Use filtered positional update operator to update nested arrays of embedded documents

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      In MongoDB 3.6, filtered positional update operator was added as described here: https://docs.mongodb.com/manual/reference/operator/update/positional-filtered/#update-nested-arrays-in-conjunction-with. This operator permits find-and-modify operations on nested arrays of embedded documents - specifically, it is free of the restriction of the positional update operator (https://docs.mongodb.com/manual/reference/operator/update/positional/) which only works with one level of nested arrays.

      Mongoid should use the filtered positional update operator to solve the following reported problem:

      This seems to have been fixed before but it doesn't use the positional operator when an embedded document has embedded documents.

      require 'mongoid'
Mongoid.connect_to 'embedded_positional_operators_test'
class Team
 include Mongoid::Document
embeds_many :players
field :name, type: String, default: ''
end
class Player
 include Mongoid::Document
 embeds_many :previous_teams
 embedded_in :team, inverse_of: :players
field :name, type: String, default: ''
end
class PreviousTeam
 include Mongoid::Document
embedded_in :player, inverse_of: :previous_teams
field :name, type: String, default: ''
 field :year, type: String, default: ''
end
Team.delete_all
Team.create!(name: 'Falcons')
falcons_instance_1 = Team.first
falcons_instance_2 = Team.first
falcons_instance_1.players.create!(name: 'Vidur', previous_teams: [{name: 'Eagles', year: '2018'}])
falcons_instance_2.players.create!(name: 'Jonathon', previous_teams: [{name: 'Paaaaaanthers', year: '2018'}])
me = falcons_instance_2.players.find_by(name: 'Jonathon')
# me.previous_teams.find_or_initialize_by(year: '2018').update(name: 'Panthers')
me.previous_teams.find_or_initialize_by(year: '2018').assign_attributes(name: 'Panthers')
me.save
Team.first.players.each do |player|
 previous_teams = player.previous_teams.each.map(&:name).join(', ')
 puts "Player Name: #{player.name}, Previous Teams: #{previous_teams}"
end

       
      So the expected print would be:
      Player Name: Vidur, Previous Teams: Eagles
      Player Name: Jonathon, Previous Teams: Panthers
       
      but it returns:
      Player Name: Vidur, Previous Teams: Panthers
      Player Name: Jonathon, Previous Teams: Paaaaaanthers

      it looks like the query being created is:

      Unable to find source-code formatter for language: mongodb. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml
      { q: { _id: ObjectId('5db0a55728f9d506e57a336d'), players._id: ObjectId('5db0a55728f9d506e57a3370') }, u: { $set: { players.0.previous_teams.0.name: "Panthers" } }

      And that first 0 should be the positional operator $.

      I looked through the code and found it was being done here and in there I see it uses positional operator only when nesting 1 level deep. Looking at the commit that added that im guessing its needed when the embedded document with the same name?

              Assignee:
              Unassigned
              Reporter:
              Jonathon Gardner
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                Created:
                Updated: