False positive with ReversibleMigrationMethodDefinition with inline ActiveRecord model

[javierjulio]

If creating or updating data as part of a migration (e.g. creating a few records for a lookup table), it's considered good practice to inline the model definition to not break the migration if future changes are made, such as removing or renaming the model.

Expected behavior

To not trigger any warning when defining a local ActiveRecord model when needing to create or update data as part of the migration.

Actual behavior

With this example migration:

class CreateNotificationTypes < ActiveRecord::Migration[6.1]
  class NotificationType < ApplicationRecord
  end

  def change
    # ...
  end
end

The Rails/ReversibleMigrationMethodDefinition rule triggered a warning:

C: Rails/ReversibleMigrationMethodDefinition: Migrations must contain either a change method, or both an up and a down method.
  class NotificationType < ApplicationRecord ...
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Steps to reproduce the problem

• Edit any migration file and paste the example from the "Actual behavior" section
• Run bundle exec rubocop --only Rails/ReversibleMigrationMethodDefinition
• The warning should be reported on the line defining the inline ActiveRecord model

RuboCop version

> bundle exec rubocop -V
1.26.0 (using Parser 3.1.1.0, rubocop-ast 1.16.0, running on ruby 2.7.5 x86_64-darwin20)
  - rubocop-rails 2.14.2