Exclude descendants of `#[doc(hidden)]` modules from auto-completions

[crlf0710]

#[doc(hidden)] items are usually internals APIs that is not intended for use. It would be nice if they can be excluded from auto-completion results for downstream crates.

For projects using stable rustc, it's also nice to exclude #[unstable] items too.

[lnicola]

We already exclude #[doc(hidden)] from completion outside of the current crate. Not sure about #[unstable], though.

[flodiebold]

Excluding unstable items is #3020.

[crlf0710]

@lnicola I've not sure whether i missed something, but this is what i got when i wrote a proc-macro today:

The proc_macro::bridge should definitely be excluded because bridge is #[doc(hidden)]

[kjeremy]

Can we give it a lower score instead of excluding it?

[lnicola]

I think we exclude hidden items, but not descendents of hidden modules.

[crlf0710]

Maybe it's worth add excluding descendents of hidden modules as an option, if not making it default behavior...

[lnicola]

No, it's a good idea, it was probably an oversight.

[jyn514]

FWIW I consider it a bug that doc(hidden) applies recursively, rustdoc should still show the items if they're re-exported to a module that's not hidden: rust-lang/rust#59368

But I agree they should be hidden if they're not reexported.

[flodiebold]

Yeah, I don't think "Excluding descendants of #[doc(hidden)]" is exactly what we want -- but rather "Exclude auto-imports that include #[doc(hidden)] modules in the path".