m2m_changed pk_set value inconsistent between post_add and post_remove
|Reported by:||anentropic||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||1.5|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
the docs say:
"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."
What I found is that for action=='post_add':
- first time add(x) -> set([x])
- next time (same x) add(x) -> set()
but for action=='post_remove':
- first time remove(x) -> set([x])
- next time (same x) remove(x) -> set([x])
I feel like they should be consistent. Either way is fine but the behaviour of post_add seems more useful to me (can avoid unnecessary action in your signal receiver)... but it should be documented that you get empty set if nothing needed adding.
I've only tried on 1.5 so far but looking at source I don't see any new code to change this behaviour https://github.com/django/django/blob/master/django/db/models/fields/related.py#L1032
Whereas it looks like the add method has code to deliberately exclude already added items https://github.com/django/django/blob/master/django/db/models/fields/related.py#L1008
I'm happy to make a patch if it's felt this is useful?
Change History (2)
comment:1 Changed 16 months ago by anentropic
- Needs documentation unset
- Needs tests unset
- Patch needs improvement unset
- Summary changed from Documentation clarification: m2m_changed pk_set inconsistent between post_add and post_remove to m2m_changed pk_set value inconsistent between post_add and post_remove