[Rails 5] Overriding `db:schema:load` rake in order to load legacy schema before running the default `db:schema:load` task

1_remove_task.rake

#lib/tasks/remove_task.rake

Rake::TaskManager.class_eval do
  def remove_task(task_name)
    @tasks.delete(task_name.to_s)
  end
end

def remove_task(name)
  Rake.application.remove_task(name)
end

2_db_schema_load.rake

#lib/tasks/db_schema_load.rake

require 'active_record'
load File.expand_path('../remove_task.rake', __FILE__)

remove_task('db:schema:load')
namespace :db do
  namespace :schema do
    desc 'Overrides the `db:schema:load` rake  in order to load legacy schema before running the default `db:schema:load` task'
    task load: [:load_config, :environment] do
      ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, 'db/legacy.rb')
      ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, ENV['SCHEMA'])
    end
  end
end