Pushing a document onto one-sided N:N relation no longer updates parent

[mgartner]

The release of origin 1.0.11 has left me a little bit lost. In one of my apps, pushing a document onto a one-sided N:N relation doesn't update the document being pushed to. For example:

class Band
  include Mongoid::Document
  has_and_belongs_to_many :tags
end

class Tag
  include Mongoid::Document
end

band = Band.create
tag = Tag.first

band.tags << tag

# Before the release of origin 1.0.11, the band variable would be updated and the below would
# print "1". 
puts band.tags.count  # => 0

band.reload
puts band.tags.count # => 1

However, I've tried to rigorously reproduce the bug in a new app, but am unable to do so, and I believe I've used the same DB structure exactly. I'm baffled as to why I can't reproduce it.

I believe the issue can be traced to the commit fd6ede1, though I have limited knowledge as to the details of the source code.

Any ideas about this would be much appreciated.

[durran]

Which version of Mongoid are you running. In order for this update of Origin to play nicely you'd need to be on Mongoid 3.0.14, since we handle the changes after this commit: https://github.com/mongoid/mongoid/commit/ba4f54da3a27ce36b641d54e728e3ce56f69de19

[mgartner]

I'm running off the master branch instead of a stable release. But it looks like that contains that commit, correct?

[durran]

Just tested in Mongoid master and 3.1.0-stable and this code is correctly returning 1 for the counts.