import pickle

import django

from django.db import DJANGO_VERSION_PICKLE_KEY, models

from django.test import SimpleTestCase

class ModelPickleTests(SimpleTestCase):

    def test_missing_django_version_unpickling(self):

        """

        #21430 -- Verifies a warning is raised for models that are

        unpickled without a Django version

        """

        class MissingDjangoVersion(models.Model):

            title = models.CharField(max_length=10)

            def __reduce__(self):

                reduce_list = super().__reduce__()

                data = reduce_list[-1]

                del data[DJANGO_VERSION_PICKLE_KEY]

                return reduce_list

        p = MissingDjangoVersion(title="FooBar")

        msg = "Pickled model instance's Django version is not specified."

        with self.assertRaisesMessage(RuntimeWarning, msg):

            pickle.loads(pickle.dumps(p))

    def test_unsupported_unpickle(self):

        """

        #21430 -- Verifies a warning is raised for models that are

        unpickled with a different Django version than the current

        """

        class DifferentDjangoVersion(models.Model):

            title = models.CharField(max_length=10)

            def __reduce__(self):

                reduce_list = super().__reduce__()

                data = reduce_list[-1]

                data[DJANGO_VERSION_PICKLE_KEY] = "1.0"

                return reduce_list

        p = DifferentDjangoVersion(title="FooBar")

        msg = (

            "Pickled model instance's Django version 1.0 does not match the "

            "current version %s." % django.__version__

        )

        with self.assertRaisesMessage(RuntimeWarning, msg):

            pickle.loads(pickle.dumps(p))

    def test_with_getstate(self):

        """

        A model may override __getstate__() to choose the attributes to pickle.

        """

        class PickledModel(models.Model):

            def __getstate__(self):

                state = super().__getstate__().copy()

                del state["dont_pickle"]

                return state

        m = PickledModel()

        m.dont_pickle = 1

        dumped = pickle.dumps(m)

        self.assertEqual(m.dont_pickle, 1)

        reloaded = pickle.loads(dumped)

        self.assertFalse(hasattr(reloaded, "dont_pickle"))