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codex/tools/argument-comment-lint/README.md
2026-03-14 08:18:04 -07:00

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# argument-comment-lint
Isolated [Dylint](https://github.com/trailofbits/dylint) library for enforcing
Rust argument comments in the exact `/*param*/` shape.
Prefer self-documenting APIs over comment-heavy call sites when possible. If a
call site would otherwise read like `foo(false)` or `bar(None)`, consider an
enum, named helper, newtype, or another idiomatic Rust API shape first, and
use an argument comment only when a smaller compatibility-preserving change is
more appropriate.
It provides two lints:
- `argument_comment_mismatch` (`warn` by default): validates that a present
`/*param*/` comment matches the resolved callee parameter name.
- `uncommented_anonymous_literal_argument` (`allow` by default): flags
anonymous literal-like arguments such as `None`, `true`, `false`, and numeric
literals when they do not have a preceding `/*param*/` comment.
String and char literals are exempt because they are often already
self-descriptive at the callsite.
## Behavior
Given:
```rust
fn create_openai_url(base_url: Option<String>, retry_count: usize) -> String {
let _ = (base_url, retry_count);
String::new()
}
```
This is accepted:
```rust
create_openai_url(/*base_url*/ None, /*retry_count*/ 3);
```
This is warned on by `argument_comment_mismatch`:
```rust
create_openai_url(/*api_base*/ None, 3);
```
This is only warned on when `uncommented_anonymous_literal_argument` is enabled:
```rust
create_openai_url(None, 3);
```
## Development
Install the required tooling once:
```bash
cargo install cargo-dylint dylint-link
rustup toolchain install nightly-2025-09-18 \
--component llvm-tools-preview \
--component rustc-dev \
--component rust-src
```
Run the lint crate tests:
```bash
cd tools/argument-comment-lint
cargo test
```
Run the lint against `codex-rs` from the repo root:
```bash
./tools/argument-comment-lint/run.sh -p codex-core
just argument-comment-lint -p codex-core
```
If no package selection is provided, `run.sh` defaults to checking the
`codex-rs` workspace with `--workspace --no-deps`.
Repo runs also promote `uncommented_anonymous_literal_argument` to an error by
default:
```bash
./tools/argument-comment-lint/run.sh -p codex-core
```
The wrapper does that by setting `DYLINT_RUSTFLAGS`, and it leaves an explicit
existing setting alone. It also defaults `CARGO_INCREMENTAL=0` unless you have
already set it, because the current nightly Dylint flow can otherwise hit a
rustc incremental compilation ICE locally. To override that behavior for an ad
hoc run:
```bash
DYLINT_RUSTFLAGS="-A uncommented_anonymous_literal_argument" \
CARGO_INCREMENTAL=1 \
./tools/argument-comment-lint/run.sh -p codex-core
```
To expand target coverage for an ad hoc run:
```bash
./tools/argument-comment-lint/run.sh -p codex-core -- --all-targets
```