bpo-35328: Always set VIRTUAL_ENV_PROMPT at venv activation

[mafredri]

This is a follow-up to GH-21587 and modifies the behavior so that VIRTUAL_ENV_PROMPT is always set.

The change is needed because VIRTUAL_ENV_PROMPT is being conditionally set only if VIRTUAL_ENV_DISABLE_PROMPT is unset. Shell prompts must set VIRTUAL_ENV_DISABLE_PROMPT to non-empty to prevent venv from hijacking PS1. I'm one of the maintainers of the Pure prompt for zsh, and for us it would be great if VIRTUAL_ENV_PROMPT could always be set, just as VIRTUAL_ENV is too.

No news added since this PR is true to the news written in GH-21587.

https://bugs.python.org/issue35328

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[MaxwellDupre]

I have tried this with 3.11.0.a4 with this branch and I cant get it to work with either
virtualenv venv --prompt '(wat)'
or
python -m venv --prompt '(wat)' ./venv

I notice that there are files for activate csh and fish, hence why don't you make this work with a activate.zsh. Also, there are other scripting solutions on stackExchange:
https://unix.stackexchange.com/questions/87062/how-to-display-the-name-of-the-current-virtualenv

However, if your solution does work please show results in Issue35328

[mafredri]

I have tried this with 3.11.0.a4 with this branch and I cant get it to work with either virtualenv venv --prompt '(wat)' or python -m venv --prompt '(wat)' ./venv

What doesn't work?

I notice that there are files for activate csh and fish, hence why don't you make this work with a activate.zsh. Also, there are other scripting solutions on stackExchange: https://unix.stackexchange.com/questions/87062/how-to-display-the-name-of-the-current-virtualenv

The Stack Exchange post does not address the issue that this PR is trying to amend, which is to make the custom prompt available via environment variable even if disable prompt is enabled.

[MaxwellDupre]

I have recently updated my clone and checked out your PR:

Then running a zsh with python -m venv .venv --prompt env

I get

I see % prompt but expected (wat) %

Also, I note that virtualenv is not core cpython but a pypi package..

[mafredri]

@MaxwellDupre are you saying the behavior is different without this patch? This PR does not touch anything that affects displaying of the virtualenv name in the prompt.

[MaxwellDupre]

Ah, ok. Then looks ok to me.

[sguth-affirm]

Bump, ran into an issue today where I needed this env. variable set despite the presence of VIRTUAL_ENV_DISABLE_PROMPT. Any chance it can get merged?