cache_page decorator doesn't work with HttpResponses whose content is an iterator

[Erik Allik]

To reproduce:

@cache_page(60*15)
def foo(request):
    return HttpResponse(i for i in ('resp', 'onse'))

Responds with emptiness. Outcomment @cache_page(60*15) or replace i for i in ('resp', 'onse') with 'response' and it's fine.

The documentation for HttpResponse is clear about this: "content can be an iterator or a string."

[Russell Keith-Magee]

I wasn't even aware that the docs ever claimed that a HttpResponse *could* be an iterator.

[Carl Meyer]

They certainly do: ​http://docs.djangoproject.com/en/dev/ref/request-response/#passing-iterators

Perhaps at the least there ought to be a note there that this doesn't work with caching?

[Erik Allik]

The docs are very clear about this: "Finally, you can pass HttpResponse an iterator rather than passing it hard-coded strings."

[James Bennett]

The example you've given is a generator; so far as I'm aware we've never supported those in responses.

[Alex Gaynor]

A generator is an iterator. If we want to say we support some iterators, but not all, that really needs to be explicitly documented (and it's going to confuse the hell out of people: myself included).

[Russell Keith-Magee]

This isn't something that should be fixed in documentation. We need to work out why a generator doesn't cache properly - or why the caching process doesn't result in rolling out the generator.

[Russell Keith-Magee]

#12214 is related to this problem.

[Aymeric Augustin]

This is an exact duplicate of #6527.

The problem is that cache_page will drain the iterator, leaving it empty for the actual rendering step.