Bug in modifier and trackable relation

[sarcilav]

When between the modifier model and trackable model you have more than one relation, when you try to write in the 'modifier' mongoid is returning the wrong relation.
I found that in mongoid/relations/bindings/referenced/in.rb the bind method is making something unexpected, it is returning for the modifier the second relation defined between the models, no the one that is created by mongoid-history in https://github.com/sarcilav/mongoid-history/blob/fixing-bug-when-trackable-modifier-has-more-than-one-relation/lib/mongoid/history/trackable.rb#L36 , I think that the problem is in the modifier you don't have to specify the relation, and it creates a weak relation.
I re-wrote two models in the integration test of mongoid-history to double check that the problem is on mongoid-history https://github.com/sarcilav/mongoid-history/blob/fixing-bug-when-trackable-modifier-has-more-than-one-relation/spec/integration/integration_spec.rb

[aq1018]

@scarliav

I used your branch, and rake spec failed miserably. I personally never used habtm in my projects, and don't really know what is going on here.

A brief test shows the following traceback:

NoMethodError: undefined method `map' for #<Post:0x000001010bb358>
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/attributes.rb:162:in `method_missing'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/referenced/many_to_many.rb:147:in `block in initialize'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/proxy.rb:33:in `call'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/proxy.rb:33:in `init'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/referenced/many_to_many.rb:145:in `initialize'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:60:in `new'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:60:in `create_relation'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:26:in `build'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:166:in `block (2 levels) in setter'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/extensions/object/yoda.rb:22:in `do_or_do_not'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/bindings/referenced/in.rb:40:in `bind'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/referenced/in.rb:30:in `bind'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/one.rb:21:in `block in load!'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/one.rb:19:in `tap'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/one.rb:19:in `load!'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:28:in `block in build'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:27:in `tap'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:27:in `build'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/relations/accessors.rb:166:in `block (2 levels) in setter'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/attributes/processing.rb:138:in `block in process_relations'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/attributes/processing.rb:133:in `each_pair'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/attributes/processing.rb:133:in `process_relations'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/attributes/processing.rb:121:in `process_pending'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/attributes/processing.rb:28:in `process'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/document.rb:130:in `initialize'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/persistence.rb:168:in `new'
    from /Users/aqian/.rvm/gems/ruby-1.9.2-p180/gems/mongoid-2.0.2/lib/mongoid/persistence.rb:168:in `create'

[aq1018]

If you are able to figure out the cause of it. I'd be glad to change / pull

Thanks!

[sarcilav]

About the specs my idea is to show that mongoid-history is falling on that situation :)

[matekb]

Was this ever solved? I am experiencing this with version 0.3.1 and mongoid 3.0.16.

[dblock]

@matekb Post a repro, ideally in a form of a test for mongoid-history and I can take a look.

[matekb]

I have written a test in branch Issue11 of https://github.com/matekb/mongoid-history/ that resembles my setup and problem. Please have a look!

Ohh, just saw that my commit was automatically referenced in the previous message. Nice!

[dblock]

So the problem is an ambiguous relationship with :user:

     Failure/Error: model.undo! user
     Mongoid::Errors::AmbiguousRelationship:

       Problem:
         Ambiguous relations :models, :external_model defined on User.
       Summary:
         When Mongoid attempts to set an inverse document of a relation in memory, it needs to know which relation it belongs to. When setting :modifier, Mongoid looked on the class Model for a matching relation, but multiples were found that could potentially match: :models, :external_model.
       Resolution:
         On the :modifier relation on Model you must add an :inverse_of option to specify the exact relationship on User that is the opposite of :modifier.

This is because the model already has a relationship with User, and adding a belongs_to :user without an :inverse_of is ambiguous. I added an :modifier_field_inverse_of option to track_history, so now you can do this:

      track_history   ...
                  :modifier_field => :modifier,
                  :modifier_field_inverse_of => nil, # no inverse modifier relationship

Let me know if that works.