In `DEBUG`, when an `Http404` is encountered it is re-routed to the 404
handler, which renders using `TECHNICAL_404_TEMPLATE`, and an opportunity
arises to provide hints about what code was causing the error, much like I
asked for in #22756 (if there's a theme to my tickets, it's that I value
debugging simplicity), which puts the view causing the 404 into the
result. By suggesting instantiating 404s with messages, we can help users
help themselves further.
Given this view:
{{{
def myview(request, obj_id):
obj = get_object_or_404(MyModel, pk=obj_id)
if not mymodel.published:
Http404("Unpublished")
if not mymodel.is_accessible_via(request.method):
Http404("Not via this method")
if not mymodel.allows_user(request.user):
Http404("Not found for this user")
# ...
}}}
It is easy to see which 404 was thrown in the technical debug view because
`force_bytes` is called on the exception (which inherits `__str__` from
`Exception`) and the `reason` is rendered as the error message if no
`urlpatterns` were tried.
Without instantiating (`raise Http404` vs `raise Http404('message')`) it
becomes a debugging guessing game as to which condition threw the
exception (ignoring the merit of the above conditions, which are total
garbage)
I'm suggesting that the places in the documentation where bare, un-
instantiated Http404s are raised is updated to reflect this idea, which is
already used in places like `get_object_or_404` anyway.
--
Ticket URL: <https://code.djangoproject.com/ticket/24143>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
* needs_better_patch: => 0
* has_patch: 0 => 1
* needs_tests: => 0
* needs_docs: => 0
Comment:
Pull request is https://github.com/django/django/pull/3907
--
Ticket URL: <https://code.djangoproject.com/ticket/24143#comment:1>
* needs_better_patch: 0 => 1
* stage: Unreviewed => Accepted
Comment:
As I mentioned on the PR, I think this ticket's rationale could be added
to the docs as well.
--
Ticket URL: <https://code.djangoproject.com/ticket/24143#comment:2>
* needs_better_patch: 1 => 0
* stage: Accepted => Ready for checkin
Comment:
[https://github.com/django/django/pull/3907 PR #3907] LGTM.
--
Ticket URL: <https://code.djangoproject.com/ticket/24143#comment:3>
* status: new => closed
* resolution: => fixed
Comment:
In [changeset:"726a9550db5129badc1c44809b0bed728fa1ad90"]:
{{{
#!CommitTicketReference repository=""
revision="726a9550db5129badc1c44809b0bed728fa1ad90"
Fixed #24143 -- Encouraged use of Http404 messages for debugging.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/24143#comment:4>
Comment (by Tim Graham <timograham@…>):
In [changeset:"bd08cfca6ff04e7cec940f5b59e97cdcceddcc69"]:
{{{
#!CommitTicketReference repository=""
revision="bd08cfca6ff04e7cec940f5b59e97cdcceddcc69"
[1.7.x] Fixed #24143 -- Encouraged use of Http404 messages for debugging.
Backport of 726a9550db5129badc1c44809b0bed728fa1ad90 from master
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/24143#comment:5>