As documented, the id() function can return the same value for distinct
objects with non-overlapping lifetimes which can result in signals being
sent to the wrong receivers if two distinct senders happen to have a
colliding id() value.
Since reproduction of the issue requires memory constrained
circumstances where the same exact id() is reused for two senders of the
same signal the test opt to simulate the collision by systematically
making the same id for Sender instances.
Note that we explicitly avoid keeping a strong reference to senders that
cannot be weakly referenced as that would unexpectedly prevent them from
being garbage collected. This means that id(sender) collisions could
still occur for such objects but Django itself doesn't make use of them.
Thanks Sjoerd Job Postmus for the reduced test case and Mariusz for the
review.
Co-authored-by: And Clover <and@doxdesk.com>
