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[1.5.x] Fixed #18823 -- Ensured m2m.clear() works when using through+to_field 

There was a potential data-loss issue involved -- when clearing
instance's m2m assignments it was possible some other instance's
m2m data was deleted instead.

This commit also improved None handling for to_field cases.

Backpatch of 611c4d6f1c
This commit is contained in:
Anssi Kääriäinen 2012-10-28 16:47:07 +02:00
parent 13b4d44860
commit f105fbe52b
3 changed files with 128 additions and 15 deletions
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45
django/db/models/fields/related.py
View File

@ -573,9 +573,31 @@ def create_many_related_manager(superclass, rel):
self.reverse = reverse
self.through = through
self.prefetch_cache_name = prefetch_cache_name
self._pk_val = self.instance.pk
if self._pk_val is None:
raise ValueError("%r instance needs to have a primary key value before a many-to-many relationship can be used." % instance.__class__.__name__)
self._fk_val = self._get_fk_val(instance, source_field_name)
if self._fk_val is None:
raise ValueError('"%r" needs to have a value for field "%s" before '
'this many-to-many relationship can be used.' %
(instance, source_field_name))
# Even if this relation is not to pk, we require still pk value.
# The wish is that the instance has been already saved to DB,
# although having a pk value isn't a guarantee of that.
if instance.pk is None:
raise ValueError("%r instance needs to have a primary key value before "
"a many-to-many relationship can be used." %
instance.__class__.__name__)
def _get_fk_val(self, obj, field_name):
"""
Returns the correct value for this relationship's foreign key. This
might be something else than pk value when to_field is used.
"""
fk = self.through._meta.get_field(field_name)
if fk.rel.field_name and fk.rel.field_name != fk.rel.to._meta.pk.attname:
attname = fk.rel.get_related_field().get_attname()
return fk.get_prep_lookup('exact', getattr(obj, attname))
else:
return obj.pk
def get_query_set(self):
try:
@ -677,7 +699,11 @@ def create_many_related_manager(superclass, rel):
if not router.allow_relation(obj, self.instance):
raise ValueError('Cannot add "%r": instance is on database "%s", value is on database "%s"' %
(obj, self.instance._state.db, obj._state.db))
new_ids.add(obj.pk)
fk_val = self._get_fk_val(obj, target_field_name)
if fk_val is None:
raise ValueError('Cannot add "%r": the value for field "%s" is None' %
(obj, target_field_name))
new_ids.add(self._get_fk_val(obj, target_field_name))
elif isinstance(obj, Model):
raise TypeError("'%s' instance expected, got %r" % (self.model._meta.object_name, obj))
else:
@ -685,7 +711,7 @@ def create_many_related_manager(superclass, rel):
db = router.db_for_write(self.through, instance=self.instance)
vals = self.through._default_manager.using(db).values_list(target_field_name, flat=True)
vals = vals.filter(**{
source_field_name: self._pk_val,
source_field_name: self._fk_val,
'%s__in' % target_field_name: new_ids,
})
new_ids = new_ids - set(vals)
@ -699,11 +725,12 @@ def create_many_related_manager(superclass, rel):
# Add the ones that aren't there already
self.through._default_manager.using(db).bulk_create([
self.through(**{
'%s_id' % source_field_name: self._pk_val,
'%s_id' % source_field_name: self._fk_val,
'%s_id' % target_field_name: obj_id,
})
for obj_id in new_ids
])
if self.reverse or source_field_name == self.source_field_name:
# Don't send the signal when we are inserting the
# duplicate data row for symmetrical reverse entries.
@ -722,7 +749,7 @@ def create_many_related_manager(superclass, rel):
old_ids = set()
for obj in objs:
if isinstance(obj, self.model):
old_ids.add(obj.pk)
old_ids.add(self._get_fk_val(obj, target_field_name))
else:
old_ids.add(obj)
# Work out what DB we're operating on
@ -736,7 +763,7 @@ def create_many_related_manager(superclass, rel):
model=self.model, pk_set=old_ids, using=db)
# Remove the specified objects from the join table
self.through._default_manager.using(db).filter(**{
source_field_name: self._pk_val,
source_field_name: self._fk_val,
'%s__in' % target_field_name: old_ids
}).delete()
if self.reverse or source_field_name == self.source_field_name:
@ -756,7 +783,7 @@ def create_many_related_manager(superclass, rel):
instance=self.instance, reverse=self.reverse,
model=self.model, pk_set=None, using=db)
self.through._default_manager.using(db).filter(**{
source_field_name: self._pk_val
source_field_name: self._fk_val
}).delete()
if self.reverse or source_field_name == self.source_field_name:
# Don't send the signal when we are clearing the

8
tests/regressiontests/m2m_through_regress/models.py
View File

@ -62,18 +62,18 @@ class B(models.Model):
# Using to_field on the through model
@python_2_unicode_compatible
class Car(models.Model):
make = models.CharField(max_length=20, unique=True)
make = models.CharField(max_length=20, unique=True, null=True)
drivers = models.ManyToManyField('Driver', through='CarDriver')
def __str__(self):
return self.make
return "%s" % self.make
@python_2_unicode_compatible
class Driver(models.Model):
name = models.CharField(max_length=20, unique=True)
name = models.CharField(max_length=20, unique=True, null=True)
def __str__(self):
return self.name
return "%s" % self.name
@python_2_unicode_compatible
class CarDriver(models.Model):

86
tests/regressiontests/m2m_through_regress/tests.py
View File

@ -123,6 +123,14 @@ class ToFieldThroughTests(TestCase):
self.car = Car.objects.create(make="Toyota")
self.driver = Driver.objects.create(name="Ryan Briscoe")
CarDriver.objects.create(car=self.car, driver=self.driver)
# We are testing if wrong objects get deleted due to using wrong
# field value in m2m queries. So, it is essential that the pk
# numberings do not match.
# Create one intentionally unused driver to mix up the autonumbering
self.unused_driver = Driver.objects.create(name="Barney Gumble")
# And two intentionally unused cars.
self.unused_car1 = Car.objects.create(make="Trabant")
self.unused_car2 = Car.objects.create(make="Wartburg")
def test_to_field(self):
self.assertQuerysetEqual(
@ -136,6 +144,84 @@ class ToFieldThroughTests(TestCase):
["<Car: Toyota>"]
)
def test_to_field_clear_reverse(self):
self.driver.car_set.clear()
self.assertQuerysetEqual(
self.driver.car_set.all(),[])
def test_to_field_clear(self):
self.car.drivers.clear()
self.assertQuerysetEqual(
self.car.drivers.all(),[])
# Low level tests for _add_items and _remove_items. We test these methods
# because .add/.remove aren't available for m2m fields with through, but
# through is the only way to set to_field currently. We do want to make
# sure these methods are ready if the ability to use .add or .remove with
# to_field relations is added some day.
def test_add(self):
self.assertQuerysetEqual(
self.car.drivers.all(),
["<Driver: Ryan Briscoe>"]
)
# Yikes - barney is going to drive...
self.car.drivers._add_items('car', 'driver', self.unused_driver)
self.assertQuerysetEqual(
self.car.drivers.all(),
["<Driver: Ryan Briscoe>", "<Driver: Barney Gumble>"]
)
def test_add_null(self):
nullcar = Car.objects.create(make=None)
with self.assertRaises(ValueError):
nullcar.drivers._add_items('car', 'driver', self.unused_driver)
def test_add_related_null(self):
nulldriver = Driver.objects.create(name=None)
with self.assertRaises(ValueError):
self.car.drivers._add_items('car', 'driver', nulldriver)
def test_add_reverse(self):
car2 = Car.objects.create(make="Honda")
self.assertQuerysetEqual(
self.driver.car_set.all(),
["<Car: Toyota>"]
)
self.driver.car_set._add_items('driver', 'car', car2)
self.assertQuerysetEqual(
self.driver.car_set.all(),
["<Car: Toyota>", "<Car: Honda>"]
)
def test_add_null_reverse(self):
nullcar = Car.objects.create(make=None)
with self.assertRaises(ValueError):
self.driver.car_set._add_items('driver', 'car', nullcar)
def test_add_null_reverse_related(self):
nulldriver = Driver.objects.create(name=None)
with self.assertRaises(ValueError):
nulldriver.car_set._add_items('driver', 'car', self.car)
def test_remove(self):
self.assertQuerysetEqual(
self.car.drivers.all(),
["<Driver: Ryan Briscoe>"]
)
self.car.drivers._remove_items('car', 'driver', self.driver)
self.assertQuerysetEqual(
self.car.drivers.all(),[])
def test_remove_reverse(self):
self.assertQuerysetEqual(
self.driver.car_set.all(),
["<Car: Toyota>"]
)
self.driver.car_set._remove_items('driver', 'car', self.car)
self.assertQuerysetEqual(
self.driver.car_set.all(),[])
class ThroughLoadDataTestCase(TestCase):
fixtures = ["m2m_through"]