Improve interop with importlib.metadata: variation without importlib_metadata

[abravalheri]

This is basically the same as #195 but without using importlib_metadata.

Feel free to close if #195 is preferred.

This might be worthy considering:

In general, I find that the following works relatively fine:

• using importlib_metadata.DistributionFinder, MetadataPathFinder to implement find_distrubitions, but then using importlib.metadata high-level APIs

And the following does not work:

• using importlib.metadata.DistributionFinder, MetadataPathFinder to implement find_distrubitions, but then using importlib_metadata high-level APIs

i.e. while this approach decreases the "spooky action at distance" of a transitive dependency installing importlib_metadata, it may also be more error prone if some dependency is indeed using importlib_metadata.

[takluyver]

Thanks! Does this somehow avoid the exception you found in setuptools tests in this comment?

[abravalheri]

For setuptools, it should be fine abravalheri/setuptools#14 (tests should OK, docs failing but that is unrelated).

(I went ahead and already added fixed the importlib.metadata compatibility in setuptools: pypa/setuptools#4339)

[takluyver]

Aha, so this is functionally similar to the original version of #195 (before involving importlib_metadata), but setuptools has changed so that it works?

I prefer this approach. I'll give it a day or so in case anyone else wants to weigh in, but if not then I'd like to merge this and cut another release.

[abravalheri]

(before involving importlib_metadata), but setuptools has changed so that it works?

It is very nuanced 😅

The reason for introducing importlib_metadata was mainly motivated by #195 (comment).

Trying to import importlib_metadata alone does not fix setuptools (because of the vendoring drama).

If setuptools did not have to use vendoring, then yes using importlib_metadata would be enough and no change in setuptools would be necessary. That is related to the drawbacks and considerations discussed in #199 (comment).