[1.2.X] Added sanity-checking of annotation alias names. Backport of [14092] from trunk.

        with data aggregated from related fields.

        """

        for arg in args:

            if arg.default_alias in kwargs:

                raise ValueError("The %s named annotation conflicts with the "

                                 "default name for another annotation."

                                 % arg.default_alias)

            kwargs[arg.default_alias] = arg

        names = set([f.name for f in self.model._meta.fields])

        for aggregate in kwargs:

            if aggregate in names:

                raise ValueError("The %s annotation conflicts with a field on "

                    "the model." % aggregate)

        obj = self._clone()

        obj._setup_aggregate_query(kwargs.keys())

            lambda b: b.name

        )

    def test_duplicate_alias(self):

        # Regression for #11256 - duplicating a default alias raises ValueError.

        self.assertRaises(ValueError, Book.objects.all().annotate, Avg('authors__age'), authors__age__avg=Avg('authors__age'))

    def test_field_name_conflict(self):

        # Regression for #11256 - providing an aggregate name that conflicts with a field name on the model raises ValueError

        self.assertRaises(ValueError, Author.objects.annotate, age=Avg('friends__age'))

    def test_pickle(self):

        # Regression for #10197 -- Queries with aggregates can be pickled.

        # First check that pickling is possible at all. No crash = success