From 3ba2733d72ab368bab70e1480fc0de6b434a28d0 Mon Sep 17 00:00:00 2001
From: Tim Chater <t.chater@gmail.com>
Date: Tue, 17 Jun 2008 13:54:03 +0100
Subject: [PATCH] dirty fixed to record changes from zero to blank

---
 activerecord/lib/active_record/dirty.rb |    4 +++-
 activerecord/test/cases/dirty_test.rb   |   27 +++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletions(-)

diff --git a/activerecord/lib/active_record/dirty.rb b/activerecord/lib/active_record/dirty.rb
index b32e17e..a7d7674 100644
--- a/activerecord/lib/active_record/dirty.rb
+++ b/activerecord/lib/active_record/dirty.rb
@@ -142,9 +142,11 @@ module ActiveRecord
 
       def field_changed?(attr, old, value)
         if column = column_for_attribute(attr)
-          if column.type == :integer && column.null && old.nil?
+          if column.type == :integer && column.null && (old.nil? || old == 0)
             # For nullable integer columns, NULL gets stored in database for blank (i.e. '') values.
             # Hence we don't record it as a change if the value changes from nil to ''.
+            # If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll
+            # be typecast back to 0 (''.to_i => 0)
             value = nil if value.blank?
           else
             value = column.type_cast(value)
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index c011ffa..4fceef2 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -53,6 +53,33 @@ class DirtyTest < ActiveRecord::TestCase
       assert_nil pirate.parrot_id_change
     end
   end
+  
+  def test_zero_to_blank_marked_as_changed
+    pirate = Pirate.new
+    pirate.catchphrase = "Yarrrr, me hearties"
+    pirate.parrot_id = 1
+    pirate.save
+    
+    # check the change from 1 to ''
+    pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
+    pirate.parrot_id = ''
+    assert pirate.parrot_id_changed?
+    assert_equal([1, nil], pirate.parrot_id_change)
+    pirate.save
+    
+    # check the change from nil to 0
+    pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
+    pirate.parrot_id = 0
+    assert pirate.parrot_id_changed?
+    assert_equal([nil, 0], pirate.parrot_id_change)
+    pirate.save
+    
+    # check the change from 0 to ''
+    pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
+    pirate.parrot_id = ''
+    assert pirate.parrot_id_changed?
+    assert_equal([0, nil], pirate.parrot_id_change)
+  end
 
   def test_object_should_be_changed_if_any_attribute_is_changed
     pirate = Pirate.new
-- 
1.5.5.1