SessionBase.cycle_key() discards session data if _session_cache isn't populated

[InvalidInterrupt]

The cycle_key() method will use an empty dict for session data if it had not previously been loaded. The docstring says the function is there specifically to avoid losing sesison data, and the behavior feels inconsistent. This won't be noticed on most sites, as the AuthenticationMiddleware accesses the session on every request. However, it did cause problems for me in unittests for some views.

[Tim Graham]

Could you please give an example test that demonstrates the issue?

[InvalidInterrupt]

The first commit in ​https://github.com/InvalidInterrupt/django/tree/ticket_28066 modifies an existing check for this situation to fail if data is lost. I also went ahead and quickly wrote a patch for the issue. I'll submit a pull request if you also believe this is a bug.

[Tim Graham]

Looks okay at first glance. The previous change (887f3d3219b9f8192d27314eceee27ab1f89c5cc) was new in 1.11 so this could be backported.

[InvalidInterrupt]

​PR

[Tim Graham <timograham@…>]

In dda596c:

Fixed #28066 -- Prevented SessionBase.cycle_key() from discarding data.

[Tim Graham <timograham@…>]

In 5d556d2a:

[1.11.x] Fixed #28066 -- Prevented SessionBase.cycle_key() from discarding data.

Backport of dda596ca3296f5b2574cf4876a4e176594f52834 from master

[GitHub <noreply@…>]

In 81f84494:

Refs #28066 -- Fixed nondeterministic ordering test failure in sessions_tests.

Thanks Tim Graham for the review.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 3173d9a:

[1.11.x] Refs #28066 -- Fixed nondeterministic ordering test failure in sessions_tests.

Thanks Tim Graham for the review.

Backport of 81f844940279140d27578fc6a5b134763ffcceb6 from master

[Tim Graham <timograham@…>]

In d6524088:

[1.11.x] Refs #28066 -- Fixed Python 2 failures in sessions_tests.