Mobility + JSONB bug

mobility_jsonb_blank.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  gem "rails", "6.1.4.1"
  gem "pg", "1.2.3"
  gem "mobility", "1.2.2"
end

require "active_record"
require "minitest/autorun"
require "logger"
require "mobility"

Mobility.configure do
  plugins do
    active_record
  end
end

ActiveRecord::Base.establish_connection(adapter: "postgresql", database: "mobility_test")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :properties, force: true do |t|
    t.jsonb :name_i18n, default: {}, null: false
    t.jsonb :long_name_i18n
  end
end

class PropertyWithoutMobility < ActiveRecord::Base
  self.table_name = "properties"
end

class PropertyWithMobility < ActiveRecord::Base
  self.table_name = "properties"
  extend Mobility
  translates :name, backend: :jsonb, column_suffix: "_i18n"
  translates :long_name, backend: :jsonb, column_suffix: "_i18n"
end

class BugTest < Minitest::Test
  def test_without_mobility_reading_from_not_null_column
    property = PropertyWithoutMobility.create!
    property.reload
    assert_equal({}, property.name_i18n)
    assert_equal({}, property.changes)
  end

  def test_without_mobility_reading_from_null_column
    property = PropertyWithoutMobility.create!
    property.reload
    assert_nil property.long_name_i18n
    assert_equal({}, property.changes)
  end

  def test_with_mobility_reading_from_not_null_column
    property = PropertyWithMobility.create!
    property.reload
    assert_equal({}, property.name_i18n)
    assert_equal({}, property.changes)
  end

  def test_with_mobility_reading_from_null_column
    property = PropertyWithMobility.create!
    property.reload
    assert_nil property.long_name_i18n
    assert_equal({}, property.changes)
  end
end