Issue with STI and polymorphism

[TaylorMerritt]

There seems to be an issue with selecting the appropriate type for use in a query when STI is involved.

class Parent
  ...
end

class Child
  has_one :information
end

class Information
 belongs_to :informationable, polymorphic: true
end

Attempting to use deep_pluck while create a query like the following:

> Child.deep_pluck(deep_information: [:id, :name])
...
SELECT informations.id, informations.name FROM "informations" WHERE ("informations"."informationable_type" = 'Child')

Comparatively, rails uses the parent of the STI for this query:

> Child.all.first.information 
...
SELECT informations.* FROM "informations" WHERE ("informations"."informationable_type" = 'Parent') AND ("informations"."informationable_id" = ...)

It seems like maybe this line needs to be addressed, but I'm not sure: https://github.com/khiav223577/deep_pluck/blob/master/lib/deep_pluck/model.rb#L120

[khiav223577]

Hi @taylor-au , thanks for your report. Could you create an executable test case? See: https://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#create-an-executable-test-case for more details.

---

I wrote some test cases and found it works fine. See the test cases in the following:

begin
  require 'bundler/inline'
rescue LoadError => e
  warn 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'deep_pluck', '~> 1.1.6'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table 'parent', force: :cascade do |t|
    t.string :name
  end

  create_table 'children', force: :cascade do |t|
    t.string :name
  end

  create_table 'information', force: :cascade do |t|
    t.string :name
    t.string :informationable_type
    t.integer :informationable_id
  end
end

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

class Parent < ApplicationRecord
end

class Child < ApplicationRecord
  has_one :information, as: :informationable
end

class Information < ApplicationRecord
  belongs_to :informationable, polymorphic: true
end

class BugTest < Minitest::Test
  def setup
    Child.create!(name: 'Child A', information: Information.new(name: 'Info A'))
  end

  def test_deep_pluck
    assert_equal Child.deep_pluck(:name, information: [:name]), [
      { 'name' => 'Child A', :information => { 'name' => 'Info A' } }
    ]
  end

  def test_model
    assert_equal Child.all.first.information.name, 'Info A'
  end
end

[TaylorMerritt]

This issue turned out to be an issue with the way my code was setup and Rails' STI pattern. It revolves around having multiple associations with another model that has a STI pattern and also associating with the parent class of the STI directly.

Small example of what was happening is say you have the following class:

class Consumer
  has_one :contact, as: :contactable
  has_one :main_contact, as: :contactable, class_name: 'MainContact' # MainContact is a child of Contact
end

Consumer.deep_pluck(contact: :name) will pluck contacts with a type of MainContact also. Was just a misunderstanding on my part of that part of STI.

Thanks for taking a look into this though!