Nested includes with polymorphic association throwing error in validate_includes!

[mhluska]

I have a controller with the following code:

render json: MenuSerializer.new(menus, include: %i[items.sellable.photos])

The serializers look like this:

class MenuSerializer < ApplicationSerializer
  has_many :items
end

class ItemSerializer < ApplicationSerializer
  belongs_to :sellable, polymorphic: true
end

# In this example, Car is a type of sellable.
class CarSerializer < ApplicationSerializer
  has_many :photos
end

class PhotoSerializer < ApplicationSerializer
  attribute :url
end

However, object_serializer throws the following error:

photos is not specified as a relationship on ItemSerializer

The offending line in the library seems to be:

raise ArgumentError, "#{parsed_include} is not specified as a relationship on #{klass.name}" unless relationship_to_include

If I change it to:

return unless relationship_to_include

Everything seems to work fine 🤷‍♂

[ThomasSevestre]

In case it helps, here is another fix :
https://github.com/ThomasSevestre/fast_jsonapi/blob/master/lib/fast_jsonapi/object_serializer.rb#L307-L311