Can't validate money/currency presence in model

[rporrasluc]

Unless legacy_default_currency! is used, models can't be validated if currency is missing. Calling valid? on the method will read all attributes and so it will end up calling Helpers.value_to_currency(currency) with nil currency which will raise in absence of defaults.

Only if both value and currency are null (and coerce_null is false), the validation can be performed as read_money_attribute will return early if value is nil.

[csalvato]

Note, this means that, by default, an invalid record where currency is nil, calling record.validate will result in a Money::Currency::UnknownCurrency error instead of ActiveRecord::RecordInvalid error, which is a break in convention.