attac-t Skill: Craft Guard Clause
"Handle the bad cases first. Let the happy path breathe."
The Standard
- Guards at the top: All precondition checks before any business logic.
- One check, one exit: Each guard handles one condition, then returns or throws.
- 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.