Ensure we are not comparing a string with a symbol in HasManyAssociation#inverse_updates_counter_cache?. Fixes #2755, where a counter cache could be decremented twice as far as it was supposed to be.

activerecord/lib/active_record/reflection.rb

@@ -226,7 +226,7 @@ module ActiveRecord
         if options[:counter_cache] == true
           "#{active_record.name.demodulize.underscore.pluralize}_count"
         elsif options[:counter_cache]
-          options[:counter_cache]
+          options[:counter_cache].to_s
         end
       end
 

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -17,6 +17,7 @@ require 'models/invoice'
 require 'models/line_item'
 require 'models/car'
 require 'models/bulb'
+require 'models/engine'
 
 class HasManyAssociationsTestForCountWithFinderSql < ActiveRecord::TestCase
   class Invoice < ActiveRecord::Base
@@ -850,6 +851,15 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_clearing_updates_counter_cache_when_inverse_counter_cache_is_a_symbol_with_dependent_destroy
+    car = Car.first
+    car.engines.create!
+
+    assert_difference 'car.reload.engines_count', -1 do
+      car.engines.clear
+    end
+  end
+
   def test_clearing_a_dependent_association_collection
     firm = companies(:first_firm)
     client_id = firm.dependent_clients_of_firm.first.id

activerecord/test/models/car.rb

@@ -8,7 +8,7 @@ class Car < ActiveRecord::Base
   has_one :frickinawesome_bulb, :class_name => "Bulb", :conditions => { :frickinawesome => true }
 
   has_many :tyres
-  has_many :engines
+  has_many :engines, :dependent => :destroy
   has_many :wheels, :as => :wheelable
 
   scope :incl_tyres, includes(:tyres)