Implement RFC 3631: add rustdoc doc_cfg features

[GuillaumeGomez]

Implementation of rust-lang/rfcs#3631.

First commit comes from #138755.

What remains to be done:

• Handle doc(auto_cfg(show/hide)) "collisions"
• Add more tests

r? ghost

[petrochenkov]

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]

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]

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

Do you mean like in #138515? :)

[GuillaumeGomez]

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

[rust-log-analyzer]

The job mingw-check-tidy failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

info: removing rustup binaries
info: rustup is uninstalled
##[group]Image checksum input
mingw-check-tidy
# We use the ghcr base image because ghcr doesn't have a rate limit
# and the mingw-check-tidy job doesn't cache docker images in CI.
FROM ghcr.io/rust-lang/ubuntu:22.04

ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get install -y --no-install-recommends \
  g++ \
  make \
---

COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/

# NOTE: intentionally uses python2 for x.py so we can test it still works.
# validate-toolstate only runs in our CI, so it's ok for it to only support python3.
ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test \
           --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
#
# This file is autogenerated by pip-compile with Python 3.10
# by the following command:
#
#    pip-compile --allow-unsafe --generate-hashes reuse-requirements.in
---
#12 3.462 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#12 4.039 Collecting virtualenv
#12 4.080   Downloading virtualenv-20.29.3-py3-none-any.whl (4.3 MB)
#12 4.144      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 4.3/4.3 MB 69.7 MB/s eta 0:00:00
#12 4.201 Collecting platformdirs<5,>=3.9.1
#12 4.205   Downloading platformdirs-4.3.7-py3-none-any.whl (18 kB)
#12 4.244 Collecting filelock<4,>=3.12.2
#12 4.247   Downloading filelock-3.18.0-py3-none-any.whl (16 kB)
#12 4.266 Collecting distlib<1,>=0.3.7
#12 4.269   Downloading distlib-0.3.9-py2.py3-none-any.whl (468 kB)
#12 4.277      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 469.0/469.0 KB 94.1 MB/s eta 0:00:00
#12 4.359 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#12 4.544 Successfully installed distlib-0.3.9 filelock-3.18.0 platformdirs-4.3.7 virtualenv-20.29.3
#12 4.544 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#12 DONE 4.6s

#13 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#13 DONE 0.0s
---
DirectMap4k:      126912 kB
DirectMap2M:     9310208 kB
DirectMap1G:     9437184 kB
##[endgroup]
Executing TIDY_PRINT_DIFF=1 python2.7 ../x.py test            --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
+ TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.05s
##[endgroup]
WARN: currently no CI rustc builds have rustc debug assertions enabled. Please either set `rust.debug-assertions` to `false` if you want to use download CI rustc or set `rust.download-rustc` to `false`.
[TIMING] core::build_steps::tool::LibcxxVersionTool { target: x86_64-unknown-linux-gnu } -- 0.222
---
[TIMING] core::build_steps::tool::Tidy { compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu } -- 0.000
fmt check
fmt: checked 5927 files
tidy check
tidy error: /checkout/compiler/rustc_passes/messages.ftl: message `passes_doc_auto_cfg_wrong_literal` appears before `passes_doc_auto_cfg_expects_hide_or_show`, but is alphabetically later than it
run `./x.py test tidy --bless` to sort the file correctly
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_passes/messages.ftl:189: odd number of backticks
##[error]tidy error: /checkout/library/std/src/lib.rs:304: line not in alphabetical order
##[error]tidy error: /checkout/library/core/src/lib.rs:175: line not in alphabetical order
removing old virtual environment
tidy error: The Unstable Book has a 'language feature' section 'doc-cfg' which doesn't correspond to an unstable language feature
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (25.0.1)
linting python files
All checks passed!
checking python file formatting
26 files already formatted
checking C++ file formatting
some tidy checks failed
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:45
  local time: Tue Mar 25 11:25:34 UTC 2025
  network time: Tue, 25 Mar 2025 11:25:34 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[bors]

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