gh-127036: Update importlib.util._LazyModule.__getattribute__ to special-case requests for __spec__

[Sachaa-Thanasius]

Allow importlib.util._LazyModule to special-case its __spec__ attribute so that when the regular import machinery requests that attribute, it doesn't trigger the full module load. This will make it easier to use importlib.util.LazyLoader.

• Issue: Allow lazily loaded modules to be imported multiple times without forced resolution #127036

[Sachaa-Thanasius]

A few things I'm unsure of:

• Is this worthy of a news fragment?
• What kind of tests would suffice? I can imagine adding two along the lines of test_spec_passthrough_without_load and test_e2e_same_module in Lib/test/test_importlib/test_lazy.py, but I'm not confident in that, so I'd appreciate any guidance.

[brettcannon]

• Is this worthy of a news fragment?

I think so since it changes the semantics and someone may have been relying on it.

• What kind of tests would suffice?

I think what you already have in the PR suffices as it verifies things are working.

[brettcannon]

And apologies for taking so long to get to this PR!

[brettcannon]

FYI my approval is still gated on a news entry thanks to CI checking for it.

[Sachaa-Thanasius]

Cheers! Looking at this with fresh eyes, the semantic change definitely warrants more than just a code change.

In addition to the news entry, I'll attempt to tweak the LazyLoader docs and LazyLoader.exec_module comment to mention the __spec__ special case, since both currently specify that any attribute access triggers the load. Hope that's fine.

[brettcannon]

Hope that's fine.

Sounds great!

[brettcannon]

This needs at least a news entry and doc changes.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[brettcannon]

@Sachaa-Thanasius do you think you want to continue to work on this and address the review comments?

[brettcannon]

@Sachaa-Thanasius if you end up wanting to pick up this PR later just let me know, but otherwise I'm closing this PR due to lack of activity.

[Sachaa-Thanasius]

Apologies, life was distracting. Still is. Also, I had second thoughts on the scope of this (e.g. maybe we actually want to return a copy of the spec, since it's mutable; maybe there are other import-related attributes we want to exclude like __path__; and so on).

I'll come back to this when I'm in a better headspace (or maybe someone will beat me to it :D).