Re-slug HTML attachments if they are unpublished

app/models/attachment.rb

@@ -108,7 +108,9 @@ def publishing_api_details_for_format
   end
 
   def deep_clone
-    dup
+    dup.tap do |clone|
+      clone.safely_resluggable = false
+    end
   end
 
   def external?

app/models/html_attachment.rb

@@ -76,7 +76,7 @@ def url(options = {})
   def should_generate_new_friendly_id?
     return false unless sluggable_locale?
 
-    slug.nil? || attachable.nil? || !attachable.document.published?
+    slug.nil? || attachable.nil? || safely_resluggable?
   end
 
   def deep_clone

db/migrate/20210111161500_add_safely_resluggable_to_attachment.rb

@@ -0,0 +1,6 @@
+class AddSafelyResluggableToAttachment < ActiveRecord::Migration[5.1]
+  def change
+    add_column :attachments, :safely_resluggable, :boolean, default: true
+    Attachment.update_all(safely_resluggable: false)
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20201130161652) do
+ActiveRecord::Schema.define(version: 20210111161500) do
 
   create_table "about_pages", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci" do |t|
     t.integer "topical_event_id"
@@ -73,6 +73,7 @@
     t.string "external_url"
     t.string "content_id"
     t.boolean "deleted", default: false, null: false
+    t.boolean "safely_resluggable", default: true
     t.index ["attachable_id", "attachable_type"], name: "index_attachments_on_attachable_id_and_attachable_type"
     t.index ["attachable_type", "attachable_id", "ordering"], name: "no_duplicate_attachment_orderings", unique: true
     t.index ["attachment_data_id"], name: "index_attachments_on_attachment_data_id"

test/unit/html_attachment_test.rb

@@ -85,7 +85,7 @@ class HtmlAttachmentTest < ActiveSupport::TestCase
     assert_equal "an-html-attachment", draft.attachments.first.slug
   end
 
-  test "slug is updated when the title is changed if edition is unpublished" do
+  test "slug is updated when the title is changed if document has never been published" do
     attachment = build(:html_attachment, title: "an-html-attachment")
 
     create(:draft_publication, attachments: [attachment])
@@ -97,7 +97,7 @@ class HtmlAttachmentTest < ActiveSupport::TestCase
     assert_equal "a-new-title", attachment.slug
   end
 
-  test "slug is not updated when the title is changed if edition is published" do
+  test "slug on old attachment is not updated when the title is changed if document is published" do
     edition = create(
       :published_publication,
       attachments: [
@@ -114,6 +114,21 @@ class HtmlAttachmentTest < ActiveSupport::TestCase
     assert_equal "an-html-attachment", attachment.slug
   end
 
+  test "slug on new attachment is updated when the title is changed if document is published" do
+    edition = create(
+      :published_publication,
+    )
+    draft = edition.create_draft(create(:writer))
+    attachment = build(:html_attachment, title: "an-html-attachment")
+    draft.attachments = [attachment]
+
+    attachment.title = "a-new-title"
+    attachment.save!
+    attachment.reload
+
+    assert_equal "a-new-title", attachment.slug
+  end
+
   test "slug is not updated when the title has been changed in a prior published edition" do
     edition = create(
       :published_publication,