paper_trail: Redefinition of PaperTrail::Version stopped working in v12

Hello,

It seems that the v12 somehow interferes with Rails lazy autoloading in the development environment. The overriding class is no longer concerned. See below the script for more info.

---

Check the following boxes:

• This is not a usage question, this is a bug report
• This bug can be reproduced with the script I provide below ==> the script cannot be used because it does not rely on autoloading
• This bug can be reproduced in the latest release of the paper_trail gem

Due to limited volunteers, we cannot answer usage questions. Please ask such questions on StackOverflow.

Bug reports must use the following template:

# frozen_string_literal: true

# Use this template to report PaperTrail bugs.
# Please include only the minimum code necessary to reproduce your issue.
require "bundler/inline"

# STEP ONE: What versions are you using?
gemfile(true) do
  ruby "2.6.6"
  source "https://rubygems.org"
  gem "activerecord", "5.2.5"
  gem "minitest", "5.14.4"
  gem "paper_trail", "12.0.0", require: false
  gem "sqlite3", "1.4.2"
end

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

# Please use sqlite for your bug reports, if possible.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = nil
ActiveRecord::Schema.define do
  # STEP TWO: Define your tables here.
  create_table :users, force: true do |t|
    t.text :first_name, null: false
    t.timestamps null: false
  end

  create_table :versions do |t|
    t.string :item_type, null: false
    t.integer :item_id, null: false
    t.bigint :user_id, null: false
    t.string :event, null: false
    t.string :whodunnit
    t.text :object, limit: 1_073_741_823
    t.text :object_changes, limit: 1_073_741_823
    t.datetime :created_at
  end
  add_index :versions, %i[item_type item_id]
end
ActiveRecord::Base.logger = Logger.new(STDOUT)
require "paper_trail"

# STEP FOUR: Define your AR models here.
class User < ActiveRecord::Base
  has_paper_trail meta: {user: ->(item) { item }}

  validates_presence_of :first_name
end

module PaperTrail
  class Version < ActiveRecord::Base
    include PaperTrail::VersionConcern

    belongs_to :user

    validates_presence_of :user
  end
end

# STEP FIVE: Please write a test that demonstrates your issue.
class BugTest < ActiveSupport::TestCase
  def test_1
    assert_difference(-> { PaperTrail::Version.count }, +1) {
      User.create!(first_name: "Jane")
    }
  end
end

# STEP SIX: Run this script using `ruby my_bug_report.rb`

# Running:

D, [2021-04-06T14:36:22.417428 #91222] DEBUG -- :    (0.1ms)  SELECT COUNT(*) FROM "versions"
D, [2021-04-06T14:36:22.420818 #91222] DEBUG -- :    (0.0ms)  begin transaction
D, [2021-04-06T14:36:22.421598 #91222] DEBUG -- :   User Create (0.1ms)  INSERT INTO "users" ("first_name", "created_at", "updated_at") VALUES (?, ?, ?)  [["first_name", "Jane"], ["created_at", "2021-04-06 12:36:22.421102"], ["updated_at", "2021-04-06 12:36:22.421102"]]
D, [2021-04-06T14:36:22.435035 #91222] DEBUG -- :   PaperTrail::Version Create (0.1ms)  INSERT INTO "versions" ("item_type", "item_id", "user_id", "event", "object_changes", "created_at") VALUES (?, ?, ?, ?, ?, ?)  [["item_type", "User"], ["item_id", 1], ["user_id", 1], ["event", "create"], ["object_changes", "---\nid:\n-\n- 1\nfirst_name:\n-\n- Jane\ncreated_at:\n-\n- 2021-04-06 12:36:22.421102000 Z\nupdated_at:\n-\n- 2021-04-06 12:36:22.421102000 Z\n"], ["created_at", "2021-04-06 12:36:22.421102"]]
D, [2021-04-06T14:36:22.439861 #91222] DEBUG -- :    (0.1ms)  commit transaction
D, [2021-04-06T14:36:22.440312 #91222] DEBUG -- :    (0.1ms)  SELECT COUNT(*) FROM "versions"
.

Finished in 0.025732s, 38.8621 runs/s, 38.8621 assertions/s.

1 runs, 1 assertions, 0 failures, 0 errors, 0 skips

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The script runs well, but this is due to avoided autoloading (PaperTrail::Version is defined in the same script).

The problem is with Rails when PaperTrail::Version is redefined in another file (see: https://github.com/paper-trail-gem/paper_trail/blob/v12.0.0/README.md#5b2-item-association). This no longer works in development where autoloading is lazy.

Any advice?