Concerns

A concern is a module mixed into other classes. It should not know which classes use it.

component :model_concerns, in: "app/models/concerns/**/*.rb"
model_concerns.cannot_reference_includers

Rule id: concerns.independence

ArchSpec finds every class that includes, prepends, or extends a concern, then flags the concern for referencing that class by constant.

module Chargeable
  def charge
    Order.create!(...)  # Chargeable must not reference its includer Order
  end
end

class Order < ApplicationRecord
  include Chargeable
end

A concern that names its includer couples the two and defeats the point of extracting it. Passing behavior through the instance, such as self or a method the includer defines, does not trigger the rule.

The :rails_strict and :vanilla_rails architectures apply this to app/**/concerns/**/*.rb. Override the glob with concerns:, or pass concerns: false to skip it.