[bug?] update_all lost data when using with $addToSet

[midnight-wonderer]

$addToSet is weird.

Here is the model:

class BuggyModel
  include ::Mongoid::Document
  store_in collection: 'buggy_models'

  field :list, type: :array, default: []
end

Create one element:

::BuggyModel.create!({ _id: 'test' })

Add something to the set:

::BuggyModel.update_all({
  '$addToSet': {
    list: 'a',
  },
})

Reload:

::BuggyModel.find('test').list

Expecting: ['a']
Actual: [nil]

Why?

[midnight-wonderer]

Digging further, the problem is in mongoize of Array fields that was called from hash.__consolidate__.

The workaround exists by omitting the type of the field.
Changing this:

field :list, type: :array, default: []

To this:

field :list, default: []

Probably Mongoid::Persistable::LIST_OPERATIONS handling needs revises.

[jamis]

Thank you for reporting this! I don't know how your post got past our radar, but I apologize for missing this. I've added a ticket to our tracking system here, if you'd like to follow along: https://jira.mongodb.org/browse/MONGOID-5686

[comandeo]

Since the issue was fixed, I am closing this discussion. @midnight-wonderer thank you again for reporting this!