Deprecate automatic counter caches on has_many :through

Reliant on https://github.com/rails/rails/pull/15747 but pulled to a
separate PR to reduce noise. `has_many :through` associations have the
undocumented behavior of automatically detecting counter caches.
However, the way in which it does so is inconsistent with counter caches
everywhere else, and doesn't actually work consistently.

As with normal `has_many` associations, the user should specify the
counter cache on the `belongs_to`, if they'd like it updated.

1 files changed, 5 insertions, 5 deletions

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 0fa34e829e..a85e020f0c 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -489,7 +489,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     post = posts(:welcome)
     tag  = post.tags.create!(:name => 'doomed')
 
-    assert_difference ['post.reload.taggings_count', 'post.reload.tags_count'], -1 do
+    assert_difference ['post.reload.tags_count'], -1 do
       posts(:welcome).tags.delete(tag)
     end
   end
@@ -499,7 +499,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     tag  = post.tags.create!(:name => 'doomed')
     post.update_columns(tags_with_destroy_count: post.tags.count)
 
-    assert_difference ['post.reload.taggings_count', 'post.reload.tags_with_destroy_count'], -1 do
+    assert_difference ['post.reload.tags_with_destroy_count'], -1 do
       posts(:welcome).tags_with_destroy.delete(tag)
     end
   end
@@ -509,7 +509,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     tag  = post.tags.create!(:name => 'doomed')
     post.update_columns(tags_with_nullify_count: post.tags.count)
 
-    assert_no_difference 'post.reload.taggings_count' do
+    assert_no_difference 'post.reload.tags_count' do
       assert_difference 'post.reload.tags_with_nullify_count', -1 do
         posts(:welcome).tags_with_nullify.delete(tag)
       end
@@ -524,14 +524,14 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     tag.tagged_posts = []
     post.reload
 
-    assert_equal(post.taggings.count, post.taggings_count)
+    assert_equal(post.taggings.count, post.tags_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
+    assert_difference 'post.reload.tags_count', -1 do
       tag.tagged_posts.destroy(post)
     end
   end