synonyms don't handle PropComparator; make more powerful synonym() function

[Mike Bayer]

the use case for synonym should be set up with something less verbose and which actually supports instrumentation: i.e.

class Foo(object):
    def _get_bar(self):
        return self._bar
    def _set_bar(self, value):
        self._bar = value

mapper(Foo, bar, properties={
    'someprop' : synonym('_bar', column=bar.c.somecol, getter=Foo._get_bar, setter=Foo._set_bar)
})

use two InstrumentedAttributes here, and have the 'someprop' InstrumentedAttribute replace its getter/setter with the custom ones sent in. have mapper._compile_property() pull out a separate ColumnProperty from the SynonymProperty (i.e. we use two MapperProperties here too).

[jek]

rather than getter=, etc., how about simply wrapping a user's 'property' instance with instrumentation. a synonym wrapper can reuse the impl guts from the base property.

    class AliasedAttribute(InstrumentedAttribute):
        def __init__(self, user_prop, orm_impl, comparator=None):
            self.user_prop = user_prop
            InstrumentedAttribute.__init__(self, orm_impl,
                                           comparator=comparator)
        def __get__(self, obj, owner):
            if obj is None:
                self.user_prop.__get__(obj, owner)                
                return self
            return self.user_prop.__get__(obj, owner)
        def __set__(self, obj, key, value):
            return self.user_prop.__set__(obj, key, value)
        def __delete__(self, obj, key):
            return self.user_prop.__delete__(obj, key)

[Mike Bayer]

that works just great. committed in 4ee70702230244569913da0de64f988ff0de06b8.

[Mike Bayer]

Removing milestone: 0.4.xx (automated comment)