Rails core - Apr 2006 - has_many_through doesn''t retain existing object

I''ve got a has_many :through setup that works, but has a rub to
it.  This behavior happens with rel_1-1-0 *and* trunk (4169).
Here are the models:

  class Product < ActiveRecord::Base
    has_many :cart_items
    has_many :accounts, :through => :cart_items

  class CartItem < ActiveRecord::Base
    belongs_to :account
    belongs_to :product

  class Account < ActiveRecord::Base
    has_many :cart_items
    has_many :products, :through => :cart_items do
      def in_cart
        find :all, :conditions => ["order_id IS NULL"]
      end

      def previously_bought
        find :all, :conditions => ["order_id IS NOT NULL"]
      end
    end

Here is the test that triggers the issue:

  def test_add_to_freds_cart
    fred = Account.find_by_login("fred")
    product = Product.create(:sku => "XXXX",
                             :short_name => "Fred''s
product!",
                             :retail_price => Money.new(19291),
                             :wholesale_price => Money.new(17291),
                             :currency => "USD")
    assert_equal 0, fred.products.in_cart.size
    assert_equal 0, product.accounts.size
    cart_item = CartItem.create(:quantity => 3, :unit_price =>
Money.new(3000))
    fred.cart_items << cart_item
    product.cart_items << cart_item
    cart_item.save
    breakpoint
    assert_equal 1, fred.products.in_cart.size
    assert_equal 1, product.accounts.size
  end

When the breakpoint is hit, cart_items has a new row which
references this new product, and fred.

  >>> CartItem.find_all("product_id = 15")
  => [#<CartItem:0x2207710... "account_id"=>"5"...
"product_id"=>"15"...]

But look at what happens:

  >>> fred.products
  => [#<Product:0x223c028....  "id"=>"15"...]
  >>> product.accounts
  => []

product.accounts *should* contain fred, shouldn''t it?  When I
enter that line, no query is performed on the database.  The
only way I can get him to show up is to retrieve product again:

  >>> Product.find(15).accounts
  => [#<Account:0x2226fc0.... "login"=>"fred"...]

Is this a bug, or am I missing some elementary principle of
has_many?

Thanks.

-Drew

> Is this a bug, or am I missing some elementary principle of
> has_many?
Associations are cached.  Pass true to force a reload.

fred.products(true)

This is described under the ''Caching'' header in the docs:

http://rails.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

--
Rick Olson
http://techno-weenie.net