Revert #1108 (lorint's STI fix)

This partially reverts commit 58369e1.
I have kept the specs, skipped.

Per the following, this approach does not seem to be working:

- #1135
- #1137
- seanlinsley#1

CHANGELOG.md

@@ -20,14 +20,6 @@ respectively.
 
 - `paper_trail-association_tracking` is no longer a runtime dependency. If you
   use it (`track_associations = true`) you must now add it to your own `Gemfile`.
-- [#1108](https://github.com/paper-trail-gem/paper_trail/pull/1108) -
-  In `versions.item_type`, we now store the subclass name instead of
-  the base_class.
-  - You must migrate existing `versions` records if you use
-    [STI][1]. A migration generator has been provided. Generator `update_sti`
-    creates a migration that updates existing `version` entries such that
-    `item_type` then refers to the specific class name instead of base_class.
-    See [5.c. Generators][2] for instructions.
 - [#1130](https://github.com/paper-trail-gem/paper_trail/pull/1130) -
   Removed `save_changes`. For those wanting to save space, it's more effective
   to drop the `object` column. If you need ultimate control over the
@@ -1060,6 +1052,3 @@ in the `PaperTrail::Version` class through a `Rails::Engine` when the gem is use
   - [#160](https://github.com/paper-trail-gem/paper_trail/pull/160) - Fixed failing tests and resolved out of date dependency issues.
   - [#157](https://github.com/paper-trail-gem/paper_trail/pull/157) - Refactored `class_attribute` names on the `ClassMethods` module
     for names that are not obviously pertaining to PaperTrail to prevent method name collision.
-
-[1]: https://api.rubyonrails.org/v5.2.0/classes/ActiveRecord/Base.html#class-ActiveRecord::Base-label-Single+table+inheritance
-[2]: https://github.com/paper-trail-gem/paper_trail/blob/master/README.md#5c-generators

README.md

@@ -934,15 +934,8 @@ class Banana < Fruit
 end
 ```
 
-A change in what `item_type` stores for subclassed models was introduced in
-[PR#1108](https://github.com/paper-trail-gem/paper_trail/pull/1108), recording
-the subclass name instead of the base class. This simplifies
-reifying through associations, and allows for a change in PT-AT that fixes
-[issue 594](https://github.com/paper-trail-gem/paper_trail/issues/594).
-
-For those that have existing version data from STI models, `item_type` can be
-updated by using a generator, `rails generate paper_trail:update_sti`.  More
-information is found in section [5.c. Generators](#5c-generators).
+However, there is a known issue when reifying [associations](#associations),
+see https://github.com/paper-trail-gem/paper_trail/issues/594
 
 ### 5.b. Configuring the `versions` Association
 
@@ -962,97 +955,27 @@ Overriding associations is not recommended in general.
 
 ### 5.c. Generators
 
-#### `paper_trail:install`
-
-Used to set up PT for the first time. Writes, but does not run, a migration
-file. Creates an initializer for configuration. The migration adds the
-`versions` table.
+PaperTrail has one generator, `paper_trail:install`. It writes, but does not
+run, a migration file.  It also creates a PaperTrail configuration initializer.
+The migration adds (at least) the `versions` table. The
+most up-to-date documentation for this generator can be found by running `rails
+generate paper_trail:install --help`, but a copy is included here for
+convenience.
 
 ```
 Usage:
-  rails generate paper_trail:install --help
   rails generate paper_trail:install [options]
 
 Options:
-  # Includes the `object_changes` column, for storing changeset (diff) with each version
-  [--with-changes], [--no-with-changes]
+  [--with-changes], [--no-with-changes]            # Store changeset (diff) with each version
 
 Runtime options:
   -f, [--force]                    # Overwrite files that already exist
   -p, [--pretend], [--no-pretend]  # Run but do not make any changes
   -q, [--quiet], [--no-quiet]      # Suppress status output
   -s, [--skip], [--no-skip]        # Skip files that already exist
-```
-
-#### `paper_trail:update_sti`
-
-Updates `versions.item_type` from base class name to subclass name. If you use
-STI, and you have records in `versions` created prior to
-[#1108](https://github.com/paper-trail-gem/paper_trail/pull/1108), you must run
-this migration.
-
-Writes, but does not run, a migration. The migration scans existing data in the
-versions table to identify models which use STI. Upon finding each entry which
-refers to an object from a subclassed model, `versions.item_type` is updated to
-reflect the subclass name, providing full compatibility with how the `versions`
-association works after PR#1108. In order to more quickly update a large volume
-of version records, updates are batched to affect 100 records at a time.
-
-Hints can be used in rare cases when the STI structure is modified over time
-such as when establishing additional intermediary inheritance structure,
-pointing to a new base class, abandoning STI entirely, or changing the name of
-the inheritance_column. The vast majority of users will probably never need to
-supply hints when using this generator.
-
-Let's give an example where the inheritance_column is changed, say originally
-there is an Animal class that uses the default `type` column, but after
-generating 500 Bird and Cat objects is modified to instead use the `species`
-column with a line like this:
-
-```
-Animal.inheritance_column = "species"
-```
-
-With this change a hint can be used to build the migration in a way that
-indicates how to treat the older records. For those first 500 Animal objects,
-the `item_type` should be derived from `type`, and for the rest, from `species`.
-We would need to research the ID numbers for versions that utilise `type` in the
-`object` and `object_changes` data. In this example let's say that those first
-500 Animals had version IDs between 249 and 1124. These objects would have been
-created having an `item_type` of Animal prior to PR#1108. Of course versions
-representing all manner of other changes would also be intermingled along with
-creates and updates for Animal objects. Perhaps another STI model exists for Car
-that inherits from Vehicle, and 50 Car objects were also built around the same
-timeframe as Bird and Cat objects, with various creates and updates for those
-being referened in versions with IDs from 382 to 516. For Vehicle let's say that
-initially the inheritance_column was set to `kind`, but then it changed to
-something else after ID 516 in the versions table. In this situation, to
-properly use the generator then these hints can be supplied:
-
-`rails generate update_sti Animal(type):249..1124 Vehicle(kind):382..516`
-
-The resulting migration will include these lines near the top:
-
-```
-# Versions of item_type "Animal" with IDs between 249 and 1124 will be updated based on `type`
-# Versions of item_type "Vehicle" with IDs between 382 and 516 will be updated based on `kind`
-hints = {"Animal"=>{249..1124=>"type"}, "Vehicle"=>{382..516=>"kind"}}
-```
-
-It is important to note that the IDs are not those of the Bird, Cat, or Car
-objects, but rather the IDs from the create, update, and destroy entries in the
-versions table. As well, these hints are only needed in situations where the
-inheritance_column has changed at some point in time, or in cases where the
-entire STI structure is modified or is abandoned. It ultimately facilitates
-better reporting for historic subclassed items, and allows PT-AT to properly
-reify these historic objects through associations.
 
-Once you have run the migration, please inform PaperTrail, so that it won't warn
-you about this.
-
-```
-# config/initializers/paper_trail.rb
-::PaperTrail.config.i_have_updated_my_existing_item_types = true
+Generates (but does not run) a migration to add a versions table.  Also generates an initializer file for configuring PaperTrail
 ```
 
 ### 5.d. Protected Attributes

lib/generators/paper_trail/install/USAGE → lib/generators/paper_trail/USAGE

@@ -1,3 +1,2 @@
 Description:
-  Generates (but does not run) a migration to add a versions table. See section
-  5.c. Generators in README.md for more information.
+  Generates (but does not run) a migration to add a versions table.

lib/generators/paper_trail/install/install_generator.rb → lib/generators/paper_trail/install_generator.rb

@@ -1,10 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "../migration_generator"
+require "rails/generators"
+require "rails/generators/active_record"
 
 module PaperTrail
   # Installs PaperTrail in a rails app.
-  class InstallGenerator < MigrationGenerator
+  class InstallGenerator < ::Rails::Generators::Base
+    include ::Rails::Generators::Migration
+
     # Class names of MySQL adapters.
     # - `MysqlAdapter` - Used by gems: `mysql`, `activerecord-jdbcmysql-adapter`.
     # - `Mysql2Adapter` - Used by `mysql2` gem.
@@ -22,16 +25,34 @@ class InstallGenerator < MigrationGenerator
     )
 
     desc "Generates (but does not run) a migration to add a versions table." \
-         "  Also generates an initializer file for configuring PaperTrail." \
-         "  See section 5.c. Generators in README.md for more information."
+         "  Also generates an initializer file for configuring PaperTrail"
 
     def create_migration_file
-      add_paper_trail_migration("create_versions",
-        item_type_options: item_type_options,
-        versions_table_options: versions_table_options)
+      add_paper_trail_migration("create_versions")
       add_paper_trail_migration("add_object_changes_to_versions") if options.with_changes?
     end
 
+    def self.next_migration_number(dirname)
+      ::ActiveRecord::Generators::Base.next_migration_number(dirname)
+    end
+
+    protected
+
+    def add_paper_trail_migration(template)
+      migration_dir = File.expand_path("db/migrate")
+      if self.class.migration_exists?(migration_dir, template)
+        ::Kernel.warn "Migration already exists: #{template}"
+      else
+        migration_template(
+          "#{template}.rb.erb",
+          "db/migrate/#{template}.rb",
+          item_type_options: item_type_options,
+          migration_version: migration_version,
+          versions_table_options: versions_table_options
+        )
+      end
+    end
+
     private
 
     # MySQL 5.6 utf8mb4 limit is 191 chars for keys used in indexes.
@@ -42,6 +63,13 @@ def item_type_options
       ", #{opt}"
     end
 
+    def migration_version
+      major = ActiveRecord::VERSION::MAJOR
+      if major >= 5
+        "[#{major}.#{ActiveRecord::VERSION::MINOR}]"
+      end
+    end
+
     def mysql?
       MYSQL_ADAPTERS.include?(ActiveRecord::Base.connection.class.name)
     end

lib/generators/paper_trail/install/templates/create_versions.rb.erb → lib/generators/paper_trail/templates/create_versions.rb.erb

@@ -25,7 +25,7 @@ class CreateVersions < ActiveRecord::Migration<%= migration_version %>
       # the `created_at` column.
       # (https://dev.mysql.com/doc/refman/5.6/en/fractional-seconds.html)
       #
-      # MySQL users should also upgrade to at least rails 4.2, which is the first
+      # MySQL users should also upgrade to rails 4.2, which is the first
       # version of ActiveRecord with support for fractional seconds in MySQL.
       # (https://github.com/rails/rails/pull/14359)
       #

lib/paper_trail/config.rb

@@ -16,8 +16,6 @@ class Config
 
     attr_accessor(
       :association_reify_error_behaviour,
-      :classes_warned_about_sti_item_types,
-      :i_have_updated_my_existing_item_types,
       :object_changes_adapter,
       :serializer,
       :version_limit

lib/paper_trail/events/destroy.rb

@@ -14,7 +14,7 @@ class Destroy < Base
       def data
         data = {
           item_id: @record.id,
-          item_type: @record.class.name,
+          item_type: @record.class.base_class.name,
           event: @record.paper_trail_event || "destroy",
           whodunnit: PaperTrail.request.whodunnit
         }