Show feature labels in generated docs

[davidpdrsn]

Checklist

• I have read the Contributor Guide
• I have read and agree to the Code of Conduct
• I have added a description of my changes and why I'd like them included in the section below

Description of Changes

Adds #[cfg_attr(docsrs, doc(cfg(any(feature = "..."))))] to required features are highlighted in the standard rustdoc way.

Before:

After:

Related Issues

None.

[davidpdrsn]

To test this locally you have to generate the docs with RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --features tokio --open.

[emilk]

Whoa, didn't know about this. Very nice!

[repi]

Thought this wasn't needed anymore, that docs.rs had implemented support for the ordinary cfg? or maybe that is still support in progress, no sure.

[davidpdrsn]

Thought this wasn't needed anymore, that docs.rs had implemented support for the ordinary cfg? or maybe that is still support in progress, no sure.

I don't know exactly what the state of things is but the labels aren't showing currently.

[emilk]

I tried this with cargo doc --open --no-deps --features tokio but don't see the new docs:

[repi]

maybe it is only with nightly rustdoc? believe docs.rs does run nightly

[emilk]

To test this locally you have to generate the docs with RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --features tokio --open.

Maybe I should have read that 🤦