Add pip freeze option to report local directory instead of VCS link

[cwiede]

This is a follow up on #4300 which has been automatically locked.

I was tricked by this as well and I am not sure about the reasoning about why pip freeze wants to be super smart and changes the location of a pip install -e to a version control path. Is there some way to turn this behaviour off via command line?

If I would want to specify a version controlled package in the pip freeze output, then I could simply use

pip install -e git+ssh://<package>

to install the package. If instead I use

pip install -e ./some/relative/local/path

I find it very strange that this path is suddenly replaced by a completely different path to a version control system.

Automatically converting local paths to version control paths is a bad idea in my opinion and it actually breaks the usability of pip freeze for us. Converting the path back to a local path afterwards is pretty much impossible, but it is necessary in our infrastructure.

[pradyunsg]

As noted in that thread, there's no way for pip to distinguish between a pip install from a local checkout vs pip install from a VCS URL.

It's not that pip freeze is trying to be smart or anything, it's that there's no information available to distinguish between the two cases.

[cwiede]

Ok, I worked around this by ignoring "-e" packages in our requirement file / freeze file checks. I still feel that a choice should be given to the user whether the conversion shall be done or not.

[uranusjr]

Would PEP 610 have an effect (positive or negative) to this issue @sbidoul? The only time pip has this information is on install-time, and the extra storage would be a chance to set this correctly.

[sbidoul]

@uranusjr PEP 610 does have an effect on this issue, albeit indirect.

Actually, providing a VCS url to -e must be seen as a shortcut for git clone project && pip install -e ./project. That's the way pip works today and I assume it will stay this way.

For editable installs, PEP 610 says the local project directory must be recorded in direct_url.json (the editable flag is in the dir_info structure). The reasoning is that editable is meant for 'development mode', and the important part for that is the local project location.

So the way I see it is that pip freeze is indeed trying to be smart with editable installs to workaround the absence of PEP 610. When #7612 is merged, we can start encouraging people not to use -e anymore for the purpose of making pip freeze work with VCS URLs.

Under that light, this issue makes sense, and we will probably want to have a way for pip freeze to emit the project location and not try to infer the VCS url. Of course there will be the question of backward compatibility or if we want to add a new option etc.