Merge pull request #8400 from matthewrobertson/has-many-through-counter-cache

Fix for has_many_through counter_cache bug

Counter caches were not being updated properly when replacing
has_many_through relationships.

4 files changed, 21 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index de386cd358..be3b6564b0 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,10 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Fix counter cache columns not updated when replacing `has_many :through`
+    associations.
+
+    *Matthew Robertson*
+
 *   Recognize migrations placed in directories containing numbers and 'rb'.
     Fix #8492
 
diff --git a/activerecord/activerecord-4.0.0.beta.gem b/activerecord/activerecord-4.0.0.beta.gem
new file mode 100644
index 0000000000..1309c478b8
--- /dev/null
+++ b/activerecord/activerecord-4.0.0.beta.gem
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index c7d8a84a7e..c3266f2bb4 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -153,6 +153,11 @@ module ActiveRecord
 
           delete_through_records(records)
 
+          if source_reflection.options[:counter_cache]
+            counter = source_reflection.counter_cache_column
+            klass.decrement_counter counter, records.map(&:id)
+          end
+
           if through_reflection.macro == :has_many && update_through_counter?(method)
             update_counter(-count, through_reflection)
           end
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 8e52ce1d91..2b96b42032 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -330,6 +330,17 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_update_counter_caches_on_replace_association
+    post = posts(:welcome)
+    tag  = post.tags.create!(:name => 'doomed')
+    tag.tagged_posts << posts(:thinking)
+
+    tag.tagged_posts = []
+    post.reload
+
+    assert_equal(post.taggings.count, post.taggings_count)
+  end
+
   def test_replace_association
     assert_queries(4){posts(:welcome);people(:david);people(:michael); posts(:welcome).people(true)}