Dirty: recognize when an integer changes from zero to blank. [#433 st…

…ate:resolved]

activerecord/lib/active_record/dirty.rb

@@ -142,9 +142,11 @@ def update_with_dirty
 
       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)

activerecord/test/cases/dirty_test.rb

@@ -55,6 +55,33 @@ def test_nullable_integer_not_marked_as_changed_if_new_value_is_blank
     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
     assert !pirate.changed?