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@@ -117,14 +117,7 @@ module ActiveRecord
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         # The attribute already has an unsaved change.
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         unless changed_attributes.include?(attr)
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           old = clone_attribute_value(:read_attribute, attr)
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-
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-          # Remember the original value if it's different.
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-          typecasted = if column = column_for_attribute(attr)
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-                         column.type_cast(value)
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-                       else
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-                         value
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-                       end
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-          changed_attributes[attr] = old unless old == typecasted
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+          changed_attributes[attr] = old if field_changed?(attr, old, value)
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         end
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         # Carry on.
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@@ -138,5 +131,20 @@ module ActiveRecord
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           update_without_dirty
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         end
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       end
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+
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+      def field_changed?(attr, old, value)
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+        if column = column_for_attribute(attr)
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+          if column.type == :integer && column.null && old.nil?
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+            # For nullable integer columns, NULL gets stored in database for blank (i.e. '') values.
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+            # Hence we don't record it as a change if the value changes from nil to ''.
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+            value = nil if value.blank?
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+          else
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+            value = column.type_cast(value)
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+          end
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+        end
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+
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+        old != value
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+      end
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+
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   end
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 end

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@@ -44,6 +44,16 @@ class DirtyTest < ActiveRecord::TestCase
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     assert_nil pirate.catchphrase_change
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   end
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+  def test_nullable_integer_not_marked_as_changed_if_new_value_is_blank
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+    pirate = Pirate.new
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+
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+    ["", nil].each do |value|
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+      pirate.parrot_id = value
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+      assert !pirate.parrot_id_changed?
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+      assert_nil pirate.parrot_id_change
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+    end
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+  end
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+
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   def test_object_should_be_changed_if_any_attribute_is_changed
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     pirate = Pirate.new
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     assert !pirate.changed?