Orphaned attachment relationship safe navigation

closes rails#42514

- Adds Test for Orphaned Attachment Relationship
- Adds Changelog entry (with issue number)

Author: DRSisco

activestorage/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Attachments can be deleted after their association is no longer defined.
+
+    Fixes #42514
+
+    *Don Sisco*
+
 *   Allow to detach an attachment when record is not persisted
 
     *Jacopo Beschi*

activestorage/app/models/active_storage/attachment.rb

@@ -74,7 +74,7 @@ def purge_dependent_blob_later
     end
 
     def dependent
-      record.attachment_reflections[name]&.options[:dependent]
+      record.attachment_reflections[name]&.options&.fetch(:dependent, nil)
     end
 
     def variants

activestorage/test/models/attachment_test.rb

@@ -134,6 +134,14 @@ class ActiveStorage::AttachmentTest < ActiveSupport::TestCase
     assert_equal blob, ActiveStorage::Blob.find_signed(signed_id)
   end
 
+  test "can destroy attachment without existing relation" do
+    blob = create_blob
+    @user.highlights.attach(blob)
+    attachment = @user.highlights.find_by(blob_id: blob.id)
+    attachment.update_attribute(:name, "old_highlights")
+    assert_nothing_raised { attachment.destroy }
+  end
+
   private
     def assert_blob_identified_before_owner_validated(owner, blob, content_type)
       validated_content_type = nil