Expose interface to locate a physical .dist-info / .egg-info directory by distribution name

[jaraco]

In GitLab by @uranusjr on Feb 17, 2020, 20:29

#23 discussed whether it’d be possible to make the distribution’s _path attribute public. While I understand the rational behind not exposing it, IMO there are cases when a tool wants to find a distribution on disk. One example would be project tools wanting to perform a “clean” operation that cleans up previously-built package metadata.

Under those circumstances, the need is not to find a Distribution, and then locate it on disk (this does not make sense), but to find a dist/egg-info directory on disk (and then turn it into a Distributon; this is already possible with #90). One way to do that would be to add an interface to do something like

def locate_dist_dir(name):
    for path in MetadataPathFinder._search_paths(sys.path):
        if Distribution.at(path).metadata['Name'] == name:
            yield path

[jaraco]

In GitLab by @jaraco on Mar 9, 2020, 22:34

Yes, I'd like to expose this information. The real trick is describing for other loaders what to present (if anything) for this property.

[jaraco]

In GitLab by @blueyed on Mar 17, 2020, 12:42

Note that using locate() on files is public API already, and might be usable for @uranusjr ?

I also wanted to mention that with https://gitlab.com/python-devs/importlib_metadata/-/merge_requests/114 I've added a new _locate_path, which gets adjusted for src-based egg-info distributions.
I.e. I've thought that _path is good to point to the egg-info still, while it has extra information then about how to locate files (used by locate() then).

[jaraco]

In GitLab by @uranusjr on Mar 28, 2020, 14:24

@blueyed Not sure I get what you mean, the distribution itself is not included in the list returned by file, which is the only API I am aware of that returns PackagePath.

[jaraco]

In GitLab by @jaraco on Jun 14, 2020, 16:25

@uranusjr What would you expect locate_dist_dir to return for a dist that's persisted in an abstract store not on the file system (think SQL database)?

[jaraco]

In GitLab by @uranusjr on Jun 14, 2020, 21:27

Either return None or raise something like FileNotFoundError, since that is not a .dist-info directory.

[jaraco]

In GitLab by @jaraco on Sep 23, 2020, 15:53

the need is not to find a Distribution, and then locate it on disk (this does not make sense), but to find a dist/egg-info directory on disk (and then turn it into a Distributon

I'm afraid I still don't understand the distinction between these two options.

I think what you want here is something like:

def locate_dist_dir(name):
    dist, = metadata.Distribution.discover(name=name)
    return dist._path if isinstance(getattr(dist, '_path', None), metadata.pathlib.Path) else None

Perhaps Distribution could get a get_local_dir() implementing that last line, such that one could:

path = one(metadata.Distribution.discover(name=name)).get_local_dir()

(uses one)

WDYT?

[jaraco]

In GitLab by @uranusjr on Sep 23, 2020, 16:34

The impression I got from from !23 was that exposing _path was considered not a good idea since not all Distribution has a path, so my proposal was to avoid involving Distribution classes at all when locating the metadata directory, and provide a way turn that path into a Distribution object afterwards. The isinstance() and getattr() introspection just feels wrong.

A get_local_dir() method would make sense as well, though. I would be perfectly happy if that’s the interface we go with.

[jaraco]

Under those circumstances, the need is not to find a Distribution, and then locate it on disk (this does not make sense), but to find a dist/egg-info directory on disk (and then turn it into a Distributon; this is already possible with #90). One way to do that would be to add an interface to do something like

def locate_dist_dir(name):
    for path in MetadataPathFinder._search_paths(sys.path):
        if Distribution.at(path).metadata['Name'] == name:
            yield path

Looking at this again, I'm pretty sure _search_paths already does what you need:

locate_dist_dir = functools.partial(MetadataPathFinder._search_paths(paths=sys.path)

I think we have two options.

• add a test to protect the interface of the private _search_paths for select uses.
• expose a new, supported interface.

I think I'll go for option 1 for now, for pip's purposes, until something more is needed.

[jaraco]

I can see that pip never used the _search_paths method.

 pip main $ git log -p | grep _search_paths
 pip main $

I'm removing the protection I added for it.