ActiveRecord :inverse_of does not work for has_many :through on the join model on create

inverse_of does not work on join models on creation. This is either a bug or just a limitation in the implementation of inverse_of. Here’s an example:

class Challenge < ActiveRecord::Base
has_many :groups, :through => :group_challenges
has_many :group_challenges, :inverse_of => :challenge

attr_accessor :contact_ids
end

class GroupChallenge < ActiveRecord::Base
belongs_to :challenge, :inverse_of => :group_challenges
belongs_to :group, :inverse_of => :group_challenges

before_save :check_challenge

def check_challenge
Rails.logger.debug(“challenge.contact_ids: #{challenge.contact_ids}”)
end
end

class Group < ActiveRecord::Base
has_many :challenges, :through => :group_challenges
has_many :group_challenges, :inverse_of => :group
end

The GroupChallenge model does not reference the same Challenge when it is created via the associated Group

For example:

challenge = Challenge.new :groups => Group.all, :contact_ids => [1,2,3]

log output from GroupChallenge

=> challenge.contact_ids: []

However inverse_of does work when the models are reloaded

challenge.reload
challenge.group_challenges.first.challenge.contact_ids

log output => challenge.contact_ids: [1,2,3]

Is this a bug or just a limitation in the implementation of inverse_of ?