunit/builds/5238426/
• Read the Docs username (if applicable): rgerkin

Expected Result

I expect my pip requirements file (requirements.txt) to be processed at some point during the build, i.e. to see a pip install -r requirements.txt line, or something similar. I expect this because in my Admin/Advanced Settings page on readthedocs, I set the "Requirements file" field accordingly.

Actual Result

My requirements file is never processed. Consequently, my build fails.

[humitos]

@rgerkin hi! You are using a conda environment, that's why. As far as I know, if you use a conda env, you have to put the pip requirements inside the environment.yml used by conda.

Besides, I saw that you are using readthedocs.yml and I think that setting overrides the Admin/Advanced Settings.

---

I took a look at your settings and I can see that you are using the pip option inside the environment.yml and RTD is installing those packages also in the conda env but I don't really understand why the installation of your module fails trying to install again the packages that were already installed.

I need to keep taking a look, but that is what I have now. Sorry :(

[jdemeyer]

As far as I know, if you use a conda env, you have to put the pip requirements inside the environment.yml used by conda.

I did not manage to get that to work: https://readthedocs.org/projects/fpylll/builds/5289709/

My conda env file looks like

dependencies:
  - gmp
  - pip:
    - Cython
    - cysignals
    - git+https://github.com/jdemeyer/sphinx

It would be nice to have an actual working example of this.

[jdemeyer]

As far as I know, if you use a conda env, you have to put the pip requirements inside the environment.yml used by conda.

Is there a structural reason why RTD cannot support both a conda env and a requirements.txt? I mean, it could first install the conda env and then run pip install -r requirements.txt within that env.

[humitos]

Running the pip install after the conda env was created and configured shouldn't be a problem at all, I think. Conda support is kind of a new feature in RTD and the core developers don't have too much experience on this topic. So, help on this and a PR with this change would be appreciated for sure.

[stsewd]

Here is the relevant code, and looks like there is an explanation about this issue there.

https://github.com/rtfd/readthedocs.org/blob/393e31ad3a9aafee297df64f1a654ffcda7ef04a/readthedocs/doc_builder/python_environments.py#L369-L372

[goerz]

It would work to to put a URL in the pip sub-section of depencencies in the conda env file, except that the RTD built process calls pip install --ignore-installed ... later on. That means it will complain about any pip packages it can't find on PyPI, even though they're already installed in the conda environment!

[humitos]

I wouldn't add another way to install pip requirements in conda if there is already a way to do it, more maintained, contained in the YAML file and it's standard.

Please, if you think that this is a blocker for your project to build on RTD make a new comment of feel free to reopen explaining the situation. Thanks!

[stsewd]

#2776 (comment)

About that we have #5545

[stsewd]

Also reading https://www.anaconda.com/using-pip-in-a-conda-environment/, looks like we shouldn't use pip at all when using conda