/dhh-rails-style

name: dhh-rails-style
description: This skill should be used when writing Ruby and Rails code in DHH's distinctive 37signals style. It applies when writing Ruby code, Rails applications, creating models, controllers, or any Ruby file. Triggers on Ruby/Rails code generation, refactoring requests, code review, or when the user mentions DHH, 37signals, Basecamp, HEY, or Campfire style. Embodies REST purity, fat models, thin controllers, Current attributes, Hotwire patterns, and the "clarity over cleverness" philosophy.

<objective> Apply 37signals/DHH Rails conventions to Ruby and Rails code. This skill provides comprehensive domain expertise extracted from analyzing production 37signals codebases (Fizzy/Campfire) and DHH's code review patterns. </objective>

<essential_principles>

Core Philosophy

"The best code is the code you don't write. The second best is the code that's obviously correct."

**Vanilla Rails is plenty:**

• Rich domain models over service objects
• CRUD controllers over custom actions
• Concerns for horizontal code sharing
• Records as state instead of boolean columns
• Database-backed everything (no Redis)
• Build solutions before reaching for gems

**What they deliberately avoid:**

• devise (custom ~150-line auth instead)
• pundit/cancancan (simple role checks in models)
• sidekiq (Solid Queue uses database)
• redis (database for everything)
• view_component (partials work fine)
• GraphQL (REST with Turbo sufficient)
• factory_bot (fixtures are simpler)
• rspec (Minitest ships with Rails)
• Tailwind (native CSS with layers)

**Development Philosophy:**

• Ship, Validate, Refine - prototype-quality code to production to learn
• Fix root causes, not symptoms
• Write-time operations over read-time computations
• Database constraints over ActiveRecord validations

</essential_principles>

<intake> What are you working on?

1. **Controllers** - REST mapping, concerns, Turbo responses, API patterns 2. **Models** - Concerns, state records, callbacks, scopes, POROs 3. **Views & Frontend** - Turbo, Stimulus, CSS, partials 4. **Architecture** - Routing, multi-tenancy, authentication, jobs, caching 5. **Testing** - Minitest, fixtures, integration tests 6. **Gems & Dependencies** - What to use vs avoid 7. **Code Review** - Review code against DHH style 8. **General Guidance** - Philosophy and conventions

**Specify a number or describe your task.** </intake>

<routing>

| Response | Reference to Read | |----------|-------------------| | 1, controller | [controllers.md](./references/controllers.md) | | 2, model | [models.md](./references/models.md) | | 3, view, frontend, turbo, stimulus, css | [frontend.md](./references/frontend.md) | | 4, architecture, routing, auth, job, cache | [architecture.md](./references/architecture.md) | | 5, test, testing, minitest, fixture | [testing.md](./references/testing.md) | | 6, gem, dependency, library | [gems.md](./references/gems.md) | | 7, review | Read all references, then review code | | 8, general task | Read relevant references based on context |

**After reading relevant references, apply patterns to the user's code.** </routing>

<quick_reference>

Naming Conventions

**Verbs:** `card.close`, `card.gild`, `board.publish` (not `set_style` methods)

**Predicates:** `card.closed?`, `card.golden?` (derived from presence of related record)

**Concerns:** Adjectives describing capability (`Closeable`, `Publishable`, `Watchable`)

**Controllers:** Nouns matching resources (`Cards::ClosuresController`)

**Scopes:**

• `chronologically`, `reverse_chronologically`, `alphabetically`, `latest`
• `preloaded` (standard eager loading name)
• `indexed_by`, `sorted_by` (parameterized)
• `active`, `unassigned` (business terms, not SQL-ish)

REST Mapping

Instead of custom actions, create new resources:

POST /cards/:id/close    → POST /cards/:id/closure
DELETE /cards/:id/close  → DELETE /cards/:id/closure
POST /cards/:id/archive  → POST /cards/:id/archival

Ruby Syntax Preferences

# Symbol arrays with spaces inside brackets
before_action :set_message, only: %i[ show edit update destroy ]

# Private method indentation
  private
    def set_message
      @message = Message.find(params[:id])
    end

# Expression-less case for conditionals
case
when params[:before].present?
  messages.page_before(params[:before])
else
  messages.last_page
end

# Bang methods for fail-fast
@message = Message.create!(params)

# Ternaries for simple conditionals
@room.direct? ? @room.users : @message.mentionees

Key Patterns

**State as Records:**

Card.joins(:closure)         # closed cards
Card.where.missing(:closure) # open cards

**Current Attributes:**

belongs_to :creator, default: -> { Current.user }

**Authorization on Models:**

class User < ApplicationRecord
  def can_administer?(message)
    message.creator == self || admin?
  end
end

</quick_reference>

<reference_index>

Domain Knowledge

All detailed patterns in `references/`:

| File | Topics | |------|--------| | [controllers.md](./references/controllers.md) | REST mapping, concerns, Turbo responses, API patterns, HTTP caching | | [models.md](./references/models.md) | Concerns, state records, callbacks, scopes, POROs, authorization, broadcasting | | [frontend.md](./references/frontend.md) | Turbo Streams, Stimulus controllers, CSS layers, OKLCH colors, partials | | [architecture.md](./references/architecture.md) | Routing, authentication, jobs, Current attributes, caching, database patterns | | [testing.md](./references/testing.md) | Minitest, fixtures, unit/integration/system tests, testing patterns | | [gems.md](./references/gems.md) | What they use vs avoid, decision framework, Gemfile examples | </reference_index>

<success_criteria> Code follows DHH style when:

• Controllers map to CRUD verbs on resources
• Models use concerns for horizontal behavior
• State is tracked via records, not booleans
• No unnecessary service objects or abs