Can't override require-virtualenv config option via CLI

[justinmayer]

Environment

• pip version: 10.0.1
• Python version: 2.7.14
• OS: macOS 10.13.5

Pip bundled along with Homebrew Python, subsequently upgraded to 10.0.1

Description
I always want pip install to require an activated virtual environment, unless I override that default on a per-invocation basis. In Pip 9.x it was possible to override the require-virtualenv default via the PIP_REQUIRE_VIRTUALENV environment variable, but Pip 10 does not respect that environment variable nor seem to provide any way to override require-virtualenv on a per-invocation basis.

Expected behavior
I expected Pip to respect the PIP_REQUIRE_VIRTUALENV environment variable and/or provide some other way to override the require-virtualenv setting.

How to Reproduce
With a Pip configuration file including:

[install]
require-virtualenv = true

... override via environment variable and install the desired package to global site-packages:

env PIP_REQUIRE_VIRTUALENV="" pip install some-package-I-want-in-global-site-packages

Output
The above command behaved as expected up until Pip 10. When I attempt this on Pip 10, however, the PIP_REQUIRE_VIRTUALENV environment variable does not appear to be honored. Instead, an error is returned:

Could not find an activated virtualenv (required).

Additional Notes
If there is a flag or some other way to override the require-virtualenv setting on a per-invocation basis, I cannot find it and would appreciate a pointer to its existence. Otherwise, I would prefer and humbly request that the ability to do so be restored in some manner or other.

[moshez]

I can confirm this is a regression:

moshez@mcgyver:~/src/pybay-2018-web-a-to-z$ env PIP_REQUIRE_VIRTUALENV='' pip install --upgrade pip
Collecting pip
  Downloading http://localhost:3141/root/pypi/+f/717/cdffb2833be84/pip-10.0.1-py2.py3-none-any.whl (1.3MB)
    100% |████████████████████████████████| 1.3MB 43.0MB/s 
Installing collected packages: pip
  Found existing installation: pip 9.0.1
    Uninstalling pip-9.0.1:
      Successfully uninstalled pip-9.0.1
Successfully installed pip-10.0.1
moshez@mcgyver:~/src/pybay-2018-web-a-to-z$ env PIP_REQUIRE_VIRTUALENV='' pip install --upgrade pip
Could not find an activated virtualenv (required).

[moshez]

moshez@mcgyver:~/src/pip$ env PIP_REQUIRE_VIRTUALENV='0' PYTHONPATH=src python -m pip install twisted
Looking in indexes: http://localhost:3141/root/pypi/+simple/

Apparently using =0 is the right behavior. I don't know if we want to keep treating an empty string as 0.

[moshez]

@justinmayer to your question -- just use =0 and it should be ok!

[moshez]

https://github.com/pypa/pip/blob/master/src/pip/_internal/baseparser.py#L158 -- explicitly ignore empty values

[moshez]

And just to finalize the saga -- when it is not empty, it uses strtobool.

"True values are y, yes, t, true, on and 1; false values are n, no, f, false, off and 0. Raises ValueError if val is anything else."

On invalid values, it will traceback:

$ env PIP_REQUIRE_VIRTUALENV='blah' PYTHONPATH=src pytho
n -m pip install twisted                                                       
Traceback (most recent call last):                                             
  File "/home/moshez/.pyenv/versions/3.6.4/lib/python3.6/runpy.py", line 193, in
 _run_module_as_main                                                           
...
    values = self.get_default_values()
  File "/home/moshez/src/pip/src/pip/_internal/baseparser.py", line 230, in get_default_values
    defaults = self._update_defaults(self.defaults.copy())  # ours             
  File "/home/moshez/src/pip/src/pip/_internal/baseparser.py", line 195, in _update_defaults
    val = strtobool(val)
  File "/home/moshez/.pyenv/versions/3.6.4/lib/python3.6/distutils/util.py", line 317, in strtobool
    raise ValueError("invalid truth value %r" % (val,))                        
ValueError: invalid truth value 'blah'

[pradyunsg]

I don't know if we want to keep treating an empty string as 0.

No. I don't think setting PIP_REQUIRE_VIRTUALENV="" was ever a good way to do this. Boolean options are a little weird to deal with and how-to-use-them should probably get documented in the documentation.

---

pip clearly needs to print a better error message when the environment variable is not set correctly -- @moshez could you check if there's an existing issue for it otherwise file a new issue for this?

[moshez]

Hi @pradyunsg, I opened #5616 -- I did some searching and did not see an existing issue. Will you manage the state of this ticket and #5616 ? I don't know if this one is supposed to be closed or something.

[pradyunsg]

I opened #5616

Thanks! ^>^

Will you manage the state of this ticket and #5616?

Yeah; I'll keep this open to track a documentation change -- we should document how boolean options behave when used via environment variables. The other issue would serve to track changing to print a better error message when we get "blah" values. :P

[pradyunsg]

This issue is a good starting point for anyone who wants to help out with pip's development -- it's simple and the process of fixing this should be a good introduction to pip's development workflow. See the discussion above to understand what the desired fix is.

Feel free to mention me (write @pradyunsg in the comment) if you need help with something. :)

[SummerGram]

@pradyunsg
Is it closed?

[pradyunsg]

This ticket is open @SummerGram. Would you like to work on this?

[SummerGram]

@pradyunsg but I can't find PIP_REQUIRE_VIRTUALENV this variable

[lakshmanaram]

Is this issue still relevant to the current codebase?

[pradyunsg]

@lakshmanaram Yes.

Apologies for the delay in responding. I've been swamped by GitHub notifications since I was AWOL for a couple of weeks since the sprints.

pip's configuration code automatically translates option for CLI into environment variables when checking. I'm a little short on time to find the exact links to lines of currently -- the relevant code is in pip._internal.configuration, pip._internal.cli.cmdoptions and users of options.require_virtualenv.

[Divya063]

@pradyunsg I would like to work on this issue.

[pradyunsg]

Looks like this got fixed at some point. From https://pip.pypa.io/en/stable/user_guide/#environment-variables:

Environment variables set to be empty string will not be treated as false. Please use no, false or 0 instead.

---

@Divya063 Hi! Would you be willing to try solving a different issue? Perhaps #7804?