Engine

Skill igmarin/rails-agent-skills/skills/personas/engine

This is my personal configuration of skills as a Ruby on Rails Dev

Install

npx -y skills add igmarin/rails-agent-skills --skill engine

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

One thing to look at

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What its author says it does

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Complete Rails engine development loop with hard gates: scaffold engine structure with isolate_namespace and verify gemspec validation → set up dummy app and verify tests run with exit 0 → NEVER integrate engine into host app before engine tests pass standalone, namespace is isolated, migrations won't conflict, and dependencies are declared → code review and dependency auditing → release with SemVer, changelog, and upgrade notes; phases authoring→testing→implementation/review→documentation/release. Use when creating, extracting, or maintaining Rails engines. Trigger: create engine, extract engine, engine release, engine testing, mountable engine, gem extraction.

The file declares its own license as MIT. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

4.9 KB, as published. Nobody here has run it

Phase 1: Engine Authoring

skills/engines/create-engine (sub-skill — invoke separately) — Design and scaffold namespace isolation, directory structure, and gemspec configuration

Kickoff command:

rails plugin new my_engine --mountable --test-framework=rspec

Key files to verify after scaffolding:

lib/my_engine/engine.rb — must contain isolate_namespace MyEngine
lib/my_engine/version.rb
my_engine.gemspec — must pass gem specification validation
test/dummy/ — dummy app present

HARD GATE — Engine Structure Check:

grep -r 'module MyEngine' lib/my_engine/engine.rb
ruby -e "require 'rubygems'; spec = Gem::Specification.load('my_engine.gemspec'); puts spec.validate"
grep 'isolate_namespace\|engine.config.isolate_namespace' lib/my_engine/engine.rb

If structure check FAILS: Return to create-engine and fix.

Phase 2: Testing Setup

skills/engines/test-engine (sub-skill — invoke separately) — Set up dummy app, spec helpers, factory isolation, and test database
Write initial characterization tests:
- Test engine mounting
- Test generators if any
- Test core functionality

Run tests from engine root:

cd my_engine && bundle exec rspec

HARD GATE — Tests Run:

bundle exec rspec --format progress 2>&1 | tail -5

Must show no load errors and exit 0.

If load errors appear: Consult the test-engine sub-skill for ordered troubleshooting steps.

HARD GATE — Isolation Before Integration:

NEVER integrate engine into host app before:

Engine tests pass standalone
Namespace properly isolated
Migrations won't conflict
Dependencies clearly declared

Phase 3: Implementation & Review

Implement features using:
- tdd agent for complex features
- Individual skills for simple additions
skills/engines/review-engine (sub-skill — invoke separately)
skills/engines/upgrade-engine (sub-skill — invoke separately)

Check gem dependencies:

bundle exec rake dependencies
bundle exec bundler-audit check --update

Phase 4: Documentation & Release

skills/engines/document-engine (sub-skill — invoke separately) — Installation, configuration, usage examples, changelog
skills/engines/release-engine (sub-skill — invoke separately) — Version bump (SemVer), changelog, upgrade notes, git tag

Release commands:

gem build my_engine.gemspec
gem push my_engine-1.0.0.gem
git tag v1.0.0 && git push origin v1.0.0

Optional: 3. skills/engines/create-engine-installer — Idempotent rails g my_engine:install generator for host app configuration

Output: Published gem or releasable GitHub repository.

Quick Reference

New engine?        → create-engine → test-engine
Extract from app?  → extract-engine → create-engine
Release engine?    → review-engine → release-engine
Not sure?          → skill-router

Common Anti-Patterns

Anti-Pattern	Fix
Namespace leakage — `::MyEngine` instead of `MyEngine::`	Verify `isolate_namespace MyEngine` in `engine.rb`
Migration conflicts — Migrations outside engine dir or missing path config	Run engine migrations in isolation via dummy app
Missing gemspec dependencies — Runtime gems in Gemfile but not in `.gemspec`	Run `bundle exec rake dependencies` and `bundler-audit check` at Phase 3 end
Dummy app load errors — Missing `require` or incorrect `spec_helper`	Use test-engine sub-skill diagnostic steps