SessionStore nonexistent key example is outdated

[jmcbailey]

The documentation at ​https://docs.djangoproject.com/en/1.8/topics/http/sessions/#using-sessions-out-of-views has the following example:

from django.contrib.sessions.backends.db import SessionStore
s = SessionStore(session_key='no-such-session-here')
s.save()
s.session_key
'ff882814010ccbc3c870523934fee5a2'

However, when I run this with Django 1.8.12, s.session_key actually returns None.

The reason is that when the SessionStore instance is saved (with must_create=False, i.e. the default), it results in a call to self.load(), which looks for an existing Session object with the given session_key. This of course does not yet exist, so the session_key gets set to None - see ​https://github.com/django/django/blob/1.8.12/django/contrib/sessions/backends/db.py#L29

I don't know if this change in behaviour was intentional or not, but I didn't see any mention of it in the 1.7 or 1.8 release notes, and of course the fact that the behaviour is different to what's documented suggests it was not intentional. (I haven't checked the file's history, but it definitely did work as documented in Django 1.6.)

In any case it's a pretty minor issue, only affecting one unit test of mine, and was very easy to work around.

[Tim Graham]

The behavior changed in this security fix: 66d12d1ababa8f062857ee5eb43276493720bf16 and again in 3389c5ea229884a1943873fe7e7ffc2800cefc22 where the snippet now raises UpdateError.

I'm not sure if the example is demonstrating anything useful now. Maybe it could simply be removed?

[Berker Peksag]

I agree that the example can be removed. I've opened a PR: ​https://github.com/django/django/pull/6676

[Tim Graham <timograham@…>]

In 698c8df:

Fixed #26503 -- Removed an outdated example from session docs.

[Tim Graham <timograham@…>]

In ccea4a4:

[1.10.x] Fixed #26503 -- Removed an outdated example from session docs.

Backport of 698c8dfc2a5c5865a8bb163c1ae70b75d53e6415 from master

[Tim Graham <timograham@…>]

In 4dc1bf89:

[1.9.x] Fixed #26503 -- Removed an outdated example from session docs.

Backport of 698c8dfc2a5c5865a8bb163c1ae70b75d53e6415 from master

[Tim Graham <timograham@…>]

In 42958488:

[1.8.x] Fixed #26503 -- Removed an outdated example from session docs.

Backport of 698c8dfc2a5c5865a8bb163c1ae70b75d53e6415 from master