`darwin-timeout` documentation review by Claude Code Opus 4.5 Review)

darwin-timeout-doc-review-by-claude.md

Documentation Review

Documentation Sources

1. README.md - User-facing documentation
2. Module docs - //! comments at module top
3. Function docs - /// comments on public items
4. Code comments - /* */ and // inline comments
5. SAFETY comments - Required for unsafe blocks

README.md Evaluation

Strengths

1. Clear purpose statement - "GNU timeout clone for macOS"
2. Installation instructions - Homebrew formula provided
3. Usage examples - Multiple practical examples
4. Feature comparison - vs GNU timeout
5. Technical details - Wall clock vs CPU time diagram
6. Exit code documentation - Matches GNU spec

Structure

# timeout - GNU timeout for macOS
├── Why this exists
├── Features
├── Installation
├── Usage
│   ├── Basic timeout
│   ├── Send different signal
│   ├── Escalate to SIGKILL
│   ├── Verbose mode
│   ├── JSON output
│   └── Environment variables
├── Exit Status
├── Options Reference
├── How It Works (diagram)
└── License

Quality Score: Excellent

User documentation is comprehensive and well-organized.

Module Documentation

Assessment by Module

Module	Has //!	Has /* */ header	Quality
lib.rs	No	No	Minimal
main.rs	No	Yes	Not in rustdoc
args.rs	No	No	None
duration.rs	No	Yes	Not in rustdoc
error.rs	No	Yes	Not in rustdoc
signal.rs	No	No	None
process.rs	No	Yes	Not in rustdoc
runner.rs	No	Yes	Not in rustdoc
wait.rs	No	Yes	Not in rustdoc
sync.rs	No	Yes	Not in rustdoc
allocator.rs	No	Yes	Not in rustdoc
io.rs	No	Yes	Not in rustdoc
panic.rs	No	Yes	Not in rustdoc

Key Issue: Most modules have informative /* ... */ block comments at the top, but these are not doc comments. They don't appear in cargo doc output.

Example (duration.rs)

Current (code comment - not in rustdoc):

/*
 * duration.rs
 *
 * Parse "30s", "100ms", "500us", "5m", "1.5h", "0.5d". No suffix means seconds.
 * Zero means run forever (useful for process group handling without timeout).
 *
 * Uses integer math internally (nanosecond precision) to avoid pulling in
 * the ~6KB f64::from_str machinery from libstd.
 */

Should be (doc comment - appears in rustdoc):

//! Parse duration strings like "30s", "100ms", "500us", "5m", "1.5h", "0.5d".
//!
//! No suffix means seconds. Zero means run forever (useful for process group
//! handling without timeout).
//!
//! Uses integer math internally (nanosecond precision) to avoid pulling in
//! the ~6KB `f64::from_str` machinery from libstd.

Note: This is a quick fix - the content already exists, it just needs to be converted from /* */ to //! format.

Function Documentation

Doc Comments vs Code Comments

Important Distinction:

• /// and //! are doc comments - generate rustdoc, visible in API docs
• // and /* */ are code comments - only visible in source code

The codebase often uses code comments where doc comments would be more appropriate:

// Current (code comment - not in rustdoc):
/* zero duration = no timeout, run forever */
#[must_use]
pub const fn is_no_timeout(duration: &Duration) -> bool

// Should be (doc comment - appears in rustdoc):
/// Returns `true` if the duration represents "no timeout" (run forever).
#[must_use]
pub const fn is_no_timeout(duration: &Duration) -> bool

Public API Documentation

Some public functions have proper doc comments. Example from duration.rs:

/// Parse "30", "30s", "100ms", "500us", "1.5m", "2h", "0.5d". No suffix = seconds.
///
/// # Examples
///
/// ```
/// use darwin_timeout::duration::parse_duration;
/// use std::time::Duration;
///
/// assert_eq!(parse_duration("30").unwrap(), Duration::from_secs(30));
/// assert_eq!(parse_duration("30s").unwrap(), Duration::from_secs(30));
/// assert_eq!(parse_duration("100ms").unwrap(), Duration::from_millis(100));
/// ```
pub fn parse_duration(input: &str) -> Result<Duration>

Missing Documentation

Clippy pedantic reports:

• Missing # Errors sections for fallible functions
• Missing # Panics sections (though nothing panics)
• Some doc items need backticks

Documentation Patterns

Good Pattern - Error Documentation:

/// # Errors
///
/// - `WaitForFileTimeout` if timeout expires before file appears
/// - `WaitForFileError` if stat() fails with an error other than ENOENT
pub fn wait_for_file(...) -> Result<()>

Good Pattern - Safety Invariants:

/// # Safety Invariants
///
/// The state machine guarantees safe access:
/// - `UNINIT`: value is None, safe to write (after winning CAS)
/// - `INITIALIZING`: one thread is writing, others must spin-wait
/// - `INITIALIZED`: value is Some, immutable, safe to read

Code Comments

Comment Style

The project uses both styles appropriately:

• /* ... */ for multi-line explanations
• // for single-line notes
• // SAFETY: for unsafe blocks (required by lint)

Comment Quality

Excellent - Explains Why:

/* zero duration = no timeout, run forever */
#[must_use]
pub const fn is_no_timeout(duration: &Duration) -> bool {
    duration.is_zero()
}

Excellent - Documents Constraint:

/* exit codes per GNU coreutils convention. don't change these. */
pub mod exit_codes {
    /// Command ran too long (timed out)
    pub const TIMEOUT: u8 = 124;

Excellent - Explains Design Decision:

/* stack buffer - no heap allocation */
let mut frac_buf = [b'0'; 9];

SAFETY Comments

Required by Lint

[lints.clippy]
undocumented_unsafe_blocks = "deny"

Examples

Good - Explains Preconditions:

// SAFETY: malloc is safe to call with any size. Returns aligned memory for
// alignments <= 16 bytes (guaranteed by macOS malloc). For larger alignments,
// posix_memalign is used which guarantees the requested alignment.
unsafe {
    if layout.align() > 16 { ... }
}

Good - Explains Invariants:

// SAFETY: We won the CAS race, transitioning UNINIT -> INITIALIZING.
// No other thread can be reading (state wasn't INITIALIZED) or
// writing (we hold the INITIALIZING lock). Safe to write.
unsafe {
    *self.value.get() = Some(value);
}

Good - References Memory Ordering:

// SAFETY: state is INITIALIZED with Acquire ordering, which synchronizes
// with the Release store in set/get_or_init. The value was written before
// that Release store, so we can safely read it.

Doctests

Count and Quality

/// # Examples
///
/// ```
/// use darwin_timeout::duration::parse_duration;
/// assert_eq!(parse_duration("30").unwrap(), Duration::from_secs(30));
/// ```

Doctests exist for key public functions and serve as:

1. Usage examples
2. Regression tests
3. Documentation validation

Recommendations

High Value

1. Add # Errors sections to fallible functions
2. Add backticks to inline code in docs

Medium Value

1. Add //! module docs to args.rs and signal.rs
2. Consider adding architecture overview diagram to README

Low Value

1. Add changelog (CHANGELOG.md)
2. Add contributing guide

Conclusion

Documentation Quality: Mixed

Aspect	Rating
README	Excellent
Module docs (//!)	Missing (content exists as /* */)
Function docs (///)	Sparse (content often exists as /* */ or //)
Code comments (//, /* */)	Excellent
SAFETY comments	Excellent
Doctests	Good (where present)

Key Issue: The codebase has excellent code comments explaining implementation details, but uses regular comments (/* */, //) instead of doc comments (//!, ///). The explanations exist in source but don't appear in cargo doc output.

Quick Fix: Convert existing comments to doc format:

• Module headers: /* ... */ → //! ...
• Function comments: /* ... */ or // → /// ...

The content is already written; it just needs the comment style changed.

The SAFETY comments are particularly thorough, which is critical for a project with significant unsafe code.