Merge pull request #1323 from fx/association_primary_key

use association_primary_key in AssociationScope#add_constraints

activerecord/lib/active_record/associations/association_scope.rb

@@ -60,7 +60,7 @@ def add_constraints(scope)
 
             scope = scope.joins(join(
               join_table,
-              table[reflection.active_record_primary_key].
+              table[reflection.association_primary_key].
                 eq(join_table[reflection.association_foreign_key])
             ))
 

activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb

@@ -100,6 +100,16 @@ def test_should_property_quote_string_primary_keys
     assert_equal 'c1', record[0]
     assert_equal 't1', record[1]
   end
+  
+  def test_proper_usage_of_primary_keys_and_join_table
+    setup_data_for_habtm_case
+
+    assert_equal 'country_id', Country.primary_key
+    assert_equal 'treaty_id', Treaty.primary_key
+
+    country = Country.first
+    assert_equal 1, country.treaties.count
+  end
 
   def test_has_and_belongs_to_many
     david = Developer.find(1)