django/tests/m2m_signals/tests.py

"""
Testing signals emitted on changing m2m relations.
"""

from django.db import models
from django.test import TestCase

from .models import Car, Part, Person, SportsCar


class ManyToManySignalsTest(TestCase):
    @classmethod
    def setUpTestData(cls):
        cls.vw = Car.objects.create(name="VW")
        cls.bmw = Car.objects.create(name="BMW")
        cls.toyota = Car.objects.create(name="Toyota")

        cls.wheelset = Part.objects.create(name="Wheelset")
        cls.doors = Part.objects.create(name="Doors")
        cls.engine = Part.objects.create(name="Engine")
        cls.airbag = Part.objects.create(name="Airbag")
        cls.sunroof = Part.objects.create(name="Sunroof")

        cls.alice = Person.objects.create(name="Alice")
        cls.bob = Person.objects.create(name="Bob")
        cls.chuck = Person.objects.create(name="Chuck")
        cls.daisy = Person.objects.create(name="Daisy")

    def setUp(self):
        self.m2m_changed_messages = []

    def m2m_changed_signal_receiver(self, signal, sender, **kwargs):
        message = {
            "instance": kwargs["instance"],
            "action": kwargs["action"],
            "reverse": kwargs["reverse"],
            "model": kwargs["model"],
        }
        if kwargs["pk_set"]:
            message["objects"] = list(
                kwargs["model"].objects.filter(pk__in=kwargs["pk_set"])
            )
        self.m2m_changed_messages.append(message)

    def tearDown(self):
        # disconnect all signal handlers
        models.signals.m2m_changed.disconnect(
            self.m2m_changed_signal_receiver, Car.default_parts.through
        )
        models.signals.m2m_changed.disconnect(
            self.m2m_changed_signal_receiver, Car.optional_parts.through
        )
        models.signals.m2m_changed.disconnect(
            self.m2m_changed_signal_receiver, Person.fans.through
        )
        models.signals.m2m_changed.disconnect(
            self.m2m_changed_signal_receiver, Person.friends.through
        )

    def _initialize_signal_car(self, add_default_parts_before_set_signal=False):
        """Install a listener on the two m2m relations."""
        models.signals.m2m_changed.connect(
            self.m2m_changed_signal_receiver, Car.optional_parts.through
        )
        if add_default_parts_before_set_signal:
            # adding a default part to our car - no signal listener installed
            self.vw.default_parts.add(self.sunroof)
        models.signals.m2m_changed.connect(
            self.m2m_changed_signal_receiver, Car.default_parts.through
        )

    def test_pk_set_on_repeated_add_remove(self):
        """
        m2m_changed is always fired, even for repeated calls to the same
        method, but the behavior of pk_sets differs by action.

        - For signals related to `add()`, only PKs that will actually be
          inserted are sent.
        - For `remove()` all PKs are sent, even if they will not affect the DB.
        """
        pk_sets_sent = []

        def handler(signal, sender, **kwargs):
            if kwargs["action"] in ["pre_add", "pre_remove"]:
                pk_sets_sent.append(kwargs["pk_set"])

        models.signals.m2m_changed.connect(handler, Car.default_parts.through)

        self.vw.default_parts.add(self.wheelset)
        self.vw.default_parts.add(self.wheelset)

        self.vw.default_parts.remove(self.wheelset)
        self.vw.default_parts.remove(self.wheelset)

        expected_pk_sets = [
            {self.wheelset.pk},
            set(),
            {self.wheelset.pk},
            {self.wheelset.pk},
        ]
        self.assertEqual(pk_sets_sent, expected_pk_sets)

        models.signals.m2m_changed.disconnect(handler, Car.default_parts.through)

    def test_m2m_relations_add_remove_clear(self):
        expected_messages = []

        self._initialize_signal_car(add_default_parts_before_set_signal=True)

        self.vw.default_parts.add(self.wheelset, self.doors, self.engine)
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors, self.engine, self.wheelset],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors, self.engine, self.wheelset],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

        # give the BMW and Toyota some doors as well
        self.doors.car_set.add(self.bmw, self.toyota)
        expected_messages.append(
            {
                "instance": self.doors,
                "action": "pre_add",
                "reverse": True,
                "model": Car,
                "objects": [self.bmw, self.toyota],
            }
        )
        expected_messages.append(
            {
                "instance": self.doors,
                "action": "post_add",
                "reverse": True,
                "model": Car,
                "objects": [self.bmw, self.toyota],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

    def test_m2m_relations_signals_remove_relation(self):
        self._initialize_signal_car()
        # remove the engine from the self.vw and the airbag (which is not set
        # but is returned)
        self.vw.default_parts.remove(self.engine, self.airbag)
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.vw,
                    "action": "pre_remove",
                    "reverse": False,
                    "model": Part,
                    "objects": [self.airbag, self.engine],
                },
                {
                    "instance": self.vw,
                    "action": "post_remove",
                    "reverse": False,
                    "model": Part,
                    "objects": [self.airbag, self.engine],
                },
            ],
        )

    def test_m2m_relations_signals_give_the_self_vw_some_optional_parts(self):
        expected_messages = []

        self._initialize_signal_car()

        # give the self.vw some optional parts (second relation to same model)
        self.vw.optional_parts.add(self.airbag, self.sunroof)
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_add",
                "reverse": False,
                "model": Part,
                "objects": [self.airbag, self.sunroof],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_add",
                "reverse": False,
                "model": Part,
                "objects": [self.airbag, self.sunroof],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

        # add airbag to all the cars (even though the self.vw already has one)
        self.airbag.cars_optional.add(self.vw, self.bmw, self.toyota)
        expected_messages.append(
            {
                "instance": self.airbag,
                "action": "pre_add",
                "reverse": True,
                "model": Car,
                "objects": [self.bmw, self.toyota],
            }
        )
        expected_messages.append(
            {
                "instance": self.airbag,
                "action": "post_add",
                "reverse": True,
                "model": Car,
                "objects": [self.bmw, self.toyota],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

    def test_m2m_relations_signals_reverse_relation_with_custom_related_name(self):
        self._initialize_signal_car()
        # remove airbag from the self.vw (reverse relation with custom
        # related_name)
        self.airbag.cars_optional.remove(self.vw)
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.airbag,
                    "action": "pre_remove",
                    "reverse": True,
                    "model": Car,
                    "objects": [self.vw],
                },
                {
                    "instance": self.airbag,
                    "action": "post_remove",
                    "reverse": True,
                    "model": Car,
                    "objects": [self.vw],
                },
            ],
        )

    def test_m2m_relations_signals_clear_all_parts_of_the_self_vw(self):
        self._initialize_signal_car()
        # clear all parts of the self.vw
        self.vw.default_parts.clear()
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.vw,
                    "action": "pre_clear",
                    "reverse": False,
                    "model": Part,
                },
                {
                    "instance": self.vw,
                    "action": "post_clear",
                    "reverse": False,
                    "model": Part,
                },
            ],
        )

    def test_m2m_relations_signals_all_the_doors_off_of_cars(self):
        self._initialize_signal_car()
        # take all the doors off of cars
        self.doors.car_set.clear()
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.doors,
                    "action": "pre_clear",
                    "reverse": True,
                    "model": Car,
                },
                {
                    "instance": self.doors,
                    "action": "post_clear",
                    "reverse": True,
                    "model": Car,
                },
            ],
        )

    def test_m2m_relations_signals_reverse_relation(self):
        self._initialize_signal_car()
        # take all the airbags off of cars (clear reverse relation with custom
        # related_name)
        self.airbag.cars_optional.clear()
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.airbag,
                    "action": "pre_clear",
                    "reverse": True,
                    "model": Car,
                },
                {
                    "instance": self.airbag,
                    "action": "post_clear",
                    "reverse": True,
                    "model": Car,
                },
            ],
        )

    def test_m2m_relations_signals_alternative_ways(self):
        expected_messages = []

        self._initialize_signal_car()

        # alternative ways of setting relation:
        self.vw.default_parts.create(name="Windows")
        p6 = Part.objects.get(name="Windows")
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_add",
                "reverse": False,
                "model": Part,
                "objects": [p6],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_add",
                "reverse": False,
                "model": Part,
                "objects": [p6],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

        # direct assignment clears the set first, then adds
        self.vw.default_parts.set([self.wheelset, self.doors, self.engine])
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_remove",
                "reverse": False,
                "model": Part,
                "objects": [p6],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_remove",
                "reverse": False,
                "model": Part,
                "objects": [p6],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors, self.engine, self.wheelset],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors, self.engine, self.wheelset],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

    def test_m2m_relations_signals_clearing_removing(self):
        expected_messages = []

        self._initialize_signal_car(add_default_parts_before_set_signal=True)

        # set by clearing.
        self.vw.default_parts.set([self.wheelset, self.doors, self.engine], clear=True)
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_clear",
                "reverse": False,
                "model": Part,
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_clear",
                "reverse": False,
                "model": Part,
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors, self.engine, self.wheelset],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors, self.engine, self.wheelset],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

        # set by only removing what's necessary.
        self.vw.default_parts.set([self.wheelset, self.doors], clear=False)
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "pre_remove",
                "reverse": False,
                "model": Part,
                "objects": [self.engine],
            }
        )
        expected_messages.append(
            {
                "instance": self.vw,
                "action": "post_remove",
                "reverse": False,
                "model": Part,
                "objects": [self.engine],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

    def test_m2m_relations_signals_when_inheritance(self):
        expected_messages = []

        self._initialize_signal_car(add_default_parts_before_set_signal=True)

        # Signals still work when model inheritance is involved
        c4 = SportsCar.objects.create(name="Bugatti", price="1000000")
        c4b = Car.objects.get(name="Bugatti")
        c4.default_parts.set([self.doors])
        expected_messages.append(
            {
                "instance": c4,
                "action": "pre_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors],
            }
        )
        expected_messages.append(
            {
                "instance": c4,
                "action": "post_add",
                "reverse": False,
                "model": Part,
                "objects": [self.doors],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

        self.engine.car_set.add(c4)
        expected_messages.append(
            {
                "instance": self.engine,
                "action": "pre_add",
                "reverse": True,
                "model": Car,
                "objects": [c4b],
            }
        )
        expected_messages.append(
            {
                "instance": self.engine,
                "action": "post_add",
                "reverse": True,
                "model": Car,
                "objects": [c4b],
            }
        )
        self.assertEqual(self.m2m_changed_messages, expected_messages)

    def _initialize_signal_person(self):
        # Install a listener on the two m2m relations.
        models.signals.m2m_changed.connect(
            self.m2m_changed_signal_receiver, Person.fans.through
        )
        models.signals.m2m_changed.connect(
            self.m2m_changed_signal_receiver, Person.friends.through
        )

    def test_m2m_relations_with_self_add_friends(self):
        self._initialize_signal_person()
        self.alice.friends.set([self.bob, self.chuck])
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.alice,
                    "action": "pre_add",
                    "reverse": False,
                    "model": Person,
                    "objects": [self.bob, self.chuck],
                },
                {
                    "instance": self.alice,
                    "action": "post_add",
                    "reverse": False,
                    "model": Person,
                    "objects": [self.bob, self.chuck],
                },
            ],
        )

    def test_m2m_relations_with_self_add_fan(self):
        self._initialize_signal_person()
        self.alice.fans.set([self.daisy])
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.alice,
                    "action": "pre_add",
                    "reverse": False,
                    "model": Person,
                    "objects": [self.daisy],
                },
                {
                    "instance": self.alice,
                    "action": "post_add",
                    "reverse": False,
                    "model": Person,
                    "objects": [self.daisy],
                },
            ],
        )

    def test_m2m_relations_with_self_add_idols(self):
        self._initialize_signal_person()
        self.chuck.idols.set([self.alice, self.bob])
        self.assertEqual(
            self.m2m_changed_messages,
            [
                {
                    "instance": self.chuck,
                    "action": "pre_add",
                    "reverse": True,
                    "model": Person,
                    "objects": [self.alice, self.bob],
                },
                {
                    "instance": self.chuck,
                    "action": "post_add",
                    "reverse": True,
                    "model": Person,
                    "objects": [self.alice, self.bob],
                },
            ],
        )