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Fixed #30421 -- Allowed symmetrical intermediate table for self-referential ManyToManyField.

This commit is contained in:
Nadège Michel 2019-04-19 18:12:04 +02:00 committed by Mariusz Felisiak
parent a9179ab032
commit 87b1ad6e73
11 changed files with 167 additions and 90 deletions
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1
AUTHORS
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@ -632,6 +632,7 @@ answer newbie questions, and generally made Django that much better:
msundstr
Mushtaq Ali <mushtaak@gmail.com>
Mykola Zamkovoi <nickzam@gmail.com>
Nadège Michel <michel.nadege@gmail.com>
Nagy Károly <charlie@rendszergazda.com>
Nasimul Haque <nasim.haque@gmail.com>
Nasir Hussain <nasirhjafri@gmail.com>

12
django/db/models/fields/related.py
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@ -1234,18 +1234,6 @@ class ManyToManyField(RelatedField):
to_model_name = to_model._meta.object_name
relationship_model_name = self.remote_field.through._meta.object_name
self_referential = from_model == to_model
# Check symmetrical attribute.
if (self_referential and self.remote_field.symmetrical and
not self.remote_field.through._meta.auto_created):
errors.append(
checks.Error(
'Many-to-many fields with intermediate tables must not be symmetrical.',
obj=self,
id='fields.E332',
)
)
# Count foreign keys in intermediate model
if self_referential:
seen_self = sum(

11
django/db/models/fields/related_descriptors.py
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@ -938,11 +938,14 @@ def create_forward_many_to_many_manager(superclass, rel, reverse):
through_defaults=through_defaults,
)
# If this is a symmetrical m2m relation to self, add the mirror
# entry in the m2m table. `through_defaults` aren't used here
# because of the system check error fields.E332: Many-to-many
# fields with intermediate tables must not be symmetrical.
# entry in the m2m table.
if self.symmetrical:
self._add_items(self.target_field_name, self.source_field_name, *objs)
self._add_items(
self.target_field_name,
self.source_field_name,
*objs,
through_defaults=through_defaults,
)
add.alters_data = True
def remove(self, *objs):

2
docs/ref/checks.txt
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@ -222,7 +222,7 @@ Related fields
* **fields.E331**: Field specifies a many-to-many relation through model
``<model>``, which has not been installed.
* **fields.E332**: Many-to-many fields with intermediate tables must not be
symmetrical.
symmetrical. *This check appeared before Django 3.0.*
* **fields.E333**: The model is used as an intermediate model by ``<model>``,
but it has more than two foreign keys to ``<model>``, which is ambiguous.
You must specify which two foreign keys Django should use via the

21
docs/ref/models/fields.txt
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@ -1537,6 +1537,11 @@ that control how the relationship functions.
add the descriptor for the reverse relationship, allowing
:class:`ManyToManyField` relationships to be non-symmetrical.
.. versionchanged:: 3.0
Specifying ``symmetrical=True`` for recursive many-to-many
relationships using an intermediary model was allowed.
.. attribute:: ManyToManyField.through
Django will automatically generate a table to manage many-to-many
@ -1549,6 +1554,16 @@ that control how the relationship functions.
:ref:`extra data with a many-to-many relationship
<intermediary-manytomany>`.
.. note::
Recursive relationships using an intermediary model and defined as
symmetrical (that is, with :attr:`symmetrical=True
<ManyToManyField.symmetrical>`, which is the default) can't determine
the reverse accessors names, as they would be the same. You need to set
a :attr:`~ForeignKey.related_name` to at least one of them. If you'd
prefer Django not to create a backwards relation, set ``related_name``
to ``'+'``.
If you don't specify an explicit ``through`` model, there is still an
implicit ``through`` model class you can use to directly access the table
created to hold the association. It has three fields to link the models.
@ -1624,12 +1639,6 @@ that control how the relationship functions.
foreign keys to the model, or you want to explicitly specify which two
Django should use.
Recursive relationships using an intermediary model are always defined as
non-symmetrical -- that is, with :attr:`symmetrical=False <ManyToManyField.symmetrical>`
-- therefore, there is the concept of a "source" and a "target". In that
case ``'field1'`` will be treated as the "source" of the relationship and
``'field2'`` as the "target".
.. attribute:: ManyToManyField.db_table
The name of the table to create for storing the many-to-many data. If this

3
docs/releases/3.0.txt
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@ -254,6 +254,9 @@ Models
* :class:`~django.db.models.FilePathField` now accepts a callable ``path``.
* Allowed symmetrical intermediate table for self-referential
:class:`~django.db.models.ManyToManyField`.
Requests and Responses
~~~~~~~~~~~~~~~~~~~~~~

64
tests/invalid_models_tests/test_relative_fields.py
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@ -260,24 +260,6 @@ class RelativeFieldTests(SimpleTestCase):
field = Group._meta.get_field('members')
self.assertEqual(field.check(from_model=Group), [])
def test_symmetrical_self_referential_field(self):
class Person(models.Model):
# Implicit symmetrical=False.
friends = models.ManyToManyField('self', through="Relationship")
class Relationship(models.Model):
first = models.ForeignKey(Person, models.CASCADE, related_name="rel_from_set")
second = models.ForeignKey(Person, models.CASCADE, related_name="rel_to_set")
field = Person._meta.get_field('friends')
self.assertEqual(field.check(from_model=Person), [
Error(
'Many-to-many fields with intermediate tables must not be symmetrical.',
obj=field,
id='fields.E332',
),
])
def test_too_many_foreign_keys_in_self_referential_model(self):
class Person(models.Model):
friends = models.ManyToManyField('self', through="InvalidRelationship", symmetrical=False)
@ -301,52 +283,6 @@ class RelativeFieldTests(SimpleTestCase):
),
])
def test_symmetric_self_reference_with_intermediate_table(self):
class Person(models.Model):
# Explicit symmetrical=True.
friends = models.ManyToManyField('self', through="Relationship", symmetrical=True)
class Relationship(models.Model):
first = models.ForeignKey(Person, models.CASCADE, related_name="rel_from_set")
second = models.ForeignKey(Person, models.CASCADE, related_name="rel_to_set")
field = Person._meta.get_field('friends')
self.assertEqual(field.check(from_model=Person), [
Error(
'Many-to-many fields with intermediate tables must not be symmetrical.',
obj=field,
id='fields.E332',
),
])
def test_symmetric_self_reference_with_intermediate_table_and_through_fields(self):
"""
Using through_fields in a m2m with an intermediate model shouldn't
mask its incompatibility with symmetry.
"""
class Person(models.Model):
# Explicit symmetrical=True.
friends = models.ManyToManyField(
'self',
symmetrical=True,
through="Relationship",
through_fields=('first', 'second'),
)
class Relationship(models.Model):
first = models.ForeignKey(Person, models.CASCADE, related_name="rel_from_set")
second = models.ForeignKey(Person, models.CASCADE, related_name="rel_to_set")
referee = models.ForeignKey(Person, models.CASCADE, related_name="referred")
field = Person._meta.get_field('friends')
self.assertEqual(field.check(from_model=Person), [
Error(
'Many-to-many fields with intermediate tables must not be symmetrical.',
obj=field,
id='fields.E332',
),
])
def test_foreign_key_to_abstract_model(self):
class AbstractModel(models.Model):
class Meta:

7
tests/m2m_recursive/models.py
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@ -22,7 +22,14 @@ from django.db import models
class Person(models.Model):
name = models.CharField(max_length=20)
friends = models.ManyToManyField('self')
colleagues = models.ManyToManyField('self', symmetrical=True, through='Colleague')
idols = models.ManyToManyField('self', symmetrical=False, related_name='stalkers')
def __str__(self):
return self.name
class Colleague(models.Model):
first = models.ForeignKey(Person, models.CASCADE)
second = models.ForeignKey(Person, models.CASCADE, related_name='+')
first_meet = models.DateField()

58
tests/m2m_recursive/tests.py
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@ -1,3 +1,5 @@
import datetime
from django.test import TestCase
from .models import Person
@ -59,3 +61,59 @@ class RecursiveM2MTests(TestCase):
self.a.idols.add(self.a)
self.assertSequenceEqual(self.a.idols.all(), [self.a])
self.assertSequenceEqual(self.a.stalkers.all(), [self.a])
class RecursiveSymmetricalM2MThroughTests(TestCase):
@classmethod
def setUpTestData(cls):
cls.a, cls.b, cls.c, cls.d = [
Person.objects.create(name=name)
for name in ['Anne', 'Bill', 'Chuck', 'David']
]
cls.a.colleagues.add(cls.b, cls.c, through_defaults={
'first_meet': datetime.date(2013, 1, 5),
})
# Add m2m for Anne and Chuck in reverse direction.
cls.d.colleagues.add(cls.a, cls.c, through_defaults={
'first_meet': datetime.date(2015, 6, 15),
})
def test_recursive_m2m_all(self):
for person, colleagues in (
(self.a, [self.b, self.c, self.d]),
(self.b, [self.a]),
(self.c, [self.a, self.d]),
(self.d, [self.a, self.c]),
):
with self.subTest(person=person):
self.assertSequenceEqual(person.colleagues.all(), colleagues)
def test_recursive_m2m_reverse_add(self):
# Add m2m for Anne in reverse direction.
self.b.colleagues.add(self.a, through_defaults={
'first_meet': datetime.date(2013, 1, 5),
})
self.assertSequenceEqual(self.a.colleagues.all(), [self.b, self.c, self.d])
self.assertSequenceEqual(self.b.colleagues.all(), [self.a])
def test_recursive_m2m_remove(self):
self.b.colleagues.remove(self.a)
self.assertSequenceEqual(self.a.colleagues.all(), [self.c, self.d])
self.assertSequenceEqual(self.b.colleagues.all(), [])
def test_recursive_m2m_clear(self):
# Clear m2m for Anne.
self.a.colleagues.clear()
self.assertSequenceEqual(self.a.friends.all(), [])
# Reverse m2m relationships is removed.
self.assertSequenceEqual(self.c.colleagues.all(), [self.d])
self.assertSequenceEqual(self.d.colleagues.all(), [self.c])
def test_recursive_m2m_set(self):
# Set new relationships for Chuck.
self.c.colleagues.set([self.b, self.d], through_defaults={
'first_meet': datetime.date(2013, 1, 5),
})
self.assertSequenceEqual(self.c.colleagues.order_by('name'), [self.b, self.d])
# Reverse m2m relationships is removed.
self.assertSequenceEqual(self.a.colleagues.order_by('name'), [self.b, self.d])

7
tests/m2m_through/models.py
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@ -72,6 +72,7 @@ class TestNoDefaultsOrNulls(models.Model):
class PersonSelfRefM2M(models.Model):
name = models.CharField(max_length=5)
friends = models.ManyToManyField('self', through="Friendship", symmetrical=False)
sym_friends = models.ManyToManyField('self', through='SymmetricalFriendship', symmetrical=True)
def __str__(self):
return self.name
@ -83,6 +84,12 @@ class Friendship(models.Model):
date_friended = models.DateTimeField()
class SymmetricalFriendship(models.Model):
first = models.ForeignKey(PersonSelfRefM2M, models.CASCADE)
second = models.ForeignKey(PersonSelfRefM2M, models.CASCADE, related_name='+')
date_friended = models.DateField()
# Custom through link fields
class Event(models.Model):
title = models.CharField(max_length=50)

71
tests/m2m_through/tests.py
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@ -1,4 +1,4 @@
from datetime import datetime
from datetime import date, datetime
from operator import attrgetter
from django.db import IntegrityError
@ -7,7 +7,7 @@ from django.test import TestCase
from .models import (
CustomMembership, Employee, Event, Friendship, Group, Ingredient,
Invitation, Membership, Person, PersonSelfRefM2M, Recipe, RecipeIngredient,
Relationship,
Relationship, SymmetricalFriendship,
)
@ -401,7 +401,7 @@ class M2mThroughReferentialTests(TestCase):
attrgetter("name")
)
def test_self_referential_symmetrical(self):
def test_self_referential_non_symmetrical_both(self):
tony = PersonSelfRefM2M.objects.create(name="Tony")
chris = PersonSelfRefM2M.objects.create(name="Chris")
Friendship.objects.create(
@ -439,6 +439,71 @@ class M2mThroughReferentialTests(TestCase):
attrgetter('name')
)
def test_self_referential_symmetrical(self):
tony = PersonSelfRefM2M.objects.create(name='Tony')
chris = PersonSelfRefM2M.objects.create(name='Chris')
SymmetricalFriendship.objects.create(
first=tony, second=chris, date_friended=date.today(),
)
self.assertSequenceEqual(tony.sym_friends.all(), [chris])
# Manually created symmetrical m2m relation doesn't add mirror entry
# automatically.
self.assertSequenceEqual(chris.sym_friends.all(), [])
SymmetricalFriendship.objects.create(
first=chris, second=tony, date_friended=date.today()
)
self.assertSequenceEqual(chris.sym_friends.all(), [tony])
def test_add_on_symmetrical_m2m_with_intermediate_model(self):
tony = PersonSelfRefM2M.objects.create(name='Tony')
chris = PersonSelfRefM2M.objects.create(name='Chris')
date_friended = date(2017, 1, 3)
tony.sym_friends.add(chris, through_defaults={'date_friended': date_friended})
self.assertSequenceEqual(tony.sym_friends.all(), [chris])
self.assertSequenceEqual(chris.sym_friends.all(), [tony])
friendship = tony.symmetricalfriendship_set.get()
self.assertEqual(friendship.date_friended, date_friended)
def test_set_on_symmetrical_m2m_with_intermediate_model(self):
tony = PersonSelfRefM2M.objects.create(name='Tony')
chris = PersonSelfRefM2M.objects.create(name='Chris')
anne = PersonSelfRefM2M.objects.create(name='Anne')
kate = PersonSelfRefM2M.objects.create(name='Kate')
date_friended_add = date(2013, 1, 5)
date_friended_set = date.today()
tony.sym_friends.add(
anne, chris,
through_defaults={'date_friended': date_friended_add},
)
tony.sym_friends.set(
[anne, kate],
through_defaults={'date_friended': date_friended_set},
)
self.assertSequenceEqual(tony.sym_friends.all(), [anne, kate])
self.assertSequenceEqual(anne.sym_friends.all(), [tony])
self.assertSequenceEqual(kate.sym_friends.all(), [tony])
self.assertEqual(
kate.symmetricalfriendship_set.get().date_friended,
date_friended_set,
)
# Date is preserved.
self.assertEqual(
anne.symmetricalfriendship_set.get().date_friended,
date_friended_add,
)
# Recreate relationship.
tony.sym_friends.set(
[anne],
clear=True,
through_defaults={'date_friended': date_friended_set},
)
self.assertSequenceEqual(tony.sym_friends.all(), [anne])
self.assertSequenceEqual(anne.sym_friends.all(), [tony])
self.assertEqual(
anne.symmetricalfriendship_set.get().date_friended,
date_friended_set,
)
class M2mThroughToFieldsTests(TestCase):
@classmethod