Merge pull request #7822 from lulalala/reset-counter-cache-for-has-many-through

Fix reset_counters crashing on has_many :through associations.
Conflicts:
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/counter_cache.rb

activerecord/CHANGELOG.md

@@ -1,5 +1,10 @@
 ## Rails 3.2.9 (unreleased)
 
+*   Fix `reset_counters` crashing on `has_many :through` associations.
+    Fix #7822.
+
+    *lulalala*
+
 *   ConnectionPool recognizes checkout_timeout spec key as taking
     precedence over legacy wait_timeout spec key, can be used to avoid
     conflict with mysql2 use of wait_timeout.  Closes #7684.

activerecord/lib/active_record/counter_cache.rb

@@ -25,8 +25,14 @@ module ActiveRecord
           self.name
         end
 
-        foreign_key  = has_many_association.foreign_key.to_s
-        child_class  = has_many_association.klass
+        if has_many_association.is_a? ActiveRecord::Reflection::ThroughReflection
+          foreign_key  = has_many_association.through_reflection.foreign_key.to_s
+          child_class = has_many_association.through_reflection.klass
+        else
+          foreign_key  = has_many_association.foreign_key.to_s
+          child_class  = has_many_association.klass
+        end
+
         belongs_to   = child_class.reflect_on_all_associations(:belongs_to)
         reflection   = belongs_to.find { |e| e.foreign_key.to_s == foreign_key && e.options[:counter_cache].present? }
         counter_name = reflection.counter_cache_column

activerecord/test/cases/counter_cache_test.rb

@@ -10,9 +10,12 @@ require 'models/dog'
 require 'models/dog_lover'
 require 'models/person'
 require 'models/friendship'
+require 'models/subscriber'
+require 'models/subscription'
+require 'models/book'
 
 class CounterCacheTest < ActiveRecord::TestCase
-  fixtures :topics, :categories, :categorizations, :cars, :dogs, :dog_lovers, :people, :friendships
+  fixtures :topics, :categories, :categorizations, :cars, :dogs, :dog_lovers, :people, :friendships, :subscribers, :subscriptions, :books
 
   class ::SpecialTopic < ::Topic
     has_many :special_replies, :foreign_key => 'parent_id'
@@ -118,4 +121,14 @@ class CounterCacheTest < ActiveRecord::TestCase
       Person.reset_counters(michael.id, :followers)
     end
   end
+
+  test "reset counter of has_many :through association" do
+    subscriber = subscribers('second')
+    Subscriber.reset_counters(subscriber.id, 'books')
+    Subscriber.increment_counter('books_count', subscriber.id)
+
+    assert_difference 'subscriber.reload.books_count', -1 do
+      Subscriber.reset_counters(subscriber.id, 'books')
+    end
+  end
 end

activerecord/test/models/subscription.rb

@@ -1,4 +1,4 @@
 class Subscription < ActiveRecord::Base
-  belongs_to :subscriber
+  belongs_to :subscriber, :counter_cache => :books_count
   belongs_to :book
 end

activerecord/test/schema/schema.rb

@@ -596,6 +596,7 @@ ActiveRecord::Schema.define do
   create_table :subscribers, :force => true, :id => false do |t|
     t.string :nick, :null => false
     t.string :name
+    t.column :books_count, :integer, :null => false, :default => 0
   end
   add_index :subscribers, :nick, :unique => true