Rails Bug in *_changed?

UPDATE: The latest rails has fixed this problem but this problem was still present in Rails 2.2.2.

The new dirty methods in Rails show this interesting result:

	u = Unit.find(123)
	u.position #=> 14
	u.position = "14"
	u.position_changed? #=> false
	u = Unit.find(42)
	u.position #=> 0
	u.position = "0"
	u.position_changed? #=> true

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The above code has position as a nullable integer column. When parameters come in a post via the parameters hash position comes across as a string. For 14 you get the Rails goodness and assigning "14" is not seen as a change - but why not the same thing for 0?

The problem is in the following offending code in vendor/rails/activerecord/lib/active_record/dirty.rb file. I have commented out the problem line (look for the no!!!!...) and added what I believe to be the correct code below it:

	def field_changed?(attr, old, value)
	if column = column_for_attribute(attr)
	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 no!!!!!!!!!!! not the else branch
	# value = column.type_cast(value)
	end
	value = column.type_cast(value)
	end
	old != value
	end

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