pip freeze does not list repo url

[DataGreed]

Here's the detailed problem: http://stackoverflow.com/questions/11560056/pip-freeze-does-not-show-repository-paths-for-requirements-file

[qwcode]

pip's ability to discern where the install came from is limited after the fact using pip freeze.
pip internally relies upon setuptools to find all the installed distributions.
pip then checks to see if any of them are "editable"/-e vcs installations.
if editable, then it will print out the vcs url.
if not editable, then just the name=version spec.

btw, since you asked about "-e" in the stack link, "-e" or "editable" is an enhancement of what setuptools called a "develop" install. this is an "installation" that does not occur via copying packages into site-packages.
but rather a link of sorts is made in site-packages back to the source location of the project.
that way you can "develop" or "edit" the project live while it's installed.
for "-e" vcs installs, pip uses a "src" subdirectory of the virtualenv or sys.prefix to clone the project.
if you install from a vcs url w/o "-e", pip builds a distribution locally and installs from that, and at that point pip freeze (i.e. setuptools) doesn't know it came from vcs.

[xavfernandez]

A typical example is given in #4005.

$ pip install git+https://github.com/chadmiller/textbot_metapriv.git#egg=textbot_metapriv   # a private package that will never be in PyPI
$ pip freeze |grep bot
textbot-metapriv==1.0

[pradyunsg]

@xavfernandez is this still an issue?

[pradyunsg]

is this still an issue?

Yes.

[sbidoul]

What's the problem this feature will solve?

Abstract: this issue is becoming more acute now that pep517 is a thing and it does not support editable installs.

When installing vcs dependencies without --editable, the exact installed version is lost when subsequently doing a pip freeze. When installing with --editable, it is preserved.

Preserving the installed vcs reference is actually my main (if not only) use case for using --editable.

My problem today is that pep517 does not support --editable, so if I want to pip install from vcs a pep517 project which has no setup.py, I loose the ability to do a reliable pip freeze.

Here is an example installing a pep517 project in a virtualenv (flit):

$ mktmpenv -p python3
$ pip install git+https://github.com/takluyver/flit.git
$ pip freeze
certifi==2019.3.9
chardet==3.0.4
docutils==0.14
flit==1.3
idna==2.8
pytoml==0.1.20
requests==2.21.0
urllib3==1.24.1

So with this method, I loose the information about the exact flit commit installed, and pip freeze does not give me something reproducible.

If I try with -e, it fails because pip install -e assumes setuptools is present:

$ mktmpenv -p python3
$ pip install -e git+https://github.com/takluyver/flit.git#egg=flit
[...]
Installing collected packages: certifi, chardet, urllib3, idna, requests, pytoml, docutils, flit
  Running setup.py develop for flit
    Complete output from command /home/sbi/.virtualenvs/tempenv-04f816243221f/bin/python3 -c "import setuptools, tokenize;__file__='/home/sbi/.virtualenvs/tempenv-04f816243221f/src/flit/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" develop --no-deps:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    ModuleNotFoundError: No module named 'setuptools'

Describe the solution you'd like

I understand adding editable support to pep517 is a hard problem. Perhaps it is not needed for this use case, and a simpler approach would be to have pip preserve the installed vcs reference somewhere to restitute it in pip freeze?

I'm willing attempt a PR, but I'm not sure where pip could store this information, assuming such a place exists at all today? Could someone give me some guidance as to where to start?