#27462: Attribute "pk_set" is always is not empty, even m2m is not changed at
all.
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Reporter: Seti | Owner: nobody
Type: Uncategorized | Status: new
Component: Documentation | Version: 1.10
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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A code of signal;
{{{
@receiver(m2m_changed, sender=Group.user_set.through)
def changed_m2m(sender, instance, action, reverse, model, pk_set,
**kwargs):
print('Signal "{}" | Users in group: {} | pk_set: {}'.format(action,
instance.user_set.all(), pk_set))
}}}
Run code:
{{{
g1 = Group.objects.all()[0]
g1.user_set.add(UserModel.objects.all()[0])
g1.user_set.add(UserModel.objects.all()[0])
g1.user_set.add(UserModel.objects.all()[0])
g1.user_set.remove(UserModel.objects.all()[0])
g1.user_set.remove(UserModel.objects.all()[0])
g1.user_set.remove(UserModel.objects.all()[0])
}}}
Results:
{{{
Signal "pre_add" | Users in group: <QuerySet []> | pk_set: {UUID
('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "post_add" | Users in group: <QuerySet [<User: Martin Rivera>]> |
pk_set: {UUID('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "pre_add" | Users in group: <QuerySet [<User: Martin Rivera>]> |
pk_set: set()
Signal "post_add" | Users in group: <QuerySet [<User: Martin Rivera>]> |
pk_set: set()
Signal "pre_add" | Users in group: <QuerySet [<User: Martin Rivera>]> |
pk_set: set()
Signal "post_add" | Users in group: <QuerySet [<User: Martin Rivera>]> |
pk_set: set()
Signal "pre_remove" | Users in group: <QuerySet [<User: Martin Rivera>]> |
pk_set: {UUID('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "post_remove" | Users in group: <QuerySet []> | pk_set: {UUID
('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "pre_remove" | Users in group: <QuerySet []> | pk_set: {UUID
('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "post_remove" | Users in group: <QuerySet []> | pk_set: {UUID
('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "pre_remove" | Users in group: <QuerySet []> | pk_set: {UUID
('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
Signal "post_remove" | Users in group: <QuerySet []> | pk_set: {UUID
('d0d4a1eb-d2c0-4a27-b9a6-a057a4fa25bc')}
}}}
If action == 'pre_remove', then pk_set has primary keys of objects which
is not presets in a queryset of other model. It is an expected behaviour.
But if action == 'post_remove' then pk_set **always** contains primary
keys of objects, even queryset is empty. Does is expected behaviour?
The Django`s docs says next:
https://docs.djangoproject.com/en/1.10/ref/signals/#m2m-changed
''pk_set
For the pre_add, post_add, pre_remove and post_remove actions, this is a
set of primary key values that have been added to or removed from the
relation.''
So, why the pk_set for the action == 'post_remove' always not empty?
I tested it on the Django 1.10 and the 1.9, the result is same.
--
Ticket URL: <https://code.djangoproject.com/ticket/27462>
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