Rust Code Quality & Idioms

Enforces canonical Rust design: replacing .unwrap() with ? error propagation, defining custom error enums via thiserror, and avoiding unnecessary heap allocations and .clone().

1. Purpose

Refactor Rust code to prevent panics and improve performance.

2. When to Use

Use this skill when:

• Replacing unsafe .unwrap() or .expect() calls in library code with Result<T, E> and ?.
• Creating clean, typed error enums.
• Replacing heap allocations (String) with borrowed slices (&str) in read-only functions.

3. When Not to Use

• Do not use for testing; use rust-testing.

4. Required Inputs

• target_file: Path to the Rust source file.

5. Missing-Input Behavior

1. If target_file is missing: ask for target file.
2. Never leave bare .unwrap() in production library code.

6. Procedure

Follow these numbered actions:

1. Action 1: Audit for Panics
   • Search for .unwrap() and .expect().
2. Action 2: Convert to Result Propagation
   • Return Result<T, AppError> and propagate using ?.
3. Action 3: Audit Allocations
   • Change fn takes_string(s: String) to fn takes_string(s: &str).
4. Action 4: Verify Compiler & Tests
   • Run cargo check and cargo test.

7. Decision Rules

• Never use .unwrap() in production libraries; use ? or handle None.

8. Output Format

Emit the report using this template:

### Rust Code Quality Report: [File]

- **File Modified**: `[path]`
- **Patterns Applied**: [e.g. Error Propagation, Borrowed Slices]
- **Compile Status**: PASS
- **Test Status**: PASS

#### Improvements Made
- [Improvement 1]

9. Verification Checklist

• No bare .unwrap() calls in modified code.
• cargo test passes cleanly.
• No unnecessary .clone() calls.

10. Common Failures and Recovery

11. Stop or Escalation Conditions

Stop and ask the user when:

• Converting to Result requires modifying public library traits.

12. Examples

Example 1: Successful Execution

Input:

File: src/config.rs
Issue: let val = env::var("PORT").unwrap();

Output:

### Rust Code Quality Report: src/config.rs

- **File Modified**: `src/config.rs`
- **Patterns Applied**: Error Propagation with `?`
- **Compile Status**: PASS
- **Test Status**: PASS

#### Improvements Made
- Replaced `.unwrap()` with `env::var("PORT").map_err(ConfigError::from)?`.

Example 2: Ambiguous or Missing Input

Input:

Improve rust.

Output:

### Rust Code Quality Report: Halted - No File

- **Status**: Halted

Please specify the target Rust file to inspect.

Example 3: Expected Final Output

Output:

### Rust Code Quality Report: src/parser.rs

- **File Modified**: `src/parser.rs`
- **Patterns Applied**: Borrowed Slice Parameters
- **Compile Status**: PASS
- **Test Status**: PASS