build strategy is not working with reverse relations

[ranelpadon]

Description

We have interesting use case recently, and that is, to render a PDF preview without hitting the db. We realized that we could use the build strategy which creates instances, but not saving them in db.

Model / Factory code

# models.py
class Order:
    ...

class Ticket:
    ticket = models.ForeignKey(Order, related_name='tickets')


# factories.py
class OrderFactory:

    @factory.post_generation
    def tickets(self, create, extracted, **kwargs):
        TicketFactory.build(order=self)
        print(self.tickets.all())  # returns []

class TicketFactory:
    ...

Observed behaviors:

order = OrderFactory.build()
ticket = TicketFactory.build(order=order)
print(ticket.order)  # works ok
print(order.tickets.all())  # returns []
print(ticket.order.tickets.all())  # returns []

ticket = TicketFactory.build()
print(ticket.order)  # works ok
print(ticket.order.tickets.all())  # returns []

Expected behavior:

• order.tickets should be non-empty.

Is it working as intended? Is there a workaround so that the reverse relations will be linked properly? Removing the post_generation hook has no effect also. And they work as intended when using the default create strategy, so issue is only in build strategy. Thanks a lot.