I've not tested this but I'm not convinced it will actually work in all cases. Our reason for this is that thanks to package upgrades and removals we'll end up with eg wheel-0.47.0.dist-info/ existing in site-packages, but it will be completely empty.

This is discovered as a distribution, and because metadata() falls back to "parse an empty string" it still has valid metadata, it's just that the metadata is empty. I'm currently hacking a test into pypa/build to check that dist.metadata.name is actually set.

I take that back, latest importlib_metadata has different behaviour and correctly raises an exception.

I must admit I don't understand the reasoning behind returning invalid distributions at all: if some empty directories that look like a dist but have no content are found, why return them at all?

I agree that globally dropping invalid distributions is the cleaner end state if the project wants that behavior. I kept this PR narrower for two reasons:

1. Distribution.discover()/distributions() is the lower-level discovery surface, and changing it to filter path entries would be a broader API/behavior change than entry_points() duplicate resolution.
2. The concrete failure here is narrower: when two distributions normalize to the same name, an invalid/empty older dist-info can win the unique() selection and hide the later valid distribution that actually has the entry point. Preferring the valid candidate only inside that duplicate-name choice fixes that failure without changing what raw discovery returns.

So this patch is conservative rather than philosophical: it avoids letting an invalid duplicate shadow a valid package, but does not decide whether invalid dist-info directories should disappear from discovery everywhere. If you prefer the broader policy, I can rework it in that direction.