Implement VIRTUAL_ENV_DISABLE_PROMPT or something covering the same use case(s)

[Russell-Jones]

See https://virtualenv.pypa.io/en/stable/reference/#configuration

Handy if, e.g. installing and running xonsh in a VE using --system-site-packages. The prompt is displayed by xonsh, so I guess it'd need to be set in environ.py, but I'm not sure whether it would be best as a change to env_name() or to the prompt templates when env['VIRTUAL_ENV_DISABLE_PROMPT'] is set to anything but ''. The original reportedly prevents activate from modifying the shell prompt, but I can't see a direct equivalent to that (xonsh can't parse or do clever sub-shell things with bash/zsh/*sh prompt strings can it?).

[melund]

The function that sets the environment part of the prompt is here:

xonsh/xonsh/environ.py

Line 1120 in 3d9e844

def env_name(pre_chars='(', post_chars=') '):

I guess it could just check that environement variable exist:
if builtins.__xonsh_env__.get('VIRTUAL_ENV_DISABLE_PROMPT','') != '': and then not set the environment prompt.

[Russell-Jones]

Yes, but should it do it in the prompt template(s) or in env_name()? Is the output of env_name() exposed anywhere? Perhaps the difference in semantics is sufficient that there should be an xonsh specific env var with the closest functionality available.

Hm. Or perhaps display a message saying how to alter your prompt so it doesn't include the virtualenv name if your prompt template contains {env_name}? I need to look more closely at how prompts are specified.

Here's where it was added to virtualenv (not super enlightening that I could see) pypa/virtualenv#5

[melund]

env_name() is the functions that provide the environment name that is inserted into the PROMPT template. I am not familiar with how Virtualenv works but think this should be enough.

[gforsyth]

Question: it seems like VIRTUAL_ENV_DISABLE_PROMPT comes into play at the time of env creation, is this the behavior we want to enable? Or do we want a general blanket "if this env var is set, don't change the prompt"?

[Russell-Jones]

@gforsyth It's not at env creation, but at env activation.

[gforsyth]

I don't use virtualenv and can't test this right now, but the documentation you linked to in the initial post indicates otherwise:

VIRTUAL_ENV_DISABLE_PROMPT

Any virtualenv created when this is set to a non-empty value will not have it’s activate script modify the shell prompt.

But I would not be surprised if the docs were out-of-date / incomplete / wrong.

[Russell-Jones]

I managed to get the effect I wanted with

import os
$FORMATTER_DICT['env_name']=lambda: '' if os.path.basename($VIRTUAL_ENV) == 'myve' else '('+os.path.basename($VIRTUAL_ENV)+')'

Though I could have used the even more succinct $FORMATTER_DICT['env_name']=''
I've put this in ~/.xonshrc and it works fine AFAIAC (I might add sys and a few others there too), so closing.