I personally would like to remove it completely. I need to think what's a better solution to the problem though. I don't think it's tox problem to solve index server abstractions. People should use devpi for that with some option to pass in the index server via PIP_INDEX_URL env var.

Having to pass in something rather than being able to configure it in the tox.ini is not a desirable alternative IMO. Behind corporate firewalls this is a very useful feature to set the index to the internal pypi mirror for everyone rather than having to tell everyone they have to call with some special env var set.

You can use setenv to set that env var in tox.ini. That's what we do at our company and works like a charm.

I just tested it and I think setenv with PIP_INDEX_URL is a good solution. According to the docs it is used for setup and test run. This just needs to be documented prominently so it's easy to find and there should be a deprecation message pointing to the docs when the option is used in the config. Not sure about the command line option though. It doesn't seem to be deprecated, but also only seems to pass on one index straight to pip.

One problem I just thought about is that you can't overwrite PIP_INDEX_URL from the command line or via CI environment variables, but that may already be the case right now.

We can change the default pip command to auto pass through pip index URL from outside env var👌For now we do it explicitly overriding the pip install command inside tox.ini at our company this.

Here's what we use:

install_command = pip install -i {env:PIP_INDEX_URL:https://magic.index.server.address/simple} {opts} {packages}

We should probably just make this as the default and drop the entire indexserver thing. This would keep the installer tool agnostic the index server selection. The main reason for this is that index server is a pip thing, conda/dpkg, for example, doesn't have such. It's a clearer separation of concern if we the tool doesn't know about pips internals; and makes it easier to extend to use other packaging tools.

This allows the user to easily insert their own index server (such as a local devpi mirror index), but fallback to some hardcoded sane value on a per project basis.

This needs a deprecation warning then and a hint how to solve this differently, plus some docs.