Error in formatting HttpResponseRedirect when __init__() raises DisallowedHost

[Jerome Leclanche]

When initializing an HttpResponseRedirect with a redirect url that does not match the allowed_schemes attribute, the DisallowedRedirect exception is raised before super(HttpResponseRedirectBase, self).__init__(*args, **kwargs) is called, which sets self._headers.

This causes repr()ing/printing the response to error out with AttributeError: 'HttpResponseRedirect' object has no attribute '_headers'.

Ref: django/http/response.py (HttpResponseRedirectBase)

[Tim Graham]

Could you provide a complete snippet or a test for Django's test suite that demonstrates the problem?

[Jerome Leclanche]

Example screenshot

[Jerome Leclanche]

The easiest way to reproduce it is to initialize HttpResponseRedirect("invalid-scheme://foo") from a django view and look at the resulting debug variables. It's a trivial error as it *should* only appear when catching the exception and debugging it.

[Tim Graham]

Thanks. HttpResponseBase aliases __str__ = serialize_headers. A solution could be to define a complete __str__ that uses the value of super() if self._headers isn't set. I'm not sure it's worth it. Is the formatting error more than a minor cosmetic problem?

[Jerome Leclanche]

In 95% of cases it's just a cosmetic issue on the django debug page, but I suspect it might actually obscure other bugs, especially if someone is using Sentry or a similar exception catcher.

Is there a reason why the exception is raised before super()? It seems incorrect to do so at first glance.

[Tim Graham]

I think it would be fine.

[Babatunde Akinyanmi]

Replying to Tim Graham:

I think it would be fine.

Do you mean it would be fine to call super before raising the exception?

[Tim Graham]

Yes.

[Jerome Leclanche]

​https://github.com/django/django/pull/7708

[Tim Graham <timograham@…>]

In a849ec18:

Fixed #27606 -- Fixed HttpResponseRedirect.repr() crash when DisallowedRedirect is raised.