## Why
`argument-comment-lint` had become a PR bottleneck because the repo-wide
lane was still effectively running a `cargo dylint`-style flow across
the workspace instead of reusing Bazel's Rust dependency graph. That
kept the lint enforced, but it threw away the main benefit of moving
this job under Bazel in the first place: metadata reuse and cacheable
per-target analysis in the same shape as Clippy.
This change moves the repo-wide lint onto a native Bazel Rust aspect so
Linux and macOS can lint `codex-rs` without rebuilding the world
crate-by-crate through the wrapper path.
## What Changed
- add a nightly Rust toolchain with `rustc-dev` for Bazel and a
dedicated crate-universe repo for `tools/argument-comment-lint`
- add `tools/argument-comment-lint/driver.rs` and
`tools/argument-comment-lint/lint_aspect.bzl` so Bazel can run the lint
as a custom `rustc_driver`
- switch repo-wide `just argument-comment-lint` and the Linux/macOS
`rust-ci` lanes to `bazel build --config=argument-comment-lint
//codex-rs/...`
- keep the Python/DotSlash wrappers as the package-scoped fallback path
and as the current Windows CI path
- gate the Dylint entrypoint behind a `bazel_native` feature so the
Bazel-native library avoids the `dylint_*` packaging stack
- update the aspect runtime environment so the driver can locate
`rustc_driver` correctly under remote execution
- keep the dedicated `tools/argument-comment-lint` package tests and
wrapper unit tests in CI so the source and packaged entrypoints remain
covered
## Verification
- `python3 -m unittest discover -s tools/argument-comment-lint -p
'test_*.py'`
- `cargo test` in `tools/argument-comment-lint`
- `bazel build
//tools/argument-comment-lint:argument-comment-lint-driver
--@rules_rust//rust/toolchain/channel=nightly`
- `bazel build --config=argument-comment-lint
//codex-rs/utils/path-utils:all`
- `bazel build --config=argument-comment-lint
//codex-rs/rollout:rollout`
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/16106).
* #16120
* __->__ #16106
## Summary
Split the old all-in-one `rust-ci.yml` into:
- a PR-time Cargo workflow in `rust-ci.yml`
- a full post-merge Cargo workflow in `rust-ci-full.yml`
This keeps the PR path focused on fast Cargo-native hygiene plus the
Bazel `build` / `test` / `clippy` coverage in `bazel.yml`, while moving
the heavyweight Cargo-native matrix to `main`.
## Why
`bazel.yml` is now the main Rust verification workflow for pull
requests. It already covers the Bazel build, test, and clippy signal we
care about pre-merge, and it also runs on pushes to `main` to re-verify
the merged tree and help keep the BuildBuddy caches warm.
What was still missing was a clean split for the Cargo-native checks
that Bazel does not replace yet. The old `rust-ci.yml` mixed together:
- fast hygiene checks such as `cargo fmt --check` and `cargo shear`
- `argument-comment-lint`
- the full Cargo clippy / nextest / release-build matrix
That made every PR pay for the full Cargo matrix even though most of
that coverage is better treated as post-merge verification. The goal of
this change is to leave PRs with the checks we still want before merge,
while moving the heavier Cargo-native matrix off the review path.
## What Changed
- Renamed the old heavyweight workflow to `rust-ci-full.yml` and limited
it to `push` on `main` plus `workflow_dispatch`.
- Added a new PR-only `rust-ci.yml` that runs:
- changed-path detection
- `cargo fmt --check`
- `cargo shear`
- `argument-comment-lint` on Linux, macOS, and Windows
- `tools/argument-comment-lint` package tests when the lint itself or
its workflow wiring changes
- Kept the PR workflow's gatherer as the single required Cargo-native
status so branch protection can stay simple.
- Added `.github/workflows/README.md` to document the intended split
between `bazel.yml`, `rust-ci.yml`, and `rust-ci-full.yml`.
- Preserved the recent Windows `argument-comment-lint` behavior from
`e02fd6e1d3` in `rust-ci-full.yml`, and mirrored cross-platform lint
coverage into the PR workflow.
A few details are deliberate:
- The PR workflow still keeps the Linux lint lane on the
default-targets-only invocation for now, while macOS and Windows use the
broader released-linter path.
- This PR does not change `bazel.yml`; it changes the Cargo-native
workflow around the existing Bazel PR path.
## Testing
- Rebasing this change onto `main` after `e02fd6e1d3`
- `ruby -e 'require "yaml"; %w[.github/workflows/rust-ci.yml
.github/workflows/rust-ci-full.yml .github/workflows/bazel.yml].each {
|f| YAML.load_file(f) }'`
