Merge pull request #12748 from dm1try/fix_counter_cache_for_through_association

Fixes #11079, prevent the counter cache from being decremented twice when destroying a record on a has_many :through association

3 files changed, 17 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 54c243951d..524a048c7c 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Prevent the counter cache from being decremented twice when destroying
+    a record on a has_many :through association.
+
+    Fixes #11079.
+
+    *Dmitry Dedov*
+
 *   Unify boolean type casting for `MysqlAdapter` and `Mysql2Adapter`.
     `type_cast` will return `1` for `true` and `0` for `false`.
 
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 56331bbb0b..31b8d27892 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -163,7 +163,7 @@ module ActiveRecord
 
           delete_through_records(records)
 
-          if source_reflection.options[:counter_cache]
+          if source_reflection.options[:counter_cache] && method != :destroy
             counter = source_reflection.counter_cache_column
             klass.decrement_counter counter, records.map(&:id)
           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 c450b1beb5..47592f312e 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -514,6 +514,15 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal(post.taggings.count, post.taggings_count)
   end
 
+  def test_update_counter_caches_on_destroy
+    post = posts(:welcome)
+    tag  = post.tags.create!(name: 'doomed')
+
+    assert_difference 'post.reload.taggings_count', -1 do
+      tag.tagged_posts.destroy(post)
+    end
+  end
+
   def test_replace_association
     assert_queries(4){posts(:welcome);people(:david);people(:michael); posts(:welcome).people(true)}