igmarin/rails-agent-skills

Curated library of 28 public AI agent skills for Ruby on Rails development. Organized by category: testing, code-quality, engines, infrastructure, api, and context. Covers code review, architecture, security, testing (RSpec), engines, Hotwire, and TDD automation. Shared Ruby skills (YARD docs, DDD, service objects) have moved to ruby-core-skills. Repository agents remain documented in GitHub but are intentionally excluded from the Tessl tile.

1.78x

Quality

95%

Does it follow best practices?

Impact

93%

1.78x

Average score across 28 eval scenarios

Securityby

Passed

No known issues

Create Engine — Examples

Name: igmarin/rails-agent-skills
Rating: 93.21 (1 reviews)
Author: igmarin

Extended examples and patterns for engine creation.

Example 1: Mountable Authentication Engine

Scenario: Build an engine that provides authentication (login/logout) to host apps.

Step 1: Scaffold

rails plugin new auth_engine --mountable --full

Step 2: Define Host App Contract

Aspect	Requirement
Host must provide	User model with `email` and `password_digest` attributes; mount route in host routes
Engine exposes	SessionsController, AuthenticationHelper, require_login before_action
Configuration	`user_class` (default: "User"), `session_key` (default: :user_id)

Step 3: Implementation Structure

# lib/auth_engine.rb
require "auth_engine/version"
require "auth_engine/configuration"
require "auth_engine/engine"

module AuthEngine
  class << self
    def configuration
      @configuration ||= Configuration.new
    end

    def configure
      yield(configuration)
    end
  end
end

# lib/auth_engine/configuration.rb
module AuthEngine
  class Configuration
    attr_accessor :user_class, :session_key

    def initialize
      @user_class = "User"
      @session_key = :user_id
    end
  end
end

# lib/auth_engine/engine.rb
module AuthEngine
  class Engine < ::Rails::Engine
    isolate_namespace AuthEngine

    initializer "auth_engine.controller_helpers" do
      ActiveSupport.on_load(:action_controller) do
        include AuthEngine::AuthenticationHelper
      end
    end
  end
end

Step 4: Controller Using Configurable User Class

# app/controllers/auth_engine/sessions_controller.rb
module AuthEngine
  class SessionsController < ApplicationController
    def create
      user = AuthEngine.configuration.user_class.constantize.find_by(email: params[:email])
      if user&.authenticate(params[:password])
        session[AuthEngine.configuration.session_key] = user.id
        redirect_to main_app.root_path
      else
        flash.now[:alert] = "Invalid credentials"
        render :new
      end
    end

    def destroy
      session.delete(AuthEngine.configuration.session_key)
      redirect_to main_app.root_path
    end
  end
end

Step 5: Dummy App Setup

# spec/dummy/config/routes.rb
Rails.application.routes.draw do
  mount AuthEngine::Engine => "/auth"
end

# spec/dummy/app/models/user.rb
class User < ApplicationRecord
  has_secure_password
end

Example 2: Non-Mountable Background Job Engine

Scenario: Engine that provides shared background job processing capabilities.

rails plugin new job_engine --full

Key difference: No routes, no isolate_namespace, but needs Rails initialization hooks.

# lib/job_engine/engine.rb
module JobEngine
  class Engine < ::Rails::Engine
    # No isolate_namespace - jobs live in host app namespace

    initializer "job_engine.configure_queue_adapter" do |app|
      app.config.active_job.queue_adapter = :solid_queue if defined?(SolidQueue)
    end
  end
end

Common Mistakes to Avoid

Mistake	Why It Fails	Correct Approach
`class User < ::User`	Hard-coded host dependency	`config.user_class = "User"` then constantize
Auto-running migrations in initializer	Database errors on boot	Use generators for migrations, never auto-apply
Polluting host app routes	Namespace collision	Use `isolate_namespace` for mountable engines
No dummy app	Can't test integration	Always create dummy app with `rails plugin new`
Config as hash	No validation, hard to document	Config class with explicit attributes

Testing Checklist

See TESTING.md for detailed testing patterns.

Quick verification:

# Inside engine directory
cd spec/dummy
bundle exec rails routes | grep engine_name  # Verify routes
bundle exec rspec spec/requests               # Integration tests
bundle exec rspec spec/lib/configuration_spec # Config tests
grep -r "::User\|::Account" ../lib          # No hard-coded constants

agents

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skills

api

context

infrastructure

testing

README.md

tile.json