Have pre and post test run in config

[pytoxbot]

New summary:

Plugins can already run pre and post test commands via https://tox.readthedocs.io/en/latest/plugins.html#tox.hookspecs.tox_runtest_post and https://tox.readthedocs.io/en/latest/plugins.html#tox.hookspecs.tox_runtest_pre. We should allow users to add this inside their config file too, so they don't have to create tox plugins for one time behaviours (e.g. setup/cleanup operations of dependencies).

[pytoxbot]

Original comment by @hpk42

For the record, i am open to support and/or maybe take advantage of conda with tox. I don't know too much about conda so would be glad to hear a proposal what would need to be added exactly, preferably in the form of a documentation PR that explains the new "tox conda" integration which could then become the eventual documentation for it.

[pytoxbot]

Original comment by @hayd

Using conda instead of virtual env would definitely be the preferred solution here. For one thing running tox --conda (or something) could just conda install the correct python version and "just work"... no more InterpreterNotFound errors.

[pytoxbot]

Original comment by @kmike

At conda mailing list it was suggested to add direct conda support to tox - add an option to create conda environments instead of virtualenv environments. conda inside virtualenv actually doesn't always work well, there are issues with shared C libraries and other issues.

[pytoxbot]

Original comment by @hayd

+1 for conda support would be really handy.

[pytoxbot]

Original comment by @wreszelewski

Another use-case may be if someone want to play around with requirements.txt - generate it or edit using some script.

[pytoxbot]

Original comment by @kmike

Another reason why using install_command is hard is that conda itself must be installed into virtualenv. I created a script that can be used as an install_command:

#!/usr/bin/env python

if __name__ == '__main__':
    import sys
    import os
    import subprocess

    for package in sys.argv[1:]:
        if os.path.isfile(package):
            cmd = "pip install " + package
        elif package == 'conda':
            cmd = "pip install conda; conda init"
        else:
            cmd = "conda install --yes " + package
        print(cmd)
        subprocess.call(cmd, shell=True)

but it looks like a hack.

[obestwalter]

I liek that - I think a PR implementing that (also providing the necessary hooks for plugins), would likely be merged.

[adamrothman]

Just wanted to add another data point. I have a package (asyncpg) that I currently need to build from source because I need features that are not yet available in an official release. This requires me to have Cython installed, and simply adding Cython to my deps section doesn't work (neither does adding it to my requirements.txt).

Instead I have to trick tox, using the deprecated indexserver config option to make it think it's installing from a different index server (credit to https://stackoverflow.com/a/50081741/897652):

[tox]
envlist = py36
indexserver =
    preinstall = https://pypi.org/simple/


[testenv]
deps =
    :preinstall: Cython
    coverage
    flake8
    mypy
    pytest
    pytest-asyncio
    pytest-cov
    -rrequirements.txt
commands =
    flake8 railtie tests
    mypy --ignore-missing-imports railtie tests
    pytest --cov={envsitepackagesdir}/railtie {posargs} tests/unit tests/api

It would be really great to have an officially-supported way to do this – especially before indexserver is removed altogether.

[gaborbernat]

@adamrothman cython is a build dependency, your problem solution will be adding PEP 517/518 support, tracked by #573