Empty "update" versions when using active storage

[mochetts]

Thank you for your contribution!

Due to limited volunteers, issues that do not follow these instructions will be
closed without comment.

Check the following boxes:

• 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

Due to limited volunteers, we cannot answer usage questions. Please ask such
questions on StackOverflow.

I couldn't use the script template as I needs Rails to reproduce the bug. But I'm attaching a demo repo in which the bug reproduces.

1. Checkout this repository:
   https://github.com/mochetts/paper-trail-active-storage-bug

2. Run rails db:migrate to run migrations.

3. Run rake to run minitests.

4. See that the test fails:

Some analysis I've been doing:

It seems that Rails touches records when storing a has_one_attached relationship as per this bug report and its consequent fix.

This means that every time a new record is created with an associated attachment, it touches the model multiple times, generating multiple "update" versions for it with nil "object_changes". This seems to happen because the touch is occurring on creation, when there's no "updated_at" to touch.

Now the real question is if this is a Rails bug or a Papertrail bug, as it only happens under this scenario. Worthy to mention that rails forbids you from performing a touch on a new record, but under these circumstances it seems to be doing by itself.

I would suggest skipping the insertion of "update" versions when object_changes = nil, as these become noise in the versions history of the model.

I can send a PR for this, but I'd need confirmation that this is the right path.

[mochetts]

Note that this issue doesn't happen if you turn off version creation on touch events.

As in:

class User < ApplicationRecord
  has_paper_trail on: %i[create update delete]
end

[hasannadeem]

I'm facing the same issue