language-optimization

name	language-optimization
description	Optimize code for readability, performance, maintainability, and security across Bash, Python, and Rust. Use when asked to improve code quality, optimize performance, add type safety, or refactor for idioms.
allowed-tools	Bash(cargo *), Bash(git *), Bash(mypy *), Bash(pytest *), Bash(ruff *), Bash(shellcheck *), Bash(shellharden *), Bash(shfmt *), Bash(uv *), Read, Write, Edit, Glob, Grep

Language Optimization

Optimize code across languages following universal principles and language-specific idioms.

Workflow

Think through optimization systematically:

1. Analyze: Identify issues - lint errors, type errors, performance bottlenecks, security gaps
2. Profile first: Measure before optimizing performance (never optimize without data)
3. Apply fixes: Follow language-specific standards from instructions/
4. Verify: All tests pass, metrics improved, no regressions

Universal Principles

Principle	Rule
KISS	Simple over clever; readability first
YAGNI	Don't build before needed; no premature optimization
DRY	Extract repeated logic; single source of truth
Fail Fast	Validate early; specific error messages
Security	No secrets in code; validate at boundaries

Optimization Targets (Priority Order)

1. Correctness: Fix bugs, handle edge cases
2. Type safety: Add/improve type annotations
3. Readability: Clear names, reduce nesting, simplify logic
4. Performance: Only after profiling identifies bottlenecks
5. Security: Input validation, secret management, dependency audit

<language_specific>

Bash/Shell

• Standards: instructions/bash.instructions.md
• Always: set -euo pipefail, quote variables, use [[ ]] not [ ]
• Tools: shellcheck, shellharden
• Prefer: fd over find, rg over grep, sd over sed

Python

• Standards: instructions/python.instructions.md
• Always: type hints on public functions, T | None not Optional[T]
• Tools: ruff (lint+format), mypy (types), pytest (tests)
• Prefer: generators over lists, pathlib over os.path, f-strings over .format()

Rust

• Standards: instructions/rust.instructions.md
• Always: handle all Result/Option, use clippy lints
• Tools: clippy (lints), rustfmt (format), cargo test
• Prefer: iterators over loops, &str over String in params, thiserror for errors

</language_specific>

<performance_patterns>

Common Optimizations

Pattern	Before	After
Algorithm	O(n^2) nested loops	O(n) hash map lookup
Caching	Recompute every call	Memoize/cache result
Lazy eval	Build full list	Generator/iterator
Batching	N individual calls	Single batch operation
Built-ins	Custom implementation	Standard library function

Performance Workflow

1. Set baseline benchmark
2. Profile to find bottleneck (not guess)
3. Apply targeted optimization
4. Measure improvement against baseline
5. Document trade-off if complexity increased

</performance_patterns>

Python: Add type safety

# Before
def get_user(id, include_posts=False):
    user = db.find(id)
    if include_posts:
        user['posts'] = db.posts(id)
    return user

# After
def get_user(user_id: int, *, include_posts: bool = False) -> User | None:
    user = db.find(user_id)
    if user is None:
        return None
    if include_posts:
        user.posts = db.posts(user_id)
    return user

Bash: Modern idioms

# Before
files=$(find . -name "*.py")
for f in $files; do
    if [ -f "$f" ]; then
        grep -l "TODO" "$f"
    fi
done

# After
fd -e py --type f -x rg -l "TODO" {}

Rust: Idiomatic error handling

// Before
fn read_config(path: &str) -> String {
    let contents = std::fs::read_to_string(path).unwrap();
    contents
}

// After
fn read_config(path: &Path) -> Result<Config, ConfigError> {
    let contents = std::fs::read_to_string(path)
        .map_err(|e| ConfigError::ReadFailed { path: path.into(), source: e })?;
    toml::from_str(&contents)
        .map_err(|e| ConfigError::ParseFailed { source: e })
}

Success Criteria

Optimization is complete when:

• All linter/type checks pass with zero warnings
• Test suite passes with no regressions
• Performance improved (if that was the goal, with measurements)
• Code follows language-specific idioms from instructions/

References

• Language standards: instructions/bash.instructions.md, instructions/python.instructions.md, instructions/rust.instructions.md
• Refactoring patterns: skills/code-maintenance/