Remove a book's revision history when the book is destroyed

app/models/edit.rb

@@ -1,9 +1,11 @@
 class Edit < ApplicationRecord
   belongs_to :leaf
-  delegated_type :leafable, types: Leafable::TYPES, dependent: :destroy
+  delegated_type :leafable, types: Leafable::TYPES
 
   enum :action, %w[ revision trash ].index_by(&:itself)
 
+  after_destroy :destroy_superseded_leafable, if: :revision?
+
   scope :sorted, -> { order(created_at: :desc) }
   scope :before, ->(edit) { where("created_at < ?", edit.created_at) }
   scope :after, ->(edit) { where("created_at > ?", edit.created_at) }
@@ -15,4 +17,11 @@ def previous
   def next
     leaf.edits.after(self).first
   end
+
+  private
+    # A revision holds the leafable it superseded, which nothing else references. A trash
+    # edit shares the leaf's current leafable, and that one is the leaf's to destroy.
+    def destroy_superseded_leafable
+      leafable&.destroy
+    end
 end

app/models/leaf/editable.rb

@@ -4,7 +4,7 @@ module Leaf::Editable
   MINIMUM_TIME_BETWEEN_VERSIONS = 10.minutes
 
   included do
-    has_many :edits, dependent: :delete_all
+    has_many :edits, dependent: :destroy
 
     after_update :record_moved_to_trash, if: :was_trashed?
   end

lib/rails_ext/action_text_markdown.rb

@@ -36,7 +36,7 @@ module ActionText::Markdown::Uploads
   extend ActiveSupport::Concern
 
   included do
-    has_many_attached :uploads, dependent: :destroy
+    has_many_attached :uploads
   end
 end
 

test/models/book_test.rb

@@ -1,6 +1,8 @@
 require "test_helper"
 
 class BookTest < ActiveSupport::TestCase
+  include ActiveJob::TestHelper
+
   test "slug is generated from title" do
     book = Book.create!(title: "Hello, World!")
     assert_equal "hello-world", book.slug
@@ -40,4 +42,46 @@ class BookTest < ActiveSupport::TestCase
   test "markable returns empty string for book with no leaves" do
     assert_equal "", books(:manual).markable
   end
+
+  test "destroying a book removes superseded revisions along with their content and files" do
+    page = leaves(:welcome_page).page
+    page.body.uploads.attach io: file_fixture("pixel.bmp").open, filename: "pixel.bmp", content_type: "image/bmp"
+    upload_blob = page.body.uploads.blobs.sole
+    leaves(:welcome_page).edit leafable_params: { body: "Revised body" }
+
+    picture = leaves(:reading_picture).picture
+    image_blob = picture.image.blob
+    leaves(:reading_picture).edit leafable_params: { caption: "Revised caption" }
+
+    assert_equal page, leaves(:welcome_page).edits.revision.sole.leafable
+    assert_equal picture, leaves(:reading_picture).edits.revision.sole.leafable
+
+    perform_enqueued_jobs do
+      books(:handbook).destroy
+    end
+
+    assert_not Edit.exists?(leaf_id: leaves(:welcome_page, :reading_picture).map(&:id))
+    assert_not Page.exists?(page.id)
+    assert_not ActionText::Markdown.exists?(record: page)
+    assert_not Picture.exists?(picture.id)
+    assert_not ActiveStorage::Attachment.exists?(blob: [ upload_blob, image_blob ])
+    assert_not ActiveStorage::Blob.exists?(upload_blob.id)
+    assert_not ActiveStorage::Blob.exists?(image_blob.id)
+    assert_not ActiveStorage::Blob.service.exist?(upload_blob.key)
+    assert_not ActiveStorage::Blob.service.exist?(image_blob.key)
+  end
+
+  test "destroying a book removes the content a trashed leaf shares with its trash edit" do
+    page = leaves(:welcome_page).page
+    leaves(:welcome_page).trashed!
+
+    assert_equal page, leaves(:welcome_page).edits.trash.sole.leafable
+
+    books(:handbook).destroy
+
+    assert_not Leaf.exists?(leaves(:welcome_page).id)
+    assert_not Edit.exists?(leaf_id: leaves(:welcome_page).id)
+    assert_not Page.exists?(page.id)
+    assert_not ActionText::Markdown.exists?(record: page)
+  end
 end