CacheMiddleware should respect max-age

[Chris Beaven]

This came up in IRC today, someone (K0001) wanted to use the per-site middleware but disable caching for a specific view. It seems like the django.views.decorators.cache.never_cache decorator should work but it wasn't.

The reason is because currently the cache middleware doesn't bother looking to see if an expiry age was set by the response, it just uses the CACHE_MIDDLEWARE_SECONDS setting.

[Chris Beaven]

For example (assuming you have the middleware turned on):

from django.views.decorators.cache import never_cache, cache_control

def test_cache(request):
    from datetime import datetime
    from django.http import HttpResponse
    return HttpResponse(str(datetime.now()))

cached_view = test_cache
no_cache_view = never_cache(test_cache)
short_cache_view = cache_control(max_age=5)(test_cache)

When/if this is committed it should probably be noted on BackwardsIncompatibleChanges that the per-site cache logic has changed.

[Simon G]

oops, that was me.

[Malcolm Tredinnick]

(In [6736]) Fixed #5813 -- Taught the CacheMiddleware to respect any max-age HTTP header
when setting the expiry time. Thanks, SmileyChris.