rails-instructions: Instructions file for GitHub Copilot

Rails 8 Core Principles Guide

Core Philosophy

• Follow Rails conventions religiously - they exist for good reasons
• Embrace the monolith - most applications don't need microservices
• Use Rails 8's built-in features before reaching for external gems
• Write code that's a joy to work with, not just functional
• Optimize for developer happiness and productivity

Rails 8 Stack Defaults

• Use SQLite for development and production by default
• Leverage Solid Queue for background job processing
• Implement Solid Cache for caching with database backend
• Use Solid Cable for WebSocket connections
• Embrace Propshaft for asset pipeline simplicity

Framework Principles

• Convention over configuration in all decisions
• Database-driven design with Active Record at the center
• RESTful resources and routes by default
• Server-side rendering with Hotwire enhancements
• Progressive enhancement over client-side complexity

Model Design Principles

• Keep models focused on data integrity and business rules
• Use Active Record validations extensively
• Implement scopes for common query patterns
• Add database indexes for foreign keys and frequently queried columns
• Use concerns for shared behavior across models

Model Best Practices

• Include schema annotations in all model files
• Order model contents consistently: constants, includes, associations, validations, callbacks, scopes, methods
• Keep callbacks minimal - consider service objects for complex logic
• Use dependent: options on associations to maintain referential integrity
• Implement proper counter caches for performance

Controller Principles

• Keep controllers thin and focused on HTTP concerns
• Use before_action filters for common setup and authorization
• Respond to multiple formats (HTML, Turbo Stream, JSON) appropriately
• Follow REST conventions for action names
• Handle errors gracefully with proper HTTP status codes

Controller Patterns

• Use strong parameters for all user input
• Prefer redirect_to with notice/alert over render after mutations
• Implement resourceful routes whenever possible
• Keep business logic out of controllers
• Use concerns for shared controller behavior