Major Description
ICU only uses the positive pattern of the textNumberPattern property to determine pad character and position, completely ignoring the negative pattern. If the positive pattern has no affix associated with the pad character, then there is an ambiguity if the pad character should appear before or after the negative affix when unparsing negative numbers. In this case, ICU defaults to before the affix, with no way to change it via the pattern. This effectively means it is not possible for ICU number padding to appear after a negative affix if there is no positive affix.
We need a way to specify that ICU pad characters should apper after an affix if the positive pattern does not have an affix.