# Case Study: Issue #28 — Quality Audit, Stable Rust Best Practices, and Documentation

## Issue Summary

**Issue:** [#28 — Double check we don't depend on any non stable features of rust and use all the latest best practices of rust in the code](https://github.com/linksplatform/mem-rs/issues/28)

**Scope:** Comprehensive quality audit covering stable Rust compliance, dependency freshness, documentation coverage, test organization, and automated doc generation.

## Requirements Analysis

### R1: No non-stable Rust features

**Status:** Satisfied (pre-existing, verified)

The codebase already migrated from nightly to stable Rust in PR #25. This audit verified:
- `rust-toolchain.toml` specifies `channel = "stable"`
- No `#![feature(...)]` attributes anywhere in the codebase
- All unstable standard library APIs replaced with stable alternatives via `allocator-api2`
- Stable alternatives for `MaybeUninit::slice_assume_init_mut`, `write_slice_cloned`, and `slice_ptr_get` implemented in `raw_mem::uninit`

### R2: Use latest Rust best practices

**Status:** Resolved

Changes made:
- **Edition 2024 upgrade**: Migrated from edition 2021 to 2024
  - All `unsafe fn` bodies now require explicit `unsafe {}` blocks (Rust 2024 requirement)
  - Applied via `cargo fix` + manual review
- **Clippy compliance**: Fixed all 8 clippy warnings:
  - `suspicious_open_options` — added explicit `.truncate(false)` to `File::options()`
  - `missing_safety_doc` — added `# Safety` sections to 5 unsafe functions/traits
  - `manual_is_multiple_of` — replaced manual modulo check with `.is_multiple_of()`
  - `io_other_error` — used `io::Error::other()` instead of `io::Error::new()`
- **rustfmt.toml** updated to stable-only options (removed nightly-only `version`, `imports_granularity`, `error_on_*`)

### R3: Latest dependency versions

**Status:** Resolved

| Dependency | Before | After | Notes |
|-----------|--------|-------|-------|
| allocator-api2 | 0.2 | 0.4 | Major version bump, API compatible |
| criterion | 0.5 | 0.8 | Major version bump for benchmarks |
| memmap2 | 0.9.9 | 0.9.10 | Patch update |
| tempfile | 3.x | 3.24 | Minor update |
| thiserror | 2.x | 2.0.17 | Patch update |
| tokio | 1.x | 1.49 | Minor update |

### R4: Documentation in sync with code

**Status:** Resolved

- Added crate-level documentation with examples, backend table, and feature flags
- Added doc comments to all public types, traits, methods, and modules
- Fixed 2 broken intra-doc links (`MaybeUninit::slice_assume_init_mut`, `mem::zeroed`)
- Fixed ErasedMem doc test (was using `&mut dyn ErasedMem` which doesn't implement `RawMem`)
- Enabled `#![warn(missing_docs)]` to catch future regressions
- Documentation builds with `RUSTDOCFLAGS="-D warnings"` (zero warnings)
- Updated README to reflect edition 2024, added missing API methods (`grow_within`, `grow_assumed`)

### R5: Tests not in src/ folder

**Status:** Resolved

Moved tests from source files to the `tests/` folder:
- `src/raw_place.rs` — removed `zst_build` test, added equivalent in `tests/coverage.rs`
- `src/async_mem.rs` — moved 8 async tests to `tests/async_mem.rs`

### R6: Increased test and doc coverage

**Status:** Resolved

- 10 new doc-tests across the crate (all pass)
- ZST edge case test added to coverage tests
- 8 async tests moved to proper location and verified
- Total: 88+ unit tests, 10 doc-tests, Miri compatibility tests, criterion benchmarks

### R7: Automated documentation generation (GitHub Pages)

**Status:** Implemented

Added `deploy-docs` job to `.github/workflows/release.yml` following the pattern from:
- [linksplatform/Numbers PR #143](https://github.com/linksplatform/Numbers/pull/143)
- [linksplatform/trees-rs PR #29](https://github.com/linksplatform/trees-rs/pull/29)

Configuration:
- Runs after successful auto-release or manual-release
- Uses `cargo doc --no-deps --all-features`
- Deploys via `peaceiris/actions-gh-pages@v4`
- Publishes to `rust/` subdirectory on gh-pages branch
- `keep_files: true` preserves existing content

### R8: Bug fix — Error::OverAlloc

**Status:** Resolved (discovered during audit)

`src/prealloc.rs` referenced `Error::OverAlloc` which doesn't exist in the `Error` enum (only `OverGrow` exists). Additionally, the `grow()` signature in `PreAlloc` didn't match the `RawMem` trait. Both were fixed.

## Existing Libraries Considered

| Library | Purpose | Decision |
|---------|---------|----------|
| [allocator-api2](https://crates.io/crates/allocator-api2) | Stable allocator API | Already used, upgraded to 0.4 |
| [memmap2](https://crates.io/crates/memmap2) | Memory mapping | Already used, latest compatible |
| [thiserror](https://crates.io/crates/thiserror) | Error derive macros | Already used, latest |
| [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages) | GitHub Pages deployment | Added for doc deployment |

## Solution Summary

This was a quality audit with 8 distinct requirements. All were addressed:

1. No unstable features (verified)
2. Edition 2024 + clippy compliance (8 warnings fixed)
3. All dependencies at latest versions (2 major bumps)
4. Full documentation coverage with working doc-tests
5. Tests properly organized in `tests/` folder
6. Test coverage increased with new edge cases
7. Automated doc generation via GitHub Pages
8. Bug fix for `Error::OverAlloc` in `prealloc.rs`
