Raise ActiveRecord::RecordNotSaved if an AssociationCollection fails to be replaced

activerecord/lib/active_record/associations/association_collection.rb

@@ -314,7 +314,11 @@ module ActiveRecord
 
         transaction do
           delete(@target - other_array)
-          concat(other_array - @target)
+
+          unless concat(other_array - @target)
+            raise RecordNotSaved, "Failed to replace #{@reflection.name} because one or more of the "
+                                  "new records could not be saved."
+          end
         end
       end
 

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -975,6 +975,19 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert !firm.clients.include?(:first_client)
   end
 
+  def test_replace_failure
+    firm = companies(:first_firm)
+    account = Account.new
+    orig_accounts = firm.accounts.to_a
+
+    assert !account.valid?
+    assert !orig_accounts.empty?
+    assert_raise ActiveRecord::RecordNotSaved do
+      firm.accounts = [account]
+    end
+    assert_equal orig_accounts, firm.accounts
+  end
+
   def test_get_ids
     assert_equal [companies(:first_client).id, companies(:second_client).id], companies(:first_firm).client_ids
   end