This app has a reproduction of an active record bug. To reproduce the bug, run:
rails db:migrate
rails test
You should see a failing test:
GroupTest#test_association_loads_correct_number_of_records [/Users/paul/dev/rails/myapp/test/models/group_test.rb:20]:
expected the first group to have 2 users.
Expected: 2
Actual: 3
The issue appears to be related to inverse_of. If you set up 2 models like this:
class User < ApplicationRecord
belongs_to :group, inverse_of: :users
end
class Group < ApplicationRecord
has_many :users, inverse_of: :group
end
Then create some data like this:
group = Group.create!(name: "Test")
john = User.create!(group: group, name: "John")
jane = User.create!(group: group, name: "Jane")
You can then run this code in the console to see the issue:
User.eager_load(:group => :users).where("users.id = ?", 1).first.group.users.map(&:name)
The result will be:
["John", "John", "Jane"]
This isn't what is expected. Since there are only 2 users in the group, it should be:
["John", "Jane"]