Rust Policy Enforcement

Enforces core Rust development policies for the aiassisted project. Use this skill to verify code compliance or guide implementation.

When to use this skill

Use this skill when:

• Writing new Rust code in this project
• Reviewing Rust code for policy compliance
• Checking if code meets project standards
• Fixing policy violations

Quick Reference

Policy	Requirement
Zero warnings	cargo check must produce 0 warnings
Static dispatch	Prefer generics over dyn traits
Minimal Arc	Use Arc only for actual concurrent sharing
Testing	Unit tests for all modules (positive + negative)
Integration tests	Workflow tests in tests/ directory

Policy Checklist

1. Zero Warning Policy

Verify no warnings:

cargo check 2>&1 | grep -c warning  # Must be 0

Common fixes:

• Unused variable → prefix with _ or remove
• Unused import → remove
• Dead code → remove or justify #[allow(dead_code)]

2. Static Dispatch

Check for dynamic dispatch patterns:

// ❌ Avoid
fn process(handler: &dyn Handler) { }
fn process(handler: Box<dyn Handler>) { }

// ✅ Prefer
fn process<H: Handler>(handler: &H) { }
fn process(handler: impl Handler) { }

Acceptable exceptions:

• Heterogeneous collections
• Plugin systems
• Breaking dependency cycles

3. Minimal Arc Usage

Review Arc usage - this CLI runs sequentially with no shared state:

// ❌ Avoid in this codebase
fn execute(fs: Arc<dyn FileSystem>) { }

// ✅ Prefer
fn execute<F: FileSystem>(fs: &F) { }

Arc is acceptable for:

• Actual multi-threaded sharing
• Async tasks across threads

4. Comprehensive Unit Tests

Every module must have:

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_function_success() { }  // Positive test

    #[test]
    fn test_function_error() { }    // Negative test

    #[test]
    fn test_function_edge_case() { } // Edge case
}

Required coverage:

• Success paths
• Error handling
• Edge cases (empty, large, Unicode)
• Boundary conditions

Mock dependencies with mockall:

use mockall::{mock, predicate::*};

mock! {
    pub FileSystem {}
    impl crate::core::infra::FileSystem for FileSystem {
        async fn read(&self, path: &Path) -> Result<String>;
    }
}

5. Integration Tests

Located in tests/ directory, use real implementations:

use wiremock::{Mock, MockServer, ResponseTemplate};

#[tokio::test]
async fn test_full_workflow() {
    let mock_server = MockServer::start().await;
    // Test with real HTTP client
}

Review Workflow

1. Check warnings:

   cargo check 2>&1 | grep warning
   

2. Search for dyn usage:

   grep -r "dyn " src/
   

3. Search for Arc usage:

   grep -r "Arc<" src/
   

4. Verify test coverage:

   cargo test
   

5. Check for missing tests: Look for modules without #[cfg(test)]

Detailed Reference

For comprehensive policy documentation, see rust-policy-guide.md.

Related Guidelines

• rust-dispatch-guide.md - Static vs dynamic dispatch
• rust-smart-pointers-guide.md - Box, Rc, Arc, RefCell usage
• rust-code-review-guide.md - Code review checklist