allow the :converter Proc form composed_of to return nil

This makes it possible to filter invalid input values before they are passed
into the value-object (like empty strings). This behaviour is only relevant
if the :allow_nil options is set to true. Otherwise you will get
the resulting NoMethodError.

2 files changed, 23 insertions, 0 deletions

diff --git a/activerecord/test/cases/aggregations_test.rb b/activerecord/test/cases/aggregations_test.rb
index 3e0e6dce2c..5bd8f76ba2 100644
--- a/activerecord/test/cases/aggregations_test.rb
+++ b/activerecord/test/cases/aggregations_test.rb
@@ -109,6 +109,24 @@ class AggregationsTest < ActiveRecord::TestCase
     assert_nil customers(:david).gps_location
   end
 
+  def test_nil_return_from_converter_is_respected_when_allow_nil_is_true
+    customers(:david).non_blank_gps_location = ""
+    customers(:david).save
+    customers(:david).reload
+    assert_nil customers(:david).non_blank_gps_location
+  end
+
+  def test_nil_return_from_converter_results_in_failure_when_allow_nil_is_false
+    assert_raises(NoMethodError) do
+      customers(:barney).gps_location = ""
+    end
+  end
+
+  def test_do_not_run_the_converter_when_nil_was_set
+    customers(:david).non_blank_gps_location = nil
+    assert_nil Customer.gps_conversion_was_run
+  end
+
   def test_custom_constructor
     assert_equal 'Barney GUMBLE', customers(:barney).fullname.to_s
     assert_kind_of Fullname, customers(:barney).fullname
diff --git a/activerecord/test/models/customer.rb b/activerecord/test/models/customer.rb
index 777f6b5ba0..807f25b687 100644
--- a/activerecord/test/models/customer.rb
+++ b/activerecord/test/models/customer.rb
@@ -1,7 +1,12 @@
 class Customer < ActiveRecord::Base
+
+  cattr_accessor :gps_conversion_was_run
+
   composed_of :address, :mapping => [ %w(address_street street), %w(address_city city), %w(address_country country) ], :allow_nil => true
   composed_of :balance, :class_name => "Money", :mapping => %w(balance amount), :converter => Proc.new { |balance| balance.to_money }
   composed_of :gps_location, :allow_nil => true
+  composed_of :non_blank_gps_location, :class_name => "GpsLocation", :allow_nil => true, :mapping => %w(gps_location gps_location),
+              :converter => lambda { |gps| self.gps_conversion_was_run = true; gps.blank? ? nil : GpsLocation.new(gps)}
   composed_of :fullname, :mapping => %w(name to_s), :constructor => Proc.new { |name| Fullname.parse(name) }, :converter => :parse
 end