Using PIP_NO_CACHE_DIR raises exception

[rhcarvalho]

This is related to #2855 and #2856.
#2856 fixed the exception when using --no-cache-dir flag, but using the equivalent env var still doesn't work:

$ PIP_NO_CACHE_DIR=1 pip install gunicorn
Exception:
Traceback (most recent call last):
  File "/usr/lib/python3.3/site-packages/pip-7.0.3-py3.3.egg/pip/basecommand.py", line 223, in main
    status = self.run(options, args)
  File "/usr/lib/python3.3/site-packages/pip-7.0.3-py3.3.egg/pip/commands/install.py", line 242, in run
    with self._build_session(options) as session:
  File "/usr/lib/python3.3/site-packages/pip-7.0.3-py3.3.egg/pip/basecommand.py", line 71, in _build_session
    if options.cache_dir else None
  File "/usr/lib64/python3.3/posixpath.py", line 82, in join
    elif not path or path.endswith(sep):
AttributeError: 'int' object has no attribute 'endswith'

[dstufft]

I think you want PIP_NO_CACHE_DIR=off.

[rhcarvalho]

Thanks for your reply, @dstufft.

$ PIP_NO_CACHE_DIR=off pip install gunicorn
Collecting gunicorn
  Downloading gunicorn-19.3.0-py2.py3-none-any.whl (110kB)
    100% |████████████████████████████████| 110kB 1.7MB/s 
Installing collected packages: gunicorn
Successfully installed gunicorn-19.3.0

However, what does "no cache dir = off" mean? I understand it means to use the cache dir... so I double check that it is caching:

$ PIP_NO_CACHE_DIR=off PIP_CACHE_DIR=the-cache pip install django
Collecting django
  Downloading Django-1.8.2-py2.py3-none-any.whl (6.2MB)
    100% |████████████████████████████████| 6.2MB 91kB/s 
Installing collected packages: django
Successfully installed django-1.8.2
$ tree the-cache/
the-cache/
└── http
    ├── 1
    │   └── d
    │       └── 6
    │           └── 4
    │               └── 5
    │                   └── 1d64584e92602feb17a86d9818a6020c216c9a04bcf58fb91c2f5a13
    └── c
        └── d
            └── 1
                └── 5
                    └── 9
                        └── cd159833e45a286ff17af3902a2d935061be9d24f93f9b256bca9387

11 directories, 2 files

But what I want is to disable the cache... and that doesn't work still:

$ PIP_NO_CACHE_DIR=on pip install gunicorn
Traceback (most recent call last):
  File "/home/rodolfo/.virtualenvs/tmp-151361bc365703be/bin/pip", line 11, in <module>
    sys.exit(main())
  File "/home/rodolfo/.virtualenvs/tmp-151361bc365703be/lib/python2.7/site-packages/pip/__init__.py", line 217, in main
    return command.main(cmd_args)
  File "/home/rodolfo/.virtualenvs/tmp-151361bc365703be/lib/python2.7/site-packages/pip/basecommand.py", line 219, in main
    timeout=min(5, options.timeout)) as session:
  File "/home/rodolfo/.virtualenvs/tmp-151361bc365703be/lib/python2.7/site-packages/pip/basecommand.py", line 71, in _build_session
    if options.cache_dir else None
  File "/home/rodolfo/.virtualenvs/tmp-151361bc365703be/lib64/python2.7/posixpath.py", line 70, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'int' object has no attribute 'endswith'

IIRC PIP_NO_CACHE_DIR=on is equivalent to PIP_NO_CACHE_DIR=true and PIP_NO_CACHE_DIR=1 (what I had in the original issue description).

[dstufft]

PIP_NO_CACHE_DIR=off disables the cache, it's a confusing option that happens that way because of the way we automatically translate cli flags into environment variables.

[rhcarvalho]

Oh, so then in the presence of both PIP_NO_CACHE_DIR=off and PIP_CACHE_DIR=the-cache, setting the cache-dir takes precedence and makes pip cache downloaded packages?

[gst]

I was having, right now, the same exception with the same backtrace but without specifying any of these env variables.
But I was having the failure from time to time .. I could launch "pip install -r requirements.txt" 3 times in a row and don't get the failure, and on the 4th time it'd occur.. or any combination of failure/success .. :s

I put a pdb.set_trace at the line 82 and could see that effectively the path value was 1 (the int, not the str).. after verify of my pip settings I've seen I had in my pip.conf : "no-cache-dir = true" ; changed it to "no-cache-dir = off" and there it's good..

But why was it failing sometimes and sometimes not :-?

[rhcarvalho]

Tested this again on a temporary virtualenv, seems that all positive values (1, true, on, yes) for PIP_NO_CACHE_DIR cause the same error, while negative values (0, false, off, no) cause no errors, but I still couldn't verify whether the cache is disabled or enabled when I use PIP_NO_CACHE_DIR=0. Isn't it the same as not specifying the variable at all?!

$ pip list
pip (8.1.2)
setuptools (12.0.5)
(tmp-368ff30f354a8052) ✔ ~/openshift/src/github.com/openshift/source-to-image [master|…5⚑ 4] 
22:34 $ PIP_NO_CACHE_DIR=1 pip install gunicorn
Exception:
Traceback (most recent call last):
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages/pip/commands/install.py", line 249, in run
    with self._build_session(options) as session:
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages/pip/basecommand.py", line 69, in _build_session
    if options.cache_dir else None
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib64/python2.7/posixpath.py", line 70, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'int' object has no attribute 'endswith'
Traceback (most recent call last):
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/bin/pip", line 11, in <module>
    sys.exit(main())
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages/pip/__init__.py", line 221, in main
    return command.main(cmd_args)
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages/pip/basecommand.py", line 251, in main
    timeout=min(5, options.timeout)) as session:
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages/pip/basecommand.py", line 69, in _build_session
    if options.cache_dir else None
  File "/home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib64/python2.7/posixpath.py", line 70, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'int' object has no attribute 'endswith'

$ PIP_NO_CACHE_DIR= pip install gunicorn
Requirement already satisfied (use --upgrade to upgrade): gunicorn in /home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages
$ PIP_NO_CACHE_DIR=0 pip install gunicorn
Requirement already satisfied (use --upgrade to upgrade): gunicorn in /home/rodolfo/.virtualenvs/tmp-368ff30f354a8052/lib/python2.7/site-packages

[asobrien]

If you explicitly want pip to use a cache-dir (e.g., PIP_NO_CACHE_DIR={1,true,on,yes}) then a cache-dir must be explicitly set as well (e.g., PIP_CACHE_DIR=/tmp/). The exception that is raised in the absence of the cache-dir option stems from here: https://github.com/pypa/pip/blob/master/pip/basecommand.py#L67

Note that, pip uses falsy values to enable boolean options like --no-compile and --no-cache-dir (https://pip.pypa.io/en/stable/user_guide/?highlight=falsy#configuration)

[rhcarvalho]

@asobrien thank you very much. I'm closing this as a usage error, thanks for pointing out the docs.

[brechtm]

For what it's worth, I'd like to say that is very confusing behaviour. Setting PIP_CACHE=0 to disable the cache would make sense, but having to set PIP_NO_CACHE_DIR=0 to enable no-cache-dir is just ludicrous.