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]

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