Restore pip freeze after pip install

[adrien-berchet]

Fixes #2685

This is just an attempt to restore a very useful old behavior: printing the actual versions of the dependencies installed in the virtual environment. If this is the proper way to fix it, I will add tests, docs, etc.
WDYT @gaborbernat (or anyone else 😄 )?

Notes

• The installed method uses the self._env.execute which make it difficult to format the output, so it displays a list like:

a==1.2.3
b==2.3.4
c==3.4.5

instead of the former one-line format:

a==1.2.3,b==2.3.4,c==3.4.5

• For now I set show=True but maybe we want it to be customizable by the user.

Thanks for contribution

Please, make sure you address all the checklists (for details on how see
development documentation)!

• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[gaborbernat]

Please read in the issue my comments in which form I'd accept this, and do accordingly.

[adrien-berchet]

Well, your comment is a bit short for someone like me that discovers the tox internals 😅
But I added a flag so now if we want to list the deps we have to call the following command: tox run -e py38 --display-dependencies. Is it what you have in mind?

[gaborbernat]

Not really. I've said this should be on in CI envs and otherwise off.

[jugmac00]

From just this week's experience.. debugging issues when the behavior is different locally in and in CI is a pain.

I am +1 for the attempt @adrien-berchet is suggesting.

[gaborbernat]

We can keep the flag just the default value should change by CI env. I'm strong -1 on making this on by default locally.

[adrien-berchet]

I am not sure I get your point @gaborbernat , in this current patch the default behavior is not changed, the user has to specify --display-dependencies to enable the new behavior (the show=True does not mean it will always be displayed, it just means that when the --display-dependencies is passed the deps are displayed regardless of the verbosity level). So in the CI we can pass this --display-dependencies argument and locally it's also possible to pass this argument if the user has any reason to do it, but by default it will not change anything.

[gaborbernat]

Why do we need this, considering https://github.com/tox-dev/tox/blob/main/src/tox/tox_env/python/api.py#L216. Shouldn't we be reusing that call?

[gaborbernat]

This is python specific so I don't see why it would leave under the generic runner and not the python scope.

[gaborbernat]

So in the CI we can pass this --display-dependencies argument and locally it's also possible to pass this argument if the user has any reason to do it, but by default it will not change anything.

I'd argue in the CI envs we should do this without the user passing any flags. And that was my threshold of acceptability in the issue. Locally the user can still use the flag, if they want.

[gaborbernat]

Superseded by #2794

[adrien-berchet]

I just discovered #2784, it seems very nice!
I just think it could be useful to add some doc about this behavior and how to trigger it manually (e.g. just by defining a environment variable called CI).
Thank you very much @gaborbernat !