Fixed small inconsistency when handling aggregate's default_alias.

Refs django#14030.

Author: loic

django/db/models/query.py

@@ -288,7 +288,13 @@ def aggregate(self, *args, **kwargs):
  if self.query.distinct_fields:
  raise NotImplementedError("aggregate() + distinct(fields) not implemented.")
  for arg in args:
- if not hasattr(arg, 'default_alias'):
+ # The default_alias property may raise a TypeError, so we use
+ # a try/except construct rather than hasattr in order to remain
+ # consistent between PY2 and PY3 (hasattr would swallow
+ # the TypeError on PY2).
+ try:
+ arg.default_alias
+ except (AttributeError, TypeError):
  raise TypeError("Complex aggregates require an alias")
  kwargs[arg.default_alias] = arg
 
@@ -759,14 +765,16 @@ def annotate(self, *args, **kwargs):
  """
  annotations = OrderedDict() # To preserve ordering of args
  for arg in args:
+ # The default_alias property may raise a TypeError, so we use
+ # a try/except construct rather than hasattr in order to remain
+ # consistent between PY2 and PY3 (hasattr would swallow
+ # the TypeError on PY2).
  try:
- # we can't do an hasattr here because py2 returns False
- # if default_alias exists but throws a TypeError
  if arg.default_alias in kwargs:
  raise ValueError("The named annotation '%s' conflicts with the "
  "default name for another annotation."
  % arg.default_alias)
- except AttributeError: # default_alias
+ except (AttributeError, TypeError):
  raise TypeError("Complex annotations require an alias")
  annotations[arg.default_alias] = arg
  annotations.update(kwargs)

tests/aggregation/tests.py

@@ -768,10 +768,12 @@ def test_combine_different_types(self):
  self.assertEqual(b3.sums, Approximate(Decimal("383.69"), places=2))
 
  def test_complex_aggregations_require_kwarg(self):
- with six.assertRaisesRegex(self, TypeError, 'Complex expressions require an alias'):
+ with six.assertRaisesRegex(self, TypeError, 'Complex annotations require an alias'):
  Author.objects.annotate(Sum(F('age') + F('friends__age')))
  with six.assertRaisesRegex(self, TypeError, 'Complex aggregates require an alias'):
  Author.objects.aggregate(Sum('age') / Count('age'))
+ with six.assertRaisesRegex(self, TypeError, 'Complex aggregates require an alias'):
+ Author.objects.aggregate(Sum(Value(1)))
 
  def test_aggregate_over_complex_annotation(self):
  qs = Author.objects.annotate(