Re: [Sqlalchemy-tickets] [sqlalchemy] #2872: AliasedClass.__getattr__() creates malformed QueryableAttribute

[sqlalchemy <mi...@zz...>]

#2872: AliasedClass.__getattr__() creates malformed QueryableAttribute
---------------------------+-------------------------------
      Reporter:  elic      |      Owner:  zzzeek
          Type:  defect    |     Status:  new
      Priority:  high      |  Milestone:  0.9.0
     Component:  orm       |   Severity:  major - 1-3 hours
    Resolution:            |   Keywords:
Progress State:  in queue  |
---------------------------+-------------------------------

Comment (by zzzeek):

 here's a patch I find even more interesting, that is, let the contract of
 `PropComparator.adapt_to_entity()` do the work.   the code here has really
 been kind of ad-hoc, thinking about it now might be shedding some clarity
 on what it's really supposed to be doing.  the tests all pass with this
 except for a few that have this odd reversal of expressions thing going
 on.

 {{{
 #!diff
 diff --git a/lib/sqlalchemy/orm/attributes.py
 b/lib/sqlalchemy/orm/attributes.py
 index 6071b56..a46977e 100644
 --- a/lib/sqlalchemy/orm/attributes.py
 +++ b/lib/sqlalchemy/orm/attributes.py
 @@ -149,6 +149,12 @@ class QueryableAttribute(interfaces._MappedAttribute,

          return self.comparator._query_clause_element()

 +    def adapt_to_entity(self, adapt_to_entity):
 +        assert not self._of_type
 +        return self.__class__(adapt_to_entity.entity, self.key,
 impl=self.impl,
 +
 comparator=self.comparator.adapt_to_entity(adapt_to_entity),
 +                           parententity=adapt_to_entity)
 +
      def of_type(self, cls):
          return QueryableAttribute(
                      self.class_,
 diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
 index 9737072..1b8f53c 100644
 --- a/lib/sqlalchemy/orm/util.py
 +++ b/lib/sqlalchemy/orm/util.py
 @@ -331,8 +331,10 @@ class AliasedClass(object):
              else:
                  raise AttributeError(key)

 -        if isinstance(attr, attributes.QueryableAttribute):
 -            return _aliased_insp._adapt_prop(attr, key)
 +        if isinstance(attr, PropComparator):
 +            ret = attr.adapt_to_entity(_aliased_insp)
 +            setattr(self, key, ret)
 +            return ret
          elif hasattr(attr, 'func_code'):
              is_method = getattr(_aliased_insp._target, key, None)
              if is_method and is_method.__self__ is not None:
 @@ -343,7 +345,8 @@ class AliasedClass(object):
              ret = attr.__get__(None, self)
              if isinstance(ret, PropComparator):
                  return ret.adapt_to_entity(_aliased_insp)
 -            return ret
 +            else:
 +                return ret
          else:
              return attr

 @@ -465,17 +468,6 @@ class AliasedInsp(_InspectionAttr):
                          'parentmapper': self.mapper}
                      )

 -    def _adapt_prop(self, existing, key):
 -        comparator = existing.comparator.adapt_to_entity(self)
 -        queryattr = attributes.QueryableAttribute(
 -                                self.entity, key,
 -                                impl=existing.impl,
 -                                parententity=self,
 -                                comparator=comparator)
 -        setattr(self.entity, key, queryattr)
 -        return queryattr
 -
 -
      def _entity_for_mapper(self, mapper):
          self_poly = self.with_polymorphic_mappers
          if mapper in self_poly:
 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2872#comment:2>
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