Rails 8.1: NoMethodError when saving ActiveType::Object (NullPool#with_pool_transaction_isolation_level)

[cisolarix]

ActiveType::Object raises NoMethodError (undefined method 'with_pool_transaction_isolation_level' for an instance of ActiveRecord::ConnectionAdapters::NullPool) on Rails 8.1

Summary

Forms inheriting from ActiveType::Object start failing on Rails 8.1.0/8.1.1 because the internal dummy connection returns an ActiveRecord::ConnectionAdapters::NullPool that does not implement with_pool_transaction_isolation_level. Calling save ends up invoking connection.with_pool_transaction_isolation_level and raises NoMethodError.

Environment

• Ruby: 3.4.2
• Rails: 8.1.1 (regression not present on 8.0.x)
• ActiveType: 2.6.5
• Database: MySQL

Steps to Reproduce

1. Create a new Rails 8.1 project and add gem "active_type", "~> 2.6".

2. Define a form object:

   class SignupForm < ActiveType::Object
     attribute :mobile_phone, :string
   end

3. From a Rails console run:

   SignupForm.new(mobile_phone: '13800138000').save

Expected Behavior

save should execute without raising and return true (the same behavior observed on Rails 8.0.x).

Actual Behavior

A NoMethodError is raised:

NoMethodError (undefined method `with_pool_transaction_isolation_level' for ActiveRecord::ConnectionAdapters::NullPool:Class)

My guess

• ActiveType::Object relies on a dummy connection (see ActiveType::NoTable::DummyConnection), which now inherits the new NullPool in Rails 8.1. The pool no longer implements with_pool_transaction_isolation_level, so any transaction-related call fails.

• Rolling back to Rails 8.0.x restores the previous behavior.

• Monkey patching the form base class with a no-op transaction method avoids the crash, but it only masks the regression:

  def transaction
    yield
  end

Suggested Fix

Consider updating the dummy connection/pool returned by ActiveType::Object so that it responds to with_pool_transaction_isolation_level (even as a no-op), or bypass transaction handling entirely for non-persistent objects.

Thanks for maintaining ActiveType!

[kratob]

Hi @cisolarix,

Thanks for the detailed report! I've actually stumbled over this last week when working on an unrelated issue, but haven't gotten around to releasing a fix. I've pushed version 2.7.0 now, which should hopefully resolve your issue.