pipenv always create new virtualenv if PIPENV_SITE_PACKAGES=1 is set

Issue description

When the environment variable PIPENV_SITE_PACKAGES is set, pipenv always recreate new virtualenv on each invoke of pipenv even if it is not a pipenv install command.

Expected result

• pipenv run or pipenv shell should use existing virtualenv instead of creating a new one.
• PIPENV_SITE_PACKAGES should only affect pipenv install command.

Actual result

root@9e08ac3143d2:/tmp# pipenv && pipenv && pipenv
Warning: the environment variable LANG is not set!
We recommend setting this in ~/.profile (or equivalent) for proper expected behavior.
Creating a virtualenv for this project...
Pipfile: /tmp/Pipfile
Using /usr/bin/python3.8 (3.8.5) to create virtualenv...
Making site-packages available...
⠼ Creating virtual environment...created virtual environment CPython3.8.5.final.0-64 in 254ms
  creator CPython3Posix(dest=/root/.local/share/virtualenvs/tmp-XVr6zr33, clear=False, global=True)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/root/.local/share/virtualenv)
    added seed packages: pip==20.2.4, setuptools==50.3.2, wheel==0.35.1
  activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator

✔ Successfully created virtual environment!
Virtualenv location: /root/.local/share/virtualenvs/tmp-XVr6zr33
Creating a Pipfile for this project...
Virtualenv already exists!
Removing existing virtualenv...
Warning: the environment variable LANG is not set!
We recommend setting this in ~/.profile (or equivalent) for proper expected behavior.
Creating a virtualenv for this project...
Pipfile: /tmp/Pipfile
Using /usr/bin/python3.8 (3.8.5) to create virtualenv...
Making site-packages available...
⠼ Creating virtual environment...created virtual environment CPython3.8.5.final.0-64 in 235ms
  creator CPython3Posix(dest=/root/.local/share/virtualenvs/tmp-XVr6zr33, clear=False, global=True)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/root/.local/share/virtualenv)
    added seed packages: pip==20.2.4, setuptools==50.3.2, wheel==0.35.1
  activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator

✔ Successfully created virtual environment!
Virtualenv location: /root/.local/share/virtualenvs/tmp-XVr6zr33
Virtualenv already exists!
Removing existing virtualenv...
Warning: the environment variable LANG is not set!
We recommend setting this in ~/.profile (or equivalent) for proper expected behavior.
Creating a virtualenv for this project...
Pipfile: /tmp/Pipfile
Using /usr/bin/python3.8 (3.8.5) to create virtualenv...
Making site-packages available...
⠼ Creating virtual environment...created virtual environment CPython3.8.5.final.0-64 in 239ms
  creator CPython3Posix(dest=/root/.local/share/virtualenvs/tmp-XVr6zr33, clear=False, global=True)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/root/.local/share/virtualenv)
    added seed packages: pip==20.2.4, setuptools==50.3.2, wheel==0.35.1
  activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator

✔ Successfully created virtual environment!
Virtualenv location: /root/.local/share/virtualenvs/tmp-XVr6zr33
root@9e08ac3143d2:/tmp#

Steps to replicate

• docker run -it ubuntu bash
• Inside docker: apt update && apt install -y python3 python3-pip && pip3 install pipenv && export PIPENV_SITE_PACKAGES=1
• run any pipenv command, in the example I use pipenv && pipenv && pipenv

---

Pipenv version: '2020.11.15'

Pipenv location: '/usr/local/lib/python3.8/dist-packages/pipenv'

Python location: '/usr/bin/python3'

Python installations found:

• 3.8.5: /usr/bin/python3.8
• 3.8.5: /usr/bin/python3
• 3.8.5: /bin/python3.8
• 3.8.5: /bin/python3

PEP 508 Information:

{'implementation_name': 'cpython',
 'implementation_version': '3.8.5',
 'os_name': 'posix',
 'platform_machine': 'x86_64',
 'platform_python_implementation': 'CPython',
 'platform_release': '5.4.39-linuxkit',
 'platform_system': 'Linux',
 'platform_version': '#1 SMP Fri May 8 23:03:06 UTC 2020',
 'python_full_version': '3.8.5',
 'python_version': '3.8',
 'sys_platform': 'linux'}

System environment variables:

• HOSTNAME
• PWD
• HOME
• LS_COLORS
• TERM
• PIPENV_SITE_PACKAGES
• SHLVL
• PATH
• OLDPWD
• _
• LC_CTYPE
• PIP_DISABLE_PIP_VERSION_CHECK
• PYTHONDONTWRITEBYTECODE
• PIP_SHIMS_BASE_MODULE
• PIP_PYTHON_PATH
• PYTHONFINDER_IGNORE_UNSUPPORTED

Pipenv–specific environment variables:

• PIPENV_SITE_PACKAGES: 1

Debug–specific environment variables:

• PATH: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
• PWD: /tmp

---

Contents of Pipfile (‘/tmp/Pipfile’):

[[source]]
url = "https://pypi.org/simple"
verify_ssl = true
name = "pypi"

[packages]

[dev-packages]

[requires]
python_version = "3.8"

[frostming]

Currently passing --site-packages, the equivalent of setting PIPENV_SITE_PACKAGES, will be regarded as the user wants to change the virtualenv properties. So it is a one-pass flag rather than a persistent setting, but it should be easy to fix: https://github.com/pypa/pipenv/blob/47d8b96e10e462169cb9d3e719318565514408ad/pipenv%2Fcore.py#L519-L546

Any interest in submitting a PR?

[vibhutimishra]

I have tried to run the code on my computer. On running the command “pipenv --three” it shows that virtual environment already exists and then it removes the existing virtual environment and create new one. My doubt is that we have to remove this functionality and add if any virtual environment exists it should use that?