Rails #18952 reproduction

gistfile1.rb

require 'active_record'
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Schema.define do
  create_table :somethings, force: true do |t|
    t.integer :age
    t.integer :count
  end
end

class Something < ActiveRecord::Base
  after_create -> do
    # Something.count returns different things depending
    # on how this object is created. :(
    self.count = Something.count
  end
end

require 'minitest/autorun'
class TestScope < Minitest::Test
  def setup
    Something.delete_all
  end

  def test_first_or_create
    s = Something.where(age: 20).create
    assert_equal 1, s.count

    s2 = Something.where(age: 21).first_or_create
    assert_equal 2, s2.count, "first_or_create keeps the scope"
  end

  def test_create_on_scope
    s = Something.where(age: 20).create
    assert_equal 1, s.count

    s2 = Something.where(age: 21).create
    assert_equal 2, s2.count, "create on a scope keeps the scope"
  end

  def test_create_with
    s = Something.where(age: 20).create
    assert_equal 1, s.count

    s2 = Something.create_with(age: 21)
    assert_equal 2, s2.count, "create_with keeps the scope"
  end

  def test_find_or_create_by
    s = Something.where(age: 20).create
    assert_equal 1, s.count

    s2 = Something.find_or_create_by(age: 21)
    assert_equal 2, s2.count, "find_or_create_by keeps the scope"
  end

  def test_first_or_initialize
    s = Something.where(age: 20).create
    assert_equal 1, s.count

    s2 = Something.where(age: 21).first_or_initialize
    s2.save
    assert_equal 2, s2.count, "first_or_initialize keeps the scope"
  end
end

gistfile2.sh

-- create_table(:somethings, {:force=>true})
   -> 0.0041s
Run options: --seed 17372

# Running:

.FFF.

Finished in 0.019590s, 255.2286 runs/s, 510.4571 assertions/s.

  1) Failure:
TestScope#test_first_or_create [minitest-thing.rb:29]:
first_or_create keeps the scope.
Expected: 2
  Actual: 1


  2) Failure:
TestScope#test_create_on_scope [minitest-thing.rb:37]:
create on a scope keeps the scope.
Expected: 2
  Actual: 1


  3) Failure:
TestScope#test_create_with [minitest-thing.rb:45]:
create_with keeps the scope.
Expected: 2
  Actual: 1

5 runs, 10 assertions, 3 failures, 0 errors, 0 skips