elixir-antipatterns

Elixir Anti-Patterns Skill

Community contribution for Gentleman-Skills: Core catalog of 8 critical anti-patterns for Elixir/Phoenix applications.

Structure

This skill uses a hybrid approach to balance LLM context limits with comprehensive documentation:

elixir-antipatterns/
├── SKILL.md          # Core 8 patterns (322 lines as of v1.0)
├── README.md         # This file
├── assets/         
│   ├── extended.md   # Complete 40+ patterns (706 lines)

SKILL.md (Core - LLM Loaded)

Optimized for code review and refactoring sessions

Contains the top 8 most critical anti-patterns:

1. Use raise for business errors
2. Return nil for errors
3. Business logic in LiveView
4. N+1 queries
5. = inside with for failable operations
6. Query without indexes
7. Tests without assertions
8. Long with chains (>4 steps)

Why separate files?

• SKILL.md fits within LLM context windows
• Aligns with Gentleman-Skills standard (150-388 line target)
• Includes ASCII diagram for Phoenix architecture visualization
• extended.md preserves all knowledge with advanced Ecto patterns

What This Skill Covers

• Error Handling: Tagged tuples vs exceptions vs nil
• Separation of Concerns: Phoenix contexts vs business logic in views
• Database Performance: N+1 queries, indexing, transactions
• Testing Best Practices: Independent tests, assertions, async execution

Why It's Valuable

• Comprehensive Elixir/Phoenix skill: Covers error handling, contexts, Ecto, testing
• Code review optimized: Trigger designed for PR reviews and refactoring
• Visual aids: ASCII diagrams for Phoenix Context Separation architecture
• Advanced techniques: extended.md documents 3 Ecto preload strategies

Usage with AI Assistants

The AI will automatically load SKILL.md when working with Elixir code. For deeper reference:

## Skills
When working with Elixir/Phoenix code, load the `elixir-antipatterns` skill.
For comprehensive patterns, reference `extended.md`.

Testing

Validated with:

• ✅ Cursor on Elixir/Phoenix projects
• ✅ Production applications (2+ years)
• ✅ Mix format + Credo compliance

Contributing

Created for Gentleman-Skills.

License

MIT License - Free to use and modify