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Changes between Initial Version and Version 1 of Ticket #34733

Ticket #34733
- Property Owner changed from nobody to Leif Kjos
- Property Status new → assigned

initial	v1
3	3	This poses a problem if the signal is supposed to run validation on the final state of the model. For example, let's say I have a model called `Customer` with a many-to-many relation to `SubscriptionPlan` and I have a `m2m_changed` signal that is supposed to validate if their SubscriptionPlan is valid.
4	4
5		If I call `subscription_plans.set([some_plans])`, the many-to-many manager will first call `subscription_plans.remove()` then `.add()` inside an atomic transaction. If my signal validates on the first `remove()`, it could be in an invalid state, even though it won't be by the time the `.add()` completes.
	5	If I call `Customer.subscription_plans.set([some_plans])`, the many-to-many manager will first call `subscription_plans.remove()` then `.add()` inside an atomic transaction. If my signal validates on the first `.remove()`, it could be in an invalid state, even though it won't be by the time the `.add()` completes. However, I still need to be able to validate on the signal if the standard `.remove()` method is called.
6	6
7	7	To get around this, I had to create a custom ManyToManyField with a custom RelatedManager that set an instance variable on the model when the `.set()` method was called. I'd like to propose adding a feature to the RelatedManager or to the signals to make the `m2m_changed` signal aware of if the `.set()` method was called when running. This could be a private attribute on the instance or extra information passed to the signal receiver.