Fix MONGOID-4874 Values seem to be lost when using add_to_set on a non-existent attribute on a loaded instance #4749
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It seems when an instance is loaded from a database, its `attributes` method returns an instance of `BSON::Document`. This causes some surprising behavior when we use `#add_to_set` on that loaded instance. It seems when a value is assigned to a `BSON::Document` instance, it gets modified: https://github.com/mongodb/bson-ruby/blob/master/lib/bson/document.rb#L87-L89 During modification, the attribute loses its reference to the original value, however the `add_to_set` method relies on this reference: https://github.com/mongodb/mongoid/blob/136ccbc140b25719f48ff5185bb471f90c063148/lib/mongoid/persistable/pushable.rb#L27-L31 Since that reference is broken, it no longer update the instance's attribute and the value is lost in memory, though still retained in the DB. This ensures that the reference remains intact.
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…n-existent attribute on a loaded instance (#4749) * Retain values added to sets of loaded instances It seems when an instance is loaded from a database, its `attributes` method returns an instance of `BSON::Document`. This causes some surprising behavior when we use `#add_to_set` on that loaded instance. It seems when a value is assigned to a `BSON::Document` instance, it gets modified: https://github.com/mongodb/bson-ruby/blob/master/lib/bson/document.rb#L87-L89 During modification, the attribute loses its reference to the original value, however the `add_to_set` method relies on this reference: https://github.com/mongodb/mongoid/blob/136ccbc140b25719f48ff5185bb471f90c063148/lib/mongoid/persistable/pushable.rb#L27-L31 Since that reference is broken, it no longer update the instance's attribute and the value is lost in memory, though still retained in the DB. This ensures that the reference remains intact. * expand test coverage * express the requirements more strictly Co-authored-by: Oleg Pudeyev <oleg@bsdpower.com>
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It seems when an instance is loaded from a database, its
attributesmethod returns an instance of
BSON::Document. This causes somesurprising behavior when we use
#add_to_seton that loaded instance.When a value is assigned to a
BSON::Documentinstance, it getsmodified:
https://github.com/mongodb/bson-ruby/blob/master/lib/bson/document.rb#L87-L89
During modification, the attribute loses its reference to the original
value, however the
add_to_setmethod relies on this reference:mongoid/lib/mongoid/persistable/pushable.rb
Lines 27 to 31 in 136ccbc
Since that reference is broken, it no longer update the instance's
attribute and the value is lost in memory, though still retained in the
DB.
This ensures that the reference remains intact.