Shared params don't get inherited like helper methods

The following code does not work:

# pagination.rb
module Pagination
  extend Grape::API::Helpers

  params :pagination do
    optional :page, type: Integer
    optional :per_page, type: Integer
  end

  def paginate(collection, page: params[:page], per_page: params[:per_page])
    collection.limit(per_page).offset((page - 1) * per_page)
  end
end

# posts.rb
module API
  class Posts < Grape::API
    namespace :posts do
      params do
        use :pagination
      end
      get do
        present :posts, paginate(Post.all)
      end
    end
  end
end

# base.rb
module API
  class Base < Grape::API
    helpers Pagination

    mount Posts
  end
end

when ran, it gives this error:

Params :pagination not found! (RuntimeError)

However this will work:

# posts.rb
module API
  class Posts < Grape::API
    helpers Pagination

    namespace :posts do
      params do
        use :pagination
      end
      get do
        present :posts, paginate(Post.all)
      end
    end
  end
end

and so will this:

# posts.rb
module API
  class Posts < Grape::API
    namespace :posts do
      params do
        optional :page, type: Integer
        optional :per_page, type: Integer
      end
      get do
        present :posts, paginate(Post.all)
      end
    end
  end
end

So the methods in helpers are available to mounted apis, but not the shared params.

I want to give a try at allowing this to work, could someone give me a starting point who is familiar with helpers / namespace stackable settings?

Start with the helper and namespace stackable-settings behavior described in pagination.rb, posts.rb, and base.rb, then reproduce the Params :pagination not found! error with the mounted API example. Compare shared-parameter lookup with helper lookup and verify that the mounted API can resolve the shared params while preserving the existing working examples.