craft-guard-clauselisted

# Skill: Craft Guard Clause > "Handle the bad cases first. Let the happy path breathe." ## The Standard 1. **Guards at the top**: All precondition checks before any business logic. 2. **One check, one exit**: Each guard handles one condition, then returns or throws. 3. **Flat over nested**: Guards eliminate if/else trees. Main logic lives at outer scope. ## The Anti-Patterns | ❌ Don't | ✅ Do | Why | |-----------------------------|-------------------------------|-------------------------------| | Nested if/else trees | Guard clauses | Readability, maintainability | | Check then continue | Check then exit | Happy path stays clear | | 10+ guards in one method | Split the method | Too many guards = too much responsibility | | Silent return on failure | Return Result or throw | Caller needs to know | ## Real-World Examples See [examples.md](examples.md).