new-mailer

What This Does

Generates an ActionMailer for sending transactional emails, including:

• Mailer class with email methods
• Email views (HTML and text)
• Mailer preview for development testing
• I18n translation files
• RSpec spec with email content tests

Usage

/new-mailer User                       # Creates UserMailer
/new-mailer Order                      # Creates OrderMailer
/new-mailer Admin::Report              # Creates Admin::ReportMailer

How It Works

1. Read reference patterns. Load mailer patterns from:

   • skills/new-mailer/references/mailer-examples.md
   • patterns/backend-patterns.md
   • styles/backend-ruby.md

2. Determine mailer name and actions. Parse the argument and infer:

   • Mailer class name (e.g., UserMailer)
   • Common email actions based on context (welcome, notification, etc.)
   • File paths for all generated files

3. Generate the mailer file. Create the mailer with:

   • frozen_string_literal: true
   • ApplicationMailer inheritance
   • Email methods with @user and other instance variables
   • Proper subject with I18n
   • mail call with to: and subject:

4. Generate email views. Create both HTML and text templates:

   • app/views/<mailer>/<action>.html.erb
   • app/views/<mailer>/<action>.text.erb

5. Generate mailer preview. Create preview class:

   • test/mailers/previews/<mailer>_preview.rb or
   • spec/mailers/previews/<mailer>_preview.rb

6. Generate I18n translations. Add to locale files:

   • config/locales/mailers.en.yml

7. Generate spec file. Create the spec with:

   • Delivery tests
   • Content tests for subject, body, recipients
   • Attachment tests if applicable

8. Run quality checks.

   bundle exec rubocop -A app/mailers/<path>.rb spec/mailers/<path>_spec.rb
   bundle exec rspec spec/mailers/<path>_spec.rb
   

9. Report results. Show generated files and preview URL.

Generated Files

app/mailers/<mailer_name>.rb
app/views/<mailer_name>/welcome.html.erb
app/views/<mailer_name>/welcome.text.erb
spec/mailers/<mailer_name>_spec.rb
spec/mailers/previews/<mailer_name>_preview.rb
config/locales/mailers.en.yml (appended)

Example Output

For /new-mailer User:

Mailer: app/mailers/user_mailer.rb

# frozen_string_literal: true

# Sends transactional emails to users.
#
# @example Send welcome email
#   UserMailer.welcome(@user).deliver_later
#
class UserMailer < ApplicationMailer
  # Sends a welcome email to a newly registered user.
  #
  # @param user [User] the user to welcome
  # @return [Mail::Message] the email message
  def welcome(user)
    @user = user
    @login_url = new_session_url

    mail(
      to: @user.email,
      subject: t('.subject', name: @user.name)
    )
  end

  # Sends a password reset email.
  #
  # @param user [User] the user requesting reset
  # @return [Mail::Message] the email message
  def password_reset(user)
    @user = user
    @reset_url = edit_password_reset_url(@user.password_reset_token)

    mail(
      to: @user.email,
      subject: t('.subject')
    )
  end
end

View: app/views/user_mailer/welcome.html.erb

Preview: spec/mailers/previews/user_mailer_preview.rb

# frozen_string_literal: true

# Preview user emails at http://localhost:3000/rails/mailers/user_mailer
class UserMailerPreview < ActionMailer::Preview
  def welcome
    UserMailer.welcome(User.first || FactoryBot.build(:user))
  end

  def password_reset
    UserMailer.password_reset(User.first || FactoryBot.build(:user))
  end
end

Rules

• Inherit from ApplicationMailer
• Use I18n for all subject lines and email copy
• Always provide both HTML and text versions
• Use deliver_later (not deliver_now) in application code
• Create previews for visual testing in development
• Test email content, not just delivery
• Use layouts for consistent email styling