The problem I was encountering is that history doesn't make it easy to
differentiate between collections and non-collections very well:
inspect(obj).attrs.intcolumn.history.unchanged returns return [intval],
rather than intval.
inspect(obj).attrs.children.history.unchanged returns [<childobj>]
It'd be handy if I can just do something like:
original = get_original(self)
if original.value != self.value:
pass
With some sufficiently-robust-but-should-be-simple implementation of
get_history.
The main problem with Jonathan's approach is the results will be
inconsistent if any of the attributes are collections.
In my actual case at the moment, I know every attribute I'm going to look
at is a scalar, so inspect(self).attrs.target_attribute.non_added()[0]
"works" (provided this was loaded from the database at all and isn't a new
instance of the model). The problem is that I can't make easily write a
general case for this, because the [0] is required for scalars, but will
completely break when applied to any attribute that's a collection.
Michael: By "Losing changes", I mean that I know it's easily possible to
get to the unmodified version of an object via session.rollback() or
session.expire() -- but then I lose the pending (not yet committed) changes
that I'm trying to compare against. I wasn't referring to autoflush.
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