Migrate tox.ini to pyproject.toml?

[nstarman]

What is the problem this feature will solve?

One fewer config file.

Describe the desired outcome

https://tox.wiki/en/latest/config.html#pyproject-toml

copy-paste from tox.ini to pyproject.toml

Additional context

Trying to assess the pros and cons.

[astrofrog]

My initial reaction is no - tox.ini is quite long/complex as-is, and having one giant config file for everything won't necessarily help readability. After all, when it comes to Python code we encourage splitting up to avoid very long files!

[mhvk]

Since tox is quite specifically for testing, I also think it is best kept separate. This even more so since the only way right now to include the information in pyproject.toml is as one giant string.

That said, it may pay to look if there is duplicated information.

[namurphy]

My inclination would be to keep tox.ini separate. Putting the tox config into pyproject.toml would have the .ini content in a string called legacy_tox_ini, and I'm not sure that .ini syntax highlighting or linters would work with all IDEs if it is embedded in a TOML file. If we could get away from the .ini format (my least favorite part about using tox) and have the configuration in TOML instead, then it'd be much more tempting to put the tox configuration in pyproject.toml.

[A side note: I've been considering switching PlasmaPy from tox to nox because the configuration for nox is written in Python (https://github.com/PlasmaPy/PlasmaPy/issues/1734).]

[nstarman]

I used nox mostly as well and like it better thus far.