New pip list column: Editable project location

[sbidoul]

What's the problem this feature will solve?

When running pip list, the location field/column contains the location where the project is installed.
It is, roughly, the parent directory of the .(egg|dist)-info directory.

When running pip list, (or pip freeze, see also #10243), we are mainly interested in the project directory, not the metadata directory.

With setuptools editables, the issue is not acute, because the .egg-info directory is in or below the project directory.
With PEP 660 editables, the metadata directory is in the the target environment and that location does not help finding the project directory.

Describe the solution you'd like

I propose adding a new column / json field in pip list output, named Project location / project_location.
The Location column keeps the same meaning but is only displayed in verbose mode.
The Project location column is only displayed when there are editable distributions.

Alternative Solutions

None

[sbidoul]

This would be an alternative to #7670 to close #7664.

[uranusjr]

Maybe we should deprecate Location and add two new fields Metadata Location and Module Location. Both Location and Project Location are confusing names to me, and I don't think I would be able to tell which is which if you ask me an hour later.

[sbidoul]

Module location does not make me immediately think to the directory containing pyproject.toml ? At least less so than Project location ?

[sbidoul]

My post was possibly unclear: location is not the metadata directory but its parent (in most case, if we exclude zip distributions).

[uranusjr]

My mental model for metadata directory is "the directory that contains the metadata directory", and same goes for module directory. "Module" is definitely still not a very good name, but project is also ambiguous (and not a word we use much in the UI right now?) For pure-Python projects maybe "source distribution" makes sense, but not for packages installed from a binary wheel. Naming is hard…

[sbidoul]

So in #10249 I'm naming the new column Editable project location (editable_project_location in the json output).

The default column output has therefore some changes in column titles (Location becomes Editable project location in non-verbose mode, and there is a new optional Editable project location column in verbose mode). I hope this has not to be considered a breaking change. I preserved the column order, in case anyone tried to parse the column output...

In the json output, there is a new field editable_project_location that only appears for editable projects. There is a minor breaking change in the sense that the location field that was output in verbose mode for all items or for editable projects only in non-verbose mode, is now only output in verbose mode. So people who relied on running pip list --format=json in non verbose mode to detect editable installs will need to change to rely on editable_project_location.

I think this is a good compromise, but I'm open to alternatives, of course.

[updated: there is no breaking change]

[sbidoul]

Updated previous comment, as there is actually no breaking change as the existing json fields do not change semantics at all.