Implement RFC 3631: add rustdoc doc_cfg features #138907

GuillaumeGomez · 2025-03-24T22:50:33Z

This implementation actually resulted in a lot of simplifications:

All cfg computation is now done in one place: propagate_doc_cfg.rs. Because (trait) impls are not retrieved at the same time as the other items, we cannot perform this computation in the clean process, it needs to be after.
Because there is cfg inheritance, we can keep track of them in one place (in propagate_doc_cfg.rs), meaning we don't need to copy an item's attributes to its children anymore. Only exception: impl items. For them we clone only cfg attributes.
propagate_doc_cfg.rs is also now much simpler, much less need to keep track of parents, since everything we need is handled by the new CfgInfo type.
I also suspect that Cfg::simplify_with could either be removed or at least used directly into propagate_doc_cfg.rs when we compute cfgs. Considering how big the PR already is, I'll do it in a follow-up.

I didn't remove the doc_cfg* features in this PR because some dependencies used in rustc (like stdarch) are using it, so we need to have a nightly released with this PR before I can switch to the new feature.

r? ghost

petrochenkov · 2025-03-25T09:48:06Z

What remains to be done:

I'd also want to block the stabilization on landing #138844 to avoid a stable rustdoc feature relying on externally observable hacks in rustc.
The crater run in #138844 returned mostly clean, so I expect it to land soon.

GuillaumeGomez · 2025-03-25T10:36:45Z

Noted! And that will be a nice improvement, thanks!

Just one thing left for the cfg expansion missing: #[cfg_attr(blabla, derive(Debug))]. In this case, the cfg is not kept in the generated derive items. It's been in my TODO list for a long time now. ^^'

petrochenkov · 2025-03-25T10:49:31Z

Just one thing left for the cfg expansion missing: #[cfg_attr(blabla, derive(Debug))]

Do you mean like in #138515? :)

GuillaumeGomez · 2025-03-25T10:52:03Z

You're my hero! Gonna need to handle this new attribute then. :)

bors · 2025-03-25T17:53:10Z

☔ The latest upstream changes (presumably #138923) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2025-03-27T19:41:02Z

☔ The latest upstream changes (presumably #138927) made this pull request unmergeable. Please resolve the merge conflicts.

Nightly feature `doc_auto_cfg` is merged into `doc_cfg` rust-lang/rust#138907

In rust-lang/rust#138907, the `doc_auto_cfg` feature was subsumed by `doc_cfg`. This does overall look like we're on a path toward stabilization, which is great. One problem here though is that a bunch of crates use the `cfg` `docsrs` to enable `doc_auto_cfg`. So if we enable it, then it causes those crates to stop compiling. This is overall very annoying, and I don't know how to unfuck things. So I changed the `cfg` knob to `docsrs_regex` which, doesn't quite provide a guarantee, but gets us closer to being masters of our own destiny.

In rust-lang/rust#138907, the `doc_auto_cfg` feature was subsumed by `doc_cfg`. This does overall looks like we're on a path toward stabilization, which is great. One problem here though is that a bunch of crates use the `cfg` `docsrs` to enable `doc_auto_cfg`. So if we enable it, then it causes those crates to emit hard errors. This is overall very annoying, and I don't know how to unfuck things. So I changed the `cfg` knob to `docsrs_jiff` which, doesn't quite provide a guarantee, but gets us closer to being masters of our own destiny. See also a similar change made to `regex`: rust-lang/regex#1305

See rust-lang/rust#138907

rust-lang/rust#138907

the feature gate name changed See rust-lang/rust#138907

The feature gate name changed See rust-lang/rust#138907

the feature gate name changed See rust-lang/rust#138907

the feature gate name changed See rust-lang/rust#138907 📬 *Issue #, if available:* ✍️ *Description of changes:* 🔏 *By submitting this pull request* - [x] I confirm that I've made a best effort attempt to update all relevant documentation. - [x] I confirm that my contribution is made under the terms of the Apache 2.0 license. --------- Co-authored-by: Ariel Ben-Yehuda <[email protected]>

rust-lang/rust#138907

- replace `doc_auto_cfg` with `doc_cfg` (#507, rust-lang/rust#138907) - update `as_ref`, `as_mut` compile error message

Our latest release failed to build on docs.rs [1] because the `doc_auto_cfg` feature has been subsumed by `doc_cfg`: rust-lang/rust#138907 [1]: https://docs.rs/crate/uefi/0.36.0/builds/2603179