Counter cache columns are not marked as readonly [skip ci]

[fatkodima]

Counter caches were marked as readonly a very long time ago (rails 2),

rails/activerecord/lib/active_record/associations.rb

Lines 848 to 850 in c1bc61c

	module_eval(
	"#{reflection.class_name}.send(:attr_readonly,\"#{cache_column}\".intern) if defined?(#{reflection.class_name}) && #{reflection.class_name}.respond_to?(:attr_readonly)"
	)

but this is no longer true.

I was confused by this before, but I do not remember what I tested last time that it looked correct for me 🤦 😅 #44950

Reproducible test

# frozen_string_literal: true

require "bundler/inline"

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

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # gem "rails"
  # If you want to test against edge Rails replace the previous line with this:
  gem "rails", github: "rails/rails", branch: "main"

  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord.raise_on_assign_to_attr_readonly = true

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.integer :comments_count
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post, counter_cache: true
end

class BugTest < Minitest::Test
  def test_counter_cache
    post = Post.create!
    post.comments.create!

    assert Post.readonly_attributes.any?  # <---- fails

    assert_raises do  # <---- will also fail
      post.update!(comments_count: 10)
    end
  end
end

cc @jonathanhefner

[skipkayhil]

Changed here: 7b6720d#diff-084ec489ba3b9f2e388734a99876f0d94776111278acfe4901235dca570040c5R40 so that assigning values to a counter_cache column would not raise (I wonder if they should raise though 🤔)