versions raises error whenever PaperTrail::Version is a parent to an abstract superclass

[searls]

• This is not a usage question, this is a bug report
• This bug can be reproduced with the script I provide below
• This bug can be reproduced in the latest release of the paper_trail gem

This is the exact same issue demonstrated 7 years ago on StackOverflow. In short, extending from PaperTrail::Version in an abstract class and then extending that abstract class to a concrete custom version model class will raise an error whenever #versions is called

Reproduction script

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  ruby "~> 3.3.0"
  gem "activerecord", "~> 7.1.3"
  gem "minitest", "~> 5.21.2"
  gem "paper_trail", "~> 15.1.0"
  gem "sqlite3", "~> 1.7.2"
end

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

ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = nil
ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
    t.text :first_name, null: false
    t.timestamps
  end

  create_table :user_versions do |t|
    t.string :item_type, null: false
    t.integer :item_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
end

ActiveRecord::Base.logger = Logger.new($stdout)
require "paper_trail"

class ApplicationVersion < PaperTrail::Version
  self.abstract_class = true
end

class UserVersion < ApplicationVersion
  self.table_name = :user_versions
end

class User < ActiveRecord::Base
  has_paper_trail versions: {
    class_name: "UserVersion"
  }
end

class ExtendingPaperTrailVersionWithCustomTable < ActiveSupport::TestCase
  def test_custom_table_fails
    user = User.create!(first_name: "Jane")
    user.versions
  end
end

This will fail with error:

  1) Error:
ExtendingPaperTrailVersionWithCustomTable#test_custom_table_fails:
ActiveRecord::StatementInvalid: Could not find table 'versions'

And anyone finding this via Google, this is the error you'll see in Postgres as opposed to sqlite:

PG::UndefinedTable: ERROR:  relation "versions" does not exist (ActiveRecord::StatementInvalid)
LINE 10:  WHERE a.attrelid = '"versions"'::regclass

Workaround

Changing ApplicationVersion to instead extend from ActiveRecord::Base and include PaperTrail::VersionConcern works, however:

class ApplicationVersion < ActiveRecord::Base
  include PaperTrail::VersionConcern
  self.abstract_class = true
end

Another workaround would be to eliminate the grandparent and have one's custom version classes extend directly from PaperTrail::Version. This also works:

class UserVersion < PaperTrail::Version
  self.table_name = :user_versions
end

Why did I do this to myself?

This example from the readme—ironically, about custom version class names—extends from PaperTrail::Version instead of including the concern

class UserVersion < PaperTrail::Version
  self.table_name = :user_versions
  belongs_to :user, foreign_key: :item_id
end

Since I wanted to own a custom ApplicationVersion from which all my custom versions could extend, I fell into this trap