When generating xml with a custom implementation of serializable_hash,
if using the :except option, it was being overriden by the default AR
implementation that attempts to ignore the inheritance column from STI
automatically. So, if you have an implementation like this:
def serializable_hash(options={})
super({ except: %w(some_attr) }.merge!(options))
end
The :except option was correctly being used for :json generation, but
not for :xml, because the options hash already contained the :except
key with the inheritance column, thus overriding the customization.
This commit fixes this problem by removing the :except logic from the
xml serializer, that happened before calling serializable_hash. Since
serializable_hash also does the same check for inheritance column, this
logic was duplicated in both places, thus it's safe to remove it from
xml serializer (see ActiveRecord::Serialization#serializable_hash).
This is an attempt to solve issue #2498, that claims for a
"Single transformation API for both xml and json representations".
8b173f3bc5