conda bin_paths are missing Library\... subdirectories on windows

[thatcr]

Describe the bug

When running python code that requires external executables from conda packages - i.e. ipopt, they cannot be found on the PATH.

How to reproduce

This noxfile fails - it should find 'ipopt.exe' on the PATH:

import nox

@nox.session(python="3.7", venv_backend="conda")
def conda_path_bug(session):
    session.conda_install("conda-forge::ipopt==3.11.1")  
    session.run("python", "-c", "import shutil; assert shutil.which('ipopt')")

Expected behavior

The PATH should be set to include the same entries as Anaconda's cwp.py provides:

new_paths = pathsep.join([prefix,
                         join(prefix, "Library", "mingw-w64", "bin"),
                         join(prefix, "Library", "usr", "bin"),
                         join(prefix, "Library", "bin"),
                         join(prefix, "Scripts")])
env = os.environ.copy()
env['PATH'] = new_paths + pathsep + env['PATH']
env['CONDA_PREFIX'] = prefix

[cjolowicz]

Thanks for reporting this, makes sense.

IIUC we should emulate the way conda activate changes the environment variables. What would be a portable and maintainable way to do this?

[cjolowicz]

If you'd like to have a go at this, take a look at CondaEnv.bin_paths:

https:/theacodes/nox/blob/441b2bc666e209757bdccafd647083493e14c1cc/nox/virtualenv.py#L218-L225

The bin_paths are used to locate the commands passed to session.run:

https:/theacodes/nox/blob/441b2bc666e209757bdccafd647083493e14c1cc/nox/sessions.py#L360

[Tolker-KU]

Is a viable solution simply to hardcode the correct paths into the .bin_paths property in CondaEnv? The advantage of this approach is that it is easy to implement and very transparent.

Another approach is to hook into Conda in some way to retrieve the correct paths but this would be a lot more cumbersome to implement.

Both approaches are probably equally exposed to Conda changing something in its internals, so the simple approach seems more attractive to me.

Any thoughts on this?

[thatcr]

Thank you for this - I have just confirmed that 2022.1.7 fixes the original issue.

More generally - conda activate can run arbitrary scripts from etc/conda/activate.d so the PATH modification isn't a complete solution, but probably works for 99.9% of packages.

Wrapping any calls to session.run or session.install with conda run --prefix <prefix> <cmd> would probably be the right (cross platform) way, since that deals with the mechanics of shells and activation before running the command.

The behaviour of conda activate is dependent on which packages are currently installed, and some do modify the PATH in a bespoke way, so it would be wrong to run once to extract the environment variables and then cache them for later.

[Tolker-KU]

Happy to help 🙂

As far as I know the conda run feature is still experimental, so using it in Nox is maybe questionable?

I hope this fix works for (almost) everything as you mentioned. If that is not the case we can reconsider how to solve this.

[smarie]

Great job guys ! Indeed, I had only added the Scripts folder originally, it was definitely not complete :(

I like the conda run --prefix idea, this is definitely something to follow if the feature becomes official.