[ActiveRecord] PostgreSQL Adapter skips update on CIDR column when only netmask is changed

[dari-us]

Steps to reproduce

I cannot provide an executable test case of the exact problem since PostgreSQL cannot run in-memory easily, but I can demonstrate the underlying problem.
When I have a CIDR column in a PostgreSQL database with value 1.1.1.0/24 and I change it to 1.1.1.0/25, it will not be updated on save.

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem "rails"
end

require "active_record"
require "active_record/connection_adapters/postgresql/oid"
require "minitest/autorun"
require "logger"

ActiveRecord::Base.logger = Logger.new(STDOUT)

class BugTest < Minitest::Test
  def test_netmask_change
    type = ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Cidr.new()
    old_value = type.cast_value("1.1.1.0/24")

    new_str = "1.1.1.0/25"
    new_value = type.cast_value(new_str)

    assert type.changed?(old_value, new_value, new_str)
  end
end

Expected behavior

When old_value is in any way different from new_value, then changed? should return true.

Actual behavior

old_value (1.1.1.0/24) is treated as the same as new_value (1.1.1.0/25) which is obviously not the case.

Further notes

The cause of this problem is, that IPAddr#== ignores the netmask for its comparison.
To solve the problem, it is necessary to overwrite ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Cidr#changed? so it does not use IPAddr#== anymore. IPAddr#eql? is suitable for this, but may be overkill. There is an open issue addressing that IPAddr#== does not work as expected ruby/ipaddr#21

It is possible to monkey-patch ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Cidr to work as expected:

class ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Cidr
  def changed?(old_value, new_value, _new_value_before_type_cast)
    return old_value.nil? != new_value.nil? || (!old_value.nil? && !old_value.eql?(new_value))
  end
end

System configuration

Rails version: 7.1.3.2

Ruby version: 3.3.0